Root resorption caused by mechanical injury of the periodontal soft tissues in rats

The purpose of the present investigation was to study, histologically, the effect on the root surface of mechanical injury to the periodontal soft tissues in rats. The animals were subjected to mechanical injury with a flat, needle‐like instrument only in the gingiva and the cervical periodontal ligament of the first maxillary molar. Odontoclastic root resorption occurred in part of the root surface at the alveolar crest level at 1 day. It extended gradually in the coronal direction over the following days, reaching part of the root surface at the cementoenamel junction at 14 d, and undermining part of the dentin below the enamel just above the cementoenamel junction at 21 d. The result of the present study indicated that mechanical injuries of human gingival soft tissues being sustained accidentally or during dental treatments might cause odontoclastic resorption of the root surface.