jawsurgeryforums.com
General Category => Aesthetics => Topic started by: ODog on June 04, 2018, 05:07:35 PM
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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).
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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.
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Ok thanks Kavan. Does it rotate the mandible a bit CCW?
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it rotates the BACK of the mandible UP CW.
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I might not be understanding this correctly but wouldn’t that steepen my jaw angle ?
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It's mainly to correct a bite but since it's removal of bone, the back of jaw will rotate upwards and be shorter.
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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
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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....
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Thanks for the video, it actually shows how the mandible is affected... it clearly moves up and forward to maintain occlusion
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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.
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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.
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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.
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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.
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Anterior impaction doesn’t affect the mandible directly either, yet the new resting position allows the plane angle to straighten out.
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https://youtu.be/xR9NNPJ9280 (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
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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
In terms of what I told the OP (or 'OD'), I told him they take a wedge from the back of the (upper) jaw and the jaw rotates CW up. The video SHOWS the wedge shape removal at 0:21 and the subsequent CW rotation of the upper jaw and of course, the lower jaw will rotate in same direction to meet it. Not clear on what you need to understand other than to tell you, the video shows what I was telling him at the time frame of the video I gave. So, we assume his excess face length is coming from the BACK of his upper jaw, (assumed because he says his face is long and he's getting posterior impaction). Hence, this will shorten where his EXCESS is.
A lot of this stuff, conceptually is just grammar school geometry concepts and I think I told you sometime before that the lower jaw will swing in the direction of rotation the upper jaw has been displaced in.
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What’s confusing are the posts on here that talk about CW rotation or posterior impaction lengthening the face. Clearly this is wrong... unless there is some other CW procedure I’m unaware of
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What’s confusing are the posts on here that talk about CW rotation or posterior impaction lengthening the face. Clearly this is wrong... unless there is some other CW procedure I’m unaware of
Confusion abates when you think in terms of geometry concepts and observing relationships which is basically what is needed to conceptualize some very basic maxfax relationships.
For example, ROTATIONS: clockwise or counterclockwise (which are in reference to the profile facing to the right). Clockwise is in the 'downward' direction when the big hand on the clock rotates from 12 oclock to 6 oclock. But from 6 oclock back to 12 oclock, clockwise rotation is in the 'upward' direction. So, if someone gets an ANTERIOR downgraft (a wedge added to front maxilla), that is CW with reference to going in direction from 12 oc to 6 oc which is downwards (some elongation). But if someone gets a posterior impaction (a wedge removed from posterior maxilla), it's also CW but with reference to going in direction from 6oc to 12 oc which is upwards (some shortening). Same concept for CCW but in reverse.
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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.
Actually, it's more like you observe there has been a change in angle orientation of the mandible OR just take out your protractor and measure the change in angle of inclination of the mandibular plane.
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Confusion abates when you think in terms of geometry concepts and observing relationships which is basically what is needed to conceptualize some very basic maxfax relationships.
For example, ROTATIONS: clockwise or counterclockwise (which are in reference to the profile facing to the right). Clockwise is in the 'downward' direction when the big hand on the clock rotates from 12 oclock to 6 oclock. But from 6 oclock back to 12 oclock, clockwise rotation is in the 'upward' direction. So, if someone gets an ANTERIOR downgraft (a wedge added to front maxilla), that is CW with reference to going in direction from 12 oc to 6 oc which is downwards (some elongation). But if someone gets a posterior impaction (a wedge removed from posterior maxilla), it's also CW but with reference to going in direction from 6oc to 12 oc which is upwards (some shortening). Same concept for CCW but in reverse.
Oh yes I forgot to say the front of my maxilla will also be brought down as I have 0 tooth show at rest (back maxilla is long, front is short); so I was wondering if THAT CW rotation would elongate the face or would the impaction balance it out ?
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Oh yes I forgot to say the front of my maxilla will also be brought down as I have 0 tooth show at rest (back maxilla is long, front is short); so I was wondering if THAT CW rotation would elongate the face or would the impaction balance it out ?
