EFFECTS OF CHLORHEXIDINE-FLUORIDE MOUTHRINSES ON VIABILITY, ACIDOGENIC POTENTIAL, AND GLYCOLYTIC PROFILE OF ESTABLISHED DENTAL PLAQUE

Inhibition of dental plaque acidogenicity by chlorhexidine (CHX) mouthrinses has been ascribed to a long-lasting bacteriostatic effect due to binding of CHX to oral surface structures combined with a slow release rate from the binding sites. The present aims were to study the effects of CHX-containing mouthrinses on the viability and glycolytic activity of established plaque in order to assess the bactericidal versus the bacteriostatic effects. Following 2 days of plaque accumulation, three groups of 10 students rinsed with either 12.0 mM NaF, 0.55 mM CHX plus NaF, or with 2.2 mM CHX plus NaF. Plaque samples were collected before and 90 min after mouthrinsing. The pH in pooled pre- and post-rinse plaque samples was recorded before and up to 10 min after the addition of D-[U-C-14]glucose. Total colony-forming units in each sample were determined. High-performance liquid chromatography analyses showed lactate to be the major extracellular glycolytic metabolite in all samples. CHX-NaF markedly reduced the colony-forming units, the pH fall from fermentation of glucose, as well as glucose consumption and lactate formation, whereas NaF alone exhibited no such effects. The reduction of glucose consumption by the CHX-NaF mouthrinses corresponded to the reduction of colony-forming units, indicating no bacteriostatic effect. The plaque pH in vivo was monitored in each student 90 min after mouthrinsing with the test solutions prior to and up to Ih after a sucrose mouthrinse using touch microelectrodes. The CHX-NaF mouthrinses reduced the fall in pH significantly (p < 0.05) as compared with the NaF mouthrinse. The results suggested that the reduced acid formation by dental plaque following a CHX mouthrinse is due to a bactericidal effect rather than a long-lasting bacteriostatic action.