Recessed Jaws, What do you think?

[kavan]

Here is ceph of an 'ideal' relationship of the jaws and the teeth.



It is taken from an article where it's used as the type of ideal paradigm on which the Arnett analysis is based. Arnett analysis is based on people who DON'T need any maxfax surgery and that is so BECAUSE with reference to a plumb line vertical dropped from different places, the other structures of the face are in 'right' orientation relative to the verticals. They would also have horizonts that were perpendicular to those verticals.

Ref= https://www.sciencedirect.com/science/article/pii/S2395921516300575#fig0015

NOTE the PLUMB LINE vertical which shows as a chain (at back of head). The line is in direction of GRAVITY. So it is a PURE vertical. Note that a line dropped from the bottom of nose bone is PARALLEL and hence also a PURE vertical (plumb line vertical). Note this vertical passes through subnasa, runs pretty close to upper lip and chin point is posterior to it.

It is something where the PLUMB LINE is the 'TVL' on that person.

If that person sent this ceph to cephX, cephX would (hopefully) NOT rotate it. Since the person is used as a 'model' to SHOW where the Arnett TVL should be found and where the soft tissue profile is RELATIVE to it, it's not a situation where cephX would just rotate it CW by DEFAULT or to 'standardize' it. So, that person in the ceph has a TVL that's parallel with a plumb line vertical, aligned along the line of gravity. They also have pure horizonts perpendicular to it. So, the situation is one where person in ceph IS the standard already. Not one where their ceph has to be rotated for a TVL standard.

Situations where cephX or a maxfax would rotate a ceph and rotate it CW would be when a vertical plumb line (again a vertical parallel to the line of gravity and the line of the ceph stat on their ceph) would be when a plumb line vertical dropped from near the bottom of the nose bone had parts of the soft tissue profile too much IN FRONT of it. That is pretty much and almost EXACTLY what was done in your ceph.

Note that when a plumb line vertical is dropped from near the bottom of your nose bone, it does NOT pass through subnasa, your upper lip is IN FRONT of it as is your chin. So, in THAT situation, they rotated YOUR ceph the amount they did. It's the only way to get a TVL dropped from near bottom of nose bone to also intersect with subnasa, run close to your upper lip. The rest of it where areas are BEHIND it is use as reference for advancing jaws and chin.

The fact that TOO MUCH of your face was IN FRONT of PLUMB LINE vertical dropped from near the bottom of your nose bone was  WHY they rotated your ceph. They rotated it CW so that a TVL (I adjusted the TVL) dropped from near the bottom of your nose bone would pass through your subnasa and run along close to your upper lip. From there, they use it as reference to for example maybe flip your upper lip in front of it a little and, of course to advance the mandible and chin.

Again, cephX isn't going to rotate EVERYONE'S ceph. It's not a default process where everyone's ceph needs to be rotatated just because yours needed to be rotated. Certainly not the amount yours was. Your's needed to be rotated because a plumb line vertical dropped from the bottom of your nose bone--in no uncertain terms--REVEALED too much of your lower face was IN FRONT of that line. That should be intuitively obvious based on noting that your unrotated ceph WHEN rotated DIDN'T HAVE too much of your lower face in front of it.

Also, look at the example used a an ideal paradigm for Arnett's TVL where when the plumb line is dropped from near the bottom of the person's nose bone, the rest of their soft tissue profile is where it 'should be' with reference to that line. Hence, not a thing where cephx would rotate a ceph that looked like that. Nor an example of someone needing maxfax surgery at all given their ceph is used as an example of where Arnett wants to place a TVL that parts of the face are meant to be relative to.

Don't get me wrong. I'ts not 'wrong' to rotate someone's ceph.  But you want to look at (in example of CW rotating it) IF parts of there face are too forward to the Arnett TVL when a plumb line vertical is dropped from  near bottom of their nose bone. IF they are , you rotate to where a TVL dropped from there would also pass through subnasa, and go along the upper lip, basically like they did to yours. Also, to better 'ID' with someone else's profile, you'd look for class 2 Div 2 deep bite.

ETA: Diagrams included in this post.

[Dogmatix]

YES. The construct of what they call the TVL isn't really parallel to the plumb line of gravity. It's diagonally oriented away from that as to be perpendicular to an FH when the FH isn't a pure horizont.  Now the boring part:

Gunson uses ARNETT'S ceph measure program/analysis and I think a number of docs in Spain do too, 'Nemo FAB'..something like that. Maybe in addition to Dolphin. But could be instead.

