New Frontiers in Dentistry

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New Frontiers in Dentistry

Overview

After World War II efforts were concentrated in the public health and preventative aspects of dentistry. Communities began to fluoridate their water supplies. Regular dental examinations were encouraged, and dental hygiene efforts were expanded. Over the next half-century, technological improvements had major effects both on preventative services and reconstructive techniques.

Background

In the early twentieth century, most people went to dentists only when they had a toothache. As a result, one out of five World War II military recruits in the United States failed to meet the requirement that they have at least twelve teeth: three pairs of matching incisors and three pairs of chewing teeth. Dental problems were the most common reason for rejecting potential soldiers. Finally, the dental standards had to be eliminated altogether in order to fill the ranks.

After the war, improving the dental health of the population became a priority both in the U.S. and in Europe. Dental schools began devoting time in the curriculum to public health. The American Board of Dental Public Health was established in 1950, and the U.S. became a leader in this field. Scientific and technical advances were fostered by the establishment of the National Institute of Dental Research near Washington, D.C., in 1948.

One weapon in the war against dental caries (tooth decay) was fluoride. In the first decades of the twentieth century, people whose water supply had a relatively high concentration of fluoride ions were observed to have brown mottling on their teeth but rarely experienced dental caries.

The new field of dental epidemiology began in the 1940s with large controlled studies of fluoride in the water supply. These studies were conducted in Michigan, Illinois, New York, and Ontario. To provide a basis for comparison, Dr. H. Trendley Dean of the Public Health Service developed a measure called the DMF Index, taking into account decayed, missing, and filled teeth. Gradually, municipal water districts all over the U.S. began adding fluoride to their systems at about 1 milligram per liter, a level that does not discolor the enamel but reduces dental caries by approximately 65%.

Dentists were not alone in working to prevent tooth decay. At the turn of the century, Dr. Alfred Civilion Fones (1869-1938) had trained an assistant to thoroughly clean the teeth of children he saw in his practice. Later, he coined the term "dental hygienist" and established a training clinic. The first dental hygienist licensing law was put into place in Connecticut in1917. Many of the women who graduated from the early training programs were employed by school systems, and the children they served exhibited drastic reductions in cavities.

Impact

As dentistry became part of routine health care after World War II, the organization of dental practice changed. Many dentists began to specialize in a particular field. Orthodontists handle misalignments of the teeth and jaws. Periodontists treat gum problems. Pedodontics is the branch of dentistry concerned with children's teeth. Oral surgeons handle a wide range of procedures involving the teeth and jaws, including repair of birth defects and fractures.

The one-dentist office gave way in large part to the group practice, two or more dentists working together and sharing office facilities. Group practices have allowed extended hours to accommodate patients' busy schedules without making unreasonable demands upon the dentists' time. Often a group includes one or more specialists, allowing patients easy access to these professionals. Dental assistants work as an integral part of the team; "four-handed dentistry" makes coping with equipment and dental materials much more efficient.

The postwar period also saw the beginning of full participation in the dental profession by African Americans. After the 1880s almost all African American dentists had been trained either at Howard University in Washington, D.C., or Meharry Medical College in Nashville, both educational institutions founded to serve black students. The 1954 desegregation decision by the United States Supreme Court mandated access to all schools, and slowly the doors opened. In 1962 the American Dental Association, having established bylaws prohibiting racial discrimination, threatened to bar state chapters that refused to do likewise.

From the patient's point of view, another important change was the advent of third-party payer systems. Dental insurance plans are offered both on their own and as part of some medical insurance packages. During the 1960s and 1970s collective bargaining resulted in dental benefits being offered to the members of many unions. They can also be obtained through corporate and other group insurance programs, as well as on an individual basis. Most encourage preventative care by covering a variety of routine services such as examinations every six to twelve months, x-rays, and cleanings. In Europe several countries have instituted government-sponsored dental insurance.

