Association between cranial morphology and dysgnathias in adolescents and adults: A prospective case-control study.

BACKGROUND: Cranial deformities in infancy, such as positional plagiocephaly and brachycephaly, have been suggested to influence the development of jaw malpositions. However, the long-term relationship between cranial shape and dysgnathia remains unclear.

OBJECTIVE: This prospective case-control study investigates whether differences in cranial morphology, measured by the Cranial Index (CI), Cranial Vault Asymmetry Index (CVAI), Diagonal Difference (DD), and ear axis offset (EO), are associated with malocclusions classified according to the Angle system in adolescents and adults.

MATERIALS AND METHODS: A total of 146 participants (113 dysgnathia patients and 33 controls with neutral occlusion) were recruited from the Dysgnathia Clinic at the University Hospital Giessen between October 2018 and February 2020. Cranial morphology was assessed using an automated three-dimensional photogrammetric system (VECTRA®), and occlusion was documented with dental impression models. Participants were grouped by Angle classification (Class I [control], Class II, and Class III) as well as by the presence/absence of laterognathia. Statistical associations between head shape parameters and malocclusion types were analyzed using Fisher's exact test and the Kruskal-Wallis H-test (α = 0.05). Only non-syndromal adolescents and adults were included; patients with previous cranial surgery, severe head trauma, or jaw fractures were excluded; controls had Angle Class I occlusion and no history of orthodontic treatment. Cranial morphology was acquired using the VECTRA® 3D stereophotogrammetry system (Canfield Scientific Inc., Fairfield, NJ, USA). Landmarking and analysis were performed in Cranioform Analytics 4.0. We report CI, CVAI, DD and EO as continuous variables; infant-derived thresholds are cited for descriptive context only and are not used for inferential testing in this adult cohort. Angle Class I-III was determined on three-dimensionally oriented plaster models. Models were oriented using standard craniofacial planes to ensure reproducible assessment of molar relationships.

RESULTS: Mean age was 26.3 ± 8.9 years; sex distribution is reported descriptively in the Results tables (female/male proportions). The overall analysis revealed a significant association between CI classes and dysgnathia (p = 0.0042). In particular, a brachycephalic head shape (CI > 81) was significantly more common in Angle Class III malocclusions compared with controls (p = 0.0085). In addition, an ear axis offset (EO > 0.31 cm) was significantly associated with both Angle Class II (p = 0.0027) and Class III (p = 0.0274) malocclusions. No statistically significant associations were found between the indices of cranial asymmetry (CVAI and DD) and either dysgnathia or laterognathia. Notably, only 11.5 % of participants exhibited pathological CVAI values and 6.8 % abnormal DD values, suggesting a lower prevalence of cranial asymmetry in adulthood compared with infancy.

CONCLUSION: Our findings support a relationship between the longitudinal ovality of the head and the development of jaw malpositions, especially with the association of brachycephalic head shapes and Angle Class III malocclusions. The significant association of ear axis deviation with dysgnathias further suggests that variations in cranial base configuration may play a role in the pathogenesis of malocclusion. Longitudinal studies are needed to clarify the developmental mechanisms linking infant cranial deformities and adult dysgnathia.