J. Dent. 1991; 19: 307-311
Microleakage inlays*
307
around direct composite
A. C. Shot-tall and R. L. Baylis Department
of Restorative
Dentistry,
The Dental School, Birmingham,
UK
ABSTRACT The purpose of this study was to compare the microleakage around direct composite inlays bonded with a dual cure luting composite into Class V type inlay cavities in extracted molar teeth. Bonding methods which included two cavity cleansing regimes and three bonding treatments were used. Either pumice and rinse or rinse only cavity cleansing was used to remove the separator agent (agar/alcohol) from the cavity surface prior to inlay bonding. Restorations were thermocycled between 5°C and 55°C (with intermediate baths at 36°C) before (240 cycles) and during (12 cycles) silver staining. Microleakage around the sectioned restorations was Data analysis indicated that failure to quantified using digital imaging microscopy at X 40 magnification. include pumice slurry application as part of the cavity cleansing regime prior to bonding lead to a marked increase in microleakage at the enamel/restoration interface following one of the three bonding treatments. KEY WORDS: J. Dent. 1991; 1991)
Dental composites, Inlays, Microleakage, Cavity cleansing 19: 307-311
(Received 23 October 1990;
reviewed 7 December 1990;
accepted 27 March
Correspondence should be addressed to: Dr A. C. Shortall, Department of Restorative Dentistry, The Dental School, St Chad’s Queensway, Birmingham 84 6NN. UK.
INTRODUCTION Advances in dental composite technology combined with the ability to produce an aesthetic restoration that is bonded to tooth structure have lead to increased clinical usage of composites in recent years. Despite improvements in the wear resistance of some of the new materials, problems remain with the use of direct composites especially in the Class II situation. Poor marginal adaptation and microleakage have been identified as problems at the cervical margins of Class II composites (Ehrnford and Derand, 1984; Lui et al., 1987; Fayyad and Shortall, 1987). Polymerization contraction of the composite and poor adhesion of the material to cervical tooth structure have been implicated in this regard. Whilst the development of visible light-cured composites has been of major benefit, the inaccessibility of deep confined proximal areas to the light-curing source in the Class II situation creates the potential for poor marginal adaptation because of inadequate cure of the composite in the region. Manufacturers have responded to these problems by introducing composite inlay systems which utilize direct *The findings of the BSDR,
of this study were presented at the Annual King’s College. London, April 1990.
@ 1991 Butterworth-Heinemann 0300-5712/91/050307-05
Ltd.
Conference
and/or indirect techniques. With these systems a high degree of cure of the composite inlay may be assured before the restoration is bonded to the tooth, and also the adverse effects of polymerization contraction can be minimized. Dual cure luting agents have reduced the problems associated with inadequate polymerization of composite resin in areas distant from the light source. Because retention of resin-bonded inlays is not as dependent upon cavity preparation geometry as traditionally retained restorations, resin-bonded inlays may allow a more conservative approach to cavity preparation. In addition to improvements in composite systems and restorative techniques there has been steady progress in treatments for bonding resins to tooth tissues. Some of the more recently developed dentine bonding agents make use of conditioning liquids which render the dentine amenable to bonding at the same time as etching the enamel, thus greatly simplifying the resin bonding of restorations. These conditioners include the oxalate solution of the so-called ‘Bowen’ bonding system and the experimental pyruvic acid/glycine solution devised for use with the Gluma system (Asmussen and Bowen, 1987). A two-step material (Mirage-Bond, Chameleon Dental Products, Inc., Kansas City, KA, USA) which allows the dentine and enamel to be treated simultaneously and
J. Dent. 1991; 19: No. 5
308
Table 1. Bonding
Bonding A B C
treatments
treatments
employed
Mirage-Bond (Myrons) Gluma* (Bayer) Brilliant Etch Gel (Coltene)
‘Pyruvic acid/glycine dentine conditioning.
Cavity surfaces treated Enamel Enamel Enamel
and dentine and dentine
experimental cleanser used for enamel and
which is commercially available is the ‘Mirage-Bond Dentin and Enamel Adhesive’. This consists of two solutions in sealed carpules which are dispensed using a syringe. The first solution consists of an acidified surface active compound (2.5 percent nitric acid,N-phenylglycine) which is formulated to simultaneously etch the prepared enamel, remove the dentine smear layer and condition the exposed dentine. The second solution consists of a hydrophilic resin (the reaction product of pyromellitic acid dianhydride methacrylate-PMDM) in a volatile solvent (acetone). The resin polymerizes in contact with the previously conditioned surface. The solutions may be applied via a cotton wool pledget or directly from the syringe needle (Pass, 1989), the important points being that the first solution must be continually agitated during application and it must not be rinsed off but air dried after application. The purpose of this investigation was to assess the occlusal (enamel) and cervical (dentine) marginal seal of direct composite inlays (Direct Inlay System, Coltene Brilliant D.I., Direct-Inlay-System, Coltene AG, Altstatten, Switzerland) bonded with a dual cure luting composite (Duo Cure, Coltene) into Class V type cavities in extracted molar teeth using various bonding treatments. These included two cavity cleansing regimes and three bonding treatments. MATERIALS
Light-cured composite (Brilliant D.I., Coltene) was used to fill the cavities and the composite was cured for 60 s with a light unit (Luxor, ICI Dental, Macclesfield, UK). The inlays were removed, marginal excess eliminated and additional separator applied to the composite inlays before curing in the oven (Coltene D.I.-500) as per manufacturer’s instructions. Separator was then washed off before air drying the inlays.
