This Special Issue was designed to provide a multifaceted look at the latest clinical and research findings in the field of geriatric dentistry, which has rapidly gained importance since the beginning of the 21st century. It covers oral frailty, rapid oral health deterioration (ROHD), and oral hypofunction syndrome as comprehensive disease concepts related to the oral health of older people, explains their causes, and introduces the latest technology for diagnosing the deterioration of the oral environment and of oral function. It also discusses the strategy and methodology of oral healthcare in order to prevent declines in oral health and analyzes the impact of the COVID-19 pandemic. Furthermore, the impact of declining oral health on the overall health of older people is discussed from the perspectives of nutritional status, sarcopenia, and frailty.