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June's Tip: Common Areas For Case Disruption

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By: Dr. William Buckley

After practicing for 39 years and providing orthodontics for thirty years, the best Information I can pass on is: when the intra-case results are not what you expected go back to basics.  For any mechanical technique there are common basics which we all share: Diagnosis, Tooth Movement Progression, Functional Occlusion, and Retention.

Diagnosis a category in which we ALL have our own opinion; I assure the reader I am not supporting anyone in particular, however we can agree that knowing whether the patient is growing or not, and if growing, in what manner is BASIC. The next category of basic diagnostic knowledge which we all share is the relative sizes of the maxilla and mandible, and their respective relationship to the cranial base, and the spatial relationship to each other.

There is another aspect to diagnosis and treatment planning that is Basic: that is the maxillary tooth size to the mandibular tooth size. We know the analysis as the "Bolton analysis." Over the many years of reviewing cases this one analysis is the one most overlooked. Often a Bolton discrepancy is found in maxillary Laterals, but can be also caused by size discrepancies between mesial-distal width of the eight bicuspids. The Molars seem not to cause Bolton discrepancies very often.

Dr. Stephen Chu, at Columbia University, has worked out an anterior analysis from the Bolton that is very useful in determining whether or not the anterior teeth will occlude well at the end of treatment. This analysis uses the lower central incisor, when well -formed as x. From that mesial distal measurement of lower 1 one can use following formula to map out the anterior relationship x+1/2 =lower 2, x+1=lower 3. X+3=upper 1, x+1=upper 2, and x+3= upper 3. If you follow these two very basic analysis you will often catch a possible error in the making with regards to treatment planning.

After considering these very basic concepts; in my opinion, is where we all depart to our "comfortable camps" of "diagnostic direction.

It has been my observation that all too often, all camps, mitigate the effects of growth and overestimate the ability of the alveolus to accommodate expansion without relapse.

So if your treatment plan has lost its timing or is not developing as well as you had predicted, go back to your original DX/TP and check your treatment assumptions with regards to growth and development. Likewise check the amount of expansion you were anticipating.

Secondarily, if the retention period is not progressing as well, and you find that anytime spent, by the patient, without retainers is causing tooth movement; I would check where I placed the teeth with respect to the basilar bone, and functional occlusion.

The next category that seems to bedevil many people is case finishing. My experience has shown me that there are two facets of the comprehensive treatment appliance that cause the most errors during finishing. The first is consistent bracket placement with respect to the occlusal plane and the mesio-distal placement of the midline of the bracket. This may, when the placement is inconsistent, the result typically is a disrupted occlusal plane. This in turn can cause a deviation of mandible upon closure, and therefore a false sense that the arches are not aligned. At the same time a mandibular deviation can cause and anterior shift of the mandible such that the doctor feels he has achieved the proper anterior relationship only to find out latter that the anterior is not in proper relationship. Many times Doctors seem to be surprised when the anterior occlusal plane does not align and are surprised to find that the molar tubes for 308c19 or 38c14 are not in same plane of occlusion and or they are not parallel. The easy test at this point is cut two pieces of .030 wire about 7 inches long, remove the upper and lower arch wires and place the .o3o wire in either upper tubes or lower tubes and stand back and observe the planes of the .030 wires. Most times this procedure will clearly show whether your tube placement is affecting your plane of occlusion or not.

The second most vexing problem, and the one most often missed by auxiliaries is arch wire coordination. Often times when there exists a problem with the cusps of one arch lining up with the fosses of the opposing arch it is a problem generated by two different arch forms. The solution is to remove the arch wires and make sure that the maxillary wire is buccal to the mandibular arch wire. As simple as this seems it has become, with the advent of pre-made arch wires, one that is often found, especially if one buys arch wires from different suppliers. A simple but very effective solution is to use arch wire guides covered in plastic (for easy disinfection), or a tracing in every patient's file of the original arch form to be referred to at every arch wire change.

Functional occlusion is also an area which creates both intra and post-treatment problems. The best way to not allow functional occlusion to vex your sole is to use a leaf gage and monitor centric occlusion versus centric relation at 2-3 month intervals throughout treatment.

Briefly; functional occlusion requires that all teeth occlude in centric relation and that the anterior teeth (6-11) provide disclusion of all posterior teeth, including when cuspids bypass lower cuspids. Usually this statement brings forth a statement" I know group function works". There exists ample evidence that group function works, it is just very difficult to have a Dentist create it and keep it well monitored throughout one's dental life. Retention is the next and last area for this article. Retention is another one of the categories that brings out personal preference. I do not particular care which method, however I believe the retention systems that allow the actual teeth to articulate during the retention phase are the best. Those that allow tooth contact give the Dentist and patient a trial period of function with the back up of support while the PDL matrices is maturing from the cessation of orthodontic movement.

At the start and at intervals during retention I check Centric relation Occlusion with the leaf gage, and right and left working and balancing side contacts. I also "keystone" the lower anterior contacts prior to de-banding, this allows the lower anterior teeth to settle into a unit that can endure the occlusion because the contact point of each tooth stays in contact with its neighbor without slipping past the contact generated by next tooth in the arch.

To summarize; when In the course of your intended treatment do not doubt your abilities, rather go back to the beginning and carefully go over the basics. More times than not you will find the derivation which has caused you vexation.

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