Background: This study aimed to evaluate the reduction of halitosis when using antimicrobial photodynamic therapy (aPDT) with Bixa orellana extract and blue light-emitting diode (LED). Methods: Forty-four UNINOVE students or employees with a diagnosis of sulfide (H2S) >= 112 ppb in gas chromatography were selected. The patients were randomly divided in groups: Group 1 (n = 15): aPDT with annatto and LED; Group 2 (n = 14): tongue scraping; Group 3 (n = 15): tongue scraping and aPDT. For aPDT, a wasBixa orellana extract used in a concentration of 20 % w/v (Formula e Acao (R), Sao Paulo, Brazil) on the tongue for 2 min, associated with a blue-violet LED (Valo Cordless Ultradent (R) Products, Inc., South Jordan, UT, USA) (395 - 480 nm). Six points were irradiated on the back of the tongue, at wavelength 395 - 480 nm for 20 s, energy of 9.6 J and radiant energy of 6.37 J/cm(2) per point. The results were compared before, immediately after treatment and 7 days after. The Friedman test was used for the intragroup analysis and the Kruskal Wallis test for the intergroup analysis. Results: In all groups, there was a difference between baseline and the value immediately after the treatment. In Groups 1 and 3, there was no difference between the baseline and the 7 days control. Conclusion: There was an immediate reduction of halitosis, but the reduction was not maintained after 7days.