It's based on  aesthetic paradigms of people who have an 'ideal' balance with reference to the plumb line of gravity and also horizontal relationships that run perfectly perpendicular to it who very well, might have FH that are true horizonts. The aim is to bring patients, who deviate from that, CLOSER to those types of relationships with reference to the soft tissue profile.

An example of an person having the ideal paradigm the Arnett analysis is based on would be someone where a plumb line vertical would pass through around the bottom of their nose bone, through subnasa, the lips would flip a little forward to it and the Pog chin point would be posterior to it especially on a female. They would also have planes perpendicular to that line. For example, if you passed a horizont through subnasa, ANS-PNS would be pretty much aligned to it and their FH, very well could be a pure horizont.

So, basically, the paradigm used for this comes from people who have orientations of parts relative to the PLUMB LINE of gravity and orientations relative to a pure horizont. Their natural structure is oriented that way.

With regard to rotating a ceph, they kind of know that someone say with recession to lower face, would tend to tilt their head up to compensate for some recession there or they can just tell, the person is doing such and has the wrong tilt for what they want to reference for surgery plan. So, they rotate downward with reference to where they want to CONSTRUCT a 'vertical' to pass through aproximately bottom of nose bone, through subnasa and along upper lip. But in reality, with reference to the plumb line of gravity it's not a 'true' vertical . The true line of gravity is seen on the ceph stat. So, in essence, what say Gunson, would call a 'true' vertical after ROTATING a ceph where a  perpendicular would pass through the places he wants it to pass through, the construct is a DIAGONAL oriented away from the plumb line of gravity.

That's all well and good because it pretty much aimed at getting closer to the relationship of ideal alignment of the soft tissue profile that people with orientations aligned with true plumb line of gravity and pure horizonts have because the construct of what they call the 'TVL' will be perpendicular to a 'horizontal' plane that's not a 'pure' horizont eg an FH that's oriented away from a pure horizont.

In your case, it looks like they did a good job aligning your head tilt for the ceph. The  PLUMB LINE vertical (green one I drew parallel to vertical of ceph stat) passes through bottom of nose bone, subnasa and pretty much along upper lip which is kind of close to the Gunson type TVL. From there, they would look at the pure horizont perpendicular to it where they can see your FH is about 4 degrees rotated away from that. So, that black line which they CALL the 'TVL' in your case is a construct oriented 4 degrees AWAY from the plumb line of gravity as to be PERPENDICULAR to your FH.

I just want to clarify. It's not that I looked at my own ceph, saw 7 degree rotation and thought all cephs should rotate like that. I made a real attempt to mark the Or and Po point and then rotate relative to this and it happened to be 6.2 something degrees and happened to be similar to my example. Because I saw such big difference with the FH plane and the cephalostatic hz, I felt the need to rotate it to show my line of thought. I fully understand that cephx doesn't take all cephs, rotate 7 degree, if it was so we could have very fun with their service and pre-rotate and send in cephs. My own example was just to show that cephs can be taken at any angle and in my case I don't remember getting any instructions at all, not sure if I maybe even was that I should rest my chin on something, which would f**k up the rotation entirely. It's 2 years ago I think, dont remember nor reflected on this then.

[kavan]

I just want to clarify. It's not that I looked at my own ceph, saw 7 degree rotation and thought all cephs should rotate like that. I made a real attempt to mark the Or and Po point and then rotate relative to this and it happened to be 6.2 something degrees and happened to be similar to my example. Because I saw such big difference with the FH plane and the cephalostatic hz, I felt the need to rotate it to show my line of thought. I fully understand that cephx doesn't take all cephs, rotate 7 degree, if it was so we could have very fun with their service and pre-rotate and send in cephs. My own example was just to show that cephs can be taken at any angle and in my case I don't remember getting any instructions at all, not sure if I maybe even was that I should rest my chin on something, which would f**k up the rotation entirely. It's 2 years ago I think, dont remember nor reflected on this then.

I made 2 other posts directly to you. Did you mean to clarify on the post I made to you or the one to April?

[Dogmatix]

I made 2 other posts directly to you. Did you mean to clarify on the post I made to you or the one to April?

I meant to clarify so you understand where my competence level is, because you make some explanations that seems to assume I have no idea in the response I quoted, that was a response to me.

