Histologic reactions in gingival and alveolar tissues during tooth movement in rabbits.

Abstract

In this (semi)quantitative animal study the reaction of the gingival tissues to experimental tooth movement is described and compared to the reaction in the periodontal ligament. To this end, rabbit first incisors were moved sideways with helical torsion springs for periods varying from 3–72 hours. The initial force of the springs was 50 gf. Comparison with control animals and animals wearing passive springs showed that tooth movement itself leads to trauma in the dentogingival area within only a few hours. This trauma is characterized by tears and ulcerations in the epithelium, by tears and ruptures in the fibres, by leukocytic infiltration and by the presence of extravascular erythrocytes. Between the incisors, however, a firm connective tissue septum, acting as a reinforcement to the dentogingival area, remains intact. Tissue damage significantly increases with time. After 72 hours of orthodontic force, however, the interdental papilla seems to have recovered to some extent. The histologic data of the dentogingival area in animals wearing active springs, were compared to those of the underlying periodontal ligament by multivariate analysis of variance. This analysis showed, that there are significant differences between the tissue reaction in the labial and palatal segments, and between the dentogingival and dentoalveolar areas. Furthermore, a close relationship was found between the damage to the fibres and the occurrence of extravascular erythrocytes and leukocytes. It was therefore concluded, that local tissue damage, characterized by rupture of fibres, leads to an inflammatory reaction in the gingiva and the periodontal ligament.