Abstract
The composite resin jacket crown (called the CR crown) for primary anterior teeth has shown excellent clinical prognosis as well as a favorable esthetic effect, is easy to handle and has good mechanical properties. Nevertheless, we occasionally encounter cases of severe attrition of the natural primary tooth structure from opposing the composite resin jacket crowns.
In this report, worn surfaces of exfoliated primary incisors from opposing composite resin jacket crowns and from opposing natural teeth were investigated comparatively with an optical stereo-microscope (×25) and a scanning electro-microscope(×1000), We observed then the artificial wear surface of the tooth structure using the regular type composite resin and micro filler type resin.
The findings were as follows: In comparison with the undulated surface contour of the naturally worn tooth structure, the surface of the tooth structure was very smooth and covered with a number of fine scratches in the tooth opposite the composite resin jacket crown. The widths of these scratches were about 3 to 7 cm. When comparing the artifical wear surfaces using the regular composite resin with those by using micro fillered composite resin, the latter showed a smaller amount of wear.
In conclusion, it is assumed that the excessive wear of primary anterior teeth by opposing composite resin jacket crowns would have been due to the nature of the filler contained in the composite resin.
