<i>In vitro</i> evaluation of microbial test culture adhesion on the surface of denture base materials coated with denture adhesives

Background: Effectiveness of removable dentures is closely linked to reliable intraoral retention. Their clinical success largely depends on the low adhesion capacity of oral microbiota, which represent a constant component of the oral environment. Evaluation of microbial adhesion to denture base materials coated with adhesive creams may serve as a parameter for selecting the most appropriate fixation agent. Aim: To assess in vitro the adhesion of microbial test cultures to the surface of denture base materials coated with various denture adhesives. Methods: An open-label, randomized experimental study was conducted using specimens of two denture base materials: heat-polymerized polymethyl methacrylate (PMMA) and a photopolymer resin intended for additive manufacturing of removable denture bases. Samples were fabricated as discs measuring 5 mm in diameter and 0.5 mm in thickness, each coated with a denture adhesive. For microbial assessment, reference strains of five of the most commonly isolated oral microorganisms were cultured: Escherichia coli, Staphylococcus aureus, Candida albicans, Streptococcus mutans, and Porphyromonas gingivalis. Residual adhesion index was calculated for each strain. Between-group comparisons were performed using the Mann–Whitney U test. Statistical significance was set at p ≤0.05, with values reported to the third decimal place. Results: An evaluation of the primary adhesion of reference strains of microorganisms most commonly colonizing the oral mucosa revealed that denture adhesive formulations such as Corega (Haleon, UK) exhibited statistically significantly lower residual adhesion compared with President (Betafarma S.p.A., Italy), Whiteberg (Anhui Greenland Biotech Co., China), and SPLAT CONFIDent FIX (BetaPharm, Italy). Conclusion: Residual adhesion indices were detected in all tested microbial strains and showed minimal differences between the two denture base materials — PMMA and 3D-printed photopolymer. S. aureus, S. mutans, and P. gingivalis demonstrated high adhesive potential, while E. coli and C. albicans exhibited significantly lower adhesion levels. One of the critical factors in the successful use of removable dentures is their hygienic status, which depends on the low adhesion potential of microorganisms. This, in turn, significantly influences the condition of the oral mucosa and the stability of the oral microbiome. Lower microbial adhesion was observed with Corega Max Hold + Comfort and Corega Gum Protection (Haleon, UK). Components of these adhesives may inhibit primary microbial adhesion and contribute to the maintenance of colonization resistance of the oral mucosa.