Morphological Classification Of Mandible Posterior Region Based On Cone Beam CT Images

Objective:The purpose of this study is to reconstruct the mandible of Chinese people by conebeam CT,to analyze and classify the morphology of the mandible in the posterior teeth,and to compare the differences between the sex group and the age group.To explore the changes of buccal and lingual morphology of mandible in Chinese,so as to provide reference for clinical implantation of mandibular posterior teeth,and to reduce the complications related to the injury of mandibular anatomical structure.Materials and methods:208 patients were enrolled in Fujian Medical University from November 2015 to March 2018.There were 101 males and 107 females,aged 19-76 years,with an average age of(41.0 + 2.5)years.The samples met the following criteria:(1)age(> 18 years old);(2)healthy adjacent teeth,no severe periodontal disease or ceramic crown restoration;(3)no serious uncontrolled systemic disease;(4)no history of smoking;(5)only one tooth was missing and the missing time was longer than 12 months.Using cone-beam CT(Carestream Health,USA),the scanned data are transferred from the CT host to the image workstation.The data in DICOM format are imported into CS 3D Imaging V3 software,and the mandible is reconstructed in three dimensions.In the image of three-dimensional reconstruction model,surface reconstruction is carried out at the curve cutting interface,and the cross-section is adjusted to the neck of lower anterior teeth.The surface is reconstructed by drawing a line through the midpoint of alveolar ridge in turn.According to the measured tooth position,the sagittal position of the data image is adjusted,and different types of axes of premolars and molars are recorded in different axial standard planes.The classification and analysis are proposed.Results:The results showed that type A(vertical type)(79%-96%)was the most common in the premolars,whereas type B(inclined type)(36%-37%)and type C(lingual inverted concave)(30%-54%)were the most common types in the molars,followed type D(absorption severe type)(2%-5%).There was a statistically significant differences in tooth positions(P<0.001)and in tooth deficiency aspect(P<0.01),different age(P<0.001),and different gender(P=0.007).Conclusions:In this study,208 cases of mandibular buccal-lingual morphology were analyzed by cone-beam CT.The results showed that the mandible gradually inclined from near to far from the vertical shape to the lingual side,and formed a certain inverted concave on the lingual side,so as to classify the morphology.There are significant differences in the jaw morphology of different dental positions,and with the increase of the time of tooth loss,the jaw gradually absorbs and changes in morphology.The changes of jaw morphology in different sex and age groups were not significant.The judgement based on palpation can provide a reference for the implant surgeon and for the prevention of lateral wall perforation in the implant operation of the posterior mandibular region in the absence of clinical three-dimensional imaging data.