The oral cavity is the most anterior head and neck site. It is separated from the oropharynx by an imaginary line extending from the anterior tonsillar pillars to the junction of hard and soft palate to the circumvallate papillae.The oral cavity is divided into several subsites including the oral tongue, floor of the mouth, retromolar trigone, alveolar ridge, hard palate, buccal mucosa, gingiva and lips (Fig. 1).