Comparison of Geometric Displacement between Lateral Cephalometric Radiograph and Photograph

Objectives:The purpose of this study was to compare the geometric displacement between the lateral cephalometric radiograph and photograph. Methods:52 subjects with Angle Class I occlusion and no severe skeletal discrepancy were selected. The Head Posture Aligner and the standardized camera set up were adopted to obtain photographs and radiographs in a standardized manner. Six metal markers were placed on the subject's right side face representing Glabella (G), Zygoma (Zy), Philtrum (Ph), Soft tissue Gonion (Go'), Soft tissue Pogonion (Pog'), Soft tissue Menton (Me') before taking the lateral cephalometric radiograph and photograph. The 14 linear, 28 angular, and 5 area differences were measured after superimposition of the radiograph and photograph using nose and upper lip as a reference on the Image Analyzer. Results:1. When the linear measurements were compared between the lateral photograph and radiograph, the measurements related to Zy and Go' except Zy-Me' and Go'-Ph showed significant differences on both images. 2. On the angular comparison, the overall measurements except Me'-Ph-Pog', Ph-Pog'-Me', Ph-Me'-Pog', G-Me'-Ph, Me'-G-Ph, Ph-Go'-Pog', Go'-Zy-Me' and G-Go'-Me' showed significant differences on both images and especially the measurements related to Zy showed greater difference. 3. In area measurements, the overall measurements except G-Zy-Go' showed enlargement of the radiograph. 4. On the superimposition of the radiograph and photograph, the measurements related to the profile tended to be well matched. However, Zy on the lateral radiograph tended to be displaced downward and backward more than Zy on the photograph. Furthermore Go' on the lateral radiograph tended to be displaced upward and backward more than Go' on the photograph. Conclusions:The results suggested that the precise superimposition between the lateral cephalometric radiograph and photograph was not feasible due to differences in enlargement.