Ceph: Searching for mean angle between occlusal plane and mandibular plane

[katapult2]

Hey,

I'm searching for mean angle between occlusal plane and mandibular plane and the corresponding standard deviation. Is out there a study that measures this angle?

best regards,
Katapult

[XXRyanXXL]

Your going to find this information when you have a Ceph prepared by an Oral Surgeon.
He will input your age and sex, and it will plot out a histogram like line graph that corresponds to the normal, and std. deviations from the normal according to an advance xray that computes this information.
Let me give you an example that was prepared for me.

35 Year old Male
                                                        Value   Norm     Std Dev.
FMA (MP-FH) (degrees symbol)         40.1       24.6         4.1 (red)           line graph here with plotted normals
Occ Plane to SN (degrees)                    10.6    8.7          2.4  (Black)


I cannot find any measurement on the Ceph that indicates mean angle between these. I'm not a surgeon, I have no way of deciphering what the rest of the measurements mean. There are some 20+ more measurements. Ask an oral surgeon.

[katapult2]

Your going to find this information when you have a Ceph prepared by an Oral Surgeon.
He will input your age and sex, and it will plot out a histogram like line graph that corresponds to the normal, and std. deviations from the normal according to an advance xray that computes this information.
Let me give you an example that was prepared for me.

35 Year old Male
                                                        Value   Norm     Std Dev.
FMA (MP-FH) (degrees symbol)         40.1       24.6         4.1 (red)           line graph here with plotted normals
Occ Plane to SN (degrees)                    10.6    8.7          2.4  (Black)


I cannot find any measurement on the Ceph that indicates mean angle between these. I'm not a surgeon, I have no way of deciphering what the rest of the measurements mean. There are some 20+ more measurements. Ask an oral surgeon.

I know this procedure. I have a DVT and there is a ceph included. I analyse my Cephs for my own with some data from the studys from Downs, Steiner, Mc Namara and so on...
But i cant find any mean angle (and SD) between occlusal plane and mandibular plane. This Value would help me a lot to for my analysis.

[kjohnt]

You should be able to find the mean between OP and a fixed craniofacial line such as Frankfurt horizontal, then mean between MP and Frankfurt horizontal, then figure out the difference.  If using Arnett's analysis you'd use the True Vertical Line instead of a fixed line.  I can do some digging at home if you still can't find your answer.

The relationship between OP and MP is less meaningful because one or both could be off of the desired and can be modified with jaw surgery and/or other cosmetic surgeries.  It's better to analyze a changeable variable versus a fixed measurement.

edit: My document describing Arnett's analysis doesn't show an assessment of the mandibular plane at all.  But I've attached a screen snip of the Down's analysis from a comprehensive analysis I had done at CephX.com.  You'll see MP (GoGn) to FH mean is 28 degrees, OP to FH mean is 9.3 degrees, so the mean MP is 18.7 degrees steeper than the mean OP.  I have no idea how many subjects were studied for this analysis, nor do I know if the subjects were considered normal or ideal or what.  I believe it is an older study.

edit2: Wikipedia is showing a different mandibular plane angle for this analysis, see second attachment.  Not sure which is correct.

[katapult2]

You should be able to find the mean between OP and a fixed craniofacial line such as Frankfurt horizontal, then mean between MP and Frankfurt horizontal, then figure out the difference.  If using Arnett's analysis you'd use the True Vertical Line instead of a fixed line.  I can do some digging at home if you still can't find your answer.

The relationship between OP and MP is less meaningful because one or both could be off of the desired and can be modified with jaw surgery and/or other cosmetic surgeries.  It's better to analyze a changeable variable versus a fixed measurement.

edit: My document describing Arnett's analysis doesn't show an assessment of the mandibular plane at all.  But I've attached a screen snip of the Down's analysis from a comprehensive analysis I had done at CephX.com.  You'll see MP (GoGn) to FH mean is 28 degrees, OP to FH mean is 9.3 degrees, so the mean MP is 18.7 degrees steeper than the mean OP.  I have no idea how many subjects were studied for this analysis, nor do I know if the subjects were considered normal or ideal or what.  I believe it is an older study.

edit2: Wikipedia is showing a different mandibular plane angle for this analysis, see second attachment.  Not sure which is correct.

