A Preliminary Study On Computer-aided Design And Rapid Manufacture For Orbital Prosthesis

The unilateral orbital defect is a common type of facial defects. Individuals afflicted with unilateral orbital defect suffer not only from the deficit or loss of physiological function, but also from severe adverse psychological consequence. In some worst cases, patients even lose their desire to live. The surgeon is often limited by the specific anatomy character and the availability of tissue. Therefore, prosthesis are usually needed to restore normal facial appearance in most cases. In clinic, traditional facial prosthesis has been made by way of handworked wax pattern, which is difficult and time consuming while the restoration effect could not satisfy the needs of emulation. An unesthetic orbital prosthesis even creates more psychological trauma for the patient than no prosthesis at all. Advances in technology keep renewing interests in developing new fabrication techniques for maxillofacial prostheses in the past decade. New techniques such as reverse engineering, CAD/CAM and rapid prototyping were introduced into the field of prosthesis design and manufacture and dramatically improved the production efficiency and emulational effects of the prostheses. Consequently, they have created a new path for future facial prosthetics and are rapidly becoming the major trend in the development of prosthetic subject.The present study describes the computer-aided restoration of a unilateral orbital defect. The structure light scan technique was used to reconstruct the 3D facial model and measure the major orbital landmarks of healthy side. According to the results obtained above, eyeball was positioned precisely. Selective Laser Sintering(SLS) equipment was adopted to manufacture the wax pattern of orbital prosthesis which was then transformed to silicon rubber prosthesis. The purpose of this article is to explore the feasibility of a novel approach in fabricating the prosthesis in clinic work. The results are listed as follows.1. The plaster model of mandibular dentition was scanned by the structure light projector and the wax pattern was manufactured in RP machine from the reconstructed digital model. The results of comparison on model accuracy (plaster model, digital model and wax model manufactured with RP) showed that there was no statistic difference (P>0.05) between 3 models. The result showed that the wax model manufactured by this CAD/CAM system can satisfy the requirement of clinic application.2. Using the structure light scan and combining the program of Geomagic,reconstruct 3-D digitized model of unilateral orbital defect at social distance,measured major landmarks of the healthy side. By this way, the general characteristics of orbital section was simulated and the position of eyeball of the defect side was ascertained precisely.3. Based on the digital face model, the"normal"anatomy of the deformed region was recreated by mirror projection of the healthy side in Geomagic software. The margins of the mirrored healthy section were transformed to adapt to the deformed areas of the facial model in polygon phase. The eyeball's precise position was ascertained by deleting some data of iris's region and assigning different thickness to various region of orbital prosthesis.4. Then Selective Laser Sintering machine directly manufactured the wax pattern of the definitive orbital prosthesis from the 3-dimensional orbital data. The margin of wax pattern fitted the deformed region quite well. This wax model had a smooth and fine patterned surface. The transformed silicon rubber prosthesis achieved satisfying effect in clinic.In a word, the prosthesis made by this novel method has restored the orbital defect effectively at social distance. The directly manufactured wax pattern simplifies the procedures and saves work time. Furthermore it significantly improved the restoration effect of orbital prosthesis.