Press-on force during polishing of resin composite restorations

摘要

Objective. To measure the press-on force during the polishing of composite restorations carried out by 10 dentists in a clinically simulated procedure.Methods. Composite restorations (Tetric EvoCeram Bulk Fill) were placed in standardized Class II two-surface cavities in first upper acrylic molars. The surfaces were roughened by sandblasting (50 mu m, 1 bar). The tooth was mounted on a tailor-made device with a 3D force sensor (Kistler, Z21134-300, 10H z). Ten dentists (7 male, 3 female) polished one Class II restoration each using the one-step polishing system OptraPol together with a dental handpiece and water spray. The dentists were allowed to use all shapes of the polishing system (small flame, large flame, cup, lens). During polishing, the press-on forces measured for up to 2 minutes. Simultaneously, the polishing procedure was recorded with a digital camera to correlate the forces with the polishing shapes and movements.Results. In total, 17,999 force measurements were available for analysis. The mean forces of all operators varied between 0.77(+/- 0.63) N and 2.23(+/- 1.48) N; the difference was statistically significant (ANOVA, post-hoc Tukey B, p 0.05). All dentists exerted maximum forces higher than 3 N (between 3.3 N and 18.3 N). Force values exceeded 2 N during 25% of the polishing time. Female dentists polished with a statistically significant lower force than male dentists (ANOVA, p 0.001). Polishing with the large flame and the cup generated significantly higher forces than polishing with the small flame and the lens (ANOVA, post hoc Tukey B, p 0.01).Conclusions. The press-on forces applied during polishing varied significantly between dentists and within the same dentist. In about 25% of the polishing time, forces were above the 2 N limit, which is recommended by some manufacturers as the maximum polishing force. Test institutes and manufacturers should evaluate the polishing performance of polishing instruments with various press-on forces. (C) 2019 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.