Specialty that focuses on preventative treatment, evaluates periodontal health, removes calculus, and provides clean tooth surfaces below the gingiva, prophylaxis, and patient education. Some states allow them to apply sealants, mount dental radiographs, chart conditions in the oral cavity, inject local anesthetics, or administer nitrous oxide. They must complete one year of dental hygiene prerequisites before being accepted into an accredited program so they can pass the national and state written and clinical exam.