Streptococcus mutans is one of the more significant pathogens involved in the development of dental caries in humans. The purpose of this research was to design a TiO 2 -coated dental instrument and to determine the bactericidal effects of the instrument on S. mutants . TiO 2 photocatalytic films were prepared by the low-pressure metal-organic chemical vapor deposition (LPMOCVD) method using titanium tetraisopropoxide (TTIP) as precursor. The photocatalytic reaction was carried out on a TiO 2 -coated pyrex petri dish with an ultraviolet (UV) light emitting diode (LED) illuminator or a fluorescent lamp light source. Our data indicates that the relative survival ratio of S. mutans when plated onto TiO 2 photocatalytic films and under exposure to UV-A light for 15 min was 0.01%. In addition, a fluorescent lamp light source also had bactericidal effects on the S. mutans plated TiO 2 photocatalytic films. These results indicate that TiO 2 -coated dental materials or devices may be useful in dental treatments for the prevention of carious or enamel demineralization.