resin-retained bridges re-visited part 1. history and ... bridges part 1.pdf · resin-retained...

HistoryResin-retained bridges have beenused clinically for nearly 25 yearsand today are considered to becapable of producing long lastingaesthetic results (Figure 1) Their

success is partly due to the devel-opment of better retention meth-ods appropriate choice of metalsfor casting and adhesive cements

RetentionIn 1955 Buonocore1 introduced theconcept of adhesion in dentistrywhen he etched enamel with 85phosphoric acid and attached acrylicresin This technique has been dev-eloped allowing restorative materialsto be attached to teeth with littleor no tooth preparation The dev-elopment of a composite resin con-ta ining bis GMA (bisphenol-A-glycidyl methacrylate) by Bowen2

produced a filling material whichcould be bonded predictably toenamel w i thou t the p r ob lemsassociated with acrylic

With these advances in dentaltechnology came a number of tech-niques to restore edentulous spaces

Bonding of extracted natural teethcrowns to adjacent teeth usingcomposite resin3

Attaching acrylic resin dentureteeth with composite4 to adjacentteeth

Attaching composite pontics toadjacent teeth5

Although some of these techniqueswere moderately successfu l a com-mon clinical finding was fracture ofcomposite connectors

In 1973 Rochette6 used a perfo-rated type IV gold casting to splint

periodontally involved teeth togetherusing self-cured acrylic resin Theapplication of this appliance toreplace missing teeth was quicklyseen7 spawning the fi rst resin-retained bridge the Rochette bridge(Figure 2 ) The main disadvantages

of this type of bridge were thelimited retention provided by thecomposite retained metal the thick-ening of the metal retainers requiredto compensate for the weakeningeffect of the perforations and thewear of the resin cement8

Other forms of retention haveincluded

Macro-mechanical retention

Mesh retention9 This techniqueused a mesh within a solid re-tainer The retentive area wasless than the fit surface areabecause the mesh was sealed at

Resin-retained Bridges Re-visitedPart 1 History and Indications

Geoffrey St George Ken Hemmings and Kalpesh Patel

Resin-retained bridges have been usedclinically since the 1970s and offer amore conservative approach to therestoration of edentulous spaces thanconventional bridgework They areeasy to place cheap to fabr icate andhave been shown to be cost effectiveDespite this they are not f requently

used in genera l dental practice andthey have an undeserved reputationfor failure

Since their initial introduction theyhave undergone a number of changesto their method of retention and thematerials used in their constructionThis has resulted in a predictable aes-

thetic restoration which barring theuse of implants is often the treatmentof choice where teeth adjacent to anedentulous space are minimally or notrestored

This first article details the historyadvantages indications and designs ofresin-retained bridges

KEY WORDS DENTURE PARTIAL FIXED RESIN-BONDED DENTAL BONDING RESIN CEMENTS TOOTH PREPARATION PROSTHODONTIC copy PRIMARY DENTAL CARE 20029(3)87-91

G St George BDS MSc FDS DGDP(UK)Specialist Registrar in Restorative Dentistry

K Hemmings BDS MSc MRD FDSConsultant in Restorative Dentistry

K Patel BDS MSc FDS(Rest Dent)Consultant in Restorative Dentistry

Eastman Dental Hospital London UK

RESTORATIVE DENTISTRY AND PRIMARY DENTAL CARE

PRIMARY DENTAL CARE JULY 2002 87

Figure 1 A resin-retained bridge replacing

2 2 which has remained in place for seven

years without de-cementing

Figure 2 Rochette bridge

the margins Poor castings werecommon with this technique

Acrylic beads 10 Acrylic beads(02-03 mm) were placed on thefit surface of the retainer wingswhich were then duplicated inthe casting to produce mech-anical retention

Virginia sal t technique11 Saltcrystals (015-025 mm) wereincorporated into wax and re-moved in solution leaving cubicretentive pits This was a timesaving method compared to thetechnique of etching Theevaluation of the retent ivesurface was easier and agreater choice of non-etch-able metals could be used Acommercial product CrystalBond which was a com-bination of salt and acrylicbeads used to produce pitsand retentive beads on thefit surface of retainers wasproduced

All the above techniques re-quired thickening of the retain-ers to incorporate the retentivesystem used and were poorlyretained at their margins due tothe retentive feature stopping shortof the retainer edges

