Comparison of tongue coating removal methods: A preliminary study with a systematic review

Abstract Background It is known that tongue coating is one of the main causes of halitosis, as well as various diseases such as aspiration pneumonia. However, no method for removing tongue coating has been established. Materials and methods We first performed a systematic review of 32 papers that compared the effects of multiple tongue coating removal methods. Next, we conducted a preliminary, randomized controlled trial on the effect of three disinfectants on tongue cleaning. Thirty-two patients were randomly assigned to the following four groups; 1) benzethonium chloride group (BC group), 2) povidone iodine group (PI group), 3) hydrogen peroxide group (HP group), and 4) tap water group (TW group). Tongue cleaning was performed using a toothbrush with the 4 test drugs, and the number of bacteria on the dorsum of the tongue before and after tongue cleaning was measured using the Rapid Oral Bacteria Quantification System. Results The systematic review suggested that, 1) mechanical tongue cleaning reduced the tongue coating, 2) some antibacterial mouthwashes reduced the tongue coating, and 3) some diets, chewing gums and tablets also reduced the tongue coating. The randomized controlled trial showed that the number of bacteria decreased significantly when tongue brushing was done using povidone iodine and hydrogen peroxide solution, while, 0.2% benzethonium chloride and tap water did not decrease the bacterial count. Conclusions Tongue brushing with povidone iodine or hydrogen peroxide is the most effective method of reducing the bacterial count of tongue coating. Trial Registration The study was registered in the University Hospitals Medical Information Network Clinical Trials Registry (UMIN-CTR), UMIN000038544 on November 11, 2019: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000043924.