CBCT evaluation of mandibular retromolar space in adult patients according to skeletal Class and facial biotype: A cross-sectional study.

OBJECTIVE

To evaluate mandibular retromolar bone availability across skeletal patterns using cone-beam computed tomography (CBCT), considering crown- and root-level trajectories.

METHODS

This retrospective cross-sectional study analysed 120 CBCT scans (18-60 years; mean age 29.8±9.8 years) obtained between 2022 and 2025 from an institutional database. From an initial pool of 465 scans, inclusion criteria comprised adults without third molars, alveolar bone loss, or craniofacial anomalies. Measurements were performed along two reference lines (cusp and sagittal) at four planes (0, 2, 4, and 6mm). Statistical analyses included Friedman, Kruskal-Wallis, and Chi-square tests (α=0.05).

RESULTS

Retromolar space decreased significantly from plane 0 to plane 6 in both reference lines, with consistently smaller and more variable values in the sagittal line (root level). Skeletal Class III patients exhibited the greatest mean space (6.9mm), followed by Class I (5.3mm) and Class II (3.8mm). No significant differences were observed among facial biotypes. Males presented significantly larger values than females across nearly all planes.

CONCLUSIONS

Mandibular retromolar space is more restricted at the root level and varies according to skeletal Class and sex. Class II patients present the most limited space and therefore require the most cautious distalization planning. CBCT assessment is essential to guide individualized biomechanics and minimize the risk of root-cortical contact or iatrogenic complications.