Posterior maxillary impaction

[ODog]

Hi guys,


Can someone explain to me how posterior maxilla impaction would affect the face, e.g soft tissues? Does it lend support to the cheekbones.l?

Also, does it shorten or lengthen the face? I know with anterior impaction the mandible is auto-rotated up and forward CCW, but wouldn’t posterior impaction lend  a CW rotation of upper jaw and lengthen the face?

I have a long face (Class 3) with a steep mandibular plane, however with no tooth show at rest (philthrum is also normal length).

[kavan]

If your excess bone length comes from the back of the upper jaw, posterior impaction is done where they remove a wedge from the BACK of it. So, it shortens where you have the excess of bone length. It does not lengthen the face.

[ODog]

Ok thanks Kavan. Does it rotate the mandible a bit CCW?

[kavan]

it rotates the BACK of the mandible UP CW.

[ODog]

I might not be understanding this correctly but wouldn’t that steepen my jaw angle ?

[kavan]

It's mainly to correct a bite but since it's removal of bone, the back of jaw will rotate upwards and be shorter.

[Dogmatix]

it rotates the BACK of the mandible UP CW.

I think this is a really interesting topic. Is there any way this relation can be understood? When I look at different animations of jaw surgeries, it doesn't make it clear that there's an automatic response to the other jaw when one of the jaws are having surgery.

I understand that I can't base my education on youtube clips, but these videos basically sums up what understanding I can have so far. Videos below displays posterior impaction, and the mandible seems to stay in the same position. How can I understand what happens to the mandible that is not shown in this video?
https://www.youtube.com/watch?v=IDURPY1TCBM
https://www.youtube.com/watch?v=VzUmMOCyBTA

[ODog]

My orthodontist told me Posterior Impaction shortens the face. In terms of what happens to the mandible he never elaborated. But if you visualize the posterior region getting shorter to align with the anterior region, the mandible would have to come up and forward to maintain occlusion, just like an anterior impaction....

[ODog]

Thanks for the video, it actually shows how the mandible is affected... it clearly moves up and forward to maintain occlusion

[Dogmatix]

Thanks for the video, it actually shows how the mandible is affected... it clearly moves up and forward to maintain occlusion

Maybe there's a terminology confusion here. In my sense, the mandible is not moved in these videos, how ever the the person who bite will have to bite a bit differently to reach occlusion after surgery.

[ODog]

Look at the attached pic. Mandible is clearly positioned differently after impaction. It is up and forward. Look at the chin projection. Face is also shorter.

[Dogmatix]

Look at the attached pic. Mandible is clearly positioned differently after impaction. It is up and forward. Look at the chin projection. Face is also shorter.

The maxilla is cut and actually moved. The mandible is positioned differently because the support level it has to reach for occlusion has moved away and the after picture is at the new support level.
It's like if you would put your finger on the molars of the maxilla before and after, and say that the surgery affects and move your fingers.

[ODog]

Right I’m not saying it moves the mandible directly obviously since only the maxilla is cut but all that matters is the new resting position of the mandible at occlusion.

[ODog]

Anterior impaction doesn’t affect the mandible directly either, yet the new resting position allows the plane angle to straighten out.

[ODog]

https://youtu.be/xR9NNPJ9280

As shown in this video, anterior impaction affects the mandible in the same way by allowing it to assume a resting position higher up