Like

It's not something where if they rotate person A's ceph by X degrees, then person A rotates person B's ceph by same X degrees. It's not like that.

No of course. I do have a masters degree in physics and some common sense. The question about rotation fully resolves to if I managed to spot Po and Or correctly or not.

Edit: I realize I maybe quoted the wrong response when I was on my phone.

[InvisalignOnly]

Can you please tell me what I should do to fix my recessed jaws and get enough projection? I'm thinking about getting bimax. What should I do to get attractive forward-projected mandible and maxilla?

I said this before and I know you (and perhaps others) do not like my answer but I saw your post and feel like it's my 'duty' to react - this is the last time I comment on any of your threads, I'll make my point and then leave you alone.

So, as I said before, you are a young, good looking guy as you are now, with a great bite, as we can see in the scan. You are thinking of getting very serious, invasive surgery that can have negative consequences for the rest of your life, for what? Because you think it would make you look better? Before you start paying for someone to break your face, you should really sit down with yourself or preferably a trusted friend / family member / psychologist and try to figure out what makes you so insecure about your looks, when objectively speaking you already look fine and your bite is fine.

I can understand if you want fillers / a chin implant / maybe even genio etc. but bimax, what for? Do you really understand what is involved and the risks? This kind of surgery is for people like myself that look quite different from the 'norm' and have health problems associated with that, and even then it might not be worth it in many cases. For someone like you, it's madness to even contemplate it.

I personally think if you carry on like this, sooner or later you will end up in the hands of an unscrupulous surgeon that's happy to take your money and will leave you with health problems and potentially making you look worse, not better. This is my two cents, and I hope it does not happen to you and that you can start feeling better about yourself in a different way that does not involve bimax surgery.

[kavan]

I meant to clarify so you understand where my competence level is, because you make some explanations that seems to assume I have no idea in the response I quoted, that was a response to me.

Like
No of course. I do have a masters degree in physics and some common sense. The question about rotation fully resolves to if I managed to spot Po and Or correctly or not.

I'm sorry if you may have felt I was chastising you for that. It's just that I wanted to elaborate more on how CW rotation of a ceph and extent of it is a direct function of whether or not a vertical dropped from a certain place is consistent or inconsistent with where the CCW 'gurus' want it to be near. If the former, not much rotation. If the latter, then rotation for the vertical to 'hit' certain places and to reveal what other places need to be displaced relative to it.

It was in spirit of teaching/explaining because to me it seemed it would be helpful to fill in some gaps if I elaborated more to the whens and whys (or why not) they rotate a ceph. Perhaps 'circumstantial' that your rotation of SH was same amount they rotated you and also in light of your telling him his profile was 'quite similar to yours'. I would not have gone through all that extent of an explanation if I had any reason to believe you lacked the type of background as basis to recipient of it.

As to having a masters in physics, I think that's great. Are you familiar with Walter Lewin and Phillip Morrison of MIT, 2 world renowned experts in physics? Both were my physics professors. I was one of Walter's favorite students. Wasn't a physics major though. Although, that has little to do with the topic here (and was long time ago) but if you're going to bring physics into the equation (no pun intended), then consider that an 'MIT type' is going to have the tendency to be extremely rigorous in observations having to do with stuff like rotations as to how they would apply to one situation but not another.

[Dogmatix]

I'm sorry if you may have felt I was chastising you for that. It's just that I wanted to elaborate more on how CW rotation of a ceph and extent of it is a direct function of whether or not a vertical dropped from a certain place is consistent or inconsistent with where the CCW 'gurus' want it to be near. If the former, not much rotation. If the latter, then rotation for the vertical to 'hit' certain places and to reveal what other places need to be displaced relative to it.

It was in spirit of teaching/explaining because to me it seemed it would be helpful to fill in some gaps if I elaborated more to the whens and whys (or why not) they rotate a ceph. Perhaps 'circumstantial' that your rotation of SH was same amount they rotated you and also in light of your telling him his profile was 'quite similar to yours'. I would not have gone through all that extent of an explanation if I had any reason to believe you lacked the type of background as basis to recipient of it.

As to having a masters in physics, I think that's great. Are you familiar with Walter Lewin and Phillip Morrison of MIT, 2 world renowned experts in physics? Both were my physics professors. I was one of Walter's favorite students. Wasn't a physics major though. Although, that has little to do with the topic here (and was long time ago) but if you're going to bring physics into the equation (no pun intended), then consider that an 'MIT type' is going to have the tendency to be extremely rigorous in observations having to do with stuff like rotations as to how they would apply to one situation but not another.

