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Pathology => Anatomy => Teeth
Teeth
INTRODUCTION
Dentistry, practice of preventing and treating diseases of the teeth, gums, and tissues of the mouth. Unlike other human tissue, such as skin, that continuously grows and self-rejuvenates, dental structures generally cannot repair themselves and require regular care to retain their health and vitality. If not treated, dental health problems can lead to complications in other parts of the body. Thorough and timely dental care is not only important for maintaining healthy teeth and gums, it is essential to overall human health.
Dentists and dental hygienists are health care professionals trained and licensed to provide dental care. General dentistry emphasizes treatments that prevent oral health problems, especially dental caries, commonly called tooth decay. Tooth decay is one of the most prevalent diseases in the United States, second only to the common cold. Dentists help prevent tooth decay by cleaning teeth to remove buildup of calculus, or tartar, which forms when plaque, a sticky film of bacteria, hardens on the teeth. As they feed on sugar and food residue on the teeth, the bacteria produce acids. If not removed regularly, these acids eat away the tooth enamel, leaving decayed holes in the teeth called cavities. To help prevent cavities, dentists apply fluoride (a mineral that strengthens tooth enamel) to teeth. Dental sealants-clear plastic coatings that are brushed onto the chewing surfaces of molars-are also effective in preventing tooth decay.
During a dental checkup, dentists take X rays of teeth and perform physical examinations to look for the presence of tooth decay. If a tooth is found to have a cavity, dentists use a high-speed drill to remove the decayed part of the tooth and then fill the cavity with gold, porcelain, plastic, or a mixture of silver and mercury called amalgam. Dentists usually fill cavities while the patient is under local anesthesia. The use of an anesthetic, such as procaine (marketed under the brand name Novocain) or lidocaine (marketed under the brand name Xylocaine), numbs the area of the mouth where the dentist is working, reducing the patient's pain and discomfort.
If tooth decay is not caught in time, it may reach an interior portion of the tooth called the pulp, where it can cause pain and infection. To correct this problem, dentists perform a procedure called root canal therapy, during which they remove the pulp, replace it with artificial material, and cement a crown-a toothlike cap made of plastic, porcelain, or gold-onto the damaged tooth.
If tooth decay is severe, a dentist may need to extract the tooth and replace it with a bridge, also known as a fixed partial denture. This artificial tooth replacement covers the space where one or more teeth have been lost. To attach a bridge, a dentist cements the fabricated tooth to adjacent teeth to anchor it in place. More and more often, dentists and patients elect to use tooth implants instead of dentures or bridges. A tooth implant is an artificial tooth that is surgically attached to the jawbone. An anchor is embedded in the jawbone, and after the surrounding gum tissue and bone has healed from the surgery, a post is attached to the anchor. An artificial tooth made of porcelain, metal, or plastic is fixed to the post.
DENTAL SPECIALTIES
A growing number of dentists specialize in one or more particular areas of dental practice. Dentistry has eight recognized specialties: general dentistry, periodontics, endodontics, oral surgery, prosthodontics, orthodontics, pediatric dentistry, public health dentistry, and oral pathology. In most communities, general dentists and specialists establish close working relationships with each other. General dentists manage the overall dental health of a patient, develop the initial treatment plan, and refer patients to a specialist when more specialized treatment is required.
Periodontists specialize in problems associated with gums and the bone that supports the gums. Gum disease, also known as periodontal disease, is one of the most common oral diseases and one of the greatest causes of tooth loss in people over the age of 21. Gum disease occurs when bacteria in the plaque that causes tooth decay attacks the gum tissue around a tooth, creating pockets between the tooth and gums. These pockets become repositories for harmful bacteria. Periodontal disease usually starts as gingivitis, a mild form of gum disease that causes gums to become red, swollen, and bleed easily. In its early stages, gingivitis can be eliminated by brushing and flossing daily to remove plaque. If not treated, gingivitis can progress to periodontitis, a more serious condition of the gums that occurs when bacteria attack the bone and tissue supporting the teeth. Periodontists treat gum disease with root planing and scaling, a treatment in which the periodontist pulls back the gum tissue and uses specialized scraping tools to remove the harmful bacteria.
Endodontists perform root canal therapy on teeth in which the pulp has decayed and must be removed. If teeth become hopelessly diseased, they may have to be extracted by oral surgeons, who are trained to surgically extract teeth and perform advanced surgical procedures. When a person loses several teeth or entire sections of teeth, false teeth known as dentures must be fabricated to enable that person to chew and eat. Prosthodontists specialize in creating and inserting prosthodontics, or dentures, tooth implants, and other types of artificial dental structures such as crowns or bridges.
