Amalgam repair

Amalgam repair

Boondarick Niyatiwatchanchai

Tuesday, August 13, 13

Replacement of restoration



• secondary caries

• marginal defect

• cusp fracture




• marginal defect

• cusp fracture




• marginal defect

• cusp fracture




• marginal defect

• cusp fracture




• marginal defect

• cusp fracture


Replace or repair


Replace or repair

• loss of dental tissue

• increasing preparation/restoration size

• cost

• time consuming

• technically difficult

• Potentially damage to pulp


Replace or repair

• loss of dental tissue

• increasing preparation/restoration size

• cost

• time consuming

• technically difficult

• Potentially damage to pulp


Benefit of repair• more conservative of tissue

• reduce risk of iatrogenic damage

• reduce need for the use of local anesthesia

• oppotunity to enhanced patient experience

• saving in time and resources

• esthetic


Benefit of repair• more conservative of tissue

• reduce risk of iatrogenic damage

• reduce need for the use of local anesthesia

• oppotunity to enhanced patient experience

• saving in time and resources

• esthetic


Resin composite as repair material

• interfacial bond between amalgam and resin composite

• strengthening of the tooth-material interface

• veneering of amalgam for esthetic


Development in adhesive technology

• Improve sealing quality of amalgam repair


Still controversy

• still in wide range of result attributed to various factors ex time , interface , effect of roughening , type of alloy



Aim of the study

• to assessed the repair quality of amalgam restorations at the amalgam-resin and resin tooth interfaces

• using different

• 1) surface finishing methods

• 2) adhesive systems


Methods and materials

• 55 caries-free intact human molars

• stored in distilled water

• clean and polished with pumice and rubber cup for 10 sec

• occlusal cavity preparation using high speed hand piece with air/water spray


• Average facio-lingual width of cavies was approximately one-third of intercuspal width and 3 mm depth

• restored with high copper , microfine lathe-cut amalgam(Cavex Avalloy)

• stored in distilled water for 24 hrs

• thermo cycling in deionized water

• remove mesial and distal parts of the cavities

• one side was finished with a coarse diamond bur while the other was finished with fine diamond bur

• divided into 5 groups( n=10/group) to receive the following adhesive system


• Group 1: All Bond 3 (BISCO, Inc, Schaumburg, IL, USA) (dual cure, etch&rinse adhesive system)

• Group 2: Clearfil SE Bond+Alloy Primer (Kuraray, Okayama, Japan) (self-etch adhesive system with alloy primer)

• Group 3: Kuraray DC Bond (Kuraray) (dual-cure, self-etch adhesive system)

• Group 4: Xeno V (Dentsply DeTrey, Konstanz, Germany) (one-step, self-etch adhesive system)

• Group 5: XP Bond (Dentsply DeTrey) (etch&rinse, self-priming adhesive system)

All of the cavities were restored with resin composite (TPH Spectrum, Dentsply DeTrey) and light polymerized with a halogen light of 500 mW/cm2 intensity



• Thermocycled again

• immersed in 0.5 basic fuchsin soluion 24 hr

• rinsing with distilled water

• embedded in epoxy resin

• sectioned mesiodistally with a slow speed diamond saw

• digitally photographed

• data analyzed with one-way ANOVA and poist hoc Tukey test


Result

• All the groups exhibited microleakage between the amalgam-resin interface and the tooth-resin interface















Result

• there was no difference among each region when using all bond 3

• no statistical difference between the microleakage values of surfaces with either course or fine finish(p>0.05)

• amalgam-resin surfaces exhibited statistically more microleakage than tooth-resin surfaces for the other adhesive systems




DISCUSSION

• Amalgam comprises about 40% of the restoration being replaced with a median age of 12-15 years

• A successful technique for the repair would be advantageous conservative


Alternative options for defective amalgam restoration

• Rapairing

• Sealing

• Refurbishing


DISCUSSION

• Replacing ditched amalgam restorations with other similar restorations resulted in significant dental structure loss

• Previous studies report on 40%-70% bond strength archieved from amalgam-to-amalgam repair

