Download - Klas II Onlay
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LECTURE 7:
Inlay and onlays
Lecture outline:
1- Cast-gold inlays and onlays
2- Esthetic inlays and onlays. (composite and ceramic).
Cast gold inlays and onlays:
Dr said that we wont be doing these in the lab but we should know about them as
we might do them later after graduation.
The definition of class II inlay: involve the occlusal and proximal surfaces of a
posterior tooth and may cap ONE or MORE but NOT all of the cusps. This was
definition given by the art and science of operative dentistry.
In the class II ONLAY we cover all the cusps, so it is an inlay but with all the CUSPS
capped.
Indications of cast gold inlays and onlays: when do we do them??
• Large restorations: as we want to control the contact and the contour of
the tooth.
• Endodontically treated teeth: in these teeth we need occlusal coverage, for
any posterior root canal treated tooth we need to protect the tooth from
future fracture by capping all of the cusps “occlusal coverage”, either by a
crown or onlay.
Some may ask: how come we do and onlay and don’t do a crown??
Because it is more conservative.
Example: we have a lower 6 with an MOD cavity preparation, in this tooth
the buccal and lingual cusps are still intact therefore, in this situation
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itsbetter to do an onlay than a crown. In the onlay you’ll preserve the tooth
structure; you don’t have to prepare the buccal and lingual walls.
• Teeth at risk of fracture
Fracture tooth syndrome: teeth with fracture lines, these fracture lines may
propagate to fracture the tooth, if we discover these fracture lines at early
stages, then we can control the problem by capping the cusps of the tooth.
And again it is better to do an onlay than a crown to conserve the tooth
structure.
• Dental rehabilitation with cast metal alloys.
If the patient wants to do dental rehabilitation, he has MOD cavity
preparations, fractured cusps so again the best is to use cast gold inalys and
onlays.
• Diastema closure and occlusal plane correction.
We have space between the teeth, and we want to close it using indirect
restorations, the best is to use inlays and onlays.
• Removable prosthodontics abutment.
We want to use this tooth as an abutment for an RPD and it needs to be
restored, the best treatment for it is to restore it with gold either an inlay
or onlay.
Contraindications of cast-gold inlays and onlays:
� high caries rate, because this type of treatment is consuming and
expensive, so we don’t want to make it a definitive restoration in
high caries risk patient until we lower the caries risk of the patient
� Young patients, fear of exposing the pulp during preparation as the
pulp chamber and pulp horns are high in these young patients
� Esthetics, “gold” and because in these esthetic areas we can do
composite, they don’t need a large more expensive restorations like
onlays or inlays.
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As student asked whether gold was better than amalgam or not? And
the dr said I we want to compare between restorations we have to
compare direct restorations with direct and indirect restorations with
indirect. But ofcorse gold is better, longevity is better.
� Small restorations.
Advantagesdisadvantages
Strength ------Gold Number of appointments and
higher chair time, as you have to
do preparations exactly like you
do for the crown, you’ll send the
patient home with the
temporary.
Biocompatible, with soft tissues temporary
Low wear facets, esp with
opposing teeth so if the patient
has bruxism the best treatment is
to use GOLD. (not like ceramic,
high wear rate of opposing
dentition.)
Cost, because we have lab work.
More chair time too.
Control of contour and contacts,
here compared to direct
restoration.
Technique sensitive because you
need to take an impression the
impression is sent to the lab,
then we have the restoration
that needs to be cemented (like
the crown)
Splitting forceesp for the inlay.
Inlays can cause wedging forces,
increase the chance of splitting
the tooth. That’s why nowadays
the use onlays more than inlays
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Basic principles of cast restorations: basics for any preparation, direct or
indirect.
� Conservation of tooth structure.
o Preparation should be as conservative as possible
o Preparation must be designed to protect the remaining tooth
structure. This means that if you have undermined cusps then
you should cut this cusp because it will fracture.
� Retention and resistance form: it is an indirect restoration so we’ll
need the retention and resistance forms just like a crown.
- Reten?on line is gained by 2 parallel walls (intra or extra coronal).
The retention comes from the buccal and lingual walls in the
crown and onlay but in the inlay the retention comes from the
buccal and lingual surfaces inside the tooth just like the class II.
- the degree of convergence (6-10). The inlay is just like the class II
but the wall in it are divergent to be able to insert the inlay and
cement it later on. Not too divergent, if it is too divergent it will
decrease the retention.
- the length of the walls: length the retention
- Twisting or rotational forces are resisted by the presence of
grooves or pins. And also when you have short wall, you place
retention grooves to increase their retention
� Finish line:
Chamfer finish line for the gold.
