147193392-operative2011-2012-1

OPERATIVE Amal

All Class III lesions should b€ filled with composite resin,because they are esthetically important,

. Both the statement and the reason are correct and related

. Both the statement and the reason are correct but NOT related

. The staternent is correct, but the reason is NOT

. The statement is NOT correct, but the reason is correct

. NLITHFR the sratemenr NOR rhe reason is correcr

'|

Cop!riglr c 20ll-l0l I - Denhl Dccks

*** Think closely, distolingual Class III lesions are relatively nonesthetic and Nartional Board questions consider the best material whether it be amalgam or direct gold.

Composite resin is not recommended for Class III lesions on the distal-lingual aspect ofcanines /rse either amalgam or direct gold). Composite material will not maintain themesiodistal dimension ofthe looth. Note: This may not be entirely true today due to thefact that there are much better wear resistant resins than in the past, however, for Na-tional Board questions composite is not recommended for this situation.

A lingual approach is made when preparing a Class III dental amalgam preparation for thedistal ofa canine because a lingual approach preserves the esthetic value ofthe facial sur-

face.

Remember:

. A bite-wing radiograph is the best method to diagnose incipient carious lesions onthe distal surface ofcanine teeth.. A diagnostic aid to be used as a last resort to confirm the presence ofa carious lesionon the proximal surface of an anterior tooth is mechanical separation (usually w,ith aweage).

Rule ofthumb: When two teeth adjacent to each other have Class III lesions, you shouldprepare the larger one lirst and fill the smaller one first. Access to the preps and shadematching are easier when you do both at the same appointment.

The iderl tmount of dentin required between anamalgam restoration rnd the pulp for insulation is:

.0.5 mm

.l.0mm

. 2.0 mm

. 3.0 mm

Coplrighr O 2011,2012, D€nral Decks

' A prtlent comes in claiming that th€ir holistic doctor told hlm that h€ has rn '

allergy to mercury and needs only white fillings. Your best response is:

. There is no such thing as a mercury allergy; plus, there is no mercury in amalgamfillings

. You might have mercury allergy, but that is very rare. Plus, there is no mercury inamrloam fi llinoc

. There is no such thing as a mercury allergy; plus, with proper isolation and techniqueyour exposure will be minirnal

. You might have a mercury allergy, but that is very rare. Plus, with proper isolation andtechnique your exposure will be minimal

Copright O 201 l-2012 - Dental Decks

**x Amalgam is a poor thermal insulator; this is why a base ofeither calcium hydrox-ide or zinc oxide eugenol is placed under most amalgam restorations 60plovide thermalnrolectiotl).

Comparison of Restorative Msteri!ls

Chancteristic Direct Gold Amrlgem Composite

Close adaptation to cavjty walls Vcry good Good Cood

Coeflicient ofthermal exDansion similar to tooth structure Verv good Cood

Chemicallv acceDtable to hard and softtissues Very good Cood

Absence ofinitation to gingival Very good Good

High edge strenglh Very good

Non-corroding in oral fluids Very good Fair N/A

Insolubiliry in oral fluids Ixcel]cnt Excellent Cood

Clinical loflge\'ify Verv good Good Fair

High abmsron resisrance Cood Cood Fair

Permanently.estores M-D dimension Cood Very good Fair

\\'irh sla nds masticatory forces F-air Cood

\jersatility in use Iair Cood

Imltates natural tooth color Fair Poor very good

Ease ofmanipulation and placemert Good Very good

Tlermal and electrical insulator Very good Cood

Thc amount of mercury rcmaining in a set amalgam rcstoration is rclated to how much ofthc rnercury-rich matdx is lel-i in thc amalgam after condcnsation. The key is to minimizethe amount of matrix which forms during the reaction. By condensing the amalgamnri\turc in the cavity preparation, the mercury-rich matrix will comc to the surface and bcr!'mo\ cd bv subscqucnt condensing and carving. The final amalgam restoration will be.Lrnrposed of mostly residual alloy and vcry little ofthe mercury-rich matrix.

TlIc amount ofmercury remaining in dental amalgam after condensation directly affects:i 1 t th,-. porosity ofthe restoration (2) thc compressive strength ofthc rcstoration (3) the cor-rt sir,-- rcsistancc ofthc rcstoration and (4) tbe surfacc finish ofthc rcstoration.

\Iercurr is used to initiate the reaction ryith the alloy. Although an amalgam restorationi: non-toric. mercury is poisonous. Free mercury, in thc form of vapor or liquid droplets.r.prcscnts a significant health hazard in the dcntal office. The greatest potential hazard ofchronic nrcrcury toxicity comes from inhalation ofmcrcury vapor. The vaporization is mostlrkell to occur during condensation ofthe amalgam (alu,ct1.s use high speed suction).\ote: Nlercury hypersensitivity (allergl') isvery rare (l irt 100 million).

Important point concerning corldensation pressure: The area ofthe condenser point andthc forcc cxcrtcd on it by thc opcrator govcrn the condensation pressurc. The smaller thecondenser point. thc greater is thc pressure exerted on the amalgam. By doubling the di-ameter of the condenser point and doubling the hand pressure applied to the instrument,the operator actually exens lcss condensation pressure.

You would prefer your assistant overtriturate the amalgamrrther than undertriturate it, this is because an overtriturated

amalgarn will still haye optimal strength.

. The first statement is true; the second statement is false

. The first statement is false; the second statement is true

. Both stalements are true

. Both statements are false

Co$n-shr < :0ll l0ll - Denral Decks

All ofthe followings are similarities between amalgamClass II restorations and inlay Class II restorttions

EXCEPT one, Which one is the EXCEPTIOM

. Occlusal isthmus width

. Depth into dentin

. Axio-pulpal line angle shape

. Gingival wall form

CoP)righr O 201l'2012 - Denral Decls

Iotei'

The longer the trituration time, the smaller the setting expansion. Ifthe trituration is car-ried to the extent that the amalgam appears shiny and wet. the strength will be maximaland the smooth, can'ed surface will retain its Iuster long after polishing. A properly tdtu-rated amalgam appears shiny, wet, smooth and homogenous.

Inadequate trituration results in an amalgam mix that has a low strength and a rough sur-face that will accelerate corrosion. An undertriturated amalgam mixture will appear dryand grainy. Condensing this mixture will result in poor adaptation to the walls of thepreparation, lacrimation between condensed increments, and reduced strength.

Remember: An overtriturated nix is preferable to an undertriturat€d mix.

L The discolored, conoded, superficial layer frequently seen on the surface ofa dental amalgam restoration is most likely a sulfide.2. When carving an amalgam restoration, be sure to trim the margins with a

sharp instrument that rests on tooth structure /t/rr.r r.i/1 prevent " ditching" theIwrgurs).3. lfan amalgarr "chips" when you are carving it, the reason for this is that theamalgam was condensed after its working tirre had elapsed.

*** The gingival n.rargin should clear the contact area to allow lor adequate finishing ofthe enamel marsins and olacement ofa matrix band.

l/J intcrcuspal (max) 1/3 intercuspal (max)

Inclitration of wells with respectto the occlusal surface

Buccal and lingual walls convergeapproximately parallcl to theextemal surface

Form a reverse bevel at th€ axialgingival line angle, into the

gingivalr,vall

Class V amalgam restorNtions rar€ly require retentivegfooves, but if they are used, they are placed at the

lncisoaxial and gingivoaxial line angles.

. The first statement is true; the second stalement is false


. Both slalements are true


Copyrighr C 2011,2012, Denral Decks

. Insufficient tdh.[ation and condensation

. High residual mercury

. The contamination ofthe amalgam by moisture during trituration and condensation

. The failure to use a cavity vamish

7

Cop,righr O 201 l'2012 - Dental Decks

Delayed expanslon of amalgam restorations isassociated with which two factors?

*** Class V amalgam restorations commonly require and utilize retention grooves.

The r€tention form for a Class V amalgar.n preparation is provided by the gingival re-tention groove placed along the gingivoaxial Iine angle and the incisal retention grooveplaced along the incisoaxial line angle.

The outline form for the classical Class V amalgam preparation is a deformed trapezoid(sometimescollecl'kidney-shaped").Theoutlineformisdeterminedbythelocationandsize ofthe carious area.

The non-parallel mesial and distal walls ofthe preparation are straight and parallel to,but never extending beyond, the transitional line angles. The direction olthese walls is

determined by the direction ofthe enamel walls (as is the decay pattern).

The occlusal and gingival walls ofthe preparation should be gently curved arcs as deter-rrlined by the contour ofth€ free margin ofthe gingival tissue. Note: These arcs shouldbe as parallel to each other as possible.

lmportant points:L The occlusal arc will normally be the longer of the two.i. The gingival margin will normally be at, or slightly below, the rrargin ofthe free gin-sir a.

-l. For incipient lesions, the axial wall should be uniformly deep into dentin.

1** Important: Thc contaminalion ofthe amalgam by moisture during tdturation and condcnsation js

unquestlonably the principal cause of failures.

limorsture is incorporatcd into an alloy that contains zinc, thc watcr reacts with the zjnc to produce hy-drogcn gas. The resulting pressure from the liberated gas produces severe expansion ofthe amalgam. This

results rn the follorving clinical manifestations:. lhc amalgam protrudes from the cavity preparation. PosI operative parn. Erccssivc corrosion

Important points to remcmbcr rcgarding amalgam:

L The compressive sftength js greatly reduced when amalgam is contaminated with moisture. The

comp.essr!e strength ofhigh-coppcr amalgam is similar to tooth structure.LThc most imponant problem for amalgam restorations is that they have different co€fficients ofthermaf erpansion/contr^ction (amalgam: 25 ppnr/"C) compared to tooth structure (10 ppm/'C).During reductions in intraoral temperatllre. there is a strong tendency at thc margins for amalgam

rcsroralions to contract away from the margins and allow marginal leakage ol intraoral fluids (petro1dhir, that arc latcr expelled when the temperature retums to non-nal.i. Thc tensile strength ofamalgam is about one-fifth to one-eighth ofits compressive strcngth. thatis \\ht enamel is needed to support amalgam at the margins ofrestomtions. Nole: It is more abrasion-

resistant than composite resin or unfilled resin..1. Amalgam is brittle and has a low edge strength.5. Amalgam is a high thermal conductor.6. High-copper amalgams exhibit no clinically relevant crccp or flow7. You need a minimum thickness of0.75 fin axial areds) to |.5-2 mm (in areas ofocclusal conldct)lbr adequate cornpressivc strength.

Proper cond€ns|tion ind carving makes an amalgam restorationstronger because it removes th€ mercury-rich matrix.

. Both the statement and the reason are correct ard related


. The statement is correct, but the reason is NOT

. The statement is NOT corect, but the reason is corect

. NEITHER the statement NOR the reason is correct

Coplright e 20ll-2012 - Dental Decks

t Which phase of the amrlgam re&ction is prone

to corrosio, in clinic{l r€storations?

. Gamma

. Garrma-one

. Gamma-fwo

. Gamma-three

9CopFghtO 20ll-2012 - Dental Decls

The most important consideration in the strength ofthe amalgam is the mercury content.lfthe mercury content exceeds 5570, a dramatic loss in strength results. Amalgam restora-tions that contain mercury levels ofabout 55% exhibit a high incidence ofmarginal break-down, fracture, corrosion, and the surface finish olthe restoration is not good.

Factors which influence the final m€rcury content of a restoration:. Original mercury-alloy ratio: specific to each product but generally less than 1 :1 so

that amalgam contains 43% to 50% mercury. Amount of trituration. Condensation pressure and time involved in carrying out condensation

Very important: Removing the mercury-rich matrix by proper condensation and carv-ing produces a stronger and more corrosion-resistant amalgam because it minimizes theforration of the matrix phases of ar.nalgam, which are the least desirable parts of the set

matenal.

Silrcr-tin alloy + Mercury -),\g:Sn Hg

(gamma)

Silvcr-tin alloy + Silver-mcrcury + Tin-mercuryAglSn Ag:Hg: SngHg

(gamma) (gamma-one) (gamma-two)

Camma is the unreacted alloy. lt is the strongest and corrodes the least. l'onrs 307n ofvolume ofsct anialsan. Gamma-one is thc matrix lbr unrcactcd alloy and is thc sccond strongesl phasc. ItFrrnni 609'0 ofvolume ofset a)nalgam. Gamma-two is thc wcakcst and softest phase. It is also themost susceptible to corrosion in the mouth and fonns l0olu ofthe volume ofthe sct amalgam. Ther olunre of lhe Ganrma-two phase decreases with tirne due to corrosion.

Thc kcy drttcrcncc bctwcen the low coppcr and thc high copper amalganls is thal thc low copperamalgarns contain the gamma-two phase, which is not present in the high copper amalgams. lnstead,the high copper anralgams contain the Cu6Sn5 phase. Since the gamma-two phasc conodcs t'aster

rhan the Cu,,Sn5 phase. thc gamma-two phasc containing low copper amalgams develop micro-porositics duc to corrosion fastcr than thc high coppcr amalgams. Thesc porcsities wcaken theanralcam rnarcins and explain why rnarginal delbcts (chipped riargllr) are more oftcn seen aroundlo* copper amalgans. This explains why high-copper amalgams should be used rather than the low-cerpper amalgams.

l. Smaller particle size results in higher strength, lower tlow, and bctter car'"ability.

\ot*s 2 Spherical amalgams high in copper usually have the bcst tcnsilc and con'rprcssivc

charactcristics."" 3. Copper contents over 6yo ("high-copper" alloy,i/ climinate the gamma-two phase

by forming a copper-tin fCr6SrJ-, phase resulting in superior propcrties.,1. Amalgam has a coellicient ofthcrmal cxpansion approrimately tuice that ofloolhstructure.

5.The tensile strength ofamalgam is about one-fifth to one-eighth ofits compressive

strcngth.

The reaction that occLrrs between the allov Darticles and thc mcrcurv can be sunrmarized as lollows:

When preparing a class Il amalgam restoratlon, all surface anglesshould be approximately 90 degrees.



. Both statements are true


10

CopyriShr O 201l-2012, Dental Decks

Beveling the gingival cavosurface mrrgin of the proximal boxofa Class II amalgam preparation on a permanent tooth:

. Should result in a long bevel

. Is contraindicated because ofthe low edge strength of amalgam

. Should remove unsupported enamel which may fracture

. Is unnecessary since the tooth structure in this area is strong

11

CopFight C 201 I -20 12 - De'tal Deck

General propenies of Class lI amalgam preparations:

. All walls should meet the surlace of the tooth at a 90'angle (butt joint).

. Occlusal dovetail; provides resistance to proximal displacement.

. Pulpal floor should be flat same as Class l.

. The buccal and lingual walls ofthe proximal section should converge occlusally the ex-tension ofthese walls is determined primarily by the position ofthe adjacent teeth in rela-tion to the tooth being restored.. The buccal, lingual, and gingival walls should be extended into the embrasures enoughto allow easy cleaning - areas of lessened caries susceptibility.. The axiopulpal line angle is beveled to reduce concentration of stresses resistancefonn.. Retention grooves are placed in the axiobuccal and axiolingual line angles and extend-ed to the height ofthe axial wall - resistance to dislodgement.. Lingually, it is often necessary to create a reverse cuNe in the outline. A revelse curveis a cun'e put into the buccal or lingual wall so the wall meets the extemal surface of thetooth at a 90" angle.

\ote: Class ll amalgam preps have independent retention and resistance form fbr both theproximal box and occlusal portion ofthe prcparation.

Important: When caries is extensive, reduction ofone or more ofthe cusps for capping rnaybe indicated. When the facial (or lingtnl) extension is two-thirds from the primar) groove to-rvard the cusp tip, reduction ofthe cusp(s) for amalgam capping is mandatory fbr the devel-

opn]ent ofadequate resistance form. Note: The final restomtion has to have restored cusps witha minimal thickness of2 mm of amalgam for functional cusps and l 5 mm of amalgam fornonfunctional cusps.

""* The gingival cavosurface margin is bevered onry ifit is in the enamer. Beveling is notnecessary if the gingival margin is within cementum.

The,singir.,al cavosurface margin should be beveled to remove any unsupported enamel.The ber el is usually placed with a gingival margin trimmer. This gingival margin must bebe1o* an'existing contact with the adjacent tooth in order to alori pioper finishing ofthe-rrnerlal margin.

L The bevel is no steeper than necessary to ensure lullJength enamel rods fonn_\oa€ ing the gingival margin and is no wider than the enamel.2. Remember: Enamel rods in the gingival third ofthe primary teeth extendocclusally from the DEJ, eliminating the need in Class il preparations for thegingival bevel that is required in permanent teetlt.3. Primary morar teeth have marked cervicar constriction. Thererore. whenpreparing the proximal portion ofa Class II cavity prep, a satisfactory gingivalseat may be difficult to obtain if the prep extends too deeply gingivally.

Which tooth requires special attention when preparingthe occlusal aspect for a restoration?

. Mandibular first bicuspid

. Mandibular second bicuspid

. Maxillary first molar

. Maxillary first bicuspid

12

Coprighr O 201 1,2012 - Denral D€cks

a



. The statement is conect, but the reason is NOT



13

Cop)right O 201l-2012 - Denial Decks

r All four wa[s ofa Class I amalgam preparation should diverge slighflybecause divetgence prevents undermining ofthe marginal ridges.

The key to this question is the angulation ofthe preparation. The bur should be tilted lin-gually to prevent encroachment on the facial pulp horn and also to maintain dentinalsupport ofthe lingual cusp. The pulpal floor should be parallel to the occlusal plane ofthetooth faciolinsuallv.

\ote: Pulpal floor slopes to coincide with the slope (height) of the c\sps.Remember: The area olthe tooth that is most sensitive durins cavitv nreparation is DEJ.

Important:. Only nvo walls of a Class I amalgam preparation should diverge, the mesial and dis-tal. Thc. reason is still true because there are only two marginal ridges per tooth, mesialand distal

XDIVERGING

(Correct)CONVERGING

(Incorrect)

*** This slight occlusal divergence prevents undermining the marginal ridges of theirdentin support.

, 1. This divergence of the mesial and distal walls holds true for Class I prepa-

t\i..otci'. rations for direct filling gold and gold inlays as well..,.;:,:,,;,:, 2. For premolars the distance from the margin of the mesial and distal wall to

the proximal surface must not be less than 1.6 mm. For molars this minimaldistance is 2 mm.

The matrix band should be removed after condensation ofthe amalgam, butprior to the linal carving ofthe restor|tion. This is because the wedge

compensstes for the thickness ofthe matrix band.

. Both the statement ard the reason are correct and related



. The statement is NOT correct, but the reason is corect

. NEITHER the statement NOR the reason is conect

14

Cop) iehr O 201 1,2012 - Dental Decks

The diagonal slot opening on the Tomemire matrix ret ner (also called theUnivercal matrix systeml is always placed facing the gingiva. This:

. Permits easy separation ofthe retainer from the band in an occlusal direction

. Allows for better contour ofband to tooth

. Allou's for easier wedge placement

. Is less harmful on the gingiva

15

Coplright O 20ll-2012 - Dental Decks

Although the wcdge is uscd to cornpensatc for the thickncss ofthe mat x band. the true reason forcarving after the rcmoval ofthe band is to gain proper access to all margins ofthe amalgam rcstora-tion.

lmportant points to remember regarding matrix bands:. The reason lbr placing thc matrix for a Class II amalgam restoration to p.olrude abovc the cav-ily preparation is to allorv for overfilling, thus enhancing adcquate cavosurface coverage.. Contact arcas are always carefully restorcd in all restorations in order to protect thc gingivaltissuc. Thc matrix band should be bumishcd into contact with adjaccnt tceth, this will help as-SUre contact.. One of thc most difficult teeth to adapt thc matrix band to is the mesial of a maxillary firstpremolar, due to its devefopmental dcpression (co cavity in the cervical thir-d ofthe mesiol sur,fute oflrc o ortr).

lmportant: The wedging action betwcen the teeth should providc enough separation to compen-sate for the thickness ofthe matrix band. This will cnsure a positive contact relationship after thcnratrix is rcmovcd following thc condensation and initial carving oflhe anralgam.

Corrrrnon problems associated with amalgam restorations:. Postoperative sensitivitl ;

- \1ay be causcd by inadcquatc condensation, or lack ofpropcr dcntinai sealing. \Iarginal voids:

- \1ay be caused by inadequate condcnsation. or amalgarn breaking away from margins whencan ing

.llarginal ridge fractures: may bc causcd by any ofthe following:- Not rounding the axiopulpal iine angle in Class Il tooth preparations

' \laryinal ridge lcl't too high- Inrpropcr occlusal cn'rbrasurc fomr- hnproper removal ofmatrix band- Or erzealous carving ofthe restoration

In addition. tlte larger circumference ofthe matrix band is alu,ays placed toward the oc-clusal surlace ofthe tooth. This acconnnodates for the larger tooth circumference at thecontact level.

The primary function ofthe matrix band is to restore anatomical contours and contactareas. Other functions include providing a rigid wall to condense filling material against,pre\ enling excess filling material from going subgingivally, and to some extent, limitingmoisture contamination during condensation. A properly placed wedge will also protectthe sinsiral tissue and help reduce moisture leakage into the cavity preparation.

\\ edses are inserted fron the facial or lingual embrasure, whichever is largeq slightly gin-gival to the gingival margin. The wedging action between the teeth should provide enoughseparation to compensate for the thickness ofthe matrix band.

Important: When placing a matrix band for a Class II amalgam restoration, the gingivo-occlusal \r'idth ofthe band should be trimmed to be at least I mm qreater than the ex-pected marginal ridge height.

All ofthe following are true statements regarding the polishingof amalgam .EXCEPI one. Which one is the EXCEPTION?

. It reduces marginal discrepancies

. It should be done about l0 minutes after placement

. It prevents tamishing of the restoration

. It improves the appearance oflhe restoration

. It should be done with a wet polishing powder

16

Coprigh€r 20ll-2012 - Dental Dects

All of the following are true concernlng a Class V amalgam

r preparztion EXCEPT one. Which one is the EXCEPTIOM

. The outline form is determined primarily by the location ofthe free gingival margin

. The mesial, distal, gingival and incisal walls of the cavity preparation diverge outward

. The retention form is provided by the gingival retention groove along the gingivoaxialline angle and an incisal retention groove along the incisoaxial line angle

. A cervical clamp is usually necessary to retract gingival tissues

17

Cop),right C 20ll-2012 - D€ntal Decks

The final finish of the amalgam restoration should not be done until after the amalgamis fully set. It should be delayed for at least 24 hours after condensation and preferablylonger (21-48 hours). By waiting you can be assured that the reactions between the alloyand mercury will have been completed and a more corrosion-resistant surface will be cre-ated.

Amalgam restorations should be tlnished and polished fbr tlrree major reasons: (1) to re-duce marginal discrepancies and to create a more hygienic restoration. (2) to reduce mar-ginal breakdown which will reduce the chance of recurrent decay, and (3) to preventtarnishing and to improve the appearance ofthe restoration.

Heat generation must be avoided. The use of dry polishing porvders and discs can

easily raise the surface temperature above the 6VC (14ff F) danger point. Thus, a wetabrasive powder in a paste form is the agent ofchoice. Not€: I{eat will not only damage

rhe pulp but also draws mercury to the surlace ofthe restoration and an inferior restora-tion rvill result.

Flnai polishing may be accomplished using a rubber cup with flour of pumice followedb1 a high-luster agent, such as tin oxide.

Remember: When checking the occlusion on a newly condensed amalgam restoratton,

rhe marks left by the articulating paper should be of the same intensity as other markingsin the same quadrant.

*** This is false; the outline lbrm is determined primarily by the location and size ofthecarious lesion.

l. Care must be taken to distinguish the active root surface carious lesion from\otes the root-sudace lesion that was active but has become inactive (arrested).The

anested lesion shows ebumated dentin (sclerotic dentin) lhat has darkened fromextrinsic staining and is firm to the touch of an explorer.2. Thc Class V an.ralgam restoration is used to restore lesions from caries, ero-sion and abrasion.3. Care should be taken not to "ditch" the cementum when finishing and pol-ishing.,1. Occasionally you will notice that the gingival tissue has receded apicallyfrom the gingival margin ofa Class V restoration that was previously polished.This may be related to ineversible tissue changes caused by inadvertently trau-matizing the tissue when the restoration was being polished.Key point: Be careful.

Remember: Incipient carious lesions are contained entirely within enamel and have notspread to the underlying dentin. The two options for treatment are:

l. Promote remineralization: with fluoride vamish and self-administered fluoride.followed by regular monitoring. Note: Incipient carious lesions usually do not progress

rapidly.2. Place a restoration: be as conservative as nossible.

