The Journal of Adhesive Dentistry, 01/2011

The advent of "Adhesive Dentistry" has simplified the guidelines for cavity preparation enormously. The design and extent of the current preparations are basically defined by the extent and shape of the caries lesion, potentially slightly extended by bevelling the cavity margins in order to meet the modern concept of minimally invasive dentistry. New caries excavation techniques have been introduced, such as the use of plastic and ceramic burs, improved caries-disclosing dyes, enzymatic caries-dissolving agents, caries-selective sono/air abrasion and laser ablation. They all aim to remove or help remove caries-infected tissue as selectively as possible, while being minimally invasive through maximum preservation of caries-affected tissue. Each technique entails a specific caries-removal endpoint and produces residual dentin substrates of different natures and thus different receptiveness for adhesive procedures. This paper reviews the newest developments in caries excavation techniques and their effect on the remaining dentin tissue with regard to its bonding receptiveness. Keywords: minimally invasive dentistry, dentin caries, caries excavation, bond strength of composite/dentin interfaces

Purpose: To evaluate marginal adaptation of Class I restorations in enamel using contemporary one-bottle all-in-one adhesives, stressed by thermocycling (TC) and mechanical loading (ML). Materials and Methods: Ninety-six extracted human molars were prepared (standard Class I cavities: 3 mm deep, 6 mm wide mesio-distally, and 4 mm wide bucco-lingually). Twelve adhesive systems were used: OptiBond FL (OPT), Clearfil SE Bond (CSE) and Adper Prompt L-Pop (PLP) as controls, compared with nine one-bottle all-in-one adhesives - AdheSe One (AHO), Adper Easy Bond (EB), Bond Force (BF), G-Bond (GB), iBond Self Etch (IB), One Coat 7.0 (OC), OptiBond All-in-one (OPA), Clearfil Tri-S-Bond (TSB), Xeno V (XV). All teeth were restored using Filtek Z250 placed in three (one horizontal, two oblique) increments. Enamel margins were evaluated following 21 days of water storage, after thermocycling (2000 cycles: 5°C to 55°C), and after mechanical loading (150,000 cycles, 50 N). After each step, replicas were produced and quantitative SEM margin analysis was performed (200X) using defined criteria. Results: The median values of % "continuous margin" following TC and ML, respectively, were: OPT(98.6/96.2), CSE(95.4/90.9), BF(81.7/68.1), GB(81.1/65.0), OPA(83.0/68.1), OC(64.1/41.3), TSB(59.3/42.2), EB(57.1/42.6), IB(38.4/27.6), PLP(36.6/21.5), XV(45.0/30.0), AHO(17.7/5.4). Statistical evaluation (Kruskal-Wallis test with Bonferroni adjustment, p 0.05) revealed the following ranking for ML: OPT=CSE>BF=OPA=GB>OC=EB=TSB=XV =IB=PLP>AHO. Conclusion: All one-bottle all-in-one adhesives exhibited statistically significant lower marginal qualities in enamel compared to the etch-and-rinse system OPF and the two-step self-etching system CSE. The results obtained for GB, OPA and BF, however, were better than for the other all-in-one adhesives. Keywords: marginal quality evaluation, Class I, adhesive system effectiveness, thermocycling, mechanical loading

Purpose: This study compared microtensile bond strength (µTBS) of six simplified adhesive systems and an etch-andrinse, one-bottle adhesive system to intact enamel. Materials and Methods: Twenty-eight sound incisor teeth were cut at the cementoenamel junction (CEJ) under water cooling. The enamel surfaces were cleaned with pumice, randomly assigned to seven groups and treated with one of the following adhesives: Hybrid Bond (Sun Medical); AdheSE One (Ivoclar/Vivadent); One Coat 7.0 (Coltene/Whaledent); Danville Experimental (Danville Materials); Clearfil S3 Bond (Kuraray); G Bond (GC); and Prelude Total-etch (Danville Materials) as control. Composite resin (Clearfil AP-X, Kuraray) buildups were created and after 24 h, the teeth were sectioned into beams of 1.0 mm2 cross-sectional area. Each beam was tested in a microtensile tester (Bisco) at a crosshead speed of 1 mm/min. Data were calculated as MPa and analyzed by one-way ANOVA. Multiple comparisons were done using the Tukey test. Results: µTBS values of adhesives to intact enamel were as follows (mean ± SD; different letters indicate statistically different groups, p 0.05): Hybrid Bond: 15.62 ± 3.90a; AdheSE One: 17.29 ± 3.88ab; One Coat 7.0: 19.59 ± 3.95abc; Danville Experimental: 18.65 ± 5.33abc; Clearfil S3 Bond:20.89 ± 2.96bcd; G Bond: 23.49 ± 4.21cd; Prelude Totaletch: 25.79 ± 5.24d. Conclusions: Clearfil S3 Bond and G Bond showed bond strength similar to Prelude Total-etch (p = 0.064). The other simplified adhesives showed a similar performance (p = 0.239), however, µTBS values to intact enamel of these systems were lower than those obtained by Prelude Total-etch (p 0.05). Keywords: all-in-one adhesives, intact enamel, enamel bonding, prismless layer, self-etching primer, microtensile

