Collagen turnover in the periodontal ligament under normal and altered functional forces. II. Adult rat molars.

Abstract

48 six month old rats were given 1 μCi/g of body weight of tritiated proline by intraperitoneal injection, 24 of them having had the left maxillary molars extracted two weeks earlier; 4 animals from each group were killed after a further 12 hours, 1, 4, 7, 12 or 20 days. Analyses of autoradiographic grain densities in various areas of the lower first molar periodontal ligament allowed calculation of half‐lives which were attributable to collagen turnover; all such values were less than 12 days.It is argued that the results are applicable to man in relative terms and thus have several important clinical implications. It becomes entirely feasible that the tissue destruction in chronic periodontitis is, at least in part, a function of decreased collagen formation brought about by any inflammatory process. The normal relatively slow rate of turnover in crestal fibres may well provide a barrier to the spread of inflammation from the gingiva, but its increase consequent on incresed tooth movement, as occurs in active orthodontic treatement, may reduce the barrier's effectiveness. However, the turnover rate is such taht even in adults it should not be a limiting factor in orthodontic treatement or in periodontal treatment aimed at restorring attachement.