The association between orthodontic treatment and third molar position, inferior alveolar nerve involvement, and prediction of wisdom tooth eruption.

PURPOSE: The present study aims to compare mandibular third molar position in relation to the mandibular ramus, mandibular third molar angulation, potential impaction and nerve involvement in orthodontic treated versus untreated subjects.
METHODS: The sample consisted of 300 panoramic radiographs 119 males (mean age 16.9 years); 181 females (mean age 16.8 years), contrasting an orthodontically treated (n = 150) to an untreated group (n = 150). Only patients with a full mandibular dentition were included. Pell and Gregory (Dent Digest 39: 330-338, 1933), Winter (Principles of exodontia as applied to the impacted third molars, 1926) and Félez-Gutierrez modified by Gomes (Study of nerve lesion following mandibular third molar surgery, 2011) classifications were used. Radiological information was used to predict eruption. Data was analyzed using frequency analysis and Chi-square testing.
RESULTS: 220 lower wisdom teeth (73.3%) were impacted in the treated group, opposed to 236 impacted lower wisdom teeth (78.7%) in the untreated group. A close relation with the mandibular nerve was observed 125 times (41.7%) in the treated group, opposed to an incidence of 112 (37.3%) in the untreated group. The differences were not statistically significant. A partial eruption was predicted for 153 (51%) lower wisdom teeth in the treated group, opposed to 106 (35%) in the untreated group and an impossible eruption in 67 (22%) in the treated group, opposed to 130 (43%). These differences were statistically significant (p < 0.05).
CONCLUSIONS: The significant outcomes indicate that orthodontically treated patients may develop a higher likeliness to partially erupted third molars, which potentially leads to local clinical morbidities, such as pericoronitis and caries on adjacent teeth. In this context, it may support third molar extractions at an earlier stage in particular cases.