Part II of the series on thyroid disorders discusses hypothyroidism and thyroiditis that may be found in dental patients. An overview of the conditions is presented. Presenting signs and symptoms, laboratory tests used to diagnose hypothyroidism and thyroiditis, and their medical management is discussed. The dental management of patients with hypothyroidism is discussed in detail. The dentist by detecting the early signs and symptoms of hypothyroidism and thyroiditis can refer the patient for medical diagnosis and treatment and avoid potential complications of treating patients with uncontrolled disease. Patients with thyroiditis may have a short period of being hyperthyroid and it may be best to avoid routine dental treatment during that period. Patients with suppurative thyroiditis should not receive routine dental treatment during the acute stage of the disease. The end stage of Hashimoto's thyroiditis results in hypothyroidism. Central nervous system depressants, sedatives, or narcotic analgesics must be avoided in patients with severe hypothyroidism because significant respiratory depression may occur. In addition, myxedematous coma, particularly in elderly hypothyroid patients, can be precipitated by central nervous system depressants, infection, and possibly stressful dental procedures. In medically well-controlled patients the dental treatment plan is not affected and most dental procedures can be offered to these patients.