Impact of food-simulating liquids on the surface degradation of conventional, CAD/CAM-milled, and 3D-printed denture base materials

Background Digital technologies have introduced CAD/CAM-milled and 3D-printed denture base materials as alternatives to conventional polymethyl methacrylate (PMMA). However, evidence on their surface degradation under simulated oral conditions remains limited. This study evaluated the effect of food-simulating liquids on surface degradation of heat-cured PMMA, CAD/CAM-milled, and 3D-printed denture base resins over time. Methods A total of 225 specimens (10 × 10 × 2 mm) were fabricated from three denture base materials (75 per material): heat-cured PMMA (HC), Ivotion Base CAD/CAM-milled PMMA (IB), and SprintRay Apex Base 3D-printed resin (SR). Fifteen specimens per material were allocated to five testing conditions (n = 15): control (air; AR), distilled water (DW), ethanol solution (ES), citric acid (CA), and heptane (HE). Specimens were evaluated after 1 week (T1) and 1 month (T2). Surface roughness (Ra, µm) was measured using a profilometer, and hardness (VHN) was assessed by Vickers hardness testing. Data were analysed using two-way ANOVA, one-way ANOVA with Tukey’s post hoc test, and paired-samples t-test (p < 0.05). Results SR demonstrated the lowest surface roughness (T1: 0.099–0.105; T2: 0.096–0.121), whereas IB generally exhibited the highest values, particularly in CA (T1: 0.237 ± 0.043; T2: 0.241 ± 0.038). At T2, DW and CA significantly increased roughness of HC (up to 0.232 ± 0.030 in DW) (p < 0.05). For hardness, HC showed the highest values overall, especially in HE (T1: 20.32 ± 0.94; T2: 20.66 ± 0.31), while IB demonstrated lower hardness, particularly in ES at T2 (10.97 ± 0.39). ES markedly reduced hardness of SR. HE produced no significant changes over time. Conclusions Surface degradation was material- and medium-dependent. The 3D-printed resin exhibited superior smoothness, whereas conventional PMMA showed greater hardness. Acidic and alcoholic environments adversely affected surface properties, highlighting the importance of material selection according to patients’ diet.