Orthodontists correct unsightly crooked teeth or poorly aligned teeth that cause problems with biting using orthodontics-special wires, brackets, and bands commonly known as braces. A growing area of dental treatment is esthetic, or cosmetic dentistry. Bonding and veneers (tooth-colored materials used to cover stained or misshapen teeth) as well as tooth bleaching are used to improve the appearance of teeth.
Pediatric dentists have special training in children's oral health problems such as tooth decay, early orthodontic care, and dental injuries, and they receive training on the behavior of children. Special care is taken to make dental visits positive experiences. Public health dentists administer many government dental programs and promote dental health through organized community efforts. For example, public health dentists may administer school-based dental sealant or fluoride programs designed to ensure that public school students receive regular preventive dental care. Public health dentists may also be involved in research and teaching. Oral pathologists study and research the causes and effects of diseases of the mouth.
THE PROFESSION
According to the American Dental Association (ADA), the primary professional organization of dentists, there are 163,000 licensed dentists practicing in the United States. Nine out of ten are in private practice. Others work in alternative settings such as military and civilian hospitals, dental schools, and public clinics. More than 20 percent of dentists are specialists, and nearly 50 percent of all specialists are in orthodontics and oral surgery.
In order to practice dentistry in the United States, dental students must complete a four-year course of study at one of the 55 accredited dental schools in the United States, nearly all of which are affiliated with universities. Applicants must have at least two years of general college education and most dental students complete a four-year college degree before they are admitted to dental school. Dental students follow a curriculum that focuses first on basic biological sciences and training in dental technology, and later on oral health care.
Licensure begins after the second year of dental school when students take the first part of the National Board Dental Examination. The second and final part of the examination is usually taken during the last year of school. After successfully completing this exam and graduating from dental school, dental graduates must then take an exam administered by the state in which they intend to practice.
Together with dentists, dental hygienists and dental assistants make up the team that provides dental care to patients. Hygienists record patient medical histories, such as blood pressure and pulse. They clean teeth, apply sealants and fluoride treatments, teach patients sound oral hygiene practices, and often assist with X rays. Many hygienists receive a two-year associate degree, while others may choose to enroll in a four-year program at a university or in a master's degree program. There are 225 dental hygiene programs and 100,000 active dental hygienists in the United States.
Dental assistants may also take X rays and patient histories. Typically, they sterilize dental instruments, make impressions of a patient's teeth for record keeping, perform office management tasks, and communicate with patients and equipment suppliers. There are more than 200,000 dental assistants working today. Many begin their careers without specialized training, but most attend a dental assistant program at a community college, vocational school, technical institute, or university before entering the field.
Most dentists in the United States belong to the ADA. This professional organization lobbies the Congress of the United States to fund dental research and education; sets ethical and professional standards for practicing dentistry; accredits dental schools and training programs for dental assistants and hygienists; and provides consumers and dentists with a guide to safe and effective dental products.
IVHISTORY OF DENTISTRY Diseases of the teeth and gums have troubled humans for thousands of years. Ancient Egyptian medical texts, dating back to 3500 BC, refer to toothaches. The earliest record of dental treatment also comes from Egypt, where gum swelling was treated with a concoction of cumin, incense, and onion. The earliest known dentist was Hesi-Re, an Egyptian "doctor of the tooth" who lived around 3000 BC. There is evidence that toothaches were treated with acupuncture in China as early as 2700 BC. By AD 659 the Chinese were filling cavities with a mixture of mercury, silver, and tin, nearly 1000 years before amalgam was first used in Western countries. Some cultures, such as the Maya, did not treat disease but decorated their teeth with stone and metal inlays for ornamental purposes.
Romans were known to be conscientious about their oral hygiene-it was common for dinner guests to be given gold picks to clean their teeth. As early as 450 BC Romans treated toothaches, filled cavities, and fashioned bridges to replace extracted teeth. In the 3rd century BC the Greek physician Diocles advised fellow citizens to rub teeth and gums with pulverized mint to remove particles of food. The Greek physician Galen, who settled in Rome during the 2nd century AD, advocated the use of a file to remove decayed portions of a tooth.
