Fatigue resistance and retentive force of cast clasps treated by shot peening

Purpose: The fatigue failure of denture clasps has often been observed in removable partial denture rehabilitation. To increase their fatigue strength, shot peening was evaluated as a surface treatment. In this study, we evaluated the fatigue resistance and retention of cast clasps by using a shot peening treatment. Methods: A cobalt chromium (Co- Cr) alloy, commercial pure titanium (CP Ti), silver palladium gold (Ag- Pd- Au), and a gold platinum (Au Pt) alloy were cast and then treated with shot peening. The retentive forces of the clasps were measured up to a repetition of 10,000 insertion/ removal cycles in distilled water at 37 C. A fatigue test was also performed using a 15-mm cantilever. Specimens were loaded with a constant deflection of 2.0 mm with 20 Hz. A shot peening treatment indicated a better stability of retentive forces than that without shot peening. The retentive force of Co Cr clasps without shot peening was remarkably decreased at 500 cycles of insertion/removal repetition. Results: The clasps with a shot peening treatment provided approximately 1.4-3.6 times higher fatigue strengths than those without a shot peening treatment. Conclusion: To prevent the fatigue failure of the denture clasps and use the dentures for long term, a shot peening treatment would be recommended. 2013 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.