Author Topic: Bimax or just BSSO? Conflicting opinions are making decision difficult  (Read 8939 times)

haven

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #15 on: March 19, 2018, 06:20:20 PM »
FWIW I had a very similar starting position as you (flat occlusal plane, severely proclined lower jaw incisors, double chin). During the "set up" phase of my treatment, upper jaw (in addition to the unavoidable lower jaw extractions in both our cases) extractions were discussed but I managed to get away without them - partly because of a 2 piece lefort osteotomy which widened my upper arch bit which in turn increased the space available for the teeth.

A posterior downgraft of the maxilla was briefly considered by my surgeon but I ended up getting no rotation and my skeletal base was successfully normalized without rotation (ANB angle is 0°, SNA and SNB both 87°) with a linear advancement of both jaws. My result has been generally received positively.

I have come to realize, however, that most if not all of the aesthetic improvement came from the lower jaw advancement (I didn't get a genioplasty). Therefore I think that in your case (a low angle patient) lower jaw premolar extractions, BSSO and a genioplasty will give the improvement you seek with a much easier surgery over all. I think that, had I do it all over again, that I would pick this route for my case.
I think that had I been asked to remove an additional two premolars in the upper jaw, I would not have gone through with jaw surgery (my back up plan was a chin wing surgery instead).

The difference between this and a proper CCW rotation surgery is maybe 3-4mm of additional lower jaw advancement (if that). I highly doubt that this would make a material difference, both in terms of sleep apnea and looks/attractiveness. Would anyone look materially different with a lower jaw that's 3mm more forward? I doubt it.

One last word of caution: Your bite right now seems pretty good, despite the aggressive dental compensation. Mine was the same way, maybe a tad worse than yours. You should fully expect for the post op occlusion to be worse after extractions, especially if you opt to not extract in the upper jaw (which I would recommend).

So you think he should leave the upper jaw alone but still extract teeth up top? Would the molars be shifted forward to close the spaces on the upper jaw and the lower teeth would be moved back to create a larger overjet to then move the mandible forward? Sorry to hijack your thread, bro, haha.

PloskoPlus

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #16 on: March 19, 2018, 07:09:15 PM »
No he meant extract lower only. Advance lower only.

haven

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #17 on: March 20, 2018, 07:48:14 AM »
No he meant extract lower only. Advance lower only.

Just extending the mandible without a genioplasty after extractions means they get to move the jaw based on the space created by the extractions right? So if there was a 5mm gap created from extractions, after moving the lower teeth back the overjet created is more or less equal to the space created from the extracted teeth?

Totally not an expert in this.

Sanj87

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #18 on: March 20, 2018, 04:37:40 PM »
Im curious how are both his jaws underdeveloped if his sna is way above the norm?

kavan

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #19 on: March 20, 2018, 06:29:06 PM »
Im curious how are both his jaws underdeveloped if his sna is way above the norm?

Because angle relationships are relative measures.
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emanresu

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #20 on: March 20, 2018, 11:21:34 PM »
Because angle relationships are relative measures.

Sorry if I misunderstood, but are you basically saying the other points (S and N) are “throwing off” A? And while we could typically look at A to determine if the upper jaw was retruded and in a deviant position, since S and/or N are also deviant (perhaps N being too low and/or underprojected), SNA can’t actually be relied on as a metric for determining retrusion in this case?

Perhaps this is just a quirk of my morphology, or perhaps it indicates something more dreadful such as an overall lack of bone development, jaw and all.

kavan

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #21 on: March 21, 2018, 08:48:51 AM »
Sorry if I misunderstood, but are you basically saying the other points (S and N) are “throwing off” A? And while we could typically look at A to determine if the upper jaw was retruded and in a deviant position, since S and/or N are also deviant (perhaps N being too low and/or underprojected), SNA can’t actually be relied on as a metric for determining retrusion in this case?

Perhaps this is just a quirk of my morphology, or perhaps it indicates something more dreadful such as an overall lack of bone development, jaw and all.

QUIZ for you.

