title: Structure of tongue microbiota and its association with halitosis
design: Totally 29 individuals with or without self-reported oral malodor were involved in this study. To eliminate confounding factors attributable to individual brushing habit or different oral hygiene products used, for each of the individual an one-week acclimation period using the assigned products of Crest KC  (One of the most common Crest anti-cavity toothpaste in market and NaF was the only ingredient with key activity) and Crest Standard toothbrush was administered prior to the halitosis measurements. In addition, subjects were given oral hygiene instructions on teeth brushing method and performed teeth-brushing two times a day. All halitosis meas-urements and intraoral examinations were performed by the same dental professional.   After the measurement of halitosis, tongue plaque was collected via the following steps. Moisture was reduced by drying the dorsum of the tongue with an appropriate amount of air. One sterilized cotton swab was used to scrape cross the tongue surface twice for approximately five seconds, applying gentle pressure. The head of the swab was then aseptically cut and placed into a 2 ml Eppendoff tubes and maintained on ice for subsequent DNA extraction.