Microtensile bond strengths of composite to dentin treated with desensitizer products

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 mm(2). 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.82859

The effect of light-curing source and mode on microtensile bond strength to bovine dentin

Purpose: The purpose of this study was to evaluate the effects of different light-curing techniques on the microtensile bond strength of hybrid and packable resin composite to dentin. The null hypotheses were that different light-curing techniques do not affect the adhesion of resin composites to tooth structure and that different resin composites do not have a similar bond to dentin. Materials and Methods: One hundred four box-shaped buccal preparations were made and dentin/enamel adhesive was applied according to the manufacturer's instructions (Single Bond 3M ESPE). A hybrid resin composite (Filtek Z250, A2, 3M ESPE) or a packable resin composite (Solitaire 2, A2, Heraeus Kulzer) were inserted in bulk and polymerized using one of these techniques (n = 13): (a) Soft-start (SS) using a halogen lamp (QTH); (b) LED low intensity; (c) Plasma arc (PAC) curing for 6 s for packable resin composite and 3 s for the hybrid resin composite; (d) Conventional (C) QTH curing for 40 s. Afterwards, specimens were thermocycled 1,000 times between 5 degrees C and 55 degrees C in tap water, and were sectioned into beams with a rectangular cross-sectional area of approximately 1 mm(2). Microtensile bond strength testing was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. Results: Bond strength means +/- (SD) in MPa were: Filtek Z250: SSQTH = 17.9 (5.4); LED = 17.9 (6.4); PAC = 16.8 (6.8); CQTH = 16.1 (4.6). Solitaire 2: SSQTH = 12.4 (6.4); LED = 15.5 (4.3); PAC = 16.2 (4.4); CQTH = 13.8 (5.7). The data were structured in a split-plot design and analyzed by a two-way ANOVA and Tukey's tests (alpha = 0.05). Conclusion: The light-curing method did not significantly affect bond strengths. However, the bond strengths of the packable resin composite were significantly lower than those of the hybrid resin composite for all polymerization techniques, suggesting that the restorative material itself might be a more critical factor in adhesion than the curing method.81414

Nonvital tooth bleaching: A 2-year case report

A discolored, nonvital maxillary right central incisor was bleached with sodium perborate and water, used as a "walking" bleach. An excellent result was obtained, proving the efficiency of both the intracoronal bleaching technique and the materials employed. A clinical evaluation performed 2 years later revealed that the tooth was slightly stained but esthetically satisfactory.301174875

Effect of two different restorative techniques using resin-based composites on microleakage

Purpose: To evaluate in vitro the extent of microleakage of Class 11 cavities restored with two different brands of resin-based composite, one hybrid (Tetric Ceram) and the other "packable" (Surefil) taking into account two variables: the localization of the margins and the insertion technique. Methods: 100 bovine teeth, recently extracted, had standardized Class II slot cavities prepared on the mesial and distal surfaces with the gingival floor located on enamel or dentin, for a total 200 cavities. The teeth were randomly divided into eight groups of 25 teeth each (25 restorations in each group): (1) margin on dentin, restored with Surefil, bulk insertion; (2) margin on dentin, restored with Tetric Ceram, bulk insertion; (3) Margin on enamel, restored with Surefil, incremental technique; (4) margin on enamel, restored with Tetric Ceram, incremental technique; (5) margin on enamel, restored with Surefil, bulk insertion; (6) margin on enamel, restored with Tetric Ceram, bulk insertion; (7) margin on dentin, restored with Surefil, incremental technique; (8) margin on dentin, restored with Tetric Ceram, incremental technique. After this procedure, the teeth were subjected to 1000 thermocycles, stained with 2% methylene blue solution, and then sectioned in the mesiodistal direction. Dye penetration at tooh/restoration interface was scored based upon the extent of the dye using a light stereoscope x 35. Results: All groups showed considerable levels of microleakage at both dentin and enamel margins (P< 0.05). Restorations with margins in enamel using the hybrid resin-based composite with the incremental technique did not show statistically significant differences when compared to bulk placement. However, restorations with hybrid resin-based composite have significantly less microleakage than either bulk or incremental technique for the "packable" resin-based composite Surefil. As for the margins in dentin, Tetric Ceram in bulk placement did not differ from the incremental technique and Tetric in bulk placement had significantly less microleakage than Surefil either bulk or incremental technique. The hybrid resin-based composite with margins in dentin and incremental technique showed less microleakage than the "packable" resin in bulk placement.1729910