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Cast gold inlay:
� Suggested burs:
� Plain straight fissure bur (0.8mm head diameter)
� Plain tapered fissure bur ( 0.5 mm head diameter)
� Flame finishing bur.
In the picture in the slide: 1st
bur is used to do cavity prepara?on. 2nd
bur used to do reten?on grooves, and the 3rd
to make the bevel for
the gold
� Occlusal preparation:
Diverging walls ( 4-5 degree) taper/wall; (8-10degree).
It is basically a class II except: 1) the buccal and lingual walls are
tapered, as it is indirect. The clearance is more ( buccallingually)
to be able to make the bevel and to be able to finish the margin
of the gold2) the bevel, we should bevel the cavosurface margin.
� Proximal preparation:
-Increased proximal extensions relative to amalgam preparations
(0.2-0.5 proximal clearance)
-Definite dovetail
-Undercuts blocked out (Glass ionomer or composite), if you
removed the caries and you have undercuts you’ll use GI to block
them out
-smoothness is critical.
� Beveling of the margins:
-proximal bevel
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-Gingival bevel
You can use the finishing diamond bur or the finishing disks,
exactly like we bevel the composite.
Why do we bevel the margins??
Gold can be burnished, so we bevel the margins to be able to
burnish the gold when we cement it, plus it will be easier to work
with it in the lab
- Occlusal bevels he gold we bevel it are usually not necessary.
(only needed when cavosurface margins are very flat and
margins of gold will be unworkable)
� Retention grooves
-0.3mm deep
-in short wall we have to put retention grooves because
retention in short walls will be jeopardized. Exactly the same as
we did in class II we put them on the buccal and lingual walls
inside the dentine
Cast-gold onlays:
The onlay is the same as the inlay but we cap the cusps. The preparation and
principles are the same. We reduce the cusps and cap them. The finish line will be
on the cusps we don’t extend it all the way done.
� In the slides there is a lower 6:
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Carbide or diamond is used for cuspal reduction.
For the functional cusps (centric cusps)here they are the buccal, we do shoulder
preparation and bevel the shoulder, 1.5-2mm reduction for the centric cusps.
For the non functional cusps (non centric cusps) we do chamferand you don’t
have to bevel the chamfer, 1-1.5 reduc?on for the non-centric cusps.We can place
retention grooves distally and mesially.
� Seating and Finishing: finishing is like the finishing we do in the
crown except here, the gold is burnished to make the onlay fit
better, no gaps between the gold and tooth structure.
� Polish and cementation, we cement it using GI.
In the other part of the lecture we will be talking about:
Esthetic inlays and onlays: composite and ceramic.
Indications:
1. Esthetic, the patient is concerned
2. Large defects or previous restorations. In the indirect you can control
the contour of the tooth and contact
3. Economic factors.Its questionable! Usually the indirect is more
expensive than the direct. But if you compare the composite indirect to
the ceramic indirect it is cheaper
Contraindications:
1. Heavy occlusal forces, especially with ceramic because it can fracture. And
wears the opposing teeth, as we mentioned before whenever we have a
wearing problem, gold is our choice
2. Inability to maintain a dry field, we are going to cement it with resin
cements.
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3. Deep subginival preparations. Because of the inability to isolate and
inability to bind to dentine as you go gingivally enamel will be less and it
binds to enamel better than it does with dentine .
Advantages compared to direct restorations:
1- Improved physical properties. Indirect composite has better properties
than direct.
2- Variety of materials and techniques, because we have more than one
option like ceramic and composite.
3- Wear resistance,
4- Reduced polymerization shrinkage, as we know that composite has
polymerization shrinkage, in the indirect restoration we make the
restoration outside the patients mouth (in the oven or they light cure it)
so the polymerization shrinkage will happen outside the mouth
5- Ability to strengthen remaining tooth structure, as we use resin cement
to adhere it.
6- More precise control of contour and contacts
7- Biocompatibility and good tissue response (ceramic)
8- Increased auxiliary support. Because we have the help of the lab in
making these restorations.
Disadvantages:
1- Increased cost and time (lab work, two visits)
2- Technique sensitivity
3- Brittleness of ceramic
4- Wear of opposing dentition and restoration (ceramic)
5- Resin to resin bonding difficulty (indirect resin). This is related to the
oxygen inhibited layer. When we do resin composite restoration
outside the patients mouth, there will be a problem in binding it to
the resin cement in the tooth, because when we do it outside the
patients mouth (the light curing and polymerization shrinkage) we
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put it in the oven for heat, in the polymerization of the composite
the double bond becomes a single bond. And it bond to other
composite because it still has double bonds to bind! So here most of
the double bonds are converted, so the ability to bind it to resin will
be difficult.
