A time-related study of periodontal healing and root resorption activity after replantation of mature permanent incisors in monkeys.

Periodontal and pulpal healing was registered histometrically at different observation periods after replantation of mature incisors in green Vervet monkeys. Maxillary central incisors and mandibular lateral incisors were extracted and then replanted after either 0- to 18 min. In the 18 min. group, the teeth were stored dry prior to replantation. The animals were sacrificed 1-, 2-, 4-, or 8 weeks after replantation. The mobility of the replanted teeth was determined and histological examination carried out. The following parameters were registered for each tooth: periodontal ligament healing, surface resorption, inflammatory resorption, replacement resorption (ankylosis) and the extent of vital pulp. Periodontal ligament healing, as assessed histologically or via mobility testing, was almost complete 2--4 weeks after replantation. Surface resorption was first recognized after 1 week and became prominent after 2 weeks; the frequency increased slightly after 4- and 8 weeks. Inflammatory resorption was first recognized after 1 week and showed a rapid extension with increasing observation periods. Replacement resorption was first noted afer 2 weeks, where the peak frequency occurred. The frequency decreased in both groups with increased observation periods. The 18 min. group showed significantly more replacement and inflammatory resorption than the immediate replantation group. Finally, an analysis of the systematic error of histometric registration of root resorption showed that the uneven distribution of root resorption upon the root surface could lead to significant errors in the registration of root resorption activity unless a proper sectioning plane was chosen and an adequate number of measuring locations along the root surface was used.