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In order to realize reliable sealing and combination of constructional glass and Kovar alloy, the effects of temperature, holding time, roughness and oxide layers on their wetting property were studied. When the temperature increased from 800℃ to 900℃, the viscosity of liquid glass reduced, so the wetting angle decreased from 69.5° to 31.1°. When the holding time prolonged from 5 min to 40 min at 850℃, the liquid glass had enough time to diffuse under the condition of low viscosity, and the wetting angle increased by 30%. With an increase in roughness of steel sheet surfaces, the barrier increased which was needed to overcome by the liquid glass to spread around. When the roughness value Ra increased from 0.186 μm to 0.563 μm, the wetting angle increased from 46.9° to 69.5°. The oxide layer on the surface of Kovar alloy and the liquid glass had diffusion reaction that could form strong ionic bonds, which increased the wetting property considerably, and the wetting angle could decrease by 23.6%. Therefore, during the actual sealing process, increasing the temperature and holding time, decreasing the roughness of steel sheet surfaces, and steel sheet pretreatment could effectively improve the wetting property of the glass and Kovar alloy.

Objective: To analyze the effects of core material and design on the fracture mechanism of veneered all-ceramic crowns., Methods: The fracture process of 6 veneered alumina or zirconia crowns with different core design (well-distributed core, not well distributed core, and core with cervical ring) under load was analyzed by RFPA'2D finite element analysis software., Results: All the six tested crowns fractured due to tension failure, and the crack started at the porcelain in the cusp and spread along the interface between core and porcelain. Under the conditions of this test, the break was only related to the porcelain and not the core, and the crack of porcelain took place earlier in zirconia crowns than in alumina crowns. Minimum stress distribution in cervical ring core design crown and maximum stress distribution in not well distributed core design crown could be seen at the neck area., Conclusions: Zirconia crowns presented greater stress at the interface between core and porcelain than alumina crowns. The not well distributed core design did not increase the rise of break. The neck area was the weak area with tensile stress concentration in the cervical ring core design.

Currently, hip replacement is an effective treatment for some hip joint diseases. The friction and wear of a prothesis in the human body are the main causes for the failure of joint arthroplasty. It is, therefore, very important to simulate the working conditions of a hip prosthesis in order to get an optimal design and successful clinical applications. This article summarizes wear testing methods of hip prostheses and the developing status of their simulators. Three key aspects of the simulators, i.e., the structures, motions and lubrications, are analyzed in detail. At the end, the developing trend of the simulators are discussed.

Objective: To evaluate the effect of core:dentin thickness ratio on the flexure strength, fracture mode and origin of bilayered IPS Empress II ceramic composite specimens., Methods: IPS Empress II core ceramic, dentin porcelain and bilayered composite specimens with core:dentin thickness ratio of 2:1 and 1:1 were tested in three-point flexure strength. Mean strengths and standard deviations were determined. The optical microscopy was employed for identification of the fracture mode and origin., Results: The flexure strength of dentin porcelain was the smallest(62.7 MPa), and the strength of bilayered composite specimens was smaller than single-layered core ceramic(190.2 MPa). The core: dentin ratio did not influence the strength of bilayered composite specimens. The frequency of occurrence of bilayered specimen delaminations was higher in the group of core: dentin thickness ratio of 1:1 than in the group of 2:1., Conclusion: IPS Empress II core ceramic was significantly stronger than veneering dentin porcelain. Core:dentin thickness ratio could significantly influence the fracture mode and origin, and bilayered IPS Empress II ceramic composite specimens showed little influence in the fracture strength.