THE EDITOR'S CORNER

There are ideas that achieve the status of "a well-known fact" through repetition. Some of these have become a routine part of the treatment procedure of many orthodontists without having been proven. One of these is overcorrection or overmovement of teeth.

Overcorrection is advocated in the treatment of rotation and one also sees it recommended for anterior-posterior correction, for tipping, for torquing, for expansion, and for overbite.

One has to respect the clinical experience of practicing orthodontists, and yet one can also ask for proof. Indiscriminate overtreatment with no proof of its value could not be defended as good procedure.

Take rotations. The reasoning is that it is necessary to overstretch connecting fibers so that when they contract on being let go, they will relapse to a correct position. There has been some research to indicate that the basic mechanism of fiber stretching is valid. However, there has not been anything to establish the validity of overrotation; no evidence to compare ultimate (5-year) relapse in teeth that are rotated to a correct position with those that are overrotated to varying degrees; no evidence to show how much overcorrection is sufficient; no evidence to point out how the teeth decide to stop relapsing in a corrected position; no evidence of how problems of rotation may vary from tooth to tooth, from mouth to mouth; that tooth anatomy may play a role; that occlusion and function may play a role; that collateral correction in terms of bodily movement, tipping, etc. may introduce a more complicated mechanism than what we visualize as rotation.

This whole discussion suggests that we should be taking a well-designed look at overrotation both from the point of view of trying to assess its validity and also from the standpoint of finding a more satisfactory method of dealing with the problem of relapsing rotation. There is some evidence in the literature that a periodontal-surgical solution could be a better answer.

There are orthodontists who aim to correct Class II malocclusions to an overcorrected Class I with an anterior edge-to-edge relationship. The reasoning is that these will relapse into a perfect Class I. Many of these fool you and do not relapse into a perfect Class I, but remain in an overcorrected Class-III-ish relationship and frequently with an anterior open bite. You do not have to experience too many of these to realize that you can correct your Class II to a solidly interdigitated Class I with optimum opening of the anterior bite and simply stop whatever mechanics you are employing to test the stability of the anterior-posterior correction. In this connection, Tweed mechanics called for overtreatment as a stage of treatment. However, it was followed by careful finishing mechanics to a well-interdigitated "socked in" Class I cusp relationship (See Kaplan, JPO, June 1968).

It seems to me that a quick relapse of a corrected Class I relationship must be due to extraneous mesial movement of the mandible in treatment which, when released, retropositions to an unrestrained more distal position. This should be demonstrable cephalometrically. If there is a change over a longer period of time, it could be an adverse differential growth pattern; or a slower release of the artificially mesially positioned mandible, perhaps due to a more gradual elimination of some interferences that maintained the artificial position for a while; or possibly a slower unlearning process of a learned artificial mesial position of the mandible. True correction of a posterior occlusion, as opposed to the false contribution of some mesial mandibular jaw movement, will most often retain itself.

Overtipping in a mesio-distal direction and overtorquing in a labio-lingual or bucco-lingual direction probably produce unstable positions and invite relapse which causes the teeth to assume improved positions and seems to lend itself, albeit probably falsely, to the interpretation that the overtreatment assisted in producing correct final positions. In this connection, anyone who has ever torqued an incisor root in the lower arch labially or lingually out of the cortical plate or in the upper arch labially out of the plate or lingually against the palatal bone with resorption of the root tips visible in a sagittal plane on cephalometric x-ray, may take a dim view of overtorque if he can see satisfactory results by torque to a satisfactory completed position.

Correction of a narrow arch by overexpansion has drawn the ire of many modern orthodontists and yet some palatal expansion people practice overexpansion in anticipation of relapse. Certainly for starters, we should distinguish between various arches and the inclinations of buccal teeth before uniformly overexpanding narrow arches (See Di Paolo, JCO, September 1970).

Overcorrection of deep overbite by excessive bite opening has merit in treatment mechanics, but as far as treatment results are concerned, there is not a standard amount of relapse to be expected which, therefore would permit us to see better results if that amount of relapse is applied to a treatment-produced open bite as compared to an edge-to-edge bite or a partly closed or overlapping bite. The question is far different from so oversimplified a concept. It is also related to such things as vertical growth, tooth and jaw relationships, extrusion, intrusion, continuous eruption, and methods of retention.

There are techniques which require certain movements of overtreatment in order to accomplish treatment. However, overtreatment for any reason with the expectation of relapse to a more desirable position is a round trip and cannot be considered optimum treatment. If overcorrection does contribute anything to the correctness or stability of an orthodontic result, it can only be considered an expedient which is useful because we don't know how to achieve a correct, stable end position without it. It is well, however, not to confuse those requirements with some more general concept that overtreatment is necessary in order to achieve a correct, stable result. Not, at least, before we have a lot more evidence than we have that this is true.