Experimental Research On The Reconstruction Of Large Mandible Defect Via Rapid Prototyping

In clinical work, it is found that jaw defects could be caused by tumor, infection and the developmental deformity. All these diseases result in not only the facial deformity but also the functional loss of oral maxillofacial system, such as mastication, deglutition and speech dysfunction. Thus patients who suffered from those are living with low quality. To resolve this problem, many researches have focused on this field but it is still a difficult matter in maxillofacial surgery. With the development of maxillofacial surgery, many methods have been applied in the reconstruction of jaw defects, but till to now the limit quantum and additional trauma of bone supply, and the difficulties for reshaping still exist. A material with favorable biocompatibility, good flexibility and intensity, the capability for easy to shape and low liability of additional trauma may be of great help. Titanium seems to be the right candidate for its biocompatibility and physical and chemical characteristics and has been comprehensively used inmaxillofacial surgery. As the titanium now used is pre-shaped before the operation, most of them need to be reshaped according the exact bone defect. It must cause long operation time. In addition, the titanium after reshaping couldn't be exactly consistent with the bone defect because the reshaping mostly depended on the experience of the surgeon. As it was reported, this and the resulted stress distributing are major factors for unsuccessful reconstruction. In order to increase the ratio of titanium for jaw reconstruction, the shape consistency must be highlighted, but it not easy to meet this demand as the figure of jaws is very complex. The newly developed technology, rapid prototyping (RP), perhaps does some good way. RP, involved with computer-aided design, laser process, digital control and new material exploitation, very specializes in duplication of little and complex matters. Maybe it can be used for the shaping of titanium mesh for jaw reconstruction but few literatures were found. In this study, the experimental research pn the reconstruction of large mandible defect via rapid prototyping was conducted.Dogs were used in this study for establishment of mandible defect and the reconstruction. Through surgery manner, mandible defects of 7.0cm'2.0cm, including the complex angle region were obtained. The status of dogs after operation was observed and 2 weeks later, mandible defects were detected by X-ray and scanned through 3D CT, the data were used for 3D reconstruction of mandible defects. Also with these data from CT scan, software Mimics 7.10, Surfacer7.1 and Digisurf were applied to establish the digital model of mandible defects. After the models were established, titanium meshes for individual mandible defect weredesigned according to the shape and function of mandible. CAD was applied in this program to achieve the digital model of special titanium meshes. The digital data were then imported for sterolighthography, and thus the resin stereotype of digital model of special titanium meshes were obtained. The titanium meshes were cast directly from the resin models and then underwent a serial of treatment as polishing, passivation. Then the meshes could be used for animal experiment. In this study, the animal experimental for mandible defect reconstruction was also done. 22 dogs were randomly divided into 3 groups, 12 for RP titanium meshes, 8 for pre-shaped titanium meshes, 2 for control groups. Large bone defect of mandible were made in every animal. Ilium was acquired for reconstruction in the first 2 groups but not in control group. In operation, the consistency of meshes with bone defects was observed and so did the dogs' statuses after operation. 8 weeks and 16 weeks later, species were acquired respectively for histological study. And the outlines of mandibles were recorded and X-ray examinations were conducted.In this study, the large bone defect model of mandible is characterized with stability and easiness for establishing. Through surgical manner, in this model, ma...