jet.
tested
AND METHODS
Cavity preparation Standardized Class V type inlay cavities were prepared (using 80 urn particle size preparation diamonds and 25 urn particle size finishing diamonds) in mesial and distal surfaces of 30 extracted molar teeth. The occlusal cavity margin, placed in enamel, was 5 mm long and the gingival margin, placed in cementum, was 4 mm long. The cervical floor was 1 mm deep. The cavities were randomly allocated amongst three experimental groups A, B and C (Table I) according to the bonding treatment employed. Two inlay cavities were prepared per tooth and the inlays in each experimental group were divided equally between mesial and distal surfaces. Inlay fabrication Separator agent (Brilliant D. I., Coltene) was applied to the cavities and then dispersed to a thin layer with an air
Cavity cleansing One of two cavity cleansing regimes was used to assist in the removal of Separator agent (Brilliant D.I., Coltene) from the cavity surfaces prior to bonding. Regime 1 employed a pumice cleansing of the inlay cavity surface (for 10 s) using a pumice/water slurry applied on a bristle brush (which had been trimmed to lit the cavity dimensions) followed by air/water spray rinsing (5 s) and air jet drying (5 s). Regime 2 consisted of rinsing the cavity with an air/water spray (5 s) and air jet drying (5 s). Pumice slurry cavity cleansing (Regime 1) is recommended by the manufacturer of the Mirage-Bond material. Water rinse cavity cleansing (Regime 2) is the standard regime recommended for use with the direct composite inlay system used (Brilliant D.I., Coltene). Bonding protocol (15 teeth)
for Regime
1 cavities
Treatment A (Mirage-Bond) Enamel and dentine were treated for 30 s with activating conditioner solution applied on a cotton pledget using a scrubbing technique. Excess solution was then dispersed with an air jet and drying was continued for 30 s. The hydrophilic resin solution was then applied and allowed to evaporate for 40 s. Treatment B (Gluma) Enamel and dentine were conditioned for 30 s with an experimental pyruvic acid/glycine solution (10 per cent w/w pyruvic acid with glycine, pH 2.20). These cavities were rinsed with an air/water spray (10 s) and dried (5 s). Next Gluma primer (Gluma Primer 3, Bayer Dental, Leverkusen, Germany) was applied (30 s) and the cavity dried (5 s). Treatment C (control) The enamel cavity walls and margins were etched with phosphoric acid etch gel (Coltene D.I.) for 30 s. These cavities were then rinsed with an air/water spray (20 s) and air dried (5 s). For all three groups the inlays were luted with dual cure composite (Duo-Cure, Coltene), and this was light cured for 60 s. Marginal excess of luting composite was then removed using composite finishing diamonds (Intensiv
Shortall
and Baylis: Microleakage
Composhape Diamonds, W. Hubschmid & Sohn, Lugano, Switzerland). The restored teeth were then kept in individual pots of distilled water at 23 “C and during the next 10 days they were exposed to 240 cycles of thermal stress. Each cycle consisted of immersion in water-baths at 5°C (1 min), 36°C (4min), 55°C (1 min) and 36°C (4 min). The apices ofthe teeth were then sealed with lightcured composite and the root surfaces were varnished to within 1 mm of the restoration margin before a further period of 2 h thermal cycling (12 cycles), this time in 50 per cent aqueous silver nitrate solution in darkness. The teeth were then rinsed, immersed in photodeveloper solution and exposed to light for 3 h prior to sectioning mesiodistally through the centre of the restorations using a water-cooled diamond-bladed sectioning machine. Bonding protocol (15 teeth)
for Regime
around direct composite
resin inlays
combinations at the restoration/dentine interface was limited. In contrast, the results for the enamel/restoration interface demonstrate a high mean microleakage value for Treatment A when Regime 2 cavity cleansing (rinse only) was used. The analysis ofvariance for the data at this interface showed that a significant difference (2 P < 0.05) existed between the test groups considered together but no significant difference (2 P > 0.05) was found between groups at the dentine/restoration interface (Table ZZO. Paired group comparisons (Scheffe test) of the difference between means for the enamel/restoration interface (Table ZV) showed that the difference between the mean for the Regime 2/Treatment A test group and all other means exceeded the critical difference value (0.221), thus indicating a significant difference (2 P < 0.05) between this and all other groups. No other significant differences for any of the remaining paired group comparisons were found.
