Effect of Different Fiber Reinforcement Strategies on the Fracture Strength of Composite Resin Restored Endodontically Treated Premolars

Objective: To compare the effect of three different fiber reinforcement strategies on the fracture strength of composite resin restored endodontically treated premolars. Material and Methods: Seventy-two sound human premolars extracted for orthodontic reasons were divided into 6 groups (n=12) after endodontic treatment. Group 1: intact teeth (positive control); Group 2: endodontically treated teeth without restoration (negative control); Group 3: composite resin restoration; Group 4: placement of fibers at occlusal position; Group 5: splinting the buccal and palatal walls with horizontal fiber posts; Group 6: placement of fibers at the occlusal position after splinting the buccal and palatal walls with horizontal fiber posts. Then fracture strength was measured at a crosshead speed of 0.5 mm/min in a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests at α=0.05. Results: There were significant differences between the negative and positive control groups (p<0.001) and between the negative control group and all the other study groups (p<0.001). However, there were no statistically significant differences between the positive control group and all the experimental groups and between the experimental groups (p>0.05). Conclusion: Fiber insertion had no additional reinforcing effect on the fracture strength following composite resin restoration.

Comparison of the effect of hydrogel and solution forms of sodium ascorbate on orthodontic bracket-enamel shear bond strength immediately after bleaching: An in vitro study.

Aim: This study compared the effects of hydrogel and solution forms of sodium ascorbate (SA) with two different application times on bracket bond strength subsequent to bleaching. Materials and Methods: A total of 72 sound premolars were randomly divided into six groups (n = 12): An unbleached control group (group one) and five experimental groups of carbamide peroxide. Specimens in group two were bonded immediately after bleaching; specimens in groups three and four were bleached, then treated with SA solution for ten minutes and three hours, respectively, and then bonded. In groups five and six, SA hydrogel was used and the specimens were prepared similar to groups three and four, respectively. Following debonding, bond strengths were recorded in MPa. To evaluate the amount of resin left on the enamel surfaces, adhesive remnant index (ARI) scores were used. Statistical Analysis: The bond strength data were analyzed with ANOVA and pairwise comparisons were made by Tukey test. The ARI data were subjected to Kruskal-Wallis test and two-by-two comparisons were made by the Mann-Whitney U test. Results: There were significant differences in bond strengths between the groups ( P < 0.0005). However, the differences between groups three, four, five and six were not significant. Furthermore, there were no significant differences between group one and groups four and six, whereas the differences between the other groups were significant ( P < 0.05). Regarding ARI, there were significant differences among the groups ( P = 0.004). Conclusion: Bleaching significantly decreased the bracket bond strength. Compromised bonding was reversed with a three-hour application of both forms of SA.