Carvability

The clinical characteristic selected for this test was the "limit of carvability," the amalgam consistency at which the dentist feels that further carving embodies an excessive risk of fracture. A punch test approximating pure shear loading was selected to measure this property. Results of hand-carving tests made on specimens indicate that the clinical limit of carvability is approximated closely by that time at which the load required for punching is 25.5 lb.

None of the specifications, however, contains any method for determination of the carvability of the amalgam, and so far no correlation seems to have been shown between an objectively measurable property of dental amalgams and their carvability. It is the purpose of this work to investigate whether the carvability of amalgam is correlated with its tensile strength.

Dentine owes its strength and carvability to its composite nature—pure hydroxylapatite is brittle but cracks in ivory are stopped where they run from the crystals into the organic part of the material.