Pre-surgical Dental Decompensation

[kjohnt]

Extractions?

My teenage orthodontics compensated for my overbite in part by proclining my lower incisors (and possibly retroclining my uppers but I can't tell if it's that or CW rotated jaws or both).  I know they will need to be straightened upright to make part of my overbite return prior to orthognathic surgery. 

I've read that some folks have to have premolars and/or other teeth extracted as part of the decompensation process, and I'd like to understand why.  Is it because their proclined incisors cannot be straightened upright without first creating extra space to do so?

I also read in this paper (http://www.med-college.hu/en/wiki/artikel.php?id=227&lan=2) that to make a class II worse as part of decompensation, class III rubber bands may be used and vice versa for class III decompensation. 

So in regard to decompensation, when are extractions needed and when are they not necessary?

Midlines

My upper midline is currently 1mm off to the right of my philtrum, and my lower is perfectly centered.  However, the rest of my teeth are in line and I have a good bite.  Would surgeons generally deem it necessary to center the upper midline?  I'm fine with it as is and it seems like it would cause more issues to mess with it as then my entire upper teeth (molars and such) would be off the lowers by 1mm...

Perhaps these are questions best suited for a consultation with a surgeon, but if anybody has previous related experience, please share!

[JayJaw]

I recently went to surgeon and was told the same as you. Honestly, after looking at my xrays / ceph and what not, I understand.

If your teeth were tilted to fit... It is one of 2 reasons. 1. Simply to mask the overbite. 2. Solve crowding.

For those that it was used to mask an overbite, it is possible they could be uprighted without extractions (because mandible still technically "large" enough). However, tilting teeth also is used to fix crowding. It makes the teeth fit in a larger arch (the wide ends anyway, not root ends). For me, my tongue thrust shaped my teeth in said larger arch rather than applying force to palate and actual jaws.

Anyway, they can't move teeth back into nonexistant jaw bone. They also can't give you an underbite during jaw surgery in hopes to move the lower after. They need to decompensate, and this could mean removing teeth if your jaws/teeth require it. Then they move jaws into place with teeth in proper decompensated positions.

If you don't have room for your teeth to be at the proper inclinationn due to crowding, then teeth need to be removed first. You could leave the compensation. However, you won't get as much movement laterally with mandible then. You can only get rotation and movement of jaws together.

[kjohnt]

Cool thanks.  I'd just assumed my lower incisors were tilted to mask my overbite, but I'm not sure if crowding was part of the issue.  It's been so long that I can't remember my lower teeth prior to orthodontics.  Looking at them now, I really don't see how they can be tilted backward any further because the upper ends are already touching and all of my lower teeth are close together, so I'd probably need extractions as part of decompensation.  I'll just have to see what the doctors say I guess.

...You could leave the compensation. However, you won't get as much movement laterally with mandible then. You can only get rotation and movement of jaws together.

I wonder if the difference is only a couple of mm that perhaps leaving the compensation is the best answer.  The lower jaw would remain retracted by that much, but I'd get to keep all of my teeth.  It sure would be nice if there was an easy way to expand the arches.

[molestrip]

Here's the reason. To make space for crowded teeth orthodontists have to expand the arch. That moves the teeth out of the center of the bone. To decompensate them they need to move them back to the center. At that location the arch is smaller again and there's no space for all the teeth anymore.

Orthodontics is a s**tty solution to a hard problem. Other than minor trivial things, the only solutions that make sense are extractions and surgery and even in those cases, not all problems can be solved well. A 3-piece, for example, doesn't perfectly level the arch in cases of two plane occlusions.

The best answer is really to never have problems in the first place, one area I seem to have lucked out in. My upper arch is 5mm too narrow but otherwise, plenty of room for all my teeth including wisdom teeth. Just goes to show that facial and alveolar bones are quite different, they develop at different times in life so while it's possible to have a common mode influence that interferes with both, sometimes only one or the other can be affected.

[kjohnt]

So I now understand how extractions and then tightening of the lower teeth will upright everything. 

I'm still curious about how the uppers can be pushed outward.  Does anybody know how this works?  It seems like it would create gaps.

[Tezcatli]

Not a direct answer but I also discovered my class I bite was due to natural compensation, my upper teeth were naturally proclined, twice the normal range, now I'm retracting then which is giving me an underbite that will be solved by jaw surgery.

My doctors said that if you don't have space to remove the compensation you will need to extract the bicuspids or get a palatal expansion. As few people get mandibular expansions* they prefer to remove the lower bicuspids. I'm lucky enough to have space for all 28 teeth and wisdom teeth as my main problem when I used braces as a child was gaps between the teeth, I had this huge diastema in the two upper incisors.

My midline is also off by 1-2mm, but the dentist said it's somewhat normal, it should be fixed during treatment but most people don't have exactly centered midlines and 1mm is not really perceptible during day to day life.

*Reasons being it's extra surgery and except if you have an extremely narrow mandible it's likely you would need to expand the upper arch too, so that would be two surgeries, more recovery time, more risk of nerve damage etc.