Dentistry 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. A dentist is a doctor qualified to practice dentistry. In most countries, several years of training in a university (usually 4-8) and some practical experience working with actual patients' dentition are required to become a qualified dentist. The patron saint of dentists is Saint Apollonia, martyred in Alexandria by having all her teeth violently extracted.

General Dental Practice includes most examination, diagnosis, treatment planning, treatment, and prevention of disease. The dentist frequently uses X-rays and other equipment to ensure correct diagnosis and treatment planning. Treatment may include filling cavities, removing the nerves of teeth, treating diseases of the gums, removing teeth, and replacing lost teeth with Bridges and Dentures (Dental Plates). Anesthesia is often used in any treatment that might cause pain.

Teeth may be filled with Gold, Silver, Amalgam, or Cements, and with fused Porcelain Inlays. Dentists treat diseases of the mouth and gums such as trench mouth and Periodontitis. An important part of general dental practice is preventive dentistry. If a dentist examines a patient's teeth at regular intervals, a disease may be detected and treated before it becomes serious. Dentists also demonstrate proper methods of brushing and flossing the teeth. They may advise their patients about what food to eat or to avoid for good dental health. Dentists may also treat teeth with Fluorides or other substances to prevent decay.

In the United States, dentists earn either a D.D.S. (Doctor of Dental Surgery) or D.M.D.(Doctor of Dental Medicine) degree. There is no difference in the training for either degree. The degrees are equivalent, and recognized equally by all state boards of dentistry.

There are 56 Accredited Dental schools in the United States requiring 4 years of post graduate study (except for one unique 3 year program at the University of the Pacific)[14]. Most applicants to dental school have attained at least a B.S. or B.A. degree, however, a small percentage are admitted after only fulfilling specific prerequisite courses. So unlike many other countries, it can take more than 8 years to become a dentist.

(List of dental schools in the United States) The degrees D.D.S. and D.M.D. require equivalent education and are identical in every way. The difference relates to the history involved in the division of medicine and surgery in medical practice. There has been a recent movement to include a 5th year of education that focuses on purely practical training in the clinical setting. In at least one state, a state dental license can be received without taking the licensing exam (State Board Exam) upon completing this additional year of training.

Dentists are licensed and regulated by the state in which they practice. The license is only valid in the issuing state and is non-transferable. There are many cooperative agreements between states that allow recognition of another state's license so as to procure a license either via "licensure by credentials" or "licensure by reciprocity."

A dentist may go on for further training in a dental specialty which requires an additional 1 to 7 years of post-doctoral training. There are 9 recognized dental specialties. They are Endodontics(root canal treatment), Oral and Maxillofacial Pathology, Oral and Maxillofacial Radiology, Pediatric Dentistry, Periodontics(gums), Prosthodontics (complicated dental reconstruction), Orthodontics(braces), Oral and Maxillofacial Surgery(tooth removal and surgery of the oral and related structures), and Dental Public Health.

There is no specialty in esthetic dentistry or implantology, and no additional training is required for a dentist to make the claim of being an esthetic or cosmetic dentist. Dentists are forbidden to claim that they are specialists in areas of practice in which there is no recognized specialty. They may limit their practices to a single area of dentistry, and claim that their practice is limited to that area.

Any general dentist may perform those procedures designated within the enumerated specialties if they deem themselves competent. Many general dentists train in certain aspects of the above specialties such as the placement and restoration of dental implants, advanced prosthodontics and endodontics, and have limited or heavily focused their practices to these areas. When a general dentist performs any procedure that falls within the realm of a specialty, they are expected to perform with the same level of expertise as a certified specialist and are legally held to such standards with respect to any issues of malpractice.

There are nine dental specialties recognized by the American Dental Association and require 2-6 years of residency training after dental school.

The specialties are Dental Public Health (study of dental epidemiology and social health policies), Endodontics (root canal therapy), Oral and Maxillofacial Pathology (study, diagnosis, and often the treatment of oral and maxillofacial related diseases), Oral and Maxillofacial Radiology (study and radiologic interpretation of oral and maxillofacial diseases), Oral and Maxillofacial Surgery (extractions and facial surgery), Orthodontics and Dentofacial Orthopaedics (straightening of teeth), Pedodontics (pediatric dentistry; i.e. dentistry for children), Periodontics (treatment of gum disease), Prosthodontics (replacement of missing facial anatomy by prostheses such as dentures, bridges and implants).

Specialists in these fields are designated registrable (U.S. "Board Eligible") and warrant exclusive titles such as orthodontist, oral surgeon, pedodontist, periodontist, or prosthodontist upon satisfying certain local (U.S. "Board Certified") registry requirements.

Two other post-graduate formal advanced education programs: General Practice Residency (advanced clinical and didactic training with intense hospital experience) and Advanced Education in General Dentistry (advanced training in clinical dentistry) recognized by the ADA do not lead to specialization.

Other dental education exists where no post-graduate formal university training is required: cosmetic dentistry, dental implant, temporo-mandibular joint therapy. These usually require the attendance of one or more continuing education courses that typically last for one to several days. There are restrictions on allowing these dentists to call themselves specialists in these fields. The specialist titles are registrable titles and controlled by the local dental licensing bodies.

Forensic odontology consists of the gathering and use of dental evidence in law. This may be performed by any dentist with experience or training in this field. The function of the forensic dentist is primarily documentation and verification of identity.

Geriatric dentistry or geriodontics is the delivery of dental care to older adults involving the diagnosis, prevention, and treatment of problems associated with normal aging and age-related diseases as part of an interdisciplinary team with other health care professionals.