Microscopic observations of the wear of a tooth restorative composite in vivo.

The wear of a composite restorative material in the oral cavity was followed by examining impressions by scanning electron microscopy. It was demonstrated that filler particles protrude from the polymeric matrix and, eventually, are lost leaving holes in the surface. A measure of the rate of wear was obtained by following the recession of the matrix on the faces of a large prominent particle. For a restoration that had been in place for 7 years, the average rate of wear over a further period of several months was estimated to be about 0.1 microns/day. For comparison, the gross wear of 2 mm over the entire 7-year period gives a greater average rate of wear of 0.8 microns/day.