The world continues to struggle with the COVID-19 pandemic, and there is concern over the increase in the needs of older people for nursing care. In this study, the relationships of the "tooth condition" with mobility and cognitive function were investigated in 1,000 residents of 14 special elderly nursing homes. In those using well-fitting dentures, the percentage of those capable of independent indoor mobility was highest at 21.6%, and the percentages of those able to communicate (66.2%), understand routines (47.5%), state their own age (36.2%), remember recent events (45.0%), state their own name (85.7%), understand seasons (43.7%), and understand places (46.4%) were significantly higher than in those in other "tooth conditions". This study clarified the relationships of the "tooth condition" with mobility and cognitive function, and maintaining an adequate "tooth condition" was suggested to contribute to the prevention of a condition requiring long-term nursing care.