These tests used compact partable indenters of the type generally used in industry for quality control. The hardness no is based on the depth of penetration of the indent patient into the materials. Abrasion and Abrasion Resistance Abrasion is a complex mechanism in the oral environment that involves an interaction between numerous factors. Usually hardness has often been used as an index of the ability of a material to resist abrasion or wear that the reliability of hardness as a predictor of abrasion resistance is limited. Although it may be used to compare materials that are similar i.e. one brand of cast metal with another brand of the same type of casting alloys it cannot be used to evaluate different classes of materials eg. Synthetic resin with metal. The hardness of a material is only one of the factors that affect the wear of the contacting enamel. Other factors are: 1. Biting force. 2. Frequency of chewing. 3. Abrasiveness of the diet. 4. Composition of liquids. 5. Temperature changes. 6. Roughness of each surface.
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