Ankylosis of teeth following thermal injury

Thermal injury to the periodontium via the root canal was produced in 12 squirrel monkeys in order to study the sequence of events leading to ankylosis. Three days and one week following such injury an area of necrosis was found in the periodontal ligament which was circumferential, involved both periodontal ligament and alveolar hone, extended approximately l/3 the length of the root and did not involve the epithelial attachment. Two and 3 weeks following thermal injury new fibroblasts and blood vessels were seen at the periphery of neerotic areas and progressively decreased the area of necrosis. This was accompanied by frontal resorption of bone and cementum. Rear resorption took place adjacent to areas where the periodontal ligament was still neerotic. By one month, healing had progressed so that neerotic tissue was no longer present, bone apposition was more prominant than resorption and in some areas tooth and bone had fused. Ankylosis persisted but a continuous remodeling process was taking place as evidenced by further resorption and bone formation until the end of the study (6 months).