Tooth loss in one's 20s can result from various factors. Poor oral hygiene, leading to gum disease and tooth decay, is a primary cause. Injuries from sports or accidents can also result in tooth loss. Genetic conditions, such as early-onset periodontitis, may predispose some individuals to dental issues. Lifestyle choices, including smoking and a diet high in sugar, can further contribute to dental deterioration. Additionally, underlying health conditions like diabetes can affect gum health, increasing the risk of tooth loss.