Microleakage of compomer class V restorations: effect of load cycling, thermal cycling, and cavity shape differences

Microleakage is an important problem with direct filling restorations and an understanding of the factors that contribute to it is of critical importance.

This study investigated the effect of thermal and occlusal load cycling, and limited cavity preparation on microleakage of compomer Class V restorations in vitro.

Class V cavities were randomly prepared on the buccal and lingual surfaces of 32 recently extracted molars and premolars and restored with Dyract compomer restorative system as per the manufacturer's directions. Teeth were randomly assigned to 1 of 4 treatment groups with 8 teeth in each group: (I) thermocycling only; (II) load cycling only; (III) both thermocycling and load cycling; and (IV) no treatment. All teeth were then immersed in 2% basic fuchsin solution for 24 hours. Dye penetration was measured linearly using color photographic prints. ANOVA, comparisons between means, and correlation were used to analyze the results.

Thermocycling and cavity preparation had a significant effect on microleakage, but load cycling did not. Occlusal margins leaked more than the gingival margins.

Class V restorations demonstrated increased microleakage under the conditions of thermal cycling and nonretentive cavity design. More microleakage occurred at occlusal margins than at gingival margins. The effect of load cycling is complicated by considerations of the types of stresses applied and the restorative material response to such stresses.