Marginal microleakage of resin-modified glass-ionomer and composite resin restorations: Effect of using etch-and-rinse and self-etch adhesives.

Objectives: Previous studies have shown that dental adhesives increase the bond strength of resin-modified glass-ionomer (RMGI) restorative materials to dentin. This in vitro study has evaluated the effect of etch-and-rinse and self-etch bonding systems v/s cavity conditioner, and in comparison to similar composite resin restorations on maintaining the marginal sealing of RMGI restorations. Materials and Methods: 98 rectangular cavities (2.5×3×1.5 mm) were prepared on buccal and palatal aspects of 49 human maxillary premolars, randomly divided into 7 groups (N=14). The cavities in groups 1, 2 and 3 were restored using a composite resin (APX). The cavities in groups 4, 5, 6 and 7 were restored using a resin-modified glass-ionomer (Fuji II LC). Before restoring, adhesive systems (Optibond FL = OFL, three-step etch-and-rinse; One Step Plus = OSP, two-step etch-and-rinse; Clearfil Protect Bond = CPB, two-step self-etch) were used as bonding agents in groups 1-6 as follow: OFL in groups 1 and 4, OSP in groups 2 and 5, and CPB in groups 3 and 6, respectively. The specimens in group 7 were restored with GC cavity conditioner and Fuji II LC. All the specimens were thermo-cycled for 1000 cycles. Microleakage scores were determined using dye penetration method. Statistical analyzes were carried out with Kruskal-Wallis and Mann-Whitney U tests (α=0.05). Results: There were significant differences in microleakage scores at both enamel and dentinal margins between the study groups (P<0.05). The lowest microleakage scores at enamel and dentin margins of RMGI restorations were observed in group 6. Conclusion: Use of two-step self-etch adhesive, prior to restoring cervical cavities with RMGIC, seems to be more efficacious than the conventional cavity conditioner in decreasing marginal microleakage.

Bond strength of composite-resin and resin-modified glass ionomer to bleached enamel: Delay bonding versus an antioxidant agent.

Objectives: As enamel bond strength of the resin-modified materials is reduced after bleaching, a delay bonding of at least 1 week is recommended. This study investigated the efficacy of 10% sodium ascorbate hydrogel on the bond strength of bleached enamel as an antioxidant agent. Materials and Methods: Ninety-six human, sound molars divided into eight groups. Buccal enamel surfaces of specimens in two negative control groups after preparation were bonded by the Z100 CR using the single-bond adhesive and Vitremer RmGI. Specimens in other groups after enamel preparation were bleached with 9.5% hydrogen peroxide. In two positive control groups, bonding of CR and RmGI was performed immediately after bleaching. Specimens in two other groups were immersed in distilled water after bleaching, and then CR and RmGI were bonded after 1 week. In last two groups, 10% sodium ascorbate hydrogel was applied after bleaching, and then they were bonded by CR and RmGI. The specimens were placed under shear force. Statistics: ANOVA and Duncan's multiple range tests were used for data analysis. Results: Application of 10% sodium ascorbate hydrogel immediately before bonding and delay bonding for 1 week eliminated the negative effects of bleaching on CR and RmGI enamel bond strength. Conclusion: Application of 10% sodium ascorbate hydrogel or 1 week period elapsed after bleaching could significantly increase the enamel bond strength to a normal value.