Why did my teeth shift after the braces came off?
I often hear from patients that their teeth moved after
their braces came off and they want to know why. There are basically 3
reasons for a failed case (that was treated well.)
1. The patient did not wear their retainers properly. This
is patient error.
2. The patient did not eliminate mouth habits, and did not
wear appliances to protect them from their mouth habits. This is a combination
of patient and dentist error (if the dentist did not make the patient aware of
their habits, and/or did not make appliances that could protect the patient
from these habits.)
3. The patient grew unfavorably. No one had control over
this one.
(4. If the teeth were not aligned in the middle of the bone
ridge, they will relapse to be centered in the ridge again. The treating
dentist had control over this reason.)
The next few blogs will address these errors. Today we will
address #3: unfavorable growth.
Unfavorable growth is the growth that takes place after the
braces are removed which destroys the final bite. One jaw grows more than the
other. The teeth in each jaw may stay perfectly aligned, but the bones that
support the teeth may not stay in balance with each other.
We can all see that children look like their parents. Facial balance is also genetically
determined. Parents with “buck teeth” have children with “buck teeth”; Parents
with “underbites” have children with “underbites.” Although we can change the skeletal
balance and esthetics with orthodontic orthopedics in young patients, the
patients continue to grow after their active orthodontic treatment is
complete. A patient who started with their front teeth
sticking out “way too far” will relapse in that direction- their top jaw will
continue growing and after several years they may have front teeth that stick
out farther than when they completed treatment. This relapse growth issue is
seen most vividly in “underbite” cases. The bottom jaw will continue growing
for many years after the top jaw stops growing, so a patient who started with a
prominent lower jaw will continue growing that prominent lower jaw and the
lower jaw may “outgrow” the balance that had been achieved with the orthodontic
orthopedic treatment. In addition, lower jaw bones rotate internally, although the outside remodels and looks the same. The lower front teeth tip forward with this rotation and in order to stay behind the upper teeth, the lower teeth develop "middle age crowding."
The skull, like the rest of the body, shows early growth “high
up” and later growth “low down.” We see
this in babies who have large skulls with respect to the rest of the body
versus adults who have small skulls with respect to the rest of the body. The skull stops growing earlier than the legs
stop growing. Within the skull, the top
of the face stops growing earlier than the bottom of the face. The midface
stops growing earlier than the lower face.
With orthodontic orthopedics (palatal expansion with headgear treatment)
we can modify the growth of the maxilla (upper jaw), which is in the mid-face. Palatal
expansion is successful in girls until about age 12, and in boys until about
age 14, when the midface stops growing. While
creating width of the upper jaw (palatal expansion) forces can be exerted on
the jaw to restrain the growth (traditional straight pull headgear to the top
of the head and the back of the neck) or to increase the amount of growth in
the forward direction (with front pull headgear against the forehead and chin.)
These treatments are no longer effective after the midface has finished growing
because the sutures (the zippers between the bones) close with physical maturity.
The mandible (the lower jaw which is in the lower third of the face) continues
to grow for many more years than the maxilla (upper jaw bone), until about age 17 in girls, and
until about age 23 in boys. If the
mandible was genetically programmed to be small, we do not notice the forward
growth of the mandible after the maxilla stops growing. If the mandible was genetically programmed to
be large, the forward growth of the mandible is obvious and often results in a
return of the “underbite.”
When I treat “underbite” cases I overcorrect the forward
correction of the maxilla, leaving the young patients with the opposite problem
from which they presented. They start
with the upper teeth and jaw behind the lower teeth and jaw, and I finish them
with the upper teeth and jaw too far forward for the lower teeth and jaw. An
ideal bite has the upper front teeth one to two millimeters in front of the
lower front teeth. A Class III underbite
may have the upper front teeth behind or tip to tip to the lower front teeth. I overcorrect the jaw position leaving the
upper teeth three to four millimeters in front of the lower teeth in order to
allow for up to 2mm more lower jaw growth in the future. I do not aim for a correction of over-jet to
5mm because I do not want to take the risk that the lower jaw does not have a
late growth spurt, and the final result (as an adult) remains with excessive
over-jet (seen as “buck teeth.”) Anticipating how much relapse growth will take
place is an educated guess based on family history and the appearance of the
parents.
Another phenomenon, related to unfavorable growth is the relapse
of tooth rotations and teeth that grew in to the outside or inside of the arch
form. The longer the teeth “live” in the
poor position, the more they have ingrained that “memory” of that
position. If the size of the arch form
is corrected early and the teeth grow into a straight position, the teeth are
more likely to stay in a straight position.
If the jaw size is corrected and the teeth aligned within a year after
the teeth erupt, the teeth are more likely to stay in a straight position. If the jaw size is corrected as an early teenager,
the teeth already have a memory of the crooked position, and are more likely to
return to that crooked position after orthodontic treatment has been
completed. If the teeth are aligned in
adults, after facial growth is complete, the teeth are much more likely to
return to the crooked position. This is
why night time retainer wear is so important in patients whose teeth were
aligned later in life.
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