2 cavities
The experiment was then repeated using another set of 15 teeth, this time using Regime 2 for cavity cleansing prior to bonding and the protocol for Treatment A cavities (Mirage-Bond) was modified in that the activating conditioner solution was applied from the syringe needle and agitated with this instead of on a cotton pledget using a scrubbing technique. The sectioned restorations were examined with a stereomicroscope (magnification X 40) and the extent of silver stain at the composite/dentine and composite/ enamel interfaces on each half of each sectioned restoration was measured and quantified using an imageanalysis apparatus linked to the microscope by a viewing tube (Shortall et al., 1989). An average of the two values was taken to obtain a mean in each case. A one-way analysis of variance was performed on the data and statistical comparisons between group means were determined using the Scheffe test (at 2 P < 0.05 significance level).
ADDITIONAL
INVESTIGATION
An extra set of specimens (10 teeth, two cavities per tooth) was prepared to establish whether variation in application technique (via a syringe needle or applied on a cotton pledget with a scrubbing technique) of the activating conditioner solution used for the Treatment A cavities (Mirage-Bond) was involved in the significant difference found in microleakage extent at the enamel/restoration Table II. Extent of silver stain (mm) at the enamel/restoration interface and the dentine/restoration interface
Bonding treatment A
Cavity cleansing regime* Enamel interface Dentine interface 1 2 7 2 0.073 (0.074) 0.034 (0.036) 0.028 (0.017)
8 C
RESULTS
0.443 (0.338) 0.1 18 (0.083) 0.052 (0.038)
Table 111.Results of simple randomized design analysis of variance for enamel and dentine
Between groups Within groups Dentine Total Between groups Within groups
0.182 (p;;)
0.190 (p$)
p;)
((pi)
(0:093)
(0:040)
Results shown are mean of 10 values: figures in parenthesesare s.d. *Regime 1, pumice and rinsecavity cleansing; Regime 2, rinseonly cavity cleansing.
The results for extent of silver stain penetration (mm) from the tooth surface are listed in Table ZZ.The extent of microleakage for all cleansing regime/bonding treatment
Enamel Total
309
Source m.s.
F -
-
5 54
0.25 0.02
1 1.76 -
< 0.001 -
59 5 54
0.01 3.85E-3
2.25 -
> 0.05 -
ss
d.f.
2.43
59
1.27 1.16 0.25 0.04 0.2 1
P
310
J. Dent.
1991;
19: No. 5
Table IV. Scheffe test comparisons between interface (1) Group/treatment A2
A2
62
c2
Al
61
Cl
P< 0.05
P< 0.05
P< 0.05
P < 0.05
P < 0.05
P> 0.05
P> P > 0.05
P> P > 0.05
P> P > 0.05
P > 0.05
P > 0.05 P > 0.05
:;
Al 61 Cl
Table V. Extent of silver stain (mm) atthe enamel/restoration interface and the dentine/restoration interface for additional Mirage-Bond specimens (all Regime 1 cavity cleansing) Application technique for part 1 solution Syringe needle
Enamel interface 0.058
means for the enamel/restoration
Dentine interface 0.167
(y&)
(y;;)
(0:035)
(0:069)
Cotton pledget Results shown are mean of 10 values; figures in parentheses s.d.
are
interface. A pumice and water rinse cavity cleansing regime was employed for all of these additional test cavities. The data (summarized in Table V) was analysed by a paired Student’s t test which showed that there was no significant difference (2P > 0.05) between the mean values recorded for the two sets of specimens at the enamel/restoration interface, thus demonstrating that the increased microleakage pattern in the main investigation was due to omission of the pumice slurry application as part of the cavity cleansing regime.
