Dr. Lysle E. Johnston, Jr., on Orthodontics and the Scientific Method
DR. WHITE In the November 1990 issue of the British Journal of Orthodontics, you published an essay entitled "Fear and Loathing in Orthodontics: Notes on the Death of Theory". Why do you feel respect for scientific theory and the scientific method has been put on the back burner by orthodontists?
DR. JOHNSTON Because it is possible to practice orthodontics and survive without theory. The common impression that theory is unimportant, along with a short-term message that doing things in the "appropriate" way will keep you out of court, have essentially divorced orthodontics from any convincing theoretical basis.
DR. WHITE What are some specific clinical effects of responding to proprietary science?
DR. JOHNSTON Perhaps the major effect is a revolution in orthodontics without any perceptible basis in the literature. We are used to speaking of such changes as "swings of the pendulum", as if that were a natural phenomenon. Whatever the cause, the orthodontics that is being practiced in some parts of the country in 1993 would be recognizable to the orthodontist of 1893, but totally foreign to the orthodontist of 10 years ago. You have extraction, bite jumping, and bone growing of various kinds all competing for the clinician's attention cheek by jowl with carefully bent wires and a variety of older virtues.
DR. WHITE Why do you think there is such a rush for dentists to endorse and practice procedures that have proven so ineffective over the years?
DR. JOHNSTON From a practical standpoint, they are not entirely ineffective if patients come to the office. Moreover, when the literature declares a technique ineffective, it is often after many years of apparently successful use. For example, when Tweed decided that expansion was no good, it was after years of expanding every case ad libidum. Nowadays, our experience comes from a more conservative era; we are just starting to expand once again. Our experience is short-lived. We haven't yet seen anything close to what Tweed saw. But in about five or 10 years we will have, and it's my guess that we will find that there are no new biologies; we will find that expansion is still unreliable.
DR. WHITE It seems orthodontists' diagnoses and treatment plans are being second-guessed more by general dentists than ever before. Do you have a strategy for dealing with this problem?
DR. JOHNSTON Not really. I suppose--and this is really no strategy--you should continue to do what you feel is right and try to resist as professionally as possible pressures that you feel are inappropriate. It is probably a minority of dentists who are critical. If we decide to mount a general counterattack, we risk alienating the "good guys". Instead, we should try to cultivate the 70% who value us and try to resist the 30% who don't and whom we can't placate.
DR. WHITE The temporomandibular joint has been a particular bone of contention lately within the profession. Why has such controversy arisen about a subject dentistry was hardly interested in for a hundred years?
DR. JOHNSTON It is probably a busyness problem that has caused people to become interested in things like the temporomandibular joint, although there have always been factions in dentistry--for example, the gnathologists--that have been interested in this sort of thing.
DR. WHITE Is scientific research in the orthodontic disciplines being compromised by cynicism vis-a-vis the traditional orthodontic therapies?
DR. JOHNSTON I think cynicism is corrupting everything. I suppose it goes back to the first question--the realization that you can survive in practice on almost any philosophy with almost any kind of treatment. People are left with the idea that the only thing that matters is the right slot size and the appropriate archwire, an attitude that would reduce orthodontics to a purely technical trade.
DR. WHITE The retraction of incisors has been blamed recently by many dentists as a cause of TMJ dysfunction. Is this a viable criticism?
DR. JOHNSTON In terms of science, it is not a viable criticism. There is no evidence that incisor retraction routinely "distalizes" the condyles, nor is there any evidence that condylar position is, in any event, a cause of temporomandibular joint dysfunction.
DR. WHITE There has been some interest lately in the removal of maxillary and mandibular second molars as a way of relieving anterior crowding. Has this proven to offer much relief for arch-length discrepancy?
DR. JOHNSTON A student of mine, Dr. Michael Habern, studied the results of second molar extraction in sagittal appliance therapy. He found that second molar extraction, if I remember correctly, only produced about a millimeter or so of extra space. In truth, I can't really understand why people think that second molar "replacement" is a good idea, especially in the mandibular arch. Obviously, the occasional extraction of upper second molars will help you get some extra distal movement of the first molars; however, that is a far cry from four-second-molar extraction as a universal cure for crowding. Frankly, I don't understand it.
