Using three-dimensional digital models to establish alveolar morphotype

Background: The aim of the study was to propose a classification of alveolar morphotype and assess a relationship between extraction/non-extraction orthodontic treatment and changes to the alveolar process. Materials and methods: Seventy-five subjects (mean age = 23.2, SD = 5.1) were selected. Areas of the sections of the alveolar process (ASAP) at three different levels (0, 2, and 4 mm) were measured on pre- and post-treatment three-dimensional digital models. Method reliability was analysed using Dahlberg's formula, intraclass correlation coefficient, and paired t-tests. Results: The mean ASAP was smallest at level 0 and largest at level 4. Pre-treatment ASAP < 773 mm(2), < 863.9 mm(2), and < 881.1 mm(2) at levels 0, 2, and 4 mm, respectively, should be described as a "thin" alveolar morphotype. Regression models showed that pre-treatment ASAP was a predictor of the change of the alveolus during treatment only at level 2. Conclusions: Patients for whom pre-treatment ASAP is < 773 mm(2), < 863.9 mm(2), and < 881.1 mm(2) at levels 0, 2, and 4 mm, respectively, should be described as having a "thin" alveolar morphotype. In these patients, extraction treatment, associated with a decrease in the alveolus area, should be exercised with caution.