. Increased trituration time will increase compressive strength and decrease settingexpanslon

. A decrease in particle size will decrease compressive strength and increase settingexpanslon

. Increased condensation pressure will increase compressive strength and decrease settingexDansron

18

Coplaight O 201 l-2012 - Detrtal Decks

Amalgam restorations require an obtuse cavosurfacemargin because amalgam b a brittle material.






19

Coplrjghr O 20ll-2012 - Dental Deck!

*** The opposite is true.

Dimensional change

Setting Expansion:- Most amalgam restorations show slight setting expansion, but not ofclinical sig-nificance.- The more free mercury, the more setting expansion (and vice versa).

. The greater the time oftrituration, the less the expansion

. The greater the pressure used in condensation, the less the expansion

. The smaller the particle size, the less the expansion

Strength:

- Amalgam is brittle, but possesses good compressive strength. The most impor-tant consideration in the strength of the amalgam is the mercury content. Mercurycontent above 550% will cause a marked decrease in stren stb. khould be within 45-5 3?6 b1'u,eight).

. Higher condensation pressure increases strength

. The smaller the pafiicle, the more strength

. The longer the trituration time, the more strength

. The fewer voids, the more strength

Remember for the boards: (when this is the answer)

A. The statement is NOT correctB. Therefore, the reason is obviously not relatedC. So, you need to evaluate the reason independently

thus: . Amalgam restorations require a 90o cavosurface margin. An.ralgam is a brittle material

Clinical experience has established that this butt joint margin ofenamel and amalgam isthe strongest. Amalgam is a brittle rnaterial with low edge strength and tends to chip underocclusal stress ifits angle at the margins is less than 80" to 90'.

90 degre€s with the exlemal surface

Outer planes carried into cleansableatea (prcvides access lor fnishinsmdlg'rt. Bcvcled to result in 40degree marginal metal

90 degr€€ angle with extemal ludace

90 degee angle with extemal surface

New amalgam alloys are t€rmed "hlgh copper."

The higher 7o of copper reduces marginal breakdown.





20Coptriglr @ 2011,2012, Denial Dects

Creep is a process that happens over time, and graduallyincreases the matginal integrity of an amalgam restoration.





21

Cop),right () 2011,20t? - Dertat Decks

Constituents in Amalgam:

Basic constituents:. Silver (Ag) (40-70'/,)

- tncreases strength- lflcreases expanslon

. Tin (Sn) 25-270/. Note: Influences the amalgam in an

- dccreases expansion opposite manner to silver.- decreased strength-incrcascs sctting time

. Copper /C , 6% or less: Note: New alloys called "high copper" conrain 9-- ties up tin: rcducing gamma-2 fbnnation 30% copper. These alloys have less marginal break-- incrcascs strength dorvn and are lcss likcly to corrode.- reduces tamish irnd corrosion- rcducc. crccl: rcdrrccs marginal deterromtron

. Nlercury d18l 3% max.:- activates reaction- only pure metalthat is liquid

Other constitu€nts:. Zi.c (Zn) l9i, or less: used in manufacturing. decreases oxidation of other elements (sacrificial

- Prolides better clinical perfomance: less marginal breakdown- Causes delayed expansion with low Cu alloys ifcontaminated with moisture during condensation. Palladium 1Pl/ l96 or lcss: rcduced corosion, greater luster. Itrdium (ln) lrzo or less:

- decreases surfacc tcnsion

- spherical allo]s. requrre less mercury

- smalier surface area easier to wet- -10 Io,15% Hg

- admixed alloys. require more mercury

- lathe-cut particles more difficult to wet- 45 ro 50% Hg

- rcduces creep and marginal brcakdown. reduces amount ofmercrlry necessary - increases strength. reduces emitted mercury vapor - must be used in admixed alloys

Creep (ti re-dependent deJbrmation or strqin relaxation) is the deformation with time inresponse to a constant stress. It has been implicated as one of the main causes for mar-ginal fracture of amalgam restorations.

L The higher the creepJ the greater the degree ofmarginal deterioration.\otes 2. Creep is time-dependent.

High copper and low mercury content of an amalgam restoration will tend to decreasecreep..{ltering the trituration time and condensation pressure can change the creep rateLri an amalgam restoration:

. Both undertrituration and overtrituration tend to increase the creep rate

. If there is a delay between trituration and condensation, the creep rate incr€ases

. Increasing the condensation pressure decreas€s the creep rate (this u,ill al.so decreasetlte littal nrercur,- <:onte t of'the restoration)

The marginal leakage ofan amalgam restoration decreases as the restoration ages. Cor-rosion products are helpiul in reducing marginal leakage around amalgam restorations.These corrosion products, such as tin oxide and tin sulfide, accumulate in the gap betrveenthe restoration and the tooth, thus providing an excellent seal.


. Both the statement ard the reason are correct but NOT related

. The statement is correctt but the reason is NOT



22

Coplright C 20ll-2012 - Dental Deks

All ofthe following are true about glass ionomer cementsEXCEPT one.Which one is the EXCZ'PIIOM

. Release fluoride

. Good chemical adhesion

. Good biocompatibility

. Good thermal insulator

. Thermal expansion similar to tooth

. High solubility after initial setting

23

Cop)righr @ 20ll'2012 - Denral Decks

*** There is no free mercury in tdtumted amalgam because trituration coats the alloy parti-cles with mercury.

The object oftrituration is to bring about an amalgamation ofthe mercury and alloy. Each in-dividual alloy particle is coated with a slight film ofoxide that prevents penetmtion by the mer-cury. During trituration this film is rubbed offand the clean metal is then readily attacked bythe mercury

Silver Allovs for Dental Amalgams:Low copper alloys :4 to 6010 or less, traditional alloy

. Comminuted {irregular Jiliug, or ldthe-cut)

. Spherical particles

High copper alloys: 9-30%o most conmon. corrosive resistant

. Spherical: sets faster and attains final mechanical properties more rapidly

. Comminuted can haye zinc or be zinc free and also can be fine cut ur microcut

. Combination (admix) mixture of spherical and comminuted particles

Dispersed phase allov was the original admix alloy, mixture of comminuted traditional sil-r er alloy and spherical particles of silver-copper eutectic alloy. Most commonly used alloytoda1.

Eutectic alloy is an alloy in which the elements are completely soluble in liquid solution butseparate into distinct areas upon solidification.

\ote: Once amalgamation occurs, no free (unreacted) mercury is associated with the amalgamrestomrion. The restoration has no toxic properties. However, if the amalgam is heated be-

) ond 80'C, liquid mercury can fom on the surface ofthe amalgam and its vapor presents ahealth hazard.

*** This is false; glass ionomer cements have low solubility, lower than zinc phosphates

t\\'hi(h ore loter thon zinc poll'c(u'fisrytlqlse).

Glass ionomer cements are hybrids ofsilicate and polycarboxylate cements designed tocombine the fluoride releasing properties of silicate particles with the chemically ad-hesile and more biocompatible characteristics ofthe polyacrylic acid matrix comparedto the extremely acidic matrix ofsilicate cement.

Advantageous physical properties of glass ionomer cements:. Release of fluoride: anticariogenic. Chemical adhesion to the prepared tooth and certain metals. Micromechanicalbond to composite resins. Important: Chelation of calcium ions on tooth structureby ionized polyacrylic acid side-groups is the principal mechanism of chemical ad-hesion to tooth structure.. Biocompatibility is high, thus with enough dentin remaining (0.5- I rrr) no pulpalprotective agent (colcium hydrotide) is required. Good thermal insulators: equal to that ofnatural dentin. Thermal expansion is similar to that oftooth structure. Aft€r initial setting, they have low solubility in the morith

Note: Its disadvantage as a cement is that it has a higher cement film thickn€ss than zincphosphate cements.

R€member: No lab test ofcement has correlated solubility with clinical retention.





21Coptrighr () 20l l-2012, Denlal Decks

ZOE cements make good ternporary sedativerestorations b€cruse their pH is very basic.






25Cop)righr O 201 I 2012 - Dental Decks

Glass ionomer ccmcnts arc mixcd powdcr-liquid componcnt systcms. Thc polvdcr is a fluoro alumino-silicrte glass

that .cacts with a liquid u,hich is polyacrylic acid to tbrm a ccmcnr ofglass particlcs sunoundcd by a matrix of tlu-oridc clcments.

Luaing agcnts /{{ rrerrrl:. Zinc phosphate cement: onc ofthc oldcsl and nrosl widcly uscd ccmcnts, zinc phosphalc ccmcnt is lhc stan-dard against which ncw ccmcnls arc mcasurcd. Advantages: Iong record ofclinical acccpiabilily, high comprcs-sivc strcnglh, acccptably fiin film thickncss. Disadvantagcsr lo\r initial pH lvhrch ml]y lcad to postccmcntalionscnsitivily, lack ofan abilily 10 bond chcmically to toolh structurc and lack ofan anticariogcnic cUcct. Important:Zjnc phosphatc cemcnl is mixcd using thc "frozen slabrr lcchnique rlhich grcatl,v cxrcnds thc working timc abr'

$nuchas300%). Note:ThcpHofncwlymixcdzincphosphatecsmcnlisundcr2/.'foldr.rtol\dnishm slbc applied i or.ler to proled thc pulp) brl iscs lo 5.9 $ithin 2,1hours aDd is rcarly n!'utralat 48 hours.Thc filmthickrcss ofzinc phospharc is abour 25Im.. Zinc pollcarboxylate cement: also known as zinc polyacrylatc ccnrcnt. r,as one ofthe first chemicalh adhe-siye dcnlal malcrials. Thc adhcsivc bond is primarily 1o cnamclallhough u wcakcrbond to dcntin also fonns. Thisis duc 1o thc fact that bondrng appcars to bc thc rcsult ofa chclation reaction bctwccn thc carboxyl groups oftheccmcnt and caicium

'n thc loolh slructurc;hcncc,lhc morc highly mincralizcd rhc tooth slructrrc, the slrongerthc

bond. ,\dy.ntagcs: kind to thc pulp. chcmically bonds to tooth stnrcturc. Disadvantages shon lvorkinS tinrc, re-quircs scparatc looih conditioning stcp priorto cemcntation. Note: It is morc viscous whcn mixcd and has r shortcr$orking lirnc than docs zinc phosphale ccment.

. Glass ionomer cement: Advantages: chcmical bond to cnamcl and dcniin, anticariogcnic cllccr(rctea\es llu-r/ /.Ll. cocfiicient oflhcrnlal cxpansion sinrilar to thal oflooth structurc. high comprcssivc strcngth, low solubil-iI!. Disadrantrges lo$ inilial pH which may lcad to postcemcntation scnsili\ity. scnsilivity lo both moislurcconlrmination and dcsiccation. Note: 1ts mcchanical propcnics arc supcrior to zinc phosphatc and polycarboxy-

' R!sin-modified glass ionomer luting agents: havc propcrtics sinrilar to glass ionomcr ccmcnls, bul havc higherrtrenglh end lo*er solubilit). Note: Thcy should not bc used with all-ccramic resloralions ducs to rcporls ofcc-.3rnic iiacturc. nrost likcly Ihc rcsult ofexpansion liom walcr absorplion.

. Resin luting agcnts: arc unfillcd rcsins that bond to dcntin, which is achicvcd \rith organophosphatcs, l2-,tr.lrotterht l nu'rhacn'late IHE]|{AI/, or,1-mcthacryloyloxycthyl rrimcllitatc anhydridc (4-llE rA).,\d\antages: higb comprcssivc strcngth. low solubility. Disadrantages: irrilaling cffccls on thc pulp. high lilnrhickncss a. lJ !rr. Note: As a gene.al rulc, resin cements arc thc bcst choicc fbr luling ceramrc restoratrons.

*** ZOE cen.rents make good temporary sedative restorations because their pH is about

Zinc oxide-eugenol cement is a soft, sedative - type cement. It is used as a sedatiYe or tem-porar\'filling material, as an insulative base, and in interim caries treatment. The pow-

der is zinc oride and the liquid is eugenol. Eugenol has a palliative eff€ct upon the dental

pulp. and this is one of the main advantages ofusing this type ofcement.

-\ con|entional mixture ofzinc oxide and eugenol is relatively weak. In recent years "re-intorced" or "irnproved" zinc oxide-eugenol cements have been introduced (called rain-

Iorced ZOE or ZOE-EBA).ln reinforced ZOE (4,pe I ZOE) the powder is composed

of zinc oxide and finely divided polymer particles (poll,nethyl-metlncD'late) in the

arrount of 20 to 40% by weight. In addition, the zinc oxide powder is surfac€ treatedbr an aliphatic monocarboxylic acid. such as propionic acid. Note: This combination ofsLrriace treatment and polymer reinforcement results in a material that has good strength

and toughness rvhich markedly improves abrasion resistance. Reinforced ZOE is fine forbasing large and complex cavities. This material is able to withstand the pressure of amal-

sam condensation and it has minimal effect on the pulp.

Contraindications to the use ofZOE include:

l. On dentin or enamel prior to bonding: compromises bonding.

2. As a base or liner for composite resins: eugenol interferes with polymerization.

3. Patients rvho are allergic to eugenol (or oil oJ cloves): this is somewhat common.

4. Direct pulp capping: eugenol is a pulpal irritant when in dir€ct pulpal contact.

Remember: ZOE is soluble in oral fluids and is difficult to remove from cavity prepa-

ratlons.

BILIC

IRNI (Intermediate Restorative Maleia, will int€rfere withsubsequent placement ofa resin filling, This is because IRM

is a form of Zinc Oxide Eugenol,


. Both the staternent and the reason are correct but NOT related


. The statement is NOT correct, but the reason is conect


OPERATI\rE BIL/C

Zinc phosphate cement can cause irreversible pulpaldamage because it shrinks slightly upon setting.





. NEITHER the statement NOR the reason is comect

Coprright O 20ll-2012 - Dental Decks

Zinc oxide-eugenol cement is a low-strength base used as a temporary cement filling inthe event that the patient will return at a later date for a semi-pennanent restoration. Thepowder is mainly zinc oxide and the liquid is eugenol with olive oil as a plasticizer ZincOxide and Eugenol (ZOE) is not very durable, and it wears away afterjust a few weeks,but it works to relieve pain, calm the nerve and protect the tooth. Note: During the Viet-nam War, the US Army invented a more durable form of ZOE called IntermediateRestoratiye Matetial (lRM) which is fortified with plastic powder.

Uses:. As an intermediate restorative material lor both Class I and II restorations.. As a base under non-resin restorations. Restomtion oldecidr"rous teeth lwlan pennanent teeth arc tv,o .veat1s or less.fiom erup-tton ). Restorative emergencies

-tr dvantages:. Hi-sh strength comparable to zinc phosphate. Excellent abrasion resistance. Good sealing properties. Lo\\' solubility

Important: Because of its zinc-oxide eugenol composition, IRM rvill interfere rvith sub-

sequent placement ofa resin filling.

lmportant: The initial nixture ofthis cement is very acidic (pH oJ 3.5) ancl can causeirrerersible pulpal damage ifa cavity varnish (2 coits) is not;lac;d on rhe tooth priorto cementation ofthe crown.

\ote: Zinc phosphate cements shrink more when they are in contact with air; thus, the.'ement should not be alJowed to dry our.

zinc phosphate cement is the oldest ofthe luting cements and thus is the one that has theLrrnsest "track record" and serves as the standard to which newer systems can be com_pared. It is a powderJiquid system; the powder is mostly zinc oxide 1al.ro con ,\ists o/.mag_,:esrrrnt oxide in the approxinate ratio o-l'9 to /) and the liquid is orthophosphoric acid.The primary use ofzinc phosphate cement is as a luting agent for the cementation ofcastreltorations. It can also be usetl as a base material wtin a f]igtr compressive strength isneeded.

It ha-s superior strength compared to other cements, and its retention ls dependent uponIn.":luni:ul interfocking (as opposetl to glass ionomer antl polycdyfiolylqte c,ements'.rhiclt edhere to tooth structure by- virtue of rhe polvat.rylic acid ii the liquid).

l.Zinc phosphate cement riquid that has lost some of its water content wi\otes, cause the sctting time ofthe mix to be lengthened.

pressivc strength ofthc cement.

Zinc phosphate cements should be rnixed on a cool glass slab, addinga srnall amount of powder to the llquid every 20 seconds. This is done

in order to gain atl of the foltowing advantages .EXCXPI one.Which one is the EXCEPZOM

. Stronger final set

. Lower solubility

. Greater viscosity

2A

Cop).right C 20ll-2012 Dental Deks

. Glass ionomer is often the ideal material of choice for restorins root surface caries inpatients with high caries activity

. The best surface finish for a glass ionomer restoralion is that obtained against a sur-face matrix

. Glass ionomer adheres to mineralized tooth tissue

. Glass ionomers are somewhat esthetic and polish much better than composites

29

CopFiShr O 201 l'2012 - D€ntal Decks

All ofthe following statements are true regarding glass ionomerrestorations TXCEP? one. Which one is the EXCEPTIOI'ft

*** This is a disadvantage; it will create a material with lower viscosity and thus allow-ing it to flow throughout the metal crown.

Mixing procedure for zinc phosphate cements:

. A cool mixing slab should be usedx* Caution: The temperature of the slab should not be below the dew point of theroom.. Mixing should be started with the addition of a small amount of powder to the liq-uid. This procedure, along with the cool slab, increases the working time.. Small increments of powder are added approximately every 20 seconds with vigor-ous mixing until a creamy consistency is achieved. This will promote a high powderliquid ratio and a superior cementation medium by providing the following:

- a lower viscosity ofthe mix- a stronger final set- a lower solubility ofthe set cement

*** Important point: The advantages of using the cool slab method are a sub-stantial increase in the working time of the mix on the slab and a shorter settingtime of the mix after olacement in the mouth.

*** It is tru€ that glass ionomers are somewhat esthetic. however, they do not polish as

u ell as composites.

Both self-cured and light-cured versions ofglass ionomers are available. Light-cured glass

ronomers are preferred because of both the extended working tirne and their improvedphvsical properties. Because of their limited strength and wear resistance, glass

ionomers are indicated generally for the restoration of low stress ar€as where caries ac-

rilin potential is ofsignificant concern.

Compared to composites, glass ionomers:. Har e a lower compressive strength, tensile strength, and hardness. .\re generally very technique sensitive because of their high solubility when firstmrred

\ote: \\iith the newer hybrid or light-cured resin-modified glass ionomers, the aboveproperties have treen improved.

Glass ionomers are generally considered the nearly ideal base/liner material because ofthe tbllorving properties:

. Adhesive bond to tooth structure

. Snap set in the light-cured form (br example, Vitrebond)

. Anticariogenic: due to fluoride release

. Bond to composite: makes for excellent liners for Class V root caries restorations.

*** Sometimes called the "sandwich technique". This technique achieves all the ben-efits ofthe glass ionomer cements plus the high polishability, surface hardness, andstrong bond to enamel ofthe composite resin.

Which of the following mlterials could be used tocement o bridge and lill a cervlcal lesion?

. Glass Ionomer

. Zinc oxide-eugenol

. Zinc polycarboxylate

. Zinc phosphate

30

CopyriShr O 201 I'2012 - Denral Decks


. The first slatement is false; the second statement is true



31

Coptrighr O 20ll-2012, DmtalDecks

*** Only glass ionomer is uscd as a ceme (lutitry agent) and a pennanent rcstoralivc nratcrial.Glass ionomcr ccmcnts are ollen used for root surface carious lesions bccause ofthe potenlial ad-

vantagc of tluonde release in helping to control the spread ofcarics.Alier lhc sctting, expansion due to water uptakc has bccn obscrvcd lbr some of thc ncwcr rcsin-modified glass ionorrcr cemenls (Fuji Duet, l/ilremer and Adt ancel compated to a regular resin(BIS-GMA or uretfutne actllale) cemcnt such as Panavia 21, which is a self--cure resin cenlenl,conventional glass ionomcr luting ccmcnts, and thc old standby zinc phosphatc cemenl. Tradilionalglass ionomcq phosphate. and resin cemcnts all undergo contraction during sctting. The BIS-GMAor urethane acrylate resin cements all undergo polymerization shrinkagc during setting. Horvever.

the presence ofglass fillcr in somc resin cement materials reduces the shrinkage and can imparl ra-diopacity. Many ofthc resin cements arc now supplicd in the form ofdual curc systems (pholo-ifii'

tiatetl as vell as telliary- amine peroxide rca(:tiotl). Such matcrials include Adherence, Choice.Duolink. Enforcc. [-ute-it. Nexus. Opal, Rcsinomer, Scotchbond Resin Cement and Variolink.

Remember: It is important to note that fhe main f'unction ol'a luting cement is 10 provide a non-penreable seal at the margins around the restoration. Thc rnarginal cementiilled gaps around in-lals. cro\\'ns and bridgc abutments can rangc from 25 to 15Opm. Research has shown that thc widerrhe cenrenl gap at the nargin, the greater thc ccmcnt loss i'li1.'rirrgl. A rough cement surfacc is an

rd.'al site fbr plaque accumulation. ln such a situation, slow rclcase of fluoridc can be a very dis-

trnct ad\ anlage.

lmportant: In general, glass ionomer cements tend to have the least erosion. and polycarboxylate

.enrents the most. However, solubility, crosion and strength are signiljcantly affccted by the pow-

der liqurd ratio uscd.

\ote: ZOE. rcinforced ZOE, ZOE-EBA, silicate, and zinc silicophosphate ccmcnts are no longcr rou-

iircly uscd to permancntly cement restorations. Zinc photphate cement has been cxtcnsivcly re-

olacr'd b1 polycarboxylate or glass ionomcr cements. These cemcnts are based on ion cross linked

polr acrl lic acid natriccs that have the potcntial to rcact chenically with residual po\\'dcr panicles

.iild the suriace ol tooth struclurc.

Zinc polycarbox"vlate cement was the first system developed rvith a potential for adhe-

sion to tooth structure via chelation. The polycarboxylate cements are powder/liquid sys-

tems. The liquid is an aqueous solution ofpolyacrylic acid and copolymers. The powder

is zinc oride and magnesium oxid€,

Zinc pollcarboaylate cements have a compressive strength slightly lower than that ofzrnc phosphate while the tensile strength is high€r. Its final strength is dependent on the

pos der liquid ratio, with n.rore powder giving greater strength. The strength of the set

material is sufficient for amalgam condensation and its effect on the pulp is mild enough

ro eliminate the need for sublining. Thermal conductivity is low and thus the materialgi\ es sood protection against thermal stimuli applied to metallic restorations.

-\n ad\ antage ofzinc polycarboxylate cement is that it can bond to tooth structure. Thisis attributed to the ability of the carboxylate groups in the polymer molecule to chelateto calcium in the tooth. The most commonly noted disadvantages of polycarboxylate

cen]ent js its marked thickness and short working time. Currently marketed brands in-clude Durelon lJM ESPE).Liy Carbo (GC Amerita),Shofu Polycarboxylate /.t o/ir. and

Trlok Plus (Dentspl.v/Cqulk). The most recent innovation in these cements has been the

development of Durelon Maxicap. an encapsulated version of Durelon. Because it ismixed and expressed lrom a capsule, the traditional difficulties ofshort working time and

excessive thickness are overcome.

Remember: When cementing a cast restoration, always apply cement to both restora-

tion and the tooth.

When uslng a zlnc phosphate cement you place the varnish lirst_ This is because zinc phosphate cements are not biocompatible.






32

Cop).rightO 20ll-2012 - Denial Dects

. Final application thickness

. Degree ofpulpal protection

. Biocompatibility of material

. Degree ofhardness

Copyrighr O 20ll-2012 - Dental Decks

It should be emphasized that the use ofa base in conjunction with amalgam or gold foil does

not alleviate the need for a vamish as an aid in sealing the cavity margins against leakage.

However, the type ofbase govems the respective order ofapplication ofthe vamish and the

base. lf a zinc phosphate cement base is to be used, then the cavity vamish should be ap-plied to the cavity walls prior to placement of the base. On the other hand, if a biocom-patible agent (e.g., a calcittm h.vdroxide, zinc oxide-eugenol, or polvc arboxl'late cenentbase.,l is employed. then these should be placed against the dentin. and the vamish shouldnot be applied until the base material has hardened. Important: lf vamish is added be-fore a biocompatible base it may prohibit positive qualities such as eugenol's soothing ef-fect or polycarboxylate's chelation and adhesion-

Zinc phosphate cements provide good pulpal protection frorr thermal. electrical, andpressure stimuli, but may damage the pulp as a result ofan initial low pH. This, however,

can be ofbenefit as it provides an antibacterial effect which reduces the number ofviablemicroorganisms in the cavity floor and thus decreases pulpal irritation.

Important: Cements used for bases should be mechanically stronger than u'hen used as

Iuting agents and are mixed with the maximum powder content that is possible. A lou'pol der-toJiquid ratio produces a Iow viscosity cement that is needed for luting agents.