• The trend of minimally invasive dentistry


DISCUSSION

• In Vivo studies related to the repair of amalgam indicate a significant impact on the improvement of clinical performance of amalgam restoration with minimal intervention


Important factor

• Interfacial bond between the joined surfaces

• clean surfaces , roughening amalgam , adhesive for metallic


Microleakage test

• useful methods for evaluating sealing performance of adhesive systems

• image analysis to obtain quantitative results


Effect of roughening

• Jessup and Vandewalle report improved bond strengths after roughening with carbide burs

• Hadavi and others report similar result using carbide burs and diamond burs

• However the results of the current in vitro study could not correlate microleakage and surface roughness of the joined surfaces


Use of bonding agent

• Robert and others found the use of a bonding agent did not improve the degree of protection against microleakage

• Ozer and others found significant improvement in microleakage especially amalgam-resin interface


Bonding systems

• Etch and rinse

• Self etch


Etch and rinse• Phosphoric acid etching of enamel and

dentin

• weak zone of uninfiltrated dentin

• hydrolytic degradation of collagen


Self etch

• increasing popularity

• reduces application time and technique sensitivity

• prevent hydrolytic degradation of bond

• debate on efficacy of bonding to enamel


In this study

• Total etch performed significantly better than self etch

• alloy primer did not significantly improve sealing in the restoration comolex


All bond 3

• Hydrophobic , radiopaque-filled bonding resin and also HEMA-free

• less prone to water sorption

• Hydrophobic adhesives are expect to be more durable


• Better performance of etch and rinse systems may also be related to micromechanical interlocking of the resin system to acid etched surfaces

• However additional roughening with coarse bur did not facilitate bonding both in amalgam and tooth surface


Conclusion

• In term of preventing microleakage etch and rinse adhesive may be preferred for amalgam repair

• The use of coarse versus fine diamond for preparation did not impact microleakage



Primary Aim

• To evaluate the effects of different amalgam conditioning methods on the tensile bond strength between amalgam and a nanohybrid resin composite restorative material , using various intraoral restoration repair systems

• Study the nature of interfacial bond failure , using electron microscope


Null Hypothesis

• There was no statistical difference in repair bond strengths between the various repair protocols


Material and methods

• Specimen preparation

• 160 PMMA retention bases were prepare containing a central recess(width 5mm , height 5mm , depth 4mm)

• cavity of 2mm diameter and 2mm depth was prepared at the base

1. Introduction

Replacement of defective amalgam restorations accounts for a

substantial part of activity performed in general dentalpractice.1–3 The main reasons for replacement include second-ary caries, marginal defects, inadequate marginal integrity orinadequate interproximal contact.4,5 Another common reasonfor amalgam replacement is partial or complete cusp fractureadjacent to, or involving, the amalgam restorations.6,7

Previous studies indicate that complete cusp fracture inteeth restored with amalgam restorations is a relativelycommon observation in clinical practice and particularly sofor posterior teeth restored with extensive amalgam restora-tions.7–9 The prevalence of complete cusp fracture in amal-

gam-restored premolar and molar teeth has been reported torange between 4–8% and 5–15%, respectively.10–13 The majorityof cusp fractures are observed in, and limited to, the supra-gingival location, which suggests that the fractured tooth isamenable to restorative procedures.12 Various factors maycontribute to cusp fracture of amalgam-restored teeth,including lack of adhesion of amalgam to tooth structures,thereby providing no significant change in the fractureresistance of the cusps14 or in the amount of cuspal flexure15

relative to equivalent unrestored teeth. These factors may becompounded by the presence of undermined cusps, extensive

restoration size, parafunctional activity, impact load, fatigueload, and occlusal disharmony.9

