Experimental And Clinical Research On Mandibular Augmentation With A "Sandwich" Method

Purpose1. To compare the difference of accuracy between cephalometric and computed tomographic analysis, to study the changes in width of soft and hard tissue contour of lower face and analyse the influence of mandibular augmentation with natural coral implantation.2. To study the influence of natural coral and coralline hydroxyapatite on mandible, masseter muscle and inferior alveolar nerve after mandibular augmentation with sandwich method. To analyse the morphological changes of mandible with CT reconstructive and imaging method.3. To report two cases receiving mandibular augmentation with coralline hydroxyapatite, to analyse the indication and contraindication, and to analyse the morphological changes of lower face contour with X-ray cepholometric and CT measurement.Methods and materials1.25 patients with hemifacial microsomia received cephalometric analysis. The distance had been tested from skeleton contour to midline through gonion, incisor point superior of maxilla, incisor point inferior of mandible, the difference with data from CT measurement had been compared. Different changes in width of soft and hard tissue contour had retrospectively analysed in cases after mandibular augmentation with natural coral using a sandwich method, and regression analysis had done and the rate of asymmetry had been calculated.2. The physical and chemical features had been measured.9 goats were selected and randomly devided into three groups. All goats received mandibular augmentation with sandwich method, one side with natural coral and another with coralline hydroxyapatite. Computer tomography was applied at 6 months,12 months and 18 months, one goat had been randomly selected and partial mandible, masseter muscle and inferior alveolar nerve had been harvested to do pathological section and ultrastructure analyses. The area of masseter muscle fiber and the lenghth of sarcomere were measured. The mandible of other animals were sent for biomechanical test. All the CT data were applied for morphological analysis, the thickness and volumn of mandible were calculated.3. Two patients with hemimandibular dysplasia received mandibular augmentation with sandwich method using coralline hydroxyapatite. Soft and hard tissue contour had been measured through cepholograms. Morphological analyse were made with X-ray film and CT data, changes in thickness and volumn of mandible had been analysed.Results1. Both cepholometric analysis and CT analysis were feasible for measuring width of lower face, two methods had no significant differences (P>0.05). Three layers' measurements accurately reflected changes in width of lower face contour. High correlation between soft and hard tissue contour was detected, the changes of them had a regulation.2. Both natural coral and coralline hydroxy apatite were suitable for mandibular augmentation. Natural coral were degraded at about 6 months postoperation, coralline hydroxy apatite needed 12-18 months. Although the thickness of mandible had no significant difference at 12 and 18 months after surgery, the volumn resulted in difference. This method had little influence on masseter muscle and inferior alverolar nerve.The changes in area of muscle fiber and the length of the sarcomere between two materials had no significant differences (P<0.05). CT imaging analysis could also be an effective method to evaluate the changes of contour.3. Mandibular augmentation with the sandwich method could be effective to improve mandibular thickness and correct facial asymmetry in clinical appliance following strict indications and contraindications.Conclusion1,Cepholometric and CT measurements, imaging analysis based on CT data were suitable for disgnosis and surgical assessment in lower face asymmetry.2,Mandibular augmentation with the sandwich method was also an effective way to improve mandibular thickness and facial asymmetry.3,In goat model, coral hydroxyapatite and natural coral were suitable for mandibular augmentation. However, further study of the influence on masseter muscle amd inferior alveolar nerve is still worthwhile. The effectiveness and safety of clinical appliance relys on feedback of long-term follow-up.