DISCUSSION The extent of microleakage at the dentine/restoration interface was low for all test groups even though all the restorations were thermally stressed before and during silver staining and no dentine bonding agent was employed for the Treatment C specimens. The thermal stressing procedure adopted was not meant to simulate the range and duration of temperature change likely to be encountered clinically (Longman and Pearson, 1987) but was simply adopted to produce a stress on the resin/tooth bond (Bullard et al., 1988). The low extent of microleakage seen at the dentine/ restoration interface in this study contrasts with the results of the investigation by Hasegawa et al. (1989) who found leakage at the dentine margin of MOD indirect composite inlays to be about 1 mm on average when using a silvernitrate staining technique and thermocycling regime similar to those of the current study. Shortall et al. (1989) also reported more extensive leakage at the cervical dentine margin of uncycled Class II inlays using a similar method of assessment. Their results showed that the efficacy of marginal seal of the inlays varied according to
the treatments and materials tested. This contrasts with the findings of the current investigation where no such discrimination could be made. It is likely that the simple cavity form, small dimensions and good initial fit of the unbonded restorations in the current study contributed to this difference in the results. Douglas et al. (1989) also reported very low microleakage values for cavities restored with Class V composite inlays. However, they found that varying the adhesive in the bonding treatment did result in a significant difference in the extent of microleakage. Also the adhesives tested, the method of inlay fabrication and the reference points used for assessing the extent of silver stain penetration all differed from the current investigation, thus preventing any direct comparison between the two studies. Microleakage assessment techniques which depend upon the inspection of a crosssection of a silver-stained specimen for evidence of imperfect marginal seal may have a limited discriminatory potential when the total amount of leakage is slight and there is bulk uptake of silver stain by the root surface (Douglas et al., 1989).Alternative techniques which assess marginal adaptation according to the presence of dye stain (Zidan el al., 1987) or by marginal gap registration around the entire restoration/cavosurface margin (Peutzfeldt and Asmussen, 1989) may have greater potential in this respect. Peutzfeldt and Asmussen (1989) compared the direct measurement of marginal gap formation around the entire restoration circumference (wall-to-wall contraction measurement) with the silver stain penetration method of assessment and concluded that whilst both methods were applicable the former had greater discriminatory power. This conclusion may be relevant to the current results for the dentine/restoration interface where the extent of silver penetration is low for all test groups. A technique which combines marginal adaptation assessment of the entire restoration cavosurface margin/tooth interface with a cross-section assessment may be advantageous in future investigations. A significant finding from the current study is that the cavity cleansing procedure employed prior to enamel conditioning with the activating conditioner solution (Mirage-Bond) used for Treatment A cavities had a major influence on the extent of microleakage at this interface. The etching agent in the activating conditioner solution is 2.5 per cent nitric acid and it is likely that this agent was less effective in producing a satisfactory enamel etch than
Shot-tall and Baylis: Microleakage
the 10 per cent pyruvic acid and 35 per cent phosphoric acid etching agents (Treatments B and C) when water rinsing only was employed for cavity cleansing. It is probable that this procedure was less effective than the pumice/water rinse cavity cleansing regime at removing Separator agent from the enamel cavity surface. It would appear that the manufacturer’s recommendation to pumice the cavity surface prior to bonding is an essential step in the bonding protocol with the MirageBond system. The preparation cleansing procedure has also been shown to be a significant factor in regard to crown retention (Button et al., 1988). It is presumed that microleakage at the dentine/restoration interface was not affected by omission of the pumice cleansing treatment prior to bonding because the inherently wetter nature of the dentine cavity surface reduced the extent of contamination and/or facilitated removal of the separator agent. Additional investigations are planned to test this hypothesis.
Acknowledgements The image analysis equipment used in this investigation was provided through a grant (GL 3009) by the Endowment Fund Medical Research Committee of the Central Birmingham Health Authority. The authors acknowledge the word processing skills of Mrs G. Bunney in the preparation of this manuscript.
References Asmussen E. and Bowen R. L. (1987) Effect of acidic pretreatment on adhesion to dentin mediated by Gluma. J. Dent. Res. 66, 1386-1388.
around direct composite
resin inlays
311
Bullard R. H., Leinfelder K. F. and Russell C. M. (1988) Effect of coefticient of thermal expansion on microleakage. J Am. Dent. Assoc. 116, 871-874. Button G. L., Moon P. C.. Barnes R. F. et al. (1988) Effect of preparation
cleaning
procedures
on crown retention.
J.
Prosthef. Dent. 59, 14.5-148. Douglas W. H., Fields R. P. and Fundingsland J. (1989) A comparison between the microleakage of direct and indirect composite restorative systems. J. Dent, 17, 184-188. Ehrnford L. and Derand T. (1984) Cervical gap formation in Class II composite resin restorations. Swed. Dent. J. 8, 15-19. Fayyad M. A. and Shortall A. C. C. (1987) Microleakage of dentine bonded posterior composite restorations. J. Dent. 15,67-72. Hasegawa E. A, Boyer D. B. and Chan D. C. (1989) Microleakage of indirect composite inlays. Dent. Mater. 5, 388-391. Longman C. M. and Pearson G. J. (1987) Variations in tooth temperature in the oral cavity during fluid intake. Biomaterials 8, 411-414. Lui J. L., Masutani S., Setcos J. C. et al. (1987) Margin quality and microleakage of class II composite resin restorations. J. Am. Dent. Assoc. 114,49-54. Pass K. (1989) Two-step dentine-enamel bonding. Dent. Practit. 27, (23), l-3. Peutzfeldt A. and Asmussen E. (1989) Bonding and gap-formation of glass-ionomer cement used in conjunction with composite resin. Acta Odontol. Stand. 47, 141-148. Shortall A. C., Baylis R. L., Baylis M. A. et al. (1989) Marginal seal comparisons between resin-bonded class II porcelain inlays, posterior composite restorations and direct composite resin inlays. Int. J. Prosthodont. 2, 217-223. Zidan O., Gomez-Marin 0. and Tsuchiya T. (1987) A comparative study of the effects of dentinal bonding agents and application techniques on marginal gaps in Class V cavities. J. Dent. Res. 66, 716-721.
