An Appreciation of a Giant in Orofacial Sciences Research-John Greenspan.

Professor John S. Greenspan died on March 31, 2023. He was a renowned and accomplished academic, dentist/scientist, pathologist, and administrator who made sustained and significant international impacts on numerous fields over half a century. John was arguably best known for his work with his wife, Dr. Deborah Greenspan, on the oral aspects of AIDS and the role of viruses in oral epithelial and salivary gland lesions. He had a lifelong interest in Sjögren's syndrome, culminating in the leadership of the Sjögren's International Collaborative Clinical Alliance. He was also widely recognized as one of the leading investigators into the understanding of oral mucosal diseases, including recurrent aphthous stomatitis. He and his colleagues' major contributions to HIV research and care included the discovery of the oral lesion "hairy leukoplakia," its etiological association with Epstein-Barr virus, and other oral lesions in the natural history of HIV disease. In recent years, John turned his attention to global oral health inequalities, helping to establish the International Association for Dental Research's Global Oral Health Inequalities Research Network and serving as its first president. He led many organizations with humble authority, knowledge, wit, and wisdom and mentored colleagues from all over the world, especially from lower- and middle-income countries. John leaves a very special legacy based on example and scientific curiosity, and his work has not only made a lasting impact on his colleagues but also translated to abiding benefit for patients.