The Journal of Adhesive Dentistry, 06/2014

Purpose: To evaluate the effect of enzyme-based (Papacárie) and sodium-hypochlorite-based (Carisolv) chemomechanical caries removal methods on bonding of self-etching adhesives to caries-affected dentin, in comparison to the standard rotary-instrument caries removal method. Materials and Methods: Seventy-eight carious permanent molars exhibiting frank cavitation into dentin were used. Forty-eight teeth were randomly divided into three groups, according to the caries excavation methods: (i) Papacárie, (ii) Carisolv and (iii) a round steel bur. After caries removal, each group was subdivided into two groups for two-step (Clearfil SE Bond) or one-step (Clearfil S3 Bond) self-etching adhesive application and resin composite buildups. Bonded specimens were sectioned into beams for microtensile bond strength testing. Bond strength data were analyzed using three-way ANOVA and Tukey's test. For interfacial nanoleakage evaluation using a field-emission scanning electron microscope, caries was similarly removed from the remaining thirty carious molars, bonding was performed as for bond strength testing, and the teeth were sectioned. Results: Results of three-way ANOVA revealed that bond strength was significantly affected by "adhesive" (p 0.001) and "dentin" (p 0.001), but not "caries excavation methods" (p > 0.05). The bond strength of the two-step self-etching adhesive was significantly higher than that of the one-step self-etching adhesive (p 0.001). Conversely, the bond strength of self-etching adhesives to sound dentin was significantly higher than to residual caries-affected dentin (p 0.001). Greater silver penetration was observed in the bonded interfaces of residual caries-affected dentin and in interfaces bonded with the one-step self-etching adhesive vs those bonded with the two-step self-etching adhesive. Conclusion: Chemomechanical caries removal did not affect the bonding of self-etching adhesives to cariesaffected dentin as compared to caries excavation with rotary instruments. Keywords: chemomechanical caries removal, Carisolv, MDP, Papacárie, self-etching adhesives, caries-affected dentin

Purpose: To assess the resin microtensile bond strength (MTBS) and the monomer conversion (MC) of indirect composite resin restorations made of three different materials. Materials and Methods: Two light-polymerized direct materials (Filtek Z100 and Premise) and one light- and heat-polymerized indirect material (Premise Indirect) were used. For MTBS testing, 42 cylindrical samples were fabricated (7 pairs per material). Surface conditioning included airborne-particle abrasion, cleaning, and application of a silane. Cylinders were bonded to each other using adhesive resin (Optibond FL). Specimens were stored in water for 24 h. Another 15 cylinders (5 per material) were fabricated for MC measurements (FT-IR) immediately and at 24 h. The MTBS data were submitted to one-way ANOVA and the MC to two-way ANOVA (material and storage time) (α = 0.05), followed by post-hoc comparisons with the Tukey test. Results: The MTBS to Z100 was 72.2 MPa, significantly higher than that to Premise (48.4 MPa) and Premise Indirect (52.7 MPa). The immediate MC was similar for all materials (range 51% to 56%) and significantly increased at 24 h (range 57% to 66%), except for Z100. Premise Indirect showed the highest MC (66% at 24 h). Conclusion: Z100 showed better "bondability" than Premise and Premise Indirect. Premise Indirect, with its heat initiator, did not present a higher MC. Keywords: adhesion, bond strength, direct composite resin, dental materials, indirect composite resin, monomer conversion

Purpose: To evaluate the microleakage of Cerec 3, IPS e.max Press, and Turkom-Cera inlays cemented with three self-adhesive resin cements. Materials and Methods: Ninety standardized class III MOD cavities were prepared in intact human mandibular third molars. Ceramic inlays were fabricated according to the manufacturer's instructions and were cemented using three self-adhesive resin cements (RelyX Unicem, Smartcem 2, and SpeedCEM). The specimens were stored in distilled water at 37°C for 24 h and subjected to 1000 thermocycles in water between 5°C and 55°C with a dwell time of 30 s. Subsequently, the specimens were subjected to 100,000 cycles of mechanical loading of 50 N at 1.6 Hz in 37°C water. The specimens were immersed in 0.5% basic fuchsine for 24 h and were sectioned using a low-speed diamond blade. The percentage of dye leakage at the tooth/restoration interface was measured and compared by Kruskal-Wallis tests with Bonferonni correction and Mann-Whitney U-tests at a significance level of p 0.05. Results: Microleakage at the RelyX Unicem interface was lower than that with Smartcem 2 and SpeedCEM resin cements (p 0.05). Microleakage of the Turkom-Cera system was higher than Cerec 3 and IPS e.max Press ceramic inlays (p 0.05). Conclusions: Regardless of the ceramic system and self-adhesive resin cement used, dentin margins were associated with higher microleakage than enamel margins. Keywords: microleakage, inlay ceramic systems, resin cements