If they don't have a constant named after them, I probably don't know about them . I started studying physics after high school when I was dead serious about understanding how the world works. After a couple of years I understood how everything resolves to a quantum chaos, and not the deterministic world I wanted to find and understand. So I drifted away from physics and didn't do more courses than I had to to get my degree and filled up with mathematics and computer science instead. I thought I read in a thread you were European and not American?

Not very unlike how I dived into jaw surgery, wanting to know everything, and then realize how chaotic it is and how much of of the "truths" that confuse me actually are derived from opinions. The more I hear about this business and learn, I revert to thinking the patients should be given more freedome to decide on their treatments and planning. They have most probably spent a lot time contemplating about their situation and issues and know what they want to do, of course with the guidance and experience of the one who will execute the treatment.

Enough about me.
The frankfort horizon have a strict definition. You also talk about "True Horizon" and "Pure Horizon". How do you define these? Are these reference lines you use to orientate the skull, and if so, how do you find them? I've had my fair share of mess in my head about how I should hold my head "correct". Going to chiropractors, physiotherapists etc and well, the more people you ask the more "good" tips you get. Some people talk about "Natural head posture", but it's very vague what is natural. I figure, if you have to force it, it's probably not natural, but also jaw imbalance and narrow airways can force or promote an unnatural posture. Forward head posture is in fact strongly linked to OSA.

That's why I like the FH orientation, it's not something you can alter by holding your head in different positions and wonder if you hold it "correct". Just a question, are you saying I marked the Po incorrectly on SH's ceph, or are you saying it's maybe incorrect and we can't tell?

The thing about ceph orientation and planning is that it's very interesting how the skull is rotated in the displacement diagrams. I don't think most people realize that the displacements can only be compared if the orientation is the same. The A-P and Vertical displacement meassurements depend on the orientation. In the extreme case you can take a ceph, rotate it 90 degrees and ta-da, the pure A-P displacement is now a pure vertical displacement in the new coordinate system. That's not so hard to understand, but if you compare displacement diagrams from 2 surgeons, you also need to know if they use same standard when orientating the skull. 5mm A-P advancement maybe compare to 3mm A-P advancement and a vertical displacement in another orientation. I think there is a small such difference in my plans from different surgeons e.g. The absolute distance in displacement is absolute though.

[kavan]

If they don't have a constant named after them, I probably don't know about them . I started studying physics after high school when I was dead serious about understanding how the world works. After a couple of years I understood how everything resolves to a quantum chaos, and not the deterministic world I wanted to find and understand. So I drifted away from physics and didn't do more courses than I had to to get my degree and filled up with mathematics and computer science instead. I thought I read in a thread you were European and not American?

Not very unlike how I dived into jaw surgery, wanting to know everything, and then realize how chaotic it is and how much of of the "truths" that confuse me actually are derived from opinions. The more I hear about this business and learn, I revert to thinking the patients should be given more freedome to decide on their treatments and planning. They have most probably spent a lot time contemplating about their situation and issues and know what they want to do, of course with the guidance and experience of the one who will execute the treatment.

Enough about me.
The frankfort horizon have a strict definition. You also talk about "True Horizon" and "Pure Horizon". How do you define these? Are these reference lines you use to orientate the skull, and if so, how do you find them? I've had my fair share of mess in my head about how I should hold my head "correct". Going to chiropractors, physiotherapists etc and well, the more people you ask the more "good" tips you get. Some people talk about "Natural head posture", but it's very vague what is natural. I figure, if you have to force it, it's probably not natural, but also jaw imbalance and narrow airways can force or promote an unnatural posture. Forward head posture is in fact strongly linked to OSA.

That's why I like the FH orientation, it's not something you can alter by holding your head in different positions and wonder if you hold it "correct". Just a question, are you saying I marked the Po incorrectly on SH's ceph, or are you saying it's maybe incorrect and we can't tell?

The thing about ceph orientation and planning is that it's very interesting how the skull is rotated in the displacement diagrams. I don't think most people realize that the displacements can only be compared if the orientation is the same. The A-P and Vertical displacement meassurements depend on the orientation. In the extreme case you can take a ceph, rotate it 90 degrees and ta-da, the pure A-P displacement is now a pure vertical displacement in the new coordinate system. That's not so hard to understand, but if you compare displacement diagrams from 2 surgeons, you also need to know if they use same standard when orientating the skull. 5mm A-P advancement maybe compare to 3mm A-P advancement and a vertical displacement in another orientation. I think there is a small such difference in my plans from different surgeons e.g. The absolute distance in displacement is absolute though.

