No abstract

The apparent viscosity of 17 commercially available alginate impression materials was examined using a rheometer. Each material was mixed for 15 s at a temperature of 23 +/- 0.5 degrees C, using a specially designed alginate mixing instrument. The water powder ratio was determined according to the manufacturer's instruction. The mixed alginate paste was immediately transferred to the sample stage of the rheometer or to a commercial perforated metal tray. Over the same time scale adjusted according to the rheometer test, a discrimination test (subjective test) was performed by 16 young dentists (each with more than 4 years experience). The apparent viscosity of all materials rose as a function of time after mixing and most of the material had properties similar to pseudoplastic fluids. The relationship between the results of the subjective test and the experimental values (objective test) with the rheometer was expressed in a quadratic equation. The maximum value of the apparent viscosity derived from this result was 1.52 x 10(3) Pa.s.

No abstract

The fractional stress loss could not be classified by the cement type. Two implant cements [Multilink Implant and IP Temp Cement] showed similar properties with permanent resin cements and temporary glass ionomer cements, respectively. Careful consideration of the choice of cement is necessary.

The shear bonding strengths of a veneering resin to polished, sandblasted, and retention bead-cast commercially pure titanium (cpTi) plates with and without alkaline treatment were measured before and after thermal cycling. The bonding strengths to polished cpTi with and without alkaline treatment decreased remarkably with thermal cycling (p<0.01).The bonding strength to sandblasted cpTi with alkaline treatment at 5,000 thermal cycles showed no significant differences from those before thermal cycling (p>0.05), and those at 20,000 thermal cycles showed values which were quite small (p<0.01). On the other hand, there were no significant differences in the bonding strengths of veneering resin to retention bead-cast cpTi in all conditions (p>0.05).These results suggested that although alkaline treatment is a simple and effective surface modification technique for titanium improving adhesion to resin due to formation of tight-fine rutile particles, it does not provide sufficient bonding durability for long-period restorations.