Effect of Maxillary Base Length, Mandibular Body Length, and Ramus Height on Sagittal Skeletal Relationships in Libyan Class II Division 1 Patients: A retrospective Cephalometric Study.

Abstract

Since skeletal class II division 1 malocclusion is a sagittal discrepancy between jaw bases i.e the mandible and maxilla, this study aimed to evaluate the influence of the jaws size cephalometrically measured as the maxillary base length (ANS–PNS), mandibular body length (Go–Pg), and mandibular ramus height (Ar–Go) on sagittal skeletal relationships (SNA, SNB, ANB) in Libyan patients with skeletal class II division 1 malocclusion. A retrospective cephalometric study was conducted on 116 lateral cephalographs (56 males, 60 females). Measurements were digitized and analyzed using Dr.Ceph cephalometric software. Statistical analysis included descriptive statistics, independent t-test, one-sample t-test, Pearson correlation, and multiple linear regression analysis, which were compared to Libyan normal values. In addition to these, three advanced statistical analyses were performed to explore the multivariate structure of the data. Firstly, the binary logistic regression was performed to determine whether the mandibular body length, ramus height, and maxillary base length could predict the severity of skeletal class II discrepancy. Secondly, the principal component analysis (PCA) was performed to identify the main skeletal components explaining variations between skeletal variables, and thirdly, structural equation modeling (SEM) was performed using SPSS AMOS to evaluate the hypothesized causal pathway between jaw dimensions and sagittal skeletal discrepancy. The study showed that no significant sex differences were found (p>0.05). The maxillary base length (ANS–PNS) showed a nonsignificant difference from Libyan normal values (p>0.05). The mandibular body length (Go–Pg) and the mandibular ramus height (Ar–Go) were significantly reduced (p<0.001). Go–Pg and Ar–Go showed significant positive correlation with SNB (r.0.25, p<0.01) each. ANS–PNS showed no significant correlation with SNB (r .0.01, p>0.05). Mandibular sagittal position (SNB) showed a stronger negative correlation with ANB (r = -0.450, p<0.001) than the maxillary sagittal position. Mandibular body length and ramus height are the stronger determinants of sagittal skeletal discrepancy compared to maxillary length, which plays a negligible role. Skeletal class II division 1 malocclusion in this Libyan sample is primarily a mandibular deficiency involving both body and ramus components. The logistic regression confirmed the descriptive, linear regression, and Pearson correlation findings. The PCA showed that the largest source of variation was mandibular, not maxillary, and SEM supports the mandibular-driven pathway.