Depends on the net CW rotation. If more is removed from the back than 'dropped down' in the front, then mandible plane angle should be LESS than what you started with.
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Thank you Kavan.
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Depends on the net CW rotation. If more is removed from the back than 'dropped down' in the front, then mandible plane angle should be LESS than what you started with.
Kavan and ODog, this isn't true at all.
Assuming solely autorotation of the mandible (and that occlusion will be satisfactory after surgery), the change of the mandibular plane angle can be explained by the following:
(CW rotation of mandibular plane) = (CW rotation of the maxilla) - (degrees of anterior open bite)
All terms are in degrees, and the last terms measures the discrepancy between the maxillary and mandibular occlusal planes (where an anterior open bite is positive). Negative CW rotations are positive CCW rotations.
QUIZ:
Derive the above "formula," using simple geometric concepts.
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No idea what you are talking about.
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Kavan and ODog, this isn't true at all.
Assuming solely autorotation of the mandible (and that occlusion will be satisfactory after surgery), the change of the mandibular plane angle can be explained by the following:
(CW rotation of mandibular plane) = (CW rotation of the maxilla) - (degrees of anterior open bite)
All terms are in degrees, and the last terms measures the discrepancy between the maxillary and mandibular occlusal planes (where an anterior open bite is positive). Negative CW rotations are positive CCW rotations.
QUIZ:
Derive the above "formula," using simple geometric concepts.
The videos shown on this thread titled 'Anterior Open bite' were introduced by neither me nor the OP. But from the videos we were looking at POSTERIOR IMPACTION.
The OP did NOT say he had an anterior open bite.
The OP also did not mention the NET number of degrees his maxilla was to be rotated.
What numbers do you propose be plugged into your equation given neither any mention of an anterior open bite NOR any mention of the proposed CW rotation of the maxilla???
PLEASE ANSWER the OP'S question:
["Oh yes I forgot to say the front of my maxilla will also be brought down as I have 0 tooth show at rest (back maxilla is long, front is short); so I was wondering if THAT CW rotation would elongate the face or would the impaction balance it out ?"]
In terms of only his question and in the ABSENCE of ANY mention of his having an anterior open bite and also in the absence of any quantitative degree measures.
I would like to see the correct answer relative to how he asked the question in the absence of any quantitative measures and mention of having any anterior open bite.
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What numbers do you propose be plugged into your equation given neither any mention of an anterior open bite NOR any mention of the proposed CW rotation of the maxilla???
If OP doesn't have an anterior open bite, then the number to plug into the last term (I specified the last term as "the discrepancy between the maxillary and mandibular occlusal planes") would be zero.
Thus, in cases where the maxillary and mandibular occlusal planes are parallel, the formula simplifies to:
(CW rotation of mandibular plane) = (CW rotation of the maxilla)
OP mentioned that he is getting CW rotation, which implies the term on the right side of the equation is positive, which in turn implies that there will be "positive" CW rotation of the mandibular plane (assuming OP doesn't have an anterior open bite).
You said,
Depends on the net CW rotation. If more is removed from the back than 'dropped down' in the front, then mandible plane angle should be LESS than what you started with.
This is false. Consider a case when there is both a posterior impaction and an anterior disimpaction (downgrafting) where the magnitude of the posterior impaction is greater than the magnitude of the anterior disimpaction. Also assume OP doesn't have an anterior open bite. Since both the posterior impaction and anterior disimpaction contribute to CW, there must be a positive net CW rotation of the maxilla, which would yield a positive net CW rotation of the mandibular plane from the formula.
CW rotation of the mandibular plane is a steepening of the mandibular plane, or an increase in the mandibular plane angle. But you said that "If more is removed from the back than 'dropped down' in the front, then mandible plane angle should be LESS than what you started with." Thus, this case contradicts your statement.
