Volumetric Analysis of the Jaws in Skeletal Class I and Class II Patients using CBCT and Derived Lateral Cephalograms

Abstract

Introduction: Cone Beam Computed Tomography (CBCT) imaging recently has become a very common diagnostic tool in the orthodontic literature. Recent research work has shown that CBCT imaging would give additional information regarding the volumetric assessment of the craniofacial structures. However, the previous published work has not considered the impact of the anterior-posterior skeletal classification and the vertical skeletal pattern on the volumetric assessment of the maxillary and mandibular bones. Aim: To evaluate maxillary and mandibular volumes (MxV and MdV, respectively) in hyper-divergent skeletal Class II (CII) and normo-divergent skeletal Class I (CI) patients and to investigate any possible correlation between CBCT derived lateral cephalometric variables and the calculated volumes. Materials and Methods: CBCT images of 60 patients (30 patients: CI, 30 patients: CII) were obtained and processed with Mimics® 17 software (Materialise, NV, Belgium). The threedimensional models of both jaws were reconstructed and the related volumes were calculated using a novel approach. CBCT based cephalograms were also derived and linear and angular measurements of the craniofacial complex were obtained. Significance tests were based on t-tests (alpha set at 5%) and Pearson’s correlation coefficients were calculated. Results: No significant differences were detected between the two groups in the MxV (p=0.435) and the MdV (p=0.507). In the CI group, no or weak correlations were found between the volumetric measurements and the 2D variables. In the CII group, there was a strong correlation between both MxV and MdV and both the posterior facial height (r=0.60, 0.78 respectively) and the facial height index (r=0.62, 0.72 respectively). A negative moderate correlation was found between both MxV and MdV and the mandibular plane angle (r=-0.48, -0.44 respectively) and Bjork's sum (r=-0.48, -0.44 respectively). Conclusion: There were no significant differences in the MxV and MdV between CI and CII skeletal patterns. Some cephalometric variables had moderate to strong correlation with the MxV and MdV in the CII group.

Keywords

• derived cephalograms
• hyper-divergent
• class ii patients
• mandibular volume
• maxillary volume
• normo-divergent class i patients