MSX1 and tooth agenesis: Hypodontia occurs when there are one to five missing teeth and its prevalence reaches 2.6–11.3% depending the ethnic group.1 Although the etiology of dental agenesis involved genetic and environmental factors, the genes more frequently associated with hypodontia in different populations are AXIN2, MSX1, PAX9, EDA, and WNT10. 2,3