Process parameter optimization for removable partial denture frameworks manufactured by selective laser melting

Abstract

Statement of problem: Selective laser melting (SLM), an additive manufacturing technology, is expected to replace the traditional lost-wax casting process used in producing removable partial denture (RPD) frameworks. However, studies comparing the accuracy of RPD frameworks and the effects of process parameters are lacking.

Purpose: The purpose of this in vitro study was to optimize SLM process parameters and use a quantitative analysis method to improve the accuracy of 3D-printed RPD frameworks.

Material and methods: The orientation and support structure of Kennedy Class II RPDs were designed in various ways by using 2 different software programs, CAMbridge and Magics. The optimum melt-pool parameters, including laser power, scan speed, hatch distance, and layer thickness, were determined empirically before manufacturing 12 RPD frameworks with 4 different process designs by using SLM (n=3). The accuracy of the RPD frameworks was determined by 3D scanning and comparing the 3D scan data with the original standard tessellation language (STL) RPD design with the best-fit algorithm of the Geomagic software program.

Results: Optimum melt-pool parameters were found with the function of density, surface roughness, and productivity (P=180 W, v=1200 mm/s, h=60 μm, t=30 μm). RPD frameworks fabricated by the optimized process parameters (167 ±105 μm) showed significantly better (P<.05) mean ±standard deviation accuracy than the 3 other groups of RPD frameworks manufactured by using the nonoptimized process parameters (180 ±121 μm to 222 ±136 μm). The best accuracy was found with the transverse orientation and interconnected support structure.

Conclusions: With the optimized design of process parameters, clinically acceptable RPD frameworks were produced. The accuracy of RPD frameworks fabricated by using SLM varied according to the design of the process parameters, indicating that SLM technology can replace the traditional lost-wax casting process.