The Study On Surgical Treatment Of Mandibular Deviation Deformity And Correlative Elementary Research

BackgroundMany research shows that the non-significant asymmetry face is widespread in general population, beauties also have physiological asymmetry.The Mandibular deviation deformity refers to the mandibular appears asymmetric at the cranial midline, which is the most common type of facial asymmetry deformity. It is named by morphology. Currently, there is no clear diagnosis about the mandibular deviation deformity. The chin deviation could be the major feature of that, and one of standards of diagnosis. Normal facial is not completely symmetrical, and chin is not completely is in the center of the face.but this kind of asymmetry is slight, and it would not affect the aesthetic appearance. Therefor that should not be called the mandibular deviation deformities. When the chin deviates over a certain degree, it should be called mandibular deviation.Michiels said that the chin is the most sensitive indicator of diagnosis of mandibular deviation.In the most mandibular deviation research,it is used to assess the mandibular deviation.Haraguchi found people is sensitive to the asymmetry that chin is deviated over4mm.In clinic, Machida’s research said the diagnosis of mandibular deviation is gnathion deviate over4mm in frontal cephalometric X ray film.In this study, diagnosis of mandibular deviation use that standard.Fukusima found that80%of facial asymmetry deformity only occurred in the mandibular by frontal cephalometric X ray film. Haraguchi’s study found there is more common of left deviation than right. Study found that70%-85%of the mandibular deviation patients associated with osseous Class III malocclusion. At present, the main treatment of mandibular deviation are orthodontic, distractive osteogenesis, dental arch expanding treatment, surgical treatment, jaw adjusting treatment, and so on. Jaw deflection deformation through simple orthodontic treatment only can correct some of the light source sex bone deformities.Orthodontic treatment could correct slight mandibular deviation deformities.Most should be corrected by surgical treatment.The common complication of the surgical treatment is the respiratory tract obstruction, nerve damage, root injury, bone nonunion, temporomandibular joint disturbance, infection, and so on.There are many reasons for that, Surgeons are unfamiliar with the anatomy of mandible and its adjacent structure is one of the most important reasons. This study is about surgical treatment of mandibular deviation and correlative elementary research, aiming at carrying out surgical treatment of mandibular deviation better and providing relevant basic theory to reduce complications.Part one. The anatomical study of mental foramen areaObjectBy studying mental foramen area and the applied anatomy, providing the security bone cutting line of the surgery of chin area, such as anterior mandibular subapical osteotomy, chin plastic and aesthetic surgery, and so on. Aim to avoid complications such as injury of the mental nerve and root injury. Methods10cases(male6cases,female4cases) of adult head specimens fixed by formalin, are grinded the outer surface bone cortex, exposing the mandibular canal, mental canal, incisor nerve canal and the roots of lower teeth, and observing these anatomy and relative measurment.Results1.Mandibular canal is divided into mental canal and incisor nerve canal, mental canal bends backward, upward and outward then opens into mental foramina, incisor nerve canal moves forward, ending at below the mandibular lateral incisors or between mandibular central incisor and lateral incisor. Pipe diameter ratio of mental canal and incisive neural canal is about3:2, while length ratio is about1:5.2.In the majority, the mental foramen appear below the teeth between the forth and the fifth.3.The horizontal distance from the front of mental foramen to the front of mandibular canal is about3.47±0.37mm; the vertical distance from the inferior margin of the mental foramen is about3.53±0.33mm; the vertical distance from the root of canine teeth is about6.62±0.57mm.4.The vertical distance from the inferior margin of the incisor neural canal to inferior margin of the mandible is about7-13mm.Conclusion:The surgical safe zone of mental foramen area should be4mm ahead and4mm below of the mental foramen,5mm below of tooth root. The distance from the incisor neural canal to the inferior margin of the mandible is non-constant and variable, about7-13mm above the inferior margin of the mandible. The surgery of chin area should be operated13mm above the inferior margin of chin for avoiding incisor nerve injury. Osteotomy line of the mental foramen plane would not damage the teeth root. Considering the individual difference, medicine image should be combined in clinical.Part two.The research on the sprial CT of mandibular canalObject:From the scanning data of spiral CT of head, analysing the mandibular canal layers, aim to avoid complications such as injury of interior alveolar nerve and bone fracture.Methods:Since December2010to January2013,60persons is selected who scaned the head sprial CT in Zhujiang Hospital affiliated Southern Medical University. Among them,30cases male and30cases female, aged from18to38years old, with the average age of24years. The selected materials should also meet the following criteria relatively symmetrical maxillofacial, no abnormalities, no malocclusion. Five cross section of mandibular are obtained, measuring the thickness of ramus of mandible,outer and inner surface bone cortex, and