A plethora of diseases affect the tissues of the maxillofacial complex. They include developmental, heritable, inflammatory, hyperplastic, neoplastic, metabolic and degenerative processes. Many of these diseases are localized, whereas others are manifestations of systemic or multisystem diseases. Regardless of their pathogenesis, diseases that affect teeth, bones, oral mucosa and salivary tissues result in clinically observable tissue changes that subsume many processes. Soft tissue mucosal diseases can be conveniently grouped into seven different lesion forms; included under each lesion type are specific disease processes of varying etiopathogenesis.