6- Short clinical track record, doesn’t have long clinical studies to tell if
these restorations can live long. (longevity)
7- Low potential for repair (ceramic). Fractures are difficult to repair
inside the patient’s mouth. In resin you can acid etch and add to it
and sometimes we even do sand blasting intra orally.
8- Difficult intraoral polishing, this applies to ceramics.
Types of esthetic inlays and onlays:
� Resin composite inlays and onlays
� Posterior bonded porcelain restorations
� CAD/CAM ceramic restorations. ( the new technique)
Resin composite inlays and onlays
Specific indications:
� Maximum wear resistance is desired from composite
restoration
� Achievement of proper contour and contacts. ( again
comparing direct from indirect)
� A ceramic restoration is not indicated because of cost or
concern about wear of the opposing dentition. We need
esthetics but at the same time we can’t use ceramics because
it is expensive and it wears the opposing teeth so we use
composite.
1-Preliminary consideration:
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a- Discuss cost with the patient. More expensive than direct restorations.
b- Identify occlusal contacts ( marks with articulating paper) and degree of
wear. This is when we examine the patient and discuss the treatment
options with the patient, if the patient has wear facts and heavy occlusal
forces we can’t do ceramic restoration.
c- Identify shape desired (vita guide), because we are working with esthetic
restorations.
d- Plan for type of temporary restoration; make alginate impression of
restored quadrant if necessary.
2-isolation: rubber dam isolation is highly recommended
3-preparation:
-recommend brassler esthetic inlay and onlay kit. If you don’t have it you can use
the straight fissure bur or tapered fissure bur or diamond bur that we use for
crown and bridge work.
Basic principles of tooth preparation:
1-all margins should have 90 degree cavosurface. Here on the contrary to gold.
Why should they be 90 degree? In the gold onlays and inlays, the margins should
be beveled in order to polishable margins. But here we need the cavosurface to
be 90 degrees because you need good thickness of ceramic/composite to avoid
fracture.
A student asked why we bevel the tooth surface when we do a class IV?
Because we want to bond more tooth structure, but here in this case we have a
gap and we use the cement , you don’t bind to the whole tooth structure there.
And in the class IV you will bind it using adhesive but here you will be using
cement.
2-all the external and internal angles should be should rounded, to reduce
stresses.
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3-buccal and lingual walls should be occlusaly divergent.
4-the occlusal step should be 1.5-2mm in depth
“The resin composites and ceramic thickness should be at least 1.5mm”
5-isthmus and groove extensions should be at least 1.5mm wide.
6-smooth and relatively flat pulpal floor.
7-proximal clearance should be at least 0.5mm, buccal and lingual clearance in
order to be able to finish the margins. When we cement it in order to remove the
excess cement.
8-gingival margin should be extended as minimum as possible. As we said for
isolation, and bonding to enamel is better than bonding to dentine
9-capped cusps should be reduced 1.5-2mm and have a 90 degree cavosurface
angle.
The dr just zoomed thru the slides quickly and said: this is just preparation read it!
Then again she read on and said:
Page 10 slides: dual cured lu?ng resin and dual cured den?n bonding agent (
followmanufracturer instructions) dual cure: starts with dual cure cement then
you have to light cure at the margins.
Rebond margins with unfilled resin: in finishing and polishing we can remove from
the margins, so we can do acid itching then use the unfilled resin (adhesive) and
light cure it.
CAD/CAM ceramic restoration:
Computer-aided design/computer-assisted manufacture.
The difference between this technique and the conventional way is that the
impression here is digital, then you enter the image into the computer, the
computer will do the design for the restoration then we will have the milling
device.
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It is inbetween the lab and chairside.
Slide page 10 this is the machine (like a computer) that is connected to the milling
machine which has burs. Then we have the blocks; resin composite blocks or
ceramic blocks. These blocks are inserted in the machine, then we take a digital
image of our preparation which will be sent to the milling machine which will
make the restoration and then we cement it.
Its use is limited to inlays, onlays and ¾ crowns.
The dr just read the case seletion and contraindications.
(Follow the pictures in slide page 11)
Again a tooth is prepared, we have to spray special powder for the computer to
be able to take the optical image. We also have aintra oral camera. In the
computer there will ba a 3D image designed, then in the milling machine which
has burs ( two diamond burs) it will carve the external surface of the restoration
and internal surface, then we cement the restoration by DUAL CURED CEMENT.
SO IT IS A SEMI-DIRECT RESTORATION.
End of lecture
We’re almost there….DENTISTS.
You don’t have to be great to start…but you have to start to be great.
BANAN AL-NATOUR