The Optimization Design In Rehabilitation Of The Edentulous Maxillary Defects By Three Dimensional Finite Element Analyses

Maxillary defects are common maxillofacial diseases, the edentulous unilateral maxillary defect and the bilateral maxillary defect have great influence on patients' life, it's a challenge to rehabilitate these defects, using implants is the best way till now. To investigate the distribution of stresses in support tissues with different design is helpful for realizing the optimization design in rehabilitation of these maxillary defects.Objective: To find an effective and flexible method to establish 3-D finite element model of the edentulous unilateral maxillary defect and the bilateral maxillary defect, investigate the distribution of stresses in support tissues with different implants design under occlusal force, realize the optimization design of the maxillary defects.Methods: Establish 3-D finite element model based on material object; study the stresses distribution in support tissues by finite element analysis. The detail as following:1, Scanning a normal man's head by multislices helical CT to get precision data of the slices' images in DICOM format; Inputting the data into expert medical images reconstruction software to build 3-D model of maxillary by PC; Getting material object of this model by RE(reverse engineering) software.2, In Ansys, establishing 3-D finite element model of edentulous maxillary and cranial skeleton from the material object to investigate and compare the role of maxillary in transferring occlusal force with complete upper denture and implanted complete overdenture, examine the stresses distribution on the wall of maxillary sinus.3, Establishing emulational 3-D finite element model of the edentulous unilateral maxillary defect to compare the influence of the loading and the implant design on the stresses distribution in the bone surrounding the implants.4, Establishing 3-D finite element model of the bilateral maxillary defect to investigate the stresses distribution in support tissues with different super-structure.Results: 1, The 3-D CAD model reflected the whole and the detail geometric shape of the maxillary, could help getting the vivid impression of maxillary sinus, nasal cavity directly. It's easy to establish 3-D finite element model by using the CAD model.2, The 3-D finite element model of the whole maxillary and cranial skeleton showed good geometric similarity, it provided a base for establishing 3-D FE model of the whole cranial-facial skeleton.3, Three vertical pillars(canine, zygomatic and pterygoid) could be observed, and the stresses on the wall of maxillary sinus was first described in this study.4, In rehabilitation of the edentulous unilateral maxillary defect, health of the bone surrounding I1 is most important; After placement of implants in the zygoma, the stresses of this area decreased dramatically.5, In rehabilitation of the bilateral maxillary defect, there are little distinguish in stresses distribution between three methods. The whole maxillary prostheses retained with combined application of implants , ovalframework and magnetic attachments is the most effective way to restorebilateral maxillary defect at present.Conclusion: According the method, the 3-D FE model of maxillary andcranial skeleton was established and with favorite similarity in geometric, the study verified the modeling method is feasible and effective. In this study, the stresses in support tissues after restoring the maxillary defects were investigated and the results could be used to realize the optimization design in rehabilitation of the edentulous maxillary defects.