An enzyme histochemical study of the behavior of rat bone cells during experimental apical periodontitis.

Bone alkaline and tartrate-resistant acid phosphatase activities were studied in paraffin sections obtained from experimentally induced periapical lesions of rats. These enzyme activities were demonstrated despite the use of high temperatures during embedding. In the formation phase, numerous osteoblasts and periodontal ligament cells showed strong alkaline phosphatase activity. On the other hand, a number of osteoclasts and preosteoclasts showed tartrate-resistant acid phosphatase activity in the activated resorption sites of periapical lesions. It is suggested that enzyme histochemical applications to paraffin sections are a useful means for clarifying the behavior of bone cells and that bone remodeling has occurred in the periapical lesions.