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Case Finishing: Is it all about the Bracket Prescription

By: Dr. William Buckley

By: Dr. William Buckley

 

It has been the convention in orthodontics, since the innovation of the prescription Rx bracket, that case finishing was a "Fake-complate." However, just as relapse was the "demon" that always visited the completed case, the Rx bracket has brought no more stabilization than its predecessors.

Every dentist who has contemplated "the end" has mentally wrestled with how to ensure that the completed orthodontic result will be stable. In the profession we have been driven to "eternal" retainers, treating with functional appliances in phase one, only non-extraction therapy, head gear, orthognathic surgery. All the modalities were to ensure the outcome of stability. Many leaders in the field of orthodontics have created cephalometric analyses such as Dr. Tweed with the "Tweed- triangle" with his ultimate treatment position of lower 1 to mandibular plane (incisor to mandibular plane angle) of 90°. Dr. Williams had the measurement of lower 1 to A-P of -1 to +1 to be the ideal final resting place of the lower incisor.

The common factor throughout orthodontics that has been perennially ignored is functional occlusion. This paper will be the initial one of a series that will present the relationship of centric relation, centric occlusion, and functional occlusion with orthodontic case finishing and stability of the orthodontic result.

Dr. Pete Dawson has said it as succinctly as possible, "occlusal disease is the number one factor in orthodontic relapse." Dr. Dawson goes on to define disease as: the inability of the structure or organism to adapt to the stresses it is subjected to, and therefore the structure or function or both are changed forever." This, I dare say, is what we have commonly called relapse, the bane of every dentist who has ever treated orthodontic patients. Can we learn from the non-orthodontist Dr. Dawson?

Dr. Dawson continues to instruct that anyone who is considering full mouth reconstruction should always, without exception, make sure that the TMJ health is secure prior to treatment.  The TMJ represents the major part of the neuromuscular component of the gnathostomatic system, and as such controls the "envelope of motion." When the functional occlusion is not coordinated with this envelope, it creates either problems with the TMJ apparatus or the stability of the teeth or both.

The Foundation for Orthodontic Research was a group created by leading members of the American Association of Orthodontists to research these very nettlesome issues that we all face. The group's conclusion was expressed in a position paper delivered by Dr. Wm Mc Horns at the AA0 convention in 1980. The main conclusion of the paper is: "When full mouth orthodontics is done with respect to centric relation and functional occlusion it is the finest full mouth reconstruction done in the world."

So dust off your crown and bridge books from dental school and borrow and articulator from a friend if do not have one, because we have to incorporate all the ideals from crown and bridge that apply when 'providing reconstructive dentistry.

As further proof of the need for this discomfort you are now having with this article, ask yourself what RX is in the bracket that I presently use? I would bet your next year's IA0 dues that it is a Roth Rx. Question: do you know what Dr. Roth's protocol for every case was prior to finishing? He mounted the orthodontic case, with a facebow and centric bite to evaluate the functional occlusion prior to removing braces.

Recent articles such as this one have been published, "Changes in functional occlusion during the post-orthodontic retention period: a prospective longitudinal clinical study." Am J Dentopcial Orthjpedics Mar; 135(3): 310-5. To quote the conclusion, "Settling of the occluding teeth seems not to improve the functional occlusion after fixed appliance removal. Thus, it is ne'cessary to check the functional occlusion before the appliance is removed to eliminate unsatisfying functional occlusal contacts."

A second article: "Orthodontics and Occlusion," British Dental Journal Volume 191, No. 10 November 24, 2001. It is important to point out that is necessary to carry out a full occlusal examination for all orthodontic patients. Not only the patient's habitual bite (centric occlusion, CO) but also to record the patient's ideal jaw relationship (centric relation, CR). Then ask yourself the question does CR occiir at the same place as CO and if not why not? Secondly, does the anterior guidance occur without posterior interference? Without this examination the dentist or orthodontist cannot fully assess a malocclusion or avoid mistakes in treatment planning. Another aspect of case finishing that needs to be considered at the beginning is tooth size discrepancy and arch form which we commonly call arch length discrepancy. Both of these measurements can forecast impending problems that, at the end of treatment, will either secure the result or cause relapse to be more likely.

In the ensuing articles we will cover: envelope of function vs. envelope of motion, centric relation and why it is important to relapse, is cuspid guidance the same as anterior guidance, cross-over and how does it impact on lower one to A-P, how to record centric relation reliably, and take cephalometric radiographs in centric relation, and when is the best time to perform an occlusal adjustment on an orthodontic patient?

Dr. Bill Buckley is an IBO Diplomate, a Fellow of the Academy of General Dentistry and lectures internationally.