The curious aesthetics of lip-trapping compensation
in mandibular-deficient patients
by Chad Foster, DDS, MS, editorial director
Much attention is paid to the upper lip
and the nasolabial angle as they relate to
soft-tissue profile aesthetics, but the lower
lip is obviously important to consider as well.
In some mildly mandibular deficient
Class II patients with excess overjet, “lower
lip trapping” (lower lip resting against upper
incisors) occurs as compensation by the soft
tissue, which to some degree can serve to
“mask” the underlying hard-tissue deficiency.
In some of these cases it can present as a
favorable aesthetic profile compensation.
Observe this in the two patients here, in
both photos and cephalometric X-rays.
As the lower lip reaches and rolls forward,
it not only gives a more forward (Class I)
appearance of the lower lip—to visualize,
cover everything below the lower lip of
these two patients and assess profile—it
also significantly increases the “projected”
surface area of the lower lip vermilion display
as the lip rolls forward and down.
In the two cases below, this sensitive
lower lip position is wholly dependent on
the AP position of the upper incisors, as
evident on ceph. Most often in these cases,
advancing the mandible is ideal, but if
not an option (adult patients who decline
surgery), special attention should be given
to any amount of upper incisor retraction
if attempting to dentally camouflage the
skeletal disharmony—particularly if the
upper incisors are in a good position. What
do we expect to happen to this “masking” if
the uppers come back at all? The lower lip
is actively resting on the upper incisor; it is
not passively positioned there, which more
so would be the case in a normal mandible
where mild upper incisor retraction might
have less effect on the aesthetic AP position
and vermilion display of the lower lip. As
the upper incisors go back, so will the
lower lip as it decompensates, which can
be at the expense of the lower lip aesthetic
presentation. Keep in mind that lower lip
pressure on incisors is 2½ times that of
upper lip pressure.1
Our treatment plans should consider not
just fixing what is bad, but also protecting
what is good. Sometimes nature has a subtle
way of doing what is best in a compromised
situation. I think this concept applies in how
we should treat some unique presentations
of overjet/lip trapping. Obviously, not in
every case is lip trapping an aesthetic benefit!
Often it can be quite unaesthetic. How it
presents in each case is quite unique, which
demands our unique appreciation of each
individual presentation.
Reference
1. Southard, Thomas E., et al. “Orthodontics in the Vertical
Dimension.” Wiley Blackwell, 2015
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