title: In situ neutralisation of the antibacterial effect of 0.2% Chlorhexidine on salivary microbiota: Quantification of substantivity.
abstract: OBJECTIVE
  To quantify the substantivity of a single 0.2% Chlorhexidine mouthwash in saliva after its neutralisation with tooth-brushing and 1% acetic acid, in order to identify the effect of Chlorhexidine substantivity in regard to the re-growing period of the salivary bacteria.
  
  
  METHODS
  Unstimulated saliva samples were collected from a group of 15 healthy individuals at baseline (BS), and then 30s and 1, 3, 5 and 7h after the following protocols were performed: a single sterile water mouthwash (M-WATER) (negative control), a single 0.2% Chlorhexidine mouthwash (M-0.2% CHX) (positive control) and a single 0.2% Chlorhexidine mouthwash followed by a complete and detailed tooth-brushing, and a single 1% acetic acid mouthwash (M-0.2% CHX+NP). The samples were analysed using an epifluorescence microscope in combination with LIVE/DEAD(®) BacLight™ fluorescence solution.
  
  
  RESULTS
  After the M-0.2% CHX treatment, the bacterial vitality was significantly lower than BS until 7h (87.6 ± 6.5% vs. 73.6 ± 8.8%; p<0.001). However, after M-0.2% CHX+NP, the bacterial vitality remained significantly lower until 3h with regard to BS (81.4 ± 3.8% vs. 68.1 ± 10.6%; p=0.001), increasing at 5 and 7h (no differences from BS).
  
  
  CONCLUSIONS
  The immediate antibacterial effect of a single 0.2% Chlorhexidine mouthwash is so potent that the bacterial population needs more than 3h to return to baseline bacterial vitality levels. The substantivity of a 0.2% Chlorhexidine mouthwash is a property that significantly increases its antibacterial activity from the first hour and contributes to extend the duration of its effect by at least double.
authors.affiliation: Oral Sciences Research Group, School of Medicine and Dentistry, University of Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Quintas
authors.affiliation: Oral Sciences Research Group, School of Medicine and Dentistry, University of Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Prada-López
authors.affiliation: Department of Clinical Research, Periodontology Unit, UCL Eastman Dental Institute, London, United Kingdom.
authors.forename: N
authors.initials: N
authors.lastname: Donos
authors.affiliation: Oral Sciences Research Group, School of Medicine and Dentistry, University of Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Suárez-Quintanilla
authors.affiliation: Oral Sciences Research Group, School of Medicine and Dentistry, University of Santiago de Compostela, Santiago de Compostela, Spain. Electronic address: inmaculada.tomas@usc.es.
authors.forename: I
authors.initials: I
authors.lastname: Tomás
mesh_terms: D000328:Adult; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D002710:Chlorhexidine / Q000494:pharmacology*; D015169:Colony Count, Microbial; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D064307:Microbiota / Q000187:drug effects*; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009067:Mouthwashes / Q000494:pharmacology*; D012463:Saliva / Q000382:microbiology*; D014099:Toothbrushing
chemical_list: D000891:Anti-Infective Agents, Local; D009067:Mouthwashes; D002710:Chlorhexidine
keywords: Acetic acid; Chlorhexidine; Epifluorescence; Mouthwash; Neutralisation; Substantivity