Well, I guess you don't have a T shirt with Maxwell's equations on them. Just surprised that a physics major wouldn't know of those professors. As to quantum chaos, 'the' guy on that is Richard Feynman, well known in venue of quantum theory. He worked on Manhattan project with Phillip Morrison. But is better known for his lectures on quantum theory. As to stopping the study of physics because 'everything resolved to quantum chaos'. Rest assured the laws Newtownian mechanics still exist as orderly physical laws.  Any physics major should check Walter Lewin out. Here's a video of him giving a lecture where he uses a wrecking ball (pendulum) aimed at his face to demonstrate concept of conservation of mechanical energy. https://www.youtube.com/watch?v=BAdDvCwkZeo  at 2:11 As to reading I was European, whether I am or not would have nothing to with being MIT grad.

I know what the definition is of the Frankort horizontal: Or to Po.  When I talk about 'true' or 'pure' horizont, it's to stress that the FH is NOT perfectly horizontal in everyone. If you're asking what 'true' or 'pure' horizontal could mean, it means perfectly horizontal, parallel with the horizon, inclined 0% away from a horizontal line, the level at surface of water. In terms of maxfax; A-P direction = horizontal displacement component.

As to your marking it on SH's ceph, I'm saying I'm not sure you did because it's hard to find and also that I found a horizontal on his ceph that also could be the point. So, 50/50 and I found no basis in your likening your profile to his as to rotate his ceph as yours was rotated.

As to head orientation in a ceph, it can be a matter of the type of analysis and surgery the doctor does. An easy way to see if skull is oriented differently in 2 cephs would be to look at the S-N line, compare to a horizont to look for changes in angle of inclination. S-N is easiest to locate.

[Dogmatix]

I know what the definition is of the Frankort horizontal: Or to Po.  When I talk about 'true' or 'pure' horizont, it's to stress that the FH is NOT perfectly horizontal in everyone. If you're asking what 'true' or 'pure' horizontal could mean, it means perfectly horizontal, parallel with the horizon, inclined 0% away from a horizontal line, the level at surface of water. In terms of maxfax; A-P direction = horizontal displacement component. Likewise the term I use to differentiate something called the 'True Vertical Line' or 'TVL' from the actual vertical direction of gravity is the 'plumb line vertical'.

Ok. A true or pure horizon is parallel to sea level. Check, this is a strict definition that's easy to understand.

the FH is NOT perfectly horizontal in everyone

This is where it gets complicated. When, how, what? FH is a line between 2 points and the head is mobile. A line that is mobile can always be positioned parallel to another line. So I must assume you mean that the head "at rest", in "natural head position" or something
else does not put the FH parallel to sea level in all people. But how do you effectively find out if your FH is parallel to sea level or how much it deviates and what is "natural" for you? Trying to hold your head "naturally" is like trying to feel what it feels like to not think about anything. *Ah, now I got it, doh, didn't I tell you to stop thinking*. It's like schroedingers head position, you can't both do it and meassure it. Everytime you want to meassure it you become conscious and may alter it.

It gets even more complicated when we conclude e.g that it's "very common" for those with a situation like me to tilt the head up so the ceph needs to be rotated 7 degrees. And also when we know that OSA and bite deficiencies can be linked with promoting different unhealthy head postures. The goal for a successful surgery with such posture should be to decompensate the bite or breathing problem so it promotes a normal head posture. But how can you quantify what is normal on a person where the situation you're treating is causing a head posture, and also assuming that the FH which could be a strict reference is not perfectly horizontal in everyone?

I would say that FH is one of the best tools there is for this. FH is absolute regardless of posture and sea level is absolute, put those parallel and you have as good starting point as you're gonna get. You also showed some other useful techniques, like looking at the nose bone etc. I think any way it's twisted, defining normal or natural is impossible. The ceph rotation needs to be done by some approximation and assumption that is standardized.

