Does It Play a Role in Orthodontic Treatment?
Presented by Dr. Ib Leth Nielsen.
Summarized by Dr. Robert Quinn, Central Region Editor
we provide our
young patients is an
understanding of how
their faces are changing
while under our care.
If we either don’t
understand or don’t
plan for these changes
we are shortchanging
our patients. Reduced
friction brackets, temporary
anchorage devices, lasers
—all these recent technological advances pale in their
influence compared to the growth-related changes our
patients are experiencing.
The amazing aspect of growth is that it is not mysterious.
Similar to orthodontic mechanics, when we understand it
we can take advantage of it to produce a superior outcome.
Fortunately, 80% of our patients have mandibles that undergo an anterior or forward growth rotation. This growth
pattern, when taken to its extreme, results in a severe
overbite and short lower face. Posterior or backward rotation of the mandible during growth results in an anterior
open bite and long lower face.
Growth rotations can be predicted based on structural criteria in the mandible. A short lower face height, anterior
inclination of the symphysis, thicker cortical bone below
the symphysis, and a characteristic downward convexity
of the lower anterior border of the mandible are all predictors of a forward growth rotation. Backward rotation can
be predicted by an increased anterior face height, a backward inclination of the mandible, posterior inclination of
the symphysis, and a thin and straight cortical border of
the mandible. Once we develop an eye for these criteria
we can use them to construct custom treatment and retention plans for our patients.
Patients with short lower face heights, the so-called
forward rotators, should be started with an early
phase of treatment and the anterior occlusion maintained with a bite plate and lower lingual arch. These
patients are at risk for developing a deep overbite and
Avoid extractions in short lower facial height patients.
Expand and procline incisors to maintain a fulcrum at
the incisors and prevent the overbite from deepening.
Don’t base extraction decision solely on crowding.
Maxillary premolar extraction treatment to resolve a
Class II malocclusion should never be commenced
prior to cessation of mandibular growth as determined by a hand wrist radiograph. If mandibular
growth continues it may be impossible to close the
extraction sites, and crowding of the lower incisors
during or after retention will follow.
Long lower face patients with crowding often need
four premolar extractions to leave the incisors more
upright on the mandible. If treated non-extraction,
you will likely see the lower anteriors tip lingually
and crowd after treatment.
When we don’t take the time to understand it, we tell our
patients growth is unpredictable and may adversely affect
their treatment outcome. We even devote a paragraph to it
on “Risk and Limitation” forms.
Arne Bjork published the definitive work on facial growth
over 30 years ago, but its lessons are still not widely
incorporated into our treatment plans. Dr. Nielsen takes
these lessons and shows us how to use them to make our
treatment more predictable.
P C S O B U L L ET I N • S P R I N G 2 0 0 7
Patients with a strong backward rotation and open
bite should not be treated until growth has ceased.
They will often require surgery to produce any
improvement in their skeletal balance, and treatment during growth may compromise the benefits
Class III patients, especially
those with mandibular asymmetry, should not be treated
until growth has stopped.
This can only be determined
by head films superimposed
one year apart, as the mandible does not completes its
growth until the age of 21
to 22 in boys, several years
after growth in height is
S P R I N G 2 0 0 7 • P C S O B U L L ET I N
With respect to the post-treatment period, Dr. Nielsen
made the following observations:
The best retainer is a good occlusion.
Mandibular teeth will upright in most forward
and backward rotating patients after treatment.
The alignment can best be held by a bonded lingual
retainer continued well past the
cessation of mandibular growth
at 20 to 22 years of age.