Evaluation of polymerization shrinkage of bulk-fill resin composites using microcomputed tomography.

OBJECTIVES: This study evaluated the influence of cavity depth on polymerization shrinkage of bulk-fill resin composites with and without adhesive resin. MATERIALS AND METHODS: Standardized box-shaped cavities (width, 4 mm; length, 5 mm, depth, 2 mm or 4 mm) were made on occlusal surfaces of extracted human third molars (N = 60). The teeth were assigned to 3 groups to receive bulk-fill resin composites (low-viscosity bulk-fill, SDR; high-viscosity bulk-fill; Filtek Bulk-Fill-FB; and TetricEvo Ceram Bulk-Fill-TB) in the prepared cavities with and without adhesive resin (Clearfil S3 Bond). Each specimen (n = 5 per group) was scanned twice using microcomputed tomography (micro-CT): once after application of the resin composite to the cavity prior to polymerisation and once after polymerisation. The shrinkage of volumetric loss (%) was measured using micro-CT. Data were analysed using Kruskal-Wallis and Mann-Whitney U tests (alpha = 0.05). RESULTS: The material type (p < 0.05), application of adhesive resin (p < 0.05) and cavity depth (p < 0.05) significantly affected the shrinkage values. The interaction terms were also significant (p < 0.05). All the bulk-fill resin composites tested showed significantly less shrinkage when applied in cavities with adhesive resin (0.94-2.55) compared with those without (2.01-3.45) (p < 0.05) and presented significantly more shrinkage after polymerisation (p < 0.05). At a 2-mm cavity depth without (2 mm, 2.28; 4 mm, 2.41) and with adhesive (2 mm, 0.94; 4 mm, 1.67), significantly less shrinkage was observed with FB compared with SDR and TB (p < 0.05). At a 4-mm cavity depth without (3.14) and with adhesive (2.55), SDR showed significantly higher shrinkage compared with FB and TB (p < 0.05). CONCLUSIONS: The bulk-fill composites tested presented less shrinkage when used in conjunction with adhesive resin application on dentin. Overall, the low-viscosity bulk-fill resin SDR showed more shrinkage compared with high-viscosity resins tested. CLINICAL RELEVANCE: Low- or high-viscosity bulk-fill resin composites should be applied on dentin after application of adhesive resin to decrease shrinkage.

Effect of Different Antioxidants on the Microtensile Bond Strength of an Adhesive System to Sodium Hypochlorite-treated Dentin.

PURPOSE: To evaluate the effects of different antioxidant treatments on the microtensile bond strength of an adhesive system to sodium hypochlorite (NaOCl)-treated dentin. MATERIALS AND METHODS: Thirty extracted third molars were sectioned 3 mm below the occlusal surface and divided into six groups according to the antioxidant treatment received: control group: distilled water; NaOCl group: 5.25% NaOCl and distilled water; proanthocyanidin (PA) group: 5.25% NaOCl, 5% PA and distilled water; 1-week storage group: 5.25% NaOCl and storage for 1 week in distilled water; Accel group: 5.25% NaOCl, Accel, and distilled water; noni group: 5.25% NaOCl, noni fruit juice, and distilled water. NaOCl, PA, Accel, noni, and distilled water were administered for 30 s, 10 min, 30 s, 10 min, and 30 s, respectively. A self-etching adhesive system (Single Bond Universal Adhesive) was applied to each specimen and a resin composite (Filtek Z550) was built up to a height of 5 mm on the dentin surface. Each specimen was serially sectioned to obtain sticks with a cross-sectional area of 1 mm2, and their microtensile bond strength was determined. Statistical differences between groups were analyzed using one-way ANOVA and Tamhane's T2 test. RESULTS: Microtensile bond strength in the NaOCl group was significantly lower than in all other groups. However, there were no significant differences in the bond strength between the groups treated with different antioxidants. CONCLUSIONS: NaOCl significantly reduced the microtensile bond strength of the adhesive system. The application of PA, Accel, and noni fruit juice to NaOCl-treated dentin significantly improved the microtensile bond strength.

Randomized controlled trial of the 2-year clinical performance of a silorane-based resin composite in class 1 posterior restorations.

PURPOSE: To compare the 2-year clinical performance of a silorane-based resin composite with that of an established nanoceramic resin composite for class 1 posterior restorations. METHODS: In this randomized controlled study, 100 class 1 molar cavities were prepared in 50 subjects. Each subject received a restoration with Filtek Silorane and Ceram.X Duo in different quadrants. The restorations were evaluated using the modified USPHS criteria at baseline and 6, 12, and 24 months. Parametric changes over the 2-year period were assessed with the Friedman test. The baseline and recall scores were compared by using the Wilcoxon signed-rank test (P < 0.05). RESULTS: No subject developed secondary caries or postoperative sensitivity. Further, the resin composites showed no significant differences in all the evaluated parameters over 2 years (P > 0.05). At 2 years, four Filtek Silorane and seven Ceram.X Duo restorations had Bravo scores for anatomic form, marginal adaptation, and surface texture (P < 0.05); however, these changes were mainly the effect of scoring shifts from Alfa to Bravo. Overall, both materials showed good clinical results with predominantly Alfa scores.