Purpose: To assess the detrimental effects that polymerization contraction causes on the interfacial microtensile bond strength (µTBS) to dentin of three light-curing resin composites: two conventional bis-GMA-based composite resins (Filtek Z250, TPH Spectrum) and a low shrinkage material (Filtek Silorane [SIL]). Materials and Methods: Flat surfaces of labial dentin were made in 46 bovine teeth and restored in single (group A) or in three separate (group B) one-increment visible-light cured resin composite blocks, with similar locations among teeth. After 24 h, restored teeth were sectioned perpendicular to interfaces, producing rectangular compound specimens (385 specimens were produced in group A, and 132 in group B), and submitted to tension (crosshead speed 1mm/min) until failure. µTBS results were adjusted to bonded area and transformed to percentages of maximum values within each tooth (PTens). In A groups, distances of specimens to the gingival ends of each restoration were transformed to PDistances: the percentage of that distance within its specimen. Results: Spearman's nonparametric correlation test showed that for Z250, TPH and SIL, in A groups, a material's correlation coefficient was positive for the first half of restorations (0% to 50% PDistances) and negative for the second (50% to 100%). For all materials, PTens values in extremes of restorations (pooled 0 and 100% PDistances) in A groups were smaller than corresponding values in B groups. These differences were statistically significantly (Student's t-test) only for Z250 and TPH. Conclusion: Even in cases of favorable configuration factor, polymerization shrinkage in large restorations can reduce interface mechanical characteristics. The relevance of this decrease has still to be established. Keywords: polymerization contraction stress, silorane, µTBS, Weibull analysis

Purpose: This study examined the effect of dentin pretreatment with acetone or ethanol on bonding of one-bottle self-etching vs two-step self-etching adhesives to evaluate the effect of hydration on bond strength. Materials and Methods: The bond strengths of resins were measured using two one-bottle and two two-step selfetching adhesives that bonded to wet dentin (control), or acetone- or ethanol-pretreated dentin. Wet dentin is the normal substrate for bond testing, and in the pretreatment groups, 95% acetone or ethanol was applied to the dentin surface for 30 s before bonding. Weight of resin adhesives before and after evaporation was measured to evaluate the extent of the solvent contents in the adhesives. Furthermore, phase separation of adhesives was morophologically investigated by in situ light-microscopic observation to evaluate the hydrophilicity of the adhesive resins. Results: The bond strengths of the acetone and ethanol groups for one-bottle adhesives were significantly greater than for the control (p 0.05). However, significantly lower bond strengths were found in the pretreatment groups for the two-step self-etching adhesives (p 0.05). Conclusion: The bond strength depended on the wetness of the bonding substrate for both adhesive groups, with a positive effect in bond strength for one-bottle adhesives and a negative effect for two-bottle self-etching adhesives. The acetone- or ethanol-pretreated dentin surfaces may provide an improved substrate for resin adhesion of hydrophilic self-etching adhesives such as one-bottle self-etching adhesives due to dentin dehydration. Keywords: self-etching adhesive, acetone, ethanol, water, pretreatment, bond strength, phase separation, dehydration

