title: Effects of tongue cleaning on bacterial flora in tongue coating and dental plaque: a crossover study.
abstract: BACKGROUND
  The effects of tongue cleaning on reconstruction of bacterial flora in dental plaque and tongue coating itself are obscure. We assessed changes in the amounts of total bacteria as well as Fusobacterium nucleatum in tongue coating and dental plaque specimens obtained with and without tongue cleaning.
  
  
  METHODS
  We conducted a randomized examiner-blind crossover study using 30 volunteers (average 23.7 ± 3.2 years old) without periodontitis. After dividing randomly into 2 groups, 1 group was instructed to clean the tongue, while the other did not. On days 1 (baseline), 3, and 10, tongue coating and dental plaque samples were collected after recording tongue coating score (Winkel tongue coating index: WTCI). After a washout period of 3 weeks, the same examinations were performed with the subjects allocated to the alternate group. Genomic DNA was purified from the samples and applied to SYBR® Green-based real-time PCR to quantify the amounts of total bacteria and F. nucleatum.
  
  
  RESULTS
  After 3 days, the WTCI score recovered to baseline, though the amount of total bacteria in tongue coating was significantly lower as compared to the baseline. In plaque samples, the bacterial amounts on day 3 and 10 were significantly lower than the baseline with and without tongue cleaning. Principal component analysis showed that variations of bacterial amounts in the tongue coating and dental plaque samples were independent from each other. Furthermore, we found a strong association between amounts of total bacteria and F. nucleatum in specimens both.
  
  
  CONCLUSIONS
  Tongue cleaning reduced the amount of bacteria in tongue coating. However, the cleaning had no obvious contribution to inhibit dental plaque formation. Furthermore, recovery of the total bacterial amount induced an increase in F. nucleatum in both tongue coating and dental plaque. Thus, it is recommended that tongue cleaning and tooth brushing should both be performed for promoting oral health.
authors.forename: Miki
authors.initials: M
authors.lastname: Matsui
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Chosa
authors.forename: Yu
authors.initials: Y
authors.lastname: Shimoyama
authors.forename: Kentaro
authors.initials: K
authors.lastname: Minami
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Kimura
authors.affiliation: Division of Preventive Dentistry, Department of Oral Medicine, Iwate Medical University School of Dentistry, 3-27 Chuodori 1-chome, Morioka 020-8505, Japan. mkishi@iwate-med.ac.jp.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kishi
mesh_terms: D000328:Adult; D001419:Bacteria / Q000302:isolation & purification; D058491:Bacterial Load; D018592:Cross-Over Studies; D003773:Dental Plaque / Q000382:microbiology*; D016967:Fusobacterium nucleatum / Q000302:isolation & purification; D006801:Humans; D009910:Oral Hygiene / Q000295:instrumentation / Q000379:methods*; D016037:Single-Blind Method; D014059:Tongue / Q000382:microbiology* / Q000473:pathology; D055815:Young Adult