It takes about 25 to 30 years before a scientific theory becomes accepted. Paul Ehrlich developed the theory of chemotherapy for fighting infections between 1907 and 1910, but it was 25 years later when the sulfa drugs he invented were finally marketed. Penicillin, which was discovered by Fleming in the mid-1920s, would probably not have made it to the marketplace until the 1950s had it not been for World War II, which compressed the ordinary lead time. By 1918 all the scientific knowledge, mathematical concepts, and technical expertise needed to make a computer was available, but the first computer didn't become operational until 1946.
One often reads in consumer magazines about how much faster scientific theory is turning into techniques and products today, but this is largely a misconception. The 25-to-30-year lead time for knowledge to be put to use really hasn't changed much. No one knows why, but no doubt it has something to do with aversion to change. As Alvin Toffler has written, change brings stress and stress brings disease. Maybe our reluctance to change is Nature's way of protecting our systems from dangerous physiological overload.
Dentistry is not exempt from this lead-time phenomenon. For instance, one of the most innovative and exciting recent techniques is the bonding of composite restorative materials to dentin and enamel. Buonocore published this radical new concept in 1955. By 1970 some South African orthodontists were experimenting with an epoxy version of Buonocore's technique, and by 1975 several orthodontists were supplementing their ordinary banding techniques with some form of bonding. But dentistry in general didn't jump on the "bond wagon" until about 1980--25 years later.
In 1952, the Utah Orthodontic Study Group demonstrated how tipped brackets could obviate tip-back bends in archwires. Other orthodontists began to experiment with torque in anterior brackets, and in 1968 Andrews compressed these ideas, along with improved metallurgic casting techniques, into a complete Straight-Wire Appliance. By 1975 several hundred orthodontists were using some version of this appliance, and by 1980 a stampede toward the straightwire concept had started-- but only 28 years after its feasibility had been demonstrated by Holdaway and others.
Certainly there have been and will be exceptions to this 25-to-30-year rule. If someone should develop a cure for cancer or AIDS, the acceptance and immediate applicability would surely require less lead time. It's possible that a similarly shortened lead time may occur with another exciting dental innovation that is just beginning to be appreciated. Glass ionomer cement was first described by Wilson and Kent in 1972. There are several types of this cement being marketed, but the basic ingredients are an old-fashioned silicate powder and a polyacrylic acid.
Glass ionomer cement has many favorable features for dentistry in general and orthodontics in particular. It bonds chemically to dentin, enamel, cementum, nonprecious metals, and plastics. It doesn't require undercuts and interlocks ordinarily required with restorations. It releases fluoride ions and virtually eliminates caries and decalcification up to 3mm around the bonding site. It has low pulp irritation and low solubility after the initial set. It has a high compatibility with materials that can improve its strength, such as amalgam and acrylics, and it can be etched like enamel and covered with composite restorations. It can also be used as a sealant for pits and fissures. These characteristics have caused Dr. Joe Simmons of Dallas to call the amalgam variation a "miracle mixture". He may be right. At any rate, glass ionomer cement offers a much-needed improvement in restorative and cementation techniques.
Teeth don't have to be etched before the cement is used, and the absolute dryness we must have in ordinary bonding techniques is not necessary. In fact, too much dryness seems to weaken the bond, so the usual drying procedure is no more than a swipe over the tooth with a cotton roll. When a frozen glass slab is used for mixing, enough cement can be mixed to band or bond an entire dentition. There is ample time to adjust bracket heights, and bracket drift is seldom a problem.
For orthodontists and their patients, the most important benefit will be the reservoir of leachable fluoride ions that prevent caries and decalcification and inhibit the growth of bacteria associated with periodontal disease. Even if these unwanted consequences can be attributed to poor oral hygiene, neither doctor nor patient is pleased when they occur. Glass ionomer cements may be the best antidote we have ever had for the ravages of oral hygiene neglect.
According to the unwritten law of scientific innovation, we can expect most orthodontists to be using glass ionomer cements by the mid-1990s. It will be a shame if we can't compress this lead time--for the sake of our patients.