Microleakage inlays*
307
around direct composite
A. C. Shot-tall and R. L. Baylis Department
of Restorative
Dentistry,
The Dental School, Birmingham,
UK
ABSTRACT The purpose of this study was to compare the microleakage around direct composite inlays bonded with a dual cure luting composite into Class V type inlay cavities in extracted molar teeth. Bonding methods which included two cavity cleansing regimes and three bonding treatments were used. Either pumice and rinse or rinse only cavity cleansing was used to remove the separator agent (agar/alcohol) from the cavity surface prior to inlay bonding. Restorations were thermocycled between 5°C and 55°C (with intermediate baths at 36°C) before (240 cycles) and during (12 cycles) silver staining. Microleakage around the sectioned restorations was Data analysis indicated that failure to quantified using digital imaging microscopy at X 40 magnification. include pumice slurry application as part of the cavity cleansing regime prior to bonding lead to a marked increase in microleakage at the enamel/restoration interface following one of the three bonding treatments. KEY WORDS: J. Dent. 1991; 1991)
Dental composites, Inlays, Microleakage, Cavity cleansing 19: 307-311
(Received 23 October 1990;
reviewed 7 December 1990;
accepted 27 March
Correspondence should be addressed to: Dr A. C. Shortall, Department of Restorative Dentistry, The Dental School, St Chad’s Queensway, Birmingham 84 6NN. UK.
INTRODUCTION Advances in dental composite technology combined with the ability to produce an aesthetic restoration that is bonded to tooth structure have lead to increased clinical usage of composites in recent years. Despite improvements in the wear resistance of some of the new materials, problems remain with the use of direct composites especially in the Class II situation. Poor marginal adaptation and microleakage have been identified as problems at the cervical margins of Class II composites (Ehrnford and Derand, 1984; Lui et al., 1987; Fayyad and Shortall, 1987). Polymerization contraction of the composite and poor adhesion of the material to cervical tooth structure have been implicated in this regard. Whilst the development of visible light-cured composites has been of major benefit, the inaccessibility of deep confined proximal areas to the light-curing source in the Class II situation creates the potential for poor marginal adaptation because of inadequate cure of the composite in the region. Manufacturers have responded to these problems by introducing composite inlay systems which utilize direct *The findings of the BSDR,
of this study were presented at the Annual King’s College. London, April 1990.
@ 1991 Butterworth-Heinemann 0300-5712/91/050307-05
Ltd.
Conference
and/or indirect techniques. With these systems a high degree of cure of the composite inlay may be assured before the restoration is bonded to the tooth, and also the adverse effects of polymerization contraction can be minimized. Dual cure luting agents have reduced the problems associated with inadequate polymerization of composite resin in areas distant from the light source. Because retention of resin-bonded inlays is not as dependent upon cavity preparation geometry as traditionally retained restorations, resin-bonded inlays may allow a more conservative approach to cavity preparation. In addition to improvements in composite systems and restorative techniques there has been steady progress in treatments for bonding resins to tooth tissues. Some of the more recently developed dentine bonding agents make use of conditioning liquids which render the dentine amenable to bonding at the same time as etching the enamel, thus greatly simplifying the resin bonding of restorations. These conditioners include the oxalate solution of the so-called ‘Bowen’ bonding system and the experimental pyruvic acid/glycine solution devised for use with the Gluma system (Asmussen and Bowen, 1987). A two-step material (Mirage-Bond, Chameleon Dental Products, Inc., Kansas City, KA, USA) which allows the dentine and enamel to be treated simultaneously and
J. Dent. 1991; 19: No. 5
308
Table 1. Bonding
Bonding A B C
treatments
treatments
employed
Mirage-Bond (Myrons) Gluma* (Bayer) Brilliant Etch Gel (Coltene)
‘Pyruvic acid/glycine dentine conditioning.
Cavity surfaces treated Enamel Enamel Enamel
and dentine and dentine
experimental cleanser used for enamel and
which is commercially available is the ‘Mirage-Bond Dentin and Enamel Adhesive’. This consists of two solutions in sealed carpules which are dispensed using a syringe. The first solution consists of an acidified surface active compound (2.5 percent nitric acid,N-phenylglycine) which is formulated to simultaneously etch the prepared enamel, remove the dentine smear layer and condition the exposed dentine. The second solution consists of a hydrophilic resin (the reaction product of pyromellitic acid dianhydride methacrylate-PMDM) in a volatile solvent (acetone). The resin polymerizes in contact with the previously conditioned surface. The solutions may be applied via a cotton wool pledget or directly from the syringe needle (Pass, 1989), the important points being that the first solution must be continually agitated during application and it must not be rinsed off but air dried after application. The purpose of this investigation was to assess the occlusal (enamel) and cervical (dentine) marginal seal of direct composite inlays (Direct Inlay System, Coltene Brilliant D.I., Direct-Inlay-System, Coltene AG, Altstatten, Switzerland) bonded with a dual cure luting composite (Duo Cure, Coltene) into Class V type cavities in extracted molar teeth using various bonding treatments. These included two cavity cleansing regimes and three bonding treatments. MATERIALS
Light-cured composite (Brilliant D.I., Coltene) was used to fill the cavities and the composite was cured for 60 s with a light unit (Luxor, ICI Dental, Macclesfield, UK). The inlays were removed, marginal excess eliminated and additional separator applied to the composite inlays before curing in the oven (Coltene D.I.-500) as per manufacturer’s instructions. Separator was then washed off before air drying the inlays.
