[Investigation of etching and bonding on the inner surface of free enamel. SEM observation and thermal cycling test for pigment invasion].

The purpose of this study is to examine adhesive condition on the inner surface of free enamel. If it was possible to use an adhesive composite resin to reinforce free enamel, it would be unnecessary to remove the free enamel entirely. To this study, we have used a visible light-cured and adhesive composite resin for the inner surface of free enamel. At the first, we carried out SEM examination of adhesive condition on the inner surface of free enamel. Then we performed thermal cycling test for pigment invasion. Results 1. SEM observation found tag-like extensions on the inner surface of free enamel. These extensions were of 2 shapes: horseshoe and beehive. 2. Thermal cycling test for pigment invasion showed practically no difference in marginal leakage between the experimental free-enamel cavities and control box cavities. 3. As a result of observation of adhesive conditions on the inner surface of free enamel, we believe that a certain degree of reinforcement of that enamel can be expected from composite resin.