[Biological evaluation of new hydroxyapatite endodontic cement in vivo. Histopathological and clinico-pathological observation].

Histopathological observations of vital human and monkey dental pulp were performed to evaluate biologically a new root canal filling material APC containing hydroxyapatite. Experimental materials were divided into the following 3 groups. Group 1. Direct application to pulp wound (monkey teeth), 30 and 90 days. Group 2. Direct application to pulp wound (human teeth), 8-477 days. days. Group 3. Root canal filling on pulp stump (human teeth), 7-461 days. After extraction, the experimental teeth were fixed, demineralized, dehydrated and embedded in celloidin, they were prepared as thin sections and submitted to hematoxylin-eosin staining. Light microscopic observations were then made of them. After fixing, some specimens were embedded in resin and prepared in ultra thin sections before being triple stained with tannic acid-ethanol uranium-lead. They were submitted to observation under a HITACHI H-600 transmission electron microscope (TEM). Element analysis was performed on some unstained sections by means of energy dispersive X-ray analysis with a Kevex 7000A. Results 1. Application of APC to monkey dental pulp had no inhibiting effects on the healing progressed, the formation of regeneration hard tissue was observed. APC is believed to be biocompatible with dental pulp tissues. 2. Of the total of 50 cases in which APC was applied to human dental pulp, by the end of the experiment, 42 had occurred no symptoms of any kind. Broked down further, this means 23 (92%) of 25 cases in Group 2 and 19 (76%) of 25 cases in Group 3. Of the 25 cases in Group 2, 24 (96%) were evaluated as clinically good, none (0%) as fair, and 1 (4%) as unsatisfactory. Of the 25 cases in Group 3, 22 (88%) were evaluated as clinically good, 2 (8%) as fair, and 1 (4%) as unsatisfactory. Histopathologically, various pathological findings occurred in both groups of experimental materials. In the early stage, hyperemia, hemorrhage, round-cell infiltration, suppurative inflammation, and resorption of dentin in chamber walls were observed. By the thirtieth postoperative day, pulp cicatrization, formation of new hard tissue, and apposition of dentin on chamber walls were observed. TEM investigation of round-cell infiltration, observed in both group, revealed incursions of hydroxyapatite and bismuth in the macrophages. The tendency for hard tissue newly generated has began on 73 days in Group 2 and on 32 days in Group 3. This finding was made somewhat earlier in Group 2. Thereafter, dental pulp continued in a healthy condition.(ABSTRACT TRUNCATED AT 400 WORDS)