Can CBCT-3D Condylar Morphology Reveal the Development Patterns of Asymmetric Skeletal Class III Malocclusion?

To investigate whether 3D mandibular-condylar morphology features derived from cone-beam CT can differentiate between normal and pathologic developmental patterns in patients with asymmetric skeletal class III malocclusion.

A 3D skull model was generated from cone beam CT scans of 90 patients (mean age: 19.4±5.0 y; 53 female, 37 male). On the basis of menton deviation, unilateral mandibular skeletal patterns were classified into 3 groups: deviated group (DG, nondeviated/long side), nondeviated group (NDG, deviated/short side), and nonmandibular deviation group (NMDG, no detectable deviation). The novel 3D Condylar Remodeling Scoring System (CRSS) was used to qualitatively assess condylar morphologic changes and stability. Quantitative analyses of condylar development included measurements of condylar volume, condylar height (CH), and the CH-to-ramus height ratio (CH/RPH). On the basis of the Obwegeser criteria, paired-sample t tests were first used to compare anatomic differences between the long side and short side. Through the test results, unilateral mandibular bones were scientifically classified, and the classification characteristics and patterns of unilateral mandibular bones in patients with skeletal class III mandibular deviation were systematically analyzed.

Cortical continuity was intact in 99.4% (179/180) of condyles. No significant differences in CRSS scores were observed among DG, NDG, and NMDG (8.1-8.7, P >0.05). The DG exhibited significantly greater CH (25.5±3.8 mm) compared with the NDG (23.2±3.8 mm, P =0.001) and NMDG (23.2±4.8 mm, P =0.004) groups. CH/RPH differed significantly across groups (Kruskal-Wallis H =11.06, P =0.004), with DG (0.69) showing higher values than NMDG (0.59, P =0.004). This study analyzed all mandibular asymmetry cases with hemimandibular elongation using the Obwegeser classification, revealing exclusive mandibular condylar hyperplasia (MCH) with nonmandibular ramal hyperplasia (nMRH)/nonmandibular body hyperplasia (nMBH).

In skeletal class III malocclusion with mandibular deviation, short-side condyles with continuous cortical architecture and CRSS ≥8 are classified as normally developing, while long-side condyles exhibit hyperplastic growth. The CH/RPH ratio (≈0.59 for normal versus ≥0.69 for hyperplastic condyles) critically distinguishes these developmental patterns. Using the Obwegeser classification, this study demonstrates that skeletal class III malocclusion with mandibular asymmetry exclusively presents as type II (simple condylar hyperplasia) in unilateral mandibles, with significant enrichment of condylar hyperplasia in the long-side group.