Author Topic: Advice needed Anterior downgraft CW rotation  (Read 3188 times)

Dot

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Advice needed Anterior downgraft CW rotation
« on: July 27, 2024, 01:30:50 PM »
Hi
Advice appreciated
I had DJS couple years ago to treat class 3 open bite and my maxilla was impacted both posterior and anterior but differential not linear
And my lower jaw was setback and CW of mmc
turns out upper jaw was overimpacted and only showing 2mm on smiling looks BAD

I now need downgraft of anterior maxilla but problem is I don’t want to elongate my lower face from front view and my upper lip dropped from initial surgery don’t want further drop

so would a anterior downgraft with posterior impaction of same amount in mm ( eg 4 mm anterior downgraft & 4mm posterior impaction) keep the length the same as with CW rotation of maxilla the lower jaw rotates back? Or am I wrong?
Also, is extrusion of upper teeth with braces an alternative?
I know pics are helpful but I struggle to take pics with my current situation it’s distressing so I avoid but you get the gist hopefully

kavan

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Re: Advice needed Anterior downgraft CW rotation
« Reply #1 on: July 27, 2024, 04:10:00 PM »
Too much anterior impaction could be a trade off of getting the bite right. Whether the bite still would be 'right' or what new trade-offs may arise after what you are pondering is best worked out by a surgeon who has  computer stimulation design program. Consult with an ortho to determine how many millimeters can be pulled down for more upper tooth show. If you think your upper lip is too 'long', you could explore the option of a lip lift for more tooth exposure.
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Dot

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Re: Advice needed Anterior downgraft CW rotation
« Reply #2 on: July 27, 2024, 04:53:38 PM »
Thanks yeah I did try to enquire about lip lift but would make zero difference on its own as the jawbone is buried up too high so definitely will need to downgraft atleast 4mm so do you think the tracing ceph should accurately show the changes vertically I just can’t work out how to avoid elongating the face with a downgraft I will ask the surgeon if more posterior impaction can counteract it or not

kavan

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Re: Advice needed Anterior downgraft CW rotation
« Reply #3 on: July 27, 2024, 08:14:19 PM »
. Consider that posterior impaction  is CW-r and so is anterior downgraft. So, you better get all that worked out by a surgeon who has a computer simulation program to show/advice you about  tradeoffs.
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Dot

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Re: Advice needed Anterior downgraft CW rotation
« Reply #4 on: July 27, 2024, 09:38:52 PM »
Sure will..Thanks mate

kavan

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Re: Advice needed Anterior downgraft CW rotation
« Reply #5 on: July 28, 2024, 02:05:51 PM »
Here's how I look at it. But I could be wrong. So, all the more reason to cross reference with a surgeon as to potential trade-offs.

Assume an anterior downgraft of 'X' mm will rotate the maxilla-mandible complex CW-r by Y degrees.

Assume a symmetrical but opposite posterior impaction of 'X' will rotate the maxilla-mandible complex CW-r by Y degrees.

Since each rotation is is CW-r, they are additive. The total rotation would be 2Y degrees CW-r. It isn't a 'net' rotation of 2 opposite directions when one is subtracted from the other.

It could result in an UNWANTED total CW-r where the anterior front face could look all the more longer because the posterior impaction rotates upward (shortens) (in CW-r) but the anterior downgraft CW-r rotates the chin point downward and backwards.

Now, Y degree rotation can vary from person to person for every X mm of anterior downgraft or posterior impaction. But to keep the concept SIMPLE, let's say for every Xmm addition to one part and subtraction to the other part = Y degrees. So,
4mm addition to anterior max will effect a CW-r of 4 degrees and a 4mm subtraction to posterior max (impaction) will also effect a CW-r of 4 degrees. So, it doesn't matter what Y is for every X. What matters is that for X to be added to the front and X subtracted from the back, both are CW-rs and both added together can double the total CW-r which could affect a visually longer appearance to the frontal visage.
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For example, let's take each one individually and then add them.

1: Consider if you got only an anterior downgraft of 'X'mm but no posterior impaction. In EXCHANGE for the extra X mm frontal tooth show (which again is a CW-r), the CW-r of Y degrees, rotates the chin point down and backwards which in turn, will make the anterior face cast longer. The rotational position of the chin point affects how the face looks in frontal view.

2: Consider if you got  only a posterior impaction (CW-r) with no anterior downgraft. The back of the maxilla rotates upward and gets shorter. So, now you have some extra shortness in back which in turn will give LESS posterior tooth show because you are SUBTRACTING posterior tooth show from the smile. In effect, you would be 'adding' more 'shortness' to the overall tooth show

3: If you add both of those individual rotations together, you are adding X more frontal tooth show to the overall smile but also subtracting X tooth show from the back. Posterior impaction is CW-r but also an upward rotation at the back of jaw. Hence SHORTENING takes place there. Anterior downgraft is also CW-r but it's also rotating the chin point down and backwards which will cast the front face longer in frontal perspective. So, when the posterior shortening is equal to the anterior lengthening (of X mm) and Xmm rotates the MMcomplex Y degrees, when you add 2 CW-rs together, you can get a total rotation of 2 Y degrees. It isn't a 'net' rotation where one is subtracted from the other. It's a TOTAL rotation; a total CW-r. The impaction in back shortens in back and the downgraft in front elongates in front. So, the trade off of doing both could be the frontal view of face casting all the more longer.

Again, I could be wrong on this and your plan might work or I could be right on this and your plan might not work out so well. So, all the more reason you need to cross reference this with the surgeon as to the potential trade-offs.
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Dot

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Re: Advice needed Anterior downgraft CW rotation
« Reply #6 on: August 08, 2024, 12:57:53 PM »
wow that’s really interesting and so technical do you think looking at the ceph tracing is accurate enough to see if it will be longer or not I’m assuming by looking at the new chin and lower lip position on the tracing will determine that? Hoping it’s accurate enough

kavan

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Re: Advice needed Anterior downgraft CW rotation
« Reply #7 on: August 08, 2024, 02:11:46 PM »
wow that’s really interesting and so technical do you think looking at the ceph tracing is accurate enough to see if it will be longer or not I’m assuming by looking at the new chin and lower lip position on the tracing will determine that? Hoping it’s accurate enough

If you mean a ceph tracing that not only includes a present tracing but also an overlay of a new proposed contour diagram to give a visual of the plan proposal, that can be used as a guideline.
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