The Journal of Adhesive Dentistry, 02/2006

Purpose: This study examined the ultrastructure and microtensile bond strengths (TBS) of self-etching (with different acidity) and conventional adhesive systems bonded to unground enamel. Materials and Methods: Resin composite (Filtek Z250) buildups were bonded to unground enamel surfaces of third molars after adhesive application with the following materials: Clearfil SE Bond (CSE); Optibond Solo Plus Self-Etch (OP); Tyrian Self Priming Etching (TY), and the controls Scotchbond Multi-Purpose Plus (SBMP) and Single Bond (SB). Six teeth were assigned to each material. After storage in water for 24 h at 37°C, the bonded specimens were sectioned into beams of approximately 0.8 mm2 and subsequently subjected to µTBS testing at a crosshead speed of 0.5 mm/min. The average values were subjected to one-way ANOVA (α = 0.05). The effect of surface conditioning of each material was observed under scanning electron microscopy (SEM). Results: The highest resin-enamel bond strength was observed for SBMP (22.7 ± 5.2) and SB (26.7 ± 5.2 MPa). The lowest mean bond strengths were 10.9 ± 3.2 and 7.8 ± 1.5 MPa for TY and OP, respectively. CSE showed an intermediate performance (18.7 ± 4.6 MPa). An overall increase in porosity was evident along the entire enamel surface treated with the self-etching primers; however, no selective demineralization similar to that with 35% phosphoric acid was observed. Conclusion: The highest bond strength means and the more retentive etching pattern were observed for the two-step etch-and-rinse adhesives. Among the self-etching systems studied, Clearfil SE Bond should be preferred. Keywords: adhesive system, bonding, enamel morphology

Purpose: This study was designed to analyze the influence of desensitizing procedures on dentin bond strength. Materials and Methods: Forty bovine incisors were used, divided into four groups (n = 10): G1: control; G2: Gluma Desensitizer (Heraeus Kulzer); G3: Oxa-Gel (Art-Dent); G4: low-intensity laser (MMOptics). The buccal surface was wet ground flat with 180-, 400- and 600-grit silicon carbide abrasive paper to expose midcoronal dentin and create a uniform surface. After the application of the desensitizing agents to the exposed dentin, the specimens were etched with 35% phosphoric acid for 30 s, and an adhesive (Single Bond) was applied and light cured. A 4-mm high crown of composite resin (Filtek Z250) was then built up. Specimens were trimmed to an hourglass shape with cross sections of 1 mm2. Each specimen was individually fractured by a microtensile testing machine at a crosshead speed of 0.5 mm/min. The data, recorded in MPa, were analyzed with one-way ANOVA and the Duncan test (p = 0.05). Results: Specimens treated with dentin desensitizers (except Gluma) yielded significantly lower mean bond strengths than nontreated control specimens. The mean values in MPa (±SD) were: G1: 13.4 (6.2); G2: 13.2 (4.8); G3: 7.15 (4.3); G4: 7.21 (4.6). Conclusions: Among the desensitizing agents studied, only Gluma Desensitizer did not detrimentally influence the bond strength values. It is a useful material for dentin desensitization. Keywords: dentin, desensitizer, microtensile bond strength

Purpose: The aim of this study was to determine the static load-bearing capacity of fractured incisors restored with the conventional adhesive-composite technique or by using fiber-reinforced composites (FRC). Materials and Methods: Twelve extracted sound maxillary incisors per group were prepared by cutting the incisal (one-third) part of the crown horizontally. Restorations were made using three techniques. Group A (control group) was restored by reattaching the original incisal edge to the tooth. Group B was restored using particulate filler composite (PFC). Group C was restored with PFC and FRC by adding a thin layer of FRC on the palatal surface of tooth. The bonding system used was the conventional etch system with primer and adhesive. All restored teeth were stored in water at room temperature for 24 h before they were statically loaded until fracture in a universal testing machine. Data were analyzed using ANOVA (p = 0.05). Failure modes were visually examined. Results: Group A (reattaching fractured incisal edge) revealed the lowest load-bearing values, whereas preparation of the new incisal part with PFC revealed 148% higher load-bearing values compared to Group A. Group C (teeth restored with FRC) revealed a 254% higher load-bearing capacity than the control group. ANOVA revealed that the restoration technique significantly affected load-bearing capacity (p < 0.001). The failure mode in Groups A and B was debonding of the restoration from the adhesive interface, while in group C, 50% of the teeth fractured below the cementoenamel junction. Conclusion: These results suggest that an incisally fractured tooth restored with a combination of PFC and FRC provide the highest load-bearing capacity. Keywords: fiber-reinforced composite, load-bearing capacity, incisal edge fracture, particulate filler composite resin

