Stig K. Osterberg

The effect of extraction and orthodontic treatment on dentoalveolar support

Full-mouth radiographs of ninety-six patients treated by extraction of four first premolars were taken at least 10 years postextraction. Three groups were established: one with extensive crowding in the full permanent dentition treated by extraction and fixed appliance therapy; one treated by serial extraction and fixed appliance therapy; and one treated by serial extraction only. Measurements of tooth length and alveolar bone height were made from the projected radiographs, and buccolingual socket areas were measured from direct tracings of the radiographs. Comparison between groups revealed reduced mean radiographic tooth lengths for incisors and mandibular molars in the orthodontically treated groups. The incidence of root resorption was similar for both treated groups. Reduced alveolar bone heights were noted in the extraction sites of the two orthodontically treated groups but not in the group treated by serial extraction only. Most reduction in long-term dentoalveolar support occurred as a result of root resorption except in the extraction sites, where it occurred largely as a result of bone loss. Root parallelism did not appear to influence proximal bone heights at the extraction site. In malocclusions involving arch length deficiency, maximally displaced canines had reduced long-term proximal bone compared to nondisplaced canines, supporting the concept of encouraging autonomous distal eruption through serial extraction.

Long-term effect of root proximity on periodontal health after orthodontic treatment

The present investigation was done to evaluate the incidence and distribution of root proximity after orthodontic treatment and to test the hypothesis that interproximal areas with thin interdental bone provide less resistance against marginal periodontal breakdown than areas with normal width of bone between the roots. Only adult patients were examined at least 16 years after active orthodontic treatment. The distance between the roots was measured directly on periapical radiographs. Gingival health, level of connective tissue attachment, and clinical scores for bone levels in sites with thin interdental bone and neighboring or contralateral sites with normal width of bone between the roots were compared. Among the 400 patients studied, 25 had unilateral or bilateral areas with root proximity. Root proximity was diagnosed between maxillary central and lateral incisors in 18 patients, between mandibular central and lateral incisors in two patients, and between maxillary lateral incisor and canine, maxillary first and second molars, mandibular canine and first premolar, mandibular first and second premolars, or mandibular first and second molars in only one patient. No statistically significant differences in inflammation, level of attachment, and bone level were observed between root proximity sites and control sites. The results indicate that anterior teeth are not predisposed to more rapid periodontal breakdown when roots are in close proximity. Too few molar sites were included to draw conclusions regarding such areas.