Author Topic: Why are surgeons flattening the curve of Spee?  (Read 3597 times)

molestrip

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Why are surgeons flattening the curve of Spee?
« on: April 22, 2015, 03:25:22 PM »
All my treatment plans include leveling the plane of occlusion, as described here, via a 3-piece LeFort. At first I attributed this to closing my open bite but then I noticed on my casts that my open bite closes nearly perfectly without it. I measure the curve to be 3mm so if this page is any guide then my occlusion would be grossly normal. In fact, it would become abnormal after surgery! At least various sources I've read suggest that a mild curve of Spee is both good for mastication and the TMJ. I could even keep my wisdom teeth, were they not removed for the BSSO. Yet, many orthodontists and surgeons try to flatten the curve. Does anyone know the reason for this? A 3-piece Lefort is a far riskier procedure, both in terms of necrosis from additional loss of bone blood flow and relapse. In fact, it's among the least stable types of movements according to the hierarchy of stability.

Only one surgeon I corresponded with, out of five, has not recommended it. I haven't discussed it with him yet but in that case, the arch could simply be widened orthodontically or via a SARME in a separate procedure, avoiding most of the risk and morbidity of a 3-piece LeFort.

terry947

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Re: Why are surgeons flattening the curve of Spee?
« Reply #1 on: April 22, 2015, 05:34:52 PM »
The surgeon also recommended this to me during my consultation. TBH, i dont want to do a 3 piece lefort. Thats why I'm doing to try and close the bite with braces or whatever I figure out, and then get a standard lf1 for advancement. The less cuts the better, and probably more stable. I've already noticed my bite closing. My opinion, is to avoid the 3 piece.

PloskoPlus

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Re: Why are surgeons flattening the curve of Spee?
« Reply #2 on: April 22, 2015, 06:56:31 PM »
It's interesting that 3 piece is default for a&g.  AFAIK, they don't do sapre.

LoveofScotch

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Re: Why are surgeons flattening the curve of Spee?
« Reply #3 on: April 22, 2015, 08:09:37 PM »
I've seen a handful of people and only one said a 3-piece Le Fort may be needed. No one proposed SARPE.

A multisegment Le Fort scares me. A lot. Are my fears logical? I'm not really sure. I'm actually not that worried about stability, but I'm concerned about the potential consequences for my teeth.

I think it's probably worth avoiding if possible, but I don't think I would pick a less optimal surgical plan strictly to avoid having my upper jaw cut into multiple chunks.

terry947

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Re: Why are surgeons flattening the curve of Spee?
« Reply #4 on: April 22, 2015, 11:07:43 PM »

molestrip

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Re: Why are surgeons flattening the curve of Spee?
« Reply #5 on: April 23, 2015, 02:09:52 PM »
I'm worried about stability. Those face muscles eventually take their toll, which is where I'm at. That's a cool appliance but at the end of the day, they're just moving teeth in the jaw. I can't avoid surgery but it'd be nice to know that if there's relapse, it can be controlled orthodontically. At least I'd only be looking at revision upper jaw surgery but it would really suck to go through it again AND have to have the multi-segment osteotomy. It's risky enough the first time but with scar tissue from the first surgery? Same probably goes for revision are multi-segment otseotomy. That being said, I've spoken to a number of people who've had them and it doesn't seem to be an issue in practice when done by competent surgeons except for one girl on realself (her surgeon decided to a 4-piece interop and she has EDS). Some amount of relapse may also just be tolerable, minorly unaesthetic and unfunctional in other words isn't necessarily a problem.

Some other cool quotes I picked up from an oral surgeon textbook:

One surgeon (ahem, the author) notes a Bolton discrepancy on my upper lateral incisors. Here's what he writes:
"A tooth size discrepancy (TSD) causes incompatibility of dental alignment and may occur in the anterior teeth, premolars, and molar regions. Approximately 40% of patients with dentofacial deformities will have an anterior TSD affecting the anterior six teeth of the maxillary and mandibular arches (the mandiblar arch is commonly too large compared with the maxillary arch), usually owing to small maxillary lateral incisors. In such cases, proper tooth alignment, with all spaces closed, often precludes establishment of a good class I cuspid-molar relationship with treatment".

