THE EDITOR'S CORNER
In the past few issues of JCO, some important observations have been made about cephalometrics. They bear repeating.
Dr. McHorris in an article in this issue says:
If one believes in the importance of centric relation of the mandible, then one should examine, diagnose, and treat with that objective in mind. If a discrepancy exists between centric relation and maximum intercuspation, and cephalometrics taken with the mandible in an eccentric position is used as a diagnostic aid, the validity of any analysis based on the resultant information must be considered untrustworthy. Cephalometric measurements that include the mandible can only be considered valid when the mandible is in centric. This is a sad realization when we consider the endless hours, days, months, years, and even decades of time devoted to cephalometric studies, establishing cephalometric norms, computerizing treatment objectives--and yet most of these studies were performed with an eccentrically positioned mandible.
Dr. Coben in this same issue says:
Many clinicians are unaware that a lack of standardization of enlargement in the taking of cephalometric x-rays creates erroneous clinical interpretation. Furthermore, because variable enlargement in cephalometrics exists throughout the profession, x-rays of transfer cases are not comparable and are of limited value. The profession must begin to realize that if it is to continue using cephalometrics as a scientific tool, the problem must be remedied.
Of course, if one's cephalometric requirements are limited to a Downs analysis or Steiner analysis, which measure proportions by the use of angles, there is no need to be concerned about enlargement. However, if one superimposes serial tracings, as everyone does, or measures tracings linearly, the problem of enlargement becomes a major factor. Correctional scales as employed by Broadbent and Adams can be used to correct for individual measurements, but it is not possible to superimpose tracings unless the x-rays are optically changed to uniform enlargement.
In the July issue, Dr. Burstone said:
I would agree that the reason you do cephalometrics is to get a better understanding of the orthodontic case you are going to treat, and not to develop a treatment plan. I look at the head film very much as a general looks at his maps before he plans a battle. He wants to know the terrain he is dealing with. I think that the reason we do cephalometrics is to find out the variation inherent in the individual, by comparison to a standard. The treatment planning is separate. It is a misuse of cephalometrics to use any of those numbers as a goal for treatment planning. For some years, it was common for orthodontists to treat by the numbers. I hope that most orthodontists have gotten away from that idea and that they use cephalometrics for its legitimate function, to let you know the morphology you are dealing with and to describe how the patient differs from the standards.
If these 3 statements are correct, and I believe that they are, they seriously call to question the techniques that most of us have used in posturing the patient for cephalometric x-ray, in positioning the film for standardized enlargement, in superimposing successive films, and in using the information we think we obtained from this assorted set of errors. One would have to have great faith in the canceling of errors to believe that research quality data would very often result from such science .
If an orthodontist believes in the importance of a centric relation occlusion, and its coincidence with maximum cuspation, that relationship must be a part of the clinical examination, study models should be trimmed to that relationship, and cephalometric x-rays should be taken with the patient's jaws in that relationship. Otherwise, it defies logic to deprive yourself of the view you say is fundamental to the realignment of the occlusal system.
If an orthodontist derives quantitative data from superimposed tracings, he now learns that if his data were not flawed by unstable or unreliable reference points, they were a mismatch because of size differences in the successive images.
I hope that everyone has studied Dr. Burstone's point of view. Elsewhere in his interview (in the August installment) he suggests that treatment decisions are 20% science and 80% judgment. Much of our fascination with cephalometrics has involved a continuing attempt to make judgment unnecessary. Without Dr. Burstone's having to tell us, we ought to have learned from experience that clinical orthodontics is an art both in techniques of bioengineering and human relationships.
