National Dental Hygiene Day, also known as National Dental Health Day, is observed in Thailand every October 21. Established by the government in 1989, this day commemorates the birth anniversary of Princess Srinagarindra, who significantly contributed to public health in the country. The observance aims to address the disparity in dental care access between urban and rural areas, highlighting the importance of universal dental care coverage. On this day, organizations, with support from the Ministry of Public Health and volunteer dentists, conduct free dental examinations in remote regions. Additionally, educational institutions and dental clinics host special events to promote oral hygiene practices, such as tooth brushing and flossing. National Dental Hygiene Day coincides with National Nurses’ Day, both honoring Princess Srinagarindra's legacy in healthcare.