Aims: Investigate the potential of curcumin, hypericin and photogem as antimicrobial agents in the antimicrobial photodynamic therapy (APDT) in Streptococcus mutans planktonic cultures. Methods and Results: Susceptibility of S. mutans (ATCC 25175) to APDT using three concentrations of curcumin (250, 750 and 1000 mg l-1), hypericin (1, 5 and 10 mg l-1) and photogem (1, 5 and 10 mg l-1) was examined by colony-forming units method. Separated specimens of each group were irradiated using specific wavelengths (450 ± 10 nm, 590 ± 10 nm and 630 ± 10 nm). Results demonstrate absence of antibacterial effects for the groups that didn't have the association of light with photosensitizers. Antibacterial effects were observed in the groups using photogem and hypericin. When compared with the positive control, the observed reductions were in the order of 6-logs up to the eradication of the treated cells. It is possible to co-relate the increase of photosensitizer concentration and irradiation time with higher antibacterial effect. Conclusions: APDT have potential to be used as an oral disinfectant method. Significance and Impact of the Study: APDT can be used prior to the execution of any oral treatment to decrease the dentist and staff exposure to a big bacterial load during the subsequent treatments and to lower the potential of environmental cross-contamination.