What very simple 4th grade concept in GEOMETRY would you need to be familiar with as to the very basic understanding of what could be meant by the statement: 'Angle Relationships are Relative Measures' ?
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emanresu

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #22 on: March 24, 2018, 12:12:30 PM »
QUIZ for you.

What very simple 4th grade concept in GEOMETRY would you need to be familiar with as to the very basic understanding of what could be meant by the statement: 'Angle Relationships are Relative Measures' ?

Are you referring to ratios? But what angle is SNA being compared with? Or are you just more generally saying “it’s all relative”, as in, everything has to be considered with everything else, and an individual angle isn’t always perfectly indicative of appropriate/possible treatment? Seems like a pretty reasonable approach, but the high SNA just seemed odd to me.

I’ve spent the last few days trying to research the topic, and I read a few interesting things in Facial Aesthetics: Concepts and Clinical Diagnosis:

“In patients with dentofacial and/or craniofacial deformities, there is always the possibility of deviations from the norm in the inclination (or sagittal cant) of the cranial base, as well as in the position of the jaws. Therefore, abnormal cephalometric measurements relating to the jaws to the cranial base may be due to deviations in the cranial base (the position of sella, nasion or both), rather than in the position of the maxilla or mandible.”

The excerpt above seems like pretty fundamental stuff, a.k.a. basic geometry, but it also explicitly confirms what I mentioned in my previous post about how deviations in the positon of the cranial base (nasion in particular?) seemed to be causing the deceptive SNA angle. Unfortunately, I haven’t yet found anything which states how severe of an issue having a deviant cranial base is, as in, if these deviations are regarded as a fairly typical thing to work around, or a very unfortunate hurdle (which in my case would result in bimax making the maxilla appear too forward regardless of CCW or conservativeness). If the latter, it would perhaps be another point in favor of a lone BSSO.

I also found a slightly more interesting excerpt: “If nasion is more forward in position, the SNA is decreased, and vice versa. Therefore, in these circumstances the angle ANB may be adjusted, to some extent, as follows . . . For every 1° that it [SNA] is above the average, subtract 0.5° from the angle ANB.”

This is very curious to me, as I understand that SNA – SNB = ANB, so the greater SNA is, the greater ANB also is, but then the adjustor outlined above also actively aims to reduce the difference caused by the higher SNA. For whatever reason this is mainly done, it also seems that it would have the additional benefit of allowing you to advance the jaws (well, A and B; not the teeth) more forward than you’d be able to otherwise as long as your SNA is greater than normal. Exactly how much further movement this adjustor allows, I’m not yet sure, but it’s still somewhat comforting to know that a high SNA can be accommodated to some extent.

notrain

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #23 on: March 24, 2018, 02:12:06 PM »
Thanks for the follow-up! That’s really interesting about the 2-piece Lefort. No one has suggested that to me yet, so I’m not sure if it’s applicable in my case, but I’ll definitely be keeping it in mind. I actually asked Gunson about SARPE + MSDO and he said it’d make my chin too wide, but maybe that was only in reference to the MSDO.
You don't need SARPE, you may need a cone shaped split of the maxilla to widen the space between the left and right upper jaw molars. That is what I got, 4mm wider upper jaw in the back, no widening in the front.

