Antimicrobial efficacy of hypochlorite-based gels for disinfecting heat-polymerized and 3D printed denture bases

Denture biofilm control remains a clinical challenge, especially for individuals with reduced dexterity. Conventional chemical protocols are complex and prone to dosing errors that compromise daily hygiene.

The purpose of this in vitro study was to formulate and characterize sodium hypochlorite (NaOCl) and calcium hypochlorite (Ca(OCl)₂) gels and evaluated their antimicrobial efficacy against biofilms formed on heat-polymerized (HP-PMMA) and 3-dimensionally (3D) printed polymethyl methacrylate (3D-PMMA).

Minimum inhibitory concentration assays were used to define the effective concentration for gel formulation. Experimental gels (0.5% NaOCl or Ca(OCl)₂) were prepared with hydroxyethyl cellulose and characterized for organoleptic (color, odor, turbidity, phase separation) and physicochemical properties (density, pH, consistency) after 1 and 6 months. Biofilms of Candida albicans, C. glabrata, C. tropicalis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were grown on HP-PMMA and 3D-PMMA specimens (n=15). Four disinfection protocols were tested: control, brushing with gel, brushing plus residual gel contact, and immersion. Antimicrobial activity was assessed by colony-forming unit (CFU) counts and scanning electron microscopy (SEM). Data were analyzed using Kruskal-Wallis with Bonferroni post hoc tests, t tests, and Mann-Whitney U tests (α=.05).

MIC assays supported the 0.5% concentration for both hypochlorites. All gels remained organoleptically stable and maintained alkaline pH after 6 months. The Ca(OCl)₂ gel exhibited greater consistency and lower density than NaOCl. The brushing plus residual exposure protocol eliminated all microorganisms on both substrates (0.00 ±0.00 CFU/mL; P<.001). Ca(OCl)₂ generally outperformed NaOCl, and 3D-PMMA showed lower microbial retention than HP-PMMA in several conditions. SEM confirmed minimal biofilm coverage after residual-exposure protocols.

Hypochlorite-based gels provided effective antimicrobial action against fungal and bacterial biofilms on denture base resins. The brushing plus residual contact protocol was the most effective method. Ca(OCl)₂ gel and 3D-PMMA showed superior performance, supporting their potential for simplified and clinically applicable denture hygiene strategies.