Saliva is a vital yet often overlooked biofluid that plays a crucial role in our daily lives. From aiding in digestion to providing antimicrobial properties, understanding saliva and its changes throughout life is essential for maintaining both oral and systemic health. This book explores the fundamental characteristics of saliva, the structure and composition of this remarkable fluid, and the significant role it plays across different life stages. We explore the anatomy and function of salivary glands, assess how various local and systemic factors influence salivation, and highlight normal salivary flow rates. As we age, saliva undergoes significant changes that can affect our health, and we will investigate these transformations in infants, adolescents, young adults, and the elderly. Additionally, this book discusses the diagnostic potential of saliva in identifying diseases and the advancements in creating artificial saliva and substitutes. By examining the importance of saliva in human life and its future prospects, we aim to provide readers with a comprehensive understanding of this essential bodily fluid. This book provides an integrated perspective on saliva, highlighting its critical importance in health, disease, and future clinical applications.

Yeon-Hee Lee, DDS, PhD, is a Professor in the Department of Orofacial Pain and Oral Medicine at Kyung Hee University Dental Hospital, and an Affiliate Researcher at the School of Dentistry, Dental Research Institute, Seoul National University. From 2025 to 2026, she served as a Visiting Associate Professor at Massachusetts General Hospital in Boston. Her clinical and research interests include salivary gland disorders, xerostomia, halitosis, temporomandibular disorders (TMD) and orofacial pain, bruxism and sleep-related disorders, oral soft tissue diseases, oral potentially malignant disorders (OPMD) and oral cancer, and stress-related oral conditions.