Evaluation of CAD-CAM methods for fabrication of removable partial denture frameworks from commercially pure titanium

Commercially pure titanium (CP-Ti) is ideal for removable partial denture (RPD) frameworks owing to its biocompatibility and corrosion resistance; however, conventional casting can introduce defects and dimensional errors. This study compared the shape accuracy, surface roughness, microstructure, and internal pores of CP-Ti RPD frameworks prepared using four CAD-CAM fabrication methods: (1) Ti-resin: casting from a three-dimensional (3D)-printed resin pattern; (2) Ti-wax: casting from a milled wax pattern; (3) Ti-milling: direct milling from a CP-Ti disc; and (4) Ti-SLM: selective laser melting.

Forty frameworks were prepared for each group (N = 10). Shape accuracy was assessed using 3D data-inspection software, surface roughness was analyzed using laser microscopy, the microstructure was determined using X-ray diffraction, and internal pores were examined using micro-computed tomography. Nonparametric statistics (Kruskal-Wallis and Steel-Dwass tests) were used (P < 0.05).

Ti-SLM achieved the highest trueness (median: 0.00 mm; IQR: 0.09 mm) and precision (median: 0.01 mm; IQR: 0.02 mm), while Ti-milling yielded the lowest surface roughness (median arithmetic mean height: 0.61 µm; IQR: 0.05 µm). Internal pores were absent in Ti-milling and minimal in Ti-SLM (0-1), whereas Ti-resin and Ti-wax produced 319 and 171 pores (median), respectively. Significant inter-method differences were found in shape accuracy, surface roughness, and pore counts (P < 0.05).

The fabrication method affected the dimensional accuracy, surface conditions, crystalline features, and internal pores of the CP-Ti frameworks. Ti-milling and Ti-SLM outperformed the casting-based methods (Ti-resin and Ti-wax) in terms of accuracy and defect reduction. These digital approaches may improve the reproducibility and precision of clinical fabrication of CP-Ti RPD frameworks.