Purpose: To evaluate the effect of different surface treatments on the microtensile bond strength (μTBS) of novel CAD/CAM restorative materials to self-adhesive resin cement. Materials and Methods: Two types of CAD/CAM restorative materials (Vita Enamic [VE] and Lava Ultimate [LU]) were used. The specimens were divided into five groups in each test according to the surface treatment performed; Gr 1 (control; no treatment), Gr 2 (sandblasted [SB]), Gr 3 (SB + silane [S]), Gr 4 (hydrofluoric acid [HF]), and Gr 5 (HF + S). A dual-curing self-adhesive resin cement (Bifix SE [BF]) was applied to each group for testing the adhesion after 24 h of storage in distilled water or after 30 days using the μTBS test. Following fracture testing, specimens were examined with a stereomicroscope and SEM. Surface roughness and morphology of the CAD/CAM restorative materials were characterized after treatment. Data were analyzed using ANOVA and Tukey's test. Results: The surface treatment, type of CAD/CAM restorative material, and water storage periods showed a significant effect on the μTBS (p 0.001). For the LU/BF system, there was no significant difference in the bond strength values between different surface treatments (p > 0.05). On the other hand, for the VE/BF system, surface treatment with HF + S showed higher bond strength values compared with SB and HF surface treatments (p 0.05). Surface roughness and SEM analyses showed that the surface topography of CAD/CAM restorative materials was modified after treatments. Conclusion: The effect of surface treatments on the bond strength of novel CAD/CAM restorative materials to resin cement is material dependent. The VE/BF CAD/CAM material provided higher bond strength values compared with the LU/BF CAD/CAM material. Keywords: adhesion, microtensile, polymer-infiltrated ceramic network, resin cement, resin nanoceramic, surface roughness, surface treatments

Purpose: To evaluate the bonding performance of self-adhesive resin cements to zirconia and lithium disilicate in self- and dual-curing modes before and after thermocycling. Materials and Methods: Rectangular bars (3 mm high, 3 mm wide, 9 mm long) were manufactured from zirconia (Vita In-Ceram YZ for inLab, VITA) and lithium disilicate blocks (IPS e.max Press, Ivoclar Vivadent) (n = 240 per material). Zirconia bars were sandblasted (35 μm Al2O3, 1.5 bar pressure). Lithium disilicate bars were HF etched (20 s, IPS Ceramic Etching Gel, Ivoclar Vivadent) and silanized with ESPE Sil (3M ESPE). Forty bars of zirconia were luted in twos perpendicular to each other as were 40 bars of lithium disilicate using RelyX Unicem Automix 2 (3M ESPE), G-Cem LinkAce (GC Europe) or Maxcem Elite (Kerr) in self- or dual-curing mode. Half of the specimens from each material were submitted to tensile bond strength (TBS) testing after 24-h storage in distilled water at 37°C, and half underwent TBS testing after thermocycling (5000 cycles, 5°C/55°C, 30-s dwell time). Bond strength values for each bonding substrate were analyzed using one-way ANOVA (Student-Newman- Keuls, α = 0.05). Results: On zirconia, dual-curing resulted in significantly (p 0.05) higher tensile bond strengths compared to self-curing, with the exception of RelyX Unicem 2 after thermocycling. Thermocycling significantly (p 0.05) reduced the tensile bond strength of Maxcem Elite to zirconia in both curing modes. The TBS of self-adhesive cements to lithium disilicate showed no significant (p > 0.05) difference between the different curing modes and after thermocycling. Conclusion: For most of the investigated self-adhesive cements, bond strengths to zirconia were increased by dual curing; this was not true for lithium disilicate. For luting on zirconia with self-adhesive cements, dual curing is strongly recommended in clinical situations. Keywords: self-adhesive resin cements, tensile bond strength, zirconia, lithium disilicate, thermocycling

