Antibacterial dental adhesive resins containing nitrogen -doped titanium dioxide nanoparticles

The development of dental adhesive resins with long-lasting antibacterial properties is a possible solution to overcome the problem of secondary caries in modern adhesive dentistry. Objectives: (1) Synthesis and characterization of nitrogen-doped titanium dioxide nanoparticles (N_TiO2), (ii) topographical, compositional and wettability characterization of thin-films (unaltered and experimental) and, (iii) antibacterial efficacy of N_TiO2-containing dental adhesives against Streptococcus mutans biofilms. Materials and methods: Nanoparticles were synthesized and characterized using different techniques. Specimens (diameter = 12mm, thickness congruent to 15 mu m) of OptiBond Solo Plus (Kerr Corp., USA) and experimental adhesives [50, 67 and 80% (v/v)) were fabricated, photopolymerized (1000 mW/cm(2), 1 min) and UV-sterilized (254 rum, 800,000 mu J/cm(2)) for microscopy, spectroscopy, wettability and antibacterial testing. Wettability was assessed with a contact angle goniometer by dispensing water droplets (2 mu L) onto four random locations of each specimen (16 drops/group). Drop profiles were recorded (I min, 25 frames/s, 37 degrees C) and contact angles were calculated at time = 0 s (theta(INITIAL)) and time = 59 s (theta(FINAL)). Antibacterial testing was performed by growing S. =tans (UA159-ldh, JM10) biofilms for either 3 or 24 h (anaerobic conditions, 37 degrees C) with or without continuous light irradiation (410 +/- 113 nm, 3 h = 38.75 J/cm(2), 24 h = 310.07 J/cm(2)) against the surfaces of sterile specimens. Results: N_TiO2 was successfully prepared using solvothermal methods. Doped-nanoparticles displayed higher light absorption levels when compared to undoped titania. Experimental adhesives demonstrated superior antibacterial efficacy in dark conditions, Conclusions: The findings presented herein suggest that N_TiO2 is a feasible antibacterial agent against cariogenic biofilms.