jet.
tested
AND METHODS
Cavity preparation Standardized Class V type inlay cavities were prepared (using 80 urn particle size preparation diamonds and 25 urn particle size finishing diamonds) in mesial and distal surfaces of 30 extracted molar teeth. The occlusal cavity margin, placed in enamel, was 5 mm long and the gingival margin, placed in cementum, was 4 mm long. The cervical floor was 1 mm deep. The cavities were randomly allocated amongst three experimental groups A, B and C (Table I) according to the bonding treatment employed. Two inlay cavities were prepared per tooth and the inlays in each experimental group were divided equally between mesial and distal surfaces. Inlay fabrication Separator agent (Brilliant D. I., Coltene) was applied to the cavities and then dispersed to a thin layer with an air
Cavity cleansing One of two cavity cleansing regimes was used to assist in the removal of Separator agent (Brilliant D.I., Coltene) from the cavity surfaces prior to bonding. Regime 1 employed a pumice cleansing of the inlay cavity surface (for 10 s) using a pumice/water slurry applied on a bristle brush (which had been trimmed to lit the cavity dimensions) followed by air/water spray rinsing (5 s) and air jet drying (5 s). Regime 2 consisted of rinsing the cavity with an air/water spray (5 s) and air jet drying (5 s). Pumice slurry cavity cleansing (Regime 1) is recommended by the manufacturer of the Mirage-Bond material. Water rinse cavity cleansing (Regime 2) is the standard regime recommended for use with the direct composite inlay system used (Brilliant D.I., Coltene). Bonding protocol (15 teeth)
for Regime
1 cavities
Treatment A (Mirage-Bond) Enamel and dentine were treated for 30 s with activating conditioner solution applied on a cotton pledget using a scrubbing technique. Excess solution was then dispersed with an air jet and drying was continued for 30 s. The hydrophilic resin solution was then applied and allowed to evaporate for 40 s. Treatment B (Gluma) Enamel and dentine were conditioned for 30 s with an experimental pyruvic acid/glycine solution (10 per cent w/w pyruvic acid with glycine, pH 2.20). These cavities were rinsed with an air/water spray (10 s) and dried (5 s). Next Gluma primer (Gluma Primer 3, Bayer Dental, Leverkusen, Germany) was applied (30 s) and the cavity dried (5 s). Treatment C (control) The enamel cavity walls and margins were etched with phosphoric acid etch gel (Coltene D.I.) for 30 s. These cavities were then rinsed with an air/water spray (20 s) and air dried (5 s). For all three groups the inlays were luted with dual cure composite (Duo-Cure, Coltene), and this was light cured for 60 s. Marginal excess of luting composite was then removed using composite finishing diamonds (Intensiv
Shortall
and Baylis: Microleakage
Composhape Diamonds, W. Hubschmid & Sohn, Lugano, Switzerland). The restored teeth were then kept in individual pots of distilled water at 23 “C and during the next 10 days they were exposed to 240 cycles of thermal stress. Each cycle consisted of immersion in water-baths at 5°C (1 min), 36°C (4min), 55°C (1 min) and 36°C (4 min). The apices ofthe teeth were then sealed with lightcured composite and the root surfaces were varnished to within 1 mm of the restoration margin before a further period of 2 h thermal cycling (12 cycles), this time in 50 per cent aqueous silver nitrate solution in darkness. The teeth were then rinsed, immersed in photodeveloper solution and exposed to light for 3 h prior to sectioning mesiodistally through the centre of the restorations using a water-cooled diamond-bladed sectioning machine. Bonding protocol (15 teeth)
for Regime
around direct composite
resin inlays
combinations at the restoration/dentine interface was limited. In contrast, the results for the enamel/restoration interface demonstrate a high mean microleakage value for Treatment A when Regime 2 cavity cleansing (rinse only) was used. The analysis ofvariance for the data at this interface showed that a significant difference (2 P < 0.05) existed between the test groups considered together but no significant difference (2 P > 0.05) was found between groups at the dentine/restoration interface (Table ZZO. Paired group comparisons (Scheffe test) of the difference between means for the enamel/restoration interface (Table ZV) showed that the difference between the mean for the Regime 2/Treatment A test group and all other means exceeded the critical difference value (0.221), thus indicating a significant difference (2 P < 0.05) between this and all other groups. No other significant differences for any of the remaining paired group comparisons were found.
