Comparative evaluation of microleakage of metallic copings luted with three different commercially available luting cements: An in vitro study.

Aim: To evaluate the microleakage of metallic copings luted with three different commercially available luting cements. Setting and Design: Comparative evaluation in vitro study. Materials and Methods: Thirty replicas of abutment analog were milled and divided into 3 groups. Nickel chromium copings were fabricated; marginal gap was evaluated with optical microscope and luted with Zinc Oxide Non Eugenol cement, Zinc Polycarboxylate cement and Zinc Phosphate cement. After Thermocycling, cemented specimens were placed into 0.5% aqueous solution of basic fuchsin solution for 24 hours for dye penetration. Copings were longitudinally sectioned and microleakage scores were evaluated. Statistical Analysis Used: Kruskal-Wallis analysis of variance (ANOVA) followed by Chi-Square test. Pairwise comparison of groups with Mann Whitney U test. Result: Mean microleakage score was least for Zinc Phosphate cement (1.075 ± 0.85) followed by Zinc Polycarboxylate cement (1.80± 0.23) and most for Zinc Oxide Non Eugenol (2.1± 0.37). The results of the study were statistically significant, P < 0.05. Conclusions: Within the limitations of the study, it was found that all cements exhibited certain amount of microleakage. Zinc Phosphate cement exhibited a mean microleakage score that was significantly lower than Zinc Oxide Non Eugenol cement and Zinc Polycarboxylate cement. When microleakage scores of Zinc Oxide Non Eugenol cement and Zinc Polycarboxylate cement were compared, the difference was found to be insignificant indicating that microleakage in these cements is similar.

Effect of proanthocyanidin and riboflavin on shear bond strength of a nanocomposite to deep dentin - An in vitro Study.

Aims: The objective of this study was to evaluate the effect of two collagen crosslinking agents on shear bond strength of a nanocomposite using total-etch adhesive to deep dentin. Materials and Methods: Thirty maxillary central incisors were selected for the study and each tooth was divided into two equal halves with diamond disc (n = 60). Proximal surfaces were prepared to expose the deep dentin until the remaining dentin thickness was approximately 1 mm. The specimens were divided into three groups based upon the biomodification of dentin with collagen crosslinking agents. In Group I (n = 20), no collagen crosslinking agent was used before bonding system. In Group II, deep dentin biomodification was done with 6.5% proanthocyanidin (PA). In Group III, deep dentin biomodification was done with Riboflavin. Shear bond strength was evaluated using universal testing machine. Statistical Analysis Used: One-way analysis (ANNOVA). Pairwise comparison of groups was done with post hoc test. Results: Biomodification of deep dentin with PA showed the highest shear bond strength followed by riboflavin and control group. Conclusion: Biomodification of dentin surface with collagen cross-linking agents results in improvement of bond strength of total-etch adhesive to deep dentin.