Effects of additive manufacturing technology and build angle on surface characteristics and microbial adhesion of 3D-printed dental zirconia: a laboratory study.

BACKGROUND: Microbial colonization on 3D-printed zirconia restorations may aggravate plaque accumulation and periodontal inflammation. While additive manufacturing (AM) parameters significantly influence surface roughness and morphology, evidence regarding their impact on bacterial adhesion remains unclear. This study investigated the effects of AM technologies and build angles on the surface characteristics and initial microbial adhesion of 3D-printed zirconia. METHODS: Zirconia discs were fabricated using material jetting (MJ, 10 μm layer thickness) and digital light processing (DLP, 30 μm layer thickness) technologies with three build angles (0°, 45°, and 90°), respectively (n = 25 per group). The surface topographic features and roughness were analyzed using scanning electron microscopy and laser scanning microscopy, respectively. The surface wettability was evaluated via water contact angle measurements. Streptococcus gordonii (S. gordonii) was used to assess bacterial adhesion, which was evaluated via colony-forming unit counts and visualized through SEM imaging. Statistical analysis involved two-way ANOVA and post hoc Tukey tests, with significance threshold set at p < 0.05. RESULTS: AM technologies and build angle significantly affected surface characteristics, with significant interactions observed for roughness (p < 0.05). DLP-45° showed the roughest surface, while DLP-0° was the smoothest. Water contact angle varied significantly with both factors (p < 0.05), with MJ-45° showing the highest wettability. For S. gordonii adhesion, a significant interaction between AM methods and build angle was found (p < 0.05), and AM methods showed a main effect (p = 0.0104), while build angle alone was not significant (p = 0.0642). The least adhesion occurred in MJ-45° and DLP-0°, with no consistent correlation between roughness and bacterial adhesion. CONCLUSIONS: AM technologies and build angle affected S. gordonii adhesion to zirconia surfaces. DLP printing at 0° and MJ printing at 45° were associated with significantly reduced bacterial counts, presenting a clinically approach to minimize initial plaque formation and support the long-term periodontal success of 3D-printed zirconia restorations.