DR. WHITE The surveys conducted by the Journal of Clinical Orthodontics over the past few years indicate the majority of orthodontists use some form of preadjusted bracket system. Do you feel this great professional endorsement is warranted?
DR. JOHNSTON I think it is warranted. Larry Andrews's basic arguments have always impressed me. He said that if he had to go from New York to a house in Los Angeles, he would take the airplane to get to the neighborhood of the house, and then take a cab to get the rest of the way. He argued that the straightwire appliance was the equivalent of using the airplane to get you into the vicinity quickly and efficiently, and then individual adjustments would get you the rest of the way to the ideal positions. The problem is that I think the straightwire appliance fosters in some people the idea that some of the old skills of orthodontics are no longer needed--the ability to bend wire and the ability to put brackets on properly.
DR. WHITE Many of the straightwire systems have quite differing tips, torques, and angulations. Yet skilled practitioners seem to consistently get good results with different appliances. How do you explain this?
DR. JOHNSTON I suppose bracket tolerance and skill may be the answers. If you use a wire that doesn't fill the slot and you can bend wire, chances are you can use almost any prescription and make it work.
DR. WHITE How do individual tooth positions and tooth morphologies limit the current preadjusted appliances?
DR. JOHNSTON There is an excellent St. Louis University thesis done by Dr. Jim Bill Morrow (Abilene, Texas) in which it was demonstrated that the facial surfaces of the teeth are sufficiently variable that the only way to use a given prescription is to be prepared to do some adjustment. Many of the prescriptions, as you know, are very different, both from one another and from the actual facial surfaces of the teeth. But if you incorporate some "slop" in the bracket and can bend wires, anything could work.
DR. WHITE What kind of bracket do you see evolving for orthodontics over the next decade?
DR. JOHNSTON I have no idea. If I had any expert grasp of this topic, I would be a captain of industry, not a seedy academic.
DR. WHITE Recent studies show that ceramic brackets have some serious limitations such as increased friction, fragility, and dangerous adhesion to the enamel. What kind of future do you see for these brackets?
DR. JOHNSTON I think that bonding and debonding will be improved and also, with greater experience, people will learn where they should be used and where they shouldn't.
DR. WHITE A few years ago there was an enormous interest in lingual appliances. Lately, that interest has waned. What kind of future do you see for lingual orthodontics?
DR. JOHNSTON I suppose, like so many things, it is just another tool-- another arrow in the quiver. There will always be, I suppose, a small number of people who have a real need to have their teeth straightened with "invisible braces". I don't think it ever will be a very large number, however. Instead, I see the popularity of lingual orthodontics declining to a low, stable equilibrium point.
DR. WHITE What do you see as the role of functional orthodontics?
DR. JOHNSTON As with lingual orthodontics, I think "functional orthodontics" will find a non-controversial equilibrium point. Contrary to what people might assume, I don't think that functional appliances are bad. In fact, for people practicing in areas where the climate of opinion demands early treatment, they may well be preferable to alternatives such as serial extraction.
DR. WHITE Do you feel that, in fact, we can grow mandibles, or is the growth we see simply an acceleration of normal growth during the time of therapy?
DR. JOHNSTON I think that argument is essentially a straw man. Yes, I think we can grow mandibles; however, the problem is that the amount is probably very limited. I would be willing to wager that if you use a functional appliance on the next "N" patients you see and use it properly, you will pick up about a tenth of a millimeter of extra mandibular growth a month. On some patients more, on some patients less; however, you won't be able to predict which. An extra millimeter and a half or two millimeters is not trivial, but by the same token it is not a revolution in orthodontics, and it's not a substitute for surgery or bands and archwires.
DR. WHITE Referring to the research done at the University of Washington by Riedel and Little, post-treatment retention seems to be a continual problem for orthodontists and their patients. How do you think orthodontists should respond to this challenge?
DR. JOHNSTON There should be more people studying treatment and retention than one group in Washington. It is clearly within the reach of everybody to take cephalograms and models on their patients. In any event, I think orthodontic treatments may well be somewhat more stable than Little and Riedel have reported. That is my opinion; however, it would be handy if other samples and treatments were subjected to long-term scrutiny.
