By: Dr. William Buckley
In the last two Ortho points that I wrote, I have covered the intellectual portion of why Functional Occlusion is of paramount importance to Orthodontics. I also covered the background research that our "Orthodontic Forbearers" did to try and determine is there such a thing as orthodontic stability, and can they reduce it to a formula applicable to cephalometric measurements
My intention, in this article, is to make the use of Centric Related Occlusion common practice in your office.
The two tools, which are indispensable in using Centric Related Occlusion, are 1) The Facebow, 2) Leaf-Gage. The Facebow I prefer: is the Denar-Earbow (Figure 1-2-3)the technique I sue for capturing centric relation is: the Leaf Gage (Figure 4).
For twenty years I used the “Dawson” bimanual-manipulation technique, after being challenged by Dr. McHorris to compare techniques, I have found that the leaf-gage to be as predictably accurate, and a lot faster. This is especially true when you are first encountering a new patient but want the “Centric Record”. The second incident which makes the leaf-gage indispensible: The patient with trismis can, while in the operatory, be induced to relax the muscles of mastication by incrementally “walking” the jaw open and into centric relation with the use of the leaf-gage. Then by reducing the number of leafs one can find the offending contract creating the trismis. A short note to emphasize the practical and real importance of the Facebow: Dr. Roth, whom it is safe to say has the most copied “bracket RX” in the world, did not depend on his Rx as much as his Facebow and Centric related mounting during treatment to create consistent and long lasting excellent results. Dr. Roth at approximately 18 months into treatment mounted his cases and assessed the occlusal scheme with regards to functional occlusion and centric relation; after his study he often practiced an occlusal adjustment on the mounted models and then transferred that practical “knowledge” to his patients and finished treatment.
The Denar Facebow is extremely easy to teach assistants, and the results are not only repeatable but accurate every time. The mounting “jig” which comes with the Facebow (Figure 5-6), makes the turnaround time, for reusing the Facebow, about 1 minute. With multiple jigs one can use the Facebow for different patients, to the extent of the number of jigs that are not presently associated with a specific case. If the assistants are trained to take the mounting jig and immediately place on the Denar articulator with the upper cast, and place mounting plaster, the whole “Axis-of-rotation” can be transferred within ten minutes, thus freeing up the mounting jig for the next patient (Figure 7).
The next task, in accurately capturing the centric relation for a specific patient , is completed in many ways, I prefer the “Leaf Gage.” This process need not be time consuming, or frustrating to a busy General Practice. First several wax forms of different sizes can be pre-made and placed into warm water ready for use, after the face bow the assistant can approximate the usable premade-form for the particular patient from the Facebow recording, and then in a rubber bowl with warm water place that in operatory with the patient awaiting the Doctor. The doctor uses the leaf gage to determine centric relation, after finding “centric” introduces the wax rim records centric, and the whole process is done in less than 3 minutes (Figure 8)
With the wax bite and the Facebow transfer the assistants can mount the models, and present the mounted set to the Doctor for evaluation. Notes, with sharpie marker, can be made on casts and a future date taken back to patient for verification. A sophistication of the mounted model, which would help identify anywhere that the Doctor has modified the casts, would be to spray paint the models with a contrasting acrylic color, thus any alteration of the original casts would be readily apparent to the observer. These marks can be clinical guides with the patient at hand (Figures 9-10).
Hopefully this article has made what seems to be an onerous and time consuming task in the busy practice one which can be incorporated with ease.
My journey from student at Case Western Reserve Dental School to now, through the various post-grad CE’s has been immeasurably enhanced by the adaption of Centric Relation. The predictability and accuracy by incorporating these techniques have made the Orthodontic Outcomes more stable (without permanent retention). Centric Relation has also made the restorative portion of General Practice more predictable and the resultant restorations more serviceable.
From Dr. Pankey, to Dr. Dowson, to Dr. Wirth, Dr. Gysi, Dr. Roth, to Dr. Conlin, to Dr. Kesling, to Dr. McHorris, to Dr Hoffman; I owe to them to “Pay it forward”.