The effects of local trauma to the enamel-related periodontal tissues in the eruption of the rat incisor

The periodontal tissues related to enamel (PTE) of the rat incisor comprise a connective tissue derived from the dental follicle and the enamel organ with its successive stages of development. Localized damage to these tissue s in rat lower incisors was done surgically in three ways: with an endodont ic file introduced into the labial periodontal space through either (i) its basal or (ii) its incisal extremities, or (iii) by the partial removal of the mandibular lower border, at the level of the molar teeth, together with the introduction of an endodontic file into the incisal part of that space . The lesions in the molar region of the PTE produced first a variable peri od of retarded eruption, and, depending upon their extent or degree were fo llowed by a cessation of the eruptive movement and, in the majority of the operated teeth, a recovery of the normal eruption rate before the end of th e experiment (17 weeks after surgery), Access to the PTE through the basal portion of the socket was erratic, but when the tissues were damaged produc ed similar effects.. Effects on eruption of lesions produced through the al veolar crest were minimal or even absent. Localized injury to the periodont al ligament of either lower or upper incisors did not produce similar effec ts on tooth eruption. The dental follicle and the enamel organ of teeth of limited growth when their crown is completed are similar to the PTE in the molar region of continuously growing rodent incisors. In teeth of limited g rowth these tissues play an essential part in the intraosseous stage of eru ption. The results here suggest that the PTE may also have a role in the su praosseous stage of eruption, which is continuous in teeth such as rat inci sors due to the presence of a continuously functioning odontogenic organ. ( C) 2000 Elsevier Science Ltd. All rights reserved.