Alveolar ridge changes in patients congenitally missing mandibular second premolars.

This study investigated changes in ridge width over time in patients who were congenitally missing mandibular second premolars. Data were obtained from stone casts and radiographs of 35 edentulous sites on 22 patients representing three time periods: (1) before extraction of the primary mandibular second molar, (2) completion of orthodontic treatment, and (3) long-term evaluation. The findings indicate that ridge width decreases 25% within 3 years after primary molar extraction. The rate of decrease diminishes to 4% over the next 3 years. The change in ridge width had a weak association with the age of the patient at the time of the extraction but a small predictive value. No correlation was found between changes in ridge width and height and the time since the extraction or the age of the patient at the time of extraction.