2 cavities
The experiment was then repeated using another set of 15 teeth, this time using Regime 2 for cavity cleansing prior to bonding and the protocol for Treatment A cavities (Mirage-Bond) was modified in that the activating conditioner solution was applied from the syringe needle and agitated with this instead of on a cotton pledget using a scrubbing technique. The sectioned restorations were examined with a stereomicroscope (magnification X 40) and the extent of silver stain at the composite/dentine and composite/ enamel interfaces on each half of each sectioned restoration was measured and quantified using an imageanalysis apparatus linked to the microscope by a viewing tube (Shortall et al., 1989). An average of the two values was taken to obtain a mean in each case. A one-way analysis of variance was performed on the data and statistical comparisons between group means were determined using the Scheffe test (at 2 P < 0.05 significance level).
ADDITIONAL
INVESTIGATION
An extra set of specimens (10 teeth, two cavities per tooth) was prepared to establish whether variation in application technique (via a syringe needle or applied on a cotton pledget with a scrubbing technique) of the activating conditioner solution used for the Treatment A cavities (Mirage-Bond) was involved in the significant difference found in microleakage extent at the enamel/restoration Table II. Extent of silver stain (mm) at the enamel/restoration interface and the dentine/restoration interface
Bonding treatment A
Cavity cleansing regime* Enamel interface Dentine interface 1 2 7 2 0.073 (0.074) 0.034 (0.036) 0.028 (0.017)
8 C
RESULTS
0.443 (0.338) 0.1 18 (0.083) 0.052 (0.038)
Table 111.Results of simple randomized design analysis of variance for enamel and dentine
Between groups Within groups Dentine Total Between groups Within groups
0.182 (p;;)
0.190 (p$)
p;)
((pi)
(0:093)
(0:040)
Results shown are mean of 10 values: figures in parenthesesare s.d. *Regime 1, pumice and rinsecavity cleansing; Regime 2, rinseonly cavity cleansing.
The results for extent of silver stain penetration (mm) from the tooth surface are listed in Table ZZ.The extent of microleakage for all cleansing regime/bonding treatment
Enamel Total
309
Source m.s.
F -
-
5 54
0.25 0.02
1 1.76 -
< 0.001 -
59 5 54
0.01 3.85E-3
2.25 -
> 0.05 -
ss
d.f.
2.43
59
1.27 1.16 0.25 0.04 0.2 1
P
310
J. Dent.
1991;
19: No. 5
Table IV. Scheffe test comparisons between interface (1) Group/treatment A2
A2
62
c2
Al
61
Cl
P< 0.05
P< 0.05
P< 0.05
P < 0.05
P < 0.05
P> 0.05
P> P > 0.05
P> P > 0.05
P> P > 0.05
P > 0.05
P > 0.05 P > 0.05
:;
Al 61 Cl
Table V. Extent of silver stain (mm) atthe enamel/restoration interface and the dentine/restoration interface for additional Mirage-Bond specimens (all Regime 1 cavity cleansing) Application technique for part 1 solution Syringe needle
Enamel interface 0.058
means for the enamel/restoration
Dentine interface 0.167
(y&)
(y;;)
(0:035)
(0:069)
Cotton pledget Results shown are mean of 10 values; figures in parentheses s.d.
are
interface. A pumice and water rinse cavity cleansing regime was employed for all of these additional test cavities. The data (summarized in Table V) was analysed by a paired Student’s t test which showed that there was no significant difference (2P > 0.05) between the mean values recorded for the two sets of specimens at the enamel/restoration interface, thus demonstrating that the increased microleakage pattern in the main investigation was due to omission of the pumice slurry application as part of the cavity cleansing regime.
