Effect of an essential oil-containing antiseptic mouthrinse on plaque and salivary Streptococcus mutans levels

Background: Clinical studies in which antimicrobial mouthrinses were shown to have significant antiplaque activity most frequently have used gingiviti s as the clinically relevant endpoint. However, there is evidence to sugges t that mouthrinses containing active agents effective against Streptococcus mutans, such as chlorhexidine, may also have a role in inhibiting dental c aries. This clinical study was conducted to determine the effect of 2x-dail y rinsing with an essential oil-containing antiseptic mouthrinse (Listerine (R) Antiseptic) on levels of recoverable S. mutans and total streptococci i n supragingival interproximal plaque and in saliva. Additionally, a follow- up in vitro study is reported which determined whether a differential susce ptibility to the antiseptic mouthrinse exists among different strains of st reptococci. Method: Following baseline saliva and plaque sampling for quantification of recoverable S. mutans and total streptococci, 29 qualifying subjects were randomly assigned either the essential oil mouthrinse or a sterile water co ntrol. They rinsed with 20 ml for 30 s 2xdaily for 11 days and once on the 12th day, in addition to their usual oral hygiene procedures. On day 12, sa liva and plaque samples were again collected and microbiological quantifica tion performed. The procedures were repeated with the alternate rinse after a I-week washout period. Results: The essential oil mouthrinse produced respective reductions of 69. 9% and 75.4% in total recoverable streptococci and in S. mutans in plaque, and corresponding reductions of 50.8% and 39.2% in saliva. The in vitro stu dy revealed that streptococci from the mutans group were more susceptible t o the bactericidal activity of the essential oil mouthrinse than streptococ ci from the mitis group. Conclusions: As antimicrobial mouthrinses are most frequently recommended t o patients whose mechanical oral hygiene procedures are not adequate for th e control of supragingival plaque and gingivitis, this study provides an ad ditional rationale for the inclusion of the essential-oil mouthrinse as an adjunct to daily oral hygiene procedures.