Impact of photodynamic therapy based on modified orthodontic self-cured acrylic resin containing titanium dioxide nanoparticles against Candida albicans

Abstract

Background: This in vitro study was conducted to evaluate the impact of photodynamic therapy (PDT) using modified acrylic resin with titanium dioxide nanoparticles (TiO₂NPs) on Candida albicans biofilm, physico-mechanical properties, and pro-inflammatory gene expression.

Materials and methods: The biofilm inhibition test was used to assess the antimicrobial effectiveness against C. albicans biofilm. The levels of gene expression for TNF-α and IL-6 in human gingival fibroblast (HGF) cell line were examined using quantitative real-time polymerase chain reaction (qRT-PCR). The roughness, flexural strength, and microhardness of modified acrylic resin with different concentrations of TiO₂NPs (0 %, 1 %, 2 %, and 3 %) were measured using a profilometer, a universal testing machine, and a digital hardness tester, respectively.

Results: The C. albicans biofilm was most effectively reduced by 0.2 % chlorhexidine (CHX), showing the lowest colony count (5.94 ± 0.46 × 10⁶ CFU/mL). Comparable results were observed with 3 % TiO₂NPs-PDT (7.37 ± 1.34 × 10⁶ CFU/mL, P = 0.300). The colony counts from 2 % TiO₂NPs-PDT (9.21 ± 1.25 × 10⁶ CFU/mL) was not significantly different from 3 % TiO₂NPs-PDT (P = 0.529) but was notably higher than that of 0.2 % CHX (P = 0.004). The expression of TNF-α and IL-6 genes decreased significantly in HGF cell line when exposed to 2 % and 3 % TiO₂NPs-PDT. Microhardness and flexural strength demonstrated a direct correlation with the concentration of TiO₂NPs, while roughness showed an inverse correlation. Additionally, all groups exceeded the ISO standards for flexural strength.

Conclusion: 3 % TiO₂NPs-PDT reduced C. albicans biofilm and downregulated the pro-inflammatory gene expression without adversely affecting the properties of the acrylic resin, making it suitable for clinical use.

Keywords: Acrylic resin; Candida albicans; Flexural strength; Gene expression; Photodynamic therapy; Titanium dioxide.