Purpose: To evaluate the bond strength of glass fiber posts to intraradicular dentin when cemented with self-etching and self-adhesive resin cements. Materials and Methods: Forty-eight single-rooted human teeth were decoronated, endodontically treated, post-space prepared and divided into 8 groups (n = 6). The glass fiber posts used were: Exacto (EA) (Angelus) and everStick (ES) (StichTeck), which were cemented with two self-adhesive resin cements: BisCem (BIS) (Bisco) and Rely-X Unicem (UNI) (3M/ESPE), and two self-etching resin cements: Esthetic Cementing System NAC100 (NAC) (Kuraray) and Panavia-F (PAN) (Kuraray). Specimens were thermocycled between 5°C and 55 °C for 1000 cycles and stored in water at 37°C for 1 month. Four 1-mm-thick (in cross section) rods were obtained from the cervical region of the roots. Specimens were then subjected to microtensile testing in a special machine (BISCO; Schaumburg, IL, USA) or a crosshead speed of 0.5 mm/min. Microtensile bond strength (µTBS) data were analyzed with two-way ANOVA and Tukey's tests. Results: Means (and SD) of µTBS (MPa) were: EA/PAN: 10.3 (4.1), EA/NAC: 14 (5.1) EA/BIS: 16.4 (4.8), EA/UNI: 19.8 (5.1), ES/PAN: 25.9 (6.1), ES/NAC: 29.1 (7), ES/BIS: 28.9 (6), ES/UNI: 30.5 (6.6). ANOVA indicated significant differences among the groups (p 0.001). Mean µTBS values obtained with ES post were significantly higher than those obtained with EA (p 0.001). For EA, Tukey's test indicated that higher µTBS means were obtained with the self-adhesive resin cements (BIS and UNI), which were statistically significantly different (p 0.05) from values obtained with the self-etching resin cements (PAN and NAC). Different cements had no significant effects on the bond strength values of ES post (p > 0.05). µTBS values obtained with ES post were significantly higher than those obtained with EA post irrespective of the resin cement used. Conclusion: everStick posts resulted in the highest mean µTBS values with all cements. Self-adhesive cements performed well in terms of bond strength. Keywords: glass-fiber posts, resin cements, microtensile bond strength, root dentin

Purpose: To investigate the depth of nanoleakage of four luting agents for bonding fiber posts after thermomechanical fatigue. Materials and Methods: Twenty-four extracted human anterior teeth were endodontically treated, sectioned at the cementoenamel junction, and restored with fiber posts using four commercially available resin cements with the corresponding core buildup materials (n = 6): Panavia F 2.0/Clearfil DC Core Automix (Kuraray), Variolink II/Multicore Flow (Ivoclar Vivadent), RelyX Unicem/Filtek Z250 (3M ESPE), and Multilink Sprint/Multicore Flow (Ivoclar Vivadent). The specimens received all-ceramic crowns and were subjected to thermomechanical fatigue (1.2 million cycles). After cutting off the crowns, the roots were isolated with nail polish except for a 1-mm rim around the root canal, and immersed in 50 wt% ammoniacal silver nitrate solution for 24 h. The specimens were sectioned perpendicular to the long axis of the tooth into four slices, fixed, dehydrated, and processed for FE-SEM. Leakage was analyzed using backscattered FE-SEM and EDS. Results: The depth of nanoleakage was significantly affected by the factor resin cement (p 0.015; Kruskall-Wallis). Multilink Sprint resulted in significantly deeper penetration of silver particles than the other materials (p 0.05; Mann Whitney U-Test). Conclusion: Hybridization of the root canal dentin created by self-etching or etch-and-rinse adhesive systems demonstrated distinctive nanoleakage up to 0.8 mm, whereas the self-adhesive resin cement RelyX Unicem was able to prevent distinctive leakage at this penetration depth. However, none of the investigated luting systems would be able to hermetically seal the root canal if leakage occurred around the margins of the coronal restoration. Keywords: root canal dentin, resin cement, FE-SEM, nanoleakage, fiber post

