Mandibular growth and third molar impaction in extraction cases.

The position of mandibular third molars was studied in 60 patients from the pedodontic and orthodontic departments at the Federal University of Rio de Janeiro. All individuals received orthodontic treatment with an edgewise appliance following the extraction of first premolars. Examination of superimposed pretreatment and posttreatment cephalometric radiographs led to the observation that mandibular growth is directly related to the positioning of mandibular third molars. Third molar impactions were more likely to occur in cases with a predominance of vertical growth. The larger ascending ramus, the diminution in total length of the mandible and the larger mesial inclination of the crowns also seem to be indicative of third molar impaction.