\ote: The varnisb will reduce the initial microleakace of an amalsam restoration.

The most important consideration for pulp protection in restorativc techniques is thc thickness ofthe rcmaining dentin.

In gencral. cements that are thickcr than 2 mm are termed bases and as such function to replacelost dentin structure beneath restorations. A base may be used to providc thcnnal protection under

:nctallic restorations. to increasc the resistance to thc forccs of conclcnsation of amalgam, or to

block out undercuts g'hen taking irnpressions for cast restorations.

The only drstinction bctwcen a base, a cen,leni, and a cavity lincr is thcir final application thick-nesS:

L Cements for luting havc a dcsircd linal film thickness ofapproximatcly l5 to 25 microns.L Ca\ itl finers (either solution or suspension litters). Liners arc nratcrials that arc placcd as a

Ihin coating r ir7r,e .? desied./inal /iln thickness ofapproinutely 5 microns) on the surface ofr .a\ itv prcparation. Although they providc a barrier to chemical irritants, thcy are not used for

rh!'nrlal insulation or to add bulk to a cavity preparation. F urthermorc, these matcrials do not

har c sullicient hardncss or strength to be used alone in a dccp cavity.

-i. Bases havc a linaf application thickncss of approiDt.ttelr, l-2 mm (they nnl' be thitker dep-

pcnling on tl1('.t outlt ef dentin lhal ]1as heen desu'o|ed/. Bascs can be considered as restora-

tr\ c substitules lbr thc dcntin that was rcmoved by caries anclror thc cavity prcparation. They act

as a barrier against chcmical irritation, provide thermal insulation, and can resisl the condensa-

rion lorces on a tooth when placing a restoration. Also, the clinician can shape and contour base

rnaterials ailer placemenl into thc cavity preparalion.

Important: A base should not be used unnccessarily.

Remember: Calcium hydroxide is very eileclive in promoting the fbrmation ofsccondary dcntin.

which is an important aid in the repair ofthc pulp.

Note: Thc sclcction of appropriate bascs and liners to restore the axial wall ol'a Class ll restora-

tions is dependent r,rpon the biological eff'ect requircd and thc thickness of th€ remainingdentin.

_ base ls a base that is typically placed over a calciumhydroxide base that has been placed over a pulp exposure.

. Primary base

. Secondary base

. Direct base

. Indirect base

34Coplrighr O 20l l-2012 - Denral Decks

Solution liners should not be pleced under composite restorationsbecNuse composites do not requir€ the pulpal protection.





. N EITHER the statement NOR the reason is correct

Cop]righr O 20ll-2012 - Denlal Decks

Bases are classilied as either primary or secondary:. Primary bases are placed on the dcntin in closc proximity to thc pulp primarily to pro-vide protection from toxic and thermal irrilants. Undcr amalgam and tooth-coloredrestorations, the primary base is usually calcium hydroxide. whereas, under gold restora-tions, the primary base is usually zinc phosphate cement or zinc polycarboxylate cemenl.Glass ionomcrs arc commonly uscd today as wcll.. Thc most common use of a secondary base is thc placcmcnt of zinc phosphate cementovcr a calcium hydroxide base which has been placed over a pulpal cxposve (direcl pulp. ap).

*** Bases in essence serye as a replacement or substitute lor the protective dentin that has

been destroyed by caries an<lor cavity preparation. Important:The thickness ofthcrmal insulationrequired for pulpal protection is 1000-2000 gm ( L000-2.000 mrn).

lVaterials that have been employed as bases (bases are tlpicallt l-2 nnt thick)l

. Zinc phosphatc cement: remember to seal dentinal lubules with varnish prior to application

. Zinc polycarboxyJate cement: provides adhesion

. ZOE

. Glass ionomer cemcnt:providcs lluoridc rclcase and adhesion

. "Hard setting" calcium hydroxidc matcrials: thickcr than rvhcn used as a linerRemember: All of the above are suitable as a base under amalgam restorations, however, lorcomposites, ZOE cannot be used becausc thc cugcnol will inhibit the compositc sctting rcaction.

Important: (l) pulpal sensitivity is causcd prirnarily by lluid l1ow in dentinal tubulcs (2) lluidflo\\ is detected by mcchanoreceplors on the edge ofthe pulp (3) the reduction in tooth sensitivity* ith decreased fluid flow in tubules is rclated to the fourth power ofthc tubulc radius.

*** Solution liners should not bc placcd undcr compositc rcstorations because they will inhibit the

poll merization ofthe resin. Suspcnsion lincrs should be uscd for pulpal protection in this casc.

Ca\ it\ liners are matenals that are placed as thin coatings over exposed dentin. Their ma'n purposc js to

protect thc pulp by crcating a barrier between the dentin and pulpally jrrilating agents i.e., ocids.liom

;::it,tItt or centents. restordlive nalerials, elc../ by sealing thc dentinal tubules.

Ca\ iI liners are usually classified into two main groups:

L Solution Lircr ( LArnish)t thin film; typical thickncss rangc is 2-5 pm (0.002-0.005 mm):. Suspension Liner: relatively thin film; typicalthickness rangc is 20-25 pm (0.020-0.025 mm)

l. Solution liner: thin layer to seal offrubules- \'arnish:

. Organic solvent based: water insoluble

. l-: llm filmi used to line cavity up over cavosufacc margins

. Sets bl ph.vsical rcaction fd,),1,79/ iust like finger nail polishCommercial examples: Copalite. Hydroxyline. Chembat and Tubilitcc

?. Suspension Liner:. \\ater solvent bascd: water soluble. l0-:5 Lrnr fllm; uscd to line only the denhn. Sets b] physical reactton (dt)ing)Commercial examples: Pulpdcnt and Hypooal

Important: Thc above cavity liners are now being substitutcd with the new dentin bonding systems ordentin sealcrs 1'e.g., Gluma or HurriSeal). Thc dcntin bonding systcms and dentin sealers arc classificdas 5olution liners.

l. The alerage lifetime for thc intcgrity of a vamish film is one month.

-- 2. A 509. rubule co\crcgc is produccd by onc thin coating ofvamish. Hence. thc reasonloles varnish.! lhuulJ bc anp'iietl rn ru' rhrn c.ats.':t;;ii:..t 3. Thc chemical composition ofcopalite contains organic resin, chloroform solvcnt, acc-

tone solvent. and alcohol solvent.

. Chemical reaction ofacids and bases

. Chemical reaction involving pollnnerization

. Chemical reaction involving chelation

. Physical reaction of drying

. Physical reaction ofa sol-gel transformation

36

Coplrighr O 201 1,2012 - Dental Decks

When removing caries, which of the following layers of dentin are^aa^^r^,| lt,1-^l lnf^^.^rl n-.1 ]|r^-t^,^ l^ -^1-^^l ]^ L^ - -^.,-ntaffect€d, btrt not infected, and therefore do not need to be removed?

. Turbid dentin

. Infected dentin

. Transparent dentin

. Normal dentin

. Sub-transpaxent dentin

37

Coplright O 201 l-201? - Dental Decks

Dental materials that are designed as pulpal mcdicaments contain caicium hydroxide or eugenol.

Need depends oo extent ofcavity preparationl. Shallow : 0.5 mm into dentin (Rcmaining dentin > 2 mm, not necessary). Moderate: 1.0 mm into dentin (Remaining dentin : 0.5-2 mm, possibly). Deep < 0.5 mm from pulp (Rcmaining dcntin < 0.5 mm, ycs)Objectives for Pulp Medication:. Eliminate acute inflammation (by soothing the nerves). Prevent chronic inflammation (stimulate secondary/reparative dentin)

Managemedt of Acute InflammationEugenol:

. Palliative : mitigates, alleviates, or eases pain

. Obtundcnt: reduces violence or pungency by dulling senses

Delivery:. Relcased from cement liner or ccmcnt basc into dentinal tubules. Short term effect

N{anagement of Chronic Infl ammation:Calcium hydroxide:

Delivery:. Released from susDension liner, cement liner, or cement base. Very basic, dissolves in water, and diffuses to pulp. Accelerates fomation ofreparative or secondary dentin. Method ofaction unknown

Characteristics of Calcium hydroxide, Ca(OH)2, pasres:

. Gcncratcs very alkaline solutions, pH = I1.0

. Aqueous pastes are viscous and do not wet dry dentin well

. Apply without pressure only on concavcly excavated dentin

. Apply thickness that creates uniform appearance

. Set mate als arc low strength, water soluble, and radiograph poorly

. Commercial examples: DYCAL (LD Caulk), LIFE (Ken), and Light Cured DYCAL

Zones of carious dentin - from innermost to outermost:. Zone | (normal denlin): totally normal dentin with no bacteria in the tubules.. Zone 2 (sublransparent dentin)t zone of demineralization created by the acid fromcaries. Damage to the odontoblastic process is evident, however, no bacteria are foundin this zone. Capable of remineralization.. Zone 3 (transpqrent dentin)2 softer than normal dentin, shows further demineraliza-tion. No bacteria are present. Capable of remineralization provided the pulp re-mains Yital.. Zone 4 hurbid dentin): is the zone ofbacterial invasion, tubules are filled with bac-ieria. Zone is not capable of remineralization and must be removed prior to restora-Ilon-. Zone 5 (inlbcted dentin)2 the o]utermost zone, consists of decomposed dentin that isfilled with bact€ria. Must be totally removed prior to restoration.

Four zones of an incipient lesion in enamel:

l.Translucent zone: the deepest zone, represents the advancing front ofthe enamellesion.2. The dark zone: does not transmit polarized light. Areas of demineralization and re-mineralization.3. The body ofthe Iesion: the largest portion ofthe incipient lesion. Area ofdemineral-tzauon.4. The surface zone: relatively unaffected by the caries attack.

The rate of senile caries is increasing in part becauseof the incr€ase in ginglval recession.

. Both lhe statement and the reason are correct and related


. The statement is corect, but the reason is NOT



38CopFiShr O 201l-2012 - Dental Decks

. Slowly progressing or arrested

. Pain is common

. Common in adults

. Extrinsic pigmentation

39Cop}'ighr O 20ll-2012 - D€ntal Dtrks

Cbronic caries is characterized by all of the followlngEXCEPT one. Which one is the EXCEPTIOIIT

The rising incidence ofroot surlace cales (sometime,s relbrretl to as senile cqrle.s/ can beattributed to the aging ofpopulations and the fact that most adults are retaining more teeth.

ln this population, there is increased gingival recession with exposure ofroot surfaces.

leading to the development ofroot surface caries. Root surface caries usually appears as

a well-defined discolored area adjacent to the gingival margin, typically near the CEJ. Itis found to be softer than the adjacent cementum or dentin. Root surface caries generallyspread more on the surface laterally around the CEJ, rather than in depth. In older pa-

tients, rampant caries can be caused by poor oral hygiene, decreased salivary flow, andside effects of medications. On a d€ntal radiograph, root surface caries appears as a

cupped-out or crater-shaped radiolucencyjust below the cemento-enamel junctron (CE.I).

Early lesions may be difficult to detect on a dental radiograph

Remember: Glass ionomer is a desirable restorative material for root surface cariesu here esthetics is not a major lactor.

L R€sidual caries is caries that remain in a completed cavity preparation,\otes whether by dentist intention or by accident.

2. Secondary /rrc arrenl) caries is decay appearing at the margins ofa restora-

tion and under it.3. The etiology of root surfac€ caries is now-a-days believed to be the same

as for coronal caries - S. mutans. S. sanguis, A. viscosus, A. naeslundii, Lac-

tobacillus. and Veillonella.

*** \\'ith chronic caries, pain is uncommon

Chronic caries is somelimes rcfcncd to as slow or arrested caries and is also characterized by the

:ollorr ing:. The lesion is shallow (smull lesion). The entrance to the lesion is wide. Dark pigmentation with leathcry consistcncy*** Chronic caries should bc completely removed when found in enamcl and close tothe DEJ.

Acute caries \\hich is sometines relencd to as rampant caries. is characterized by:

. ThL (nlran(c ro thc lcsion is smal

. The lesion is deep ard narrov (latge lesiott)

. Pain may be a feature

. Little or no staining

. Olien multiple. soll-to-the-touch l(sion5

. Most frequcntly found in children

. Rapidly progressing

Note: Changes ofthc pulp and dentin depend on the rate ofthe carious progression. The response

ofthe pulp to carious attack or thc trauma ofoperative procedures dcpcnds on the blood supply ofthc pulp and its cellular activitv.

Defense mechanisms ofthe pulp (loprolect it fiom irrit.ition)i. Sclcrotic dcntin /peritxhular dentin fbrmalioir: inilial delense. Whcn it occurs due to thc agingprocess it is called physiologic sclerotic dentin and when by initants it is known as reactive scle-

rotic dcntin.. Rcparativc dcntin liD'ildtion dentitl Jbmralio,r: sccond line ofdefense. lls vascularily (inllammation)

is degraded by Streptococcus mutans into andtberefore causing caries initiation and progression.

. Sucrose, glucans, lactic acid

. Glucose, glucans, lactic acid

. Sucrose, glucose, acetic acid

. Glucose, sucrose, acetic acid

40Copyighr C 20ll'2011- Dental Decks

The initiation of caries requires four entities.Which of the followlng is NO?one of them?

. Host

. Bacteria

. Carbohydrates

. Saliva

. Time

41

Coplright @ 201 I 2012 - Denral Dects

*** Sucrose is degraded by Streptococcrls mutans into glucans and lactic acid therefore caus-

ing caries initiation and progression.

Pit and fissure caries has the highest prevalence ofall dental caries. Smooth surface areas, es-pecially the proximal enamel surfaces immediately gingival to the contact area are the sec-

ond most sr"rsceptible areas to caries. Streptococci and lactobacilli species are common in thisarea. The facial and lingual root surfac€s may have plaque containing filamentous actino-myces species which can cause root surface caries. Remember: Lactobacillus species do notproduce the dextranlike, extracellular long-chain polysaccharides (fi'uctaus and glucans) as

do Streptococci species but produces a different extra-polysaccharide called lexan. The waythat the lactobacillus species cause dental caries in the pit and fissure areas is that it gets packed

into those pit and fissure areas thereby exerting its effect.

Fluoride treatments will dramatically reduce smooth surface caries though they are not as

effective in preventing pit and fissure caries. Sealing the pits and fissures just after tooth erup-

tion :nay be the single most impoftant procedure to help protect these areas from caries de-

struction.

Remember:The metabolic acids produced by mutans streptococci demineralize the tooth sur-l'ace and lead to dental caries. The enzyme glucosyltransferase lGlFl produced by mutans

srreptococci is the key factor in this process. Sucrose is a natural source ofenergy for this en-

z\rre. and GTF is the key enzyme that catalyzes the conversion ofsucrose to dextranlike, ex-

tracellular long-chain polysacchaddes (fructqns and g/llcar.t/, which extrude from thebacterium and stick to the tooth.

Important: Predominant bacteria found in dental plaque:. Streptococcus san gurs (found the earh esr) . Veillonella, Lactobacilli, and Fusobacterium. Streotococcus mutans. mitis. and salivarius

Dental caries is an irfectioos microbiological disease that results in the localized dissolution oftooth struc-turc. For caries to occur, a suscepiible host /d tootrl, microflora $ith cariogenic potential apldqrer, and a suitahle subsrate /dieldr'r . urhohv.lnues), all inli'ract to promote the severiq ofthe disease. \ot€: A cc(ain period

c'i tinle is also required fbr caries to develop.

The grealest percentage ofiooth loss in the first two decades oflifc lcrcept /),on the nutrral loss ofdeeicluou.ri!(r, is due ro untr€ated dental caries. The rate at which the carious desiruction ofdentin progrcsses tends

r,r be slower in older adults than in young persons due to gen€ralized dentinal sclerosis *'hich occurs with3g'rs.

Protectir e nrechanisms of saliva:. Bacterial clearance: glycoproteins in saliva cause some bacteda to agglulinate and then be removed bys\ rllon ing L5 L of saliva fbrmed each day

' Direct antibacterial activity: salivary proteins (e.g., ltso:yne, lactoperoidus(la.lofeffin dnd secrelor.t

r'-g J/ drscourage or clcn kill bacteria..

' BufTering crprcit): ofsaliva is mftjor rolc in caries protection.

' Remineralization: calcium, phosphate, potassiurn, and varying conccntralions offluoride are in saliva and

:..isi \\ ith remineralization- Some salivary proteins promote remineralization, thcsc include statherin, cys-r3iits. histatins. and oroline-rich Droteins.

L Fluoride and occlusal scalants modili the susceplible host /Ioor[r.Remember: Fluoride pro-

\ote3 vidcs lluoride ion lor remirleralization forming fluorapalitc. $'hich is more rcsistant to acid aFrack than intdcl hydroxyapatitc crystals in enamel.

' 2. Enamel demineralization occurs at pll 5-5 or belo$'. Remin€ralizrtion ofthe damaged tooth

srructurc occurs as the pH rises above 5.5.

L The prevalence of caries has bcen declining in children. A decline in adult caries is notas evident. Fluoridation has received thc most crcdit for thc decline in the devclopment olcaries.4. Pregnant patienfs, compared with similar non-pregnant paticnts, are likely to have thesame degrcc ofdcn{al caries, but more inflamed gingival tissues.

5. In ordcr to create smooth surface caries, a microorganism musl be able to produce dextran-like.extracellular long-chnin polysaccharides (frudans and gluuns). This dextranlike matcrial is a

similar product to that which is produced by btmaclcs lo allow them !o attach to lhe bottom ofaship. It is a vcry tenacious sticky material. Somil mcmbcrs ofthc streptococci family i/i.€., ,n xldr.r

strcpto.occi) arc able to producc cnough dcxtran lo attach to the tooth's surface.

There is rbundant evidence that the initiation ofdental caries requires a high proportlon of:

. Lactobacillus within saliva

. Streptococcus mutans within dental plaque

. Lactobacillus within dental plaque

. Streptococcus mutans within saliva

. Acidogenic, cariogenic

. Aciduric, cariostatic

. Acidogenic, cariostatic

. Aciduric, cariogenic

42Coplright e 201 l-2012 - Dert.l Decks

43CopI iShr O 2011,2012 - Dental D€cks

Thc first event in thc development ofcarics is the deposit ofplaque on the teeth. Dental plaqueis a highly organized gelalinous mass ofbacte a that adhcrcs to the tooth surfacc. Streptococcusmutans produce great anrounts of lactic acid fucidogenic), arc tolcmnt of acidic cnvironlncnts(ot'iduric.l, arc vigorously stimulatcd by sucrose, and appear to be the primar) orga nisms nssrrci-

ated with dcntal carics, howcvcr, thcy arc not the only organisms required for caries initiation.Olher mutans strcptococci species in humans can do this as well (for exanrple, S. sobrirtus).

\ote: X)litol. which is a natural sugar i'rom birch trees, keeps sucrose molecules liom binding\\ ilh mlrtans streptococci. Strcptococcus mutans cannot ferment xylitol. Additionally. xylitol causes

thc cn\ ironmcnt to bccomc morc alkaline inhibitine the baclerium's growth.

*** Streptococcus mutans are acidogenic and therefbre cariogenic.'Ihis means that thesespecies produce acid and therefore cause the initiation and rrrosression ofcaries.Cariogenic bacteria:

. Especially members oftbe mutans streptococci-group /e.g., Streptoco..cus nutans anclSt rcpt o t oc t Lts. .s o bri n us ). Lactobacilli casei\ote: \losl current research suggests that the microbial etiology ofroot caries is very sim_rlar to coronal caries. In the past it \\,as thought that Actinomyces species (.tis(,osu.\ andtl,tciIundii) were most commonly associated with root surface caries.

Essential properties of cariogenic bacteria:. -\cidogenic Qtoduce acid) and acidluric (being able to tolerate qn a..id enyitonment)**x \ote: Lactic acid is tbrmed in large quantities following the degradation ofsucroseb\ mutans streptococci,

. The abilit]'to attach to the tooth surlace. Note: Streptococci species have special recep-tors ibr adhesion to the surl'ace and also produce a sticky mat x that allows them to cohereIo eilch other. The abilitr to lbrm a protective matrix. Note: Streptococci species produce dextran-like.ertracellular long-chain polysaccharides (lructans and glutar.rJ, which extrude fiom thebacterium and stick to the tooth, which protects it fiom being removed from the tooth bysalir a, liquids. foods, and masticatory forces.

Dental plaque describes the soft white film of organized bacterial colonies (nain L,onpo -cTit,salivary glycoproteins, and inorganic material that readily forms on the surt'ace of teeth.

\ote: The strong correlation between the presence of dental plaque and the appearance ofdental caries and periodontal disease has been recognized for many years.

Large amount ofplaque on leeth. meaning many bactcria that canproduce acids (low pH, demineralization)

T!,rre of bacteria Large proportion o f "cariogen ic ' types ofbacteria. resulting inlower pH and sticky plaque and also prolonged acid production

High in carbohydrates, in particular sucrosel'sticky" diet leading tolow pH for a longer time

High .ugar lrequencl re.ulting in longer time per Jr\ $ irh low pH

Rcduccd salivary flow leading to prolongcd sugar clearance timeand to a reduced amount ofother saliva protectivc systems

Low buflcr capacity rcsulting in prolongcd timc with low pH

Comp

UV light curing systems are no longer used, that is because dualcure systems lixed the problem of"incomplete curing."

. Both the statement and the reason are corect and related




. NEITHER the statement NOR the reason is comecl

44Coplright ,e 20ll-2012 Dental Decks

OPERATIVE Comp

AII of the following statements are true concerning posterior compositerestorations -EXCEPI one. Which one is tbe EXCEPTIOM

. Posterior composite restorations are frequently indicated in the treatment of occlusallesions s'hich allow conservative preparations

. Posterior composite restorations are contraindicated in a patient with heavy occlusion( bruri.tnt)

. Posterior composites are contraindicated in patients with high caries risk

. Posterior composite restorations may be indicated for the restoration of Class II cavi-ties in premolar teeth where the appearance is very important, the cavity margins are

in the enamel, and the occlusal contacts are on tbe enamel

. Posterior composites are contraindicated for cusp replacements unless a dry operating

field is maintained 4s

Coplright c 20ll-2012 - Dental Decks

Light curing of compositc formulations arose dudng the late 1960s with the adoption of ul-ftavtolet (UV) light polymerized systems. In just a few years, it became obvious that visible-light cured (VLC) had many advantages over UVJight cured composites, and practitionersmade the shif't. Dentistry has been wed to VLC systems ever since.Msible light cr.rring systems have totally displaced the UV light systems. Also, visible lightcurjng systems are much more widely used than the chemically activated ones /selfcured). Anadvantage oflight cudng systems as a whole is that the dentist has complete control over theworking time and is not conlined to the built-in curing cycle ofthe self-cure. This is particul-arly beneficial when large restorations are placed.

Note: To deal with problems ofincomplete curing with VLC due to the thickness ofrestora-tions and filler particles scattering light, manufacturers have developed composite resins thatare dual-cur€d which combines self-curing and visible light-curing. Another polymerizationmethod is staged curing which is a two-staged cure. Howeyer, VLC composites are still themost popular today.

Remember: Visible light cured composites are single component pastes, and the polymer-ization process is activated by an extemal energy source. The alpha-diketone initiator (gelF

etu ll.t canphor quirorel absorbs energy from a visible 14 2.1 r n-blue light) llght source. Theketone absorbs energy and reacts with an amitl.e (added to the s)'sten lo enlut ce the affect ofrhe light-sensitive c..r/alrs, to produce ftee radicals.

L For large restorations (those that are u,ider than the diqmeter of tlte light tip),\ores cure each area for the full required time. Do not back off light tip until it lights up

entire sud'ace of restoration.

2. Visible lighrcuring involves light energy in the range of,ll0-500 nm with a peak

intensity ofabout 470 nm.3. The minimum acceptable level for visible curing light outputs is 300 mwcmr.

Allhough Ihe ADA does not endorse composite resins as a substifutc for a[ralgam in postcrior teeth,cLrtuposite restorations can be excellcnt if stricl guidelines are follotved for tooth selcction and if there\rorations are done properly. But remember. composite resin restorations arc infcrior k) amalgam iniarms of compressive strength and abrasion rcsistancc foaclr!a/ )rc4rl. Also, curent composite resinsrrr e no capabilirv to providc an anticarjogcnic cffect as do freshly placed glass ionomer or resin modi-i:l.l gla\\ ionomers, for example.

lhc nrLrst scrious limitation of the visiblc light-cured posterior cornposite restoration is the polymer-ization shrinkage, \\'hich can cause intemal stresses and gap formations at butt-joint interfaccs. whichr:a ieen rt the gingi\al lloor ofClass II and V resiorations. Important: Stress from polvmcrization.irinkase is influenced by rcstorativc technique, modLllus ofresin elasticity, polymerization rate, and ca\.:5 .onlisuration or "C-factor." Thc C-t'acIor is the ratio between bonded and unbonded surfaces; an in-.r.iic in this ratio rcsults in incrcascd polymcrization stress. Three-dimensional cavity preparations,C/,r-rr 1r have the highcst (nost unJbtorable.) C-factor because only outer unbonded surfaces absorb.irer\ To rninimize the sttess fiom polymerization shrinkagc, efforts have been directed torvard im-p:.ir ine placement techniques, material and composite formulation. and curing methods. Incrementalcunnq rc-duces the C-factor und, therefore, reduces the residual stress ofthe resulting composite restora-tion.

