The minimal occlusal thickness of amalgam restoration for appropriate resistance to fracture is:

# The minimal occlusal thickness of amalgam restoration for appropriate resistance to fracture is:

A. 0.5 mm

B. 0.8 mm

C. 1.5 mm

D. 2.5 mm

The correct answer is C. 1.5 mm.

The relatively horizontal pulpal and gingival walls, prepared perpendicular to the tooth’s long axis, help the restoration resist occlusal forces and limit the likelihood of tooth fracture from wedging effects caused by opposing cusps. It may be necessary to reduce cusps that no longer have sufficient dentin support and cover (or envelope) them with an adequate thickness of restorative material in order to provide resistance to fracture of the tooth and/or the restorative material. Preparation design must allow for adequate thickness of polycrystalline restorative materials to ensure adequate primary resistance to restoration fracture. he minimal occlusal thickness, for appropriate resistance to fracture, of amalgam is 1.5 to 2 mm and glass-ceramic is 2 mm. Polymeric restorative materials (e.g., composite resins) have no minimal thickness.

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