DR. WHITE There seem to be so many contradictory cephalometric analyses. What suggestion would you make for those who want to make their cephalometric analysis more accurate and effective?
DR. JOHNSTON Learn to locate landmarks; spend time on the technical details; then pick any common analysis. My experience from teaching cephalometrics for 20 years or so is that most tracings are clearly wrong. The landmarks are wrongly placed and the measurements are often crudely executed. No wonder the resulting numbers don't seem to bear any relationship to anything. So my advice is to be technically adept and precise, and then take any analysis and use it.
DR. WHITE Do you think we are wasting our time and effort drawing so many lines and measuring so many angles? Could that time be better spent, perhaps, by using templates such as those developed by you or Jacobson or the Bolton studies?
DR. JOHNSTON I think templates are fine; however, I wouldn't necessarily argue for templates over tracings. Whatever it is you decide you want to get out of a cephalogram, it should be technically reliable and it should have meaning. Whether that meaning comes from a well-executed measurement from a tracing or from a well-superimposed template is immaterial. Either way, you have to want something more from the cephalogram than an opportunity to write down some numerical answers to questions formulated by people who have been dead for 20 years.
DR. WHITE Is there any particular article or book readers could refer to for more information about using templates?
DR. JOHNSTON You can go back to Popovich and Grainger1 or to the literature coming out of the Burlington Study in Canada.2 The 20th Anniversary Issue of the JCO has an article on templates,3 as does Jacobson and Caufield's cephalometrics text.4
DR. WHITE What role do you see for video imaging?
DR. JOHNSTON Video imaging perhaps has heuristic significance, but as an actual prediction tool, its ability to account for individual variability is limited.
DR. WHITE Do you envision some type of three-dimensional cephalometric or video imaging for diagnosis and treatment planning, and how would it be useful for practicing orthodontists?
DR. JOHNSTON I can imagine 3D imaging, but I am not too sure it would be useful. People are fond of saying that a cephalogram is a three-dimensional image compressed into two dimensions. It sounds good, but the original Broadbent-Bolton cephalometric technique featured an "orientator", a template that enabled you to orient the lateral and P-A cephalograms to study things in three dimensions. Few thought it worthwhile, and few have used it. I am sure that when three-dimensional computerized cephalometrics comes along, if the pictures are pretty, people will use it; however, it is a logical fallacy to argue that something is useful merely because it is used.
DR. WHITE A few years ago, the prediction of growth during treatment was a hot topic. Why do you feel that subject is not often emphasized now?
DR. JOHNSTON Because it doesn't work and probably can't work. By and large, the errors of cephalometric technique, weighed against the size of the thing we are trying to predict, make it highly unlikely that we will ever be able to predict the small unknown increment of change. Remember, the thing we are trying to predict is future growth, not the future shape of the face or the future size of the face, but just the change from the present time to some time in the future. I think it's silly to assume that from four or five shadows on a cephalogram, you can divine how the face is going to grow in the future. In my opinion, it would be remarkable if chaos theory, information theory, and the limited information available from a cephalogram would allow you to predict individual growth.
DR. WHITE How important are patient growth spurts to the practicing orthodontist, and how can they realistically capitalize on these growth spurts?
DR. JOHNSTON "Growth" is a field in which orthodontists have always taken a proprietary interest. Differential growth makes a marked contribution to the orthodontic correction. Growth and growth spurts are thus important, and we capitalize on them by treating at times when growth is most likely to occur. Unfortunately, it has never been demonstrated that the use of hand-wrist films enables you to tell specifically when an individual growth spurt is going to occur. One would probably be better off betting on the average: that a growth spurt will occur at 10-12 years in females, 12-14 in males. If you are treating roughly during these intervals, you will be helped by the growth spurt, because in most cases the pattern of facial growth is favorable for the correction of Class II malocclusion.
DR. WHITE Academicians often criticize proprietary courses in orthodontics, yet some of these courses have afforded orthodontists training and information they haven't gotten in their graduate training. What future role do you see for proprietary courses for orthodontists, or for general dentists in orthodontics?
