The correlation between time of polishing composite resins and the long term effect with regard to surface smoothness

Abstract

Composite resins are, along with amalgam, the most widely used filling material in today’s dental practice. Increased hardness of a material increases the resistance to abrasion; it is the filler particles in the composite that are the sole contributors to this property. Several reports in the literature have discussed the problem of polishing composite resin to a smooth surface. Several pastes and rubber wheels have appeared on the market to polish composite resin. The objective of this study was to investigate these polishing materials. It was also hypothesized that perhaps composites, like amalgams, should be polished after 24 hours. For that purpose, 14 patients were divided into two groups. In group A, composite restorations were polished immediately after insertion and polymerization; in group B, the restorations were polished 24 hours post insertion. By means of a hard replica technique, the restorations were replicated in vivo. Replicas were made immediately after polishing, 24 and 72 hours, 1, 3, 6 and 200 weeks post insertion. The replicas were observed in a scanning electron microscope. The results indicate that there is no difference in surface integrity which depends on time of polishing over a 6 week period. Loss of resin matrix was observed however, exposing more of the body of the filler. Some particles disappeared from the surface; this was especially evident after 20 weeks. Surface smoothness per se was not achieved utilizing either polishing material. From this study it can be concluded that loss of resin matrix is a slow, continuous process; over a period of 30-40 weeks it can be estimated that a turnover of surface filler particles takes place, exposing deeper situated filler particles.