@ODog, I was basically pointing out that if you don't have an anterior openbite, clockwise rotation of the maxilla will result in an INCREASE in mandibular plane angle, not a reduction like kavan said.
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If OP doesn't have an anterior open bite, then the number to plug into the last term (I specified the last term as "the discrepancy between the maxillary and mandibular occlusal planes") would be zero.
Thus, in cases where the maxillary and mandibular occlusal planes are parallel, the formula simplifies to:
(CW rotation of mandibular plane) = (CW rotation of the maxilla)
OP mentioned that he is getting CW rotation, which implies the term on the right side of the equation is positive, which in turn implies that there will be "positive" CW rotation of the mandibular plane (assuming OP doesn't have an anterior open bite).
You said,
This is false. Consider a case when there is both a posterior impaction and an anterior disimpaction (downgrafting) where the magnitude of the posterior impaction is greater than the magnitude of the anterior disimpaction. Also assume OP doesn't have an anterior open bite. Since both the posterior impaction and anterior disimpaction contribute to CW, there must be a positive net CW rotation of the maxilla, which would yield a positive net CW rotation of the mandibular plane from the formula.
CW rotation of the mandibular plane is a steepening of the mandibular plane, or an increase in the mandibular plane angle. But you said that "If more is removed from the back than 'dropped down' in the front, then mandible plane angle should be LESS than what you started with." Thus, this case contradicts your statement.
@ODog, I was basically pointing out that if you don't have an anterior openbite, clockwise rotation of the maxilla will result in an INCREASE in mandibular plane angle, not a reduction like kavan said.
OK. I see what you are saying and how I went wrong on this one. I was looking at video only in terms of posterior impaction and disregarded the Title of 'Anterior Open Bite'. I erroneously attributed the decrease in MPA to posterior impaction when a screen shot of the video was entered from which I measured a decrease in the angle. Hence the decrease in MPA from the screen shot pulled from the video was attributable to the significant open bite.
Thanks for catching that. I gave you a Karma point.
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OK. I see what you are saying and how I went wrong on this one. I was looking at video only in terms of posterior impaction and disregarded the Title of 'Anterior Open Bite'. I erroneously attributed the decrease in MPA to posterior impaction when a screen shot of the video was entered from which I measured a decrease in the angle. Hence the decrease in MPA from the screen shot pulled from the video was attributable to the significant open bite.
Thanks for catching that. I gave you a Karma point.
No problem, happy to help. Interesting that you used screenshots from the video simulation to try to see if the MPA steepened, since it would be way easier just to use basic geometric intuition (since you seem to often comment about that lol). If you were assuming OP didn't have an open bite pre-surgery, then obviously rotation of the maxilla would force an equal autorotation of the mandible, or else OP would be left with an open bite post-surgery.
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I didn't take the screen shots though. Just measured the angle. The OP did not say he had an open bite. Again, got caught up in in just the posterior wedge cut of the video and disregarded the actual title of it.
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I think my braces are decomensating my teeth and revealing a bit of an open bite actually. However I assumed having a long posterior maxilla and a short anterior maxilla basically = an anterior open bite. Or else why would you impact the posterior ?
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I think my braces are decomensating my teeth and revealing a bit of an open bite actually. However I assumed having a long posterior maxilla and a short anterior maxilla basically = an anterior open bite. Or else why would you impact the posterior ?
Are you planning on having BSSO along with the LF1?
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Probably mandible advanced as well. But the surgeons I meet with say single jaw is better if we can do it... not sure what the final plan will be
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Are you planning on having BSSO along with the LF1?
Sorry for bringing up an old thread. I just want clarification on how my surgery will change my face. First off, please bear with me as my doctors don’t really share exact information with me and have been quite vague thus far as to the exact causes of my jaw problems.
It turns out I DO have an anterior open bite, which has now been revealed. The cause is posterior vertical maxillary excess, along with (I assume) anterior vertical maxillary deficiency (no tooth show at rest).
