Module 5 case 1 prompt 2

[Chad Carter (Course Director)]

Christopher,

1) For evaluating a posterior transverse discrepancy when there is also a severe AP discrepancy we need to take both planes into account (it’s also discussed a few other threads about this case). So I start (like you said) by looking for posterior crossbites or wide buccal corridors. I agree with you that those items are not present.

<u style=”font-style: italic;”>However, this is where the AP situation comes in to play. A great phrase of one of my mentors (Dr. Frans Currier, OU) is that “The mandible is the diagnostic arch!” So how does that play out here? Well, we imagine in our minds uprighting in a 19×25 SS (or your wire of choice) and then advancing into a Class I relationship. In this case once the patient is advanced into a Class I relationship he will be at least edge to edge in the posterior if not bilateral posterior crossbite. Side Note: This is much easier to simulate when you have models actually in your hand. So this is what we then call an absolute transverse discrepancy because when put in correct skeletal AP and dental AP relationship their will be crossbites. On the other hand a relative transverse discrepancy is frequently evident with severe maxillary AP deficiency – the maxilla is deficient and you see posterior crossbites but if you advance them to Class I skeletal/dental with a LeFort all of a sudden there are no crossbites.

2) For the face height the measurements are linear and not angular. So it does not reference FMA or SN-MP. Instead, Lower Anterior Face Height is ANS to Menton (Upper is Nasion to ANS). Posterior Face Height is Sella to Gonion. This prompt’s reply then is identifying that there is a decreased distance between ANS to Menton.

Do both of those items make better sense now?

Thanks!

Carter

[Christopher Fanelli]

Yes the transverse discrepancy certainly makes sense to me.

For anterior facial height, I don;t seem to remember seeing the numbers listed in any of the ceph numbers in any of the cases. Did I miss that? Or are we just looking at it and taking our best guess since the numbers are not on the ABO analysis?

Thanks!

[Chad Carter (Course Director)]

You are correct, sir. The facial height measurements are not provided measurements on the ABO analysis. We just eyeball it.

Thanks!

Carter

[BRIAN BROADWELL]

I find it helpful to use your scratch paper to place two marks that would represent the distance from mid-browline to subnasale and then compare that measurement to the distance from subnasale to base of chin (is ST gnathion a thing?).

[Christopher Fanelli]

Thanks Brian!!