DR. JOHNSTON The marketplace will determine their role. If they can be sold, they will survive. In the end, however, this is a question for philosophers. It's an old argument: "If I don't do it, somebody else will do it and they'll do it worse." Just because a sizable group of people in dentistry want a certain kind of instruction, I don' t think it necessarily means that orthodontists are duty-bound to provide it.
DR. WHITE Anecdotal dentistry has often been faulted for steering people to erroneous conclusions, but treatment effects are important to the practicing clinician. What are your recommendations for dealing with anecdotal clinical information?
DR. JOHNSTON Anecdotes are just filtered experience. It seems to me that anecdotes--uncontrolled experience--can be a valuable source of hypotheses, but certainly not a source of final answers. If a person tells me that every time he does a two-jaw surgery he gets condylar resorption, that's not a finding. It is a potential hypothesis that we can test.
DR. WHITE Do you see a need for university orthodontic programs to expand to three or four years?
DR. JOHNSTON Obviously, all things being equal, longer is better. You can teach more, you can see more cases through to the end. But by the same token, the argument for extra time implies that students have no capacity to learn when they get out; that learning can only take place in the university. I feel strongly both ways. I currently run a three-year program. For 20 years before that, I ran two-year programs. We can make use of the third year, but without a firm resolve to make proper use of the extra time, all we can say about a three-year program is that it is surely a year longer.
DR. WHITE Do you feel our university programs are preparing orthodontic graduates for problems of managing a modern orthodontic practice?
DR. JOHNSTON We're trying. We develop seminar series and courses in practice management. We bring people in from the outside. I suspect, however, that there is no way we can really prepare people for the practice of orthodontics, any more than we can prepare our children for life.
DR. WHITE How are our university dental programs preparing their graduates to conform to the new OSHA mandates?
DR. JOHNSTON The universities are instigating training programs designed to bring all the faculty, all the staff, and all the students up to speed and at the same time, to document that we have met the OSHA requirements.
DR. WHITE What research programs would you like to see undertaken within the next 10 years, and how do you think they would affect dentistry?
DR. JOHNSTON I'd like to see orthodontics take an interest in what it is doing. I'd like to see us look at the long-term impact of the various kinds of treatment that are currently competing for attention. When some people are extracting bicuspids and some people are expanding and some people are jumping the bite and some people are extracting second molars, it seems to me that all of these approaches can't simultaneously be right. Orthodontics, however, is not nuclear physics: we can look at what we do and find out what works and what doesn't. I would really like to see orthodontists take an interest in the long-term impact of what they do and pay attention to the results.
DR. WHITE Many people have endorsed the idea of an expanded undergraduate curriculum in orthodontics, but from talking with recent graduates from several dental colleges, I receive the unmistakable idea that undergraduate orthodontic education is a hoax. How do you think the profession should address this educational deficit?
DR. JOHNSTON It is not certain that there is an educational deficit. By and large, orthodontic programs are attempting within the space available in the curriculum to teach something meaningful about orthodontics. It is obvious that, when students rotate through the orthodontic department in two-week blocks, it is very difficult for them to learn much of anything about a treatment that takes two to three years. Secondly, from our experience in teaching undergraduate students, it is very difficult for orthodontics to compete with operative requirements, denture requirements, crown and bridge requirements, and the like.
DR. WHITE Is there anything you would like to add to this interview?
DR. JOHNSTON I am concerned about the lack of people going into orthodontic education. I believe it is not because of the income differential, which is perhaps less than it was 30 years ago. Instead, I think young people no longer perceive orthodontics as being an important intellectual calling. They see it as a technical field that enjoys certain advantages over general dentistry--it pays better, the hours are better, the patients don't hate you, there is no pain, you are respected, etc. But in the old days, I think orthodontics was intriguing because people found it a thinking person's calling and felt that it rendered an important service. I suppose if we could get our science straight and then take it seriously, orthodontics would be a lot better off. It might even bring back the "golden era" that always seems to have died just before we entered the field.
DR. WHITE Thank you for sharing these insights with our readers.