The traditional approach to the management of cuspfractures in teeth which have been restored with amalgam hasbeen either total restoration replacement resulting in moreextensive direct restorations, or preparation for indirectrestorations. Both of these procedures result in increasedpreparation and restoration size.16 This approach has beenreferred to as the ‘repetitive restoration cycle’17 and can resultin the progressive weakening of the tooth through unneces-sary removal of sound tooth tissue, detrimental effects on thedental pulp, together with potential damage caused to

adjacent teeth.18

Whilst some amalgam restorations with adjacent cuspfracture, notably those associated with an extensive second-ary caries lesion, will inevitably require replacement, it may besuggested that some amalgam restorations with adjacent cuspfracture may be given extended longevity through repairprocedures (i.e. cusp replacement with or without partialreplacement of the amalgam restoration, allowing preserva-tion of that portion of the restoration that presents no clinicalor radiographic evidence of failure). This more conservativeminimally invasive approach to the management of cusp

fracture adjacent to or involving the amalgam restoration,offers many advantages, including:

! more conservative of tooth tissue,! reduced risk of iatrogenic damage,! reduced need for the use of local anaesthesia,! opportunity for enhanced patient experience,! savings in time and resources.

In contrast to amalgam repair procedures using bondedamalgam, the use of resin composite as a repair material

provides additional aesthetic and structural benefits. This isattributable to the improved appearance owing to veneering ofthe amalgam with tooth-coloured restorative material, andadhesion of the resin composite to remaining tooth tissue,

resulting in strengthening of the tooth–material interface.19

An important aspect related to the quality of amalgam repairis the quality of the interfacial bond between amalgam andresin composite repair material. In consideration of continuousadvances in adhesive and resin composite material technologyas well as the drive towards the principles of minimally invasivedentistry, a growing number of commercially available intra-oral restoration repair systems for the direct veneering ofamalgam have been introduced to the market. However, despitethe ever increasing number of these repair systems, theliterature is sparse regarding the best protocol for performing

an amalgam repair using resin composite.The primary aim of this in vitro study was to evaluate the

effects of different amalgam surface conditioning methods onthe tensile bond strength between amalgam and a nanohybridresin composite restorative material, using various intra-oralrestoration repair systems. The secondary aim was to thenature of interfacial failure, using scanning electron micros-copy (SEM) and profilometry examinations of failed interfacialsurfaces. The null hypothesis tested was that there was nostatistical difference in repair bond strengths between thevarious repair protocols.

2. Materials and methods

2.1. Specimen preparation

One hundred and sixty poly(methymethacrylate) (PMMA)retention bases (Mould 1) (VisionTek Systems Ltd., Chester,UK) were prepared containing a central recess (width 5 mm,height 5 mm, depth 4 mm). A cavity of 2 mm diameter and2 mm depth was prepared at the base of this central recess, tofacilitate mechanical retention of the amalgam (Fig. 1). The

amalgam (non-gamma 2, lathe-cut, high-copper alloy with43% Ag, 25.4% Cu) (ANA 2000 Duet, Nordiska Dental AB,Angelholm, Sweden) was triturated according to the manu-facturer’s instructions and then condensed with a handinstrument into the recess within the PMMA base. Specimens

Fig. 1 – Custom made retention base (Mould 1).

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 1 5 – 2 116


• Triturated amalgam(non gamma2 , lathe-cut, high copper)

• condensed with a hand instrument into the recess within the PMMA base

• Allow to set for 24 h

• polished with a wet 1200-grit silicon carbide disc at 300 rpm for 30s and cleaned for 10 min in ultrasonic bath

• Air-dried for 24 h

• stored in artificial saliva for 2 weeks to present an aging process


Surface conditioning method

• Divided into 8 groups , each containing 20 specimen


1 Group 1: Air-borne particle abrasion with 50 mm Al2O3 (Korox R, Bego, Bremen, Germany) using an intraoral sandblaster (Dento-PrepTM, RØNVIG A/S, Daugaard, Denmark) from a distance of 10 mm at a pressure of 2.5 bar for 4 s followed by application of Alloy primer (Kuraray, Japan) and Panavia 21 (Kuraray, Japan).

