This document discusses adhesion and surface phenomena in dentistry. It defines adhesion as the attachment between two dissimilar substances and describes the components of an adhesive junction. Adhesion can occur through mechanical, chemical, or physical bonding. The document outlines factors that affect adhesion such as surface energy, surface tension, wettability and contact angle. It also lists criteria for successful bonding and discusses the importance of adhesion for dental procedures like bonding restorations and sealing pits/fissures. Specific techniques for bonding to enamel and dentin are covered, including acid etching of enamel and the use of etchants, primers and bonding agents to create a hybrid layer for dentin bonding.