Purpose: To evaluate the influence of the internal structure of lithium disilicate glass ceramics (LDC) on the microtensile bond strength to a resin adhesive using two surface treatments. Materials and Methods: Milling blocks of three types of LDC were sectioned (4 mm thick) using a precision cutting machine: IPS Empress 2 (conventional LDC), IPSe.max CAD (a refined crystal high strength LDC), and Celtra (zirconia reinforced LDC). Cut specimens received crystallization heat treatment as suggested by the manufacturers. Two surface treatments were performed on each group: hydrofluoric acid etching (HF) and airborne particle abrasion using 50-μm glass beads, while the as-cut surface served as control. Treated surfaces were examined using scanning electron microscopy (SEM). The disks were coated with a silane primer and bonded to pre-aged resin composite disks (Tetric EvoCeram) using a resin adhesive (Variolink II) and then stored in water for 3 months. Bonded specimens were sectioned into micro-bars (1 x 1 x 6 mm) and microtensile bond strength test (MTBS) was performed. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (α = 0.05). Results: Statistical analysis revealed significant differences in microtensile bond strength values between different LDCs (F = 67, p 0.001), different surface treatments (F=232, p 0.001), and interaction between LDC and surface treatments (F = 10.6, p 0.001). Microtensile bond strength of Celtra ceramic (30.4 ± 4.6 MPa) was significantly higher than both IPS Empress 2 (21.5 ± 5.9 MPa) and IPSe.max ceramics (25.8 ± 4.8 MPa), which had almost comparable MTBS values. SEM images demonstrated homogenous glassy matrix and reinforcing zirconia fillers characteristic of Celtra ceramic. Heat treatment resulted in growth and maturation of lithium disilicate crystals. Particle abrasion resulted in abrasion of the glass matrix and exposure of lithium disilicate crystals, while HF etching produced a microrough surface, which resulted in higher MTBS values and reduction in the percentage of adhesive failure for all groups. Conclusions: Within the limitations of this study, bond strength to lithium disilicate ceramics depends on proper surface treatment and on the chemical composition of the glass ceramic. Keywords: MTBS, bond, lithium disilicate, SEM

Purpose: The surface roughness of zirconia specimens and the bond strength of zirconia and resin cements were evaluated after selective infiltrated etching (SIE) surface treatment using a modified glass agent. Materials and Methods: One hundred twenty zirconia specimens were divided into four groups according to surface treatment method: untreated control (C), airborne particle abrasion (A), airborne particle abrasion followed by SIE treatment using a modified glass agent (A-SIE), and SIE treatment using a modified glass agent without airborne particle abrasion (SIE). The surface morphology and roughness of the specimens were examined before and after treatment using scanning electron and atomic force microscopy. The specimens were then cemented to resin blocks with a 4-META resin luting system (Superbond C&B). The shear bond strength of the zirconia/ resin interface was measured before and after thermocycling and fatigue testing. Results: The surface roughness and shear bond strength values of the SIE group were higher than those of the other three zirconia groups. The surface roughness (Ra) values were 8.10, 8.34, 9.42, and 12.42 μm for the C, A, A-SIE, and SIE groups, respectively, with significant differences between SIE and the C and A groups (p 0.05). The shear bond strength values before thermocycling and fatigue testing were 23.37, 23.38, 25.82, and 28.67 MPa for the C, A, A-SIE, and SIE groups, respectively. These values did not decrease after 10,000 cycles of thermocycling for the surface-treated groups, but did decrease for the untreated control group (C). Conclusion: SIE treatment using a modified glass agent can increase surface roughness and the bond strength between zirconia and resin cements. The shear bond strength did not decrease after thermocycling and fatigue testing. Keywords: zirconia, bond strength, selective infiltrated etching, surface modification, thermocycling test

Purpose: To evaluate post-to-composite bonds in terms of their durability, achieved either by physical vapor deposition (PVD) or tribochemical silica coating (TSC) compared to coupling strategies for fiber posts at chairside. Materials and Methods: Thirty uncoated fiber posts (DT Light) each were either left untreated (control) or silanized with a one-bottle (Monobond Plus) or a two-bottle (Clearfil SE Bond/Porcelain Bond Activator) silane at the chairside. Thirty coated fiber posts each had already been silica coated and silanized by the manufacturer using PVD (DT Light SL) or TSC (DentinPost Coated) deposition techniques. Surface analysis was carried out by profilometry and x-ray microanalysis. All the posts were surrounded by 2-mm-thick disks of a dual-curing composite resin (MultiCore Flow). After water storage for 24 h at 37°C, the specimens in each group were randomly divided into three subgroups (n = 10) and subjected to 0, 1500, and 20,000 thermocycles (5°C to 55°C) prior to push-out testing. Failure modes were evaluated by optical and scanning electron microscopy. The statistical significance was determined with two-way ANOVA, the Student-Newman-Keuls test, and Fisher's exact test. Results: The conditioned posts had significantly higher interfacial bond strengths than the control posts after thermocycling (p 0.05). Extended thermocycling significantly reduced the interfacial strength of chairside silanized posts (p 0.05). This effect was not significant with industrially coated posts (p > 0.05). Coatings deposited by TSC reached the highest bond values (p 0.05) and showed predominantly adhesive failures in the form of coating delamination (p 0.0001). In contrast, the other coupling strategies showed significantly lower values and adhesive failures between the post and the composite. Conclusion: PVD and TSC techniques enhanced the bond durability of fiber posts. TSC led to a superior post-tocomposite bond, probably based on more effective micromechanical adhesion due to the higher surface roughness. Keywords: fiber post, composite resin, physical vapor deposition, tribochemical silica coating, silanization, bond durability

