Objective: Four common antimicrobial agents were evaluated for their efficacy in reduction of aerobic bacteria intraorally grown in biofilms on rough titanium samples. The solutions investigated contained chlorhexidine, essential oil, octenidine, or citric acid. Method and Materials: Twenty volunteers wore splints with titanium sleeves intraorally for 10 days. Following irrigation with the antiseptics, the sleeves were removed and biofilm samples were taken by swabbing. The bacteria were first examined microscopically by Gram staining. These samples from the surfaces were then cultured under aerobic conditions to identify and quantify the colonizing bacteria. Results: Compared to untreated controls, significant (P .05) differences in antimicrobial efficacy were observed for the different regimens depending on bacterial species or even the subtype. The reduction rates achieved varied from 30.0% after 2 minutes of rinsing with chlorhexidine to 99.8% after 8 minutes of rinsing with octenidine. Conclusion: The irrigation regimens studied in this investigation reduced bacterial colonization in a mature biofilm grown intraorally on rough titanium surfaces. The highest absolute reduction was achieved after 8 minutes, but only the 2-minute reduction rates are significant for clinical practice. Taking this into consideration, the distinct decontamination efficacy of octenidine and citric acid is evident.