DETERMINATION OF THE IN SITU BACTERICIDAL ACTIVITY OF AN ESSENTIAL OIL MOUTHRINSE USING A VITAL STAIN METHOD¹

Objective
To determine the bactericidal effects of Listerine® Antiseptic on dental plaque bacteria in situ.

Methods
In this crossover study of 17 subjects, 1—day—old plaque was sampled at baseline from the buccal surfaces of diagonally contralateral maxillary and mandibular bicuspids and first molars. Subjects were randomly assigned to either LISTERINE^® Antiseptic or a sterile saline negative control and rinsed under supervision with 20 mL for 30 seconds. Plaque was sampled 30 minutes later from the remaining contralateral posterior teeth.

Following a washout period of 7 days, subjects repeated these procedures with their respective alternate rinse. Plaque samples were stained and analyzed with computerized image analysis.

Results
LISTERINE^® Antiseptic displayed statistically significant bactericidal effects against bacteria within the plaque biofilm. At 30 minutes, LISTERINE^® Antiseptic killed 78.7% of bacteria compared to 27.9% with the control rinse (p< 0.001). These data confirm the findings of previous in vitro and in vivo studies that demonstrated the significant biocidal activity of LISTERINE^® Antiseptic.

Conclusions
In summary, this study has demonstrated that rinsing with the essential oil mouthrinse has significant bactericidal activity against supragingival plaque bacteria in situ. The results of this study confirm the findings of previous in vitro and in vivo studies which demonstrated this mouthrinse formulation to have significant microbiaocidal activity against oral microorganisms. They are of particular interest in the context of our current understanding of the nature of biofilms insofar as they demonstrate the ability of the mouthrinse formulation to penetrate the plaque biofilm and exert a bactericidal activity on the organisms contained therein.