Effect of cyclic bend loading on a cobalt-chromium clasp fabricated by direct metal laser sintering.

STATEMENT OF PROBLEM: Limited information is available regarding the mechanical properties of a partial removable dental prosthesis clasp fabricated by direct metal laser sintering (DMLS). PURPOSE: The purpose of this in vitro study was to measure the mechanical properties of cast clasps, DMLS clasps, and annealed DMLS clasps and to determine the correlation between cyclic bend loading, annealing, and mechanical properties. MATERIAL AND METHODS: Sixty half round clasp specimens were fabricated, with a length of 20 mm and a diameter of 1.5 mm at 10 mm from the tip. The specimens were divided into 6 groups (n=10). Twenty specimens were fabricated by casting (CS, CSAC), and 40 specimens were fabricated by DMLS (DS, DSAC, ADS, ADSAC). Of the DMLS specimens, 20 underwent annealing (ADS, ADSAC). Equivalent to 5 years of clinical use, 0.25 mm of bending was applied to group CSAC, DSAC, and ADSAC 14 600 times. After cyclic bending loads, a cantilever bend test was conducted on all groups, and the loads were measured. To compare the load values, 1-way ANOVA and the Tukey HSD test were performed and statistical significance among the groups was evaluated (alpha=.05). Scanning electron microscopy and energy-dispersive spectroscopy analyses were also used for surface morphology evaluation and element analysis. RESULTS: Bending loads of the DMLS specimens were significantly lower than those of the cast specimens (P<.05). The influence of cyclic bending loads was significant for cast specimens (P<.05), but not for DMLS specimens (P>.05), in terms of variation of loads. Annealed DMLS specimens had significantly higher bending loads than DMLS specimens (P<.05). CONCLUSIONS: The DMLS specimens had lower load values at 0.25 mm bending than cast specimens. The DMLS specimens were less influenced by cyclic bending loads than the cast specimens. Annealing increased load values of the DMLS specimens at 0.25 mm bending.