The Empirical Study On Feasibility To Fabricate Ni-Cr Alloy Coping With Laser Rapid Forming Technique

The dental prosthetic restoration is fabricated mainly by hand-made manner customarily. The inextricable problems have been showing up in applicating the customary technique more or less. However the semiautomatic or automatic technique, which emerged and have been applying in field of fabricating dental prosthetic restoration, have some insufficiency. If the more advanced automatic processing technique is brought into this field, it can promote the technique of fabricating dental prosthetic restoration enormously by elevating processing efficiency and improve quality of restoration to redeem the insufficiency of available technique now. In the past few years, the technique of Laser Rapid Forming (LRF) emerged and was brought into this field, showing obvious potential ascendency. This study is to probe the feasibility of fabricating Ni-Cr alloy coping with LRF to establish the empirical base for clinical application. The route of this study was concordant with the flowsheet of dental CAD/CAM, beginning with three dimensional measurement and reconstruction of abutment tooth and CAD of coping, then researching the technology of LRF and fabricating the coping with LRF, evaluating the feasibility of fabricating coping with LRF by analyzing adaptation finally.The contents and methods of this study can be described as follows:Firstly, the reliability and accuracy of the 3DSS-II color structured-light scanning system on reconstructing abutment tooth was identified to seek the suitable methods for abutment tooth. Secondly, the mimical maxillary abutment tooth models were scanned and reconstructed with the chosen methods, and the suited coping was designed by CAD manner. Thirdly, the forming regularities of LRF were discovered, and the LRF parameters and the maximum radian of formed contour fitting for fabricating Ni-Cr alloy coping were obtained. At the end, the coping was fabricated and inspectted with adaptation.Results presented in this study can be summarized as follows:1. It is feasible and reliable to scan and reconstruct the model of abutment tooth by 3DSS-II color structured-light scanning system, but it's precision can not meet the demand of digital impression of abutment tooth.2. 3-diamensions point-clouds of mimical abutment tooth model is abtained by laser scan method, it is reconstructed and coping is disigned with software(Surfacer & Geomagic).3. The rule is obtained how the parameters influence the character of forming: the width and height of the single tract are influenced by power(w), scan velocity(mm/s) and rate of powder feeding(g/min), increasing with power increasing notably, degrading with scan velocity increasing notably, increasing with rate of powder feeding increasing not notably. The parameters fitting for fabricating Ni-Cr alloy coping are selected: 750w, 10mm/s, 7g/min(diameter of laser spot=0.8mm) primarily. 4. The parameters are decided by forming experiments: 500～600w, 13～15mm/s, 5.3～6.3g/min(diameter of laser spot=0.8mm, increment of Z axis=0.1mm).5. The maximum radian of contour forming is obtained: 12.51°.6. The coping is fabricated with selected parameters, and the adaptation is better than the reference of 120μm which is accepted generally in test of adaptation.Conclusions: The Ni-Cr alloy coping can be fabricated with Laser Rapid Forming successfully. But the equipment is used for industry, LRF may become a new technique of fabricating coping for clinical application with reforming the equipment and technique.