Elastic Modulus — MFDS Part 1 MCQ

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ModerateDental MaterialsElastic ModulusMFDS Part 1

In a tensile stress–strain test of two dental restorative materials, material X has a steeper slope than material Y within the linear elastic region. This finding indicates that material X has greater:

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Correct answer: D — Stiffness (resistance to elastic deformation)

Explanation lettering: E = shown as A · D = shown as C · A = shown as D · C = shown as E

A is correct. Young's modulus is the slope of the stress–strain curve within the linear elastic region. A steeper slope means that more stress is required to produce a given elastic strain, so material X is stiffer and more resistant to elastic deformation. Strength concerns the stress sustained before yielding or failure and cannot be inferred from the elastic slope alone. Hardness is resistance to local indentation or scratching. Toughness is the total energy absorbed before fracture, represented by the area under the stress–strain curve. Ductility describes the amount of plastic deformation sustained before fracture.

Reference: Spears IR. A three-dimensional finite element model of prismatic enamel: a re-appraisal of the data on the Young's modulus of enamel. Journal of Dental Research. 1997;76(10):1690–1697. https://pubmed.ncbi.nlm.nih.gov/9326902/