by Robert C. Frantz, DDS
To read Part 1 of this article, go to the August issue of Orthodontic Products
How has the development of Roth’s philosophy and its subsequent exposure to the orthodontic profession led to so much misunderstanding? What component is so controversial that many members of the orthodontic profession believe it incumbent upon themselves to denigrate or discount the methodology and techniques now promoted by the followers of Drs Roth and Williams worldwide? Is it possible that, given the opportunity, an interested individual might come to the conclusion that the philosophy has merit, and that the techniques have rationality? What follows is a short discussion of some of this methodology, and how it is applied. This is not meant as a comprehensive review of all techniques employed, nor a complete exposÉ of all procedures and methods. Since these are rarely taught in postgraduate orthodontic training, it will be left to the individual to seek this experience out if they so desire.
Seated Condylar Reference Position
The basic tenet of the philosophy is that the mandible is able to function at a position known as the Seated Condylar Reference position. While also known as Centric Relation, this term has been altered and redefined to the point that it causes more confusion than clarity. The use of a reference is important in all phases of treatment and is integral to the methodology employed. The studies of Gibbs and Lundeen7 have recently been compiled into a body of work that clearly shows the validity of the use of this position as a basis for planning and treatment. There is little doubt that the individual does not always (let alone constantly) use this reference position in the day-to-day functioning of the chewing system, but there is also little doubt that during the course of function (or parafunction), the individual is capable of reaching this position. It is this fact that the Seated Condylar Reference represents a border position, and is a terminal position during at least some of the chewing strokes, that makes its location and its use so valuable to the clinician.
Movement Pattern of the Dynamic Gnathic System
If the movement of the mandible relative to the maxilla is at least partly guided by the temporomandibular complex, and the teeth are best served by a movement pattern or scheme that produces the most favorable distribution of forces and the least amount of damage or wear to the system, then it would appear that the mutually protected occlusion has much merit. Positioning the teeth within this functioning matrix to achieve this occlusal scheme is the essence of “full-mouth reconstruction.” Unlike the restorative dentist, the orthodontist does not have the luxury of changing the tops of the teeth to fit the movement pattern and to achieve the goal of mutual protection. Understanding the borders of movement allows the clinician to accurately position the dentition in a manner that allows the teeth to pass over one another in a way that is not self-destructive.
Knowledge of the borders of the envelope of motion is required if one is to achieve this result. Many methods are available to measure this envelope, and the choice is open to the clinician. How this is achieved is not important, only that the knowledge be gained and implemented into the diagnostic and treatment schemes. To achieve this knowledge, experience has shown that a system that easily measures the jaw relationships, that allows observation of the movements of the dental arches across one another, and that has an acceptable level of accuracy with regard to the extent of the border movements and the movement patterns, is a valuable adjunct to the diagnosis and treatment-planning of an orthodontic case.
Today, that instrumentation exists in the form of the articulator and the ancillary instruments for measurement. While it is true that this instrument cannot duplicate the exact movements of the jaw, it is able—as shown by the research of many, Gibbs and Lundeen in particular—to simulate these movements at the level of the teeth in a manner to be useful to the clinician. No other technique is capable of capturing and making visible this movement pattern with the same ease and simplicity. If the neuromusculature of the individual dictates how movement will occur, and an unfavorable relationship exists so that the individual will attempt not to cause harm to himself, then being able to uncover and assess the problem is difficult at best. The articulator and casts mounted in the Seated Condylar Reference position offer the clinician the best opportunity to assess the true nature of the orthodontic malocclusion, and to devise a plan of correction.
It has been found that the position the mandible takes when placing the teeth into their best fit position (or ICP or Centric Occlusion) is learned, and if any impediments to easy, direct closure to this position exist, the proprioceptive inputs direct closure so as to avoid noxious contact. For this reason, it is difficult to detect the extent of a problem if the malocclusion is long-standing or the adaptations are complex.
- A diagram of movement over the molar occlusal surface.
One of the procedures often described is the use of a gnathologic repositioning splint. This plastic orthotic is used to cover the existing malocclusion, and to allow the clinician to establish an occlusion that is more compatible with a seated condyle and that does not involve any cross-arch interferences during function and chewing. That this orthotic requires adjustment and time to allow the muscles to seat the condyles into the reference position suggests that adaptation on the part of the host often occurs as a protective mechanism. While this adaptation may provide protection for the host in the short term, if having the complex functioning in an intact mode is more favorable and more stable, then achieving this at the conclusion of treatment is in the best interests of the patient. For this reason, if there is any indication that the patient has adapted to a position that differs significantly from the Seated Condylar Reference, the most prudent action by the clinician will be to fabricate such an orthotic and attempt to seat the condyle into the fossa with the intact disk interposed. This cannot be done by manipulation, and the extent of the adaptation that has occurred previously cannot be adequately viewed intraorally.
Fabrication of the orthotic is best accomplished in the laboratory, in the interests of time, accuracy, and efficiency. Once again, instrumentation allows this to be done. There may be other methods that achieve the same result, but using an articulator greatly facilitates accomplishing this task. Using an orthotic is integral to the diagnostic process, and unless the clinician is confident with regard to the Seated Condylar Reference position, there will always be some doubt as to what the true characteristics of the orthodontic problem are.
