Orthotown September 2020 - 22

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Mechanics in Extraction Cases
A recent grad takes to the boards for the first time to get some advice on mechanics

mas000
Member Since: 08/07/17
Post: 1 of 15

Hi, first-time poster here and recent ortho grad. Being thrust into the "real world" and trying
to pick up simpler and perhaps more convenient mechanics has been interesting.
I'm curious how others carry out their extraction treatments-for example, after bracketing
and having the extractions done, do you level and align on round wires (even if that means crowded
incisors will flare and you'll have to roundtrip), working your way up to heavy rectangular stainless
steel wires, and then powerchaining first the canines and then the full arches with elastics as
needed to back up your anchorage? Do you sometimes just go ahead and chain the full arches on
the rectangular steel wires without retracting canines first if the canine relationship starts Class I
(like in a bimax or U/L Class I crowded case)? Do you level and align just until you can get into
a round stainless steel and then do your canine retraction on that? Do you worry about lower
anchorage or, because of the greater mandibular bone density, are you less concerned?
I was trained with lacebacks used on round (.016) and rectangular (.019x.025) NiTi for canine
retraction (which I actually loved, but I suppose poses hygiene issues and is more difficult and
inconvenient for assistants), followed by retraction of U2-2 with active tiebacks from crimpable
hooks distal to the U2s to the U6s. I was also trained with sectional loop mechanics where only
the two teeth adjacent to the extraction site are bracketed, and not bracketing crowded incisors
initially and instead open-coiling from canine to canine to push the canines distally into extraction
spaces on an .018 SS before establishing enough space and then bracketing the incisors. So, I'm
well-trained in these techniques, but they don't fit into the flow of my current practice.
I would like to learn how you all sequence out your extraction cases. Specifics on wire sizes
and such would be extremely helpful as well. Thank you so much in advance! ■
7/31/2020

fesdds
Member Since: 05/22/08
Post: 2 of 15

Obviously it is going to vary a lot based on where the crowding is and which direction you
want incisors versus molars to go.
I will give you an average situation for me. I like to keep things simpler when possible. I also
love to take out 5s way more than 4s. So let's say I extracted U/L5s. I would most of the time PT
(power thread) U/L4-6 on my .014n wires. (Could also do 4-7 if need more anchorage). Then
next visit, go to 16x22n and PT4-6 again if needed. Then assess again on 19x25n. Will PC U2-2
if needed on this wire. Then put 19x25's and PC6-6, might do 7-7 if needing more anchorage.
If I take out 4s, will PT 3-5, 3-6 or 3-7 depending on anchorage needs. I think NiTi closing
springs on a posted wire are awesome and will do this a couple times a year, but PC is just easier
with the staff and kids want fresh colors anyway. ■
7/31/2020

mas000
Member Since: 08/07/17
Post: 3 of 15

Thanks so much for your detailed response! Are you doing the PT over the wire or under?
When we used PT in residency, we did it under the wire, which posed the same (or higher) hygiene
risks than lacebacks do. If you're doing it over the wire, that sounds nice and clean, and it's great
to be able to start space closure on your .014 NT!
Also, do you use elastics to reinforce anchorage? What about max anchorage appliances, like
Nances or LLHAs? I've noticed those are used less frequently, if at all, out in practice as compared
with in my residency. ■
7/31/2020

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