Laboratory comparative study of three different types of clasp materials

Purpose The objective of this in vitro study was to evaluate the retentive strength of 3 clasp materials Acetal resin (Ac), Cobalt- Chrome (Co-Cr) alloy and Nickel-Chrome (Ni-Cr) alloy before and after cyclic loading. Materials and methods A total of 72 clasps (24 clasps for each material) were fabricated on standardized metallic molar models. The clasps of each material were divided into 3 groups 8 clasps each according to degree of undercuts (0.01, 0.02 0.03 inch). Each clasp assembly was subjected to 730, 1460, 2190 and 2920 cycles of insertion and removal of a removable partial denture. Retentive strength was measured before and after each cyclic period. Retentive strength values were analyzed using ANOVA and Fisher s PLSD multiple comparison test at the 0.05 level of significance. Results Ac clasps had significantly lower retentive strength than Co-Cr and Ni-Cr clasps. Clasps with 0.01 inch undercut showed significantly less retention than clasps with 0.02 inch undercut and the latter showed significantly less retention than clasps with 0.03 inch undercut. All clasps exhibited continuous significant decrease in retentive strength from the first period of cyclic loading till the end of the cycling except for Acetal resin at 0.01 inch undercut which show no significant difference after 730 cyclic loading. Conclusion There was significant decrease in retentive strength of the 3 clasp materials.