Micro-mechanical retention

Etching This has been carried outby electrochemical12 and chemi-cal methods13 The electrochemi-cal etching technique developedat the University of Marylandgave rise to the name lsquoMarylandBridgersquo The tiny etching patternproduced was verified by exami-nation under a microscope toensure it was adequate Bondstrengths were good but difficul-ties in calculating times for elec-trochemical etching the hazardsof chemical etching and produc-ing uniform etch patterns14 led tothe use of other methods

Sandblasting This technique used50 micro alumina to produce a rough-ened oxide layer over the surface(Figur e 3) Sandblas ted basemetals have been shown to givehigher bond strengths than etch-ing or using salt particles15 espe-cially when the metal used had

an oxide coating and was usedwith a chemically active resin16

Chemical bonding

Tin coating17 The fit surfaces weretin coated electrochemicallyNoble metals were mainly usedrather than non-precious alloysLittle data was available to showsuccess rates and the techniquewhen applied to sandblas tednickel-chrome failed to improvebond strengths when compared tosandblasting alone18

S i l ane coa t ing 1 9 S i l i c a wasattached to metal surfaces byvaporising silane in a propaneair flame followed by a furthercoating of silane when the metalhad cooled Although promisinglittle clinical data is available

MetalsMetals used in the construction ofresin-retained bridges should pos-sess the following qualities

Rigidity Base metal alloys havehigher rigidity and hardness thannoble metal alloys This makesthem ideally suited to being usedin thin section resulting in lessbulky retainers Possible disad-vantages include greater wear ofopposing natural teeth difficultyin adjusting the finished metaland the inability to burnish mar-gins to optimise retainer fit

Accurate when cast Noble metalalloys melt at lower temperaturesthan base metal alloys and there-fore shrink less on cooling

Biocompatible Gold alloys are

biocompat ib le whereas baseal loys such as nickel-chromemay cause hypersensi tivity reac-tions20 Beryllium was originallyadded to nickel-chrome as it pro-duced a superior pattern whenetching was employed Howeverit is no longer used due to itsknown carcinogenic potential21

and the availability of alterna-tives to etching

Good bonding to porcelain andres in Gold al loys have beenshown to bond to porcelain well

but the greater thick-ness of oxides presentfollowing the heating ofbase metal alloys canbe more prone to failcohesively resu l t ingin porce lain fracture

Aesthetics Base metalalloys may cause grey-ing of anterior teethdue to meta l sh ine-through although thishas been reduced tosome degree by theuse of opaque cements

Low cost Base metalalloys are cheaper than

noble metal alloys hence theirwidespread use

The original Rochette bridge wasconstructed from type IV gold butthe majo ri t y o f res in- re t a inedbridges made today use a beryl-lium-free nickel-chrome alloy as asuperior material for frameworks

CementsResin cements have been used forthe cementation of resin-retainedbridges to etched enamel sinceRochette cemented his periodontalsplint using Sevriton (self-curedacrylic resin)

Acrylic resin had the followingproblems

Low compress ive and tensi lestrength

High solubility

Polymerisation shrinkage

Thermal expansionThese problems were largely over-come by the introduction of bisGMA type composite resins usedto cement the original Rochettebridges

RESIN-RETAINED BRIDGES RE-VISITED PART 1

88 PRIMARY DENTAL CARE JULY 2002

Figure 3 Electron micrograph of sandblasted retainer surface

With new methods of increasingretention of frameworks came bet-ter composite resins with smallerfiller particles and better flow prop-erties The first true breakthroughwas the development of the adhe-sive 4-META (4-methacryloxyethyltrimellitate anhydride) which wasincorporated into the dental cementSuper Bond C amp B Although ini-tially successful it was found thatthe high bond strengths obtaineddec re a sed ove r t ime when im -mersed in water and followingthermal cycling22

The development of Panavia-Exwhich contained phosphate mono-mers led to predictable bondingwhich overcame the problems ofSuper Bond C amp B Adhesion oc-cur red between the phosphategroup in the monomer and theoxide coating of the nickel-chromeand also via mechanical bonding23

A study24 carr ied out with th iscement showed that it may be pos-sible to bond strongly to nickelchromium with little or no prepara-tion of metal surfaces This led tothe introduction of sandblasting incombination with adhesive resincements to retain bridges This hassince been validated in other stud-ies1516 and has brought reliablebonding to resin-bonded bridges

