The response of the pulp to the composite resin (Clearfil F) was histopathologically investigated in 23 germ-free rats. The upper first molar pulp was exposed with a #1/2 round bur through the mesial surface of the tooth and the cavity was arranged with a #33 1/2 inverted cone bur, and the composite resin was applied to the surface of the exposed pulp. The observation period was 2, 4, 7, 10 and 14 days postoperatively.
The results indicated that the pulpal response to the composite resin was characterized by the initial weak inflammatory cell infiltration at 2, 4 and 7 days, followed by the reduced responses with evidence of newly formed calcified tissues at 10 and 14 days. However, moderate to severe circulatory disturbance was observed throughout the experimental period. From these findings, the composite resin proved to have an irritating potential on the rat molar pulp.
The germ-free rats could be used as an excellent model to investigate the exposed pulp responses to the composite resin.