\ote: Thc major indication for the use ofpostcrior composjtcs is the dcmand for csthetics by thc dcn-ril and paticnt. Othcr criteria are non-involvement of cusps, minimai occlusal contact, no cxce\si\,c\\car. and the isthmus nrust be no uidcr than onc-thjrd ofthe intercuspal distancc.Remember: Compositc is thc material ofchoice if the patient has a documented allergy to mcrcury.

Important: In thc past, postcrior compositc restorations were contraindicatcd in a patient with a caricsaclivc mouth. Ncw conccpts strcss that you should manage the disease (i.e., dental carie.rl bcforc or at

the same time as you are treating the consequence ofthe discasc (i.e., hr placing restorutions). Therc-tbrc, the currert literature does not see a special probJem for these restorations in caric\'active pctienrs.They havc as bad a prognosis as any othcr rcstorative trcatment ifthe diseasc is not managed simulta-neouslY. Note: However. for the National Boards jt js still a contraindication.

Which property of lilled resins is primarily to blrmefor the failure of Class II composite restorrtlons?

. Low flexural strength

. Low compressive strength

. Low tensile strength

. Low wear resistance

46Coprdgft t C 201 l':012 - Dental Decks

Which composite typ€ is 70 to 77 percent lilled by volumeand has en average prrticle size r.nging from I to 3 pm.

. Microfills

. Hybrids

. \{icrohybrids

. Packables

. Flowables

17CoDright O 20l l-2012 - Dental Decks

Ideally, composite resins should be used only to restore n.rinimal cavities in posterior teeth.Its use should be restricted to those instances where it will not be subjected to excessiveocclusal forces and \,!,here, when teeth are in occlusion. there is cusp-to-cusp contact andnot cusp to restoratron.

For Class III preparations using resins, the rule ol extension for prevention into embra-sures is disregarded for Class III esthetic restorations. This compromise is for esthetic rea-sons, as well as the unnecessary removal oftooth structure which will often involve theincisal edge. Ifpossible, the outline form should place the gingival margin incisally fromthc crest ofthe gingiva.

When placing the composite resin in a Class III preparation, the wooden wedge is placedin order to provide some separation of the teeth (for contac t), to stabilize the mylar strip.and to avoid creation ofexcess gingival flash. Important: Restoring the contact area mustbe done properly and diIgently.

Remember: For Class III composite preparations the retentive grooves are placed alongthe gingivoaxiaf and incisoaxial line angles (entirely in dentin). These grooves will pro-r ide tbr mechanical lock in the preparation. Small, rounded retentive areas are preferred,as contrasted to sharp angles. since it is difficult to insert viscous composite material intothe sharp angles.

\ote: Once proper finishing has been completed, a thin layer ofunfilled resin can be ap-plied as a glaze (this seal.s the nrargiu.s and snroothes the sujitce). The difficulty in fin-ishing cornposite resin restorations is due primarily to the softness ofthe resin matrix andhardness of the filler particles. The most desirable finished surl'ace for composites is ob-lained rvith aluminum oxide disks.

The iirst composite resins that were developed contained large filler p^rticles (10-100 mictons in did-,rrcrcr'r and became known as macrofill materials. In the past 20 I'ears. rcsin-based composites havc beenimFrlrled b,v reducing particle sizc. increasing filler quantity, improving adhcsion betrvccn filler and or-!anic miltrix. and using low-molecular-u'cight monomers to improve handling and polymcrization. Bya\l!'imcntinq rvirh particle size, shape and volume, nanufacftrrers have introduced resin-based.oinpL)sites \\ ith diffcring physical and handling properties. Microfill. hybrid, microhybrid. packabler.J il!r\\ able composites now are available to be used for varying clinical situations.

. \[icrofills: are 35 to 50 percent fillcd by volume and havc an average particle size ranging from 0.04t!, lr I n)icromctcr (lrm). They havc lo*,modulus ofelasticiry and high polishability; howcvcr, theya\hibit Io$ t'racturc toughness and increascd marginal breakdown.. Hl bridsi are 70 to 77 percent fil1cd by volumc and an avcrage particlc size ranging from I to 3 Am.Th.) do nor maintain a high polish but do have improved physical properties when compared withtr:cro lls.. \licroh] brids: are 56 to 66 percent filled by volume and have an average particle size ranging fromar I t.) 0. E !m. They have particlc sizes small enough to polish to a shinc similar to microfills but Iargc.nough ro be highly filled, thus achieving higher strcngth. The results are resin-bascd composites withgood ph\sical properties, high polishability and improved wear resistancc.. Packable composit€si are ,18 to 65 percent filled by volume and have an average particlc size rang-rnc iroor 0.7 to 20 pm. Thcir improved handling properties arlj obtaincd by adding a higher percent-age of irregular or porous filler, fibrous filler and resin natrix. They arc indicatcd for stress-bearingarcas and allorv easicr cstablishmcnt ofphysiological contact points in Class II rcsrorations. Researchhas sho\\ n that thc physical properties ofpackablc composites are not superior to conventional hl,brids.. Flonable composites: are 44 to 54 percent fi11cd by volLrme and havc an avcragc particle size rang-ing frorn 0.04 to 1 pm. Thcir decreased viscosity is achieved by reducing the filler volumc so they arelass rigid. yet they arc pronc to morc polymerization shrinkage and $,ear than convcntional compos-ites. Flowable composites have becn said to improve marginal adaptation ofposierior composites byacting as an clastic. stress-absorbing laycr ofsubsequently applicd rcsin-bascd composite incremcnts.

Composite filler particles function to do oll of the followingEXCEPT one. V,{hlch one is the EXCEPTIOM

.Increase the coelficient of thermal expansion

. Increase the tensile strength and compressive strength

. Reduce the polymerization shrinkage

. Increase the hardness

. Improve the wear resistance

48Cop!.rjghlO 201l-2012 - Dfrral Decls

\When comparing the physical properties of lilled resins

to unlilled resins, all of the following are true EXCEPI one,

Which one is the.EXCEP?/OM

. Filled resins are harder

. Unfilled resins have a higher coefficient ofthermal expansion

. Filled resins have a higher compressive strength

. Unfilled resins have a lower modulus ofelasticity

. Filled resins have a lower tensile strength

49Coprighr O 20l l-?012 - Dentat Decks

*** This is falsei fillers reduce thc coct'ficicnt ofthermal expansion.

Fillers are placed in dcntal compositcs to reduce shrinkage Llpon curing- Physical propenies ofcom-posite are improvcd by fillers, howcver. composite characteristics change based on tiller material, sur-face, sizc, )oad, shapc, surfacc modifiers, optical index. filler Ioad and size distribution.

Composition of com posites (lilled resi s)l. Fill€r particles: the filler particles us€d are strontium glass. barium glass, quartz. borosilicatc glass.ceramic. silica, prepolymerized resin, or the likc. Thc particles are usually combined with 5-109/o

weight ofvcry small-stzcd (0.04 pn)patticles ofcolloidal silica. Note: One micron is a critical fillersize. Fillers greater than one micron are visible to the human eye. As resin matrix around filler par-ticles wears. the filler becomes prominent and visible so the composite surface looks rough. Fillerslcss than one micron do not producc a rough appearing surface with aging. Fillcrs grcatcr than onemicron arc rcfcrred to as macrofills and fillers less than onc micron arc referrcd to as microfrlls lmidiand mini arc in be\reen macto and micr?). A new classification offiller is the nano particles. Thenrno particles fill betw,een all other particles to further rcduce shrinkage. A mixture ofdifferent part-iclc sizcs is rcfencd to as a hybrid.. \Iatrir: difunctional nonome rs either BIS-GMA or urcthanc dimcthacrylate (UEDMA). In some

cases. a proportion of a lowcr molccular wcight monomer such as TEGD\lA is introduced to lowcrIhe \ iscosiry.. Coupling agent silane $hich acts as an adhcsivc betwccn thc inen filler and the organic matrix.

t** Recentl!,. ions have been added to the filler to produce desirable physical changes. Lithium and

alunlrnum ions makc thc glass casicr to crush to gcncratc small panicles. Barium, zinc. boron, zirco-nrum. and vttrium ions producc radiopacity in thc fillcr particlc.

L The normai wear mechanism ofthc compositc resins is best explained by the following

\ote* eventsr abrasion ofthe matrix, followcd by cxposure offillcrparticles and subsequent dis-lodgencnt of thcse fillcr particles.

2. With any ofthe restorative resins, cavity vamish or zinc oxide eugenol should not be used

as they might inhibit polymerization. The use ofa cavity vamish might prcvcnt dircct con-tact between the composite and the tooth structure, preventing bonding.

The most common classification :nethod for composite resins is based on filler content. fillerparticle size, and the method of filler addition. AImost all important properties of conpos-ite resins are improved by using higher filler levels. However, as the filler level is increased,the iluidity decreases.

Highlr' filled resins typically contain large filler particles but this composition results in a

roush finished surface. Smaller liller particles are used to produce a resin that has a relativelysmooth finished surface.

Resin filler particles are called:. )lacrofillers: l0-100 microns in diameter.llidifillers: l-10 microns in diameter. \linifillers: 0.I- | microns in diameter. \licrofillers: 0.04-0.1 rnicron in diameter Examples include Denta-colour, Durafill,Heliomolar RO. and Silux Plus.

*** Hl brid resins contain a mixture ofparticles with different diarneters which allows highertiller levels and still permits good finishing. The principal particle size is in the I to 3 pmCharjsma. Herculite XRV, Prodigy, Tetric ,TPH (Total Perforuqnce Hlbrid). and Z- 100 are ex-amples.

\ote: Hybrid and microfill resins utilize colloidal silica fillers which are useful for in-creasing the hardness and wear resistance ofthe base rcsin matedal while maintaining high pol-r.h.rbility rrnd or erall estheric qualities.

*** New resins with nanofillers that range in size fiom .005 to 0.01 micron have recentlybeen developed. These particles are so small that very high filler levels can be achieved whilestill maintaining workable consistencies. Supreme H-NF and Simile H-NF are examples.

*** This is false; filled resins have a higher tensile strength.

. UV light is better than visible light

. You must keep the light 2 mm away or more

. You should cure for longer than normal

. Darker shades have less chemical bonding

50

Coplri8ht O 201 l-2012 - Dental Decks

51

Copyigh O 201l-2012 ' Denral Deck!

All of the following are current monomers for composite

resins XXCTPI one. Which one is the EXCEPTIOM

. bis-GMA

. P\{MA

. UEDMA

. TEGDMA

Important points to rcmcmber whcn using a visible light-curing unit:. Hold the light as closc to thc rcsin as possiblc within 2 mm to bc cflictivc.. Place a shield betwccn thc lighl tip and thc opcrator's cycs. Paticnrs who havc had rcccnt cataract rcmoval shouldhavc protcction also. Note: Studics havc shown that thc visiblc light uscd in polymcrization ofphoto-activated mai,crials can ciusc rctinal damagc always usc a shicld and cycglasscs for pfotcclion.. For deep restorations, you have to cure thc composilc in incrcncnts ifyou don t, thc dccpcr arcas will notbc curcd. lmportanti No morc than 1.5-2 mm incrcmcnts should bc Iight curcd at onc limc.. \'lake sure the bulb in the light is sdll powcrful cnough thcy havc commcrcially availablc p.oducts to tcslthc bulb.. With darker resin shades, curc a litdc longcr.

M,y cxtcnd lo break proximal conracrInclud. dj.ccnt suspicous ar.as

Rcmovc cancsj .ot usually unifdfr

Unifoft 0.2-0 5nm insidc DEJ Rmolc cdicsi nol usually u.ifom

Creare 9o-desree narsin

For csthct'cs, do nor berel Mginstnat re on furdion:l pElhs

Tcrrurc of pr.prr€d wrlls

Prim.n rctcntion fom Nonc (srablhhed by rouSldc$ &

Secondrry rclcntion forn Groorc\. n!tr. l!ct\. prn\. bonJrn! Bond,ngr gr6vs fdchs lll&v

tla' nooF, roundcd in,cmil Inc an!hs

P.ovrdc .pproxrndely : nnbcls.cn

Ca (OIl). orcrdirecr or indircct pulp

(,lumr Dc\Ln\iLizcr tr hcn nnr hondinq Scrlcd by bondjng systcn nsed

Dcntal resin composites typically contain a mixture ofsoft, organic resin rntri x (pol-vmer)

and hard. inorganic filler particles (ceramic). Other components are included to improvethe efTicacy ofthe combination and initiate polymerization. The resin matrix consists ofmonomers. an initiator system, stabilizers and pigments. The inorganic filler consists ofparticles such as glass, quartz and colloidal silica. The matrix and filler are bonded togeth-er rr ith a coupling agent. The peformance ofresin composites is dependent upon thesebasrc components. The recent improvement in these materials has prirnarily focused ontrller technologv. but the resin monomers have remained largely unmodified.

The orsanic resin matrix is a high molecular weight monomer such as bisphenol A gly-c jdr I methacrvlate (bis-GMA) or urethanc dimethacrylate (UEDMA). bis-GMA, rvhichstands fbr 2.2-bis 1,1(2-hydroxy-3-methacryloxypropoxy) phenyll-propane, is rn aromaricmethacn late. Terminal methacrylate groups provide sites for free radical polymerization;]l sets to a relatively rigid polymer because it has two benzene rings near rts center.

T\\ o djsadvantages of bis-GMA are its questionable color stability and high viscosity;hi-uh |iscosity is the result of its -OH groups which hydrogen bond; to lower the viscos-itr. manufacturers add low-molecular-weight f/olr-vrsco.!iry, monomers like triethyl-eneslrcol dimethacrylate (TECDMA) and ethyleneglycol dimethacrylate (EGDMA);thcse reduce the bis-GMA's viscosity, increase crosslinking, and increase hardness. An-other monomer frequently used as the matrix for resin composites is urethane dimethacry-late. This monomer was introduced in 1974 and is a brittle material with low viscosity.

Important: The high filler content and the bis-GMA resin matrix drastically reduce thecocflcient ofthermal expansion (as co mpared to the unfilled acrylic resins).The filler alsoreduces polymerization shrinkage and increases hardness.

The main ingredient in tradltlonrl acrylic resin temporarymaterials for intraoral fabrication is:

. Ethyl Methacrylate

. IsobuWl Methacrylate

. bis-GMA

. Ethylene Imine

. Methyl Methacrylate

52

CoD,riglit O 201 I -20 l2 - Denral Deck

. Amalgam

. Gold

. Unfilled resin

. Filled resin

CoplrightO 20ll-2012 - Denral Decls

For both inlays and onlays, plastic r'acry,1ic) provisional restorations are fabricated prior to thefinal restoration being cemented. Their physical properties enable them to withstand occlusalibrces and the adverse oral environment for short pedods of time. These temporaries must:restore and maintain proxilnal contacts, restore and maintain the occlusion, restore and main-tain tooth contours and the margins should be closed and flush with the tooth.

Methyl methacrylate, ethyl methacrylate, and ethylene imine resins have been employed toproduce provisional restorations. However, methyl methacrylate /MM.4/ is by l'ar the mostcommon. lt is the liquid monomer that is mixed with the polymer polymethyl methacrylate(the powler). The monomer partially dissolves the polymer to form a plastic dough.Note: The monomer is polymerized by the action of an initiator (benzoyl peroxide).

Important: Methyl methacrylate maintains the occlusal and interproximal contact relation-ships.

Remember: Polyme zation should not go to completion in the mouth for fear of overheat-ing the pulp and that the provisional will not be able to be removed from the tooth.

\ote: These provisionals are usually cemented in with a ZOE cement.

Classifi cation for provisional restorations:- Intracoronal Restorations:. ZOE-based and/or ZOF-ba.ed temporaries

- Preformed Provisional Shell Crowns:. Polycarbonate Crowns. \letal Alloy Crowns

- Custom-Fabricated Proyisional Crowns:. \{N{A-like products (MMA-/PMMA, IBMA/PBMA, EM,A,/PEMA) - self-cure. Epimine-imine products - self-cure. Bis-acryl, bis-methacryl, bis-GMA-like self-cure, dual cure, VLC

- Resins and Composites

This characteristic probably offsets to some degree the undesirable effects of the rela-tively high coe{ficient ofthermal expansion, which is 7 to 8 times that ofthe tooth. Dueto this low thermal conductivity and diffusivity, the unfilled resin restoration changes tem-perature quite slowly. Therefore, it takes considerably longer for the unfilled resin restora-tion to become hot or cold, as compared to metallic restorations, which have a highthermal conductivity and diffusivity.

The first materials that rvere used as esthetic materials were based on silicate cements. Dueto solubility problems the silicate cements were replaced by unfilled acrylic resins. Un-filled acrylic resins contrated excessively during polymerization permitting subsequent

mareinal leakage and were not strong enough to support occlusal loads. These unfilledacrylic resins have been replaced by filled resins (also colled composite rcsins). A filledresin is one in which an inorganic inert filler (lsrialU silica or quartz) has been added tothe resin matrix.

1. The compressive strength of the unfilled resin is low; the yield str€ngth\ot* and tensile strength are even lower

. 2. Unfilled resins are the softest of all restorative materials //ou, vlear resist-ance

-no Jiller)3. Compared with amalgam, filled resin, direct gold and silicates; unfilledresins show the greatest extent of marginal leakage related to temperaturechange (percol ation) .

Remember: A low co€flicient of thermal conductivity is most characteristic ofcurrentlyavailable cement bases.

' Acid etching enamel prior to placement of a composite restoration is required. for oll of the following reasons EXCI9PI one. Which one rs the EXCEPTION?

. Conserves tooth strucfure

. Reduces microleakage

. Provides micro-mechanical retention

. Increases esthetics

. 37% Phosphoric acid

. l3% Phosphoric acid

. 3 79,'o Hydrochloric acid

. 13% Hydrochloric acid

54Copright O 201 l-2012 - Dental Decks

Cop)Tight O 20ll-2012 - Dental Decks

+** This is false; acid etching does not increase the esthetics ofthe enamel margin. Donot be confused by the fact that you acid etch the bevel, which itself functions for reten-tion and esthetics.

One olthe most effective ways ofimproving the marginal seal and mechanical bondingofcomposite resins to tooth structure is to condition or pretleat the enamel with acid priorto insertion ofthe resin. This procedure is referred to as "acid-etch" t"hni'"'

Purposes of acid etching:

LIncreases suface cnergy which promotes wetting and adhesion.

2. Chemically cleans the tooth stnrcture which also promotes wetting and adhesion.

3. Creates micropores 1br micromechanical retention.

Important: Acid etching paves the rvay for resin "microtags" ivhich produces a muchinrproved bond of the resin to the tooth. The effective tag length as a result of etchingon adult anterior teeth has been demonstrated to be approximately 7 to 25 mm.

This "acid-etch technique" consen'es tooth structure, reduces microleakage, improvesestlletics. and provides micro-mechanical retention.

l. The aim is to cause maximum enamel dissolution with minimum precipi\()1e3 tation ofcalcium phosphate salts.

2. Studies indicate that acid-etched composite resin restorations have the bestinitial seal (nicroleakage), however, over time this weakens (amalgam has

rhe hest st al ovt'r Iima).

Standard acid etching ofenamel involves the application ol37% phosphoric acid for l5seconds with a l5-second rinse and a l5-second drying to roughen the surface of theenarrel. This lonns little tags approximately 7-25 micrometers in length, providing me-chanical retention. When using the acid etch technique all enamel cavosurface margins

should be chamfered or beveled (this process fonns obtuse angles).

Be\ eling the enamel margins of anterior resin composite preparations is recommendedprilrr lo etching to:

. Reduce microleakage

. Irnpror e eslhetics: by gradually blending the resin composite into the enamel

. Increase bond strength: transversely-cut enamel, when etched, provides a strongerbond to resin composite than etched, longitudinally-cut enamel.This occuts because

rhe end of enamel rods are more completely exposed to the etchant and, therefore,

more effective etching is accomplished and more retentive tags are produced.

Remember: Once you etch the tooth, it cannot be contaminated with saliva. Ifit does, youmust complete the €ntire etching procedure again.

L The depth of enamel dissolution caused by acid etching is approximatelyI0te3 l0 to 15 microns.

2. Little correlation exists between resin tag length and enamel/resin bond

strength.3. Although liquid etchants produce a more uniform etch and a greater num-ber of tags than do gel etchants, no difference in bond strength has beendemonstrated between the two.

rounded intemal line angles because it isto compress composite into them than anralgam.

. more, easler

. less, harder

. more, harder

. less, easier

56

Coplright O 201l-2012 - Dent.l Decks

. Smear layer removal

. Smear plug removal

. Peritubular dentin decalcification

. Intemrbular dentin decalcifi cation

Coprighr C 2011,2012, DentalDecks

*** When restoring teeth with composite resin, it is much easier to compress the mate-rial into rounded line angles.

The outline form ofa Class V restoration is not always uniform, as it will vary depend-ing on the location and amount of caries or decalcification

-the size and location of the

carious lesion determines the outline fonn ofthe cavity preparation. When the carious tis-sue has been removed and the margins are on reliable enamel or dentin, the outline willusually be rectangular with the comers round, ovoid, or kidney-shaped, very much re-sembling the amalgam Class V preparation except that the intemal line angles are muchmore rounded.

Recent research indicates that preparations with bevels are more resistant to microleak-age as compared with those without bevels when an acid €tch technique is used. The

bevel permits the acid to attack the enamel rods at the appropriate angle for maximum ef-fect. The cavosurface nargin is beveled wherever it is placed on enamel -- this is a majordiii-erence betrveen composite and amalgam preps. When possible an enamel bevel 0.2 to0.5 mm uide is advocated as the final stage ofpreparation. This bevel is etched and pro-r ides retention for the restorative material as well as improving the marginal seal and

mainraining the strength of the resin with su{ficient bulk. Retentive grooves supplement

the etched enamel retention (these grooves are placed in both inci,sal ond girtgival axialline andes).

\ote: Whenever possible, use a composite syringe to place the composite resin in the

resroration, this will minimize the possibility of trapping air in the final restoration.

Drnrin bonding systcms (DRS) consist ol3 componcnts:. tltchant: Typical acid conditioners includc phosphoric acid. EDTA. malcic acid, and citric acid.. Primer: is dcsigned to pcnctralc through lhc rcmnanl smcar Iayer and into thc inlcrtubular dcntin to fill ibc

lpaccs lcli by dissolvcd hydroxyapa(i1c crystals. This allolvs thc primcr o form an intcrpcnctrating nclwork a.ounddrnrrn collagcn. Note: Thc bonding primcr is based on hydrophilic nrcnonrcrs such as hydroxyclhyl mcthacrylatc

. Bonding agcnt: unfillcd rcsin adhcsivc is applicd. The resin is then curcd (light-, self-. ot dual-(urc.i). This layer

..rn 'ro$

bond ro compositc or amalgan.

\ r. . r. .rt i .|rc-! Jcnrrrr bond ng .y.rcm dc,ign.::-component slstems (LP+ B) l -com ponent slstem s (EPB). C l..rrill SE Bond & LinerBond 2v (Kuraray) . AQBond (Sun Mcdical). Tlnrn SPE lBisco) . or Touch-and-Bond (ParkelL)

. Otrrbond Solo SE Plus (Kcn) ' Adper Prompt or LP3 (lNt-ESPh)

l-component s]'stems (E + P+ B) 2-component systems (E + PB). S..rchbond \luhipurposc Plus (lM) . Syntac Singlc Componcnt (lvoclar). Prr--:r3quick (Lltradcnt) . Onc Coal Bond (Coltcnc,'Whalcdcnt). B.nd-lt {Jcncnc Pcntron) . Bond-l (Jcncric'/Pcniron). \:l-Bond I (BISCO)

Grr.yrtionr oiDcntin Bonding Systctrs /rAS).I Firjt Gencralion DBS's (bonded to smcar laycr): S..ond Cjcncration DBS's (modificdlrcmoved smcar laycr)I Third Ocncrrlion DBS's 0nodified/rcmovcd smcar laycr;produccd hybrid laycr).1 Founh Generation DBS's (optimizcd for sncar laycr modilication + dcrlin

"clting): three-stcp ctch & rinsc

5. fifih Cencralion DBS's (Reduccd-Componcnt Bonding Syslcms): two stcp ctch & rirsc(r. S i x th Ccncrarion DB S's (Truc Onc-Componcnt Ro,rding Systems): subd iv ided into Ttpe | (i.e., tr|o-step: acid-

ilietl priner and adhesive applieA s?parutelt-) andTlpe 2 (i.e., one-stq, sclf-et&ing adheti|t's drc niietl and ap'

7. S.\'enth Ccncration DBS's: adhesivcs rcquirc no mixing and arc simply placed in onc stcp.

L Dentin and cnamel bonding strcngths arc simllar tbr currcnt total-ctch products.