Panavia-Ex has since been super-seded by Panavia 21 which is sup-plied as a two-paste system unlikePanavia-Ex which was a powderand liquid It contains 10-metha-cryloyloxydecyl di-hydrogen phos-phate which produces a strong bondto metal Both types of Panavia arechemical-cured materials

Advantages andDisadvantages ofResin-retainedBridges

Advantages Conservative Retention does not

rely on conventional retentivefeatures so little if any toothpreparation is necessary Whenp repa ra t ion i s requ i red th i sshould be restricted to enamel

Reversible Providing there is littleor no tooth prepara t ion thebridges can be removed with min-imal damage to the abutmentsThis feature is helpful when thistype of bridge is used as an in-terim restoration in the young egprior to implant therapy

Cheap and quick Laboratory billsare reduced as well as chair-time

Easy to do Impressions a jawregistration and a shade are oftenall that is needed

Patient preference due to re-duced chair-time cost and lack oftooth preparation

Cost-effective A recent study hasshown the median survival ofresin-retained bridges to be sevenyears and ten months25 Creugersand Kayser (1992)26 consideredresin-retained bridges to be cost-effective if their median survivalwas greater than 65 years

Potential disadvantages More frequent de-bond when

com p a r e d t o c o n v e n t i o n a lbridges

Resin-retained bridges have anundeserved reputation for failurepartly brought about by poorbridge design and cementationtechnique If de-cementat ionoccurs it is often easy to re-

cement the same bridge Whenmultiple retainers are used oneretainer may de-bond leaving thebridge in situ Plaque may trapunderneath this de-bonded re-tainer which can result in cari-ous destruction if undetected(Figure 4) This problem is notunique to resin-retained bridges

Technique sensitive Resin-re-tained bridges require carefuldesign and adequate isolation for

cementation using rubber damapplication

Aesthetics Problems can occurwith incisa l shine- through ofmetal if an opaque cement is notused An opaque cement lute mayalso be more visible Retainers ifextending onto occlusal or incisalsurfaces may a lso be visib leThese can be masked by abradingthe retainer surfaces with glassbeads The matt finish producedand lack of reflection makes themetal surfaces disappear into thedarkness of the mouth

Redistribution of space Whendiastemas are present or ponticspace is too large or small it isoften difficult to distribute thespace between pontic and abut-ment teeth Cantilever or springcantilever designs may be con-sidered in these cases

Limited tooth replacement Smallspans tend to be more successfulthan larger ones

Temporisationtrial prosthesis isnot usually possible This pre-vents eva luation of aestheticsgu idance and speech Whenbridges are temporarily cementedre-preparation of both tooth andretainer fit surfaces is necessary

Dramatic failure A partial denturecan be made simultaneously torestore function if there is dra-matic failure of the resin-retainedbridge

Poor remuneration This treat-ment can be well rewarded inthe private sector but remunera-tion is poor under the NationalHealth Service This combinedwith scepticism about successfrom many practitioners has ledto their limited use in generaldental practice

Indications andContra-indicationsIndications Un-restoredminimally restored

teeth The highest bond strengthsa re obta ined when meta l i sbonded to enamel M inimalexposure of dentine or the pres-ence of fillings are not absolutecontra-indications Restorations

G ST GEORGE ET AL


Figure 4 Carious destruction under a de-

cemented bridge

on abutment teeth should becomposite resin and require re-placement prior to taking the im-pressions for bridge construction

Sufficient good quality enamelToothwear (Figure 5a) diminu-tive teeth (Figure 5b) and certainabnormalities of enamel eg amel-ogenesis imperfecta may reducethe quantityquality of enamelfor bonding and therefore thestrength of the adhesive bond

Sufficient inter-occlusal spacefor retainers exists Lack of in-ter-occlusal space can be over-come by cementing restorationslsquohighrsquo at an increased occlusalvertical dimension similar to theappliance developed by Dahl27

Occlusal contacts between theremaining teeth are usually re-stored in a few months in ayoung pa t i en t and s l i gh t l ylonger 9-12 months in an olderpatient Bridges cemented thisway spare enamel have beenshown to be well tolerated andhave good retention rates25 Thisis the preferred method of theauthors and is indicated in mostclinical situations apart fromu Teeth with little periodontal

support or increased mobilitySplaying of abutment teethmay occur rather than in-t rus ion and compensatoryeruption of the remainingteeth Rotation of abutmentsmay occur when canti leverbridges are cemented high onthese teeth

u Patients with a large horizon-tal slide from their retrudedcontact position to their inter-cuspal position Posterior re-positioning of the mandiblemay occur in these patients

resulting in anterior guidancebeing lost Luckily these casesare rare in clinical practice

u lsquoOcclusally-awarersquo patientsThe harmony in some patientsrsquomouths can be upset by theplacement of high retainersAgain these patients are rarePatients should be warned thatchewing food may be diffi-cult until tooth contacts arerestored