Science and technology have provided important new tools for improving dental health. Once the effectiveness of fluoridated water was demonstrated, communities quickly responded. By 1962 more than 2,000 municipalities in the United States had added fluoride compounds to their water supplies. Fluoride was also added to toothpaste formulations during the same period. Today about 135 million people live in regions with fluoridated water, and others consume foods or beverages processed there. Dental caries in schoolchildren declined by about one third in the 1970s, and another third in the 1980s.

However, fluoridation is still not universal. In some areas vociferous opposition has prevented it. Concerns focus on such issues as whether excess fluoride tends to make bones more brittle, especially in the elderly. Fluoride supplements may be recommended for children in unfluoridated-water communities, in addition to those children who drink well water or bottled water.

In 1959 Dr. Frank J. Orlond of the University of Chicago uncovered the organism principally responsible for tooth decay, the bacteria streptococcus mutans. On a susceptible tooth, especially one owned by someone partial to sugary and starchy foods, these bacteria flourish. The acid they produce demineralizes the tooth surface. Understanding the decay process is crucial to finding more effective ways to prevent it. An anti-caries vaccine is a possibility for the future, as is genetically engineering a version of the bacteria that produces less acid. Meanwhile, plastic coatings, or sealants, are commonly painted on children's permanent molars as they come in, protecting their irregular pits and crevices for about five years.

Biomedical engineering has contributed knowledge of the mechanics of chewing. Miniature sensors can be fastened to the tooth surface to study jaw alignment, movement, and pressure. Others allow precise measurement of the degree of demineralization of the surface. Periodontists can employ tiny sampling devices to analyze fluid in the crevices between the teeth and gums. Gum disease is caused by several types of bacteria that, unlike Streptococcus mutans, are not generally found in the healthy mouth. By detecting these early, the dentist can treat the patient with antibiotics before permanent damage has been done. Lasers are now being used in periodontal treatment as well. In 1998 a "hard-tissue" laser was introduced, suitable for working on both gums and teeth.

Digital x rays, developed in the 1990s, are slowly finding their way into dentists' offices. They provide the ability to detect smaller changes, while exposing the patient to 75% less radiation. A matchbook-sized, plastic-covered sensor goes into the patient's mouth instead of the familiar "bitewing" film holder. With no need for film developing, the image can be displayed immediately on a screen and easily manipulated.

Despite the best efforts of preventative dentistry, repair and restoration are still sometimes necessary. In 1957 the S.S. White Company introduced high-speed dental drills, driven at 300,000 revolutions per minute by compressed air. The reduced vibration of the high-speed drills made them more comfortable for the patient, while at the same time providing increased control for the dentist. Today's dental drills are of the same basic design as the 1957 model. However, the handpieces can now be steam-sterilized, and they include fiber optics to cast light directly upon the working area.

Kinetic cavity preparation, in which pressurized microscopic aluminum oxide particles blast away the decay, is an alternative to drilling developed in the 1990s. It's faster and less painful, but the equipment costs about $18,000, so it will arrive in dentists' offices very gradually. It is also unsuitable for large cavities.

If the tooth is too damaged for simple cavity repair, more drastic measures are called for. In the 1960s crowns made of porcelain bonded onto metal were introduced. Earlier crowns were made of gold with an acrylic veneer, and the veneer would eventually wear away. With the porcelain and metal crowns, natural-looking, permanent restorations could be constructed. During the 1980s dental implants began to appear on the scene as an alternate to bridgework and removable dentures. Implants involve surgery to attach dentures directly and permanently to the jawbone. About 100,000 patients underwent the procedure by the early 1990s.

Dental plastics that harden when exposed to light or special chemicals were developed in the 1960s and 1970s. They are useful for cosmetic dentistry as well as restorations. Bonding procedures involve etching the tooth surface with a mild acid to create tiny irregularities onto which the liquid plastic will cling. The plastic can then be built up as desired, for example to hide an unsightly tooth, repair fractures, eliminate overly large spaces between teeth, or attach orthodontic brackets without metal bands. The material itself is generally a composite, with microscopic particles such as silicates for strength. Still, it lasts only about five years and can't stand up to very hard foods. Porcelain veneers, used when bonding can't produce the desired cosmetic result, last about twice as long.

SHERRI CHASIN CALVO