.,,--_.. .2. Must lotrl clch dcntin bonding systems bond bcltcr lo moist dcnlin. usc Aqua Prcp orCluma Dcscn--\ore3. \rLrzcr to kccp ocnrrn mor\r.

atlAAr;,. 3.lnamcl bonding is fhst, strong, and long-lasting; dcn(in bonding is slower, may bc strong, bu1 may

not bc longlasting.

A gold onlay you plac€d last week fails, which ofthe followingreasons is most likely responsible for the failure?

. You "capped" the functional cusp

. You "shoed" the functional cusp

. You "capped" the non-functional cusp

. You "shoed" the non-functional cusp

58

Cop)'right C 201l-2012 - Dental Decks

Rapid cooling by immersion in water, ofa dental casting from thehigh temperature at which it has been shaped is referred to as:

. Annealing

. Quenching

. None of the above

59

Coplright e 20ll-2012 - Dental Decks

*** Important: "Shoeing" is never indicated on functional cusps.

Onlay preparations:

. Resistance form: two types of cuspal protection:

l. "Capping": refe6 to the complete coverage of functional cusp with 1.5 mm ofgold.2. "Shoeing": refers to veneering of non-functional cusp by means ofa slight finishingbevel.Note: Except in situations demanding a minimal display of gold (primarill, the ./hcialcusps oJ naxillary molars and premolars), capping is always preferred over shoeing.

Shoeing

Onla) preps have:. Improved resistance to fracture due to cuspal coverage. Thickness ofgold on occlusal (I .0 mm on non-fitnctional cusp and L 5 mnt on functional( r/-!q/ resists deformation. Reliance on tapering lingual and buccal walls for retention. Reciprocation of mesial and distal axialwalls (near parallel). Extemal extensions over the cusps add retention ifnearly parallel to line ofdraw

This usually is undertaken to maintain mechanical properties associated with a crystallinestructure or phase distribution that would be lost upon slow cooling.

Tlr o advantages gained in quenching:

L The noble metal alloy is left in an annealed condition for burnishing, polishing, andsimilar procedures it maintains its malleability and ductility.:. \\hen the water contacts tlle hot investment. a violent reaction ensues. The invest-nent becomes soft and granular, and the casting is more easily cleaned.

Remember: The set of processes, annealing, hardening and tempering are collectivelykrorr n as "heat treating."

. -{nnealing is the softening ol a metal by controlled heating and cooling to make itsmanipulation easier. It makes the metal tougher and less brittle.

. Tempering is hardening something by heat treatment.

r----al

IH

Which of the following situations delines anIndication for a Class II gold inlay?

. A young patient with high caries rate

. A patient with little money to invest in dental work

. A patient very concerned about esthetics

. A patient with a large lesion, buccalJingually

. A patient with low caries rate but a history ofperiodontal problems

60CopltiShr O 201 l'2012 - Dental Deks

Z\' Gold Ntloys _ upon solidification in the investment This needsto be compens*ted for by an equal amount of_ ofthe mold.

. Shrink, expansion

. Expand, shrinkage

. Shnnk, shrinkage

. Expand, expansion

61

Cop)'righr O 20ll-2012 - D€nral Decks

Disadvantages and contraindications for a Class II gold inlay:. Expense: gold is 6 to 7 times more expensive tban amalgam. Time: at least two visits are necessary. Minimal lesions: best restored with gold foil. Large lesions: if cavity width exceeds one-third the intercuspal width, the toothshould receive cuspal coverage. In patients with a high caries rate. Young patients. Color: not esthetic

-{dvantages and indications for a Class II gold inlay:. Tooth contours: where optimum contour and surface finish is desired to maintainperiodontal health. Str€ngth.ln patients with a low caries rate. l'se against another gold restorations. Bio-compatible

\ote: A gold inlay is defined as a cast gold restoration which derives its retention fromlhc internal walls oflhe cavity preparation.

Gvpsum bonded investments are used with Type I. II, and III gold alloys. Gold alloysused for cast gold restorations shrink upon solidification. Therefore, it is necessary tocompensate for the solidification shrinkage of the specific alloy used by expanding themold enoueh to equal the shrinkage.

The dimensional compensation necessary is accomplished by tu'o methods ofexpansion:1. Setting expansion: occurs as a result ofnormal crystal growth but can be enhancedby'' alJo$ ing the investment to set in the presence ofwatel producing hygroscopic ex-pansion.2. Thermal €xpansion: is achieved through the normal expansion that occurs uponheating the silica (quartz or cristobali/e). Note: The amount of expansion depends onthe particular refractory material used (cristobalite produces greater expansion thandoes quartz).Important: Thermal expansion is the principal cause for mold expansion.

Variables that infl uence expansion:. The older the investment is: the less it will expand. Ifthe water/powder ratio is increased: the expansion is reduced. The longer the spatulation time: the greater the expansion. The longer the time between mixing and inmersion in a water bath: the less it willexpand

Note: During solidification ofan alloy, the number ofgrains forming depends on the rateofcooling and the presence ofnucleating agents.

Which of the following finishing margins is essentially a hollowground bevel, creating more bulk ofrestorative mat€rial near the

margin and providing a greater cavosurface angle?

. Knife edge

. Beveled shoulder

. Chamfer

. Shoulder

Copyrigh €r 20ll-2012 - Dental Decks

. Undercut on mesial

. Undercut on buccal and lingual walls

. Occlusal lock (dovetail)

. None of the above

Cop)'righr O 20ll-2012 - D€ntal Deks

Whlch of the following allows for proper retention whenpreparing a tooth for a disto-occlusal Class II gold inlay?

A chamfer is essentially a hollow ground bevel. lnstead ofa flat diagonal cut across thecavosurface margin, the chamfer is "scooped out" creating rr.rore bulk ofrestorative ma-terial near the margin and providing a greater cavosurface angle.

Cavosurface angle configurations that are used when preparing a tooth for a cast goldrestoration:

. A bevel is a diagonal cut across the cavosurface margin which is flat in one dimen-sion only and curved in its other dimensions. It involves the extemal ends of enamelprisms and follows a continuous cuwed outline. It can be either a short bevel whichcuts only the external one-third of the enamel prisms, a full bevel involving the en-

tire thickness of enamel. or a wide bevel involving not only enamel but some dentinas well.. A plane is a diagonal cut across the cavosurface margin which is flat in all dimens-ions. A plane may involve the entire thickness ol enamel (u,hich it usually does) ormost of it but cannot be curved in anv direction.

When designing a Class II preparation for an inlay, an occlusal lock or dovetail should

be established to prevent proximal dislodgement. Also, the marginal ridges ofposteriorteeth that are restored with cast gold should be rounded to help form the occlusal em-

brasures and be in contact with the cusps ofthe opposing teeth. Marginal ridges should

be the same height as the adjacent tooth's marginal rtdge (or else you can create an in-turlArence in retrusive movemenl).

l The cement does provide some retention; however, the preparation design

does as well. The cement's main function is for marginal seal, not retention.

2. When rernoving a Class ll inlay, the method of choic€ is to cut through the

isthmus to remove the occlusal and proximal pieces one at a time.3. The restoration will not seat ifthere are undercuts. Actually this holds true

for all cast metal restorations. See picture above ofa Class II inlay prepara-tion.

A patient arriv€s at your oflice with their full gold crown in hand,They explain to you thlt anoth€r dentist delivered itjust last we€lc

You then examine the crovm and the preparation.What is themost likely reason the the crown fell olf?

. There was very little cement in the crown

. The preparation was only 4 mm high

. The preparation walls were tapered at about l5'

. The margins were jagged and undefined

64CopFightO 20ll-2012 - Denbl Decks

The lab calls your o{fice and asks ifyou want a prrticularcasting done in N base or a nolrle metal. Which of the

following responses is appropriate?

. Base. because the patient has a bad bruxing habit

. Noble. because the patient has a bad bruxing habit

. Base, because the patient wants a gold tooth

. Noble, because the patient wants a gold tooth

65Copright C 201 l-:012 - Dental Decks

Taper provides the optinal friction between the walls and the casting, which is the main re-tention. The f'enule (or height) of the preparation also provides the friction and thus retention,but 4mm is enough /3 nn is minimarl.

lmportant: For maxjmum retention ofcast gold restorations. the axial walls should be as par-allel as possible and as long as possible. Retention is directly proportional to the area oftheaxial walls and their parallelism. The axial walls should converge slightly frorr the gingivalwalls to the pulpal wall.

Retention form depends on:. Length of walls lrn iniuwn 3 un): the longer tbe wall, the grcater the amount ofdraft/draw.. Taper ofwalls. fmportant: provides for draw or drafl dn olderJbr the .asting to be placedonto the tooth) b\t also to provide for an appropdate small angle of divergence (2 to 5 de-grees per t'all) frorn the line ofdraw which will enhance retention form.Ke\ point: More parallel - more rerenlion. Circumference

-{di antages of cast gold restorations:. The.v are very strong and able to withstand the forces ofmastication. Thel are ideal for occlusal rehabilitation. The)'are kind to the gingival tissue

Disadi antages of cast gold restorations:. Eithetics. Cost. Time-consuming. Difllculty of technique. The need to use cement, which is the weakest point in the cast gold restoration. Gold has a high themal conductivity

\n allof is a mixture of two or more materials that are mutually soluble in the liquid state.

A pure metal solidifies at a constant temperature, whereas alloys solidify through a range

tri temperature.

Base metal alloys i/also called non-precious netols) arebased on active metallic elements

lhat conode. but which develop corrosion resistance via surface oxidation that produces arhin. righrl) adherent film, which inhibits further corrosion. Exarnple: Cobaltchromium al-It l : ibrm a Cr.O3 oxide film, which passivates the surface. Base metals are less resistanti(-' corlosion. Base metal alloy advantages are principally found only in their strength andlo$ densit\',

T1pes of allol systemsi (classiJied on the basis ol the ry,pe of structue that .fbrms as thet'

t olid it.\')

. Solid solution alloys: the metals freeze without segregation of the individual con-stituents. )iote: Are generally used in dentistry because they have a very homogenous

stmcture an provide maximum strength.. Eutectic alloys: separatc into individual grains of the respective constituents. Ex-hibit complete liquid solubility but limited solid solubility. Example is the silver-cop-per system.

Remember: Nobfe metals /a/so called precious melalt are very resistant to corrosionand do not oxidize on casting. Noble systems for dental use are based on the noble or pre-

cious metal elements gold! silver, palladium, and platinum.

Whtch of the following is NOT a correct match between the goldcast alloy component and its effect?

. Gold - decreases ductility and malleability

. Copper - hardens the alloy

. Silver - color modiffing

. Greater thar 20% gold or other noble metals

. Greater than 30%o gold or other noble metals

. Greater than 50o% gold or other noble metals

. Greater than 75o% gold or other noble metals

Coplright O 20ll-2012 - Denral Decls

Cop)right O 20ll-2012 - Denral Decks

*** Gold actually increases ductility and malleability. It also increases resistance to tar-

nish and corrosion.

Effects ofthe Various Constituents on Gold Crsting Alloy

Compound Maior f,ffect on Gold Casting Alloy

Gold (Au) Increases resistance to tarnish and corrosion; increases ductiljly and malleability

Coppe. (Cu) Increascs hardness

Sil,ver (Ae) Main purposc is to modify the orange color ofcoppert reduccs melting t€mperalure;increases duciility and malleability

Platinum (Pt) Raises melting temperaturet increases tcnsilc slrength; decreases the coelfi€ient oflhermalexDansion: reduces tamish and corrosion

Palladium (Pd) Raises melting temperature; increases hardness: acls to absorb bydrogen gas which can

cause porosities in lhc casling; prevents tamish and corrosion; has a very strong whileningeflecl on gold alloys even when used at a low concenlralion (i.e., 5 wt%)

Ztnc (Zn) Acts as an oxygen scavenger and prevenls oxidation oflhe olher melals during the manufac-luring process; increases fluidity and decreases surface lensions, which increases castability

Four Types of High-Cold Alloys:

I . ADA type l: highest gold contcnt, 83o% noble metals. Intended for small inlays. Easily bum-ished due to high ductility.l. -f.DA t"ype ll: grcater than 787o noble metals. Intended for larger inlays and onlays.Can also

be bumished.l. ADA Ipe lll: greater than 750lo noble mctals. Inlcnded for onlays and crowns. Capable ofbeing heat-trcatcd.-+. -\D-{ t}pe lv: greater than 75% noble metals. Intended for bridges and removablc partial

dentures. ,,\lso capable ofbeing heat-treated. Hardest ofhigh-gold alloys.

T! pe Hardness Yield Strength (MPa) Percentage Elongation (q/o)

Soft <140 l8

II Medium 140-200 l8

It Hard 201-_t40 t2

IV Extra-Hard >340 t0

. fledium-gold alloys are 25-75% gold or other noble metals

. Lon-gold alloys are less than 257o gold or other noble metals

. Gold substitute alloys are alloys not containing gold. These alloys are called passive because

the]' fonn some type of protcctive layer (iurface oide Jihn) that oflers maximum resistancc to

corrosion. Examples include; Palladium-silver alloys and Cobalt-chromium alloys

Remember: The karat of a gold alloy is the numbcr of parts that are purc gold, on the basis of2.1 parts as a vnit (thus, 21 karat is 100 % gold, while l8 karat is 75% gold). Fineness is meas-

ured on the basis of parts of pure gold per 1,000 ( I ,000 jitteness is I00'% gold, *hile 500 .finenessis 50% gold). Pure gold is only used in the foil restoration.

The following statements describe an MOD gold cast onlay preparation. Whichwould you have to change in order to ensure the onlay will be successful?

. The mesial box has an ariopulpal line angle that is longer from facial to lingual thanthe axiogingival line angle

. From facial to lingual, the distal axiopulpal line angle is longer than the mesial axiop-ulpal line angle

. The mesial and distal axial walls converge

. The distal box has an axiopulpal line angle that is shofier from facial to lingual thanthe axiogingival line angle

68

Copyighr 20ll 20ll DentalDecks

OPERATIVE Gold

When preparing a Class V cavity preparation for dir€ct lilling gold,you should ensure you have all of the following EXCEPT one.

Which one is the EXCEPIIOM

. Rounded internal line and point angles

. Small retentive undercuts placed in the axio-occlusal and axio-gingival line angles

. \Iesial and distal walls that flare and meet the cavosurface at a 90o angle

. An axial wall that is convex and follows the extemal contour of the tooth .5mm intodentin

69

Copynghr L.l 201l'201: - Dental Decks

Remember:. When preparing teeth with short clinical crowns, the facial and lingual walls shouldhave a minimal gingival to occlusal divergence angle for maximum retention.. From facial to lingual, the axiopulpal line angle of an onlay preparation is longerthan the axiogingival line angle (l ll \rere not, the pt?paration would be undercut andtlrc onlay would not.seaf. For an MOD onlay prep, the axial walls must converge fromthe gingival walls to the pulpal wall (fbr the same reason, tlte onlqrvrould not seat iJthey diverged).

L The bevel (0.5 mm vidth) on the cavosurface margin permits closer adap-\ot*' tation of the gold margin because the thinner margin of gold overlying the

bevel is more ductile and is able to be bumished. The desirable metal angle at

the margins ofonlays is 40 degrees, except gingivally, where the metal angleshould be 30 degrees. Note: You can bumish a 30- to 40-degree gold margin,less than 30 degrees rnay be too thin and break, greater than 40 degrees maybe too thick and will not bumish.2. During cementation, the finishing /burnishing) ofthe margins ofa cast goldrestoration should be starled as soon as the restoration is well-seated into thepreparation.3. While preparing a tooth to receive an inlay or onlay. a gingival bevel is used

to remov€ unsupported enamel and to compensate for casting inaccura-cies. Gingival margin trimmers. carbide finishing burs, or fine, tapered dia-rronds are used to place this bevel.4. This gingival margin is always placed gingival to the contact area.

Class V cavity preparation for direct filling gold:

. The outline form is usually either trapezoidal (most popalay' or kidney-shaped. The

axiai wall is placed .5 mm into dentin (this u'ill make the occlusal u'all slightl,- deeper

tha the gingiral wqll because there is a thicker la.,-er ofenamel nnking up the occlu'

-sc/ rla//,). The mesial and distal walls are placed at the line angles ofthe tooth.

*** Remember: For any Class V prep (whether.fbr amalgam. composite or direct./illins gold). the outline form is determined by the extension ofthe carious lesion.

. The retention form is attained by shalp intemal line and point angles (a-rio-gingival

und utio-occlusal).

. The resistance form is provided by flat mesial and distal walls and a convex axials all rvhich parallels the external surface of the tooth.

\ote: The axial rvall is convex in a mesiodistal direction in order to conserve tooth struc-rure and minimize pulpal initation.

Important: The rubber dam is essential to prevent contamination of the gold with sal-

ila. A cervical clamp usually is necessary to retract the gingiva (#2 | 2 ivory clamp). Thehole that is to be punched in the rubber dam lor the tooth that is being restored should

be located facial to the nomal alignment with the adjacent teeth.

The purpose ofa sprue former is to crerte a prssagefor material to flow lnto the lnvestm€nt.

The sprue former is typicrlly attached to a thin portion ofthe crown.





70Cop)'right O 20ll-2012 - Denhl Decks

Dental wax patterns (ie., inlats, onlays, crowns) should beinvested as soon as possible after fabricating to minimize

chang€ in the shape caused by:

. Reduced flow

. Drying-out of the wax

. Relaxation of intemal stress

. Continued expansion ofthe wax

71

CopyightC 20ll-2012 Denral Decl!

The purpose of the sprue former or sprue pin, as it is usually called, is to provide aningate or sprue in the investment through which the molten alloy can reach the moldafter the wax has been eliminated.

The size of the sprue former depends to a considerable extent on the type and size ofthepaftem, the type ofthe casting machine to be used and the dimensions ofthe flask or ringin which the casting is to be made. Generally, however, for the average size pattem, sprue

formers smaller in diameter than approximately 1.5 mm are contraindicated. tla sprue is

too small, the molten metal freezes completely in this area first, and localized shrinkageporosity results. The general rule for sprue pin diameter when using a centrifugal type olcasting machine is that the diameter ofthe sprue pin should be equal to or greater thanthe thickest portion of the pattem.

..Ls a general rule, it is desirable to attach the sprxe at the point of greatest bulk in thepattem. There is less chance ofdistortion upon attaching the sprue, and the molten metalis more apt to remain liquid in this area until the entire mold is filled. The direction ofthesprue former is also impoftant. It should never be attached at a right angle to a broad flatsurface of the mold. The entering hot metal impinges the mold surface at this point tocause turbulenc€ ofthe metal, which, in tum, creates a shrinlage void or suck-back poros-

ir). \\'hen the same pattern is sprued at an angle of 45o to the proximal wall, a satisfac-tory casting is obtained.

The three types ofinlay waxes differ in terms of melting point and flow:

1. Type A: hard or low-flow wax that is rarely used except in some indirect technique2. Tvpe B: medium-flow wax that is used in some direct techniques.3. Type C: soft or high-flow wax that is used in indirect techniques for the construc-tion of inlays, onlays, and full crowns.

fhe essential ingredients ofa successlul inlay wa"r are paraffin wax, gum dammar and car-

nauba l ax with some coloring material. Paraffin wax is generally the main ingredient,usualll in a concentration of40-60%. Gum dammar is added to the paraffin to improverhe smoothness in the molding. It also increases the toughness of the wax. Carnaubawar is quite hard and tends to decrease the flow ofa wax.

\ote: Ho\r'ever the pattern is prepared, it should be an accurate reproduction ofthe miss-ing tooth structure. The casting can be no more accurate than the wax pattem. The waxpattem should be invested as soon as possible after fabrication in order to minimizechanges in shaped caused by relaxation ofthe intemal stresses in the war.

The refractory filler component ofgypsum bonded investmentsprovides thermal expansion.

The thermal expansion is necessary to compensate for thealloy solidilication shrinkage.

. The first statement is true; the second statement is ialse




72

Coplri8hr C 201 1,2012 - Dental Decks

All of the foltowing are indications for a cast gold onlayEXCEPT one.Which one is the -EXCEI{IIOM

. Restoration oflarge lesions

. Restoration of ideal occlusion in cases ofdrifting, hypo and hyper eruption, etc.

. Restoration of optimum contour and proximal contact

. Restoration ofbrittle teeth (endodontically treated)

. Restoration of a tooth as an abutment for removable prosthesis, creating ideal guidingplanes, rest seats ard undercuts

. Restoration ofteeth to meet patient preference for gold

. Restoration of a tooth with minimal femrle, where a full coverage crown would not have

73

Coplrighr O 2011"2012, Denral Decks

enough retention

Main components ofgypsum bonded investments:

L A refractory filler rvhich is a form ofsilicon dioxide (Si Of, such as quanz or cristo-balite comprises 60 to 65% of the investment. These two compounds have differentcrystal structures and therefore have different thermal expansion coefficients.Key point: This refractory filler regulates and provides the thermal expansion for thelnveStment.

2. The binder fivhich i,s a g,-psum mqtrLx oj a -calcium

hemihvdrate) comprises 30to 35% ofthe investment. This is the material that hardens after being mixed with theIiquid and thus holds the investment together (qdds strength). The actual or effectivesetting expansion is dependent upon the g)?sum content plus the water/powder ratio.Kep'point: Using a thinner mix 6i,rlc h contains morc waler, of a gypsum-bonded in-vestment will decrease the setting expansion, increase the setting time, increase the

porosity ofthe set material, and ultimately weaken the set material.,l. \lodifiers are added to modify various physical properties ofthe investment. These

rrodifiers include magnesium oxide, sodium chloride, boric acid, graphite, or potass-

siurn sulfate.

Dental investments serve three important functions:1. -\ detailed reproduction ofanatomical form.l. Enough strength to withstand the heat of burnout and the actual casting of the

molten metal.l. Compensation expansion equal to the alloy solidification shrinkage.

Important: Ifa tooth is not a candidatc fbr a full coverage crown, it is not a candidate for an onlay. Atooth that does not have a minimum of 1.5 mm of femtle effect will nccd a core build up. crown length-

cning, or both.

A fenule effect is defined as the envclopmcnt ofthc tooth stmcture by a crown. According to recent stud-

ies. L 5 mm oftooth structure is sufficient to ensure the tmnsmission of the forces of mastication to bothrhe post and the tooth. A tooth that is fractured at the gumljne offcrs no form olresistance to transversal

torces. The post must take on the entire load and it is inevitablc that ccmentation fails.

Requiremcnts for a good ferrule efLct:. Lr I mm ofbuccal and lingual subgingival tooth srucftre. . nm uf r.\){h lhrckne:. after aJequ:rtc preparatiun. J mm ofsuprabony tooth structure

Tle main adrantage ofthc onlay is that it can permanently restore and reinforce a tooth by a con-

sen ati\ e technique. r\lthough conscrvation oftooth structure is desirable, such action is oliset by a lack

oi rcrcnrion. It has been shown that conservative onlays have inferior retcntion comparcd to full crowns.

Thii is duc to the cro$n's greater axial surface area.

l. Retentive features: parallelism ofvertical surface /lr,r:idl 11411t is the primary retentive

561js feature ofan onlay preparation. Sharp point and line angles add to retention.

2. Auxiliary retentive fcatures include a box or a groove. Thcse features may bc indicated

where inadequate surface atea ofvertical walls is present. A box olfers a greater increase

in surface area, thus greater retention than a groove, but is also more costly in terms oflost tooth sfructure.

3. Thc location ofthe gingivalrnargin in the preparation ofproximal surfaces is influenced

by the amount of retention required, the need to ertend gingivally to clear the contactarea and convenience form.

On delivery ofyour lirst ever crown, you notice that the margins areopen when you rttempt to seat the crown in the mouth. Which of

the following should you check ffrst?