2 Group 2: Air-borne particle abrasion as for group 1 followed by application of Amalgambond Plus (Parkell, USA).

3 Group 3: Air-borne particle abrasion as for group 1 followed by application of ALL-BOND 3 (Bisco, USA).

4 Group 4: Surface roughening with a diamond bur (Classic Diamond #521M, Dental Directory, Essex, UK) for 10 s and application of Alloy primer (Kuraray, Japan) and Panavia 21 (Kuraray, Japan).

5 Group 5: Diamond bur roughening as for group 4 followed by application of Amalgambond Plus (Parkell, USA). Group

6 6: Diamond bur roughening as for group 4 followed by application of ALL-BOND 3 (Bisco, USA)

7 Group 7: Silica coating with 30 mm SiO2 particles using an intra-oral sandblaster (3M ESPE, Germany) from a distance of 10 mm at a pressure of 2.5 bar for 4 s followed by application of the corresponding silane and bonding agents (ESPE-Sil and Visio-bond) of the CoJet System (3M ESPE, Germany)

8 Group 8 (control group): No surface conditioning and no adhesive system was used.


were allowed to set for 24 h at 23.0 ! 1.0 8C and weresubsequently polished with a wet 1200-grit silicon carbidedisc (Struers RotoPol 11, Struers A/S, Rodovre, Denmark) at300 rpm for 30 s and cleaned for 10 min in an ultrasonic bath(Quantrex 90 WT, L&R Manufacturing Inc., Kearny, NJ, USA)containing deionised water to eliminate possible contami-nants. All specimens were then air-dried (23.0 ! 1.0 8C) for 24 hand subsequently stored in artificial saliva for 2 weeks at37.0 ! 1.0 8C to represent an ageing process.

2.2. Surface conditioning methods

The PMMA/amalgam specimens were randomly divided intoeight groups, each containing 20 specimens to receive thefollowing surface conditioning treatments according to themanufacturers’ instructions:

" Group 1: Air-borne particle abrasion with 50 mm Al2O3 (KoroxR, Bego, Bremen, Germany) using an intraoral sandblaster(Dento-PrepTM, RØNVIG A/S, Daugaard, Denmark) from adistance of 10 mm at a pressure of 2.5 bar for 4 s followed byapplication of Alloy primer (Kuraray, Japan) and Panavia 21

(Kuraray, Japan)." Group 2: Air-borne particle abrasion as for group 1 followed

by application of Amalgambond Plus (Parkell, USA)." Group 3: Air-borne particle abrasion as for group 1 followed

by application of ALL-BOND 3 (Bisco, USA)." Group 4: Surface roughening with a diamond bur (Classic

Diamond #521M, Dental Directory, Essex, UK) for 10 s andapplication of Alloy primer (Kuraray, Japan) and Panavia 21(Kuraray, Japan)." Group 5: Diamond bur roughening as for group 4 followed by

application of Amalgambond Plus (Parkell, USA).

" Group 6: Diamond bur roughening as for group 4 followed byapplication of ALL-BOND 3 (Bisco, USA)." Group 7: Silica coating with 30 mm SiO2 particles using an

intra-oral sandblaster (3M ESPE, Germany) from a distanceof 10 mm at a pressure of 2.5 bar for 4 s followed byapplication of the corresponding silane and bonding agents(ESPE-Sil and Visio-bond) of the CoJet System (3M ESPE,Germany)." Group 8 (control group): No surface conditioning and no

adhesive system was used.

The description, composition and manufacturers of theintra-oral adhesive repair systems used in this study aresummarised in Table 1.

2.3. Repair resin composite application

An additional 160 PMMA retention bases, were prepared andused for the resin composite application procedure (Mould 2).These PMMA bases contained a recess for the resin compositematerial. Mould 2 was placed onto the surface of conditionedamalgam specimens (Mould 1) (Fig. 2). A nanohybrid resin

composite material (NANOSITTM, Nordiska Dental AB, Angel-holm, Sweden) was packed against the amalgam with acomposite-filling instrument in 2 mm increments and poly-merised with a standardised visible light curing unit (Smartli-teTM PS, Dentsply, Germany) for 40 s, operating at a measuredoutput of 680 mW/cm2 intensity (Fig. 3). All surface treatmentand repair procedures were performed by a single experiencedoperator in accordance with the manufacturers’ instructions.Following light polymerisation, all amalgam/resin compositespecimens were stored for 24 h at 23.0 ! 1.0 8C room temper-ature before being subjected to tensile bond strength testing.

