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 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.

Objective: To comparative the mechanical properties of f our kinds of denture resin. Method: The impact strength, f lexural strength, flexural elastic modulus and Brinell hardness of four denture resin materials, Shanghai Shanhu(SH),Shanxi Changzhi(CZ), Luciton 199(LC) and Me liodent(MD), were measured in vitro and the stress-strain curve of each ma terial under flexural force was drawn. Results: The impact strength(kJ/m 2) of SH,CZ,LC and MD were 9.94?2.25,6.55?1.85,13.76?4.31 and 13.70?3.71; flexural strength (MPa) 75.27?3.24,78.88?7.66,80.47?3.27 and 7 6.72?3.14; flexural elastic modulus(GPa) 3.08? 0.15 ,2.96?0.10,2.63?0.11 a nd 2.56?0.12; Brinell hardness(kg/mm 2)24.15?1.34, 23.43 ? 1.65 ,20.86? 1.26 and 18.49?1.71,respectively. Conclusions: Comparativ ely speaking, SH and CZ are rigidit and brittle, LC is rigidit and sturdy, MD is tough and sturdy.

Objective: To investigate the adhesive characteristics of two kinds of light-curing resin that was used to bond teeth and orthodontics brackets. Methods: A total of 60 premolar teeth were randomly divided into six groups, and brackets were bonded according to the manufacturers' instructions. In group A1, A2 and A3, the teeth were prepared using 100 ml/L polyacrylic acid, and the brackets were bonded using Fuji Ortho LC. In group B1, B2 and B3, the teeth were using self-etching primer, and the brackets were bonded using Transbond Plus Self Etching Primer (TPSEP). After 30 min and 24 h under room temperature and received cold-heat cycle treatment respectively, bond strength was measured using a testing instrument (2000S, Lloyds Instruments, Fareham, England) at a speed of 1 mm/min, and the residual adhesive was quantified using a stereomicroscope. The adhesive interface was observed by scanning electron microscope. Results: The bond shear strength of TPSEP and Ortho Glass LC are more than 5 MPa. The bond shear strength of TPSEP is stronger than that of Ortho Glass LC after 24 h. However,The adhesive remnant index (ARI)of TPSEP is higher than that of Ortho Glass LC. Conclusion: Transbond Plus Self Etching Primer and Ortho Glass LC can satisfy the clinic need of orthodontics.

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