An in vivo comparison of the antimicrobial activities of four commercial mouthwashes

The purpose of this in vivo double-blind study was to determine and compare the antimicrobial effectiveness of four commercial over-the-counter mouthwashes and a water control. Two of the products tested contained alcohol (Listerine® and Scope®) and two products were alcohol-free (Rembrandt® Mouth Refreshing Rinse and Clear Choice®). The antimicrobial efficacy of the products was determined against aerobic, microaerophilic, and anaerobic bacteria in saliva. Thirty human subjects participated in the study. At each experimental session for a given subject, a pretest saliva sample was taken. This sample was divided and used to grow three bacteria cultures under the different incubation environments. After giving the pretest sample, the subject rinsed with one of the commercial mouthwashes or the water control for 30 seconds, then waited one hour at which time a posttest saliva sample was collected. Again, the sample was divided and used to culture the different type of bacteria. Following a 48-hour incubation period, the numbers of microbial colonies on each plate were counted and compared. The results indicated that all of the mouthwashes tested performed significantly better than the water control. Both of the non-alcohol-containing products showed efficacy in inhibiting aerobic, microaerophilic, and anaerobic bacteria. Rembrandt Mouth Refreshing Rinse and Listerine inhibited all three types of bacteria, and were not significantly different from each other in efficacy. The Rembrandt mouthwash inhibited all three types of bacteria more effectively than Clear Choice mouthwash, and inhibited two of the three types of bacteria more effectively than Scope mouthwash.