Mood disorders refers to a heterogenous group of mental conditions characterized by extreme exaggeration and disturbance of mood and affect. This article examines major depression and bipolar disorders and how these disorders can affect a patient's dental care. The drugs used to treat these conditions have significant side effects that dentists should be aware of. In addition, important drug interactions can occur as a result of agents used by the dentist. The dentist should refer patients found with signs and symptoms of mood disorders for medical evaluation and treatment. Depressed patients often have poor oral hygiene due to a lack of interest in self-care. Xerostomia occurs due to depression and the drugs used to treat it. The dentist needs to provide an aggressive preventive dental education program for these patients, including the use of artificial salivary products, mouthwashes, and topical fluoride applications, in addition to the treatment of candidiasis when present.