Dimensional changes of the alveolar ridge contour of the premolar extraction site in adolescents.

PURPOSE: Premolar extraction in orthodontic therapy is common in adolescent patients. Knowledge of the tissue reaction in an extraction site is mainly based on studies with animal and adults. Thus, we aim to describe the time-dependent dimensional changes of the alveolar ridge contour of the premolar extraction site in adolescents. METHODS: Clinical data were obtained from a randomized controlled clinical trial (Universal Trial Number U1111-1132-6655), comparing treatment modalities with orthodontic space closure was initiated after 2-4 weeks (group A) and >/= 12 weeks after tooth extraction (group B). Dental casts taken before the tooth extraction (T1) and before initiation of the space closure (T2) were digitalized with a 3D scanner and superimposed to analyze the dimensional changes of the alveolar ridge in early and later stage of wound healing. Linear mixed models were used for statistical analysis. RESULTS: Plaster models of 25 patients (mean age 15.2 years, 11 male and 14 female) with 66 extraction sites were enrolled. The average atrophic changes from tooth extraction to the early stage of wound healing (group A, n = 41) were in total 27.5% +/- 11.8; labially 31.3% +/- 15.1 and orally 23.6% +/- 13.4. In group B (n = 25) the average atrophic changes were in total 38.6% +/- 12.1; labially 46.2% +/- 16.7; orally 31.3% +/- 18.9. The atrophic changes between the groups in total (p = 0.031) and at the labial side (p = 0.012) were significant. The jaw affiliation was a significant parameter for all examined areas in regard to all cases (labial p = 0.019; oral p = 0.020; total p = 0.001). Atrophic changes between genders were not statistically different. CONCLUSIONS: Alveolar atrophy increased over time after extraction primarily in the lower jaw at the labial side. The main atrophy occurred in the first healing phase of the extraction socket. Thus, timely coordination is important to preserve sufficient bone levels. The atrophic changes of the alveolar ridge in adolescents parallel those reported for adults.