Table 1 – Description, composition and manufacturers of the intra-oral adhesive repair systems and composite resinmaterial used in this study.

Material Material description Chemical composition Manufacturer

Alloy Primer +Panavia 21

Metal conditioning primer+ dual-cure adhesive system

Primer: 6-[(4-vinylbenzyl)propylamino]-l,3,5-itriazine-2,4-dithione (VBATDT),10-methacryloyloxydecyl dihydrogenphosphate (MDP adhesive monomer)Adhesive system: 10-methacryloyloxydecyldihydrogen phosphate, dimethacrylate,silica filler

Kuraray, Okayama, Japan

Amalgambond Plus Self-cure etch and rinseadhesive system

META (4-methacryloxyethyl trimellitateanhydride), bisphenol-A-dimethyacrylate,HEMA (hydroxyethyl methacrylate),ethylene glycol methacrylate

Parkell, Farmingdale, NY, USA

ALL-BOND 3 Dual-cure etch and rinse universaladhesive system

BisGMA (bisphenol-A-dimethyacrlate),urethane dimethacrylate, triethyleneglycol dimethacrylate, silica filler

Bisco, Inc. Schaumburg, IL, USA

CoJet-Sand Sand for coating substrate surface Aluminium trioxide particles coatedwith silica, particles size: 30 mm

3M ESPE AG, Seefeld, Germany

ESPE-Sil Silane coupling agent 3-Methacryloxypropyltrimethoxysilane,ethanol


Visio-bond Adhesive bonding agent Bisacrylate, aminodiol methacrylate,camphor-quinone, benzyl dimethylketale, stabilisers


NANOSITTM Nano-hybrid composite resinrestorative material

BisGMA (bisphenol-A-dimethyacrylate),HEMA (hydroethyl dimethacrylate),inorganic glass particles (57 vol%; 74 wt%),particle size: 2.0–0.2 mm

Nordiska Dental AB, Angelholm,Sweden

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Repair resin composite application

• An additional 160 PMMA retention base were prepared and use for the resin composite application procedure

• Mould 2 was placed onto the surface of conditioned amalgam specimen

• Pack nanohybrid composite against the amalgam in 2 mm increment

• Polymerized with light for 40 s


2.4. Tensile testing

The PMMA moulds retaining the amalgam–resin compositespecimens were mounted on a universal testing machine(Lloyd Instruments Ltd. Model LR5K, Hampshire, UK) fittedwith a 1 kN load cell, travelling at a crosshead speed

of 0.5 mm/min. A tensile force was applied until failureoccurred. The data were subjected to statistical analysisusing a one-way analysis of variance and post hoc Tukey’stest.

2.5. Failure analysis

The surfaces of three randomly selected specimens from eachtest group were examined under SEM to investigate thesurface morphology of the failed surfaces. The specimenswere sputter coated with a 15 nm layer of Pt/Pd to aidconductivity and examined using a Jeol JSM 5600 LV SEM (Jeol

Ltd., Japan) at an operating voltage of 15 kV in the secondaryelectron mode. Failures were classified as adhesive, cohesiveor mixed. Adhesive failure was defined as a completedebonding of the adhesive system from the treated amalgamsurface (adherent). Cohesive failure was defined as a fracturethat occurred in the resin composite and showed remnants ofbonding agent or resin composite on both sides. Mixed failure

was defined as a fracture that showed evidence of adhesiveand cohesive failures.

The failed surfaces of another three randomly selectedspecimens from each test group were examined under three-dimensional profilometry to examine the surface roughnessprofiles at the failed surfaces. The surface roughness profile

value (Ra-value) of amalgam specimens (n = 3) from each groupfollowing failure was determined using three-dimensionalprofilometry (ProScan-2000; Scantron Industrial Products, Ltd.,UK). Scanning was conducted over a 4.0 mm ! 3.0 mm areawith an x and y step-size of 0.01 and 0.10 mm and number ofsteps of 400 and 30, respectively.

