Stress distribution within circumferential clasp arms.

An analysis of stress distributions within circumferential clasp arms with various tapers, was undertaken in an effort to (1) determine the area of maximum stress concentration in both tapered and non-tapered clasps, and (2) to compare this point of maximum stress concentration with the area of frequent clasp breakage. The non-tapered clasp showed better distribution of stresses than the tapered clasps. The less favourable stress concentrations could result in eventual failure of the clasp when coupled with other factors such as porosities. The maximum shear stresses in the non-tapered clasp also were lower than those in the tapered clasps. As the taper of the clasp became more accentuated, the magnitude of the stresses increased and shifted towards the tip of the clasp. The maximum tensile stress calculated in a replica of a chromium-cobalt-nickel clasp was in the order of 34 MN/m2 which is well below the ultimate tensile strength of the alloy. This observation leads to the proposal that failure of clasps is a function not only of design but also of other variables, such as porosities, surface irregularities, and fatigue.