Oral health is closely linked to nutritional status and physical activity. As we age, not only do our legs and hips weaken, but oral function also declines. Preventing oral frailty—a condition characterized by a gradual decline in oral function that often begins with reduced interest in oral health—is important for maintaining healthy life expectancy. The oral microbiome plays a crucial role in oral health. Our research focuses on understanding the oral microbiome and developing oral microbiome evaluation methods, oral probiotics, and functional materials, with the ultimate goal of extending healthy life expectancy through the prevention of oral frailty.