3. Results

3.1. Bond strength

The results of the tensile bond strength tests are presented inTable 2.

The tensile strength of all of the specimens in the controlgroup (without mechanical and adhesive surface condition-ing) was zero (no adhesion).

Surface conditioning with alumina sandblasting and theuse of Alloy primer and Panavia 21 resulted in significantly

Fig. 2 – Custom made retention base (Mould 2) positionedover Mould 1 containing the surface conditioned amalgamspecimen surface conditioned amalgam specimen.

Fig. 3 – Resin composite packed into Mould 2 and packedagainst surface conditioned amalgam specimen inunderlying Mould 1. Amalgam specimen in underlyingMould 1.

Table 2 – Comparison of mean tensile bond strengths (TBS) and surface roughness values between repair protocols.

Surface conditioning method TBS (SD) [MPa] 95%confidence

intervals (MPa)

Statisticalgroupings

Ra-value(mm)

Group 1 Alumina sandblasting + Alloy Primer + Panavia 21 5.13 (0.96) 5.71–4.58 d 4.76Group 2 Alumina sandblasting + Amalgambond Plus 2.51 (2.73) 3.72–1.27 c 3.58Group 3 Alumina sandblasting + All Bond 3 2.42 (0.76) 2.87–1.99 a,b 2.35Group 4 Diamond bur + Alloy Primer + Panavia 21 3.42 (0.82) 3.78–3.09 b,c 16.56Group 5 Diamond bur + Amalgambond Plus 3.40 (1.68) 4.06–2.75 b,c 16.03Group 6 Diamond bur + All Bond 3 1.34 (0.71) 1.60–1.10 a 13.46Group 7 Silica coating (CoJet-system) 3.72 (1.00) 4.24–3.22 b,c 1.95

Lower case letters indicate statistically homogeneous groups. If two data sets share the same letter, they do not differ to a statisticallysignificant degree.











3. Results

3.1. Bond strength








intervals (MPa)


Ra-value(mm)





• store for 24 hrs at room temperature

• tensile stress testing using universal testing machine(Lloyd instruments Ltd.) fitted with a 1 kN load cell , travelling at a crosshead speed of 0.5 mm/min

• Apply force until failure occurred

• Data analysis using one-way analysis of variance and post hoc Tukey’s test


Failure analysis

• The surfaces of three randomly specimen from each group were examined under SEM

• Investigate the surface morphology of the failed surfaces

• Failures were classified as adhesives , cohesives or mixes


Failure analysis

• Adhesive failure a complete debonding of the adhesive system from the treated amalgam surface

• Cohesive failure was defined as a fracture that occurred in the resin composite and showed remnants of bonding agent or resin composite on both sides

• Mixed failure defined as a fracture that showed evidence of adhesive and cohesive failure


Result• Bond strength

• control group = 0 (no adhesion)

• Sandblasting and alloy primer and Panavia 21 resulted in significantly higher bond strength values than other











3. Results

3.1. Bond strength








intervals (MPa)


Ra-value(mm)




All bond3 present lower bond strength compared to other conditioning methods where aluminar sand blasting was used

No significant difference between the bond strength values of Cojet system , diamond-panavia system or diamond bur-amalgabond plus











3. Results

3.1. Bond strength








intervals (MPa)


Ra-value(mm)
















3. Results

3.1. Bond strength








intervals (MPa)


Ra-value(mm)
















3. Results

3.1. Bond strength








intervals (MPa)


Ra-value(mm)
















3. Results

3.1. Bond strength








intervals (MPa)


Ra-value(mm)







Failure analysis

• All specimen failed adhesively

• The roughness of the specimen prepared by alumina sandblast was less than the diamond bur , Cojet silicatization produced the lowest surface roughness


