Comparison of microleakage of different margin types around Class V resin restorations in primary teeth.

This in vitro study compared the effect of a concave with a straight-bevelled cavity margin on the microleakage of Class V composite resin restorations in primary teeth. Standardised Class V cavity preparations were made in vitro on the buccal (all margins placed in enamel) and on the lingual (margins placed in enamel and cementum) surfaces of 20 sound primary molars. The teeth were randomly assigned to two groups of 10 each: in Group 1, a concave bevel was made with a high-speed No. 04 tungsten carbide bur and in Group 2, a straight bevel was made with a high-speed No. 556 tungsten carbide bur. The teeth were restored incrementally with Adper Single Bond 2 (3M) adhesive and Filtek Z 350 (3M) composite resin. All specimens were subsequently thermocycled and immersed in 50% silver nitrate solution. Microleakage of the restorations was then assessed by silver penetration. A grading scale of 0 to 4 was used as the scoring criterion. At the enamel margins no statistically significant differences were observed between the two groups (p>0.05). Occlusal walls in enamel, in both groups, exhibited less leakage than the cervical walls in cementum (p<0.01) and Group 1 showed better results than Group 2 in decreasing microleakage at the cementum margins (p <0.05). Based on the results, it was concluded that concave-beveled cavity preparations may reduce but did not totally eliminate microleakage at the cementum margins of Class V composite resin restorations in primary teeth.