Evaluation of Buccal Shelf Bone Dimensions and Bone Density in Adolescents and Adults With Different Mandibular...

The mandibular buccal shelf is an important extra-alveolar skeletal anchorage site, but its morphology may vary according to age, skeletal growth pattern, root location, and measurement level. This study evaluated buccal shelf bone thickness, vertical bone height, and bone density in orthodontic patients with different age groups and skeletal growth patterns.

This retrospective cross-sectional study evaluated cone-beam computed tomography (CBCT) records of 60 skeletal Class I orthodontic patients evaluated between January 2018 and December 2020. Participants were equally distributed among adolescent average, adolescent horizontal, adult average, and adult horizontal growth-pattern groups (n = 15 each) based on mandibular plane angle. Buccal shelf measurements were obtained at the mesial and distal roots of the mandibular first and second molars. Bone thickness was assessed at 6 and 11 mm, vertical bone height at 3, 5, and 7 mm, and bone density at 6 and 11 mm from the cementoenamel junction. Mixed-model analysis of variance followed by Bonferroni-adjusted pairwise comparisons was performed.

Buccal shelf thickness was significantly greater in horizontal than in average growers (mean difference: 1.26 mm; p < 0.001) and in adults than in adolescents (mean difference: 0.32 mm; p < 0.001). Thickness also increased significantly at the 11-mm level and toward the distal root locations. In contrast, vertical bone height was greater on average than in horizontal growers (mean difference: 0.68 mm; p < 0.001) and in adults than in adolescents (mean difference: 0.45 mm; p < 0.001). The age × measurement-level interaction was significant for vertical height (p = 0.015), with a greater adult-adolescent difference at 7 mm than at 3 mm. Bone density showed a significant age × growth-pattern interaction (p = 0.012). The cumulative density was 665 ± 45 Hounsfield units (HU) in adult average growers and 620 ± 40 HU in adult horizontal growers, compared with 568 ± 35 HU and 533 ± 38 HU in adolescent average growers and horizontal growers, respectively.

Mandibular buccal shelf morphology varied significantly with age, skeletal growth pattern, root location, and measurement level. Horizontal growers exhibited greater buccal shelf thickness but lower vertical height, while adults generally demonstrated greater bone dimensions and density. These findings support individualized CBCT assessment when selecting and positioning extra-alveolar skeletal anchorage.