Dentistry is a branch of health sciences devoted to preventing, diagnosing, and treating diseases of the \Tteeth\t and oral tissues and restoring or replacing missing teeth and oral structures. A dentist possesses a thorough knowledge of all oral tissues and has the ability to recognize and diagnose problems that develop in those tissues. A dentist not only is capable of providing medical and surgical therapy for oral problems, but also assists the medical physician in diagnosing systemic disease that may be first noted by changes in the mouth. HISTORY Oral disease has been a problem for humans from the beginning of history. Skulls of Cro-Magnon man, who inhabited the earth 25,000 years ago, show evidence of tooth decay. The earliest recorded reference to oral disease is from an ancient (5000 BC) Sumerian text that describes "tooth worms" as a cause of dental decay. There is historical evidence that the Chinese used acupuncture around 2700 BC to treat pain associated with tooth decay. Among the papyri of ancient Egypt is the Ebers Papyrus, which throws light on medical practices. It was written between 1700 and 1500 BC and contains material dating back as far as 3700 BC. The Papyrus Ebers contains references to diseases of the teeth, as well as prescriptions for substances such as olive oil, dates, onions, beans, and green lead, to be mixed and applied "against the throbbing of the bennut blisters in the teeth." An Egyptian lower jaw, dated by experts from 2900-2750 BC, demonstrates two holes drilled through the bone, presumably to drain an abscessed tooth. Much of early dentistry was practiced as part of the general practice of medicine. By the 5th century BC, Herodotus, a Greek historian, wrote "in Egypt, medicine is practiced on a plan of separation--each physician treats a single disorder, and no more--some undertaking to cure disease of the eye, others the head, others again of the teeth." Aesculapius--later regarded as a god but probably an actual person, a Greek physician who lived between 1300 and 1200 BC-- is credited by many with the concept of extracting diseased teeth. Later (500-300 BC), Hippocrates and Aristotle wrote of ointments and cautery with a red hot wire to treat diseases of the teeth and oral tissues. They also spoke of tooth extraction and the use of wires to stabilize jaw fractures or bind loose teeth. A renowned Roman medical writer, Celsus (100 BC), wrote extensively of oral diseases, including bleeding gums and ulcers of the oral cavity, as well as dental treatment such as narcotic-containing emollients and astringents. Arabian physicians attached great importance to clean teeth. They described various procedures to "scrape" the teeth and designed sets of specialized instruments to accomplish that task. Mouthwashes and dentifrice powders were applied by the Arabians using a "toothbrush," a small polishing stick that was beaten and softened at one end. Throughout the Middle Ages in Europe, dentistry was made available to wealthier individuals by physicians or surgeons who would go to the patient's home. Decay would sometimes be removed from teeth with a "dental drill," a metal rod that was rotated between the palms. Soft filling materials provided short-term alleviation of discomfort by keeping air from the open cavity. Dentistry for poorer people took place in the marketplace, where self-taught vagabonds would extract teeth for a small fee. From the Middle Ages to the early 1700s much dental therapy was provided by so called "barber surgeons." These jack-of-all-trades would not only extract teeth and perform minor surgery, but they also cut hair, applied leeches to let blood, and performed embalming. Italian sources from the 1400s mention the use of gold leaf as dental filling material. Later, the French described the use of soft lead fillings to repair teeth after decay was removed. Pierre Fauchard (1678-1761), a French surgeon, is credited with being the "father of modern dentistry." His book, The Surgeon Dentist, A Treatise On Teeth, describes the basic oral anatomy and function, signs and symptoms of oral pathology, operative methods for removing decay and restoring teeth, periodontal disease (pyorrhea), orthodontics, replacement of missing teeth, and tooth transplantation. Fauchard's text was followed by others that continued to expand the knowledge of the profession throughout Europe. Two of the most popular, Natural History of Human Teeth (1771) and Practical Treatise on the Diseases of the Teeth (1778), were written by an English physiologist, John Hunter, surgeon general to the British army. Dental practitioners migrated to the American colonies in the 1700s and devoted themselves primarily to the removal of diseased teeth and insertion of artificial dentures. Paul Revere, historically noted for his "midnight ride," was by trade a metalworker who constructed dentures from ivory and gold. George Washington had at least one set of dentures that was constructed of wood. Until the mid 1800s, dentures continued to be individually constructed by skilled artisans. Gold, silver, and ivory were common components, causing them to be very expensive and available only to the very wealthy. In 1851, a process to harden the juices of certain tropical plants into vulcanized rubber was discovered. The ability to mold this new material against a model of the patient's mouth and attach artificial porcelain teeth allowed the manufacture of less expensive dentures. Later, acrylic plastics replaced the use of rubber and porcelain