Comparison of the Effectiveness of three Mouthwashes on Oral microflora: an in vitro study Dr. B. Houshmand* - Dr. R. Yousefi** - Dr. Z. Khamverdi*** *- Assistant Professor of Periodontics Dept. - Faculty of Dentistry – Hamedan University of Medical Sciences. **- Associate Professor of Microbiology Dept. Faculty of Medicine – Hamedan University of Medical Sciences. *** - Assistant Professor of Operative Dentistry Dept. Faculty of Dentistry – Hamedan University of Medical Sciences. Background and Aim: The use of mouthwashes for plaque control and preventing its accumulation on teeth and adjacent mucous membranes is of considerable importance. The aim of this investigation was to compare the effectiveness of chlorhexidine and two Irsha mouthwashes, on aerobic microorganisms in oral flora. Materials and Methods: In this in vitro study, the diffuse-agar method was used to effects of antiplaque–antitartar Irsha mouthwash, antiseptic Irsha mouthwash and 0.2% chlorhexidine on oral aerobic microorganisms. The microorganisms were dispersed and plated on blood agar or Muller Hintone medium. Six-millimeter paper disks immersed in each of the study solutions were inserted into the plates after the incubation period. This procedure was repeated 4 times for each of the microorganisms and the inhibition zones were measured for each microorganism and mouthwash, separately. The data were analyzed using ANOVA and Tukey HSD (post hoc) tests. Results: Antiplaque Irsha was useful in controlling some of the analyzed microorganisms including lactobacilli, Neisseria sicca, C. diphtheroid, Streptococcus salivarius, Streptococcus viridans and Streptococcus mutans, in decreasing order. Antiseptic Irsha did not affect the aerobic bacteria. Chlorhexidine was effective on all complex infections consisting of the studied aerobic microorganisms, especially lactobacilli and Staphylococcus epidermidis. It also successfully controlled Staphylococcus aureus followed by Brevudimonas, Neisseria sicca, Streptococcus salivarius, Streptococcus mutans, Pseudomonas aeruginosa and Streptococcus viridans, in that order. Conclusion: According to these results, 0.2% Chlorhexidine demonstrated a superior antimicrobial effect in most cases as compared to the studied mouthwashes. Key words: Chlorhexidine – Irsha – Mouthwash – Plaque - Oral microorganism | 
