Surface microstructure of composite resins after toothbrush-dentifrice abrasion.

In vitro, conventional, microfilled and experimental composite resin specimens were subjected to toothbrush-dentifrice abrasion. Subsequently, height loss was recorded, and the appearance of the abraded surfaces was studied by light and scanning electron microscopy. In the experimental composite, which had a polymer-impregnated porous glass filler, the glass phase showed flat surfaces. These surfaces were more smooth and lustrous than the surrounding resin. They also showed a rounding-off in the periphery. In the experimental composite smoothness and luster were therefore favored by the presence of large continuous areas of glass in the surface. It was possible to demonstrate the extension of the flat glass areas by the use of optical microscopy. In the conventional composite partly exposed irregular or rounded glass particles were frequent. A microfilled composite showed, except for frequent pores, a relatively smooth and lustrous surface. The wear rate of this material was, however, comparatively high.