Effect of phenoxyethanol, chlorhexidine and their combination on subgingival plaque bacteria

The effects of phenoxyethanol, chlorhexidine and a mixture of both on subgingival plaque samples from 44 patients with chronic periodontitis were investigated in vitro. At a concentration of 0.5 mg/ml, chlorhexidine inhibited the growth of all cultivable bacteria in all 44 samples while a comparable effect was achieved with phenoxyethanol only at a concentration of 20 mg/ml. All cultivable bacteria in the samples were inhibited by a mixture of the two agents containing 5 mg/ml of phenoxyethanol and 0.125 mg/ml of chlorhexidine i.e. considerably lower concentrations than when the agents were used separately. Kill times for 99.9% of bacteria in 19 of the plaque samples were less than 15 min using a chlorhexidine concentration of 0.125 mg/ml, but were from 24 to greater than 240 min with 10 mg/ml phenoxyethanol. A mixture of the two agents at these concentrations was more effective than either agent alone with 99.9% kill times of less than 10 min. This investigation has shown that the addition of phenoxyethanol to chlorhexidine results in a mixture which is effective against bacteria found in subgingival plaque samples from patients with chronic periodontitis. It also implies that formulations with lower concentrations of chlorhexidine than those currently in use may be effective as adjuncts in the treatment of chronic periodontitis.