{'fraction_non_alphanumeric': 0.03562653562653563, 'fraction_numerical': 0.006756756756756757, 'mean_word_length': 4.88086642599278, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Effects of hollow structures added by selective laser sintering on the mechanical properties of Co-Cr alloy.

PURPOSE
This study investigates the effects of hollow structures, added by selective laser sintering (SLS), on the mechanical properties of a Co-Cr alloy for providing an optimal structural property to the framework components of removable partial dentures (RPDs).


METHODS
The specimens produced using the 3D data of the dumbbell-shaped cylinders were divided into four groups based on the manufacturing method: Cast, Mill, SLS-solid, and SLS-hollow. Tensile tests were performed to measure the mechanical properties of the specimens. The mechanical property values among the four groups were statistically compared using the Kruskal-Wallis test followed by the Steel-Dwass test (α = 0.05).


RESULTS
The median elastic modulus was the largest in the Cast, followed by SLS-solid, Mill, and SLS-hollow, with no significant differences observed between all conditions. The median ultimate tensile strength was the largest in the order of SLS-solid, Mill, SLS-hollow, and Cast. The median 0.2% proof stress was the largest in SLS-solid, followed by SLS-hollow, Cast, and Mill. The median elongation was the highest in the order of Mill, SLS-solid, SLS-hollow, and Cast.


CONCLUSIONS
With the addition of hollow structures, the elastic modulus decreased while the mechanical strength and proof stress remained high in SLS specimens. In addition, the ISO 22674 standard for dental metals was met, suggesting that SLS may be a possible method to design RPD frameworks with high strength and optimal structural properties.