Study on microleakage and gap observation of composite resin restoration

The degree of marginal leakage in the cervical cavity restored with Clearfil Bond System F was determined using an autoradiographic technique with 45Ca isotope solution. The isotope used was 0.1 mci/ml of solution in the form of calcium chloride with pH adjusted to 7.0. In addition, the gaps between tooth and restoration were examined by SEM on replicated specimens to evaluate the degree of adaptability. 1. Although there was some degree of difference concerning the leakage between restorative methods, it was found that the leakage in the gingival margin was greater than that of occlusal margin. 2. It was found that the leakage was effectively reduced by etching on the occlusal enamel wall but no effect was observed on the gingival margin. 3. Total etching of the cavity surface was extremely effective in decreasing microleakage of the cavity. Statistically, there was a highly significant difference between the group totally etched and the groups partially etched or not etched at all. 4. The group restored without etching showed a greater increase in leakage after thermal stress was applied. 5. SEM observation suggested that the total etching was significantly effective in improving the bond between tooth surface and restorative materials. 6. The degree of gaps of each portion of the cavity increased in the following order: gingival cementum wall, cavity floor, and gingival dentine wall. No gaps, however, were observed on the occlusal wall. 7. The gaps observed on the cavity floor gradually increased from the occlusal wall to the gingival wall, and the maximum gap was usually observed near the pulpo-gingival line angle. These results indicate that total etching is far more effective in reducing the microleakage.