When to do Corticotomy

[DMcGann]

For those of you that attended the 2010 update seminar (if you did NOT, do NOT make any changes in your thinking), you learned that we now have ways to overcome cortical bone and to better determine in advance of treatment HOW much skeletal resistance there is in any given case.  Each bracket/archwire torque has a different skeletal resistance, and this is part of the incisor torque diagnosis.  Range of bracket torque templates PLUS the treatment decision VTO are used INSTEAD OF ANB AND WITS to determine which cases have skeletal resistance. Some cases with ANB skeletal class I need corticotomy!!!  surprise. Depends on palatal anatomy (or lower lingual), NOT A point.
   Here is the system as of this moment in time to determine which cases [still] need a corticotomy.   
I have been considering the ways to distinguish those cases that need corticotomy and those that do not after the discovery of low force changes to the cortical bone.  Since the california update, I have tried to quantify the severity of the bone resistance....and after discarding a measurement of bone needed to be resorbed, I simply made a general classification system. 
   This is a PRELIMINARY SYSTEM to decide how to distinguish the cases....and may be modified over time. Also, keep in mind that more molar anchorage is needed when the cortical bone is resorbed, to the point that skeletal anchorage is needed to match the 'dots' in model measuring anchorage planning.

 
1. Mild skeletal resistance (based on range of bracket torque template). some cortical bone must be resorbed to get the predicted tooth to the predicted position at the retraction limit inclination of the selected bracket and archwire combination.
  [ Attachment: You are not allowed to view attachments ]
 
2. Moderate skeletal resistance: A portion of the root is overlayed on the cortical bone anatomy, but the apex of the tooth is inside the medullary space.
  [ Attachment: You are not allowed to view attachments ] [ Attachment: You are not allowed to view attachments ]
 
3. Severe skeletal resistance: with range of bracket torque (reference the occlusal plane and incisal edge of final incisor position) of selected bracket on selected treatment decision vto, the root apex is over the cortical bone anatomy.
  [ Attachment: You are not allowed to view attachments ] [ Attachment: You are not allowed to view attachments ]
 
4. Extreme skeletal resistance. with range of bracket torque of selected bracket on selected VTO, the root apex is outside the cortical bone anatomy, either upper or lower.

I don’t have my scanner handy, but if you take the lower 19x25 La diagram in severe skeletal anchorage and apply Li torque, the root will definitely be outside the cortical bone!!
 
One of the concepts that I may not yet have developed as recently as the California update was the concept that every different bracket torque has a different skeletal resistance.  I think I told you this?  When retracting incisors upper or lower, the more lingual root torque in the bracket, the more skeletal resistance. So SLi has the most, La has the least. Based on the retraction limit. you can avoid corticotomy by accepting a more retroclined incisor (detorqued), OR by not retracting as far (less molar anchorage).
 
Cases in need of corticotomy are the ones with severe or extreme skeletal resistance.  Mild to moderate should be able to be treated with the principles we discussed at 2010 update....if they attended the course!!

[bleenz]

One of the ways I have been trying to predict skeletal resistance and whether to do a corticotomy or not is to do a skeletal resistance vto.This is done taking your final selected model analysis and doing a normal vto. Take a copy of the start ceph again and select the vto again and before saving it click elsewhere,this will have the effect of losing the ceph,now copy  the copied ceph again and this will produce a combination vto.Now copy the combination cep with screenhunter and  then import this into Photoshop and apply the torque templates to this ,use version 2 torque templates where the upper and lower torques have been separated and position the templates so that the occulsal plane is in its correct position and place the incisor edge of the specifc torque on the incisor edge of the final incisor position the vtoi and this will give you the prediction according to specific torque on whether to do a corticotmy or not,see if the root is outside the palatal cortical bone.I bimax cases it is acceptable to finished with a detorqed upper incisor upper 1 to Sn in the range of 72' as the bimax protrusion will make the detorqued upper incisor acceptable to terms of esthetics however in a non bimax case this range to 72' is not acceptable where a corticotomy or even orthognathic surgery intervention ma be as better alternative

[DMcGann]

I am not computer wizard enough to follow Bernard's description (he is a wizard and a great thinker), so I will just have to wait until the Australian update seminar to get a demo (you will be there Bernard?).  Skeletal resistance vto sounds interesting and valuable. 