DISCUSSION The extent of microleakage at the dentine/restoration interface was low for all test groups even though all the restorations were thermally stressed before and during silver staining and no dentine bonding agent was employed for the Treatment C specimens. The thermal stressing procedure adopted was not meant to simulate the range and duration of temperature change likely to be encountered clinically (Longman and Pearson, 1987) but was simply adopted to produce a stress on the resin/tooth bond (Bullard et al., 1988). The low extent of microleakage seen at the dentine/ restoration interface in this study contrasts with the results of the investigation by Hasegawa et al. (1989) who found leakage at the dentine margin of MOD indirect composite inlays to be about 1 mm on average when using a silvernitrate staining technique and thermocycling regime similar to those of the current study. Shortall et al. (1989) also reported more extensive leakage at the cervical dentine margin of uncycled Class II inlays using a similar method of assessment. Their results showed that the efficacy of marginal seal of the inlays varied according to
the treatments and materials tested. This contrasts with the findings of the current investigation where no such discrimination could be made. It is likely that the simple cavity form, small dimensions and good initial fit of the unbonded restorations in the current study contributed to this difference in the results. Douglas et al. (1989) also reported very low microleakage values for cavities restored with Class V composite inlays. However, they found that varying the adhesive in the bonding treatment did result in a significant difference in the extent of microleakage. Also the adhesives tested, the method of inlay fabrication and the reference points used for assessing the extent of silver stain penetration all differed from the current investigation, thus preventing any direct comparison between the two studies. Microleakage assessment techniques which depend upon the inspection of a crosssection of a silver-stained specimen for evidence of imperfect marginal seal may have a limited discriminatory potential when the total amount of leakage is slight and there is bulk uptake of silver stain by the root surface (Douglas et al., 1989).Alternative techniques which assess marginal adaptation according to the presence of dye stain (Zidan el al., 1987) or by marginal gap registration around the entire restoration/cavosurface margin (Peutzfeldt and Asmussen, 1989) may have greater potential in this respect. Peutzfeldt and Asmussen (1989) compared the direct measurement of marginal gap formation around the entire restoration circumference (wall-to-wall contraction measurement) with the silver stain penetration method of assessment and concluded that whilst both methods were applicable the former had greater discriminatory power. This conclusion may be relevant to the current results for the dentine/restoration interface where the extent of silver penetration is low for all test groups. A technique which combines marginal adaptation assessment of the entire restoration cavosurface margin/tooth interface with a cross-section assessment may be advantageous in future investigations. A significant finding from the current study is that the cavity cleansing procedure employed prior to enamel conditioning with the activating conditioner solution (Mirage-Bond) used for Treatment A cavities had a major influence on the extent of microleakage at this interface. The etching agent in the activating conditioner solution is 2.5 per cent nitric acid and it is likely that this agent was less effective in producing a satisfactory enamel etch than
Shot-tall and Baylis: Microleakage
the 10 per cent pyruvic acid and 35 per cent phosphoric acid etching agents (Treatments B and C) when water rinsing only was employed for cavity cleansing. It is probable that this procedure was less effective than the pumice/water rinse cavity cleansing regime at removing Separator agent from the enamel cavity surface. It would appear that the manufacturer’s recommendation to pumice the cavity surface prior to bonding is an essential step in the bonding protocol with the MirageBond system. The preparation cleansing procedure has also been shown to be a significant factor in regard to crown retention (Button et al., 1988). It is presumed that microleakage at the dentine/restoration interface was not affected by omission of the pumice cleansing treatment prior to bonding because the inherently wetter nature of the dentine cavity surface reduced the extent of contamination and/or facilitated removal of the separator agent. Additional investigations are planned to test this hypothesis.
Acknowledgements The image analysis equipment used in this investigation was provided through a grant (GL 3009) by the Endowment Fund Medical Research Committee of the Central Birmingham Health Authority. The authors acknowledge the word processing skills of Mrs G. Bunney in the preparation of this manuscript.
References Asmussen E. and Bowen R. L. (1987) Effect of acidic pretreatment on adhesion to dentin mediated by Gluma. J. Dent. Res. 66, 1386-1388.
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Bullard R. H., Leinfelder K. F. and Russell C. M. (1988) Effect of coefticient of thermal expansion on microleakage. J Am. Dent. Assoc. 116, 871-874. Button G. L., Moon P. C.. Barnes R. F. et al. (1988) Effect of preparation
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Prosthef. Dent. 59, 14.5-148. Douglas W. H., Fields R. P. and Fundingsland J. (1989) A comparison between the microleakage of direct and indirect composite restorative systems. J. Dent, 17, 184-188. Ehrnford L. and Derand T. (1984) Cervical gap formation in Class II composite resin restorations. Swed. Dent. J. 8, 15-19. Fayyad M. A. and Shortall A. C. C. (1987) Microleakage of dentine bonded posterior composite restorations. J. Dent. 15,67-72. Hasegawa E. A, Boyer D. B. and Chan D. C. (1989) Microleakage of indirect composite inlays. Dent. Mater. 5, 388-391. Longman C. M. and Pearson G. J. (1987) Variations in tooth temperature in the oral cavity during fluid intake. Biomaterials 8, 411-414. Lui J. L., Masutani S., Setcos J. C. et al. (1987) Margin quality and microleakage of class II composite resin restorations. J. Am. Dent. Assoc. 114,49-54. Pass K. (1989) Two-step dentine-enamel bonding. Dent. Practit. 27, (23), l-3. Peutzfeldt A. and Asmussen E. (1989) Bonding and gap-formation of glass-ionomer cement used in conjunction with composite resin. Acta Odontol. Stand. 47, 141-148. Shortall A. C., Baylis R. L., Baylis M. A. et al. (1989) Marginal seal comparisons between resin-bonded class II porcelain inlays, posterior composite restorations and direct composite resin inlays. Int. J. Prosthodont. 2, 217-223. Zidan O., Gomez-Marin 0. and Tsuchiya T. (1987) A comparative study of the effects of dentinal bonding agents and application techniques on marginal gaps in Class V cavities. J. Dent. Res. 66, 716-721.
