The experimental
gingivitis model was used to compare the anti-plaque, anti-
gingivitis and anti-microbial efficacies of a phenolic compound (
Listerine) and an
amine/
stannous fluoride mouthwash (
Meridol), using a placebo preparation as negative control and a
chlorhexidine solution as positive control in a double-blind study. After professional toothcleaning, 36 volunteers performed optimal
oral hygiene for a period of 2 weeks. They then ceased all
oral hygiene procedures for 21 days during which they rinsed twice daily with 1 of the 4 mouthrinses. After 3 weeks of rinsing, plaque indices remained the lowest in the
chlorhexidine group, while subjects using
Listerine or
Meridol harbored similar indices significantly lower than that of individuals rinsing with the placebo
solution. Up to that time, the gingival index scores were equal in all groups except for the
chlorhexidine group in which the values only amounted to half of these encountered in the other groups. The plaque vitality scores showed a bactericidal effect in vivo of
chlorhexidine during the entire time of experimental
gingivitis. In contrast, the data gave no evidence of an antibacterial effect in vivo of
Listerine. The efficacy of
Meridol to kill micro-organisms was similar to
chlorhexidine during the early stages of plaque accumulation and, with time, became insignificant. This study has demonstrated that
chlorhexidine was superior to
Listerine and
Meridol in its ability to maintain low plaque scores and gingival health during this 3-week period of no mechanical
oral hygiene. Moreover, it was also shown that
Meridol was as effective as
Listerine in reducing plaque accumulation and, in contrast to
Listerine, possessed a remarkable but transient antibacterial effect in vivo.