. The occlusal contacts

. The proximal contacts

. For a void on the crown's interior

. For a nodule on the crown's interior

74Cop)'right C 201 l-2012 - Dental Decks

. They are vacuum investing

. They are hand investing

. Nothing in particular, hand and vacuum investing are the same thing

. None ofthe above

Coptrighr O 20li 2012, Denral Decks

Ifa casting lails to completely seat on a prepared tooth, one should first check for resid-ual temporary cement or other debris on the prepared tooth. Once all the temporary ce-ment and other debris are removed, the first st€p in fitting the casting in the mouth is toadjust the proximal contact areas.

Very important points:

1. When seating a casting, the initial interferences are usually the proximal contacts.Complete seating of the restoration can be verified by an x-ray and a sharp explorerused at the gold tooth margin.2. When seating cast gold restorations, the occlusion of the restoration should be tothe same degree that teeth contact in that quadrant and on the opposite side (u.se shintstock to check occhtsion).3. InitiallS ifa cast restoration is in hyperocclusion, the patient will complain ofcoldsensitivity and pressure in the tooth. If the restoration is not adjusted, the toothsill beconre very cold sensitive, show signs of mobility and there might bercces:ion ofthe lacial gingival tissue.

These defects. or nodules, are caused by the collection of air bubbles during the invest-ing The best way to help eliminate these defects is to subject the water-tnvestment mtx-rure to a vacuum during the investing procedure in order to remove the air bubbles.

The porosity ofthe investment is definitely reduced by vacuum investing, presumably be-cause ofthe increased density obtained. As a result, the texture ofthe suface ofthe cast-ins js somewhat smoother, with better reproduction ol fine detail. The compressivestrength ofthe investment is increased slightly by the vacuum investment (the invest-nient \t Ill not /iacture as eas!-).

\ot all of the air is removed by the vacuum treatment. The amount removed dependsjLrme\\ ltat upon the consistency of the mix. The more yiscous the mix, the more airbubbles remain in the investment. However, a thick mix is usually necessary because ofthe desired shrinkage compensation and because of the poor surface texture that is ob-tarned Nith a thin tlix.

You are preparing tooth #19 for a MODB gold onlay and tooth #18 for a MODBamalgam restoration. Which of the followlng TWO statements correctly

describe the dilference in your preparations ofthe functional cusp?

. You will need 2.5 to 3 mm ofreduction for gold

. You will need 2.5 to 3 mm ofreduction for amalgam

. You will need 1.5 mm ofreduction for gold

. You will need 1.5 mm ofreduction for amalgam

Coplrighr O 2011,2012, Denial Decks

The modifred pen gnsp is the most common instrum€nt grasp in dentistry;this is because it allows for the greatest intricacy tnd delicacy oftouch.

. Both the statement and tlle reason are correct and related



. The statement is NOT corect, but the reason is correct


77Copright O 201 I 2012 - Dentd Decks

Remember:

Working cusps Ailnctional cltsps)

. Maxillary teeth: lingual

. Mandibular teeth: buccal

Non-working crsps h o n -.s r rp po rr i n g)

. Maxillary teeth: buccal

. Mandibular teeth: lingual

Minimal Occlusd Reduction

Cusp Amalgam Cast Gold Metal-Ceramic

Working 2.5-3.0 mm 1.5 mm 1.5-2.0 mm

Non-working 2.0 mm 1.0 mm 1.5-2.0 mm

L For non-working cusps the minimal reduction for amalgam is 2.0 mm\otes rvhile forming a flattened surface (this provicles resistance .fbrm) and for cast

.. gold it is 1.0 mm.2. For m€tal-ceramic restorations: facial and lingual reduction 1.5 mm3. The difference between tooth preparation for a metal-ceramic restorationand a porcelain jacket crown is mostly related to the configuration of the fin-ishing line or margin chamfer or bevel for metal-ceramic restorations and

a butt joint for porcelain jacket crowns.

Important: The most effective means for verifuing adequate occlusal clearance is a waxbite chew-in.

With this grasp the middle finger, index finger, and thumb all rest on the handle close tothe junction of the handle and the shank. The middle finger rests on the shank and therhumb and index finger are opposite each other on the handle. (See photo below)

The inlerted pen grasp is very seldom used, however, sometimes it is used lor cavitypreps utilizing the lingual approach on anterior teeth.

The palrn and thumb grasp is the most powerful grasp and is most effectively used on

the maxillary arch. It is similar to the grasp used for holding a knife while paring the skinfrom an apple.

The modified palm and thumb grasp allows much ofthe power of the palm and thumbgrasp but also permits more delicate control. It works best when you can rest the thumbon the tooth being restored or on the adjacent tooth. It also works best on the maxillaryarch.

When sttempting to remove a hard brlttle material, llkesmNlgtm, you would pref€r a bur with a:

. Zero rake angle

. Positive rake angle

. Negative rake angle

78Copyrigh O 201!-2012 - Denbl Decks

OPERATTVE

. Edge, rake, clearance

. Rake, edge, clearance

. Clearance, rake, edge

79Cop)righr €,201l-2012 - Denhl Decks

Th€ _the

angle is the angle formed betweenface and the face.

*+* Rcm€mber: The rake angle = the anglc made benveen the line connecting the edge oflhe blade to the axis

ofthe bur and the rake face. This angle may be positive or ncgativc.

Generally speakrng, soft materials such as acrylics are cut mosl effectively with positive rake angie burs;whereas cxtrcmcly hard and brittle materials /suth as analgan) ate best cul with n€g|tive rake angle burs.A rakc an€llc is said to bc ncgativc whcn the rakc facc is ahead olthc radi$ (/ionl the (:utitlg edge to the atisofthebut).A^egllverakeanglcminimizesfi?cturesofthecuttingedgethathelps!oincreasetheburlife.ln-creasing the edge angle reinforces the cutting edge ofthe bur and reduccs the likelihood ofrhe blade to fiac-ture.

Carbide burs used for cuiting looth structure gcnerally havc slight negativ€ rakc anglcs and edge angles ofapproximately 90 . To be most effective, these burs should be rotating rapidly befor€ contircting the tooth.

The clesrance angle is also anothcr importanr factor in bllrde design. The clearancc anglc senes io climinatcfriction ben'een the clearance face and the new tooth structure exposed by lhe curting edgc. The gresfer theclearance angle, the less friction.

srlrdclrnl C\ . Rob.Fin T\l.lieynran. HO.

Bur blad€ design. Schemalic cross sec-

tion riewcd lionr shank end of head loshow rltkc angle, €dge angle. and clear-

. \11 ofthe tbllo*ing influence tooth temperature during a culting procedurc:

' Djameler and sharpness ofthc bur. Bur looth contact time. T)'pe of coolan! used lwaler is best. air itt^ dehrdrate lhe loolh or cduse the loolh to he hr-pcrsensitiw h) dravin!< odontobhsts into th( dentinal tubulcs). Amounr offorcc applied to the bur

Each bur blade has two sides:

l. The rake face (to\\,ard the direction o./ (Lttting). The rake face is that surface /sidel of the blade. which makes contact with the

tooth surlace and faces in the direction ofbur rotation.

2. The clearance face. The clearance fac€ is that surface (.r/del ofthe blade that faces away from the di-rection of bur rotation.

Each bur blade has three important angles:

1. The rake angle. The rake angle is the angle made between the line connecting the edge ofthe blade

to the axis of the bur and the rake face. This angle may be positive or negative.

L The edge angle. The edg€ angle is the angle formed betrveen the rake face and clearance face.

3.The clearance angle. The clearanc€ angle is the angle formed between the clearance face and a tangent

to the path of rotation.

)iote: For most effective cutting, a bur should be rotating rapidly before contacting the

tood].

What is the blNde width of r cutting instrumentwith the following formula: 10 - 85 - 8 -14

.10mm

. 1.0 mm

. 0.85 mm

. 0.80 mm

80Copyr'gltr e 20ll 201? Denral Decks

,PERATfVE

Chisels are used primarily to cut enamel.

Ilatchets are primarily used to cut dentin.





81

Cop),right C 201 I -2012 - Detual Deks

Cutting instruments have formulas describing the dimensions and angles olthe working end:

. The first number indicates the width of th€ blade in tenths of a millimeter I 0 mm

(t 0 x . l) for the example on the front of the card.. The second number indicates the primary cutting edge angle in centigrades 85 for

the example on the front ofthe card.. The third number indicates the blade length in millimeters 8 mm for the example on

the front ofthe card.. The fourth number indicates the blad€ angl€ in centigrades l4 for the example on the

front ofthe card.

Three major parts ofa hand-cutting instrument:

1. The handle is that part ofthe instrument held or gasped during activation ofthe blade

Types: single ended or double ended.

2. The shank serves to connect the blade to the handle. Types: straight or angled (rror-

angle, bi<ngle, or triple-angle), meaning one, two or three angles in the shank'

\oie: Proper balance ofthe instrument is accomplished by angling the shank ofthe instru-

menr so that the cutting edge ofthe blade is within 2 mm ofthe long axis ofthe handle. In

order to keep the blade within 2 mm ofthe long axis, the shank ofthe instrument is angled'

i. The blade is the working end ofthe instrument and is connected to the handle by the

shank. Blades are of many designs and sizes, depending on the function they are to per-

tbrm.*** The nib is not a major part ofa hand cutting instrument lt is the working end of a non-

cutting instrumen t (i.e., a bttrnislrcr condenser' elc./. The end of the nib, or working sur-

tace. is known as the face. Note; It corresponds to the blade ofa hand cutting instrument'

*** Hatchets are also primarily used to cut enamel

Chisels may be grouped as:

l. Straight, slightly curved, or bin-angl€: primarily used for planing or cleavingenamel. Characterized by a blade that terminates in a cutting edge formed by a one

sided bevel.

2. Enamel hatchets: are chisel-bladed instruments with the cutting edge in the plane

ofthe handle. They come paired l€ft and right.

3. Gingival margin trimmers: are similar in design to the enamel hatchet except

it has a curved blade and an angled cutting edge. They are primarily used for bevel-ing gingival margins. Among other uses for these instruments is the rounding orbeveling ofthe axiopulpal line angle of Class II preparations (very important).

. Hoes

. Angle formers

. Ordinary hatchet

. Spoons

. Spoon excavator, enamel hatchet

. Spoon excavator, straight chisel

. Cingival margin trimrner, enamel hatchet

. Gingival margin trimmer, straight chisel

Sharpening line angles and convenience points for gold foil preps

Preparing retentiv€ ar€as on antedor teeth

Remove carious dentin and sometimes carve amalgam

Class III and V direct gold preps

a2

Coplright C 201l'?012 DentalDecks

83

Coplright O 201 I -20 l2 - Dental Dects

You set down the hrnd piece after preparing a Chss II rmalgamon tooth ti4. Your assistant hands vou a so you

socan remove the last bit of caries. and then theyou can plane the facial and lingual wllls ofthe prep.

There are four subdivisions of excavators:

l. The hoe excavator: has the cutting edge ofthe blade perpendicular to the axis ofthe handle. It is commonly used in Class III and V preps for direct gold.

2. The angfe former: has the cutting edge at an angle (other than 90") to the blade.It is used for sharpening line angles and is especially useful to form conveniencepoints for gold foil preps.

3. An ordinary hatchet excavator: has the cutting edge of the blade directed in thesame plane of the handle and is bibeveled. Used primarily on anterior teeth forpreparing retentiv€ areas.

.1. A spoon excavator: has a curved blade with a rounded cutting edge. It is used to re-move carious dentin and sometimes to carve amalgam,\ote: These can be sharpened with handpiece stones.

*** The enamel hatchet is the only instrument that will allow the dentist to have properaccess to the margins and that will impart the proper cavosurface angle to the margins.

Spoon excavators are used for removing caries and cawing amalgam or direct wax pat-

tems. The blades are slightly cuwed and the cutting edges are either circular or claw-like.The circular edge is known as a discoid, whereas the clawlike blade is temed a cleoid.

The number of bevels that make up the cutting edge can classify hand cutting instru-ments. For €xample, enamel hatchets and chisels have single bevels, whereas ordinary

hatchets (fbr exqmple excavators) have two bevels and are called bibeveled.

Dental hand cutting instruments are angled to:. Provide better manipulative control. Produce a better distribution of force. Increa-se elficiency. Lsl3blish proper balance u hen in use

Instruments used to trim restorativ€ materials rather than for cufting tooth structure:. Knives (lirrlslrirg, amalgam, or gold): nsed for trimming excess filling material on

the facial and lingual. Files: also used to trim excess filling material, especially at the gingival margins. Discoid-cleoid: used principally lor carving occlusal anatomy in unset amalgam

restorations

To polish a restoration you wlll likely use a bur with less cutting blades.This is because less cutting blad$ cut more efficiently.






a4Copfight O 20l l-2012 - Dertal Decks

There are several tlpes ofbleaching products tvailable for use at home'which can either be dispensed by a dentist or purchased over-the-counter.Curren$, only dentist-dispensed home-us€ tray-applied

gels carry the ADA S€al.

. 3 0oi' carbamide peroxide

. 159.'6 hydrogen peroxide

. 20% hydrogen peroxide

. l0% carbamide peroxide

85

coplri8ht O 20ll 2012 Dental Decks

*** Important: Thc greater lhc numbcr ofculting bladcs on a bur rcsults in less effici€nt cutting but a smoothersuft^ce lpolishing hrs arc ol lhi\ l|pe). Alcsser numbcr of bladcs on a bur rcsulrs in more efficient cuitine but arougher sur{ace. Crosscut t'issurc burs al high spccd or low spccd arc ofthis r}pc.

Parts ofburs:I. Shank: thc part lhat fits into handpiccc. Thc thrcc most common tlpcs arc straight. latch-r]"pc anglc and tiict-ron-gflp anglc.2. Ncck: {hc irtcnncdiatc portion ofa bur that connccls thc hcad to thc shank. lrs main lunction is to transmit ro!tational and translational forccs to thc hcad.

3. Head: thc $'orking pan of $c bur the cutting edges ofwhich pcrfonn thc dcsircd shaping of tootb structure.

Types of burs:. Sttel hts&t Dtostlr /t)t linishing prorcdure\). C^rbidc (used /ot, Larit| prepardtio : pe|orn best at high speeh)

Shapes of burs: rcfcrs to thc contour ofthc hcad. Thc basic hcad shapcs arc round, inveried conc, pcar straight fis-iurc and lapcrcd fissurc. Note: Within a givcn scrics ofburs, thc smaller numbers rcprcscnt small burs; thc largcrnumbers, largc burs.

Recent modifications in bur desicn:. Raduced use ofcrosscut burs non-crosscut burs arc now popular. ( -r orJr ti"'ur.' bur. r^ rth cxt.nd.d hc.r.l'

'R.rLnding ofihc sharp tip comcrs

Th. rotational speed ofan instrumcnt is mcasurcd in rcvolutions pcr minutc /?rr. Thcrc arc 3 spccd rangcs: slow\.:t,. i:na)1tpDt) intcnnctliarc (1:.000 to 200,000 rpnr, andhigh (ahore 200,A00 ryn, spcc.J.Tbc most uscfulin-

::r.r:..nti i.c rotatcd at either low o. high speed. Thc crucial lactor fbr somc purporcs is thc surfacc spccd ofthc in-:rrl1r.rr- rhc \clocit) a1 which ihc cdgcs oflhc cultilg inslrumcnt pass across lhe surlhcc bcing €ut. This is

.rr.rnion.rl Io borh thc rolalional speed and Ihc diamctcr oflhc inslrumcnl, with largc instrumcnts having highcr sur-:=.J .:.Jds 3t 3n] gi\en ratc ofrotation.

Di.mond abrasile instrumentsi involvc abrirsivc rathcr thar bladc cutting. Thcsc instrumcnts arc bascd on small..:r:.:u :r prnrclcs ofhard substanccs hcld in a matrix ofsoficr nratcrial. Diamonds consist ofthrcc parts: a mctal blank,::::1Lr\\dcrcd diamond abrasive, and a mctallic bonding matcrial fiat holds thc diamond powdcronto thc blank. Thc:::rnk in many $ays rcscmblcs a bur \r,ithoul bladcs. Il has $c samc csscnlial parts: hc!d, ncck. and shank. Thc clin-r.:: p.rlbnnancc ofdiamonds depends on thc sizc. spacing. unifonnit!, cxposurc. and bonding ofthc diamond par-t:.1.i Di.rmond particlc sizc is commonly catcgorizcd as coarsc. mcdium. llnc. and vcry linc.

TrIo methods of bleaching:

L "In office": most use a lightactivated solution of 35% peroxide in 4- l0 minutecr cles. Tbis procedure is called "chairside bleaching" and may require more thanone ofllce visit. Each visit may take from 30 minutes to one hour. Note: Lasers havebeen used during tooth whitening procedures to enhance the action of the whiteninga,qenl.

:. *-\t home": the active ingredient contained in all of the at home tooth whiteners* hich have eamed the ADA's seal, and the compound which has been evaluated inrhc \ ast majority of at home bleaching studies, is carbamide peroxide at a concen-tration of 109/o. The active ingredient found in most over-the-counter at home bleach-ins products is not carbamide peroxide but instead hydrogen peroxide.

\ote: Bleachins can affect the color ofdentin and enamel. Extrinsic stains respond best:o r ital beaching. Response is best with yellow stain followed by brown and orange. The\\ orsl response is from gray starns (tetracycline staining).

Other u ar r to lighten vilal teeth:. Direct composites: useful for tetracycline staining. Laboratory-fabricated porcelain veneers: useful when the shape, size and arrange-ment ofteeth are esthetically unacceptable. Full-coverage crowns fnosl invqsive and costly): may be all-ceramic or porcelainfused to metal

Which one is the EXCEPZOM

. Operator zone

. Assistant zone

. Transfer zone

. Patient zone

. Static zone

86Coplriehr O 201!-2012 - Dental Decks

Xerostomia is the most common adverse sid€ effect of medicttions.

This is attributed to the cholinergic effects ofmany medications.





87Coptaighr O 20ll-201? 'Denral Decl(!

The operator and the assistant should concentrate on positioning themselves in work cir-cles. The dentist's work circle should allow easy and unobstructed access to the patient'smouth. The assistant's work circle should include all instruments and supplies needed forthe intended operation. also allowing access to the transfer zone to bring the necessaryitems to the dentist. When viewed from above with the patient's head in the l2:00 o'clockposrtion, the right handed dentist will operate in an area from 8:00 to I l:00 o'clock. Thisarea is the operator's zone. Nothing should be in this area that would interfere with thefree movement ofthe dentist. The area from I l:00 to 2:00 o'clock is called the static zone.This area is reserved for the mobile cabinet and nitrous oxide apparatus. The area fronl2:00 to 5:00 o'clock is the assistant's zone. Although the assistant will not move as muchas the dentist, nothing should be positioned in this area that would hamper the assistant's

free access to the oral cavity, mobile cabinet and dental unit. The area form 5:00 to 8:00

o'clock is the transfer zone. This area is reserved for the transfer of instruments, medica-

ments. and supplies to the dentist. Also, the dental unit should be positioned within this

arc.

Other considerations for an efficient four-handed dental deliv€ry system:. Concerning the transfer of instruments: the hand instrument to be transfered tothe dentist is held by the assistant between the thumb and the forefinger.. Equipment selection: whatever equipment is used it should be compatible for the

dentist and assistant. The position ofthe chairside assistant should be high€r than thedentist.

\ote: \'enting the suction exhaust to the building exterior can reduce health hazards to the

orlice stllf from the central suclion unit.

*** This is attributed to the anticholinergic effects ofmany medicatrons.

Other etiologic factors for xerostomia include:. Radiation therapy to head and neck. Salivary gland surgery. -{utoimmune disorders such HIV infections, systemic lupus erythematosus, rheuma-

toid anhritis, and SjOgren's Syndrome. Endocrine disorders such as diabetes and hyperthvroidism

Treatment lor xerostomia:. Consider stopping offending medication. Comrnercial saliva substitute. Fluoride Supplementation. Scrupulous dental care is essential

Antichofinergic drugs (u,iici block receptor sites./or acery*lcholine) decrease salivarytlos and respiratory secretions during surgery Examples include: atropine, scopolamine,methantheline, and propantheline bromide.

Don't forget: Local anesthetics aid in reducing the flow ofsaliva during operative pro-cedures by reducing sensitivity and anxiety during tooth preparation.

Remember: Cholinergic agents actually increase secretions, a cholinesterase inhibitorwould also increase secretions because it would reduce the metabolism of acetvlcholine.

When restoring a Class II or Class III lesion it is inportant to crerte properlyshaped embrasures for all of the following reasons -EXCEPI one.

Which one is the EXCEPIIOM

. Create a spillway for food during mastication

. Make the teeth self-cleansing

. Protect the gingival tissue, while also allowing stimulation of it

. Provide arch stability

88Cop)rig]rr @ 20ll-2012 - Denlal Decks

OPERATIVE

Atooth was restored 3 months ago by a new associate of yours. The patient is

complaining of mobility and thermal sensitivity, You trke a periapicrlradiograph. You could see all ofthe following in that radiograph to

. conlirm your suspicions, EXCEPI one. Which one is the EXCEPTION'!

. H)?ercementosis

. Root resorption

. Periodontal pockets

. Alteration ofthe lamina dura

. Widening ofthe periodontal ligament space

89coplriSht o 20l l-2012 - Dental Decfts

*** As long as a contact is present, regardless of proper embrasure contour. you willmaintain arch stability

There are four embrasures for ev€ry contact area:| . Buccal brfitcial)2. Lingual (usually larger than the Jacial)3. Occfusal (or incisal)4. Cervical (or gingival)

*** Note: In posterior teeth, the gingival tissue fills this embrasure. Normally it is

"col" shaped when viewed in a faciolingual cross section.

Functions of embrasures:I . N4ake a spillway lor food during masticationl. \lake the leeth more self-cleansing

-1. Protect the gingival tissue from undue frictional trauma, but at the same time pro-r ide the proper degree of stimulation to the tissue.

.\ contact area is an area in which the mesial and distal surfaces ofadjacent teeth in the

sarne arch make contact. A contact point is a point at which teeth ofthe opposing arches

meet or touch in occlusion or closure.

The height ofcontour refers to the thickest portion or point ofgreatest circumference ofrhe tooth when viewed form the incisal or occlusal surface. Its functions include formingthe contact area on the mesial and distal surfaces and protecting the gingiva surroundingrhe tooth.

*"* YoLr should have suspected that the restoration was high, based n.rainly on the mobilityl'actor. Occlusal trauma can still cause periodontal pocketing; however, that cannot be

seen on a radiograph.

Some common clinical signs of trauma from occlusion include:. Increased tooth mobility is the most common clinical sign. Themral sensitivity (cold)'. prestmably, this sensitivity is due to venous hyperemia ofthe toodr. -\nrition of the enamel. Recession ofthe facial gingival tissue

Remember: Whenever a restoration is done, the occlusion has to be right. The degree ofcontact on the restoration should be to the same degree that teeth contact in that quadrant

and on the opposite site.

\ote: The radiograph ofchoice for evaluating root surfaces, suppofiing bone and the pe-

riodontal liganent is the periapical film.

Z\When restoring the embrasures of posterior teeth th€ contect

should be formed stightly buccal from center.

This will create a wider facial embrasure.





90Coptright @ 201 I 2012, Dmial Decks

. Lingering pain over 15 seconds

. Negative electric pulp test

. Frank apical radiolucency

. Percussion sensitivity

91

Coprighr O 201 l'2012 - Dental Decks

ERATIVE

*** This will create a wider lingual embrasure and a nanow facial embrasure.

The primary purpose ofthe proximal contact relationships between adjacent teeth in thedental arches is twofold. This relationship serves both to stabilize the dental arches by thecombined support of the individual teeth and to pr€vent the impingen.rent offood mate-rial on interseptal tissues between the teeth

The proximal contact area functions to:L Support neighboring teeth (stabili:es the dental atch)2. Prevent food particles frour entering the interproximal areas

3. Protect the periodontiun.r.1. Form embrasures

The loss of proxirnal contact between teeth nray result in periodontal disease, malocclu-sion. food impaction, or drifting ofteeth.

Remember: When viewed from the facial, all premolars have their contacts at the iunc-tion of the occlusal and middle third. From this same view. molars have a proximalcontact located in the middle third. Fron.r the occlusal view, all posterior teeth have con-

tacrs. r hich are located slightly buccal of the middle third (mesial and distql). This cre-

ates a rvide lingual and a nanow facial embrasure.

*** A tooth with percussion sensitivity could need caries control with a sedative tempo-

rary filling. lt could also need occlusal adjustment (vhich can cause reversible pulpitis os

Pulpal necrosis is the death of the pulp. A tooth aff'ected with a necrotic pulp may have

no painful symptoms. It may appear discolored. The EPT /electric pulp tester) will be ofr alue because there will be no response at any current level. The tooth sometimes re-

spexds to heat, but will not respond to cold. Treahnent is root canal or extraction.

