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Journal of Prosthetic Dentistry

The effect of build orientation on the microstructure and properties of selective laser melting Ti-6Al-4V for removable partial denture clasps

  • Wenqiang Xie
    Affiliations
    Graduate student, Department of Stomatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, PR China

    Resident, Stomatology Hospital of Guangzhou Medical University, Guangzhou, PR China

    Graduate student, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-Sen University, Guangzhou, PR China
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  • Meihua Zheng
    Correspondence
    Corresponding author: Dr Meihua Zheng, Department of Stomatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, 107 Yanjiang Road West, Guangzhou, PR CHINA
    Affiliations
    Professor, Department of Stomatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, PR China
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  • Jieqi Wang
    Affiliations
    Resident, Department of Stomatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, PR China
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  • Xiaoyu Li
    Affiliations
    Resident, Stomatology Hospital of Guangzhou Medical University, Guangzhou, PR China
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      Abstract

      Statement of problem

      Selective laser melting (SLM) Ti-6Al-4V has been used for removable partial dentures, but the impact of SLM Ti-6Al-4V build orientation is not evident.

      Purpose

      The purpose of this in vitro study was to investigate the microstructure and properties of SLM Ti-6Al-4V clasps with different build orientations compared with cast Ti-6Al-4V clasps.

      Material and methods

      Forty-eight clasps were made from Ti-6Al-4V alloys—by SLM with 3 different build orientations (SLM0, SLM45, and SLM90) and cast (CAST) as a control. The microstructure was investigated by using a metallographic microscope and a confocal laser scanning microscope. The fit and surface roughness of the clasps were measured, and the physical properties were evaluated. In addition, the von Mises stresses in the clasps were calculated by finite element analysis. All specimens were then subjected to insertion and removal tests in artificial saliva to model 5 years of clinical use. After these tests, 3-point bend tests were used to analyze the fracture surface of the clasp arms, which were observed by using a scanning electron microscope. All data were statistically analyzed (α=.05).

      Results

      The microstructure of the Ti-6Al-4V specimens was a comixture of α+β phases. In addition, growth directions of β grains were approximately parallel to the build orientation, with acicular α grains present between β grains. SLM0 and SLM45 had significantly higher roughness than SLM90. Even though the fit was inferior to that of SLM90, SLM0 and SLM45 still performed better than cast specimens (P<.05). The finite element analysis showed that the maximum von Mises stress was located on the middle part of the retainer arms and that the values of the 0.50-mm undercut clasps were much lower than the elastic limit. In addition, the decrease of retentive force in SLM90 clasps was less than that of the CAST group (P<.05). CAST clasps showed brittle fracture, whereas all SLM clasps showed ductile fracture.

      Conclusions

      The microstructure of SLM Ti-6Al-4V affected the properties of clasps by changing the anisotropy of specimens. Among the tested groups, SLM90 clasps had the best fit, the lowest surface roughness, and the best fatigue resistance. Furthermore, SLM Ti-6Al-4V clasps could be engaged into 0.50-mm undercuts.
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