You are required to take antibiotics before cleaning appointments and any appointments requiring major dental work. Endocarditis is a rare, life threatening inflammation of the lining of the heart muscle and its valves. It is caused by a bacterial infection. Although it can occur in anyone, it is much more common in people with certain heart conditions. Taking antibiotics prior to your dental appointment reduces the risk. If you have one of the conditions listed above then this puts you at a higher risk for infection and you must pre-medicate.