Failure analysis

higher bond strength values (5.13 ! 0.57 MPa) than all othersurface conditioning methods ( p = 0.013). The bond strengthvalues of specimens treated with All-bond 3 presentedsignificantly lower bond strength values compared to otherconditioning methods where alumina sandblasting was used( p = 0.02). No significant difference in bond strength valueswas noted between the alumina sandblasting together withthe use of All Bond 3 protocol and for conditioning methods

involving bur roughening of the amalgam surface.There was no significant difference between the bond

strength values of specimens prepared with the CoJet system(3.72 ! 0.51 MPa), diamond bur-Panavia system (3.42 ! 0.35 MPa)or diamond bur-Amalgambond Plus (3.40 ! 0.66 MPa).


SEM examination showed that all specimens examined failedadhesively, irrespective of the repair protocol used (Fig. 4). Asummary of the mean surface roughness values (Ra-values) is

shown in Table 2. The surface roughness of specimens, ashighlighted by the Ra-values determined by three-dimensionalprofilometry, identified that the roughness of specimensprepared by alumina sandblasting (mean Ra = 3.56 mm) wasmarkedly less than where a diamond bur (mean Ra = 15.35 mm)was used. The use of CoJet silicatization produced the lowestsurface roughness (Ra = 1.95 mm).

4. Discussion

Repairing an amalgam restored tooth exhibiting signs of singleor multiple cusp fractures can result in extended longevity ofthe existing restoration without unnecessarily sacrificinghealthy tooth structure as a result of progressive toothpreparation, and reducing the risk of pulpal damage.2 It isclearly preferable, therefore, to consider a repair procedure asan alternative to total restoration replacement or toothpreparation for a cast restoration, wherever possible.20 Since

Fig. 4 – SEM images of amalgam surfaces treated mechanically with (a) alumina sandblasting, (b) diamond bur and (c)silicatization with the CoJet system. All images showed surface prepared amalgam devoid of resin composite, indicatingadhesive failures.

j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 1 5 – 2 1 19


Discussion

• Repairing an amalgam restored tooth exhibiting signs of single or multiple cusps fracture can result in extend longevity of the existing restoration

• In the case of cusp fracture it is often aesthetically favourable to veneer the amalgam with tooth-coloured material


• Important factor in the quality of amalgam repair is the interfacial bond between the joined surfaces

• Previous studies suggested that shear bond strength testing has limitation

• The basic selection of the adhesive repair system used in the current study was their demonstrated ability to bond to metal

• In contrast to previous study , the finding of current study indicated that surface roughness of the amalgam substrate appears to have significant influence on its repair bond strength


• Alumina sandblasting and silicatization cause micro retention feature

• Diamond bur yields “macro” and “micro” retentive features

• Without use of adhesive , greater repair strength may be anticipated from the substrates yielding macro retentive feature


• With the use of adhesive , a better surface wetting was found occur with the micro-retentive amalgam surface

• due to better infiltration and improved physical interlocking

• Alumina sandblasting and silicatization remove large surface asperities and provide a more homogenous surface with major defects and stress concentration removed

• high degree of roughening(13.5-16.6um) induced by tx with diamond bur is likely to induce surface defect and area of concentration , deep asperities which adhesive may not fully infiltrate


• Previous studies have highlighted higher interfacial bond strengths between amalgam and resin composite where low surface roughness values were induced

• In this study a lower surface roughness induced by alumina sandblasting in combination with Panavia 21 adhesive system resulted in a significantly higher tensile bond strength compared with the Panavia 21 but prepared with a diamond bur

• This may suggest that improved surface homogenity implicit in the removal of large surface defects associated with alumina sandblasting improved adhesive bond to formed between 2 surfaces


Conclusion• 1. The tensile bond strengths of resin composite to

amalgam varied with the degree of amalgam surface roughness and the type of conditioning technique employed.

• 2. The combination of alumina sandblasting of the amalgam surface followed by the application of the Panavia 21 adhesive system exhibited significantly higher tensile bond strengths than other repair protocols tested

• 3. Interfacial failure between amalgam and resin composite was of adhesive nature, irrespective of the repair protocol employed.


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Amalgam repair