The dental abrasive testing machine applies a V-like swing arm to driving the wearing part to move along the slope back and forth, which is connected with an eccentric wheel fixed on the crankshaft of the gear motor through a connecting rod. Various abraders can be held on the wearing part with an adjustable wearing pressure between 10 and 500g loaded on the specimen. During wearing, both abrader and specimen are immersed in the wearing medium. Before and after the test, the specimen is weighed and its wearing surface is recorded by a profilometer, then the weight loss and volume loss can be calculated.

Dental Cements ; Humans

Objective: To study the feasibility of sandwich structure made by GP-084 cellular silicone rubber and SY-1 silicone elastomer in preparing facial prostheses. Methods: Samples of SY-1 silicone or GP-084 or sandwich of both were made in the size of 100 cm 2. Sandwich structure was made of SY-1 silicone as the top and bottom lyers of 1 mm in thickness and GP-084 cellular silicone as the middle layer of 23 mm in thickness. The weight density and Shore﹝A﹞hardness of the samples were measured. Results: The weight density (?10 3 kg/m 2) of GP-084, SY-1 silicone rubber and the sandwich structure was 0.411? 0.003, 1.245?0.024 and 0.679? 0.002 respectively(P

Objective: To evaluate the effect of roughness on adhesive properties of polymethyl methacrylate and SY-1 silicone elastomer.Methods:5 specimens of polymethyl methacrylate were polished by sand paper of different standards and the roughness of polymethyl methacrylate surfaces were measured by roughmeter. The tension strength between polymethyl methacrylate with different degrees of roughness and SY-1 silicone elastomer were tested according to national standards. Results: After the surfaces of polymethyl methacrylate were respectively polished by sand paper of the standard 160,320 and 800, the sufrace roughness decreased, but the tension strength between polymethy1 and SY-1 silicone elastomer was increased(P

0.05).The elongation at break of SY-1 was stronger than that of MDX4-4210 (P

0.05). The standard deviation of the distance of 6 to 6 in the water/powder ratio of 33∶10 was extraordinary big(s=0.206).②The time of pouring generated dimensional shrink(P

Objective: To study the denture base adaptation in fl uenced by technical factors. Methods: Thirty six maxilla ry denture bases were fabricated by different conditions of monomer content ,res in stage, polymerization temperature, mixing and cooling temperature conditions respectively. The gap between stone cast and acrylic resin base was measured wi th a stereoscopic microscope with a precision of 0.01 mm at five referential pos itions in each section. The data were submitted to t test. Resul ts: There was statistical significant difference ( P

Objective: To study the bonding interface characteristic of five wet bonding systems while bonding on different dentin bonding surfaces. Methods: Rhodamine B was used to label five adhesives(OptiBond Sol o,Single Bond,Gluma One-Bond,Bond-1 and One-Step) in consistency of 0.1%, an d the bonding interface of the 5 wet bonding systems on dry or wet dentin surfa ces was observed with laser scanning confocal microscope. Results: All five bonding systems could infiltrate well into dentin bonding interface when bonding on wet dentin surface. The fluorescence confocal images gave eviden ce of the adhesives penetrated into the widened tubules, lateral tubules and dem ineralized peritubular dentin. Little discontinuity in dentin tubular was observ ed in the images, especially in those of alcohol-water-based adhesives. When b onded in dry dentin surface, the hybrid thickness of acetone-based adhesives de creased significantly. Conclusion: The penetration ability of ad hesives may be reduced significantly on dry dentin surface.

0.05),respectively.The fractured adheisive dentin surface was mainly a mixed failue mode.Conclusions:There is no significant difference in the bond strengths of each of the three bonding agents to ND and CAD.

The experiment was conducted on the actions of 5 kinds of reagents on HL - 60 cellular wither, viz. Yisuiling chloroform extract, rabbit serum chloroform extract, rabbit liver paste chloroform extract, Etoposide, and normal rabbit serum. Results revealed that after fluid incubation for a short period, the HL-60 cultured cells showed no wither in the former 4 groups under microscope and flowing cytometer. Among them, action was strongest in rabbit liver paste of Yisuiling extract group, similar to the positive control of Etoposide. Followed by rabbit serum, and the action was weak in Yisuiling chloroform extract. There was no obvious action of induced wither by normal rabbit serum. The mechanism of induced wither is still under investigation.