Influence of salivary pH on the surface, mechanical, physical, and cytotoxic properties of resins for 3D-printed and heat-polymerized denture base.

OBJECTIVE: To evaluate the effects of salivary pH on the mechanical, surface, physical, and cytotoxic properties of denture base resins (heat-polymerized and 3D-printed). METHODS: Discs (10 x 3 mm) and bars (64 x 10 x 3.3 +/- 0.2 mm) were fabricated from heat-polymerized (CT) and 3D-printed (3D) denture base resins. The sample were stored for three months in distilled water and artificial saliva with acidic (pH 5.0), neutral (pH 7.0), and basic (pH 8.0) conditions. After the storage period, samples underwent surface, mechanical, and physical characterization, as well as cytotoxicity evaluation. A two-way analysis of variance (ANOVA) was conducted to compare the surface and mechanical properties of denture base resins at different salivary pH levels. The Kruskal‒Wallis test was applied for multiple comparisons, while the Mann-Whitney U test (p < 0.05) was used for paired comparisons of cytotoxicity and physical properties. RESULTS: An acidic salivary pH increased the surface roughness and hydrophilicity of the 3D resin while reducing its hardness, and flexural resistance (p < 0.05). In contrast, a basic salivary pH increased the surface roughness and hardness of the CT resin while decreasing its hydrophilicity (p < 0.05); however, the flexural strength decreased as the salivary pH increased (p > 0.05). Water absorption was higher in the 3D resin compared to the CT resin. Additionally, cell viability decreased over time when the CT and 3D resins were stored in basic and neutral salivary pH, respectively. CONCLUSION: Given the negative impact of acidic and basic salivary pH on the evaluated properties of 3D-printed and heat-polymerized resins, 3D-printed resin may be a suitable denture base material for patients with basic and neutral salivary pH, whereas heat-polymerized resin may be appropriate for those with acidic salivary pH. CLINICAL SIGNIFICANCE: The selection of denture base resin should be preceded by an assessment of the patient's salivary pH to identify the material that undergoes the least change in its properties.