and Overcorrection

The question is: If the patient were wearing straight-wire applianc- es, why would we need to over-engineer the arch wire? We all learn as orthodontists that this arch-wire shape produces a force system, which will help to level the lower arch and flatten the Curve of Spee. We place extra into our arch wire knowing that it will produce force systems to give us a flat arch.

The same ideas apply with Invisalign treatment. How would we ask for a reverse Curve of Spee arch wire with Invisalign? Simply write in your prescription: “Please set the final over bite at 0mm.”

Those instructions will over-engineer the ClinCheck plan so that the final stage for a patient like the one depicted in image 10-2, the final over bite is set at 0mm. As we have discussed many times throughout this book when we’re looking at a ClinCheck plan we’re not looking at a pre- diction of the final occlusion. We are looking at a graphic representation of the force systems made by the aligners to the teeth. Force systems, not teeth. Just like the Reverse Curve of Spee arch wire, we add Reverse Curve of Spee to our lower arch in the ClinCheck treatment plan. As you can see in this patient (see Image 10-4), he didn’t end up with a Reverse Curve of Spee, but rather he ended up with a flat arch and appropriate bite opening. This ClinCheck plan was over-engineered to produce a normal final result.

Here again is Haley from chapter 5 (see Image 10-5). Similar to the previous patient, Haley presents with a deep over bite. Look at the final ClinCheck stage (see Image 10-6) where an additional 2mm of intru- sion was added to the upper and lower incisors so her final over bite is 0mm. The ClinCheck plan is over-engineered but in reality she doesn’t not wind up with the over engineered results (see Image 10-7). She has upper and lower arches that are flat and coordinated and an excellent functional and esthetic final result.

To the reader: This concept of deep bite over treatment is one that I have built right into my clinical preferences: “For all deep-bite cases, please finish with the final overbite at 0mm.” My technician builds in over treatment — my prescription — for all my deep-bite cases.

OPEN BITES

The over-engineering principle also applies to open bites. Let’s revisit Michelle’s case, from chapter 5 (see image 10-8). If you recall from this chap- ter dealing with problems in the vertical dimension, Michelle presented with an anterior open bite. Her treatment plan is to over-engineer her ClinCheck plan with 2mm of additional intrusion on the upper molars to create a 2mm posterior open bite. Why do we​ do​ it this way? The ClinCheck plan is not a prediction of the final occlusion, but rather a prediction of the force systems acting on the teeth. Force systems, not teeth. I want to place an additional intru- sion force on the upper molars. Intrusion is a difficult movement. I am not expecting the full expression of the aligners. I am not expecting the patient to develop a posterior open bite, but I want to place additional forces on the upper molars to ensure we gain additional intrusion to allow for auto-rota- tion of the mandible and closure of the bite. Here in this image (see image 10-9) is the area of over treatment on the upper molars.

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May 6, 2017 | Posted by in Orthodontics | Comments Off on and Overcorrection
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