I am getting bi-max advancement of maxilla and mandible along with vertical reduction and advancement genioplasty of the chin.
Now, in regards to the open bite, will this correct itself on its own as it advances sagitally, I.e the anterior maxilla naturally comes down with advancement thus allowing for more tooth show and proper bite ?
Or will my surgeon have to impact the posterior max. IF SO, now that you know I have an open bite, how will this affect my mandible rotation ?
From what I understand, this will depend on how much is removed posteriorly and how much is brough down anteriorly. So probably the net affect would be 0, correct ?
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Sorry for bringing up an old thread. I just want clarification on how my surgery will change my face. First off, please bear with me as my doctors don’t really share exact information with me and have been quite vague thus far as to the exact causes of my jaw problems.
It turns out I DO have an anterior open bite, which has now been revealed. The cause is posterior vertical maxillary excess, along with (I assume) anterior vertical maxillary deficiency (no tooth show at rest).
I am getting bi-max advancement of maxilla and mandible along with vertical reduction and advancement genioplasty of the chin.
Now, in regards to the open bite, will this correct itself on its own as it advances sagitally, I.e the anterior maxilla naturally comes down with advancement thus allowing for more tooth show and proper bite ?
Or will my surgeon have to impact the posterior max. IF SO, now that you know I have an open bite, how will this affect my mandible rotation ?
From what I understand, this will depend on how much is removed posteriorly and how much is brough down anteriorly. So probably the net affect would be 0, correct ?
Your presentation is somewhat confusing to me. You say you have you have anterior open bite and the cause is posterior vertical maxillary excess. OK, well PVME is treated with posterior impaction of the maxilla. But then you ask if your doc will have to impact the posterior maxilla.
If the cause of your jaw problems is posterior vertical max excess, PVME is treated with posterior impaction which is a clockwise rotation. If the cut out area is a wedge shape, the very front of the maxilla (where the 2 front teeth are) pretty much stays where it is and the maximum upward motion is to the very back of the maxilla. So bone removal is at minimum to front max where front teeth and at maximum where back teeth are. (d/dy where y is vertical distance decrease is function of horizontal distance traveled along the elongated wedge. Min at anterior maxilla. Max at posterior maxilla.)
Keeping in mind that the wedge section removal of the posterior impaction basically leaves the most anterior part of anterior maxilla pretty much where it was, what ever (front) tooth show you get will be a function of moving the maxilla 'forward' along the line (or plane) of the OP that is left after the wedge resection of the posterior impaction.
The angle of the OP left after the wedge section removal should describe a 'downward slope' (negative slope, DIAGONAL, which is normal for an OP to have). So 'forward' movement of the maxilla along this diagonal should kick up more tooth show. It will be a function of the inclination of the OP or 'steepness' of the diagonal. The steeper the inclination of the OP , the more tooth show you will get with 'forward' advancement along the new inclination of the OP (plane). [slope= 'hypotenuse'. Vertical displacement= hypotenuse X sin theta where theta is angle of inclination of OP]
Both the angle--number of degrees-- of Cw rotation and the number of degrees of the anterior open bite are needed to know in order to plug into the handy equation given prior: (CW rotation of mandibular plane) = (CW rotation of the maxilla) - (degrees of anterior open bite) for the net CW rotation. So a net rotation of the MP of 0 would only be when the number of degrees of anterior open bite=the same number of degrees as the CW rotation of the maxilla. But with no angle measures, the net rotation of the MP can't be estimated because all you know is what you don't know which is your docs aren't giving you much info other than that you're getting bimax and V reduction + advance for chin.
Is it possible they know you are doing this to look better but they are doing it because they see an indication to fix your bite and are wanting to withhold the planned displacement measures because there is chance the outcome does not meet up with aesthetic hopes for the surgery? I don't mean to make you paranoid but you should request a ceph displacement diagram where you can see the estimated prediction of the profile changes that go along with fixing the bite. Like is this private pay or insurance no charge?