The Dental Hygienists' purpose is to recognize abnormal and normal oral anatomy and physiology, and to coach and motivate patients to achieve a healthy mouth. The majority of a dental hygienist's appointment is spent collecting and reviewing medical histories, examining, measuring, collecting diagnostic information, documenting, communicating, motivating, and sterilizing equipment. In a typical dental practice, the hygienist provides a complete assessment of the patient to the dentist and recommends a co-diagnosis and treatment recommendations for the patient. Such communication to the dentist include alerts to cracked teeth, decay/cavities, "pockets" or periodontitis, gingivitis, abnormal growth and development of the jaws and teeth, medical history and nutritional considerations, abnormal anatomy or tissue related to a variety of conditions such as vitamin deficiencies, viral infections, autoimmune disorders, and cancer. 

Depending on the extent of periodontal disease, a hygienist could spend anywhere from 25%-80% of the appointment time actually "cleaning teeth". The  process of "cleaning teeth" will differ depending on the periodontal diagnosis and can range from preventive scaling and polishing to root planing and curettage to remove diseased cementum, granulation tissue, as well as decades-old calcified bacteria imbedded in the cementum of the tooth. The act of cleaning or scaling teeth requires a refined sense of touch, fine motor skills, specialized knowledge of biology, microbiology, physics, and a gift for patience and human compassion.

In the United States, the process to become a Registered Dental Hygienist includes:

• Completion of pre-requisite science and mathematics courses, including gross anatomy cadaver dissection and physiology, microbiology, sociology, and inorganic chemistry.
• Passing an interview process with the directors of the hygiene program, maintaining a high GPA throughout the pre-requisite courses, and sometimes proving experience or shadowing in a dental office.
• Completion of at least an Associate Degree in Dental Hygiene from a CODA accredited college, after being accepted to the program based on GPA, interviews, and prior dental office experience. Many hygienists choose to complete a Bachelors or Masters degree, and some have a PhD in their chosen field.
• Passing regional clinical exams, passing National Board written exams, passing state jurisprudence exams, submitting fingerprints for background checks,  registration with the state in order to be licensed to practice.
• Maintenance of yearly or biyearly continuing education, including required CPR, jurisprudence and asepsis, and in some states, substance abuse awareness courses.

The Federal Standard Occupational Classification from the United States Office of Management and Budget classifies dental hygienists as "Healthcare Diagnosing or Treating Practitioners", which is the same classification as dentists.