Microleakage and shear punch bond strength in class II primary molars cavities restored with low shrink silorane based versus methacrylate based composite using three different techniques.

Objectives: This in vitro study aimed to evaluate the gingival microleakage in class II cavities in primary molars restored with a low shrink silorane resin composite (Filtek P90) or a nanohybride composite resin (Filtek supreme XT) using three different techniques, (total bonding, closed or open sandwich techniques) lined by nano-filled resin modified glass ionomer cement RMGIC (Ketac N100). Additionally, the shear punch bond strength between the two types of composite and KNIO0 was also examined.

Study Design: For microleakage test, two standardized class II slot cavities were prepared in proximal surfaces of 60 sound extracted primary molars which were divided into 2 groups of 30 each according to the type of composite. Each group was subdivided into 3 groups (n = 10) according to the restorative technique used. The restored teeth were examined for microleakage after immersion in 2% methylene blue dye using stereomicroscope at 20 X. Microleakage scores among the groups were compared using Kruskal Wallis test followed by pair wise Mann Whitney U test at P < or = 0.05. Thirty disc specimens were prepared for determining the shear punch bond strength between the two composite materials and the KN100. Specimens were divided into 5 groups (n = 6) according to the adhesive protocol. The differences in mean bond strength values in MPa between groups were statistically analyzed using ANOVA followed by pair wise Tukey Post hoc test at P < or = 0. 05. Mode of failure was also evaluated for all groups.

Results: Both the silorane resin and nano-composite resin showed superior marginal seal with the total bonding technique compared to closed and open sandwich techniques. The recorded mean shear punch bond strength values showed no statistical significant difference between the two resin composites without or with their adhesive bonding systems when bonded to the nano-ionomer. All specimens showed cohesive mode of failures except for silorane resin with Adper Easy Bond Self Etch Adhesive (AEBSEA) which showed adhesive mode of failure.

Conclusions: The best marginal seal was obtained with the total bonding technique using both resin composites. The shear punch bond strength between KN100 and the two composite materials was not affected by either of the used adhesive bonding agent.