The goal of the diagnostic process of this philosophy is to minimize surprises that may occur during the treatment. To this end, extensive pretreatment records are obtained in addition to the mounted study casts. Much of what is accumulated is based upon clinical findings, but current studies have disclosed that many of the patients who seek treatment may have undiagnosed problems, and that often, additional information is required.
With the advent of CBCT and the availability of 3D information sets, the clinician has available much more information with less risk to the patient. Will this change the course of orthodontics, or will its use be limited to only a few cases? As resolution increases and dosages decline, this technology may quickly become the standard of care and supplant other forms of records.8 With rapid technological advances in the future, it is difficult to guess what is in store, but it is certain that additional information will only benefit the patient and decrease the risks of undiscovered complications. Traditional cephalometric and panoramic views will remain useful until the knowledge base allows the exploitation of the increased data sets. Integrating the new visualizations into traditional analysis will provide a challenge for the future that will not easily be met. It should suffice to say that the use of the mounted study cast with its inherent 3D format dovetails nicely with the new technology, and in the future, stone models may be replaced by digital images, and movements on the articulator by graphic displays. To date, neither technology nor software have supplanted the information available to the clinician in the form of mounted study casts on an adjustable articulator. It also follows that no technique readily available in the past has been able to provide the clinician with the same set of diagnostic information. Change within orthodontics and the search for what is best for our patients is ongoing.
Once the data has been accumulated, then the diagnostic process may commence. All that has been learned about the patient is assembled, and a list of problems to be solved with treatment is formulated. While it may not be possible to achieve correction of all of the listed problems, their disclosure and the method of treatment is important to both the clinician and the patient. Ideal is a concept that is unachievable.9 Excellence of result for the individual patient may involve reaching what is optimal for the particular case. If you plan for this and disclose your plan prior to instituting treatment, then when you achieve your expected result, this may represent success. If you set an unrealistic goal and do not reach it with treatment, then both the orthodontist and the patient will be disappointed. Stating your goals in a manner that is measurable allows the orthodontist to provide the patient with an informed consent as well as a true picture of what the end-of-treatment result will be and when it will occur.
With achievable goals in mind, and an addressable problem list, the orthodontist is able to construct a detailed plan of treatment and a sequence of mechanics to reach these goals. This allows the practice to schedule in a precise manner and allows the orthodontist to treat by exception rather than rediagnosing the case at every visit. If the visual picture of the patient meets the expectations of the plan, then all that is required is to accomplish the task for the visit and to schedule the next planned procedure. Surprises are kept to a minimum, and deviations from the expected can be handled more rapidly and efficiently. It is in this instance that the Seated Condylar Reference becomes most valuable. If a problem exists and the solution is not readily available, returning to the reference allows the clinician to reassess the problem and replan the subsequent treatment in an efficient, thoughtful manner.
Since the case has been preplanned, and treatment is begun with the end in mind, then the conclusion of treatment becomes obvious. When the goals have been achieved, it is time to remove the appliance and complete the treatment. No longer is the conclusion of treatment questionable. If the patient has been compliant, and the orthodontist has been observant, then the expected completion date and the actual finish date should be very close. If a discrepancy exists, it will be disclosed well in advance, so that the expectations of the patient are kept realistic during the course of treatment.
Finally, since a reference was used in the beginning, and the treatment was planned with a known end in mind, it becomes a relatively simple procedure to measure whether the stated goals were achieved. This provides the orthodontist with a measurable tool by which to assess the results of treatment. By employing the same cybernetic approach used in the beginning of treatment, and by observing multiple results, the orthodontist has the opportunity to engage in “Studies of One.”10 By setting goals and then measuring what was achieved, the orthodontist becomes aware of what he or she is capable of achieving on a routine basis, and treatment planning becomes less and less of a mystery. In the end, it is the patients who will benefit. Utilizing realistic planning initially, and altering this with actual data, results in a practice that is under control and provides an expected service to its clientele.
- This is the second part of a two-part article; read Part I.
Those who have embraced this process have found the practice of orthodontics to be knowable and rewarding. To suggest that all orthodontists should practice in this manner would be unreasonable. To continue to listen to those who have attempted to discredit this treatment philosophy would do a disservice to those who have taught and gone before. Should the detractors or doubters wish to offer a different scheme, or create a different set of definable goals,11 then it will be up to the profession to evaluate their effectiveness and adopt them should they be found better. Until such explicit information is available, then respectfully, perhaps others should try this way and equal the results that have been shown, judged, and demonstrated by their peers.
Robert C. Frantz, DDS, has been in private practice in Danville, Calif, since 1973. He is one of three directors of the AEO Group of Roth-Williams USA. He can be reached at
- Lundeen H and Gibbs C. The Function of Teeth. Gainesville, Fla: L&G Publishers LLC, 2007.
- Jerrold L. Liability regarding computerized axial tomography scans. Am J Orthod Dentofacial Orthop. 2007;132:122-124.
- Girardot RA. Advanced Education in Orthodontics; Class Material
- Freeland TF. Advanced Education in Orthodontics; Class Material
- Turpin DL. The case for treatment guidelines. Am J Orthod Dentofacial Orthop. 2007;131:159.