Pacific Coast Society of Orthodontists Bulletin Winter 2022 - 42

Clinical Practice
Pearls of the Pacific
Midline Correction During Finishing
Proffit et al.1
Dr. James Chen
San Francisco, CA
PCSO Bulletin Contributor
outlined the following four primary
stages of orthodontic treatment: leveling and
alignment, working phase, finishing/detailing,
and retention. Major midline deviations should be
corrected during the working phase of treatment,
and minor midline correction should be corrected
during the finishing and detailing stage. Minor
midline deviations are relatively simple to correct.
Choosing the wrong type of correction could prolong
orthodontic treatment unnecessarily. Midline
correction can be achieved with many different
types of mechanics and with different types of
results. In this Pearl, I outline a simple checklist
to help decide which type of midline correction
mechanics should be used during finishing and
detailing as well as how to skew your finishing
arch wire to correct minor midline deviations.
The following sequence is what I normally use to
evaluate and treat minor midline deviations:
1. Check the posterior occlusion. Midline deviations
could be attributed to residual Class II or
Class III posterior relationships. If the posterior
occlusion is Class I molar and canine, then the
midline deviation is primarily attributed to an
issue in the anterior region.
2. Check the overjet from canine to canine. Arch
form can become skewed during treatment
either due to poor arch coordination or a shift
of the wire to one side. If one side of the arch
has excessive overjet and the opposite side
is close to crossbite, then the solution to the
midline correction is centering the arches or
improving the arch coordination.
3. Check tooth size. If the first two items are not
the reason for the midline deviation, then a
tooth size discrepancy could be the cause of
the deviation. In this case, either interproximal
reduction or opening space for restorations
will solve the midline deviation.
If the midline deviation is attributed to item 2,
there are two methods to correct the situation.
The first is to use midline elastics; however, one
disadvantage of this method is the use of extended
elastic wear can lead to canting of the occlusal
plane. This is a product of the vertical force applied
by the elastics. The second method is to skew the
arch form to center the midlines. The simplest way
to do this is to skew the finishing wire, which is
much easier to do with stainless steel than beta
titanium. Step 1 is to flatten the canine curve on
the side opposite of where you want the midline to
move (Figure, step 1) and then accentuate the canine
curve on the side where you want the midline
(Figure, step 2). Finally, if bent correctly one side of
the wire will look shorter than the other and this
is ideal. Midline correction should be quick; if prolonged
time is needed, skewed arch wires can have
a negative effect on the final arch form.
Reference
1. Proffit W, Fields H, Larson B, Sarver D. Contemporary
Orthodontics. 6th ed. Amsterdam, the Netherlands:
Elsevier; 2018.
Skewing the arch form
42
PCSO Bulletin Winter 2022
Pacific Coast Society of Orthodontists Bulletin Winter 2022

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