Objectives:Microleakage is the most important factor responsible for the destruction of restoration margins. The aim of this study was to assess the effect of mechanical load cycling on microleakage of four types of glass ionomer cement (GIC) in comparison with a flowable composite resin.Materials and Methods:In this in-vitro experimental study, 100 Class V cavities were prepared on the buccal and lingual surfaces of 50 intact premolars. The prepared cavities were divided into five groups of (A) Z350, (B) Equia Forte, (C) encapsulated Fuji II LC, (D) hand-mixed Fuji II LC, and (E) Ketac Molar. All the samples were thermocycled (×2,000, 5–55°C), and half of the samples in each group were load cycled. All the teeth were then immersed in 0.5% basic fuchsine for 24 hours, sectioned, and observed under a stereomicroscope. Data were analyzed with Kruskal-Wallis and Mann-Whitney-U tests. Comparison between the incisal and gingival microleakage was made with Wilcoxon test. P<0.05 was considered statistically significant.Results:Load cycling and type of restorative material had a significant effect on microleakage. Gingival microleakage was significantly higher than occlusal microleakage with Equia Forte, encapsulated Fuji II LC, hand-mixed Fuji II LC, and Ketac Molar in the absence of loading, and with Z350 after loading.Conclusion:The sealing ability of Z350 under load cycling was better than that of Equia Forte, hand-mixed Fuji II LC, and Ketac Molar. The marginal integrity of encapsulated Fuji II LC was not significantly different than that of Z350.

Objectives:To evaluate comparatively the effect of quercetin on postbleaching shear bond strength (SBS) and adhesive remnant index (ARI).Materials and Methods:Intact maxillary premolars were divided randomly into 12 groups of 10 each: (1) bonding the bracket immediately after bleaching, (2) bonding 1 week after bleaching, (3–8) application of three experimental concentrations of quercetin (0.1%, 0.5%, and 1%) at two time durations (5 and 10 min), (9–10) application of the solvent of quercetin at two time periods (5 and 10 min), (11) application of 10% sodium ascorbate for 10 min, and (12) bonding the brackets on nonbleached teeth. Bleaching was performed using 15% carbamide peroxide gel for 5 days (6 h daily). After incubation and thermocycling, the SBS of brackets was measured. The ARI too was recorded at ×20. The data were analyzed statistically (α =0.05).Results:Bleaching reduced the SBS below 10 Megapascal (MPa) level (P < 0.05) while all the postbleaching treatments (except the application of the solvent of quercetin) recovered the SBS back to values greater than 10 MPa (P < 0.05) and also back to nonbleached SBS levels (P > 0.01). All eight postbleaching treatments had rather similar efficacies (P = 0.1396). The concentration of quercetin (beta = 0.259, P = 0.042) but not its duration (beta = 0.213, P = 0.093) significantly improved its efficacy.Conclusion:Bleaching can weaken the bond strength of orthodontic brackets below acceptable levels. The application of quercetin or Vitamin C or delaying the bracket bonding improved the postbleaching SBS.

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Background and Aim: This study aimed to assess the effect of finishing and polishing time, technique and surface coating on microleakage of encapsulated restorative resin modified glass ionomer (RMGI). Materials and Methods: In this in vitro study, 40 freshly extracted human premolars were selected. Two standard class V cavities were prepared on the buccal and lingual surfaces of each tooth. The prepared teeth were randomly assigned to eight experimental groups (n=10) according to the finishing and polishing time, technique and surface coating. The samples were blindly examined for marginal microleakage using a stereomicroscope at x40 magnification. The Mann-Whitney U test was used to analyze the obtained data with the level of significance set at P<0.05. Results: Groups with surface coating showed significantly lower microleakage than uncoated samples (P<0.001). The groups in which discs were used had lower microleakage (P<0.001). There were no statistically significant differences between the groups with delayed or immediate finishing and polishing (P>0.05). Our results showed that there were no statistically significant differences between enamel and dentinal walls with regard to marginal microleakage scores (P>0.05). Conclusion: Immediate finishing and polishing of coated restorations with Sof-Lex discs decreases their marginal microleakage. Also, it is more effective at the gingival margin.

Objectives: The durability of composite restorations is directly affected by the mechanical properties of the composite. The aim of this study was to evaluate the hardness and wear resistance of self-adhesive flowable composite (SAF) in comparison with conventional flowable composites. Materials and Methods: In this in vitro study, 50 composite specimens were prepared in brass molds with 10mm ×10mm ×2mm and divided into five groups (n=10). Specimens included three conventional flowable composites (Grandio flow, Filtek flow and Admira fusion flow), one self-adhering flowable composite (SAF, Vertise flow) and a microhybrid composite (filtek z250). After polishing, the micro-hardness of the specimens was measured in a Vickers hardness device, and the specimens were then subjected to 5000, 10000, 20000, 40000, 80000 and 120000 wear cycles in a wear tester. One-way ANOVA/Games-Howell, Kruskal Wallis, and Friedman tests were used for statistical analysis. The significance level was set at P<0.05. Results: The surface micro-hardness of the SAF was significantly lower than that of the microhybrid composite (P=0.01). There was no significant difference between the surface hardness of the different tested flowable composites (P>0.05). Also, the wear resistance of the studied composites was not significantly different in various cycles (P>0.05). Conclusion: Based on our results, SAF would not be an ideal substitute for conventional flowable composites in high-stress areas.