Purpose: The aim of this study was to measure siloxane quantity, pH value, and resin wettability on ceramics silanized by five silane coupling agents, and to test the correlation of these parameters of silane coupling agents with bond durability between a machinable glass ceramic and resin cements. Materials and Methods: 1.5-mm-thick ceramic plates (ProCAD, Ivoclar Vivadent) were polished, cleaned, and bonded with ten combinations of five silane coupling agents (Monobond S [Ivoclar Vivadent], Rely X Ceramic Primer [3M], Clearfil Ceramic Primer [Kuraray], GC Ceramic Primer [GC], Porcelain Liner M [Sun Medical]) and two dual-curing resin cements (VariolinkII [VLII, Ivoclar Vivadent], Linkmax HV [LMHV, GC]). Their microshear bond strength was measured after 0, 10,000, and 30,000 thermal cycles. Siloxane quantity, pH value of silane coupling agents and contact angle of Heliobond (Ivoclar Vivadent) to silanized ceramic were measured using a FTIR spectrophotometer, pH-indicator strips, and a contact-angle meter, respectively. Bond strength data were analyzed by three-way ANOVA. For each cement, Pearson's correlation coefficient was calculated to analyze possible correlation between bond strength under different thermocycling conditions and absorbance peak of siloxane, pH value of silane coupling agents, and contact angle of resin to the silanized ceramic surface. Results: The bond strength of ceramic was significantly influenced by the silane coupling agent and thermal cycles, not by resin cement. For both cements, only a negative correlation was found to be significant between the contact angle of resin to silanized ceramic surfaces and bond strength after 30,000 thermal cycles. Conclusion: The better the wettability of resin on different silanized ceramic surfaces could improve their bond durability. Keywords: silane coupling agent, contact angle, pH, siloxane, dual-curing resin cement, machinable ceramic, microshear bond strength

Purpose: The aim of the present study was to assess the influence of pre-treatments of zirconia by sandblasting and/or heat treatment on the flexural strength of zirconia and debonding/crack-initiation strength of porcelain-veneered zirconia ceramic. Materials and Methods: Zirconia ceramic specimens were divided into four groups according to treatment (grinding as controls, sandblasting, heat treatment at 1000°C for 10 min, and heat treatment after sandblasting). The porcelain- veneered zirconia specimens were also prepared. The zirconia specimens were subjected to three-point bending tests, and flexural strength was calculated. The debonding/crack-initiation strength of porcelain-veneered zirconia ceramic was measured according to ISO 9693. X-ray diffractometry (XRD) was used to estimate the relative amount of monoclinic phase. Results: There was no significant difference in flexural strength between the four treatments (p > 0.05). The highest amount of monoclinic phase was found after sandblasting. No monoclinic phase was obtained from heat treatment and heat treatment after sandblasting groups, and these two groups showed significantly higher debonding/crack-initiation strength than other two groups (p 0.05). All specimens failed within the veneering porcelain. No elements of veneering porcelain were detected on the zirconia side at the interface using EPMA (electron probe microanalyzer). Conclusion: The present study suggests that the pre-treatment of zirconia with heat treatment after sandblasting prior to firing porcelain does not affect the debonding/crack-initiation strength of porcelain-veneered zirconia ceramic. Keywords: zirconia, sandblasting, heat treatment, debonding/crack-initiation strength

Purpose: This study compared shear bond strength and type of bond failure between a highly cross-linked tooth and different denture base polymers. Materials and Methods: Cross-linked denture teeth were bonded to either a heat-, an auto-, a microwave-polymerized denture base resin or a relatively new injection-molded, microwave-polymerizable polyurethane-based resin. Six experimental groups were established for each of the shear and peel tests. In four of the groups, teeth were used as received and bonded to each of the denture base resins; in the remaining two groups, they were treated with dichloromethane to determine its effect on the bonding with heat or auto-polymerized denture base resins. Bond strength was determined by compressive load applied at 45 degrees on the palatal surface of each tooth until fracture; the type of bond failure was assessed by the peel test. Results: The results showed that heat-cured PMMA groups failed cohesively and demonstrated significantly higher bond strengths than the other resins used. The application of dichloromethane on the ridge lap areas of teeth resulted in a significant improvement of bond strengths in heat- and auto-cured resins. Conclusion: Within the limitations of this experimental study, the results suggest that type of denture base material and processing methods may have an influence upon the bond strength between interpenetrating polymer network (IPN) denture teeth and base materials. Treatment of denture teeth with dichloromethane could provide substantial improvement in the bond strength of teeth with heat and auto-cured denture base resins; however, this finding should be validated in further investigations on the long-term effect of such treatment on the bond strength. Keywords: adhesion, IPN (interpenetrating polymer network) denture teeth, mechanical test, mechanical properties, polymethylmethacrylate