| The Metal-porcelain Prosthesis is also called porcelain-fused-to-metal (PFM). It is a kind of metal-ceramic complex restoration which is fused to cast metal coping by low-melting porcelain under vacumm condition. It has great strength and esthetic characteristics. In the treatment of patients with dentition loss and dentition defect, it has a variety of clinical applications.However, there are increasing problems in the quality and security about the PFM ,such as the black line,mucosal pain, excessive erosion, mucosal necrosis and severe systemic adverse reactions etc. More importantly, there was no nondestructive testing method of the inner crowns composition in the PFM based on the Guangdong Province and state food and drug administration;even if there exist serious issues about the quality of the alloy used in the dental prosthesis processing factory, harmful impurities, the contents of noble metal elements etc.To settle the above problems, Ni-Cr- metal ceramic alloys, Ti-metal ceramic alloys, Au -metal ceramic alloys were choosed as the subjects in this paper. With the combining of the theory and practice, this research constructed the precious standard through the accurate destructive test (including Dimethylglyoxime Photometry , Potentiometric titration with ferrous sulfate, Inductively coupled atomic emission spectrometry, ICP-AES);then, the nondestructive testing method of the inner crowns composition in the PFM was selected by comparing the results among the destructive tests and nondestructive tests (including Scanning electron microscope with X-ray spectrum analysis ,SEM-EDS; and Electron microprobe analysis,EPMA).Results: 1. In the aspect of destructive testing , the Ni content of Ni-Cr ceramic alloys increased 16.36% after casting; while Cr, Mo, Al were all less than 2% at relative difference value. The absolute difference value between the test results and manufacture value of Ni, Cr, Mo in titanium ceramic alloys group were all not more than 3% before casting; while after casting they were 11.52%, 4.552%, 3.750%. The Ni content increased 8.55% after casting,and the relative difference value of other elements were less than 2.50%. In gold ceramic alloys group,the relative difference value of Au, Pd, Pt were all less than 0.56%,and their absolute difference value less than 4%. The results indicated that the alloy composition may vary as casting forming process. 2. Comparing the results among the destructive tests and nondestructive tests,the results of electron microprobe analysis were the closest to the destructive test results.The relative difference value of Ni, Pt approximated to 3%, and other major elements less than 1%.While the relative difference value between SEM-EDS tests and the destructive tests was among 3%～5%,and the relative difference value of Ni in titanium ceramic alloys was up to 6.277% . In addition, the relative difference value of Ni between the results of EPMA and SEM-EDS was 7.007%, and Au was 4.248%. 3. The relative standard deviation of the EPMA was 0.32%～4.8%.Conclusions: The EPMA can be used as a non-destructive testing methods in inner crown alloy composition of PFM,which has precise measurements and wide range of quantitative analysis.The results of this research maybe can provide laboratory evidence for the quality of supervision on metal ceramic restorations, and then contribute to establish a perfect quality supervision system and industry standards, prevent counterfeit from endangering people's interests and health, ensure the patient's medical safety, and promote the healthy development of the denture processing enterprises. |
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