[kavan]

Ok. A true or pure horizon is parallel to sea level. Check, this is a strict definition that's easy to understand.
This is where it gets complicated. When, how, what? FH is a line between 2 points and the head is mobile. A line that is mobile can always be positioned parallel to another line. So I must assume you mean that the head "at rest", in "natural head position" or something
else does not put the FH parallel to sea level in all people. But how do you effectively find out if your FH is parallel to sea level or how much it deviates and what is "natural" for you? Trying to hold your head "naturally" is like trying to feel what it feels like to not think about anything. *Ah, now I got it, doh, didn't I tell you to stop thinking*. It's like schroedingers head position, you can't both do it and meassure it. Everytime you want to meassure it you become conscious and may alter it.

It gets even more complicated when we conclude e.g that it's "very common" for those with a situation like me to tilt the head up so the ceph needs to be rotated 7 degrees. And also when we know that OSA and bite deficiencies can be linked with promoting different unhealthy head postures. The goal for a successful surgery with such posture should be to decompensate the bite or breathing problem so it promotes a normal head posture. But how can you quantify what is normal on a person where the situation you're treating is causing a head posture, and also assuming that the FH which could be a strict reference is not perfectly horizontal in everyone?

I would say that FH is one of the best tools there is for this. FH is absolute regardless of posture and sea level is absolute, put those parallel and you have as good starting point as you're gonna get. You also showed some other useful techniques, like looking at the nose bone etc. I think any way it's twisted, defining normal or natural is impossible. The ceph rotation needs to be done by some approximation and assumption that is standardized.

Well, check the definitions I gave with that which were same concept.

I don't know what's so hard to understand that the FH isn't going to be horizontal in all people. Are you confusing Schroedinger's cat with the Heisenberg uncertainty principle; position and velocity can't both be measured exactly, at the same time?

So, which of my statements really triggered you this one?...

'It's not something where if [cephX] rotates person A's ceph by X degrees, then person A rotates person B's ceph by same X degrees. It's not like that.'

[april]

Gunson uses ARNETT'S ceph measure program/analysis and I think a number of docs in Spain do too, 'Nemo FAB'..something like that. Maybe in addition to Dolphin. But could be instead

I think in addition to. Maybe for the 3d planning they use NemoFAB but for the 2d plans they use Dolphin. If you look at the bottom of any G plan it says: "These images are for predictions only - actual treatment results may vary. Photos electronically simulated using the Dolphin Digital Imaging System".

I saw Dolphin being used by the other surgeon and it has the Arnett Gunson FAB analysis also built-in. It basically goes through a set of pre-defined steps, and those steps create a plan that matches the ideal profile. But of course, not all surgeons can actually DO what A&G can do, so even if a surgeon is using the same FAB analysis/program they might not be able to fully follow all the steps.

Head posture is like the biggest jaw surgery mystery. In one of their articles A&G say "Patients do not carry their heads with Frankfort horizontal parallel to the floor; therefore, Frankfort horizontal should not dictate the head posture used for facial treatment planning. " ... Yet Dogmatix's, my own, and some others' plans from Gunson are all orientated that way. I was going to guess it was because we did Gunson digital consults and weren't examined in person? But that doesn't explain why other surgeons are using FH too.

I read your explanations about the lines and I think I understand from what you're saying that the subjects Arnett created his analysis off, would have had ideal lines and by rotating they get closer to that starting point? (lol so NOT a physics/maths major here! I stayed faaar away from those and did all arts/humanities)

In your case, it looks like they did a good job aligning your head tilt for the ceph. The  PLUMB LINE vertical (green one I drew parallel to vertical of ceph stat) passes through bottom of nose bone, subnasa and pretty much along upper lip which is kind of close to the Gunson type TVL. From there, they would look at the pure horizont perpendicular to it where they can see your FH is about 4 degrees rotated away from that. So, that black line which they CALL the 'TVL' in your case is a construct oriented 4 degrees AWAY from the plumb line of gravity as to be PERPENDICULAR to your FH.

Yeah with that xray my upper lip is close to the green/plumb-line true vertical. But once it's rotated my lips and other structures become further away from the 'new' TVL.

The only reason I care about head posture is that rotating the xray away from the TVL then necessitates a far more complex plan to get those structures back in the correct positions. The more the ceph is tilted, the more complicated the plan becomes. But I do have pretty bad forward head posture IRL and I also have a reverse curve to my neck. Instead of the neck naturally curving like ) mine is starting to curve like (. I suppose if my posture was corrected then my head could be tilted more like the new TVL.

[Dogmatix]

Well, check the definitions I gave with that which were same concept.

