Why does nan huaijin have no teeth?

Nan is a famous Taoist scholar and calligrapher in China. In his later years, his teeth did fall off because of some diseases, so nan huaijin had no teeth. Nan huaijin suffered from oral cancer and osteoporosis in his later years, which led to tooth loss. Despite his poor health, Nan still insists on academic research and calligraphy creation, and enjoys a high reputation in academic and literary circles. His academic achievements and charisma, as well as his love and promotion of China's traditional culture, made him known as the "contemporary Taoist master" and "China calligraphy master".