ABSTRACT
In case of class II malocclusion, mandible has morphological characteristics such as size and position. To investigate morphological characteristics of mandible, most study has been done in indirect measurement using cephalogram. Recently, it is possible to measure directly Three dimensional skeletal model reconstructed from computed tomography images. This study aimed to know characteristics of mandible in class II malocclusion, analyzing Three dimensional mandible models of class I and II malocclusion which are acquired from computed tomography images of 80 cadavers. In open bite type of class II malocclusion, the size of mandible had no difference from class I malocclusion but the sagittal ramus angle and condylar angle were smaller 3 degree than class I. These findings inform that the ramus and condylar process of open bite type of class II malocclusion stand more erectly than class I and then the mandible is placed posteriorly. In deep bite type of class II malocclusion, the length of mandible was shorter 4 mm and, the sagittal ramus angle and condylar angle were larger 5 degree than class I. These findings, short length of mandible and more lying ramus and condylar process, make the mandible in the feature of deep bite of class II malocclusion. In comparison of past issued articles which used cehpalometry mainly, the values of measurements agree partially. It is the differences of measuring points and methods to make inconsistency between indirect measurement like cephalometric study and 3 dimensionally direct measurement like this study. To increase accuracy of Three dimensionally direct measurement, standardization of measuring points and method for the measurement is required.