A new wear testing system, which carries out toothbrush wear and simulated occlusal wear tests alternately, was developed. Differences in wear behavior among three modes of wears, combined wear, toothbrush wear and simulated occlusal wear, were investigated using polymethylmethacrylate (PMMA) and two commercial resin composites (Z100, APX). The area of the material loss after each test was measured on the worn surfaces to evaluate the different modes of wears. On PMMA and Z100, the toothbrush wear corresponded to the combined wear, suggesting that toothbrush wear was dominant in the combined wear for these materials. On the other hand, the occlusal wear was dominant corresponding to the combined wear on APX. Both the simulated occlusal wear and toothbrush wear tests are essential to evaluate the wear behavior of restorative materials, and the combined wear test is effective to analyze the wear behavior of restorative materials under different wear processes which consist of toothbrush wear and simulated occlusal wear.
Composite Resins/chemistry , Dental Materials/chemistry , Dental Occlusion , Dental Restoration Wear , Polymethyl Methacrylate/chemistry , Silicon Dioxide , Toothbrushing/instrumentation , Zirconium , Analysis of Variance , Humans , Materials Testing , Methacrylates/chemistry , Resin Cements/chemistry , Surface Properties
The objective of this study is to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. The experimental investments were prepared using a gypsum-bonded investment in which the metallic powders such as boron (B), silicon (Si), aluminum (Al) and titanium (Ti) were added as oxidizing agents. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The effect of the addition of each metal powder was evaluated from the color difference between the as-cast surface and the polished surface of the cast specimen. The color of the as-cast surface approached that of the polished surface with increasing B and Al content. A lower mean value in the color difference was obtained at 0.25-1.00 mass% B content. B and Al are useful as an additive in a gypsum-bonded investment to prevent the blackening of an Ag-Pd-Cu-Au alloy. The effects of Si and Ti powder addition could not be found.
Calcium Sulfate/chemistry , Dental Alloys/chemistry , Dental Casting Investment/chemistry , Reducing Agents/chemistry , Aluminum/chemistry , Boron/chemistry , Color , Oxides/chemistry , Silicon/chemistry , Titanium/chemistry
