EFFECTS OF MOUTHRINSES WITH CHLORHEXIDINE AND ZINC IONS COMBINED WITHFLUORIDE ON THE VIABILITY AND GLYCOLYTIC ACTIVITY OF DENTAL PLAQUE

Inhibition of plaque acidogenicity by a mouthrinse with chlorhexidine (CHX) or zinc ions has been ascribed to a prolonged bacteriostasis due to substantive properties of the agents. The present aim was to study the effects of mouthrinses with CHX and Zn ions combined with fluorid e on the viability and glycolytic activity of dental plaque in order t o assess the bacteriostatic versus possible bactericidal effects. Foll owing 2 d of plaque accumulation, 4 groups of 10 students rinsed with either 12 mM NaF (F), 0.55 mM CHX diacetate + F (F-CHX), 10 mM Zn acet ate + F (F-Zn), or with the three agents in combination (F-CHX-Zn). Pl aque samples were collected before and 90 min after mouthrinsing. Ther eafter, the in vivo plaque pH response to sucrose was monitored in eac h student using touch microelectrodes. F-CHX and F-CHX-Zn reduced the in vivo pH fall significantly as compared with F, whereas F-Zn exerted a non-significant inhibition. Pooled pre- and post-rinse plaque sampl es were used to measure the pH fall during fermentation of [C-14]-gluc ose, and the glycolytic profiles were analyzed by HPLC. Bacterial viab ility was assessed by counting the colony-forming units (CFU). All mou thrinses except F reduced glucose consumption and acid formation and t hus the pH fall. F-CHX reduced the CFU equal to the reduction of gluco se consumption, indicating that inhibition of plaque acidogenicity was due to a bactericidal rather than a bacteriostatic effect. F and F-Zn did not reduce the CFU, thus F-Zn decreased glucose metabolism withou t affecting plaque viability. F-CHX-Zn reduced both the CFU and glucos e metabolism of surviving plaque microorganisms.