THE EDITOR'S CORNER

"It may be put down as quite a general rule," Edward Angle said, "that the degree of perfection of the models he makes is indicative of the knowledge, skill and success of the orthodontist in the treatment of his patients". He advocated before and after treatment models taken with plaster impressions and produced with a beauty and exactness of detail with regard to both the anatomical and the art portions.

Calvin Case was less of a stickler for absolute detail and would accept compound impressions on difficult children. He did not object to plaster impressions "if for no other reason than it tends to cultivate habits of nicety and exactitude in other more important branches which pertain to the art of regulating teeth". However, he believed that the mouth was the best place to make the diagnosis.

So, it came to pass early in the practice of orthodontics that a cabinet of good-looking models became the hallmark of a good and successful orthodontist. The art bases of these models were generally trimmed parallel to the occlusal plane and bilaterally symmetrical. In various combinations, upper or lower occlusal plane were used to establish the horizontal plane of the model bases, and upper or lower central contact were used to establish the bilateral symmetry. These methods continue to this day, in spite of the fact that it has been apparent for a long time that occlusal planes are not always horizontal and that dental midlines are not always centered. As long as everyone understood that these were art bases whose sole purpose was to make a nice appearance, little harm resulted. However, as models became more and more important in diagnosis, one could easily be deluded as to the nature of the problem. Indeed, with a little carelessness in trimming, many a case was improved on the model trimmer alone.

The gnathostatic method of trimming casts was, in part, an effort to respond to this problem by relating the models to the orientation of the dentition in the head with reference to the Frankfort plane, the mid-sagittal plane and the preauricular plane. The method fell into disuse partly because Simon was discredited, partly because the method was more sophisticated than orthodontic treatment at that time, and partly because it was too difficult and time-consuming. Making models from plaster impressions and the gnathostatic technique probably did more to discourage careers in orthodontics than any other single factor.

I agree that orthodontists who have better quality, better looking and more complete records impress me as being better orthodontists, performing superior treatment. However, I also think that the quality of the records stems from the quality of the orthodontist and not vice versa. And, it may be that quality orthodontists will continue to produce high quality study models with bases trimmed to a standard formula, if only because it serves an esthetic purpose. But, when we talk about study models in the future, most of the time these will not be what we are talking about.

For the most part, and especially for cases in the permanent dentition, study models are going to be dynamic and not static. We are going to be mounting casts on sophisticated simulating articulators. We are going to be orienting the casts in centric relation. Diagnoses will be made from the centric relation position rather than the centric occlusion position and treatment will be aimed at making the two coincide. Orthodontists are going to be the keepers of the keys of occlusion. The reason that study models will become dynamic instead of static is that the orthodontists' concept of occlusion in diagnosis, treatment and especially in finishing is going to be dynamic instead of static.

Exciting as orthodontic practice has been, it is about to become more interesting and exciting as we go from concepts that are relatively static to those that are dynamic. Our fund of knowledge has reached that level. Each of us must ask himself how well prepared he is to practice dynamic orthodontics.