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It’s good to hear from someone else that a BSSO isn’t a bad idea, because it’s definitely still on the table for me, and I agree that 3-4 mm seems like a very fair compromise to consider.
Single (lower) jaw surgery is a great idea for low angle patients like us, as most of the movement gets translated forward and not downwards, as would be the case for steep/high angle patients.
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My occlusion is actually great as far as my bite goes, so it’s disappointing to hear surgery may make it worse. Is this due to the BSSO making the lower teeth no longer line up with their “corresponding” upper ones? If so, depending on how severe the malocclusion would become, perhaps bimax is worthwhile for this reason alone?
It has in part to do with the teeth no longer meshing with their natural counterparts. The unavoidable problem however occurs because your lower incisors are now excessively proclined which makes 1st premolar extractions mandatory in order to place them in a normal upright (90°) position. This however will cause the incisors to lengthen as the ortho uprights them which will in turn give you a huge bilateral open bite immediately after surgery (doesn't matter if you get bimax, bsso, ccw or no ccw). This open bite has to be closed with post op orthodontics via means of extrusion of the lower jaw molars and premolars. This extrusion usually relapses partly after the braces are removed. My bite was actually very good right after ortho and after 12 months the extrusion relapsed by about 1mm. Not a huge deal, but my bite before surgery was better (my looks were way worse).
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Also, not to push my luck, but could you perhaps PM me the name of the surgeon you chose? With the similarities of our cases, I would love to hear his opinion about mine, as from your description he seems like he’s comfortable suggesting the complex maneuvers which other surgeons would avoid.
I had surgery by a completely unkown German surgeon. I'll gladly PM you the name if you want, but seeing as you are from Canada, I'd say it is pointless. A linear BSSO is a simple surgery, even if it is a large advancement. Almost any jaw surgeon should be able to execute this surgery properly for you. You need specialists if you are a high angle patient who needs a large rotational advancement, but you are not a candidate for this (be glad, it is expensive).
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Thanks again, I really can’t express how much all this help means to me.
No problem, that's what we're all here for.

notrain

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #24 on: March 24, 2018, 02:30:00 PM »
Just extending the mandible without a genioplasty after extractions means they get to move the jaw based on the space created by the extractions right? So if there was a 5mm gap created from extractions, after moving the lower teeth back the overjet created is more or less equal to the space created from the extracted teeth?

Totally not an expert in this.
It's a bit more complicated. In low angle patients, the lower jaw usually gets clockwise rotation as well as a large sagittal advancement. So the osteotomy itself moves the jaw more than what the linear overjet suggests. In low angle patients, extractions combined with uprighting of usually severely proclined incisors will give more than 1cm linear overjet. Including the clockwise rotational component, you're looking at 12-15mm BSSOs providing the ortho did a good job decompensating.

Sanj87

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #25 on: March 24, 2018, 02:46:06 PM »
From what im reading sna and snb angles are useless

kavan

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #26 on: March 24, 2018, 10:35:54 PM »
Well, I see neither of you answered the simple geometry concept relating to ANGLES.

You took the last few days researching this? The question was asking for a simple geometric concept. People lacking simple geometry concepts are going to have a real hard time with a lot of what's going on with max fax and will be confusing themselves and over complicating things.


HINT:

SNA, SNB are ANGLES. Angles alone don't tell you anything about the SIZE of something.

If I have 2 equilateral triangles, the fact that their angles are the same tells me NOTHING about the distance of the lines making up the triangle and hence the SIZE of the triangles. One triangle can be a different size than the other. One can be BIGGER than the other.

So, Sanjay's statement of: ["Im curious how are both his jaws underdeveloped if his sna is way above the norm?"] reveals he doesn't understand why an angle does not tell you anything about the SIZE of something. He might as well be curious as to how 2 equilateral triangles, similar in shape are different sizes if they both have the same angles.

Basically, someone with grammer school geometry would have known angle relationships alone don't tell you anything about the SIZE of something and would not have asked that question.

BOTH jaws CAN be undeveloped whether or not SNA exceeds the norm because angles don't tell you about the SIZE of something.
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emanresu

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #27 on: March 25, 2018, 08:40:32 PM »
You don't need SARPE, you may need a cone shaped split of the maxilla to widen the space between the left and right upper jaw molars. That is what I got, 4mm wider upper jaw in the back, no widening in the front.
This really does intrigue me. I’m not sure if it’d be applicable to my case though, as my bite is perfect right now so I think I’d need to widen the mandible too so the dental arches would match. I’ll mention it to the next surgeon I speak to though!

