CRANIOFACIAL MORPHOLOGY OF SKELETAL CLASS III MALOCCLUSION IN MIXED DENTITION

Objective To compare the difference between the craniofacial hard tissue of skeletal Class Ⅲ malocclusion and that of normal occlusion in mixed dentition, and to speculate the etiologic mechanism and craniofacial development trend of skeletal Class Ⅲ malocclusion. Methods Thirty eight children with skeletal Class Ⅲ malocclusion in mixed dentition were selected as a study group, and another 40 children at similar mean age with normal occlusion served as a control group. Lateral cephalometric radiographs at central occlusion were taken. Results In the linear analysis of the hard tissue, 11 variables in male and 10 variables in female were significantly different between the study group and the control group( t=2.083-2.569,P0.05; t=2.827-3.476,P 0.01). Seventeen variables in angular measurement of the hard tissue were significantly different between the two groups ( t=2.245-2.672,P0.05; t=2.937-3.429,P 0.01). Five variables in the ratio of linear measurement differed significantly( t=2.189-3.528,P 0.01). Conclusion Mandibular hyperplasia is the main factor responsible for Class Ⅲ malocclusion. Disharmony of craniofacial relation leads to skeletal malocclusion.