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

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

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

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.

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 evaluate the effects of different kinds of fluorides and their loading on the fluoride releasing characteristics of fluoride containing composite resins. Methods Two paste type of composite resin, containing NaF and K 2TiF 6 respectively, were prepared. The composite resins were based on Bis GMA/TEGDMA resin and loaded with fluoride at 5%, 10%, 15% and 20% by weight, and a non fluoridated composite resin was prepared as the control. Six standardized discs (6 mm?3 mm) were made of each material, and three discs of each material were stored in plastic vials containing 5 ml deionized water at 37 ℃ respectively and the others in artificial saliva. The water and the artificial saliva were changed every 24 hours. An ion selective electrode (9606BN Orion) connected to an ion analyzer (720A Orion) was used to determine the amount of fluoride released on days 8, 15, 22, 29 and 62. The data were analyzed using t tests. Results All of the fluoride containing materials demonstrated a higher fluoride release than that from non fluoride control materials. The composite resin containing NaF released significantly more fluoride than that of K 2TiF 6. All materials showed a significantly higher release of fluoride in water than in artificial saliva ( P