Fatigue resistance of titanium-nickel alloy cast clasps

In this study fatigue resistance of experimentally prepared titanium-nickel (50.8% nickel and 49.2% titanium) cast clasps was evaluated in a simulated clinical situation. The change in force required to remove the titanium-nickel clasps was recorded under a repeated placement-and-removal test on steel model abutment teeth. Commercially-pure titanium, cobalt-chromium alloy, and gold-silver-palladium-copper alloy clasps were also tested for comparison. The tips of the clasps were located in the 0.25- and 0.50-mm undercut areas of the abutments. No significant changes in the retentive force were found in titanium-nickel clasps in the 1,010 repeated cycles, whereas the other three types of clasp revealed a significant decrease in the force required for removal during the test procedures (repeated analysis of variance P < 0.001). The results suggest that the cast titanium-nickel clasp may be suitable in removable prosthodontic constructions because of its significantly less permanent deformation during service. This report also discusses clinical applicability and some current problems with this new application.