Impact of Printing Orientation on the Surface Properties and Microbial Biofilm Formation of 3D-Printed Denture Resins

This study aimed to characterize the adhesion and biofilm formation of key denture-associated microbes-Candida albicans, Porphyromonas gingivalis, and Streptococcus mutans-on a 3D-printed photopolymer resin (FotoDent®).

Discs were fabricated at three distinct printing orientations (0°, 45°, and 90°) to assess the impact of layer deposition on surface properties and microbial colonization. Conventionally polymerized ProBase® cold resin discs served as controls. All specimens underwent comprehensive surface characterization, including measurement of areal surface roughness, static contact angle with polar and apolar liquids, and surface free energy components. Adherent microbial cells were quantified using species-specific quantitative real-time PCR (qPCR) following standardized biofilm assays.

Microbial adhesion to the 3D-printed resin was highly dependent on print orientation, with cell counts for all three species decreasing significantly (p<0.05) from the 0° to the 90° orientation. This trend was paralleled by an increase in surface roughness (Ra) with higher print angles. A strong, statistically significant positive correlation was observed between the surface roughness of FotoDent® discs and biofilm cell numbers for C. albicans (r=0.815), P. gingivalis (r=0.883), and S. mutans (r=0.903). In contrast, adhesion to the control ProBase® material was consistently higher and showed no significant correlation with any measured surface characteristic-roughness, wettability, or surface energy.

These findings indicate that for 3D-printed dental resins, printing parameters, especially orientation, critically determine the final surface topography, which in turn is a affects microbial adhesion and biofilm formation.