Antifungal Effect of Alum Solution as a Natural Disinfectant and Its Impact on Surface Properties of 3D-Printed Denture Base Resin

Objectives: Disinfection of 3D-printed acrylic resin is essential to reduce fungal colonization and improve the clinical performance of dentures. This in vitro study assessed the antifungal activity of aluminum potassium sulfate (alum) solutions against Candida albicans in 3D-printed acrylic resin at different concentrations, while also illustrating their effects on the material’s surface roughness and wettability. Materials and methods: The study included 120 specimens prepared from 3D-printed acrylic resin and then randomly assigned to four groups: distilled water as the negative control, a CHX 2% as the positive control, and two concentrations (10% and 15%) of alum solution. A total of 40 specimens were used for each of the three tests, with 10 specimens per group. An additional 16 specimens were fabricated for microstructural characterization, with 3 specimens per group for SEM and 1 specimen per group for AFM, bringing the total number of specimens to 136. The antifungal activity against Candida albicans was evaluated using a colony-forming unit (CFU) method. Surface roughness was evaluated utilizing a profilometer, while wettability was assessed by a contact angle goniometer. Before surface roughness, wettability, SEM, and AFM testing, the specimens in the alum (10% and 15%) and 2% chlorhexidine (CHX) groups were immersed for 5 min per cycle, completing 90 immersion cycles over 10 days to simulate approximately 3 months of clinical denture use. In contrast, the specimens used for the colony-forming unit (CFU) test against Candida albicans were immersed only once for 5 min. The negative control specimens were not subjected to any disinfection. Statistical assessments were conducted out by employing one-way ANOVA with Games–Howell post hoc for CFU, as well as one-way ANOVA with Bonferroni post hoc were chosen for wettability and roughness data. In all statistical assessments, the significance was determined at p < 0.05. Results: Number of CFU of Candida albicans was significantly reduced (p < 0.0001) in all tested groups relative to the negative control group, along with a significant rise in surface roughness. Chlorhexidine revealed higher wettability (decreased contact angle), though no significant change was found between either the 10% or 15% alum groups and the negative control (p > 0.05). Conclusions: Alum solutions at concentrations of 10% and 15% for 5 min revealed antifungal activity against Candida albicans in 3D-printed acrylic denture base resin. There was no statistical change in wettability for any concentration compared to the negative control, while surface roughness increased after treatment.