Purpose: To evaluate the fatigue resistance of the bond between dentin and glass-infiltrated alumina ceramic, using different luting protocols. Materials and Methods: The null hypothesis is that the fatigue resistance varies with the luting strategy. Forty blocks of In-Ceram Alumina were prepared, and one surface of each block was abraded with 110-µm aluminum oxide particles. Then, the blocks were luted to flat dentin surfaces of 40 human third molars, using 4 different luting strategies (luting system [LS]/ceramic surface conditioning [CSC]) (n=10): (G1) [LS] RelyX-Unicem/[CSC] airborne abrasion with 110-µm Al2O3 particles; (G2) [LS] One-Step + Duo-Link (bis-GMA-based resin)/[CSC] etching with 4% hydrofluoric acid + silane agent; (G3) [LS] ED-Primer + Panavia F (MDP-based resin)/[CSC] Al2O3; (G4) [LS] Scotchbond1+RelyX-ARC (bis-GMA-based resin)/[CSC] chairside tribochemical silica coating (air abrasion with 30-µm SiOx particles + silane). After 24 h of water storage at 37°C, the specimens were subjected to 106 fatigue cycles in shear with a sinusoidal load (0 to 21 N, 8 Hz frequency, 37°C water). A fatigue survivor score was given, considering the number of the fatigue cycles until fracture. The failure modes of failed specimens were observed in a SEM. Results: G3 (score = 5.9, 1 failure) and G4 (score = 6, no failures) were statistically similar (p = 0.33) and had significantly higher fatigue resistance than G1 (score = 3.9, 5 failures) and G2 (score = 3.7, 6 failures) (p < 0.03). SEM analysis of fractured specimens of G1 and G2 showed that almost all the failures were between ceramic and cement. Conclusion: The MDP-based resin cement + sandblasting with Al2O3 particles (G3) and bis-GMA-based resin cement + tribochemical silica coating (G4), both using the respective dentin bonding systems, were the best luting protocols for the alumina ceramic. The null hypothesis was confirmed. Keywords: fatigue resistance, alumina ceramic, luting systems, tribochemical silica coating

Purpose: To test the bond strength between a quartz-fiber-reinforced composite post (FRC) and a resin cement. The null hypothesis was that the bond strength can be increased by using a chairside tribochemical silica-coating system. Materials and Methods: Thirty quartz-FRCs (Light-Post) were divided into 3 groups according to the post surface treatment: G1) Conditioning with 32% phosphoric acid (1 min), applying a silane coupling agent; G2) etching with 10% hydrofluoric acid (1 min), silane application; G3) chairside tribochemical silica coating method (CoJet System): air abrasion with 30-µm SiOx-modified Al2O3 particles, silane application. Thereafter, the posts were cemented into a cylinder (5 mm diameter, 15 mm height) with a resin cement (Duo-Link). After cementation, the specimens were stored in distilled water (37°C/24 h) and sectioned along the x and y axes with a diamond wheel under cooling (Labcut 1010) to create nontrimmed bar specimens. Each specimen was attached with cyanoacrylate to an apparatus adapted for the microtensile test. Microtensile testing was conducted on a universal testing machine (1 mm/min). The data obtained were submitted to the one-way ANOVA and Tukey test (α = 0.05). Results: A significant influence of the conditioning methods was observed (p < 0.0001). The bond strength of G3 (15.14 ± 3.3) was significantly higher than the bond strengths of G1 (6.9 ± 2.3) and G2 (12.60 ± 2.8) (p = 0.000106 and p = 0.002631, respectively). Notwithstanding the groups, all the tested specimens showed adhesive failure between the resin cement and FRC. Conclusion: The chairside tribochemical system yielded the highest bond strength between resin cement and quartzfiber post. The null hypothesis was accepted (p < 0.0001). Keywords: bond strength, fiber post, surface conditioning, tribochemical silica coating, microtensile test