in denture construction. A major contribution from the dental profession to the future of health care occurred in 1844 when Dr. Horace Wells, a Connecticut dentist, observed an exhibition of people reacting to inhalation of nitrous oxide (laughing gas). He initiated the use of nitrous oxide inhalation during dental therapy and founded the concept of inhalation analgesia and anesthesia. The medical community later modified and adopted inhalation anesthesia as a standard surgical management procedure. Greene Vardiman Black (1831-1915) was the leading reformer of American dentistry. Black devised a foot engine that allowed the dentist to keep both hands free while powering the dental drill. He developed modern techniques for filling teeth based upon biological principles and microscopic evaluation. Black also noted a densely matted bacterial coating on the teeth, and he proposed that dental caries and periodontal diseases were infections initiated by bacteria. It was not until the early 1960s, however, that scientific evidence confirmed this theory. MODERN DENTAL PRACTICE Contemporary dental practice would be virtually unrecognizable to the itinerant "tooth-drawers" of earlier times. While tooth decay is still present today, dentistry uses a variety of clinical and radiographic techniques to diagnose problems, remove decay, and repair teeth. Local anesthetics, usually Xylocaine or one of its derivatives, are injected into specific areas of the mouth to block nerve conduction and cause the tissues and teeth in the operative area to become numb. High-speed drills, rotating at speeds of up to 300,000 revolutions per minute, rapidly remove the decayed tooth structure with minimum discomfort. A water spray on the drill tip helps maintain a clear operating field and keeps the nerve inside the tooth from overheating. Fillings Silver amalgam, a refinement of filling materials first discovered by the Europeans in the early 1800s, is still widely used. After the components of silver amalgam (silver, tin, mercury) are mixed, the material slowly hardens. During its initial soft stage, it is placed into the cavity produced by the removal of decay. As the amalgam hardens, it is carved to the proper contour to restore the tooth. Newer filling materials made of plastic polymers are becoming more widely used. Once used only in non-stress areas in the front part of the mouth, they are now being utilized in posterior chewing areas. They have an advantage over metal fillings in that the color can be matched to the surrounding tooth and the material can be chemically bonded to tooth structure. Ongoing technological advances improve aesthetic restoration of teeth infected by dental decay while maintaining and protecting unaffected areas of the teeth. Tooth Restoration Gold and porcelain have been used for restoring tooth structure utilizing "lost wax" techniques of casting. These restorations use a precise set of techniques to prepare the cavity in the tooth, take an impression, and make a plaster of Paris "positive" mold. This mold is used to prepare a second mold constructed of wax. The wax in this mold is replaced by molten restorative material and the resulting restoration is secured into the cavity by a dental adhesive. New advances in computer-assisted technology can now produce gold and ceramic restorations. After the decay is removed from a tooth, a video scanner records the anatomical details of the cavity area. This information is electronically transmitted to a milling machine, which then produces an exact restoration for the cavity. Tooth Decay Important changes have occurred in the incidence of dental decay during the past two decades. Several preventive dentistry approaches were initiated in the 1960s. Among the most effective of these was the use of fluoride, through topical application with toothpastes and gels, dietary supplementation, and water supply augmentation. The last has been a controversial procedure. Some consumer advocates worry about potential adverse health risks associated with fluoride in water (see \Tfluoridation\t). Despite the controversy, however, the use of fluoride has resulted in a 50 percent reduction of dental decay in adolescents and young adults during the 1970s and 1980s. Between 1970 and 1980 the percentage of children in the United States under age 12 who were decay-free rose from 30 percent to almost 50 percent. The use of dental sealants, plastic material that is flowed into the decay-prone grooves in children's teeth, has also helped to reduce the incidence of adolescent tooth decay. While dental decay is still a significant problem, the decline in decay rate has allowed the dental profession to expand its activities and devote more attention to other aspects of oral health and disease. DENTAL EDUCATION IN THE UNITED STATES Early dental education in the United States consisted of a preceptorial system whereby dental practitioners would, for a fee, pass on their knowledge to students of the profession. In 1840 the first organized dental school, The Baltimore College of Dental Surgery, was established with a more formalized curriculum. Most dental schools established during the late 1800s and early 1900s were established as private, profit-motivated, proprietary schools. During the 1920s, the Carnegie Foundation commissioned William J. Gies to complete a comprehensive evaluation of dental education. The "Gies Report" initiated the total merger of dental education into universities and the higher education system. Today, there