Wow so much good info. I need to do some more reading before I understand *everything* in this discussion
But overall Kavan's argument makes intuitive sense to me -- a posterior impaction will allow the *lower jaw* to rotate more CCW, even if the upper jaw is technically moved CW. So overall the lower face should be shorted. But I also understand PB's caveat that if the maxilla is advanced *a lot* at a downward angle, that could increase length (at least could increase the distance from my forehead to my upper teeth), but hopefully that can be accounted for when calculating the amount of anterior impaction. E.g. more maxilla advancement at a downward angle, more anterior impaction to offset vertical addition from the advancement. It seems like it should be possible to fully account for this.
Tbh, in general, I don't understand what the problem is with a "steep occlusal angle" (I believe occlusal angle = angle of your bite), other than the fact that it is correlated with having a long face. Don't teeth normally go up in the back in a healthy bite? (See attachment). Sorry if this question is off topic, I can post elsewhere if so!
One thing I'm worried about, speaking of feminine aesthetics, is that both age and orthognathic surgery can lengthen the philtrum, and result in less upper incisor show while speaking. I hope that fixing my bite will get rid of the gummy smile, but I don't want to impact SO much anteriorly that my upper lip covers my teeth. Anyway, I guess this will come down to the exact plan, which I wish I could have BEFORE committing to decompensating orthodontics! But as you can tell I am leaning toward the surgery regardless, since it sounds like *some* solution should be possible
I agree with some of the posts that I would tend to be on the conservative side -- I do want the best aesthetic result possible, but only within a reasonable range of what I would naturally have had, if my jaw had developed normally without chronic allergies (my parents were anti-medicine and I guess thought my constant stuffy nose was normal :/). E.g. I especially don't want a large chin even if that is technically more "correct". But hopefully I can communicate all this when decision time arrives
Thing is that with Anterior Open Bite (AOB), you have 2 occlusal planes (OPs), the max OP and the mandibular OP, NOT one. This forms and OPEN WEDGE in front where the bite doesn't close in front. It doesn't close in front because the BACK part of the maxilla is too long where only the back teeth meet each other. So BASICALLY what they do to close that open wedge space is to CUT somewhat of a similar wedge from the maxilla; one kind of pointing in the opposite direction. That moves the back of the maxilla UP more than the front of the maxilla. The removal of the wedge of bone along with the net CW rotation is the IMPACTION. The CW rotation of the cut out wedge section is CW rotation on the UPSWING. Just like the hands of a clock travel on the upswing when they travel between 6 and 12 o'clock.
This UPSWING CW rotation is what COUNTER ACTS the DOWNSWING CW (hands of a clock traveling between 12 and 6 oclock) you see to the open wedge in front where the mandible is being forced into more of a CW r because the excess length at the back of the maxilla PRECLUDES it from swinging up.
When the mandible can swing up to close the bite, you will have ONE OP and your MPA will be less steep. From there, they can elect to do linear advancement and the sliding genio. IF NOT linear advancement (eg less advancement to maxilla/more to mandible), the option to move the lower jaw further than the upper jaw (or upper jaw less than lower jaw) would depend on how they prepare the teeth for the surgery. For example if they 'buck out' the front teeth and can manage to also push backwards the lower teeth, then they can move the upper jaw forward less and the lower jaw forward more.
As to your other concerns/questions:
The philtrum does NOT get longer. It just can LOOK longer when it's aligned with a vertical plane or becomes conVEX. Some maxillary advancements can even make the philtrum look shorter like when they buck out the teeth somewhat and advance, then the philtrum is on outward diagonal plane and looks shorter. Also, TOOTH SHOW from the FRONT is part of the plan as to get the optimal amount of tooth show without excess gum show.
Keep in mind:
Presently, with 2 OPs, the surgery goal is a matter of forming ONE OP. So, your OP really can't be measured at this point. The goal of this type of surgery (type for you) is really to 'level out' the MAXILLARY PLANE. The goal is not really to make the OP less steep. Even when the goal is to make the OP less steep, it's the maxillary plane that's really altered. But it's not as if someone is going to suggest a CCW posterior downgraft so you can have MORE posterior gum show than you have now! So, for now, I would not fret about the OP because that's more relative to people who have ONLY ONE OP, not 2 diverging OPs. The 'steepness' that is way beyond the norm is the MPA. It will get less steep but be still outside the norm (because the rotation the impaction does, even though it makes it less steep won't counter-act the excess steepness it has from the norm). In fact it would be the steepness of the MPA and NOT the OP that would tend to LIMIT how much advancement you can have whether it's linear (equal max and mand.) or less maxilla and more mandible. So, I don't think you have to worry about philtral problems, bull's nostrils or 'masculine' jaw. BECAUSE, they are going to want to LIMIT the mandible advancement so they can LIMIT advancing over a steep MPA. Limit would apply to the max. advancement too.