Purpose: The aim of this study was to evaluate the bond strengths between various resin composites used as core materials (Multicore Flow, Ivoclar-Vivadent; Tetric Flow, Ivoclar-Vivadent; Filtek Flow, 3M-ESPE; Tetric Ceram, Ivoclar-Vivadent; Filtek Z250, 3M-ESPE), and an FRC post (FRC Postec Plus, Ivoclar-Vivadent) by means of the microtensile nontrimming technique. Materials and Methods: Five experimental groups were used. For the microtensile nontrimming technique, 45 to 50 beam-shaped specimens per group were obtained from cylinders of core material, which had been built up around the post by progressively adding small increments of composite resin. Each specimen was loaded in tension until failure at either one of the two post/core interfaces present in each stick. The differences in interfacial bond strength among the groups were tested for statistical significance with the one-way ANOVA test, followed by the Dunnett test for post-hoc comparisons. Results: The measured bond strengths in MPa were 17.29 ± 6.02 for FRC+MultiCore Flow, 16.37 ± 6.92 for FRC+Tetric Flow, 13.14 ± 5.35 for FRC + Filtek Flow, 12.38 ± 4.34 for FRC + Tetric Ceram, and 10.75 ± 5.43 for FRC + Filtek Z250. The statistical analysis revealed that MultiCore Flow achieved significantly higher bond strengths than Filtek Flow (p = 0.03), Tetric Ceram (p < 0.001), and Filtek Z250 (p < 0.001). The bond strength of Tetric Flow was significantly higher than that of Filtek Z250 (p = 0.003). Conclusion: For core buildup on a fiber post, dual-cure composites appear to be preferable to light-curing composites. Keywords: prefabricated FRC post, core material, composite resin, dual-cure composites, bond strength, microtensile testing

Purpose: The aim of this clinical follow-up study was to determine the clinical performance of ormocer and a new nanofill composite material, lined or not lined with flowable composites, after 2 years. Materials and Methods: Occlusal restorations (n = 108) were placed in 54 patients with two symmetric restorations per patient. In one of the two restorations in each patient, cavities were first lined with the flowable composite material Admira Flow or Filtek Flow after applying the two-step total-etch one-bottle adhesive (Admira Bond) or single bond adhesive (Single Bond). Admira or Filtek Supreme was then applied. Restorations were examined using the USPHS modified Ryge criteria for retention, color matching, cavosurface marginal discoloration, anatomic form, marginal adaptation, surface texture, and secondary caries by two previously calibrated dentists. The overall performance of the restorations was evaluated by Wilcoxon signed ranks test. The chi-square test was used to determine differences in the performance of the restorations in which the flowable composite was applied first. Results: There was no secondary caries or postoperative sensitivity in any of the restorations at the 6-month, 1-year, and 2-year follow-up examinations. After 2 years, only one Admira restoration had failed; all other restorations were available for evaluation. There were no statistically significant differences among the materials regardless of the prior use of flowable material (p > 0.05). There was no statistically significant difference between the restorations with and without the prior application of flowable materials (p > 0.05). Conclusion: The clinical performance of occlusal restorations using ormocer or nanofill composite did not benefit from the additional use of the flowable composite. Both of the restorative materials exhibited ideal clinical performance. Keywords: ormocer, nanofill composite, flowable liner, clinical evaluation

Purpose: To investigate in vivo and in vitro Class II composite restorations performed with two matrix and wedge systems. Materials and Methods: One hundred nine Class II restorations were performed in 23 patients, 59 with metallic matrices and wooden wedges (group 1) and 50 with polyester matrices and reflective wedges (group 2). All cavities were restored using Single Bond and P-60 (3M ESPE). In the metal matrix group, polymerization was performed from the occlusal, and in the polyester group through the reflective wedge. To assess microleakage, 40 proximal standard slot cavities were prepared in 20 noncarious human third molars. In the mesial cavity, the gingival margin was located at the enamel level, and in the distal cavity at the cementum/ dentin. Specimens were randomly divided into two groups (n = 20) and restored with Single Bond, Z-250 (3M ESPE), and the same techniques used in the in vivo study: metal matrix/wooden wedge (group 1) and polyester matrix/reflective wedge (group 2). Specimens were thermocycled (500 times, 5°C to 55°C), then isolated with nail varnish and immersed in fuchsin for 8 h. Specimens were sectioned longitudinally and microleakage was assessed under magnification (40X) using a standard scoring system. Results: Data were subjected to the chi-square test, Mann-Whitney U-test, and Kruskal-Wallis H-test. Matrix systems presented similar results in the clinical evaluation and the in vitro microleakage test of Class II composite restorations. Dye leakage was minimal at enamel margins, and statistically lower (p < 0.05) than at cementum/dentin margins. Conclusion: The different matrix systems had no influence on clinical performance or in vitro sealing ability of Class II composite restorations. Keywords: dental leakage, Class II restorations, matrix bands, clinical trials