Resistência à abrasão e resistência à compressão de materiais para modelos e troquéis: influência de sua imersão prévia em óleo.

Gypsum products are generally considered, by the majority of investigators, to possess the greatest amount of desirable properties, when used as model or die materials. The property, however, in which they are less efficient is the one related to abrasion resistance. The authors describe a new method to measure the abrasion resistance of gypsum products and recomend their immersion in innert mineral oil, prior to their use, in order to increase this proferty. Studdying, simultaneously, the compressive strenght of the same materials, the authors verify that, even though some of the gypsum products have their compressive strengts diminished due to a previous immersion in oll, the d'fferences, expressed in kg/cm², have no clinical significance, considering their use as model or die materials, which are much more subjected to abrasion or cutting actions in the dental laboratory. The results were statistically analysed.