During the Middle Ages, from the 5th to the 15th century AD, dentistry in Europe was practiced by barber-surgeons. These professionals served the townspeople by performing a wide variety of services including cutting hair, extracting teeth, and applying leeches to let blood, a practice once believed to cure a variety of ailments. In the late 14th and early 15th centuries a number of rapid-fire developments dramatically improved the quality of dental care. For example, during this time surgeons and anatomists in France, Belgium, Italy, and Germany developed an improved understanding of tooth anatomy, introduced the use of gold for fillings, and commonly used materials, such as wood, to replace extracted teeth.
It was not until French dentist Pierre Fauchard published his influential work The Surgeon Dentist in 1728 that dentistry began to take its modern form. Fauchard, now recognized as the father of modern dentistry, was the first person to provide a comprehensive and organized treatise on dental science for fellow practitioners to use. His work played a key role in enabling the specialty to break away from medicine and establish itself as a distinct, scientifically based profession.
The 19th century witnessed several developments that revolutionized the field. Organized dentistry began in 1840 when the world's first dental school, the Baltimore College of Dental Surgery, opened in Baltimore, Maryland. The use of general anesthesia in dentistry began in 1844 when Connecticut dentist Horace Wells first used the chemical compound nitrous oxide, commonly known as laughing gas, to relieve pain during a dental procedure. Two years later, his former partner, William Thomas Morton, introduced the use of ether as a general anesthetic at a public demonstration. In 1858 American dentist Greene Vardiman Black invented the foot-powered dental drill, a novelty that enabled dentists to use both hands during drilling procedures.
In 1890 American biochemist Willoughby Dayton Miller showed that sugars in food residue on the teeth are broken down by bacteria, creating acids that damage tooth enamel, leading to tooth decay. Miller's work played a significant role in developing the rationale for what is known today as professional tooth cleaning. The invention of the X ray in 1895 by German physicist Wilhelm Conrad Roentgen enabled dentists to examine teeth for hidden cavities and decay.
Perhaps the greatest advance of the 20th century for dentistry began in the early 1900s when the small population of Colorado Springs, Colorado, was found to have low rates of tooth decay. It was discovered that the town's water supply contained fluoride, a naturally occurring element found in rocks and minerals. Public health researchers suggested that adding fluoride to the water supplies in cities all over the United States could dramatically reduce the incidence of tooth decay. In 1945 a water fluoridation program was begun in Michigan to test this hypothesis. Ten years later the test results showed that tooth decay in participating children was reduced by 50 to 70 percent. Despite the objections of opponents who fear fluoridation may have long-term adverse health effects, most of the U.S. water supply is now fluoridated. Although a controversial issue, numerous public and privately funded studies have confirmed the benefits and low health risks of water fluoridation, and fluoridation programs are endorsed by several national and international health organizations, including the ADA, the American Medical Association (AMA), and the World Health Organization (WHO).
The field of dentistry continues to evolve. When a woman in Florida announced in 1990 that she had contracted the virus that causes acquired immune deficiency syndrome (AIDS) from her dentist, dentists were forced to reexamine their infection control methods. While recommendations had been in place to prevent the spread of viruses that could be passed through blood-to-blood contact, a majority of dentists did not routinely follow them. Dentists now equip themselves with gloves, gowns, and masks during dental exams and routinely sterilize their instruments to provide appropriate protection for their patients.
New and emerging technology may change the way patients receive dental treatment. Today dentists make an impression of a tooth to make a bridge or partial denture, but computer aided design-computer assisted manufacturing (CAD-CAM) technology will enable dentists to scan the damaged tooth and transfer a three-dimensional image to the computer. The computer can precisely blueprint the image and physically construct the portion of the tooth necessary to restore it to its original shape. Lasers, which are used currently to treat diseased gums and other oral tissues, have recently been approved for use on teeth and may someday become an alternative to the dental drill.
Genetics and advanced biomaterials research will also significantly change dentistry in the future. One day saliva and tissue tests will use genetic techniques to detect the presence of oral disease-causing pathogens. Better materials with which to restore and replace teeth are already a reality-researchers have developed better methods to repair the bone that supports teeth, and, eventually, tooth implants may completely replace dentures.
In the United States, the aging population will have a profound effect on dental care. Population projections suggest that people age 65 and over will number 40 million by the year 2010, and with modern dental care, more of these people are likely to keep their teeth. Instead of the traditional practice of providing dentures for patients who lose their teeth, dentists of the future will be able to shift their focus to treatment of age-related oral diseases, such as advanced gum disease.
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