The American Dental Association (ADA) and the National Dental Association (NDA) are two organizations that represent dentists in the United States. The ADA is a professional association of dentists dedicated to the public's oral health, ethics, science, and professional advancement. The NDA is a non-profit organization that works to improve the oral health of African Americans and other underserved populations. Both organizations provide resources and support for dentists, including continuing education, advocacy, and research.