Where a resin-retained bridge isan intermediate prosthesis (priorto implants) This is very usefulduring growth years when im-plants are contra-indicated

Patien t wishes Some patientsare reluctant to have minimallyrestored teeth prepared

Contra-indications Heavi l y res tored t ee th Th is

reduces the area of enamelbonding

Little enamel to bond to Despitethe recent advances in dentinebonding one s ti ll pre fers tobond mainly to enamel

Poor quali ty enamelf requentde-bonds

Translucent incisa l edges ofabutment tee th These a l lowshine-through of metal retainers(Figure 6) This may be min-

imised by the use of opaquecements

Excessive occlusal loading De-bonding may occur when oc-clusal contacts are present onthe pontics in excursive move-ments

Difficulty in isolation for cemen-tation to achieve a dry field

Bridge DesignThere are three possible designsbased on retainer type and con-nectors

Cantilever (Figure 7)Using a single retainer eliminatesthe problems of partial de-cemen-ta tion as the pat ientdent ist isinstantly aware of bond failureThis may be seen as a disadvantagebecause of the dramatic failure Acareful occlusal analysis is requiredto avoid heavy contac t on thepont ic especia l ly on excurs ivemovements which could precipi-tate an early failure

A can t i l ever br idge is l essexpensive than a fixed-fixed resin-reta ined bridge but l imited toreplacing one missing tooth Adiagnostic wax-up should revealany contacts in excursive move-ments which may cause eitherbond failure or tooth rotation Iforthodontic stability of teeth adja-cent to the space is required thisdesign may be inappropriate

Fixed-fixed (Figure 8)With fixed-fixed bridges one ormore retainers are placed on eithers ide of the pont i c D if fe rent ia lmovement of abutments can resultin bond failure but this can bereduced by making sure opposingteeth only contact retainer wingsand not tooth tissue in excursive



Figure 7 A cantilever bridge

Figure 5 (a) Potential abutments showing erosion (b) Reduced bonding area on diminu-

tive lateral incisors

Figure 6 lsquoShine-throughrsquo of a metal retainer

through a lateral incisor

contacts thereby biting the abut-ments out of the retainer Doubleabutments offer no advantages interms of retention as the weakerabutment retainers are often putunder shear forces causing de-bonding This can make mainte-nance d i f f i cul t Long spans egr e p l a c i n g 2 1 1 2 u s i n g 3 3 a ste rminal abutments have beenshown to be successful 25 Thisdesign of bridge is indicated whereexcursive movements on ponticscannot be avoided tooth stabilityis required following orthodonticmovement and lack of periodontalsupport could produce abutmentmovement

Hybrid bridges (Figure 9)This design has both resin-retainedand conventional retainers Theyare indicated where one of theabutments is minimally restoredand a resin-bonded retainer is used

at this site to conserve tooth tissueLaboratory bills are increased andcare should be taken in the locationof the connectors to ensure thatdrifting apart of the joint does notoccur The male part of the joint isoften attached to the resin-bondedretainer to simplify maintenancewhen de-bonds occur as the resin-retained part of the bridge invari-ably fails before the conventionalretainer It also enables optimalseating

References1 Buonocore MG A simple method of

increasing the adhesion of acrylic fillingmaterials to enamel surfaces J Dent Res195534849-53

2 Bowen RL Properties of a silica reinforcedpolymer for dental restorations J Am DentAss 19636657-64

3 Ibsen RL Fixed prosthetics with a naturalcrown pontic using an adhesive compositeCase history J South Calif Dent Assoc197341100-2

4 Portnoy L Constructing a composite ponticin a single visit Dent Surv 19734920-3

5 Simonsen RJ Clinical Applications of theAcid Etch Technique Chicago Quintessence1978

6 Rochette AL Attachment of a splint toenamel of lower anterior teeth J ProsthetDent 197330418-23

7 Howe DF Denehy GE Anterior fixed partialdentures utilising the acid-etch techniqueand a cast metal framework J Prosthet Dent19773728-31