"You should be able to find the mean between OP and a fixed craniofacial line such as Frankfurt horizontal, then mean between MP and Frankfurt horizontal, then figure out the difference."

I thought of the same but I'm not sure if this is legit and whats up then with the SD...

"If using Arnett's analysis you'd use the True Vertical Line instead of a fixed line.  I can do some digging at home if you still can't find your answer."

How is the True Vertical Line defined and what is a fixed line?

"The relationship between OP and MP is less meaningful because one or both could be off of the desired and can be modified with jaw surgery and/or other cosmetic surgeries.  It's better to analyze a changeable variable versus a fixed measurement."

I do not really understand this. Can you explain that for me?


"edit: My document describing Arnett's analysis doesn't show an assessment of the mandibular plane at all.  But I've attached a screen snip of the Down's analysis from a comprehensive analysis I had done at CephX.com.  You'll see MP (GoGn) to FH mean is 28 degrees, OP to FH mean is 9.3 degrees, so the mean MP is 18.7 degrees steeper than the mean OP.  I have no idea how many subjects were studied for this analysis, nor do I know if the subjects were considered normal or ideal or what.  I believe it is an older study.

edit2: Wikipedia is showing a different mandibular plane angle for this analysis, see second attachment.  Not sure which is correct.
[/quote]"

These differences are huge! I think these two studies are not statistical significant or there were studied different ethnics, ages or gender. Often I see a Value with 25° +-5°.

Thank you for your help. I try to figure out if a ChinWing is sufficient or a double jaw surgery is necessary for my aesthetic problem...

[kavan]

"You should be able to find the mean between OP and a fixed craniofacial line such as Frankfurt horizontal, then mean between MP and Frankfurt horizontal, then figure out the difference."

I thought of the same but I'm not sure if this is legit and whats up then with the SD...

"If using Arnett's analysis you'd use the True Vertical Line instead of a fixed line.  I can do some digging at home if you still can't find your answer."

How is the True Vertical Line defined and what is a fixed line?

"The relationship between OP and MP is less meaningful because one or both could be off of the desired and can be modified with jaw surgery and/or other cosmetic surgeries.  It's better to analyze a changeable variable versus a fixed measurement."

I do not really understand this. Can you explain that for me?


"edit: My document describing Arnett's analysis doesn't show an assessment of the mandibular plane at all.  But I've attached a screen snip of the Down's analysis from a comprehensive analysis I had done at CephX.com.  You'll see MP (GoGn) to FH mean is 28 degrees, OP to FH mean is 9.3 degrees, so the mean MP is 18.7 degrees steeper than the mean OP.  I have no idea how many subjects were studied for this analysis, nor do I know if the subjects were considered normal or ideal or what.  I believe it is an older study.

edit2: Wikipedia is showing a different mandibular plane angle for this analysis, see second attachment.  Not sure which is correct.
"

These differences are huge! I think these two studies are not statistical significant or there were studied different ethnics, ages or gender. Often I see a Value with 25° +-5°.

Thank you for your help. I try to figure out if a ChinWing is sufficient or a double jaw surgery is necessary for my aesthetic problem...

Hi, I will just address your main question about the 'mean' of an angle between the OP and the MP.

I think you are probably talking about the lower part of the BASE PLANE ANGLE.

If you wanted to measure the angle between OP and MP, you just draw the OP and MP lines and take out your protractor. That is to say, you wouldn't first have to measure the OP and MP relative to other lines and subtract the difference. You just measure the angle between the OP and MP lines. That is the lower part of the BPA.

Likewise if you want to measure angle between the palatal plane (ANS-PNS) and the OP, you would draw a line through the points ANS-PNS and the line for the OP and take out your protractor.

Then you look up some norms. One norm I found was mean of the lower part of BPA is 14 degree. Upper part mean is about 11 degree.

I understand why it would be hard to find because you'd need to know it was part of the BPA in the Rákosi's analysis which is like one of the MANY types.