In vitro microleakage of composite restorations after nonvital bleaching

Objective: After bleaching treatment, esthetic restorations often need to be replaced due to color changes. Some papers have shown alterations in the bond of adhesive restorations to bleached teeth. The purpose of this study was to evaluate tooth and resin composite adhesion when submitted to nonvital dental bleaching. Method and materials: One hundred and twenty bovine teeth were assigned to 3 groups (n = 40). paste of sodium perborate and water; 37% carbamide peroxide gel; and no bleaching (control). After 3 weeks of continuous bleaching treatment, standardized Class V cavities were prepared at the cementoenamel junction and restored with Single Bond adhesive system and Z100 resin composite. The samples were thermocycled 1,500 times (5 +/-: 1 / 55 +/- 1 degreesC) with a 1-minute dwell time. Then, they were immersed in a 2% methylene blue solution (pH 7) for 4 hours, sectioned, and analyzed by stereomicroscopy. Microleakage analyses were done, using scores from 0 to 4, considering leakage on the incisal wall (enamel) and the cervical wall (dentin). Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (alpha = 0.05). Results: The results showed that sodium perborate and carbamide peroxide gel significantly increase the microleakage in Class V resin composite restorations to dentin but not to enamel margins. Conclusion: The risk of microleakage in dentin margins is increased soon after bleaching treatment.32541341

Clinical evaluation of glass-ionomer/resin-based hybrid materials used as pit and fissure sealants

Objective: The objective of the present study was to clinically evaluate the hybrid materials Vitremer and Dyract when used as pit and fissure sealants. Method and materials: The materials were applied in pairs on the mandibular permanent first molars of 100 children. 7 to 8 years old. Results: After 12 months of sealing, the clinical evaluation presented rates of 95.9% and 85.7% of complete retention for Dyract and Vitremer, respectively, indicating a statistically significant difference. The hybrid materials presented a statistically significant protective effect against caries compared with the control group at 6 and 12 months. Conclusion: The hybrid materials were able to control occlusal caries.32646346

Influence of cross-head speed on resin-dentin shear bond strength

Objective: To evaluate the influence of different cross-head speeds on shear bond strength test on the dentin surface. Methods: One hundred and twenty extracted bovine incisors were embedded in polystyrene resin. The specimens were prepared by wet grinding with 320-, 400- and 600-grit Al2O3 paper exposing dentin. After the application of the adhesive system Single Bond (3M) to etched dentin, the composite resin Z-100 (3M) was applied and light cured. The specimens were randomly assigned to four groups (n = 30). The shear bond strength tests were performed with an EMIC DL 500 universal testing machine at four different cross-head speeds: 0.50 (A); 0.75 (B); 1.00 (C); and 5.00 mm/min (D). Results: The mean values of shear bond strength in MPa (SD) were: A, 11.78 (3.91); B, 11.82 (4.78); C, 16.32 (6.45); D, 15.46 (5.94). The data were analyzed with one-way ANOVA and Tukey's test (alpha = 0.05). The results indicated that A = B = 0.05) indicated that there were no significant differences among A, B and C; A and B differed from D, and there was no significant difference between C and D. Significance: Different cross-head speeds may influence the shear bond strength and the fracture pattern in dentin substrate. Shear bond strength using cross-head speeds of 0.50 and 0.75 mm/min should be preferred. (C) 2001 Academy of Dental Materials. published by Elsevier Science Ltd. All rights reserved.17216516