Three-dimensional Cephalometric Measurement Of Craniofacial Hard Tissues With Normal Occlusion In Anhui Area

Background: Since Broadbent introduced cephalometry in 1931,cephalometry has become a necessary craniofacial imaging technique for clinicians to evaluate and plan the treatment of orthodontic and orthognathic patients.The original cephalometry was based on two-dimensional cephalometric measurements.In 1992,the introduction of cone beam computed tomography（CBCT）solved these problems in traditional twodimensional imaging.It can obtain clear and accurate three-dimensional images.Compared with traditional 2D cephalometric measurement,3D cephalometric measurement is more accurate,however,compared with the two-dimensional cephalometric measurement technique has a mature analysis method and its corresponding normal reference values of the three dimensional cephalometric measurement technology is not mature,so far,only a few study in China and abroad in this field,the related measuring project and sample is not comprehensive,The reference value of three-dimensional cephalometric measurement in Anhui has not been reported,and there is a lack of standard value as a reference for clinical diagnosis and treatment.Objective: The aim of this study is to establish a three-dimensional cephalometric standardized value database for Anhui province,to study the craniofacial characteristics of normal adult population in Anhui,China and to provide effective information for making orthodontic and orthognathic surgery treatment plans of the craniofacial deformity.Methods: 160 normal occlusal volunteers were selected according to the inclusive and exclusive criteria and were photographed by Cone Beam CT（CBCT）.The coordinate system was established for the 3D model reconstructed with Dolphin based on CBCT data,and 38 hard tissue landmarks were located.40 lines and 20 angles were defined and measured,and measurements were analyzed with SPSS 17.0,to evaluate craniofacial features of the overall,midface,maxilla,mandible,alveolar bone,and dentition of the standard population.Results: The 3D cephalometric measurements of craniofacial hard tissues of normal adults in Anhui were obtained.The symmetry of craniofacial hard tissues was good both in males and females with the maximum asymmetry ratio of 2.2% and the minimum of 0.01%.The gender comparisons show that most of lines measured of males are larger than those of females（P<0.01）,while there is no significant difference in the measurements of the midline deviation of upper and lower mandible,the relative deviation of the maxillary and mandible and the protrusion of upper and lower incisor（P>0.05）.Additionally,there is no statistical significance in angles measured between genders（P>0.05）,except for the occlusal plane angle.The results also show that Chinese have unique facial features based on the measured data,compared with other ethnic populations.Conclusions: The symmetry of maxillofacial hard tissues of normal occlusal Han Chinese in Anhui is good.The gender obviously influences line measurements,with generally the measurements of males larger than females,but it has no effect on most angle measurements.The database of Anhui normal samples can provide a guide for making craniofacial treatment plans and evaluating surgical results.