RELATIONSHIP BETWEEN TRANSVERSE BASAL ARCH WIDTH AND MOLAR INCLINATION: A CBCT STUDY IN YEMENI ADULTS

Background: Transverse skeletal discrepancies in adults are often underdiagnosed, particularly when masked by dentoalveolar compensation such as molar inclination. This study aimed to evaluate the relationship between transverse basal arch width and molar angulation in Yemeni adults using cone-beam computed tomography (CBCT).
Methods: A retrospective CBCT analysis was conducted on 87 untreated Yemeni adults (17–40 years). Participants were classified into normal and narrow maxilla groups based on the maxillary–mandibular basal width difference (Mx–Mn). Skeletal widths were measured on standardized basal planes, and first molar inclination was recorded relative to skeletal reference lines. Group comparisons were performed using t-tests, while correlations were assessed with Pearson’s r. Intra-examiner reliability was verified with ICC.
Results: The narrow maxilla group demonstrated a significantly smaller maxillary width (54.55 ± 2.8 mm) than the normal group (57.55 ± 3.1 mm; p < 0.001), accompanied by a greater mandibular width (57.5 ± 3.3 vs. 55.2 ± 3.1 mm; p = 0.003), resulting in a negative Mx–Mn difference. Upper molars exhibited greater buccal inclination (195.2° ± 11.4 vs. 189.8° ± 7.2; p = 0.028), whereas lower molars showed more lingual inclination (146.3° ± 10.6 vs. 155.1° ± 8.5; p < 0.001). Strong correlations were found between Mx–Mn and molar inclination (upper r = +0.535; lower r = −0.463; both p < 0.001). ICC exceeded 0.90.
Conclusion: Molar inclination functions as a compensatory mechanism in the presence of transverse skeletal imbalance. Incorporating both skeletal and dental assessments through CBCT enhances the detection of concealed transverse disharmony and facilitates more individualized orthodontic treatment planning.