The common reasons for adult teeth to fall out are trauma, periodontitis, gum recession and so on. 1. trauma: if the teeth are hit by external force, resulting in serious damage to the teeth, the teeth may appear to fall out. 2. periodontitis: periodontitis, repeated inflammatory stimulation, teeth loosening, more and more gap between the teeth, more and more sparse, serious cases of teeth can fall out. 3. Gum recession: some older people with age, alveolar bone shrinkage, gums lack of nutrient supply, gum recession occurs, resulting in tooth loss. Adult teeth to fall out may also have other reasons, it is recommended to go to the hospital in a timely manner, under the guidance of professional doctors standardized treatment. Daily life, pay attention to maintain oral hygiene, regular oral examination, oral cleaning and other prevention of oral diseases to prevent the occurrence of tooth loss.