Tissue changes in the rat molar periodontium following alteration of normal occlusal forces

Abstract

Periodontal tissue changes as a result of experimental alteration in normal antagonistic contact have been studied in maxillary molars of 85 young male rats. In 55 rats (series I) the length of the experimental periods varied. In early phases (1–3 days) the apical and interradicular regions had the characteristics of decreased pressure: widening of the periodontal space and increased bone information. Later the interradicular and apical regions showed the characteristics of pressure zones, i.e. narrowing of the periodontal space, cell-free areas followed by bone and root resorption. Normal periodontal conditions were gradually re-established within 1–2 weeks. In the remaining 30 rats (series II) the experimental period was limited to 7 days, but different kinds of appliance were used. In some of the subgroups the lower left molars were removed, and these animals had increased bone formation but no sign of cell-free zones or active bone and root resorption on the upper left side. Appliances which did not comprise molars as in series I, caused bone and root resorption, and combined with removal of lower left molars cell-free zones occurred on the right side. Removal of the lower left molars only, caused bone resorption on the right side.