A joint study by Kao Corporation and Shimadzu Corporation found that people more prone to plaque have more tongue coating and more amino acids in the coating. The findings point to a new approach that emphasizes care for the entire mouth.
Through joint research with Shimadzu Corporation, Kao Corporation found that people more prone to plaque have more tongue coating, the buildup on the surface of the tongue, as well as more amino acids that serve as nutrients for bacteria in the coating. The findings suggest that these individuals may be more prone to bacterial growth on the teeth and increased plaque.
The study was conducted on 40 healthy men and women. After plaque removal, oral cleaning was suspended for 2 days, after which plaque, tongue coating and saliva were comprehensively analyzed for their quantities, bacterial balance and metabolites. Following the study, the group with high plaque levels was compared with the group with low plaque levels.
The group more prone to plaque had approximately 1.2 times as much tongue coating, and differences were also found in components that may serve as nutrients for bacteria in the coating. Aspartic acid, for example, was approximately 1.8 times higher. More than 1000 components and bacterial species were evaluated in total.
The results were presented at the 69th Annual Meeting of the Japanese Society of Periodontology, held in Hiroshima Prefecture on 16–17 October 2026. The findings point to a future oral-care research policy that emphasizes care for the entire mouth, including the tongue, rather than the teeth alone.