\ote: Acute apical periodontitis is characterized by pain, which is commonly triggered

br chen ing or percussion. AAP (acate apical periodontitis) alone is not indicative ofanirrer ersible pulpitis. It is indicative that the apical tissues are irritated, which may be as-

sociated \\ ith an othenvise vital pulp rvith a potentially reversible pulpitis. In the absence

oircue pain. a negative EPT test or a frank apical radiolucency. a carious tooth with sen-

sirir itr to percussion may respond to caries control (tentporary flling). If it doesn't re-

-.pond to a sedative filling, root canal is indicated.

Pulpal Diagnosis Cold Response Treatment

Normal Not delayed or very short linger None needed

Reversible pulpltis Lingers less than l0-15 seconds Remove causative agent

Irreversitrle pulpitis Lingers longer than 15 seconds RCT or extractlon

Necrotic pulp No response RCT or extraction

On the lirst d|y in your solo privNte practice you have r pulp exposure.All of the following are favorable factors in avoiding root canal

treaturcnt EXCEPI one. Which one is the EXCEPUOM

. It is a mechanical exposure of lmm

. The tooth had never been symptomatic

. The pulp tissue appears pink

. The hemorrhage is slight

. It is a pinpoint carious exposure

92Copyrigh O 201!-2012 - Dental Decks

The ideal amount of time lrom placing an indirect pulp cap untilrcopening the tooth to remove the remaining decay is:

.7 - l0 days

.2-3weeks

. I month

.3-4months

. I year

. Never, r.rnless the tooth becomes symptomatic there is no need for further treatment

CoplriSht O 201 1,201: - Dental D€cks

Direct pulp capping involves the prompt application ofa setting calcium hy&oxide cementto a "pinpoint" /ess thq l mm h diameref, well isoJated traumatic pulpal exposure. This pro-cedure may be expected. in most instances, to stimulate the fbmation ofa reparative "dentinbridge" over the exposure site and to preserye the underlying pulpal tissue in a healthy con-dition.Favorable factors for direct pulp capping include: the visual evidence of uninflamed /plnt)pulp tissue, the absence ofcopious hemonhage through the exposure, no previous symptomsofpulpitis, a small non-carious exposure /a mechqnicol pulp exposure). and a clean cavityuncontaminated with saliva.

The lollowing adverse responses may occur following direct pulp capping procedures:. Physical or microbial insult to the pulp may result in pemistent inflammatory changes,rvhich may culminate in partial or complete pulpal necrosis.. Regulation of the mineralization processes involved in dentin bridge fonnation may be

corne deranged, resulting in extensive calcification and obliteration ofthe pulp canal space

bl mineralized tissue.. \'er) rarely, the differentiation ofodontoclasts may be induced u,ith the development of-intemal resorptive lesions.

L Direct pulp capping is especially successful in immature te€th.\otr. 2.The failure of this direct pulp capping procedure u'ould be indicated by symp-

loms of pulpitis at any tine or the lack of a vital response after several weeks ormonths.3. Direct pulp capping should not be attempted on teeth with a history of pain,

sensitivity to percussion or periapical radiolucencies (root canal therapl, may be in-dicated).

Trvo types of pulp capping procedures:

L Indirect pulp cap: a calcium hydroxide base is placed on a thin layer of questionable dentin remaining over the pulp. It is performed when a carious exposure is antic-ipated. After a 3 - 4 month waiting period, the tooth is reopened and the remaining decayis rerroved. During the waiting period, it is hoped that there rvill be secondary dentinformation, allowing complete removal ofthe decay without pulp exposure.

Classic example: A radiograph ofa first molar shows gross decay that may involvea hom of the dental pulp. The ideal treatment would be to do an indirect pulp cap andplace a sedative filling(IRM).If tooth remains asymptomatic, in 3 - 4 months you can

re-enter the toodr and remove all decay with subsequent placement ofa permanent filling. \ote: Ifthis patient had pain in the tooth laggravated h.t'heat and tender to per-(ussiotl). and excavation of the carious lesion revealed exposure of the pulp horn\rithout evidence of vital tissue, the emergency treatment pending eventual rootcanal therapy is to place a small cotton pellet dampened with eugenol over the expo-sure and seal the cavity with a temporary material (1R M).

Rationale for indirect pulp capping there are three dentinal layers in a carious lesion:

l A necrotic, soft, brown dentin outer layeq teeming with bacteria

2. A firmeq discolored dentin layer with fewer bacteria

3. A hard, discolored dentin deep layer with a minimal amount ofbacteria invasion

2. Direct pulp cap: a calcium hydroxide base is placed directly on a pulpal exposure,

A patient walks into your ollice for an em€rgency visit. He asks ther€ceptionist for a cold glass ofwater and sesms to be tilting hishead sideways as to hold the wat€r on one side of his mouth.

. Immediately, you suspect which reason for his visit?

. Pulpal necrosis

. Pulpal hyperernia

. Irreversible pulpitis

. Acute apical periodontitis

94

Copyright C 201 l-201: - Dertal Decks

A cold test reveals N lingedng pain. You ask the patient to raise theirhand until the pain subsides. The patient raises their hand for

about 8 seconds. What does this data suggest?

. Pulpal necrosis

. Ineversible pulpitis

. Pulpal hyperemia

. Acute apical periodontitis

95Coplrighr O 20l l-2012, Dertal Decks

OPERATTVE

Irrevcrsibfe pufpitis honetimes called qcute pulpitis) rs an acute inflammation ofthe dentalpulp characterized by intemittent spasms of pain, which become continuous. In the earlystages, it may appear as a very severe hyperemia. As the condition continues, the pain may bedescribed as a gnawirg or dull throbbing. The pain is generally increased by heat and relievedby cold. The treatment accepted by most clinicians is pulp removal (t'oot canal therapl).Note: The tooth is usLrally percu.siun positive.

At first, the pain is initiated and sustained only by the stimulus f/Ir is reversible pulpitis).Later, as the pulpal swelling spreads from the initial area ofdamage or initation to the rest ofthe pulpal tissue in the chamber, the pain initiated by the stimulus becomes more prolongedrthi.s is iteversible pahtll.r/. Ifenough pulpal tissue becomes damaged, the pain may initiateor persist \\'iihout any stimulus at all. At the same time. the degenerative inflammation ofthepulp may reach down the entire length ofthe root or roots and begin to cause the apical PDLto become inflamed (acute apical periodotltitis l,4PJ. Norv the patient may have not onlyr rhrobbing toothache but also pressure sensitivrty (to the presstu< of che*'ing or pera$sion).This stage marks a later point in the pulpal degenerative timeline when the tooth is the

''hottest" and usually the most difficult to get numb.

Important: Sometimes it is hard to distinguish between reversible and irreversible pulpitis,in \\ hich case caries conftol (the plqcement ofa temporary'.fi11i1g) is a consewative approach:orr ard making the final diagnosis. lfa tooth responds well to this tempomry filling. then thereed ibr root canal therapy at this time is ruled out.

Rem€mber: Reversible pulpitis or pulpal hyperemia is mereJy the engorgement ofthe pul-pa1 ressels $,ith blood. Once the causative agent (i.e., ha.leria or a restoraliotl in h)peroc-c/r.rro7rl is removed or adjusted, the pulp will most likely retum to normal.

*** Hyperemia of the pulp is an excessive accumulation of blood in the pulp resultingin vascular congestion.

Pulpal hyperemia is sometimes called "reversible pulpitis" and may be caused by phys-

ical. chemical or bacterial insult. Following restoration placement, teeth often become

hl peremic and are sensitive to cold for a few days. The pain is not spontaneous and

does not last longer than approxiraately 10 seconds after the stimulus is removed. It isdris iict. its short duration and low intensity, which distinguishes it from the pain ofacutepulpiris /"iiraerslble pulpitis"). Remember: Hyperemic teeth respond on a lower level(rf curent on the EPT (electric pulp te,tter) than a nonnal tooth.

Treatnrent: If possible. the source (e.g., high restoretion) should be removed. lf indi-.3red. a sedative restoration can be useful. If due to deep caries, an indirect pulp cap

should be used only in permanent teeth and when pulp pathology is believed to be re-rersible/e.g.. noperiopicol patholopy, no lhgering sponlaneous pain lhqt might bevorseorerniqht and stimulated pain ol short duratiotl onl,-).

Important: Pulpal hyperemia caused by bacterial insult is a limited inflammation ofthepulp. The tooth can recover if the caries is eliminated by timely operative treatment.

\\'hen the pulp becomes severely inflamed as indicated by a thermal stimulus producingpain that lasts long after the stimulus is removed (longer than l5 seconds), this suggests

"irreversible pulpitis." The pulp is unlikely to recover after removing the caries.

Remember: The most effective way to reduce injury to the pulp during tooth preparation

is to use adequate irrigation to avoid heating ofthe dentin.

Pins

What was previously an MOD amalgarn in #20 now shows that the entirelingual portion of the tooth has fractured off, You believe that the tooth

is restorable with a pin-r€tained amalgam restoration/cor€.How many pins will you likely use and why?

. one, because you are missing the lingual cusp only

. tu,o. because you are missing both the mesio- and distoJingual line angles

. three. because you are missing the mesial, distal, and lingual walls

Cotyrigfi t O 201 l -101 2 - Denral Decks

OPERATI\TE Pins

The most retentive style of pin is the self-thr€aded pins because they arecemented into pinholes that are small€r than the pin itself.

. Both the statement and the reason are conect and related





97

CopyriShr aO 20ll ?012 ' Denral Decks

*** The rule of thumb is one pin per missing line angle.

The largest pin that can safely be placed should be selected in any situation. The opti-mal placement is at the line angles or comers of the tooth, where the tooth./root mass isgreatest and the risks ofperforation into the pulp or furcation are minimal.

Advantages:. More conservative and less time involved than castings. Enhances retention form (adds n a//s) and is an economical alternative to castings

Disadvantages:. Can cause dentin crazing. Microleakage can occur at pin channel. Pins rveaken amalgam alloy. Placement can result in pulpal exposure! perforation and fracture oftlle tooth

Tl pes of Pins:. Cemented. Friction-lock. Self-threading

Self-threaded pin systems (fbr exantple, TMS. ll haleden 1) use holes sized just under the

scre\\' diameter The elasticity (resiliency) of the dentin functions to retain the screwed

pin. This systern comes with a selflimiting drill of optimal 2 mm depth and self-shear-

ins pins that gunrd against overtightening. This type ofpin system is the most frequentlyused olthe three tlpes ofpins.

The T\IS (Thread-ntate .ttsler?) system has four sizes of pins (reg at minin, minikin

tt tl ntinLtta). They are available in titanium or stainless steel plated with gold.

Cemented pins are serrated stainless steel pins that are cemented into pinholes that are

larger thrn the diameter ofthe pin.

Self-threading Drill Size Pitr Diameter

Regular 0.027" 0.031"

Minim 0.021" 0.024'

Minikin 0.01?' 0.019'

Minuta 0.0135' 0.015"

FrictionJocked pins are tapped into pinholes that are smaller than the diameter ofthe pin.

They are retained by the elasticity ofthe dentin.

Note: The increased strength of the latest dentin/enamel bonding agents, coupled withthe revived use ofretentive slots, pot-holes, grooves and channels, has led to a reductionin the use ofpins. Examples ofdental adhesives include: Amalgambond Plus, All Bond2, DenTastic and Easybond. These systems allow adhesion to preconditioned substrate

with the added benefits ofretention and sealing ofthe restoration and a stronger total co-

hesive mass to support all remaining cuspal segments ofthe tooth.

*** Although the pinhole is smaller than the self-threaded pin, it is NOT cemented.

Pins

Regarding the use of pins, all of the following statements are true -gXCtPf one.Which one is the.EXCBPTIOM

. Use one pin per missing axial line angle, cusp, or marginal ridge, up to a maximum offour

. Use large-diameter pins whenever possible

. Use the minimum number ofpins compatible with adequate retention (pins v,eqken amalgom)

. Pins should extend 2 mm into dentin and restorative material

. Keep at least .5 to I mm of dentin between the pin and the DEJ

. Pins should be placed away from furcation areas and parallel to the extemal tooth sudace

. Coating of pins with adhesion promoters such as Panavia and 4-META materials improves

liaclure resistance ofcomposite and amalgam cores

. Pins are bent to make them parallel or to increase their retentiveness98

Copyrighr C 20ll :012 Denlal Decks

OPERATIVE Pins

When preparing a pin channel you perforate into the vital pulp chamber.What best describes your next step.

. Explain to the patient the need for root canal treatment

. Allori bleeding to stop, dry with paper point, place calcium hydroxide

. .\llou bleeding to stop, dry with paperpoint, place pin to depth of I mm as to not enterthe pulp chamber

. Allol bleeding to stop, dry with paper point, place pin elsewhere and restore with amal-

_gam

99

Coplright (l 20ll 20ll Denral Decks

*** This is false; pins are not to be bent to make thetn parallel or to increase their reten-tiveness. Occasionally, bending a pin may be necessary to allow for condensation of amal-gam occlusogingivally. When pins require bending, a bending tool must be used. A handinstrunent fe.g., an amalgam condenser or spoon excavator) should not be used.

The main advantage of pins is to improve the retention of large restorations. Unfortu-nately, pin retention techniques are not without disadvantages. Pins are known toweaken th€ restorativ€ mat€rial into which they intrude. Ifplaced by force, they can cre-ate stresses that cause crazing ofthe tooth structure. They may provide an additional deeppath for microleakage. Ilplaced in close proximity to the pulp, they may aggravate an ex-isting pulp problem or create one. The use ofpins may be contraindicated in young teethrvith very large pulps and in teeth with reversible pulp pathology, which might be aggra-vated by instrumentation. Placement is always influenced by the limitations olaccess andr ision.

Remember: Cusps to be restored with dental amalgam should be reduced by 2 mm whilefbnning a flat surface (perpendicular to the occlusal forces).

\ote: After restoring a tooth, make sure you check the occlusion very carefully. If a

restoration is left in supra-occlusion, the patient will retum complaining of discomfortu hen biting, usually with no other symptoms.

Remember: If when attempting to drill a pin hole the drill enters a vital pulp chamber,the proper treatment is to allow the bleeding to stop, dry with a sterile paper point and

place calcium hydroxide in the hole. Proceed with a better location for a pin hole. Ifa pinchannel perforates the extemal surface ofthe tooth and all factors are favorable, a pin can

be placed provided there is no extension beyond the surface ofthe tooth.

Idealty, pins should be placed I to 1.5 mm inside the cavosurface margin and at least .5mm inside the dentinoenamel junction (DEJ), rf preserft. Placement ofthe pin channel atleast ,5 mm away from the DEJ helps prevent crazing or complete fracture of the re-rraining enamel. Note: The optimal depth of the pinhole into the dentin is 2 mm.

The rule of thumb: Pins should be 2 mm into dentin,2 mm within amalgam, and I mmtiom the DEJ (to be .salb)with no bends in the pins. Important: The twist drill used to

prepare the pin channels must be angled so that it remains in dentin only. The channelshould be prepared parallel to the extemal surface ofthe tooth.

\\'hen pins are placed nearer the occlusal surface, as in cuspal coverage areas. the pins

should project only minimally into the restorative material (2 mmfor amalganr); long pins

near an area ofocclusal loading will significantly weaken the amalgami additionally, the

purpose ofthe pin in cuspal coverage areas is to bind the cusp to the restoration and to re-

sist lateral displacement with occlusal function.

Note: Maximal intemin distance results in lower levels of stress in dentin.

. Time consumption

. Patient objection

. Cost

. Staffallergies to material

.t 00

CopyiShr O 201 l'2012 - Dental Decks

The rubber dam can still be used effectively even if teeth arecrowded and overlapped because the hole punch pattern

does not alwavs have to be followed.




. The statement is NOT cofiect, but the reason is correct


101

Copldght O 201 l-2012 - Dent.l Decks

*** However, ifyou become proficient in placing the rubber dam and explain to patients

the advantages of using it, these clairrs will be eliminated.

Advantages of using the rubber dam:. Dry, clean field. Access and visibility. Improved properties of dental materials. Protection ofthe patient and the operator. Operating efficiency

The following conditions may preclud€ the use of th€ rubber dam:. Severely tilted teeth. Some third molars. Teeth that are not erupted sufTiciently. Some respiratory problems such as asthma or severe colds in which breathing through

the nose is di{Ticult

Remember: The use of a rubber dam is the standard of care when performing endo-

dontics.

In this case, you can punch the holes closer or in a similar pattem to the teeth, allowingfor the elimination ofwrinkles and avoid having papillae protruding through.

Five functions of rubber dam isolation:. Retracts soft tissue, such as lips, cheeks and tongue. Provides for clean, dry field. Protects the patient by eliminating the possibility ofthe swallowing debris or instru-ments. Protects the dentist somewhat by isolating him,/her from possible infectiousconditions in the patient's mouth.. Provides for maximum physical properties of materials. For example: The rubber

darl provides a dry field, which is essential for placement of amalgam restorationsas $ ell as cements. Remember, the cements that are placed under dry conditionsha\ e maximum strength. Also a dry field prevents delayed expansion of amalgam.. Saves time rubber dam saves time due to the fact that the operator can workmore efficiently in a clean, dry field where visibility is not impaired.

Important: In order for a rubber dam clamp to be stable, all four points of the jaws ofthe clamp must contact the tooth gingival to the height ofcontour They should not extend

beyond the line angles to prevent impingement ofthe interdental papilla and possible in-terference with placement ofa wedge.

l.A frequent cause of interdental papillae protruding from beneath the rubber

dam is holes that were punched too close together.2. Wdnkling ofthe rubber dam between isolated teeth is the result ofholes thatwere punched too far apart.

. Both the statement and the reason are correcl and related





102Cop)righr O 20ll-2012 - Denhl Decks

. Apply acid etch

. Place the low viscous sealant material

. Apply bonding agent

. Wash acid etch away

. Use rubber prophy cup with pumice

103

Cop),right O 20ll -2012 - Detual Dsks

*** It is true that the Young's rubber dam frame provides less soft tissue retraction thanthe Woodbury. However, that is not why it is used, it is simply more convenient.

lmportant points about using the rubber dam:. Apply lubricant to the lips and comers ofthe patient's mouth.. Plot the hole on the rubber dam. Always isolate a minimum of three t€eth. Punch

the appropriate size hole ior a particular tooth. For a tooth b€aring a clamp, thehol€ should be one size larger than thos€ without a clamp.. An appropriate clamp is selected that will fit the most distal tooth to be isolated. Thedam may either be stretched over the clamp with the clamp in place on the tooth; orthe clamp may be carried with the dam and placed on the tooth in one step.. Once the dam is placed, it is secured with either a Woodbury or Young's holder

l.ft qnte).. The rubber dam is inverted into the gingival sulcus using floss and/or a blast ofair and

an instrument such as a plastic instrument this will prevent seepage of saliva.

Remolal of the rubber dam very important: Removal is the reverse of application,

ercept all ligat.lres (interdental septum of dam) must be cut and removed before the

dam is removed.

Importanti Sealants necd micro-mechanical retention. The surfaces should be cleaned rvith a pro-phr laxis brush or rubber cup and pumice with watcr. Whcn thc tccth arc cffectively isolated from saliva.r.:rriminaiion. the surfaces are dried and acid-etched by ihe application ofa 30 to 50% phospho cacidi.rhrrrlrn for one minute. Thc solution should bc gcntly agitatcd during thc application. This is then washed

3\fa\ and dried leaving a frosty-appearing /drlland chalky) etched surface.

\liscellaneous information concerning sealants:I The placemcnt ofsealants is a highly effective means ofpreventing pit and fissure caries. It is safe.

h is currently underused in both pivate and public dental health care dclivcry systems.

: The subsrantial rcductions in dental decay that have occuned in the young population ofthe UnitedStates are due. for the most part. to thc use ofsystemic and topical fluorides. The control ofsmoothsurtace caries that js providcd by fluorides is ofcritical imponance to the additional effectiveness ofsealants,

i. Thc propenies ofsealants arc closer to those ofunfilled direct resins than to thosc offillcd rcsins

.1. Sealants are weak compared to filled resins (composites). The strength of a sealant is sacrihced inorder to make it flou,into the pits and fissures (lhe viscosity needs lo be lo$'enough tofov'into the

pils andfssures).5. The most likely result ofinadvertently sealing a small carious lesion in the occlusal surfacc ofatooth is that the caries rvould be arrested.6. Research indicatcs that pit and lissure sealants are retained best on maxillary and mandibular bi-cuspids. Howev€r, the first molars 1d4r. and mand.) bcncltt thc most from sealants.

7. Ifa topical fluoride is to bc used in conjunction with a pit and fissure sealant, the fluoride must bc

app)ied either beforc the conditioner /acld elcrdra/ or after the sealant.

. The first statement is true, the second statement is false

. The first statement is false, the second statement is true



1(}4

CoDTight O 201l-2012 - Deotal Decks

Fluoride reduces the r|te ofenamel solubilitv.

This increases the hardness of enamel.

. The first statement is true, t}le second statement is false




105

Coprighr O 201 l'2012 - Dental Decks

Remember: Light cure materials are all cured by visiblc light nowadays, not UV AIso. both lightcure and chcmical curc have indistinguishable rcsults.

Pit and fissure sealants were first devclopcd in the 1970s and 1980s, and thcir cltcctivcncss in pre-vcnting caries has now bccn rvcll cstablished. Two predominant typcs ofpit and fissurc sealant ma-lerials are available: resin based sealants and glass ionomer cgments.

Availablc resin-based sealant materials can bc polynerized by autopolynrerization, photopoly-merization using visible light or a combination ofthc two processes.

Glass ionomer ccmcnts arc available in two fonns. both of which contain fluoride: conventionaland resin-modified. Glass iononter ccmcnts, which do not require acid etching ol'the tooth surf'ace,gcncrally are easier to place than are resin-based scalants. They also are not as moisture-sen:irivcas their resin-bascd counlerparts. Glass ionomcr materials, which wcre developed for their abilityto relcase fluoride. can bond directly with enamel. It is hypothcsized that release of fluoride fromthis nlaterial nlay conlribute to caries prevention. Howcvcr, the clinical cfl'cct of lluoridc releaseliom glass ionorrer cenent is not well-eslablishcd.

l. The succcss ofa sealant is highly dependent upon obtaining and maintaining an in-\ote. timate adaptation ofthc scalant to the tooth surface and thereby hopefirlly sealing it.

f. Research has demonstrated that caries protcction is l00yo in pits and fissures thatre main completel] sealed,3. Resin-based sealants are the firsl choice ofnraterial lor dental sealants..1. Glass ionomer cement may be used as an intcrim prcvcntive agent when there are in-dications for placement of a resin-based sealant but concems about moisture controlnlay compromisc such placement.

5.Placement of pit-and-llssure sealants significanlly red|.|ces the perccntage of non-cavitatcd carious lesions that progrcss in children, adolesccnts and young adults tbr as

long as live years after sealant placement. compared with unsealed tccth.

Fluorides exert their anticaries effect by three different mechanisms:1. The presence of fluoride ion greatly enhances the precipitation into tooth structureof fluorapatite from calcium and phosphate ions present in saliva. This insoluble pre-cipitate replaces the soluble salts containing manganese and carbonate which were lostdue to bacterial-mediated demineralization. This exchanse Drocess results in the enamelbecoming more acid resistant.

i. Incipient. noncavitated, carious lesions are remineralized bv the same process.

-l. Fluoride has antimicrobial activity. In low concentrations fluoride ion inhibits theenzvmatic production of glucosvltransf€rase. Glucosyltransferase prevents glucoseliom forming extracellular polysaccharides, and this reduces bacterial adhesion and.lou s ecological succession. Intracellular polysaccharide formation is also inhibited,pre\ enting storage of carbohydrates by limiting microbial metabolism between theItost's meals. Thus the duration ofcaries attack is limited to periods during and imme-diately after eating.

l.The concentration offluoride in the body fluids is regulated by an equilib-\otes rium relationship between bone and urinary excretion..t;::,,:.:.,,.: 2. Fluoride ion is easily exchanged lor hydroxyl ion in the lattice structure of

enamel because the fluoride ion is slightly smaller than the hydroxyl ion, andhas a greater affinity for the hydroxyapatite crystal than does the hydroxyl ion.

*** Fluoride does not make the enamel hardel but reduc€s its rate of solubilitv.

. sl0

. )lJ

. $38

. $58

106

Cop)right O 20ll-2011- Denlal Decks

AII persons should know wheth€r the fluoride concentration in tleirprimary sounce ofdrinking water is below optimal ( ),

optimal ( ), or above optimal (______-J.

