Alveolar Bone Height Preservation in Growing Patients After Decoronation, Extraction, or Retention of Ankylosed Primary Teeth: A Retrospective Cohort Study

Abstract

Introduction: Mandibular second premolars are frequently congenitally missing. Preservation of the alveolar ridge to facilitate future implant placement is critically important for favorable outcomes. Maintaining the retained primary tooth is desired unless the primary tooth becomes ankylosed during the growth period. This study examined three approaches to preserving alveolar bone height in growing patients when the retained primary tooth becomes ankylosed: decoronation, extraction, or retention of the tooth. We hypothesized that decoronation would show the greatest preservation of bone height, while retention would show the least. Methods: This retrospective cohort study used de-identified serial radiographs collected from practitioners in the greater Seattle-Tacoma area. Ankylosed primary mandibular second molars with congenitally missing mandibular second premolars were separated into three groups based on management method: decoronation, extraction, or retention. Alveolar bone height was measured at two time points and the change over time was calculated. Results: The mean age of each sample in years at T0 was 13.1, 13.6, and 12.6 for decoronation, extraction, and retention, respectively. The mean follow-up time in months for each sample was 22.9, 29.1, and 23.9 for decoronation, extraction, and retention, respectively. Decoronation of ankylosed mandibular primary second molars showed the most favorable change in alveolar bone height over time, with the bone height in the region either increasing or remaining stable. Retention showed the least favorable effect, with alveolar bone height decreasing as the patient matured. Extraction displayed an intermediate response. Conclusions: The alveolar ridge responds more positively during growth after decoronation in patients with ankylosed primary second molars. Growth may influence the extent of change observed in each group.