8 Swift EJ New adhesive resins A statusreport Am J Dent 19892358-60

9 Taleghani M Leinfelder KF Taleghani AMAn alte rnat ive to cast etched retainers J Prosthet Dent 198758424-8

10 L aBa r re EE Wa rd HE An a l t e r nat i veresin-bonded restoration J Prosth Dent198452247-9

11 Hudgins JL Moon PC Knap FJ Particleroughened res in-bonded re ta iners JProsthet Dent 198553471-6

12 Livaditis GJ Thompson VP Etched cast-ings an improved retentive mechanismfor resin-bonded retainers J Prosthet Dent19824752-8

13 Livaditis GJ A chemical etching system forcreating micro-mechanical retention inresin bonded retainers J Prosthet Dent198656181-8

14 Lyttle HA Louka AN Young J A study ofthe consistency of etch patterns on samplesof various alloys as fabricated by commer-cial dental laboratories [abtract 11] J DentRes 198665532

15 Harley KE Ibbetson RJ The adhesivestrengths of three resin cements used withberyllium free nickel chrome alloy [BSDRabstract 9] J Dent Res 198766835

16 Atta MO Smith BGN Brown D Bondstrengths of three chemical adhesive cementsadhered to a nickel-chromium alloy fordirect bonded retainers J Prosthet Dent199063137-43

17 Van Der Veen JH Krajenbrink T BronsdijkAE Van De Poel F Resin bonding of tinelectroplated prec ious metal fixed par-t ia l dentures one year clinical resultsQuintessence Int 198617299-301

18 Asfour D Wickens J A comparison of twomethods for surface treatment of nickel-chrome alloys [BSDR abstract 152] J DentRes 198968577

19 Musil R Tiller HJ The Adhesion of DentalResins to M eta l Sur faces The K ul ze rSilicoater Technique Wehreim Kulzer amp CoGmbH 1984

20 Moffa JP Beck WD Hoke AW Allergicresponse to nickel containing dental alloys[AADR abstract 107] J Dent Res 197756B78

21 Moffa JP Jenkins WA Status report onbase-metal crown and bridge alloys J AmDent Assoc 197489652-5

22 Thompson VP Grolman KM Liao RBonding of adhesive resins to various non-precious alloys [IADR abstract 1258] J DentRes64314

23 Yamashita A Yamami T Proceedings of theInternational Symposium on Adhesive Pros-thodontics Nijmegen Eurosound DrukkerijB 198661-76

24 Jenkins CBG Aboush YEY The bondstrength of a new adhesive recommendedfor resin-bonded bridges [BSDR abstract18] J Dent Res 198564664

25 Djemal S Setchell D King P Wickens JLong-term survival characteristics of 832resin-retained bridges and splints providedin a pos t-graduate teaching hospitalbetween 1978 and 1993 J Oral Rehabil199926302-20

26 Creugers NH Kayser AF An analysis of mul-tiple failures of resin-bonded bridges JDent 199220348-51

27 Dahl BL Krogstad O Karlsen K An alterna-tive treatment in cases with advanced local-ized attrition J Oral Rehabil 19752209-14

Proprietary namesSevriton De Trey Division Dentsply LtdWeybridge Surrey UK

Super Bond C amp B Ventura Oral Systems LtdHalifax Yorkshire UK

Panavia-Ex and Panavia 21 Kuraray Co Ltd 1-12-39 Umeda Kita Ku Osaka 530-8611 Japan

G ST GEORGE ET AL


Figure 8 Fixed-fixed bridges

Figure 9 A hybrid bridge

New CDO AppointedThe Department of Health announced the appointment of Professor Raman

Bedi to the post of Chief Dental Officer for Engla nd on 17th May 2002

Professor Bedi is presently Head Department of Transcultural Oral Health

Eastman Dental Institute Professor of Transcultural Oral Health University

College London Co-Director WHO Collaborating Centre for Disability Culture

and Oral Health He qualified at the University of Bristol in 1976 He has held

academic posts at the Universities of Manchester Hong Kong Edinbur gh

and Birmingham He is a specialist in both dental public health and paediatric

dentistry The Faculty welcomes Professor Bedirsquos appointment at a crucial time

for the profession Professor Bedi has worked closely with the Faculty in the

past and we share his views on oral health equality issues

Correspondence G St George ConservationDepartment Eastman Dental Hospital 256 Grayrsquos Inn Road London WC1X 8LD E-mail gstgeorgeeastmanuclacuk

the margins Poor castings werecommon with this technique

Acrylic beads 10 Acrylic beads(02-03 mm) were placed on thefit surface of the retainer wingswhich were then duplicated inthe casting to produce mech-anical retention

