Microscopic Observation of Human Tongue and Tongue Coating

Objectives: The main cause of halitosis is attributed to tongue coating. Therefore it is necessary to investigate the process of tongue coating formation. Bacteriological aspects of tongue coating had been reported in many papers, however there were little papers on morphological observations of tongue coating. The purpose of this study was to observe human tongue and tongue coating histologically and to clarify the characteristic structure of them. Methods: The tongue specimens from cadavers were used for light microscope study. The specimens were embedded in paraffin or in Rigolac resin. The tongue coating was scraped with a metallic spatula from the tongue dorsum surface of the patients at Fresh Breath Clinic in Dental Hospital. The tongue coating was observed by light microscope and transmission electron microscope (TEM). Results: According to light microscope observation, each lingual papilla of the tongue surface was covered by epithelial cells in various stages of exfoliation. Microorganisms were observed within the layer of epithelial cells. The papillary had the structures which increased surface area. These characteristic structures seemed to be favorable for accumulation of oral debris and microorganisms. Tongue coating were mainly composed of microorganisms and desquamating keratin was observed among them. By TEM observations of tongue coating, microorganisms were adhered, eroded and dissolved the keratinized layer. Conclusion: In this study, it was observed that interaction of microorganisms and the keratinized layer as well as adhesion of microorganisms. It was suggested that further investigation on the relationship between production of volatile sulfur compounds (halitosis substance) and the morphological structure of tongue and tongue coating.