Component Analysis Of Craniofacial Type Of Xi'an Chinese With Class III Malocclusion

Classâ…¢malocclusion is not an unusual clinical condition. The craniofacial morphology of this kind of malocclusion can be represented as mandibular protrusion, maxillary retrusion or both in the sagittal direction, and high angle, average angle and low angle in the vertical direction. Severe malocclusion will affect the patient's facial appearance and the function of the stomatognathic system, as well as the patient's mental health.Different types of craniofacial development have their own specific features. Once the growth model is established, it is difficult to change the growth pattern. And the three-dimensional structure of the craniofacial disproportion will lead to skeletal malocclusion. Over the years, the debate has been focused on the different types of craniofacial growth pattern. Sagittal abnormality in classâ…¢malocclusion has been studied intensively so far. But there were only few studies on the verticular abnormality. Also manifestation mode of the classâ…¢malocclusion in our county, especially in Xi'an area, is still unclear. We performed a retrospective study on craniofacial type of the Classâ…¢malocclusion in 1177 patients admitted to department of orthodontics, stomatology hospital, Fourth Military Medical University, during 2003-2008. The computer-aided cephalometric X technology has been used and the features of class III malocclusion patients in mixed dentition, early permanent dentition and permanent dentition were studied respectively. The aim of this study is to lay the foundation for further study on etiology, prophylaxis and treatment of class III malocclusion.This study is composed of three experiments as follow:Experiment 1: Component analysis of sagittal craniofacial morphology in classâ…¢malocclusion patients in Xi'an area.All classâ…¢malocclusion patients in mixed dentition, early permanent dentition and permanent dentition were analyzed by computer-aided cephalometric X technology. Of different ages, patients were divided into six groups according to sagittal features: maxillary normal with mandibular hyperplasia group (S1); mandibular normal with maxillary hypoplasia group (S2); maxillary hypoplasia accompanied by mandibular hyperplasia Group (S3);: both maxillary and mandibular normal group (S4); both maxillary and mandibular hypoplasia group (S5);both maxillary and mandibular hyperplasia group (S6). Result: In the mixed dentition of class III patients, craniofacial types in sagittal directions are mainly manifested as maxillary normal with mandibular hyperplasia and followed by mandibular normal with maxillary hypoplasia. In addition to the above two types, all the other four types only accounts for a very small proportion. Craniofacial types in sagittal directions are mainly manifested as maxillary and mandibular normal or maxillary normal with mandibular hyperplasia in early permanent dentition. And in permanent dentition, craniofacial types in sagittal directions are mainly manifested as maxillary normal with mandibular hyperplasia and followed by maxillary hypoplasia with mandibular hyperplasia.Experiment 2: Component analysis of vertical craniofacial morphology in classâ…¢malocclusion patients in Xi'an area.Of the same study object as above, patients were divided into 3 groups according to the vertical features: high-angle group (V1), average angle group (V2) and low-angle group (V3) respectively. Then the component analysis of craniofacial morphology was performed accordingly. Results: In the mixed dentition, craniofacial types in vertical direction are mainly manifested as high angle or average angle, and seldom as low angle. And in the early permanent dentition and permanent dentition, craniofacial types in vertical direction are mainly manifested as average angle, and seldom as low-angle and high-angle.Experiment 3: Cross-analysis of sagittal and vertical craniofacial morphology in classâ…¢malocclusion patients in Xi'an area.The cross-analysis of sagittal and vertical craniofacial morphology was performed based on the data of experiment 1 and 2. Result: In the mixed dentition, craniofacial types are mainly manifested as maxillary normal with mandibular hyperplasia combined with average angle, and followed by mandibular normal with maxillary hypoplasia combined with high-angle or average angle and maxillary normal with mandibular hyperplasia combined with high-angle. In the early permanent dentition, both maxillary and mandibular normal and maxillary normal with mandibular hyperplasia in average angle patients are predominant, and followed by maxillary hypoplasia with mandibular normal combined with average angle. In permanent dentition, craniofacial types are mainly manifested as maxillary normal with mandibular hyperplasia combined with average angle, and followed by maxillary hypoplasia with mandibular hyperplasia combined with average angle.Conclusion:It was demonstrated that Class III malocclusion patient has either sagittal or vertical features. And the component analysis can play a very important role in understanding the detailed features of class III malocclusion. And more important, it is helpful for the future study on the early treatment of class III malocclusion.