Virginia sal t technique11 Saltcrystals (015-025 mm) wereincorporated into wax and re-moved in solution leaving cubicretentive pits This was a timesaving method compared to thetechnique of etching Theevaluation of the retent ivesurface was easier and agreater choice of non-etch-able metals could be used Acommercial product CrystalBond which was a com-bination of salt and acrylicbeads used to produce pitsand retentive beads on thefit surface of retainers wasproduced

All the above techniques re-quired thickening of the retain-ers to incorporate the retentivesystem used and were poorlyretained at their margins due tothe retentive feature stopping shortof the retainer edges

Micro-mechanical retention

Etching This has been carried outby electrochemical12 and chemi-cal methods13 The electrochemi-cal etching technique developedat the University of Marylandgave rise to the name lsquoMarylandBridgersquo The tiny etching patternproduced was verified by exami-nation under a microscope toensure it was adequate Bondstrengths were good but difficul-ties in calculating times for elec-trochemical etching the hazardsof chemical etching and produc-ing uniform etch patterns14 led tothe use of other methods

Sandblasting This technique used50 micro alumina to produce a rough-ened oxide layer over the surface(Figur e 3) Sandblas ted basemetals have been shown to givehigher bond strengths than etch-ing or using salt particles15 espe-cially when the metal used had

an oxide coating and was usedwith a chemically active resin16

Chemical bonding

Tin coating17 The fit surfaces weretin coated electrochemicallyNoble metals were mainly usedrather than non-precious alloysLittle data was available to showsuccess rates and the techniquewhen applied to sandblas tednickel-chrome failed to improvebond strengths when compared tosandblasting alone18

S i l ane coa t ing 1 9 S i l i c a wasattached to metal surfaces byvaporising silane in a propaneair flame followed by a furthercoating of silane when the metalhad cooled Although promisinglittle clinical data is available

MetalsMetals used in the construction ofresin-retained bridges should pos-sess the following qualities

Rigidity Base metal alloys havehigher rigidity and hardness thannoble metal alloys This makesthem ideally suited to being usedin thin section resulting in lessbulky retainers Possible disad-vantages include greater wear ofopposing natural teeth difficultyin adjusting the finished metaland the inability to burnish mar-gins to optimise retainer fit

Accurate when cast Noble metalalloys melt at lower temperaturesthan base metal alloys and there-fore shrink less on cooling

Biocompatible Gold alloys are

biocompat ib le whereas baseal loys such as nickel-chromemay cause hypersensi tivity reac-tions20 Beryllium was originallyadded to nickel-chrome as it pro-duced a superior pattern whenetching was employed Howeverit is no longer used due to itsknown carcinogenic potential21

and the availability of alterna-tives to etching

Good bonding to porcelain andres in Gold al loys have beenshown to bond to porcelain well

but the greater thick-ness of oxides presentfollowing the heating ofbase metal alloys canbe more prone to failcohesively resu l t ingin porce lain fracture

Aesthetics Base metalalloys may cause grey-ing of anterior teethdue to meta l sh ine-through although thishas been reduced tosome degree by theuse of opaque cements

Low cost Base metalalloys are cheaper than

noble metal alloys hence theirwidespread use

The original Rochette bridge wasconstructed from type IV gold butthe majo ri t y o f res in- re t a inedbridges made today use a beryl-lium-free nickel-chrome alloy as asuperior material for frameworks

CementsResin cements have been used forthe cementation of resin-retainedbridges to etched enamel sinceRochette cemented his periodontalsplint using Sevriton (self-curedacrylic resin)

Acrylic resin had the followingproblems

Low compress ive and tensi lestrength

High solubility

Polymerisation shrinkage

Thermal expansionThese problems were largely over-come by the introduction of bisGMA type composite resins usedto cement the original Rochettebridges



Figure 3 Electron micrograph of sandblasted retainer surface



























G ST GEORGE ET AL



cemented bridge
































































G ST GEORGE ET AL










































G ST GEORGE ET AL



cemented bridge
































































G ST GEORGE ET AL















































































G ST GEORGE ET AL
















resin-retained bridges re-visited part 1. history and ... bridges part 1.pdf · resin-retained...

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