Pacific Coast Society of Orthodontists Bulletin Spring 2020 - 36

Let's Talk About That

initial malocclusion, opposing arches must eventually be compatible for occlusion to be correct;
however, the needs within one arch (identified by
ICD) are seldom inversely reciprocal to the needs
in the other. Traditionally used terminology such
as "Class II mechanics" or "Class III mechanics"
does not suffice because it does not identify the
needs within individual arches, does not indicate
whether or not there is a skeletal component to
the malocclusion, and does not relate the problem
to the patient's facial appearance. Asking how to
correct a Class II is analogous to asking how to
repair a broken bicycle. The answer depends on
exactly what the problem is. The term Class II is,
at best, synonymous with broken; however, not
enough information is embedded to answer your
original question. As mentioned earlier, we do not
use Angle's classification system and have not
for a very long time. In fact, we view its continued
use as perhaps the most significant problem in
orthodontics today because it tacitly justifies
treatment aimed at the indiscriminate resolution
of overjet, or neutralizing interarch relationships,
without regard to other factors. In contrast, using
the six elements as the basis for diagnosis precisely reveals the source(s) of the malocclusion, and
treatment can be targeted accordingly.
Suffice it to say that if the ICDs are resolved in
both arches and jaw positions are corrected to six
element goals, then the malocclusion, regardless of its pretreatment phenotype, will be fully
corrected, unless leaving overjet was intentionally built in to the plan. It is exceedingly unlikely
that any so-called Class II corrector (i.e., Herbst®,
Forsus™, Carriere®, MARA, Twin Block, etc.) can
be expected to resolve the ICDs in both arches
and correct jaw positions exactly as needed. For
these reasons, we avoid the use of functional
appliances (fixed or removable) or other forms of
inherently reciprocal interarch mechanics. Some
such devices, particularly a Carrier-type appliance,
also cause significant vertical problems in the
form of dental extrusion and increased lower facial heights, which we think should be avoided.25
All of the aforementioned devices are capable

of neutralizing AP interarch relationships but
rarely in a way that produces element I (optimal
arches) and element II (optimal AP jaw positions)
simultaneously. This may come across as an
evasive answer to your question, but those who
understand the six elements know exactly what I
am trying to say.
Knowing and understanding the ICD is a huge advantage in guiding treatment decisions because
it relates to the needs within the arches individually and allows force systems to be designed
independently for each arch. This may take the
form of mesialization (+ICD), distalization (−ICD >
−6), or extractions (−ICD < −6). Whenever possible, force systems are kept within the arch being
treated and force vectors are kept as parallel to
the occlusal plane as possible, or in an intrusive
direction. If ICD values in opposing arches are
indeed equal and opposite, we do occasionally
resort to using conventional interarch elastics,
but when doing so, we try to keep the duration to
a minimum and to employ tactics to mitigate the
inherent vertical side effects.
Correcting the ICDs produces two opposing
compatible arches (element I), but AP interarch
relationships still may not be correct if AP jaw
positions are not corrected (element II). As for
treating AP jaw positions, it boils down to growth
modification or orthognathic surgery. The age of
the patient as well as the nature and severity of
the jaw-position discrepancy determine which
one is appropriate.
PT: What are your thoughts regarding jaw growth
modification?
WA: The short answer is that the position and
width of the maxilla can be modified in growing
patients because there are sutures. The mandible
obviously lacks sutures, so our influence on its dimensions is decidedly modest, if not insignificant.
The position of the mandible can be affected
indirectly by encouraging clockwise or counterclockwise rotation secondary to vertical changes

PCSO Bulletin Spring 2020

Pacific Coast Society of Orthodontists Bulletin Spring 2020

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Spring 2020