Abstract: Objective: To determine the effect of CPC mouthwash on the proportions of red complex bacteria in patients with moderate to severe chronic periodontitis by RT-qPCR. Methods: Forty patients with periodontitis were randomly assigned to two groups: experimental group (SRP+CPC) and control group (SRP+ placebo). Clinical parameters were recorded at baseline and at 4 weeks. Subgingival plaque, gingival crevicular fluid, and saliva samples were collected, and the content of trypsin-like enzyme was detected using BANA test. RT-qPCR was used to detect the proportions of P.gingivalis, T.forsythia and T.denticola in total bacteria. Results: AL, BOP, and PLI significantly improved (P<0.01) after treatment in the experimental group. Only AL significantly improved in the control group (P<0.01). The level of trypsin-like enzyme in subgingival plaque and gingival crevicular fluid for both groups decreased significantly (P<0.05). The numbers of P. gingivalis decreased significantly in both groups (P<0.01), while T.forsythia decreased significantly in the experimental group (P<0.01). There was no significant difference in the numbers of T.denticola after treatment compared to baseline. There was a significant correlation between the proportions of P.gingivalis, T.forsythia, and T.denticola (P<0.01). Conclusion: CPC can inhibit plaque formation and improve clinical parameters in patients with moderate to severe chronic periodontitis, but has no significant inhibitory effect on P.gingivalis, T.forsythia, and T.denticola.

Key words: Porphyromonas gingivalis, Tannerrella forsythia, Treponema denticola, Real-time quantitative polymerase chain reaction