The CBCT Study Of The Hard Tissue Morphology Of The Maxillofacial Region In Adult Patients With Deep Overbite In Liaoning Area

Deep overbite is one of the common malocclusion,which is defined as: anterior teeth margin over the lower anterior teeth crown length more than 1/3.Severe deep overbite not only affect the normal function of temporomandibular joint,can lead to periodontal problems and tooth wear,but also interfere with the normal function of chewing,so orthodontic or orthognathic surgery to be corrected.In the current clinical,there have been many effective treatment method for the correction of deep overbite such as rocking chair archwire,anterior flat plate,screw or J hook,and orthognathic surgery.However,the effective play of each method must be based on the corresponding causes: the teeth or bone,or otherwise two.In the past,the study on the characteristics of deep overbite of the teeth and bones is based on the plaster model,the lateral radiographs of the skull and the curved surface,which is also a traditional 2D method.Although traditional cephalometric methods have been explored and verified by a large number of clinical orthodont ic practitioners,their accuracy and reliability have been supported by a large number of literature and clinical cases.However,the human teeth,jaw,face system,after all,is a three-dimensional system,by means of two-dimensional research inevitably e rror.In recent years,CBCT has been widely used in clinical practice,and it can be used for 3D reconstruction from the corresponding software.It can be used to measure the relationship between the point,line,surface and angle of the oral and maxillofacial system.In view of the above research,the purpose of this experiment is to study the three-dimensional morphological characteristics of the craniofacial hard tissue in patients with deep overbite by 3D cephalometric technique,and provide a more accurate and reliable basis for the formation mechanism of deep overbite.This study is divided into two parts:The first part: the study on the reliability and accuracy of the location of the bonylandmarks of three dimensional cephalometricObjective: To study the reliability of two fixed points in the same and different measurement.Methods: from 160 CBCT data in 40 randomly selected patients(20 cases,male 20 cases of female)of the CBCT data,select 31 craniofacial hard tissue landmarks,3D reconstruction of CBCT data using MIMICS17.0 software,and the application of multi planar joint point(multi-planer reconstruction,MPR)method respectively,in the sagittal,coronal and axial direction with three point.Finally,the correlation coefficients(intraclas s,correlation,ICC)of the two coordinate parameters of the different measurement and the same measurement were analyzed by coefficients.Result:1.the same measurement results: ICC value greater than 0.99 accounted for 48.9%(43/88),accounting for between 0.90-0.99(41/88),and less than 0.90 of the,S points,Me points,Ar_L points and Or_R points.Among them,S points,Me points on the X axis of the coordinate value of credibility is poor,Ar_L points on the Y axis of the coordinate value of credibility is poor,Or_R on the Z axis of the coordinate value of credibility is poor.2.The results of 2 different measuring points: ICC values greater than 0.99 accounted for 40.9%(36/88),between 0.90-0.99 accounted for 52.3%(46/88),and less than 0.90 have 6,respectively,S point and Me point and Gn point,Po_L point,Ar_L point and Or_R point.Where S points,Me points,Gn points,U1 root points on the X axis of the coordinate value of credibility is poor,Ar_L points on the Y axis of the coordinate value of the credibility of the poor,Or_R on the Z axis of the value of the credibility of the poor.Conclusion:1.based on the data of CBCT,the accuracy and reliability of the three dimensional localization of the hard tissue landmarks of the cranial and maxillofacial regions were higher;2.multi plane joint fixed-point method is feasible in three-dimensional cephalometric analysis;3.with the same surveyor to mark the location of the high stability;The second part: CBCT study on the hard tissue morphology of maxillofacial region in adult patients with deep overbite in Liaoning areaObjective: To investigate the characteristics of the teeth and bones of adult patients with deep overbite,and to provide more accurate diagnosis and treatment.Methods: in the orthodontic Department of General Hospital of Shenyang military region with 160 copies of the CBCT data standard,the deep overbite group 80 cases,80 cases of normal control group,MIMICS 17.0 using 3D reconstruction software modeling,draw a point line surface 3D data,using paired samples t test was used for statistical analysis.Results: the characteristics of bone,mandibular plane angle,mandibular angle and mandibular and cranial triangle,deep overbite groups were lower than the normal control group,while the mandibular ramus length ratio,high,high above and behind the front and behind the high high,deep overbite group than the norma l control group,the high and below high and high and high above the front were the ratio of deep overbite were small.In the characteristics of the teeth,the axial inclination of the upper and middle incisors was smaller than that of the normal control group,while the depth of the Spee curve was significantly higher than that of the control group.The length of maxillary central incisor eruption and the length of mandibular first molar eruption were the same in the two groups,the former increased in the deep overbite group and the latter in the deep overbite group.Conclusion: the counterclockwise rotation of the mandible and the deepening of the Spee curve and the increase of the depth are the important mechanisms of the formation of deep overbite.