Effect of a polyhexamethylene biguanide mouthrinse on bacterial counts and plaque

For various clinical applications, polyhexamethylene biguanide (PHMB) has been used for many years as an antiseptic in medicine. Little is known, however, of its antibacterial activity in the oral cavity and its ability to inhibit plaque formation. In this study, a 0.04% PHMB mouthrinse (A) was compared with a negative control placebo rinse (10% ethanol, flavour) (B) and 2 positive control chlorhexidine rinses, one of which was a 0.12% aqueous solution (C) and the other a commercially available mouthrinse (Skinsept mucosa) diluted to a chlorhexidine concentration of 0.12% (D).

The study was a double-blind, randomised 4-replicate 4 x 4 Latin square cross-over design. Plaque regrowth was assessed with the Turesky et al. modification of the Quigley and Hein plaque index. The in vivo antibacterial effect was assessed by taking bacterial counts from the tooth surface (smears from the lingual surface of 16) and mucosa (smears from the buccal mucosa) 4 h after the 1st rinse with the preparations on day 1 and prior to the clinical examination on day 5. 16 volunteers participated, and on day 1 of each study period were rendered plaque-free, ceased toothcleaning, and rinsed 2x daily with the allocated mouthrinse. On day 5, plaque was scored and smears were collected according to the protocol. Washout periods were 9 days. Data were analysed using ANOVA with Tukey HSD adjustment for multiple comparisons (significance level alpha=0.05).

Mouthrinses A, C, and D were significantly more effective in inhibiting plaque than the placebo (B). Mouthrinse C was significantly better than mouthrinses A and D, while mouthrinses D and A were equally effective in inhibiting plaque. Bacterial count reductions on the tooth surface with mouthrinse C were significantly greater compared to mouthrinse A and the placebo (B). The reduction of bacterial counts on the mucosa with C was significantly greater than with A and B after 4 h and significantly greater than with A, B and D after 5 days. Mouthrinse A reduced bacteria on the mucosa significantly more effectively than the placebo (B) after 4 h and 5 days, while mouthrinse D was more effective than the placebo (B) after 4 h.

The results indicate that a 0.04% PHMB mouthwash inhibits plaque regrowth and reduces oral bacterial counts, and may be used in preventive applications in the oral cavity.