Comparison of extraction vs non-extraction decompensation for jaw surgery

[Heavyweight]

Abstract
OBJECTIVE:

To evaluate the effect of extraction and non-extraction decompensation to bimaxillary orthognathic surgery in skeletal class III malocclusion and the effect on postoperative.
METHODS:

Records of 36 completed surgical-orthodontic treatment skeletal class III malocclusion patients were obtained from School of Stomatology, China Medical University, 18 underwent maxillary premolar extraction, the other 18 underwent non-extraction. Their post-decompensation and postsurgery cephalometric radiographs were analyzed objectively, and their profile scissors-shadows in different groups were evaluated subjectively.
RESULTS:

The cephalometric index of post-presurgical orthodontics showed that there were significant deviations between the extraction and non-extraction groups including U1-SN, Overjet and Cm-Sn-UL values (P<0.05). During surgery, mandible was retruded (8.66 +/- 1.42) mm in extraction group compared with (6.21 +/- 3.06) mm in non-extraction group (P<0.05). After surgery, the extraction group achieved more normal ANB, U1-SN, NA-PA values (P>0.05).
CONCLUSION:

Maxillary premolar extraction can make incisor decompensation more complete so that mandible can be retruded to more ideal position and concave face can be successfully corrected.

http://www.ncbi.nlm.nih.gov/pubmed/22594229

The study was about class 3 cases, but I assume it applies to class 2 cases. I guess this kind of makes sense to me because if your jaws are so mismatched that you need jaw surgery, it's quite likely that one of your jaws has too many teeth in it. Avoiding extractions is obviously a great goal in and of itself and it does help decrease the time in braces pre-op, but the consequence is that the teeth are usually not in the ideal position within the bone, which prevents the surgeon from performing the best movements.

[Lazlo]

this makes sense, but it is irrelevant for people who have an overjet and a retruded mandible, right? most class III (underbite) patients have excess bone, but people with retruded mandibles and weak chins have less bone development in their jaws and thus need compensation. since my extractions, my jaw bones both upper and lower have slightly been absorbed at the extraction sites so that my jaws have gotten smaller, the opposite of what I want.  by no means am i certain about this, just hypothesizing that for people with overjets this may be less relevant?

[Heavyweight]

this makes sense, but it is irrelevant for people who have an overjet and a retruded mandible, right? most class III (underbite) patients have excess bone, but people with retruded mandibles and weak chins have less bone development in their jaws and thus need compensation. since my extractions, my jaw bones both upper and lower have slightly been absorbed at the extraction sites so that my jaws have gotten smaller, the opposite of what I want.  by no means am i certain about this, just hypothesizing that for people with overjets this may be less relevant?

I think it's the same for class 2 patients. Lower bicuspid extractions would increase the size of the overjet, allowing for a larger lower jaw advancement. If extractions aren't done, then the surgeon would need to either advance the lower jaw less, advance the upper jaw more, or use more counterclockwise rotation. All of these could result in a less than ideal aesthetic outcome.

You had four extractions, right? That's very different from having two extractions because it doesn't exaggerate the magnitude of the malocclusion.

[Lazlo]

I think it's the same for class 2 patients. Lower bicuspid extractions would increase the size of the overjet, allowing for a larger lower jaw advancement. If extractions aren't done, then the surgeon would need to either advance the lower jaw less, advance the upper jaw more, or use more counterclockwise rotation. All of these could result in a less than ideal aesthetic outcome.

You had four extractions, right? That's very different from having two extractions because it doesn't exaggerate the magnitude of the malocclusion.

Yeah I had all four bicuspids extracted. ...I'll look forward to see what Dr. Arnett thinks of what my ortho/surgeon here have planned thus far. I hope he's not like "those f**king morons! what the hell do they think they're doing!"