Purpose: To investigate whether the placement of a methacrylate root canal sealer or a conventional epoxy root canal sealer in two steps increases their dislocation resistance when compared to a one-step placement procedure. Materials and Methods: Eighty single-rooted teeth were randomly allocated to 4 groups (n = 20). All canals were instrumented to size 40, 0.06 taper and irrigated according to a standardized protocol. Root canal filling was conducted as follows: group 1: methacrylate sealer placed in two steps; group 2: methacrylate sealer placed in one step; group 3: epoxy sealer placed in two steps; group 4: epoxy sealer placed in one step. After setting, thin slices at different root levels were obtained and submitted to push-out testing. Results were analyzed with non-parametric tests to compare the two-step procedures to their one-step counterparts. Failure modes were determined by stereomicroscopy. Random untested methacrylate sealer specimens were also examined with scanning electron microscopy. Results: At each root level, dislocation resistance was significantly higher for the two-step procedure than for the one-step procedure using the methacrylate sealer (p = 0.003, p = 0.005, p 0.001) but not the epoxy sealer (p = 0.83, p = 0.1, p = 0.06). Among root levels, there were no significant differences in dislocation resistance in the methacrylate sealer two-step group, while all other groups showed differences. Conclusion: A two-step placement procedure resulted in significantly higher dislocation resistance for the methacrylate sealer but not for the epoxy sealer. Keywords: adhesion, configuration factor, dislocation resistance, methacrylate resin, polymerization shrinkage, root canal sealer

Purpose: To investigate the clinical performance of a silorane-based composite resin used for repairing dimethacrylate- based composite restorations. Materials and Methods: One operator repaired defective dimethacrylate-based resin restorations that were randomly assigned to one of two treatment groups: control (n = 50), repaired with Adper SE Plus and Filtek P60 Posterior Restorative (3M ESPE); or test (n = 50), repaired with P90 System Adhesive Self-Etch Primer and Bond and Filtek P90 Low Shrink Posterior Restorative (3M ESPE). After 1 week, restorations were finished and polished. Two calibrated examiners (weighted Kappa ≥ 0.78) evaluated the repaired restorations, blindly and independently, at baseline, after 6 months, 1 and 2 years. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The restorations were classified as Alfa, Bravo, or Charlie, according to modified US Public Health Service criteria. Variation in the levels of clinical parameters over time was evaluated by Friedman's ANOVA (α = 0.05). The Mann-Whitney test assessed the differences between the materials for all clinical criteria at baseline, 6-month, 1- and 2-year recalls (α = 0.05). The Wilcoxon test compared each composite resin for all clinical criteria at the same recalls (α = 0.05). Results: After two years, 79 repaired restorations were re-examined. No statistically significant differences were found between the materials at baseline or at the 2-year recall (p > 0.05). Comparing baseline and 2-year recall, there was a statistically significant difference for marginal discoloration (p = 0.029) in silorane-based composite restorations. Conclusion: After two years, the clinical performance of the silorane-based composite was similar to that of the dimethacrylate-based composite when used to make repairs. Keywords: low-shrinkage silorane-based composite, dimethacrylate-based composite, resin-based restoration, repair

Purpose: To evaluate the 10-year durability of a nanohybrid resin composite in Class II restorations in a randomized controlled intraindividual comparison with its conventional hybrid resin composite predecessor. Materials and Methods: Each of 52 participants received at least two Class II restorations that were as similar as possible. The cavities were chosen at random to be restored with a nanohybrid resin composite (Excite/Tetric EvoCeram (TEC); n = 61) and a conventional hybrid (Excite/Tetric Ceram (TC); n = 61). The restorations were evaluated with slightly modified USPHS criteria at baseline and then annually for 10 years. The overall performance of the experimental restorations was tested after intra-individual comparison and their ranking was tested using Friedman's two-way ANOVA. The level of significance was set at 5%. Results: Four patient drop-outs with 8 restorations (4TEC, 4TC) were registered during the follow-up. A prediction of the caries risk showed that 16 of the evaluated 52 patients were considered as high risk patients. In total, 22 restorations, 11 TEC (3 premolars, 8 molars) and 11 TC (3 premolars, 8 molars) restorations failed during the 10 years. The main reason for failure was secondary caries (50%). 63% of the recurrent caries lesions were found in high caries risk participants. The overall success rate at 10 years was 80.7%, with an annual failure rate of 1.9%. No statistically significant difference was found in the overall survival rate between the two investigated resin composites. Conclusion: The nanohybrid and the conventional hybrid resin composite showed good clinical effectiveness in extensive Class II restorations during the 10-year study. Keywords: dental restorations, clinical, nanofiller, resin composite, posterior