Objectives:The purpose of this study was to evaluate the reproducibility of measurements representing asymmetry of mandible, and to identify which landmarks are more useful in three-dimensional (3D) CT imaging.
Methods:Facial CT images of forty normal occlusion individuals who did not have any apparent facial asymmetry were reconstructed into 3D image using V-worksTM (Cybermed Inc., Seoul, Korea). Condyle, gonion, and menton area were major factors in determining the shape of mandible, a total 18 landmarks were constructed on these areas according to the sub-positions and views. A total 25 measurements for representing asymmetry were obtained, including 21 linear measurements (8 for ramal length, 12 for mandibular body length, 1 for condylar neck length) and 4 angular measurements (2 for frontal ramal inclination, 2 for lateral ramal inclination). The procedures were performed by four examiners and repeated one more time by one examiner in two weeks.
Results:1. Inter-examiner reproducibility of linear measurements proved to be high except for 3 measurements (Cdsup_sup - Gomid_obl, Gomid_obl - Me_ant, and Gomid_obl - Me_inf).
2. Inter-examiner reproducibility of angular measurements representing frontal and lateral ramal inclination proved to be high.
3. Intra-examiner reproducibility of linear measurements proved to be high except for 2 measurements (Cdsup_sup - Gomid_obl and Gomid_lat - Me_inf).
4. Intra-examiner reproducibility of angular measurements representing frontal and lateral ramal inclination proved to be high.
5. Inter and intra examiner reproducibility of measurements including Gomid_lat and Gomid_obl (two of 18 landmarks) proved to be low.
Conclusions:The above results suggest that the identification of landmarks (Cdsup_sup, Cdlat_ant, Cdlat_lat, Cdpost_lat, Cdpost_post, S, Goinf_lat, Goinf_inf, Golat_ant, Golat_lat, Gopost_lat, Gopost_post, Ag_lat, Ag_inf, Me_ant, Me_inf) and measurements using those landmarks in three-dimensional CT imaging can be used for facial asymmetry diagnosis.