I don't know what's so hard to understand that the FH isn't going to be horizontal in all people. Are you confusing Schroedinger's cat with the Heisenberg uncertainty principle; position and velocity can't both be measured exactly, at the same time?

So, which of my statements really triggered you this one?...

'It's not something where if [cephX] rotates person A's ceph by X degrees, then person A rotates person B's ceph by same X degrees. It's not like that.'

Sure, Heisenberg uncertainty principle is maybe a better analogy, but it doesn't involve threatening to kill a kitten and I was mostly trying to joke a bit. Exclude this if it just caused confusion.

I'm not sure if I can explain further why it's hard for me to understand that FH is not horizontal in all persons. Sure, I can agree to that, but then I want another standard or reference to use that can tell how far from FH a person is. That's a measurement that needs to be quantified to know this. A provoking statement can be that FH is horizontal in all persons, everyone can hold their head with FH parallel to sea level.

[kavan]

I think in addition to. Maybe for the 3d planning they use NemoFAB but for the 2d plans they use Dolphin. If you look at the bottom of any G plan it says: "These images are for predictions only - actual treatment results may vary. Photos electronically simulated using the Dolphin Digital Imaging System".

I saw Dolphin being used by the other surgeon and it has the Arnett Gunson FAB analysis also built-in. It basically goes through a set of pre-defined steps, and those steps create a plan that matches the ideal profile. But of course, not all surgeons can actually DO what A&G can do, so even if a surgeon is using the same FAB analysis/program they might not be able to fully follow all the steps.

Head posture is like the biggest jaw surgery mystery. In one of their articles A&G say "Patients do not carry their heads with Frankfort horizontal parallel to the floor; therefore, Frankfort horizontal should not dictate the head posture used for facial treatment planning. " ... Yet Dogmatix's, my own, and some others' plans from Gunson are all orientated that way. I was going to guess it was because we did Gunson digital consults and weren't examined in person? But that doesn't explain why other surgeons are using FH too.

I read your explanations about the lines and I think I understand from what you're saying that the subjects Arnett created his analysis off, would have had ideal lines and by rotating they get closer to that starting point? (lol so NOT a physics/maths major here! I stayed faaar away from those and did all arts/humanities)

Yeah with that xray my upper lip is close to the green/plumb-line true vertical. But once it's rotated my lips and other structures become further away from the 'new' TVL.

The only reason I care about head posture is that rotating the xray away from the TVL then necessitates a far more complex plan to get those structures back in the correct positions. The more the ceph is tilted, the more complicated the plan becomes. But I do have pretty bad forward head posture IRL and I also have a reverse curve to my neck. Instead of the neck naturally curving like ) mine is starting to curve like (. I suppose if my posture was corrected then my head could be tilted more like the new TVL.

OK, so in addition to. There used to be a video on the NemoFAB website with Arnett describing sleep apnea cases. For that, he showed the 2D ceph displacement diagrams from NemoFAB. You know those Gunson diagrams people get where the background is blue and the numbers have different colors. He was showing that one. But good observation. I just looked at someone's ceph displacement diagram (from about 4 years ago) and it did say: Photos electronically simulated using the Dolphin Digital Imaging System" (in small print). So, I guess that means the NemoFAB 'program' is compatable with Dolphin where surgeons are going to be very likely to already have Dolphin.

Yes, indeed, there is no uniform agreement on head positioning and there are head positions that compensate for recession to jaw (uptilt of head). Yet enough agreement that an individual looking straight ahead, at eye level, into a distant mirror, will have a head position parallel to the plane of the FH. (Ceph also has to show the plumb line vertical.) But once, the ear things are put in, there could be something about them where the people have the type of ear holes where they adjust head to make the ear things more comfortable. So, given the Po point is hard to find and Po 'ear thing' is easier, that can become something where some say the ear thing can scew the FH.

The FH, is in fact, an important reference line they look for. On all of Gunson's ceph displacement 2-D proposals I've seen (the ones people usually get), they show the Po and Or points for the FH. So, ya, the FH is referenced. Although it might not be found on the ceph as a line parallel to the floor (which was your case), they reference so a line will run perpendicular to it (meet at 90 degree angle).

