Photocatalytic Effects of Acrylic Resins Incorporated with Nano-titanium Dioxide on Planktonic and Biofilm Growth of Four Cariogenic Bacteria

Abstract

Aims: The activities of cariogenic bacteria in biofilm on acrylic baseplates of removable orthodontic appliances and partial denture contribute to dental caries, inflammation of gingiva and periodontal disease. This in vitro study evaluates the photocatalytic antimicrobial activity of acrylic specimens (AS) containing NanoTiO2 under ultraviolet type A (UVA) illumination against four cariogenic bacteria. Study Design: An in vitro study Place and Duration of Study: Department of Microbiology and Department of Orthodontics, Tehran University of Medical Sciences (TUMS); Department of Chemistry, Tarbiat Modares University, between June 2011 and March 2012. Methodology: Chemical-cure acrylic resins, Polymethylmethacrylates (PMMAs), were used to synthesize acrylic specimens containing NanoTiO2 (NanoT-AS). Antibacterial activity of NanoT-AS were assessed against Streptococcus sobrinus, Streptococcus mutans, Lactobacillus acidophilus as well as Lactobacillus casei and co-cultures of the four species by adherence inhibition as well as planktonic and biofilm bacterial cells growth inhibition on NanoT-AS under UVA illumination (NanoTiO2+/UVA+). Results: Exposure to NanoTiO2+/UVA+ reduced bacterial adherence by 43.8-96.5% depending on the microorganism type. NanoTiO2+/UVA+ showed 1.7-6.0 log decrease planktonic cultures in time-dependent manner over a 4h period (P<0.05). NanoT-AS inhibited significantly biofilm formation of all test bacteria and co-cultures by 44.2-93.1%, compared to unmodified PMMA (control) under UVA illumination. Some inhibitory activity of NanoTiO2+/UVA+ could be maintained even after the third generation of biofilm growth. Conclusion: The data presented here are novel in that they prove that NanoTiO2+/UVA+ effectively inhibited adherence of cariogenic bacteria to NanoT-AS surfaces as well as strong antimicrobial activity in the planktonic phase and subsequent biofilm formation. This data shows NanoTiO2+/UVA+ has the potential to minimize cariogenic microorganism’s adherence and colonization on acrylic specimens and this novel acrylic resin formulation could be developed as a denture and orthodontic appliances base.