Biofilm Formation on Denture Base Resin Including TiO₂, ZnO and MgO Nanoparticles

Objectives: To investigate whether the addition of TiO₂, ZnO and MgO nanoparticles into PMMA denture base resin reduces biofilm formation on its surface.
Methods: Standardized specimens were prepared from an auto-curing acrylic denture base resin (Palapress vario, Heraeus Kulzer) and polished to high gloss using silicon carbide grinding paper. Uncured resin mixtures were supplemented with either 0.1, 0.2, 0.4, or 0.8 wt% nanoscaled TiO₂, ZnO, or MgO; conventional acrylic resin was used for reference. Surface roughness and surface free energy were determined. Biofilm formation was initiated by incubating the specimens with whole saliva for 2 h at 37°C and subsequent incubation with Candida albicans ATCC 10231 or a suspension of Candida albicans ATCC 10231, Actinomyces naeslundii T14V and Streptococcus gordonii DL1 for 2.5 h. Microbial proliferation was simulated for 20 h and 44 h. Relative viable biomass was analyzed using a MTT-based approach. Means and standard deviations were calculated; statistical analysis was performed as a function of resin modification and biofilm formation time using two-way ANOVA guided by post-hoc analysis where appropriate.
Results: For single-species biofilms, significantly lower relative viable biomass was identified after 44 h than after 20 h of biofilm formation (P=.014), whereas for multi species biofilms, relative viable biomass was significantly higher after 44 h than after 20 h of biofilm formation (P<.001). Although significant differences in biofilm formation were identified on specimens produced from the different modified denture base acrylic resins, no significant impact of the addition of TiO₂, ZnO and MgO nanoparticles was identified for both mono- and multi-species biofilm formation in comparison to unmodified acrylic resin (P>.05).
Conclusions: Within the limitations of a laboratory study, the results suggest that the addition of TiO₂, ZnO and MgO nanoparticles into acrylic denture base resin does not have a favourable effect on biofilm formation.