BACKGROUND: There are many species of ceramic bonding systems supplied in market, the mechanical strength is aprerequisite condition for resin cement in clinical use.OBJECTIVE: To study the difference of mechanical strength between Panavia F resin cement and self-made resin cement,DESIGN, TIME AND SETTING: A controlled observational study was performed in the prosthesis laboratory of the FourthMilitary Medical University of Chinese PLA between May 2006 and March 2007.MATERIALS: Panavia F resin cement was sourced from KURARAY MEDICAL INC. (Japan), experimental resin cement wasproduced by College of Stomatological Medicine in the Fourth Military Medical University of Chinese PLA.METHODS: Five cylindrical compressive strength specimens at an 8-mm height and 4-mm diameter were prepared, as well as5 cylindrical diametral tensile strength specimens at a 3-mm height and 6-mm diameter. AGS-500 universal material testingmachine was applied to detect the compressive strength and diametral tensile strength.MAIN OUTCOME MEASURES: The diametral tensile strength test and compressive strength test of the specimens.RESULTS: The compressive strength of Panavia F resin cement was remarkably higher than that of experimental cement[(238.92±24.54), (149.08±12.13) M Pa, P ＜ 0.05]. There were no significances between two resin cements on diametral tensilestrength (P＞ 0.05).CONCLUSION: There were no significance between two resin cements on diametral tensile strength following completecuring. The compressive strength of experimental resin cement can reach the standard of ADA (＞ 70 MPa) although it is lowerthan the compressive strength of Panavia F resin cement.

BACKGROUND: Irradiation therapy in the cancer patients after surgery may have negative effects on implant fixation. OBJECTIVE: To observe the effects of 60Co irradiation and trace element zinc on fixation strengths of titanium implant. METHODS: Thirty-six adult male rabbits were involved. One piece of titanium implant was separately placed into the bilateral proximal tibial heads in rabbits to set up animal models of titanium implants. The animals were randomly divided into control group, zinc supplement group, 60Co irradiation group and 60Co irradiation and zinc supplement group. Zinc sulfate of 10 g/L was administered intramuscularly to animals in the zinc supplement group at the dose of 4 mg/kg once per day, and those in the control group were treated with saline at the same dose. The animals in the 60Co irradiation group received 60Co irradiation at the dose of 45 Gy and saline by intramuscular injection. Those in the 60Co irradiation and zinc supplement group received 60Co irradiation and zinc sulfate. The animals were killed at 1, 4 and 12 weeks after treatment. The fixation strengths were measured and compared among groups. RESULTS AND CONCLUSION: (1) Zinc supplement made the titanium implants have higher fixation strengths, and reach a high level at 4 weeks after surgery. (2) 60Co irradiation significantly inhibited the fixation strengths of the implants. After 60Co radiation, zinc supplement stil could promote fixation strengths of titanium implants. (3) It is indicated that amount of zinc supplement after irradiation therapy can al eviate the negative effects of irradiation on implant fixation.