Effects of photodynamic therapy on Streptococcus mutans and enamel remineralization of multifunctional TiO2-HAP composite nanomaterials

•Caries is a bacterial infection that causes demineralization of dental hard tissues.•TiO2-HAP can remove dental plaque and promote mineralization simultaneously.•TiO2-HAP nanocomposites showed higher ·OH formation ability and photodynamic effect than pure TiO2. As photosensitizer and photocatalyst, titanium dioxide (TiO2) can produce a photodynamic reaction for antibacterial treatment. This study aims to explore a Titanium dioxide/nano-hydroxyapatite (TiO2-HAP) composite combined with the dental curing lamp (385–515 nm) in clinical which could inhibit the dental plaque biofilm formed by Streptococcus mutans (S. mutans) and promote the enamel surface remineralization simultaneously. X-ray Diffraction (XRD) and high resolution transmission electron microscope (HRTEM) were used to detect the characterization of TiO2-HAP composite nanomaterials. Photodynamic properties of TiO2-HAP were detected by Diffuse reflectance spectrum (DRS) and fluorescence spectroscopy. Bacterial growth was measured by reading the absorbance of bacterial cultures and confocal microscope was used to observe the biofilm removal ability of nanomaterials. The ability of TiO2-HAP to promote enamel remineralization was measured by Scanning electron microscope (SEM). The OD 600 of S. mutans was 0.76 in the control group and 0.13 in group of TiO2-HAP with exposure to light-emitting diode (LED) (150 mW/cm2) for 5 min, suggesting its sustained antibacterial potency and inhibition of the metabolic activity of dental plaque microcosm biofilm. Also, the release of calcium and phosphorus ions in TiO2-HAP can promote enamel mineralization simultaneously. After 15 days of remineralization, the Ca/P ratio of demineralized enamel surface increased from 1.28 to 1.67, which was similar to that of normal enamel. The TiO2-HAP exhibit a promising anti-bacterial activity and remineralization capacity which can prevent the occurrence of caries to the greatest extent and promote the biomimetic mineralization of dental tissues.