Comparison of Antibacterial Activity of Disinfectant Solutions with Phosphoric Acid

Objectives: The deepest portion of the carious lesions have been shown to contain bacteria even after use of caries-disclosing dyes. The use of disinfectant solutions would be a possible solution to eliminate viable bacteria remaining in a cavity preparation. The purpose of this study was to compare the antibacterial activity of disinfectant solutions in different dilutions, with types of phosphoric acid combinations, and to determine their probable use as cavity disinfectants. Methods: The well diffusion test was performed according to NCCLS (National Committe for Clinical Laboratory Standards) criterias. The inoculum used was prepared using a standard S.mutans (Refik Saydam Hygiene Center No:676) isolate from a 24 hour culture. The disinfectant solutions; 2% chlorhexidine (Consepsis; Ultradent), 0.2% chlorhexidine (Klorhex;Drogsan), 5,25 % NaOCl, 3% H2O2, and their physiological saline serial dilutions (1/2, 1/4 and 1/8 of each), and 32% phosphoric acid (Uni-etch;Bisco), 32% phosphoric acid with benzalkonium chloride (BAC)(Ultra-etch;Bisco) were placed in the prepared wells in the seeded agar plates (n:10). After incubation for 24 hours, microbial inhibition zones were measured in mm. Data were analyzed with one-way ANOVA and Duncan’s test. Results: Phosphoric acid with and without BAC showed the highest inhibition zones whereas 0.2% chlorhexidine the lowest (p<0.05). Antibacterial activity of 3% H2O2 was superior than 5.25% NaOCl (p< 0.05). 2% chlorhexidine had the same antibacterial property as 5.25% NaOCl (p>0.05). The antibacterial activity of the disinfectant solutions decreased significantly with the increasement of their dilutions (p<0.05). Conclusions: All of the tested disinfectant solutions showed antibacterial activity against S.mutans however their use as cavity disinfectants would be not necessary when a phosphoric acid etchant was used.