Americans' teeth have improved markedly during the last three decades as a result of water fluoridation, regular brushing, better nutrition and the use of fluoride mouthwashes, dental floss and sealants. From 1980 to 1987, the proportion of U.S. children age 5 to 17 with no decay in their permanent teeth rose from 36.6% to 49.9%. Toothlessness among middle-aged adults declined from about about 8% 13 years ago to just 4% in 1985, according to the National Institute on Dental Research in Bethesda, Md.
Now, a second dental revolution--already under way--promises to build on these gains and make most procedures far less complicated, painful and time-consuming for the 133 million Americans who spend $33 billion annually on their teeth.
Scientists have identified the forms of bacteria in the mouth that cause decay and, using an array of new techniques, will be able to prevent major problems and treat those that occur much earlier than they do now. With new therapies, better materials and greater knowledge about controlling pain, dental care could become almost pleasant.
Since much preventive work will be simple and performed mostly by hygienists, general dentists will become "mouth physicians," said Dr. Harold Loe, the dental institute director. And while some contend that these new developments may put dentists out of work, others say there will be just as much work, only of a different type.
If preventive measures now on the drawing board work out, patients soon will be visiting the dentist less frequently for decay and more frequently for more serious conditions such as tumors and jaw-related problems.
One of the most promising approaches is under study at Boston's Forsyth Dental Center, where Jeffrey Hillman, a molecular geneticist, is developing a "good" strain of bacteria. He said this could eventually lead to a one-time mouthwash that would prevent cavities from ever developing.
Under normal conditions, certain strains of the bacterium Streptococcus mutans --believed to be the principal cause of tooth decay--sit on the surface of the tooth while sugar from food is metabolized to produce an acid that demineralizes the tooth surface and, over time, progresses into decay. Hillman's "good" strain of S. mutans would produce an antibiotic-like substance that attacks and kills off the "bad" strains and then establishes itself permanently in the mouth.
Hillman has found a strain that works for a relatively long time in animals but disappears after a month in humans. He is now using recombinant DNA technology to construct a strain that will permanently colonize the more complex system in humans and won't revert back to acid production and tooth decay.
Once completed, clinical trials involving many patients would begin. He said the recombinant has already shown some promise in animals but is probably five years from being ready for routine use in people.
When it's ready, a solution containing the bacteria would take five minutes to swab onto all tooth surfaces and probably cost less than $1. Said Hillman: "Ideally, it would be given once in a lifetime and patients would only have to go back to the dentist for cleaning."
A variation on this technique is also being developed to treat gum disease, which is responsible for bone loss in 77% of working adults between the ages of 18 and 64. Hillman admits that it has been difficult to find a strain that stays in the mouth for a long time, but believes he now has one that will be ready for human tests next year and on the market in five.
Dental researchers are also experimenting with novel ways to deliver fluoride and drugs to resist decay and gum problems. At the National Institute on Dental Research, chemist Dale Mirth has developed a pellet designed to be cemented to a tooth, slowly releasing fluoride for six months. The pellet actually consists of a fluoride solution packaged inside a permeable polymer membrane specially designed to release water-soluble drugs. Dental pellets have been constructed to release fluoride at a constant rate. Similar controlled-released systems have already been developed to treat glaucoma and as a contraceptive.
Such a system would be especially useful for handicapped people who can't brush regularly and those with braces, which prevent thorough cleanings. Studies show that the pellet can produce a 50% reduction in cavities in animals. Full-scale human tests could begin this fall and the pellet itself could be ready in five years at a cost of a few dollars apiece.