The relation between maximum flexibility, proportional limit and modulus of elasticity may be expressed mathematically as follows. E = Modulus of elasticity P= proportional limit Em = maximum flexibility P Since E =
em P
em = e Resilience As the inter atomic spacing increases internal energy increases. As long as the stress is not greater than the proportional limit this energy is called as resilience. Resilience can be defined as the amount of energy absorbed by a material when it is stressed to its proportional limit. To compare the resilience of 2 materials we must plot stress strain graphs and observe the area of elasticity in these graphs. The material with larger elastic area has more resilience. When a dental restoration is deformed during mastication, the chewing force acts on the tooth structure, the restoration or both. The magnitude of deformation is determined by the induced stresses. In most dental restoration large stains are precluded due to the proprioceptive response of the periodontal ligament.
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