Purpose: The objective of this in vitro study was to evaluate the effect of thermocycling on retentive forces of different esthetic thermoplastic partial denture clasp materials including, polyoxymethylene (Acetal), polyetheretherketon (PEEK) and monomer free semi-rigid microcrystalline polymer (karadent).
Material and methods: 2 Testing models with 2 natural premolar teeth used to test the retentive force of three types of esthetic thermoplastic clasps (N=6) Acetal, PEEK and karadent. After Thermo-cycling, the retention force of the clasps was measured at the same cross head speed. The data were collected, tabulated and a statistically analyzed using SPSS v26 , Kruskal Wallis was used for comparing quantitative non-parametric data of more than two different groups, followed by post-hoc Dunkan's while Wilcoxon signed rank was used to compare quantitative non-parametric data of two related groups.
Results: PEEK group has recorded a high statistically significant difference in retention force mean values prior to thermo-cycling, P-value ≤0.001. Following thermo-cycling, reduced retention force mean values were found for all groups with non-significant difference between the groups and a significant difference within each group. For the percentage of changes, there was a significant difference between the groups with the least percentage of changes in the Acetal clasp group. p ≤ 0.05
Conclusion: Within the limitations of this study, it was found that the thermoplastic resin clasps-showed a decreased retention values when exposed to thermo- cycling (2000 cycle) between (5 C-55 C) 30 seconds with significantly lower percentage of change for the Acetal than Peek and karadent esthetic clasp materials.