What is happening in a posterior grafting CCW?

[Teddy Bones]

Forgive me if this a dumb question. You're removing portion of the bone in anterior impaction but could someone explain me what is happening in a posterior grafting CCW?
I don't consider myself a newbie in terms of jaw surgery knowledge (far from expert too) but I haven't found anything that makes sense on it. I wish there was a visual or something that could help.

Also, let's say we have a steep occlusal plane and both the maxilla and the mandible are pointing down. By doing CCW with anterior impaction, do we also cut and reposition and thus advance the mandible in a higher angle or do we advance in the same vector as the original?

[kavan]

One way to think about this is to visualize a WEDGE shape. For CCW anterior impaction, consider a wedge shape CUT OUT from the maxilla where the wedge is longer anteriorly and gets progressively shorter toward back of maxilla.

For CCW posterior DOWNGRAFT, consider a wedge shape ADDED to the maxilla (not a cut out from it as in CCW anterior impaction) where the wedge shape is longer posteriorly (back of maxilla) and gets progressively shorter toward front of maxilla.

Rotations done to maxilla, will in turn, affect a rotation to the mandible in the same direction (CW or CCW).

[Teddy Bones]

One way to think about this is to visualize a WEDGE shape. For CCW anterior impaction, consider a wedge shape CUT OUT from the maxilla where the wedge is longer anteriorly and gets progressively shorter toward back of maxilla.

For CCW posterior DOWNGRAFT, consider a wedge shape ADDED to the maxilla (not a cut out from it as in CCW anterior impaction) where the wedge shape is longer posteriorly (back of maxilla) and gets progressively shorter toward front of maxilla.

Rotations done to maxilla, will in turn, affect a rotation to the mandible in the same direction (CW or CCW).

Oh well, it makes sense this way, Im stupid  : P

About the mandible, does the surgeon advance the bone in the same vector as the original occlusal plane thus with the rotated maxilla, the posterior part of the rammus is mechanicaly moved forward (similar to when you jut) and "locks" forward in the new bite? If thats whats happening Im assuming it would be bad for your tmj?

Or they surgically CCW rotate the mandible by advancing it in a higher angle.
Or both can be done and it depends on the patients case?
There's a high chance im talking bs right now so Im sry for that.

I have a last question that I'd like you to answer me that's more important than the rest to me.
The way I see it CCW rotation removes existing bone and shortens the face. CCW rotation of the mandible raises the chin point aswell so your skull height gets reduced right? (chin to hairline)
And does the same thing happen via posterior downgrafting CCW? Basically there is no way that your occlusal plane can lift upwards and your skull height not shorten, am I right?

[kavan]

Oh well, it makes sense this way, Im stupid  : P

About the mandible, does the surgeon advance the bone in the same vector as the original occlusal plane thus with the rotated maxilla, the posterior part of the rammus is mechanicaly moved forward (similar to when you jut) and "locks" forward in the new bite? If thats whats happening Im assuming it would be bad for your tmj?

Or they surgically CCW rotate the mandible by advancing it in a higher angle.
Or both can be done and it depends on the patients case?
There's a high chance im talking bs right now so Im sry for that.

I have a last question that I'd like you to answer me that's more important than the rest to me.
The way I see it CCW rotation removes existing bone and shortens the face. CCW rotation of the mandible raises the chin point aswell so your skull height gets reduced right? (chin to hairline)
And does the same thing happen via posterior downgrafting CCW? Basically there is no way that your occlusal plane can lift upwards and your skull height not shorten, am I right?

Many of the concepts as to maxfax displacements, rotations, points, angles and planes relate to basic geometrical concepts. People who lack a 'connection' to basic grammar school geometry will have a very hard time understanding the basics of maxfax. Reason being they have little to relate it back to.

Rotation CCW, DECREASES the inclination of the occlusal plane. It CHANGES the occlusal plane. Since rotations to the maxilla, in turn, affect a rotation to the mandible in the same direction of the rotation, rotations to the maxilla  ALSO thereby decrease the angle of inclination the mandible has with the horizontal plane. It should follow that the vector of mandibular displacement will be along the changed inclination of mandibular plane that the maxillary rotation, in turn affected. Therefore, the surgeon does NOT displace the mandible along the same vector it would have to be moved in IF the maxilla WERE NOT rotated.

My initial post to you told you to think of an CCW anterior impaction as a wedge CUT OUT and that a CCW posterior downgraft as a wedge ADD ON. So, 'how you see' (all) CCW (rotations) as something removing existing bone does not reflect you digested my prior explanation.

CCW anterior impaction (wedge CUT OUT) where height of wedge is longer to anterior maxilla, will shorten an anteriorly long face (decreases vertical maxillary excess). CCW posterior DOWNGRAFT (wedge ADD ON) will lenghthen (or 'drop down) the posterior (back part) of the mandible. BOTH ccw AI and ccw PDG decrease angle of the occlusal plane (OP).

[Post bimax]

CCW rotation of the mandible raises the chin point aswell so your skull height gets reduced right? (chin to hairline)
And does the same thing happen via posterior downgrafting CCW? Basically there is no way that your occlusal plane can lift upwards and your skull height not shorten, am I right?

The isolated CCW rotation will vertically shorten the face from "hairline to chin" since the pogonion is rotating 'up', just as one end of a see-saw moves up when the other moves down.

However, it is possible that the final displacement of the pogonion will ultimately be 'down' depending on the size of BSSO.  Imagine a see-saw being pressed down, but at the same time magically elongating to a degree where the final position of the other end of the see-saw is still lower than its starting position.