   Please THROW AWAY your version 2 torque template!!!  It took me 3 years to get the torque templates correct and ONLY version 4 is considered by me as being accurate.  There were errors in version 2, that did not work clinically, the reason to go to version 3 and eventually version 4 which works perfectly.
   Torque templates and incisor inclination according to range of bracket torque have NOTHING to do with angles of upper incisor to SN line.
   

[bliaodds]

Don:

Thanks for making this post. I print it out and kept it as part of my study.

This may seem a little redundant, but I was at the 2010 update, and I spoke with one of the instructor on the use of Range of Torque template on other cases.
Can we use these templates on ALL types of cases, including Class III cases? Most of the examples shown in class were extraction cases or retraction cases. Can you help me understand the use of template when it comes to Class III cases? or cases that involves incisor advancement?

My understanding of cases that involves advancement would mean that we use the advancing limites rather then the retraction limit, is that correct?

You may have gone over it, but I had to leave early to catch a flight, sorry...

When I look at a case now, I first select the VTO that I want to treat the patient with, then I looked at the final incisor position and after determining wether or not I want to retract, advance or stay the same, that's when I start going through the torque template, is that how you would recommend the template being use?

Any input is welcomed!! Thanks

Bliao

[DMcGann]

YOU have it right.  With an advancing incisor (predicted on your vto), the advancing limit is what you look at.  La 19x25 upper and SLa 19x25 lower have the Roth ideal inclination at the advancing limit.  This is done for EACH ARCH separately. 
     You also must consider the mechanics...so if you are applying class II elastics or coils to an upper incisor, you may choose Li torque even though the incisor may be moving "forward" on the vto.  Think about what can go wrong, what you don't want to happen, and this will then give you a hint on what is the best torque.  This is where you might get Li/SLa for a class II elastic case...prevent detorquing the upper incisor, prevent too much tipping of the lower incisor.
     Torque templates are applied to ALL CASES...to help you make the best incisor torque diagnosis. Otherwise guessing, which is not usually very effective (I am wrong about 80% of guesses)
     Class III cases, USUALLY La upper to prevent too much proclination...advancing limit (but sometimes we use Li retraction limit to push the upper incisor more forward) and La or Roth lower to allow some retroclination of the lower incisor to the retraction limit. Which one depends on the individual patient treatment decision vto.
     The non-extraction cases were at the end of the 2010 update seminar.

[bliaodds]

Don:

Thanks for the clarification.....
I think this allows us to start thinking more about our cases, rather then just follow a
general formula...This really puts the control in the doc's hand, rather then some lab
technician...

Brian

[bleenz]

Dear Don,
There is a bit of misunderstanding here,what I have done is used the latest torque templates and imported them into photoshop.I have split them into upper  and lower incisor torques separately so it is easier to see the combination of different torques.Version 2 refers to the Photoshop version not the incisor torque version sorry for the confusion [ Attachment: You are not allowed to view attachments ]

[bliaodds]

Hi Bleenz:

Can you describe in detail how you use Photoshop to place the torque template?
That looks really nice and it seems to work for you.
Please tell me how you do it.


Thanks

Brian

[bleenz]

Dear Brian,
Contact Iveta for my email and I  can send you the powerpoint on howto use it as well as the Photoshop file

Bernard

[DMcGann]

Bernard, thanks for the clarification.  Is this photoshop CS2?
   
Have you found a way to 'rotate' the image so the occlusal plane is horizontal?

[bliaodds]

Bernard:

Thanks for the help

Brian

[bliaodds]

Bernard:

It took me two days playing with Photoshop, but IT WORKS!!!!
THIS IS AWESOME!! Thank you so much.....
This should be made available to all the docs...

Brian