To be fair, I forgot my models so he couldn't evaluate them. I feel that my lateral incisors are small, though, a few have told me that. I don't see widths here but certainly in length, owing to trauma (blunt, acid, bruxism). I guess I need them crowned? Just because someone wrote it in a textbook, doesn't make it right of course. Otherwise, we would all just go to the textbook authors and they would all write textbooks lol. Those guys tend to be better though I think.

The normal values for arch widths are shown here. I took some measurements, here's what I got cuspid to 2nd molar. Maxillary: 34mm, 37mm, 42mm, 45mm, 54mm. Mandibular: 27mm, 34mm, 33mm, 43mm, 50mm. I'm male so both are actually within the realm of normal, they're just not in agreement at which end of normal they want to be! Given that much, surgical widening of the planes seems inadvisable, no? I had braces as a kid. I'd have to check my CBCT but last time I looked it seemed like my teeth were roughly decompensated already.

Continuing on, discussion on the curve of spee:
"This evaluates the vertical position of the anterior teeth compared with the posterior teeth. This assessment can be determined by placing the occlusion of the maxillary dental model on a flat plane; the incisors should be about 1mm above the flat plane. Placing the occlusion of the mandibular dental model on a flat plane should see the mandibular incisors elevated 1mm above the midbuccal teeth. A significant accentuated curve of Spee in the maxilla is usually associated with an anterior open bite and a reverse curve associated with an anterior deep bite. An accentuated curve of Spee in the mandible is commonly associated with an anterior deep bite and a reverse curve associated with an open bite.".

Hard to say here because of the wear to my teeth. But eyeballing it, on the maxilla after restorations my incisors should be level with an error +/- 1mm. The same is true for the mandible. It only appears to have an accentuated curve of Spee because of damage to the teeth. See, this is what is confusing me, if you look at my panoramic x-ray and to some extent the CBCT, you can see that the maxilla is nearly perfectly level (ignoring the tooth line). Comparing against random Google searches reveals the same. This surgeon only recommended a 2mm downgraft to the anterior. My mandible looks curved but we know that's due to my long face (19deg reportedly, I didn't check). I'd guess that'd look straight post correction. These measurements were taken without the wisdom teeth, which are "malaligned" and certainly appear so on the models otherwise the curve looks bigger at 3-4mm. But again, they have the most wear being in the back with an anterior bite which makes it look bigger. This is significant because the chapter also notes that a segmental osteotomy is indicated at >2mm for stability.

There's a discussion on macroglossia here. My tongue is indeed too large for my mouth, I've been told it's moderate-large. A few of these items apply to me, not all.

Discussion of open bite pathology on this page.

"Most anterior open bite deformities that develop in the teenage years or later are commonly related to TMJ pathology. However, if macroglossia is present then instability of the orthodontics ... with a tendency for the open bite to return. Pseudomacroglossiais a condition in which the tongue may be normal in size, but it appears large relative to its anatomic interrelationships." And some comments about stabilizing joints, which the author is noted for (and I don't necessarily disagree with either). However, my joints have been imaged and reviewed by several people now. The joints and soft tissue are excellent. My tongue is fine. So why the anterior open bite?

On other pages I noted that anterior open bites are associated with very weak chins and with a reverse curve of Spee. Neither of these applies to me. Again, all this discussion and my case isn't really matching up well.

Why am I bringing this up in excruciating detail? Because you get 3 hours with the surgeon (if you're lucky) and it took me nearly that look just to write this up lol. We have cafeteria style healthcare in this country. When you walk in the door with anterior open bite, the surgeon has matched you against a pattern of patients that they see and provided a surgical plan that matches the pattern. I'm not a clear match and so I don't have a clear solution. My best guess is that wear a mouth guard from 12+ and getting late stage growth, the mouth guard simply opened up my bite. Due to the mouth breathing and tongue thrusting from sleep apnea, I got a bit of vertical growth on the mandible and downward rotation of the maxilla. The mandible didn't follow because there was little occlusion at this point and the bite opened up.

I'd love your thoughts. Here's some of my imaging, let me know if I'm off base here.
« Last Edit: May 05, 2015, 11:17:32 AM by molestrip »

molestrip

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Re: Why are surgeons flattening the curve of Spee?
« Reply #6 on: May 05, 2015, 12:34:46 PM »
There's a nice article on PubMed from 2012 titled Significance of the curve of Spee that may be interesting in this context.