. less than 0.5 ppm, 0.5 1.0 ppm, greater than 1.0 ppm

. less than 0.7 ppm ,0.7 1.2 ppm, greater than L2 ppm

. less than 0.8 ppm, 0.8-1.3 ppm, greater than 1.3 ppm

. less than 0.9 ppm, 0.9 1.4 ppm, greater than 1.4 ppm

107

Cop,,right C 20ll-2012 - Dental Decks

In relation to teeth, fluoride is characterized by the following:. Its concentration increases in the external layer ofenamel throughout lile.Its concentration increases during topical application, but decreases for a few daysafter treatment. Fluoride uptake is gr€ater in enamel than in dentin or cementum. Increasing the fluoride content in the external layers ofthe tooth increases the resist-ance ofthe enamel to demineralization

Remember: The optimal concentration offluoride in conmunity drinking water depends

upon the average air temperature and the average water consumption. For temperateclimates it is 1 ppm, for wamer and colder climates, the amount can be adjusted from 0.7to 1.2 ppm, respectively.

1. In communities without fluoridated water supplies, the most cost-effective

Notec . method ofdelivering fluoride to 6-12 year old children is through school water

. ,. fluoridation (as opposed to fluorkle tablets, brushing with a.fluoride gel orrinsing vith fluoride mouth rinse).2. The most effective means ofincreasing the fluoride content in the extemallayers of teeth is the daily application of 1.23% acidulated phosphate fluoridein fitted trays lor four minutes. Obviously this is not realistic, since we do notroutinely do "daily" applications.

The optimal fluoride levels for public water supplies is about 1 part per million (PPM).At 0.I PPM and below, the preventive effect is lost and the caries rate is higher for suchpopulations lacking sufficient fluoride exposure.

This knowledge is the basis for all individual and professional decisions regarding use olother fluoride modalrties (e.g.,fluoride toothpaste.for chikhen under 2 years ofage, mouthrinse or supplemenlt. It is recomrnended that parents and caregivers of children, espe-

cialll children aged less than 6 years, know the fluoride concentration in their child'sdrinking $ater. For example, in nonfluoridated areas where the natural fluoride concen-

rrarion is below optimal, fluoride supplements might be considered, whereas in areas

u here the natural fluoride concentration of more than 2 pprr.r, children should use alter-

nati\ e sources of drinking water.

Fluoride is obtained in two forms: topical and systemic. Topical fluorides are found inmanl ty,pes oftoothpaste, mouth dnses and in special gels or pastes applied in the dental

ofllce.

Sy stemic fluorides are those that are ingested. They include fluoridated water and dietarytluoride supplements in the form oftablets, drops or lozenges. Systemic fluorides are in-tegrated into children's teeth as their tooth structures form.

The greatest reduction in tooth decay is achieved when fluoride is available both topi-cally and systemically. Water fluoridation provides both types of contact.

Studies have established that root sensltivity ls due in part toopen dentinal tubules at the root surface.

The hydrodynrmic theory is the proposed mechanism for this sensitivity.





108

Copyrighr O 2011'2012 - Denial Decks

. 1.23% acidulated phosphate fluoride and lo% neutral sodium fluoride

. 0.4olo stannous fluoride and |.23oA acid ated phosphate fluoride

. 0.49./0 stannous fluoride and l% neutral sodium fluoride

. l.23Yo acidulated phosphate fluoride,0.4o% stannous fluoride and I o/o neutral sodium

fluoride

109

Cop)ri8lr O 20ll-2012 - Denhl Decks

recommended to a head and neck cancer patient forhome-care custom trav use?

The most accepted theory to explain the unusual sensitivity and response of exposedroot surfaces to various stimuli is the hydrodynamic theory. This theory postulates thatthe pain results form indirect innervation caused by dentinal fluid movement in thetubules, which stimulates mechanoreceptors near the predentin.

The rationale oldesensitization procedures is not fully understood. Some techniques maydepend on denaturation of the superficial ends of Tomes' fibers or of nerve endings indentin. Other procedures are designed to deposit an insoluble substance on the ends ofthefibers or nerves to act as a baffier to stimuli. Still others are designed to stimulate sec-

ondary dentin formation thus insulating the pulp from extemal stimuli.

Nunerous fonns of treatment have been used to provide relief, such as topical fluoride,fluoride rinses, oxalate solutions, dentin bonding agents. sealants, iontophoresis, and de-sensitizing toothpastes. AII of these methods have met with varying degrees of success,

and none has been totally effective (although dentin bonding qgents provide the best ruteol -.u(cess). When these conservative methods fail to provide relief, restorative treatmentis indicated.

\ote: The application of sodium fluoride has been recommended as an effective treat-ment ior root sensitivity based upon the precipitation of calcium fluoride crystals in the

Lrpen dentinal tubules.

The gel contains either 1.07o sodium fluoride or 0.47o stannous fluoride, For maxi-mum benefit, the gel must be in direct contact with the teeth. Fluorides are recommendedto protect these patients from post-irradiation caries.

Remember two important points:l. The fluoride found in commercial toothpastes is not adequate for people who havehad head and neck radiation.l. These patients must continue to use the fluoride gel as directed for the rest oftheirlili to protect their teeth from rampant decay.

Instructions for patient: The trays containing the fluoride are placed over the teeth fora prescribed period of time (usually 10 minutes), and he/she may not eat or drink for atleast 30 minutes. Usually this is done at night after toothbrushing and just before goingto bed.

The daill use of fluoride gel in custom trays at home is indicated in the following situ-ations:

. Rarnpant enamel or root caries in any age group

. Xerostomia

. Head and neck radiation therapy

. For use on abutment teeth under an overdenture

. Hypersensitive root surfaces

lmportant: Fluorapatite is the most stable reaction product ofa topical application offlu-oride.

Acidulated phosphate flioride (APF)

Stannous fl uoride (SNF2)

Sodium fluoride (NaF)

Causes the most severe staining

Most common over-the-counter fluoride

Most common in-office fluoride

110

Coplright O 20ll-2012 ' Dertal Decks

Acidulated phosphate fluoride has a low pH.

Becaus€ of thls, it is contraindicated on porcelaln &nd composite restorations.\-,



. Both statements afe true


111

Coplriglr @ 201I ?012, DerralDecks

Important:l. Acidulated phosphate fluoride (lPF) is the most commonly applied in-office fluo-ride treatment.2. The combination of 1.23% sodium fluoride and I M orthophosphoric acid results inacidulated phosphate fluoride. It is very stable in solution.3. The most common recommended over-the-counter fluoride is 0.05% sodium fluoride.4. Stannous lluoride (80,6 F) has avery bitter, metallic taste, may bum the mucosa, and

has a short shell life.5. The tin ion in stannous fluoride may be responsible for staining the teeth, but it maybe beneficial for anestinc root caries.

\NF APF SnF,

Concentmtion 2o/o t.23% 8%'

Fluoride lon 7o 0.91 1.23 1.95

ppm Fluoride 9.040 ppm 12.100 ppm 19,160 ppm

Mg FVml 9.04 12.0 19.16

Emc.cy )9% 28yo 320/r

Taste Bland Biner w/o flavoring V€ry bitter, metrllic

Tooth discolorrtlon Nofle BroM

Gingivrl reectlon Nonc None Occasional

Important:. The pH ofAPF is approxrmately 3.5 (acidic). The pH of NaF is approximately 9.2 /ba.sicl. The pH of SnFz is approximately 2.I to 2.3 (acidic)

lmportant: APF solutions and stannous fluoride /SNF2I should not be used on patients withporcelain. glass ionomer, and composite restomtions. They have been shown to remove the

_claze trom the surlace of these rcstontions. Neutral sodium fluoride /NaF/ is best to r.rse if:hese restorations are present. Also, APF should be avoided on implant patients, it may cor-

r"Jc th< .urface oftit.rnium implants.

$ hen painting fluoride on, it is very important to isolate the teeth with cotton rolls. Whenusing ilLroride trays, cotton rolls may be placed in the premolar areas to increase patient com-tbfi and help keep the fluoride in place. Patients are asked not to brush, rinse, eat or drink 30

mrnutes alier a fluoride treatment so that the fluoride is left undisturbed and is able to continuereactjng \!jth the hydroxyapatite tbr some time after the initial application. Fluoride treat-menrs should be applied for four minutes. although there are now some one-minute products

rhar are beins marketed.

Ayoung child gets into the bathroom cabinet and ends up eating a full tube oftoothpaste. The mom calls you lirst, besides telling her to call poison control

you will ask all of the following questions TXCEPI one.Which one is the.EXCXPZOIV?

. How much does the child weigh?

. what kind of toothpaste was it?

. How old is the child?

. Did the child get into any other dental products (i.e., mouth w,ash)

112CoorightO 20ll-2012 - Denhl Decks

Sealants can be effective when placed over inclpient caries lesionsbecause carles is caused by anaerobic microorganisns.


. Both the statement and tlle reason are conect but NOT related




113

Coplrighr O 20ll-2012 - Dental Decks

*** As with any toxin, the toxicity of fluoride is based on weight, not age.

Fluoride, administered in large doses can be fatal and should be kept with all other med-ication

-out ofthe reach ofchildren. This includes fluoridated toothpaste, gels and mouth

rinse. The generally excepted toxic amount of fluoride that needs to be consumed at onetime is 5 mg/kg of body weight. This means that a child who weighs 25lbs would needto consume the equivalent of56 one mg tablets offluoride, not a difficult task to accom-plish for most 2 year o1ds.

Important: An 8.2 ounce tube of toothpaste contains 232 mg of fluoride or 28 mg perounce.

:{ote: Tlre most common forms of fluoride found in toothpastes are sodium fluoride andsodium monofluorophosphate. Amine fluoride and stannous fluoride, are less common.

**" Scalants can bc effective when placcd ovcr incipient caries lesions becausc caries is caused byaerobic nricroorganisms.

Studies hare caret'ully demonstrated that once an incipient carious lesion is sealed, the caries is{opped lbr most intcnsive purposes. Sincc carics is caused by acrobic microorganisms, once scalcdLr\ !-r \'ilh a sealant an anacrobic environment is created in which the microorganisms become statict r die and there is no funhcr action because there is no melabolite 10 reach the orsanisms. there is

no o\\sen lbr them to cxist in thcir cnvironment, thereby they die.

1. Sealants act as a physical barrier in preventing bactcria liom accumulating in thc

\otes pits and fissures ofthe teeth.

2. Care should be taken not to mix the sealant resin too vigorously prior to placementor to ovcr-nranipulate the sealant rcsin upon placement. Eithcr ofthese errors could incorporate air into the sealant r€sin, resulting in a void in the sr.rrface ofthe sealant.

3. As long as a sealant remains intact, decay will not develop undemcath it..1. The follorving factors nlay influence which teeth are candidatcs for scalants: thepresence of interproximal decay, patient age and how caries pronc the patient is.

5. Sealants should be placed right after the tooth has f'ully erupted, before the decayprocess has had a chancc to bcgin. For pcnnancnt molar placemcnt, this would usuallybe around age 6 and 12, give or take 6 months.6. Although sealants are most commonly placed on permanent molars, they may beplaced on deciduous teeth in the following instances: the presence ofdeep pits and fis-sures. a very carics prone mouth and a tooth that is not likely to bc cxfoliatcd any timcsoon,

7. The most common reason lbr sealant failure is salivary contamination, usually due

to inadequate isolation.

Which of the following is least associated with theshort term strength of a material?

. Creep

. Modulus olelasticity

. Resilience

. Brittleness

114

Cop)right O 201 | -2012 - D€ntal Decks

Plastic deformation takes place prior to elastic deformation.

The distinction between these two is t€rmed the ehstic limit.


. The first statement is false, the second statement is tme



fisCoplriglu O 20ll-2012 - Detrtal Decks

*** Creep (strain |elaxation) - deformations over time in response to a constant stress.The key term in the question is "short term".

Materials which are relatively weak or which are relatively close to their melting temper-ature are more susceptible to creep. Dental wax deforms (creeps) under its own weightover short periods of time. Traditional dental amalgam restorations are involved in intra-oral creep.

Brittleness is generally considered to be the opposite of toughness. A brittle material isapt to lracture at or near its proportional limit. A brittle material has a high compressivestrengtlr but a low tensile strength /e.& , amalgam). Note: This is why amalgam prepara-tions do not have beveled margins (they need butt joittts).

The modufus of elasticity is a measure ol the stiffness or rigidity of a mateial (it is tlrcratio of sh?ss to the strain below,the elastic limit).lmport^ntz The higher the modulusolelasticity, the stiffer, or more rigid, the material and the less strain it exhibits for a givenStTCSS.

Resilience is the energy that a material can absorb b€fore the onset of any plastic defor-mation.

Remember: Toughness is the property of being difficult to break. It is affected by lher ield strength, percent elongation, and the modulus of elasticity.

*** Elastic deformation takes place prior to plastic deformation. The distinction betweenthese tivo is termed the elastic limit.The elastic limit is the greatest stress to which a material can be subjected, such that it willrerum to its original dimensions when the forces are released. Up to the elastic limit onlyelastic deformation is involved, but beyond that, there is a combination ofelastic and plas-tic defonnation. with the plastic portion increasing and the elastic portion decreasing upto rhe breaking point.

-\n erample rvould be if a snrall tensile stress is induced in a wire, the resulting strainmight be such that the wire will return to its original length when the load is removed. Ilthe load is increased progressively in small increments and then released after each addi-tion of stress, a stress value finally will be found at which the wire does not retum to itsoriginal length after the load is removed. In such a case, the wire is said to have been

5tressed beyond its elastic limit.

The proportional limit is the greatest stress, which may be produced in a material such

that the stress is directly proportional to the strain. A material that has a high proportionallimit compared to one with a lower proportional limit also has more resistance to per-manent deformation.

Although the two terms, elastic limit and proportional limit, are defined differently,their magnitudes are so nearly the same that lor all practical pur?oses the terms can oftenbe used interchangeably.

Note: The yield strength represents a stress slightly higher than the proportional limit.

In general, ductility in temperature,in temperature.whereas malleability

. increases with increase, decreases with increase

. decreases with increase, increases with increase

. None ofthe above

1t6Cop)righr €, 201 l-2012 - Denral Decks


. Both the statement and the reason are conect but NOT related




117

Cop)righr e 20ll'2012 - Denial Decks

Ductility is the ability ofa metal to easily be worked into desired shapes (lbr example, thedbili4, to ./brm a wire Ji'om a metal). '|tese materials undergo extensive plastic deforma-tion prior to fracture (in tension). Ductility is dependent upon plasticity and tensil€str€ngth.

Not€: Ductility is usually expressed in terms of the percent elongation; the higher thevalue, the more ductile tlre alloy.

Arelated term is malleability, which describes a metal being able to be hammered (com-pression) into a thin sheet without rupture. It is also dependent on plasticity, but is not as

dependent upon tensile strength as is ductility.

Gold is the most ductile and malleable metal. and silver is second. Of the metals of in-terest to the dentist, platinum ranks third in ductility and copper ranks third in malleabil-it\.

t** An enamel bonding agent which bonds enamel to composite is termed a adhesivejoint. this is because there are two unlike materials being bonded together

Adhesion is a process of solid and/or liquid interaction of one material (atlhesive oritdhere t) \vith another (adherend) at a single interface. Most instances ofdental adhes-ion are also called dental bonding. A pit and fissure sealant bonded to etcbed enamel

is a case of dental adhesion.

-\n adhesiye joint is the result of interactions of a layer of intermediate material (adhe-

si\e ot adlrcrent) with two surfaces (adherends/ producing two adhesive interlaces.Eramples include onhodontic bracket bonding resin, enamel bonding system for a com-posite resin. and a bonded porcelain veneer.

There are trvo principal types of adhesion:

1. Ph! sical forces: called van der Waals forcesl. Chemical forces: called chemisorution

Adhesive potential can be predicted by measudng the spreading or wetting ofthe adhe-

sive over the surface ofthe substrate. This is done by determining the contact angle ofthedrop of adhesive as it spreads out. The smaller the angle, the greater the wetting andthus the potential for adhesion.

. Shear

. Flexion

. Torsion

. Compression

. Diametral compression/tension

. Tension

Match the following mechanical propertles ofloading terms with th€ir correct pictur€s.

*-D*+0--lY-gl

HY,ixqH

Decks

118

Coplrighr O 201 l-2012 - Dental





119

Cop)right O 20ll-2012 - Dental Decls

. Compression

. Tension

. Shear

. Torsion

. Flexion

-trl'HHttitt

. Diametralcompression/tension

*** Strain is the actual change in shape or deformation that accompanies any stress.

*** Tertiary dentin is formed in response to caries, operative procedures, or wear. Sec-ondary odontobfasts secrete tertiary Qeparative) dentln.

Throughout life, the dentin will respond to environmental changes (iormal wear, caries,operatire procedures, €lc, These changes initiate the deposition oft€rtiary dentin whichrs formed by repfacement odontoblzsts (termed secondary odontoblastr). This repara-tile dentin will be limited to the site ofirritation. The composition ofreparative and sec-ondarl dentin is basically the same /reparative dentin is more itegular) andthey differonly in location of deposition.

If the environmental insult is strong enough, it will kill the odontoblast and its tubularprocess. leaving the tubule empty. If there is a collection of empty tubules, they are re-fened to as dead tracts. In time, these ttbrles (dead tracLsl will calcify. The term usedto describe the tubules that become calcified is sclerotic dentin.

. 1. Primary dentin is the dentin forming the initial shape ofthe tooth. It is de-i\otcr: posited before completion ofthe apical foramen.,&*., 2. Secondary dentin is dentin that is formed after completion of the apical

foramen. It is formed at a slower rate than primary dentin as functional stressesare placed on a tooth. Secondary dentin is a regular and somewhat uniformlayer ofdentin around the pulp cavity.3. Thejunction between primary and secondary dentin is characterized by asharp change in the direction ofdentinal tubules.

When preparing for an amdgam, an operator should atlow forproper retention forrn. This is because improper preparations

can cause fracture of amalgam restorations.





. NEITHER the statement NOR the reason is coffect

120

Cop)right e 201 l'2012 - Denial Decks

. "That form the cavity takes to resist the forces ofmastication"

. "That form the cavity takes to resist dislodgement or displacement ofthe restoration"

. "The shape or form oflhe cavity on the surface ofthe tooth"

. "The shape or form ofthe preparation after carious dentin has been excavated"

. "The shape or form the preparation assumes after the retention form has beencomoleted"

121

Coplright C20ll-2012 - Dental Decks

OPERATIVE

*** Resistance form is involved in fracture. not retention form.Retention form is that form the cavity takes to resist dislodgement or displac€ment ofthe restoration. For example, the buccal and lingual walls ofa Class I amalgam prepara-tion converge occlusally; thus preventing dislodgement of the amalgam. For Class IIrestorations, this resistance to dislodgement is provided by the occlusal dovetail and re-tention grooves in the proximoaxial line angles.

Resistance form is that form the cavity walls take to resist the forces ofmastication. Re-sistance form prevents fracture ofth€ restoration and the tooth.

Examples: Severely undermined cusps should be reduced so as to prevent fracture.The axiopulpal line angle in Class II amalgam preparation is rounded or beveled so

as to reduce concentration ofstresses and lhus prevent fracture ofthe brittle amalgam.Also, proper angulation ofcavity walls (converging) and pulpal and gingival walls that

are perpendicular to occlusal forces (lat walls at right angles to the long aris oJ the

Ioolll help achieve resistance form.lmportant: The most common cause of fracture at the isthmus of a Class Il amalgam

restoration is inadequate depth at the isthmus area (must be adequate depth to obtqinres istance .fbrm). Most detdnental to the strength of a posterior tooth in a cavity prepa-

ration is an increase in faciolingual width.Remember: G.V Black, is known as the father of modem dentistry. He is known for hisprinciples oftooth preparations, in which he outlines the proper methods to prepare teeth

tbr fillings. The phrase, "extension for preventionrr is still famous in the dental com-munity today and represents Black's idea that dentists should lollow preventive tneasures

to aid patients from developing tooth decay. Further, he organized a classification system\\ ith 5 categories for different pattems oftooth decay which is still in use today. Since that

time, only one more category (Class Vl)has been added to his classification system.

Trr'o important points should be remembered in obtaining the outline form:

I . In general, the margins should be placed in areas of lessened caries susceptibility.This principle is called extension for prevention (phrased by G.V Black)*** TODAY- modification ofprinciple: extension determined by extent of DECAYand RESTORATIVE material.

?. In general. all undermined enamel (which is enamel not supported b:i'- sound dentin)

should be removed.

*** The above two points are influenced by:

. The lateral spread ofdecay at the DEJ

. The t]'pe of restorative material to be used

. The tooth and its relative position in the arch

lmportant: Extension (for prevention) can be restricted in patients with very low caries

susceptibility.

Rememtrer: If when establishing the ideal outline form, caries remains on any of the

rvalls of preparation, the next step is to extend the outline form before excavating any

canes.

r\A pati€nt return$ to your oflice only 24 hours lfter you cemented her new goldcrown on tooth #19. She claims to feel a sharp electrical sensation in both her.ir rEsr ar lrrarp tr9rulltgtlt s3utauull tII t ratt ttcfupper and lowerjaw on the left side. When you explain to her what might be

. happening, you call it:

. Electromagnetic pulse

. Alternating current corrosion

. Electroly'te explosion

. Galvanic shock

122Coplrighr O 201 1,2012 - Dental Decks

Match th€ dental material on the left with the appropriateCoelficient ofThermrl Expansion (ppnrc x 10) on the fight-

. Unfilled resins

. Composite resins

. Tooth

l4.4

11.4

81 -92

22-28

28-3s

123Coplri8ht C 2011,?012, Dental Decks

Galvanic shock is the briefbut sharp electrical sensation one can receive when two dis-similar metals come into contact in the mouth.

An example ofthis phenomenon: An amalgam restoration is placed on the occlusal sur-face of a lower tooth directly opposing a gold inlay in an upper tooth. Because bothrestorations are wet with saliva, an electric couple exists, with a difference in potential be-tween the dissimilar restorations. When the two fillings are brought into contact, the po-tential is short-circuited through the two alloys. The result is sharp pain, Such post-operative pain usually occurs immediately after insertion of a new restoration andgenerally it gradually subsides and disappears in a few days.

Note: The amount of electricity involved in galvanic shock can range up to 1.0 mi-croamneres and 500 millivolts.

Material Coeflicient of Thermal Expansion(ppm/c x l0)

Tooth 11.4

Direct Gold 14.4

Amalgam 22-28

Composite 28-35

Unfilled Resins 8t-92

rhe coetficient of thermal expansion is a measure of the tendency of a materiar tochange in shape when it is subjected to temperature changes (/br example, when eatingor drinking hot or cold items.). Apossible break in the marginal seal ofany restoration be_!'omes Imminent when there is a marked difference in the coefficient of expansion be-n'een the tooth and the restorative material. The closer the coefTicient is to the tooth. thebeuer ldircct gold is bestl. If the coefficient of thermal expansion is relerenced to a sin-gle dimension, it is called the linear coefficient ofthermal expansion (LCTE).TheLCTErs expressed in units ofppr/"C.

One of the consequenses of thermal expansion and contraction differences between arestorative material and adjacent tooth structure is percolation, which is defined as thecyclic ingress and egress of fluids at the restoration margins. The possibility of recur_rent decay at the margins increases with increased percolation.

. Class I

. Class tr

. Class III

. Class IV

. Class V

. Class VI

1UCopyrighr O 20t 1-2012 - Dnisl I}ck

Cavity classification: standardized methods ofrecording the need for restoration exist tofacilitate communication among clinicians, researchers, and dental educators. The mostcommonly accepted means ofclassiling cavities is by the names ofthe surfaces involved.Cavity type is classified further based on the type of treatment and anatomical area in-volved. This classification, developed by Dr. G. V. Black in 1908, is designated by Romannumerals as Class I, Class II, Class III, Class IY Class Y and Class Vl (this is the onlycategory that has been qdded to his original classificttion system). Note: It is importantlo remember that the classification relates to location and not size ofthe cavity.

. Class I cavities: involve the pits and fissures, while all other classifications involvesmooth surfaces ofthe teeth.. Class II cavities: involve the proximal surfaces and occlusal surfaces of premolars

and molars.. Class III cavities: involve the proximal surfaces of incisors and canines that do notinvolve the incisal angle.. Class IV cavities: are located on the proximal surface of incisors and canines and doinvolve the incisal angle.. Class V cavities: are on the facial or lingual surface of all teeth and do not involve a

pit or fissure.. Class VI cavities: are on the incisal edges of arterior teeth or on the occlusal cusp

heights of posterior teeth.

Remember: The best method for definitive detection of incipient carious lesions on the

interproximal surfaces ofposterior teeth (distal suryface of canines through molars) tsbybite-wing radiographs.

147193392-operative2011-2012-1

Documents