Abstract
In order to clarify the mechanism of traumatic tooth breakdown caused by probing into carious pits and fissures, a study was carried out on artificial carious fissures made from two pieces of bovine enamel. Twenty of the artificial fissures were divided into two groups, 15 experimental and 5 control ones. A bacterial mass cultured from human dental plaque was transferred into the experimental fissure and was incubated in MSB broth for 4 weeks at 37°C. Both experimental and control fissures were probed with a dental explorer at about 800g pressure and the adhesive force required to pull the explorer was measured with an electric weighing system which was described in our previous paper. Then vertical ground sections through the fissures were prepared and observed by light and polarizing microscopy and by microradiography. Four of the twenty fissures, 3 experimental fissures and one control fissure, were examined by scanning electron microscopy (SEM). The following results were obtained. 1) There was significant difference between mean adhesive forces in experimental fissures (50.7g) and in control fissures (7.8g). 2) Tooth breakdown was recognized in both experimental and control fissures. 3) There was histopathological caries with subsurface demineralization in all experimental fissures, but not in control fissures. 4) The subsurface demineralization was wide at the entrance of the experimental fissures and became narrow toward the bottom. 5) In the SEM study, there were no prominent features in the surface enamel of experimental fissures, but eroded enamel rods were observed in the subsurface demineralization.
