Dentistry, more appropriately "dental surgery," is the art and science of prevention, diagnosis, and treatment of conditions, diseases, and disorders of the oral cavity, the maxillofacial region, and its associated structures as it relates to human beings. While the work of dentists is often surgical in nature, dentists can and do treat many diseases of the oral cavity and face chemotherapeutically (i.e. with prescribed medicines).

See also: http://en.wikipedia.org/wiki/Dentistry