BACKGROUND: The physical property of porcelain fused to metal (PFM) differs from those of its constituents, which nake impacts on PFM,and the mechanical property of most composites can be estimated with mixture rule. However, there are various factors influencing the mechanical property of PFM and great differences found in the estimations, thus it is necessary to combine the theoretical analysis of mechanical property and mechanics of materials by matbematical models, and provide guidances for PFM' s application.OBJECTIVE: To explore the experiment and computing methods of mechanical analysis on PFM repair materials, and analyze its correlativity and internal relation.DESIGN: Three-point bending experiment and mixture rule of the composites were applied to measure and calculate the intensity and modulus of materials, and then the experimental results and computations were compared.SETTING: Repair Department of Stomatology, West China Stomatological College.MATERIALS: According to the different metal-porcelain ratios, 15 PFM test pieces of 26 mm×4 mm×1.5 mm were divided into 5 groups, with 3 in each.METHODS: Three-point bending experiment was used to detect the bending level and elastic modulus of PFM, whose changing rule was observed,and then was compared with theoretical computed value as well as study the correlation.MAIN OUTCOME MEASURES: PFM experimental result, theoretical computation and the comparison of the two,RESULTS: There were obvious correlations between the experimental measurement and theoretical results, which indicated that the mechanical property of PFM could be predicted by the revised formula.CONCLUSION: The mechanical property of PFM has regular relations with the geometrical morphous parameter and mechanical parameter of PFM constituents, and can be predicted and improved by revised theoretical formula.

In this study we compare the experimental and mathematical analyses of mechanical properties of PFM and analyze their correlation levels and inner links. Fifteen PFM specimens with different thickness ratio of metal to porcelain are made , with the shape of 26mm x 4mm x 1.5mm, and are divided into 5 groups, the metal thickness increases with 0.05mm change each among every group from 0.25mm to 0.45mm, the porcelain thickness decreases accordingly. The three-point-fracture test is used to measure their bending strength and elastic modulus, exhibit their changing laws, and disclose their inner relationships. When the whole thickness of the specimen is determined, the fracture load, bending strength and elastic modulus increase according to the increase of the metal thickness. The experimental mechanical properties of PFM are significantly influenced by the thickness ratio of metal to porcelain, and are the same as the theoretical ones calculated by the mixed law formula of compound material. There is significant correlation between the experimental analysis and mathematical analysis of mechanical properties of PFM. The regression coefficients can be obtained to describe this relationship. Further more, they can be used as the corrected parameters of the theoretical formula. The corrected mathematical formula is helpful to predicting and improving the mechanical properties of PFM.
Compressive Strength ; Dental Bonding ; Dental Porcelain ; Dental Stress Analysis ; Elasticity ; Materials Testing ; Metal Ceramic Alloys ; Models, Theoretical ; Tensile Strength