Cavosurface margin geometry in conventional and air abrasion Class V cavity preparations.

PURPOSE: To compare cavosurface angle and area of missing tooth structure at the cavosurface margin in cross-sections of Class V cavity preparations made with a conventional carbide bur and with an air abrasive cavity preparation system. MATERIALS AND METHODS: Class V cavity preparations were made with a #56 carbide bur or with a KCP 1000 air abrasive unit. They were restored and sectioned longitudinally, providing 43 margins for study. Cavo-surface angle and area of missing tooth structure were measured for each margin from digital images of the sections. The angle and area data was grouped according to margin location and cavity preparation system and analyzed for differences using the Kruskal-Wallis test. To determine if there was a relationship between the missing area and the angle at the cavosurface margin, Lomb periodograms were analyzed. RESULTS: Conventional cavity preparation margins had an average cavosurface angle less than 90 degrees while the air abrasion margin angle was greater than 90 degrees. Cavo-surface angles for conventional cavity preparations were significantly different from cavosurface angles for air abrasion cavity preparations. Missing areas at the cavosurface margin for conventional cavity preparations were not significantly different from missing areas at the cavosurface margin for air abrasion cavity preparations. Lomb periodograms showed no trend concerning the missing area as a function of the angle. CONCLUSIONS: There was no significant difference between the area of missing tooth structure at the cavosurface margin in conventional vs. air abrasion cavity preparation. Cavosurface angle in conventional preparations was less than 90 degrees, and greater than 90 degrees in air abrasion cavity preparations. Cavosurface angle and area of missing tooth structure at the cavosurface margin varied independently.