MANDIBULAR INCISORS ALVEOLAR BONE, AND SYMPHYSIS AFTER ORTHODONTIC TREATMENT - A RETROSPECTIVE STUDY

The mandible of a deceased 19-year-old young woman who had been treate d with an edgewise appliance was removed during autopsy. The overall t ooth movements during the 19 months of treatment were reconstructed (t reatment documents) and compared with the macroscopic, radiologic, and micromorphologic findings of the incisor/alveolar bone/symphysis comp lex of the dry mandible. The initial lateral cephalogram revealed an e xtremely narrow and high symphysis, with an incisor position straight above the thin bone. During treatment, the incisors had been moved to lingual (lingual root torque) and derotated. Morphologic evaluation of the dry mandible revealed lingual (oral) aspects of the roots reachin g some millimeters out of the lingual alveolar bone and largely withou t cortical plate covering, Lateral dental contact radiographs of any b one/incisor segment showed the sagittal alveolar bone width to be smal ler than the labiolingual (orobuccal) diameter of the incisor roots. A comparison of the approximate pretherapeutic alveolar bone height, wh ich was assessed by measuring the distance from the cementoenamel junc tion to the most coronal margin of any root resorption in scanning ele ctron microscopy, with that of the specimen showed a calculated bone l oss on the lingual aspect extending from 2.3 to 6.9 mm. On the labial (buccal) aspect, bone loss was far less pronounced. These results sugg est that in the case of a narrow and high symphysis, pronounced sagitt al incisor movements and derotation during routine orthodontic treatme nt with a fixed appliance may be critical and lead to progressive bone loss of lingual and labial cortical plates.