PubMed Health⌕ Search

Biomedical subjects

R W Hinman

Publications and source records attributed to R W Hinman.

9 recordsLinked to original sources
PubMed1985

Internal setting expansion of a dental casting investment measured with strain gauges.

A study was undertaken to investigate the feasibility of using strain gauges to evaluate the internal setting expansion of dental casting investments. A strain gauge was invested in the center of a casting ring to determine the linear setting expansion at the site of the wax pattern. The findings suggest that strain gauges can be used to measure setting expansion internally more accurately than volumetric or external surface measurement techniques. It was also found that winged strain gauges were more stable in the investment than wingless strain gauges.

Chemical Phenomena↗
PubMed1985

Effect of a two-step ringless investment technique on alloy castability.

An evaluation of the effects of a two-step ringless partial denture investment technique on the castability of a base metal crown and fixed partial denture alloy was made. Castability values were obtained for 60 test patterns cast on two different casting units at two different mold temperatures. No significant differences were found between the control technique and the experimental technique. However, significant differences were found between castings made by the two different casting units at a temperature of 1250 degrees F.

Dental Alloys↗
PubMed1985

A technique for characterizing casting behavior of dental alloys.

A technique for characterizing casting behavior of dental alloys has been developed and tested. The method employs easily reproducible specimen patterns and uses equipment and procedures generally available in dental prosthetic laboratories. A castability value is arrived at by counting complete segments of a cast alloy grid. Test results indicate that the castability evaluation procedure described can be a valuable aid in the laboratory for both selecting and using dental materials for producing cast restorations. The test method would also appear useful for the evaluation of products and techniques during research and development. An absolute minimum for the castability value determined relative to clinical and laboratory efficacy has yet to be established.

Chemical Phenomena↗
PubMed1983

Effects of porcelain/alloy interfacial diffusion zones on thermo-mechanical strain.

Chemical bonding between dental porcelains and alloys results from interdiffusion of porcelain and metal ions. An interfacial diffusion zone is created which, most likely, has properties different from those of bulk materials. The changed interface might affect experimental measurements of thermo-mechanical strain. To determine the magnitude and conditions under which this would occur, the interface was modeled as the intermediate layer of a three-layered porcelain-veneered split-metal ring. Layer thicknesses and coefficients of thermal expansion were varied, and the effects on gap change after cooling through 500 degrees C were calculated. Results are presented in a series of 14 Figs., ten curves each, which depict not only interfacial effects, but are extended for use in interpretation of the effects of properties of opaques and glazes as well. Under most conditions, the interface will not affect experimental measurements; some special exceptions are noted.

Chemical Phenomena↗
PubMed1975

Factors affecting airborne beryllium concentrations in dental spaces.

Air sampling for beryllium concentrations produced during finishing procedures for a beryllium-containing alloy was conducted in two rooms with capacities of 700 and 10,000 cubic feet. The clearance rate of beryllium in the air and the effect of ventilation and room size on these concentrations were investigated. With local lathe ventilation, no beryllium was found. Without local lathe ventilation, mean 10 minutes concentrations of about 23 mug per cubic meter were found at the breathing zone of the lathe operator in both rooms. At 4 and 8 feet from the breathing zone, sizable concentrations of beryllium above the maximum acceptable standard were found only in the small room. These levels decreased to zero 10 minutes after completion of the finishing and polishing procedure. It was concluded that there was little hazard to dental personnel when local lathe ventilation was used; however, our finding of high concentrations of beryllium in the air when lathe ventilation was not used indicates that continued vigilance must be maintained.

Air↗