The effect of detergents on the antibacterial activity of disinfecting solutions in dentin

Detergents have been added into different disinfecting solutions to lower their surface tension and to enhance their antibacterial effects. The purpose of this study was to evaluate the effectiveness of dentin disinfection by different antibacterial solutions in the presence and absence of detergents using a novel dentin infection model and confocal laser scanning microscopy (CLSM).

Semicylindrical dentin specimens were infected with Enterococcus faecalis by centrifugation according to a previously described protocol. After 1 day of incubation, the infected dentin specimens were subjected to 1 and 3 minutes of exposure to sterile water, 0.1% cetrimide (CTR), 2% sodium hypochlorite (NaOCl), 2% NaOCl + 0.1% CTR, 6% NaOCl, 6% NaOCl + 0.1% CTR, Chlor-Xtra (Vista Dental, Racine, WI), 2% chlorhexidine (CHX), CHX-Plus (Vista Dental, Racine, WI), 2/4% iodine potassium iodide (IPI), and IPI + 0.1% CTR. The specimens were then stained for bacterial viability and examined by CLSM to analyze the proportions of dead and live bacteria inside dentinal tubules.

More bacteria in dentin were killed after 3 minutes of exposure than after 1 minute of exposure to the disinfecting solutions in all experimental groups (P < .05). The antibacterial solutions with detergents (0.1% CTR, 2% NaOCl + 0.1% CTR, CHX-Plus, and IPI + 0.1% CTR) showed a statistically higher proportion of dead bacteria than the corresponding solutions without detergents (sterile water, 2% NaOCl, 2% CHX, and IPI) (P < .05) except for the 6% NaOCl group (6% NaOCl, 6% NaOCl + 0.1% CTR, and Chlor-Xtra) (P > .05). Six percent NaOCl, 6% NaOCl + 0.1% CTR, and Chlor-Xtra were the most effective solutions, killing over 45% and 65% of the bacteria after 1 and 3 minutes of exposure, respectively. Only 3% to 4% of the bacteria were dead in the sterile water group, whereas 0.1% CTR alone was able to kill 24% to 36% of the E. faecalis cells.

The addition of detergents in the disinfecting solutions used in the present study increased their antibacterial effects against E. faecalis in the dentinal tubules. When used alone as a single agent, CTR showed antibacterial effectiveness comparable to 2% NaOCl, 2% CHX, and 2/4% IPI.