Pacific Coast Society of Orthodontists Bulletin Summer 2020 - 66

Presentation Summary

Predictors of EARR
Is it possible to predict root resorption in our
patients?
There appears to be a wide variation in the incidence of EARR between orthodontic offices, but
there is a 50-50 probability between males and
females. With respect to age, there may be weak
evidence that non-growers have a greater risk, but
this is inconclusive. With regard to root shape, it
has been speculated that dilacerated, irregular,
pointed, or pipette-shaped root ends theoretically
receive more stress, but we are not really at the
point where specific roots can be identified as being at greater risk. Nonetheless, we can still collect
useful information from 2D panoramic x-rays.
There is no clear evidence, but it has been suggested that it might be associated with thyroid or
other endocrine problems. There might also be an
association with patients having inflamed tissue
due to asthma as well as those with a bone and
hard tissue disorder (e.g., Turner Syndrome). While
familial expansile osteolysis is a rare syndrome,
most patients who have it will experience major
orthodontic root resorption. Multiple types of idiopathic EARR are familial and have a "big" impact.

66	

if there are multiple short roots before treatment,
Dr. Sameshima suggests trying to avoid longer
treatment times. Individuals in the Hispanic population are more likely to have preexisting short
root anomalies in their maxillary incisors and
maxillary and mandibular second premolars.
Studies differ as to the actual likelihood that a
patient will experience root shortening from
orthodontics. There is a decreased risk for
incomplete roots with immature (open) apices.
Teeth with "stunted" root growth tend to have
a smaller amount of resorption at the end of
orthodontic treatment compared to teeth with an
average root length. Endodontically treated teeth
either do not resorb or have a decreasing amount
of resorption, so there may be a protective effect
here.

Treatment time is an important factor in treatment planning because longer treatment times
are associated with an increase in maxillary
incisor root resorption. Root apex displacement,
along with horizontal and vertical movements
(such as with a large overjet correction), all tend
to be related to root resorption. Bear in mind that
resorption also takes place on the surfaces that
cannot be seen in a typical 2D image. While there
is an insignificant correlation between EARR and
the type of malocclusion, crown/root ratio, or
amount of decalcification, recent literature supports the concept that resorption is greater when
there is a genetic predisposition in combination
with extended treatment times and higher force
levels, but severe EARR can occur randomly, too.

Current EARR Topics
With temporary skeletal anchorage devices, we
can achieve absolute orthodontic tooth movement such as the intrusion of maxillary central incisors or the collective intrusion of maxillary second premolars, first molars, and second molars.
Fortunately, the maxillary first molar is typically a
strong, robust tooth, so root resorption is typically
not an issue with these teeth, even when a single
molar is intruded by up to 8 mm. For other teeth,
some resorption is to be expected with absolute
intrusion, even when only light forces are applied.
Interestingly, apical resorption appeared to be
minimal in cases treated with clear aligners between 2002 and 2009, but the roots did not move
very far in these cases. In another sample of 100
clear aligner cases, 4 to 6% of the incisors showed
greater than 20% resorption. It would seem that
there may be less resorption risk with accelerated
tooth movement (with the shorter treatment
time involved), but biologically, the opposite may
be true, with faster tooth movement. There is no
conclusive evidence either way.

Are shorter roots at greater risk?
The good news is that risk increases with greater
root length, but the bad news is that when short
roots resorb, they can get "really" short. We can
move teeth with short roots, and there is no
evidence of a higher risk of resorption. However,

Informed consent forms published by the American Association of Orthodontists and California
Association of Orthodontists are good to use.
Talk about root resorption if you suspect that a
patient is at a higher risk level. Before treatment
in these cases, take good periapical (PA) x-rays or

PCSO Bulletin    Summer 2020



Pacific Coast Society of Orthodontists Bulletin Summer 2020

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