It has in part to do with the teeth no longer meshing with their natural counterparts. The unavoidable problem however occurs because your lower incisors are now excessively proclined which makes 1st premolar extractions mandatory in order to place them in a normal upright (90°) position. This however will cause the incisors to lengthen as the ortho uprights them which will in turn give you a huge bilateral open bite immediately after surgery (doesn't matter if you get bimax, bsso, ccw or no ccw). This open bite has to be closed with post op orthodontics via means of extrusion of the lower jaw molars and premolars. This extrusion usually relapses partly after the braces are removed. My bite was actually very good right after ortho and after 12 months the extrusion relapsed by about 1mm. Not a huge deal, but my bite before surgery was better (my looks were way worse).
Ah, that completely makes sense about the teeth rotating, thanks for clarifying. When you point it out, it almost seems obvious, but despite knowing this is a game of millimeters I still sometimes find myself failing to recognize how each miniscule movement and rotation can have such a profound effect like that. As I was writing this response, I just remembered one of the most interesting things Gunson said to me, which is actually relevant to this. He said that the teeth are supposed to mimic the level of the jaw, but then pointed out that my teeth don’t; my flat occlusal plane doesn’t match my steep mandibular plane, with my lower front incisors being higher than they should be (either from my previous orthodontic work pushing them up to artificially close my open bite, or just due to my mentalis muscle strain pushing them up) and he said I should talk to my current orthodontist about the possibility of pushing these teeth back down into the mandible. So I may be able to do that instead of extruding the lower molars and premolars.

I had surgery by a completely unkown German surgeon. I'll gladly PM you the name if you want, but seeing as you are from Canada, I'd say it is pointless. A linear BSSO is a simple surgery, even if it is a large advancement. Almost any jaw surgeon should be able to execute this surgery properly for you. You need specialists if you are a high angle patient who needs a large rotational advancement, but you are not a candidate for this (be glad, it is expensive).No problem, that's what we're all here for.
Interesting, I thought you may’ve gone to a “big-name” surgeon with a more complex plan like that. But yes, in that case I think you are right about it not being necessary, as I still have several more surgeons to talk to on this continent! (Well, and Alfaro as an exception.)

No problem, that's what we're all here for.
Well I’m immensely thankful for your generosity, as well as the generosity of everyone else here.

Well, I see neither of you answered the simple geometry concept relating to ANGLES.

You took the last few days researching this? The question was asking for a simple geometric concept. People lacking simple geometry concepts are going to have a real hard time with a lot of what's going on with max fax and will be confusing themselves and over complicating things.


HINT:

SNA, SNB are ANGLES. Angles alone don't tell you anything about the SIZE of something.

If I have 2 equilateral triangles, the fact that their angles are the same tells me NOTHING about the distance of the lines making up the triangle and hence the SIZE of the triangles. One triangle can be a different size than the other. One can be BIGGER than the other.

So, Sanjay's statement of: ["Im curious how are both his jaws underdeveloped if his sna is way above the norm?"] reveals he doesn't understand why an angle does not tell you anything about the SIZE of something. He might as well be curious as to how 2 equilateral triangles, similar in shape are different sizes if they both have the same angles.

Basically, someone with grammer school geometry would have known angle relationships alone don't tell you anything about the SIZE of something and would not have asked that question.

BOTH jaws CAN be undeveloped whether or not SNA exceeds the norm because angles don't tell you about the SIZE of something.
I won’t speak for Sanj87, but my curiosity and confusion about SNA doesn’t stem from a misunderstanding of basic geometry, but what seems to be a fundamental misunderstanding of the application of cephalometric values, or at least SNA in particular. I originally thought SNA directly indicated maxillary protrusion/retrusion, as some of the (admittedly introductory) resources I read seemed to state as such without elaborating further (“>85° - protrusive or prognathic maxilla, <79° - deficient or retrognathic maxilla”). I know the difference between angle and size, but my confusion led me to assume that perhaps maxfac’s had some method of converting the SNA angle (and I guess every other individual angle and value for that matter) into some directly applicable measurement for determining size of movement. I basically thought that each of these values (SNA, SNB, etc.) could, with the use of some other hypothetical function, very precisely indicated how much something should be moved.

When Sanj87 asked, “How are the jaws underdeveloped if SNA is way above the norm?” due to my misunderstanding I translated it as, “How are the jaws underdeveloped if the clinical measurement which directly determines jaw development says otherwise?”