Now, as to whether the FH is a true horizont on everyone, Frankfort had actual skulls on the table where he found such on the skulls he put on the table. But you just can't put people's skulls on the table to see if they have it. So, there will be people who have it that way and those who don't. I've come across articles that say it isn't horizontal, particularly in people haveing dentofacial deformities.  I've also come across ceph diagrams where even in people who don't have deformities, the FH is not found as a true horizont. Here is example are some examples. First comes from a link BUT link had all these JUNK characters in it which would have filled up the page. but here's a snip:

".... it should be kept in mind that the inclination of the
Frankfort horizontal plane, as with all anatomical reference planes, is unlikely to be coincident with the true horizontal, particularly in a patient with a dentofacial or
craniofacial deformity. ...

Heres, a ceph from some 'normal' ethnic populations where on the tracing you can see FH isn't a horizont.
https://d3i71xaburhd42.cloudfront.net/2048497d4165a6bd9659c3ca9f8753cc0b543db6/2-Figure1-1.png
In this one, they are using the Steiner analysis.

So, those are 2 situations where they are not taking the FH as 'be it and end all'.

In the former example, the author just basically said to CHOOSE a horizont that would be compatible with a vertical (as opposed to a vertical that was perpendicular to an off kilter FH or even thinking about adjusting an off kilter FH to be horizontal )

Now back to Gunson and those who use the Arnett system, they certainly take note of the FH and they may adjust a ceph to it. But I do think they also have the option of choosing any horizont they feel will be compatable with the TVL they construct....and let's face it, NOBODY actually sees ANY of those scull points found on a ceph. If they can make the profile 'right' and balanced so it looks better to an on looker, in particular the person looking in the mirror, that's the goal.

Perhaps that helps shed some light as to why Gunson said what he did in the article he wrote where FH was not that important but also that he uses it or adjusts to it. I think his message in that article could have been; 'We don't need construct a TVL perpendicular to the FH in EVERY case if just using a CONSTRUCT of a horizont to SUBSTITUTE for the FH would work better.' This could also be so with other docs using Arnett type analysis. It could even possibly explain WHY the ones who use it kick up better aesthetic outcomes. Could it be because their not 'slaves' to these 'horizontal' planes and BUT OF COURSE, want to see wher the FH is on someone?

As to some of the subjects Arnett created his analysis off, they would already have the the ideals with no need to rotate them. They've already got the TVL where it's wanted and most likely the FH that is parallel to the floor. If you look at the photos from the article I linked to, you will see the cephs had a plumb line chain in the ceph person as example was not rotated and just example of the ideal balance.

As to your not studying physics, LOL, at MIT, not doing so was not an option. I think Liberal Arts major is actually better course of study. I use to take a lot of Fine Arts/Art History courses at Harvard (cross registration) and helped defray tuition by writing papers on that for MIT pre-meds. 'Go take Fine Arts 101 at Harvard. Don't worry, you'll get an A. I'll write your paper.'

[kavan]

Sure, Heisenberg uncertainty principle is maybe a better analogy, but it doesn't involve threatening to kill a kitten and I was mostly trying to joke a bit. Exclude this if it just caused confusion.

I'm not sure if I can explain further why it's hard for me to understand that FH is not horizontal in all persons. Sure, I can agree to that, but then I want another standard or reference to use that can tell how far from FH a person is. That's a measurement that needs to be quantified to know this. A provoking statement can be that FH is horizontal in all persons, everyone can hold their head with FH parallel to sea level.

It's better to say 'true horizontal' or FH parallel to floor. It's because articles about that use those terms.

...as to whether the FH is a true horizont on everyone, Frankfort had actual skulls on the table where he found such on the skulls he put on the table. But you just can't put people's skulls on the table to see if they have it. So, there will be people who have it that way and those who don't. I've come across articles that say it isn't horizontal, particularly in people having dentofacial deformities.  I've also come across ceph diagrams where even in people who don't have deformities, the FH is not found as a true horizont. Here is example are some examples. First comes from a link BUT link had all these JUNK characters in it which would have filled up the page. but here's a snip:

".... it should be kept in mind that the inclination of the
Frankfort horizontal plane, as with all anatomical reference planes, is unlikely to be coincident with the true horizontal, particularly in a patient with a dentofacial or
craniofacial deformity. ...

Heres, a ceph from some 'normal' ethnic populations where on the tracing you can see FH isn't a horizont.
https://d3i71xaburhd42.cloudfront.net/2048497d4165a6bd9659c3ca9f8753cc0b543db6/2-Figure1-1.png
In this one, they are using the Steiner analysis.

So, those are 2 situations...