Measurement and analysis of indexes of mandibular three-dimensional shape in patients with hemimandibular elongation

Objective: To analyze the morphological characteristics of mandibula for patients with hemimandibular elongation using the indexes of mandibula three-dimensional shape (IM3DS) and calculate reference ranges for normal and abnormal mandibula. Methods: 46 patients with hemimandibular elongation (the disease group) and 46 normal controls (the control group) were included in this study. Cone-beam computed tomography (CBCT) data were stored according DICOM medical digital image communication standard. Mandibula three-dimensional reconstruction was performed using Mimics 15.0. The location marks were used to measure line distance and volume of mandibula, and the results were statistically analyzed. Results: There was no statistical difference in measurements between two groups (P>0.05). For the disease group, the lesion side had significantly greater measurements of WC, WN, HC, LAR, LHR, HM1, HAC, VT, VC, VAR, VB2, and VB3 than the normal side (P<0.05). The differences in other indexes were not statistically significant (P>0.05). Obtained reference ranges for normal mandibula with IM3DS between 1 and 6 were 0.5797-0.8271, 0.5323-0.7087, 0.1377-0.2000, 0.1405-0.1895, 0.1387-0.1427, and 0.0606-0.0802. Reference ranges for abnormal mandibula were 0.3862-0.7092, 0.3351-0.6581, 0.0166-0.3040, 0.1002-0.1900, 0.0968-0.1604, and 0.0914-0.1416. Conclusion: The increase in the volume of mandibula in patients with hemimandibular elongation is mainly at mandibular ascending branch and back of mandibular body with the same development trend as normal mandibula. IM3DS can rapidly and effectively evaluate mandibular shape for patients with hemimandibular elongation, so as to clarify lesion range and degree and provide references and guidance for clinical diagnosis and treatment.