At the time, this seemed like a good question, as for a total layman, when you see that you possess a value that deviates from the norm, it can seem like a cause for alarm. Really I was just trying to determine if an abnormally high SNA is something to be concerned about.

Perhaps, as you say, I’m overcomplicating things, and these cephalometric values hold less importance/determinacy than I originally thought, and they are simply used as an approximate assessment and not for directly applicable use, or perhaps they really are serious warning signs for aesthetic repercussions. I'll keep researching into this.

Anyway, I’m sorry my misunderstanding got in the way of meaningful discussion. All I can do is keep trying to learn, and I will do my best to continue doing so.

kavan

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #28 on: March 25, 2018, 09:28:03 PM »

I won’t speak for Sanj87, but my curiosity and confusion about SNA doesn’t stem from a misunderstanding of basic geometry, but what seems to be a fundamental misunderstanding of the application of cephalometric values, or at least SNA in particular. I originally thought SNA directly indicated maxillary protrusion/retrusion, as some of the (admittedly introductory) resources I read seemed to state as such without elaborating further (“>85° - protrusive or prognathic maxilla, <79° - deficient or retrognathic maxilla”). I know the difference between angle and size, but my confusion led me to assume that perhaps maxfac’s had some method of converting the SNA angle (and I guess every other individual angle and value for that matter) into some directly applicable measurement for determining size of movement. I basically thought that each of these values (SNA, SNB, etc.) could, with the use of some other hypothetical function, very precisely indicated how much something should be moved.

When Sanj87 asked, “How are the jaws underdeveloped if SNA is way above the norm?” due to my misunderstanding I translated it as, “How are the jaws underdeveloped if the clinical measurement which directly determines jaw development says otherwise?”

At the time, this seemed like a good question, as for a total layman, when you see that you possess a value that deviates from the norm, it can seem like a cause for alarm. Really I was just trying to determine if an abnormally high SNA is something to be concerned about.

Perhaps, as you say, I’m overcomplicating things, and these cephalometric values hold less importance/determinacy than I originally thought, and they are simply used as an approximate assessment and not for directly applicable use, or perhaps they really are serious warning signs for aesthetic repercussions. I'll keep researching into this.

Anyway, I’m sorry my misunderstanding got in the way of meaningful discussion. All I can do is keep trying to learn, and I will do my best to continue doing so.

It's just that you spring boarded from his (clueless) question by introducing complexities that had nothing to do with the basic response to his question. Not to say that you don't have a complex face case which I could help explain but there is a sense of futility on my part to give an explanation if I've gotta wonder if I've gotta go over basic geometry to do it. Not saying you wouldn't understand.  But I was not up to clearing confusion that looked like it arose from HIS question and my basic response to it.

SNA values when high are indicative of RELATIVE protrusion (upper jaw). But BOTH jaws can be retrusive and really retrusive and/or under developed which is your case. Your case is also complicated because you have bi-max protrusion along with the double jaw retrusion.
Yes. Maxfax's have another way of looking at double jaw retrusion and they can do it without 'converting any angles' into something else. They drop a vertical from a selected area near the forehead and take a look at whether or not the jaws are too far behind that line. Just trying to keep it simple here.

ETA: To clarify he had both double jaw retrusion with bi max protrusion.
« Last Edit: March 26, 2018, 07:42:34 PM by kavan »
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notrain

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Re: Bimax or just BSSO? Conflicting opinions are making decision difficult
« Reply #29 on: March 26, 2018, 04:19:14 AM »
This really does intrigue me. I’m not sure if it’d be applicable to my case though, as my bite is perfect right now so I think I’d need to widen the mandible too so the dental arches would match. I’ll mention it to the next surgeon I speak to though!


The mandible is wider in the back than in the front for everybody. As the surgeon advances the mandible relative to the maxilla, a wider part of the mandible will end up opposite of a narrower part of the maxilla (assuming your mandible and maxilla match up width wise where they are now). You will either need dental compensation (i.e. tilting upper jaw teeth towards your cheek) to give width or an osteotomy. An osteotomy is usually preferable to dental compensation.