Effect of premolar extraction on mandibular third molar impaction in young adults

OBJECTIVE: To test the null hypothesis that orthodontic therapy with or without premolar extraction does not result in any difference in third molar impaction. MATERIALS AND METHODS: Two groups were formed: 22 patients in one group with first premolar extractions and 22 patients in the other group without extractions. All patients were nongrowing subjects who had normal gonial angles and were skeletal Class I at the beginning of treatment. The available space for third molars, inclination of second and third molars, and angle between the second and third molars were evaluated. Also, the correlation of measured parameters and type of orthodontic therapy with the eruption of third molars was evaluated. RESULTS: Of the third molars, 81.8% were impacted in the nonextraction group and 63.6% were impacted in the extraction group. Impaction of mandibular third molars was significantly correlated to the pretreatment and posttreatment inclination of third molars and the angle between the second and third molars. In the extraction therapy group, the retromolar distance increased significantly with a mean of 1.30 ± 1.25 mm. CONCLUSIONS: When the inclination of the third molar is inconvenient, the tooth may remain impacted even if there is enough retromolar space.