are over 50 dental schools in the United States, each formally associated with a university system. Applicants to dental school must complete at least two years of college education, and many complete their college degree prior to applying to dental school. Dental education consists of a four-year curriculum, the first two years emphasizing the basic biological sciences and training in dental technology. The latter two years focus on delivery of oral health care. All United States dental schools are accredited by the American Dental Association, assuring that basic components of curricula and educational programs are equitable. Upon successful completion of the curriculum, the student earns the degree of Doctor of Dental Surgery (D.D.S.) or Doctor of Dental Medicine (D.D.M.). These degrees are equivalent in all aspects of training and professional recognition. Dentistry has eight recognized specialties: dental public health, which focuses on preventing and controlling dental diseases and promoting dental health through organized community efforts; endodontics, devoted to the treatment of the tooth's pulp (nerve) and root end; oral and maxillofacial surgery, committed to tooth removal and surgical therapy of oral abnormalities; oral pathology, concentrating on diagnosis and treatment of pathologic conditions affecting the oral cavity; orthodontics, devoted to utilizing braces to correct tooth alignment; pediatric dentistry, concentrating on dental problems of children and adolescents; periodontics, focusing on diseases of the tooth's supporting structures (gums and bone); and prosthodontics, devoted to the replacement of missing teeth. Demographic needs and modern technology have resulted in development of new therapy approaches that cross specialty boundaries. For example, replacement of missing teeth has traditionally been accomplished by the placement of artificial structures that attach to remaining teeth or rest passively on the area where teeth have been removed. A better understanding of bone healing and biocompatibility has enabled the development of dental implants, metal inserts that are submerged into the jawbone (see \Tdentures\t). Implants may be used to support artificial teeth or prostheses to replace oral structures missing because of trauma, developmental anomalies, or pathology. Successful placement of dental implants, restoration with prostheses, and continuing maintenance require the multidisciplinary skills of the general dentist, the periodontist, the oral and maxillofacial surgeon, and the prosthodontist. As an increasing percentage of the United States population is living longer, it is obvious that preventive dental practices of earlier decades are paying dividends. In 1962 over 35 percent of 60-year-olds in the United States were edentulous, that is, their teeth were removed due to decay or periodontal diseases. In 1985 only 15 percent of this same age group was edentulous. As people live longer and maintain their natural teeth, the need to completely understand the relationship between oral conditions and other aspects of aging is becoming increasingly important. Dental students are now being exposed to educational programs with greater emphasis on the biological, pharmacological, and social needs of the older patient. DENTISTRY IN THE FUTURE Biotechnical advances will significantly improve future dental care. Not only will better materials with which to restore and replace teeth continue to evolve, but other technological advances will continue to allow dentistry to provide earlier and more accurate diagnosis and better treatment in a less costly manner. For instance, the recent identification of early inflammatory products of the cell and purification of various biochemical growth factors will permit the means to identify and stop progression of infectious diseases that destroy oral tissues, as well as allow the regeneration of lost tissue. Diagnostic techniques, ranging from biotechnical analysis of specific oral bacteria to imaging technology involving magnetic resonance and computer assistance, will allow more accurate and earlier detection of pathologic change. Laser technology to eliminate small areas of diseased tissue or actually weld damaged tooth structures will soon become commonplace. The delivery of dental care within the United States is also undergoing change. Traditionally, dentists have practiced independently in solo office environments. As knowledge and technology expands, there is an increasing tendency for dentists to enter into partnership or group arrangements so that expertise and costly equipment can be shared. These arrangements also allow more efficient use of facilities and auxiliary personnel. The importance of dental therapy for patients with impaired resistance to infections from chemotherapy, organ and bone transplantation, or immunodeficiency diseases has prompted dentists to enter the medical environment and many now provide specific care in medical clinics and hospitals. Kenneth L. Kalkwarf, D.D.S. Bibliography: Brunelle, J. A. and Carlos, J. P., "Recent Trends in Dental Caries in U.S. Children and the Effect of Water Fluoridation," Journal of Dental Research, vol. 69 (1990); Glenner, R. A., David, A. B., and Burns, S. B., The American Dentist (1990); Suddick, R. P., and Harris, N. O., "Historical Perspectives of Oral Biology" in Critical Reviews in Oral Biology and Medicine, vol. 1 (1990); U.S. Department of Health and Human Services, Oral Health of United States Adults (1987).