pH-resonse of dental plaque after sucrose challenge and mouthrinse pre-treatment

The objectives: of this study were to compare acid production by dental plaque in adults after rinsing with chlorhexidine (0.2%; CHX), amine fluoride/stannous fluoride (250 ppm F; AmF-/SnF), Listerine or cetylpyridinium chloride (CPC). Methods: A telemetric system used in adults (n=5) to evaluate cariogenic sucrose challenge [Stösser et al. Oralprophylaxe 2005] was adjusted to determine antibacterial properties of mouthrinses. The sensing membrane of the glass pH electrode was mounted in the interdental area. After insertion the prostheses were not removed during the test period, thus allowing undisturbed growth of plaque. Subjects were asked to refrain from mechanical oral hygiene but twice a day they used the mouthrinses for 30 seconds (pre-treatment). The pH-response of 4-day-old plaque was measured after challenge with 10% sucrose which was maintained in the mouth for 2 min. In a second approach plaque was accumulated at the electrode without any disturbance for four days and following the mouthrinses were used immediately before sucrose exposition. The area of the curve was calculated for 30 minutes in µmol/L[H+]. Results: The average pH drop caused by sucrose was pH 4.33 ± 0.18 after 19 min in 5 adults (10 measurements). The inhibition of acid production amounted to 66% by CHX, to 55% by AmF/SnF, to 45% by Listerine but after CPC the amount of acid increased by 52%. Pre-treatment of plaque during its accumulation by CHX, AmF/SnF and CPC caused a “clean electrode” with very limited acid production (around pH 5.7) and only after Listerine pH was depressed to 4.9. Conclusion: Antimicrobial mouthrinses do not inhibit completely bacterial metabolism and influence more the process of plaque formation on solid surfaces.