Lower third molar development subsequent to second molar extraction.

Development and eruption of lower third molars was examined in 63 subjects who were treated by extraction of second molars. Changes in mesiodistal and buccolingual lower third molar angulation were measured on 60 degrees cephalograms taken before extraction and 3 or more years later. The final position of lower third molars was assessed on models at the end of the observation period by using a scoring system. All lower third molars erupted in periods ranging from 3 to 10 years after extraction. Ninety-nine percent of the third molars upright mesiodistally, but few became as upright as the second molars they replaced. Model analysis showed that 96% of the lower third molars erupted in good or acceptable positions.