Effect of occlusal load cycling on the marginal integrity of adhesive Class V restorations

The objective of this study was to evaluate the gingival wall marginal integrity of adhesive Class V restorations subjected to occlusal load cycling. Extracted lower first and second molar teeth were used. For each tooth, a Class V cavity was prepared in the buccal or lingual surface with the gingival margin in the cementum. The cavities were restored with eight different adhesive systems: (1) Ketac-Fil; (2) Fuji II LC; (3) Ketac-Bond/Pertac; (4) Photac-Bond/Pertac; (5) Scotchbond 2/P50; (6) Scotchbond Multi-Purpose/P50; (7) Clearfil Liner Bond/Clearfil Photo Posterior; and (8) OptiBond/Herculite XR. For each material-combination, three test procedures were carried out: no loading (control), loading at 125 N and at 250 N. Six specimens were prepared for each procedure. The samples were loaded for 5000 cycles in a dye solution and kept in the dye for 24 hours after loading. Control samples were stored in the dye for the same period. All teeth were sectioned and dye penetration at the gingival wall was scored from 0 to 4. Under control condition, only groups 2, 6, 7 and 8 showed perfect marginal integrity. After loading at 125 N, groups 1, 3 and 5 showed significant increase in leakage (P < 0.05). Increasing the load to 250 N resulted in significant deterioration in the marginal adaptation of all test groups, except 6 and 7. This study indicates that the marginal integrity of occlusally stressed adhesive Class V restorations can only be preserved by a few products.