- Author
-
Cassel, James M.
|
Tesk, J. A.
|
Brauer, G. M.
|
Antonucci, J. M.
|
Wu, W.
- Title
- Properties and Interactions of Oral Structures and Restorative Materials. Annual Report October 1, 1980 - Steptember 30, 1981.
- Coporate
- National Bureau of Standards, Washington, DC
National Institute of Dental Research, Bethesda, MD
- Report
-
NBSIR 81-2431,
December 1981,
157 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
dental materials
|
cements
|
wear
- Identifiers
- small angle scattering
- Abstract
- New dental cements that overcome major shortcomings of zinc-oxide-eugenol type materials were formulated. The new cements, based on esters of vanillic acid or its isomers, do not inhibit polymerization of methacrylate resins that they contact and have improved strength and solubility properties over previous cements. The softening of dental composites by chemical solvents selected for food simulation was demonstrated to directly affect their wear performance as measured with a classical pin (stainless steel) or disc (composite) wear apparatus. Wear resistance following immersion of the composites in ethanol/water solutions correlated with changes in hardness as a result of the immersion. Small angle x-ray scattering (SAXS) Analysis has yielded information on the volume concentration and characteristic length of microcracks in both in vitro and in vivo worn composite specimens. Theoretical calculations showed that for the porcelain/alloy thickness ratios (i.e. greater than or equal to 1) being employed experimentally, interfacial effects could be neglected for the split ring gap change (compatibility) analysis and a knowledge of a precise value for Poisson's ratio was not required for accurate assessment of residual stresses. (A castability test was refined to the point that a castability value can be determined for any given dental alloy).