The most common oral diseases are dental caries (tooth decay), periodontal (gum) diseases, and oral cancer.

Dental caries results from plaque that forms on a tooth surface and converts the free sugars from foods and drinks into acids that case a breakdown of tooth enamel over time. Unhealthy diets, including continuous consumption of free sugars, and poor oral hygiene lacking fluoride exposure and toothbrushing to remove plaque can lead to dental caries. Pain, infection and tooth loss can also result if not treated early.

Periodontal disease includes gingivitis and periodontitis. Gingivitis causes swollen, painful or bleeding gums and bad breath. In its more severe form, periodontitis causes a loss of connective tissue and bones resulting in tooth loss. The main causes of periodontal disease include poor oral hygiene and tobacco use.

Oral cancer is cancer that develops in the lip and all parts of the oral cavity, and oropharynx. The initial symptoms include a persistent ulceration, pain, swelling, bleeding of the soft tissue, and difficulty in eating or speaking. The risk factors include tobacco use, areca nuts or betel quid chewing, and excessive alcohol consumption.

Other oral diseases include cleft lip and palate, oral manifestation of HIV, and oro-dental trauma.