the distance between mandibular cannal and outer bone cortex, and then analysing the layers of the mandibular canal.Results1.From top to bottom, Changes in the thickness of ramus of mandible,outer and inner surface bone cortex shows increasing trend.2.From top to bottom,mandibular is close to the inner bone cortex.3.Individual difference is big in the distance between mandibular cannal and outer bone cortex, some case is disappeared.4.Comparing men and women, there is statistical significance in thickness of ramus of mandible, but not in marrow cavity of mandibular.Conclusion The head spiral CT could show clearly the layer and location of mandibular canal. From the results,there is increasing trend in the thickness of ramus of mandible, outer and inner surface bone cortex, and the distance between mandibular cannal and outer bone cortex. When operating sagittal split ramus osteotomy, it should pay attention to the cross-sectional fracture mandible while cutting inside of mandibular ramus, and also to cutting completely while carrying out the inferior margin of the mandible osteotomy. The variation of the distance between mandibular cannal and outer bone cortex, it is almost disappeared in some cases,sagittal split ramus osteotomy is not recommended.Part Three:The research on Surgical treatment of mandibular deviation.ObjectThe treatment efficiency of the mandibular deviation deformity is analysed and evaluated by skull PA and LAT, aiming at carrying out surgical treatment of mandibular deviation better and providing relevant basic theory to reduce complications.MethodsThe retrospective study from September2010to January2013, a total of47patients of mandibular deviation were received surgical treatment. According to the operation methods, the whole is divided into three treatment groups. The first group is received the pure bone plastic, the second group is sagittal split ramus osteotomy as elemental surgery while the third group is anterior mandibular subapical osteotomy. The treatment efficiency of the mandibular deviation is analysed and evaluated by skull PA and LAT. Result47cases of mandibular deviation patient all get satisfactory front and side face via surgical treatment. Among the total47cases,34cases is very satisfactory,11cases basically satisfactory,2unsatisfactory cases after the second surgery were content with the effect.2patients appeared accident bone fracture while operated sagittal split ramus osteotomy, one appeared mental nerve broken, sensation recovered one year after operation. The lower lips of patients received sagittal split ramus osteotomy were numb to various degree, but recovered nearly4-8months after operation. Other patients got good recovery of mastication, osteotomy line, and there is no complications of bone nonunions and teeth root damage. In the group two and three, the upper and lower teeth centerline and malocclusion of the patients were normal after intermaxillary traction and orthodontics after surgical treatment. The results of evaluations are as follows:1. The first group:From the indicators before and after the surgery, differences between bilateral distances from the gonion to chin point, the chin point to the facial midline have statistical significance, others not, showing the mainly changes in this group is the point of chin. Less changes in the indicators of lateral view.2. The second group:Change of indicators, including the front and lateral view is biggest, asymmetry coefficient of mandibular ascending ramus changed from6.68±1.64%to3.94±1.12%.3. The third group:The protrusion of chin changes from-5.49±1.97mm to-3.83±2.23mm, but there is no statistical significance. The changes is big in Li-EP, and have statistical significance.Result:The clinical manifestation of mandibular deviation deformity is various. So the treatment methods should be accorded to the patient’s own condition. It is accurate to use3-D CT reconstruction of hard and soft tissue for evaluating the pre-operation osteotomy and the size of implant. When the patients need correcting the malocclusion, Model surgery and intraoral splint are used to determine osteotomy method. Anterior mandibular subapical osteotomy is the best way to correct mandibular alveolar bone hyperplasia. It commonly shows Class I malocclusion, and also could be Class III malocclusion. Indications of sagittal split ramus osteotomy are wide, and could be used as the basic operation method. Compare with anterior mandibular subapical osteotomy, the sagittal split ramus osteotomy is more effective to backward movement of chin.The common complication of the surgical treatment is the respiratory tract obstruction, nerve damage, root injury, bone nonunion, temporomandibular joint disturbance, infection, and so on.The variation of the distance between mandibular canal and outer bone cortex, it is almost disappeared in some cases,sagittal split ramus osteotomy is not recommended. The safe zone of anterior mandibular subapical osteotomy should be4mm ahead and4mm below of the mental foramen,5mm below of tooth root.The key link to the respiratory tract obstruction is bleeding, edema secretion and vomiting. Before the internal fixation of sagittal split ramus osteotomy, the condyle should be ascertained at right position in the acetabulum.The main reason of bone fracture in bilateral mandibular sagittal split osteotomy and mandibular Angle osteotomy is incomplete cortical bone cutting. The blood supply of mandibular comes from the inferior alveolar artery and surrounding soft tissue.In this study, chin grinding surgery meet the expected requirement.