An observational study was conducted to clarify the morphological features of the fine structure of the tongue coating, which is one of the main causes of halitosis. Tongue specimens from cadavers, whom dental students had practiced on for anatomy class, were used as materials to observe the surface structure. Tongue coatings were obtained from patients who were referred to the Fresh Breath Clinic, Dental Hospital, Tokyo Medical and Dental University. After macroscopic observation of the tongue surface, tongue coating and examination of halitosis, the tongue coating was scraped carefully, following which it was observed using a light microscope and transmission electron microscope (TEM) . The results obtained were as follows. The tongue coating consisted mainly of bacteria and desquamated keratinized epithelium which originated chiefly from the filif orm papilla. The desquamated keratinized epithelium was also composed of degenerated epithelium of every level, from a comparatively normal epithelium to a fragmented altered epithelium. In addition, the level of degeneration of the keratinized epithelium differed according to the state of distribution and the revitalization of bacteria located in its surroundings. The intensity of halitosis increased with the amount of tongue coating. Increased amounts of tongue coating, however, did not necessarily correlate with increased halitosis in the patients. It was suggested that the severity of halitosis was probably associated with the level of bacterial invasion-related degeneration of the desquamated keratinized epithelium (tongue coating's quality) .
