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Plastazote: Pratitioners' Choice for Diabetic Orthotics
By Robert W. Keller, PhD For many years, foot health professionals have used pink
Plastazote® as the standard material for the top layer of foot
orthotics for diabetic patients. One of the primary reasons it is
widely considered to be the safest and best material for this layer
of foot orthotics is the lack of residual chemicals.
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Figure 1 |
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Plastazote foam is produced with only pure nitrogen. Other foams
use chemical blowing agents, which leave behind residual chemicals
such as ammonia and urea. Even low levels of these residual
chemicals can present a risk of irritation or allergic reaction to
the diabetic patient's foot. The level of chemicals present in
cross-linked foams typically exceeds acceptable levels listed in
the Code of Federal Regulations for repeated food contact (United
States Government, 2003).
This means that just as these chemicals can cause problems when
absorbed into the body through food, they can cause a risk when
absorbed through the skin, especially when ulcers or other wounds
are present.
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Figure 2 |
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In tests conducted, P-Cell and Plastacell-P provide better
compression set and shock absorption but are nearly twice the bulk
density as pink Plastazote, which would explain most of the
property differences. Their broad cell size distribution is typical
of foams produced using chemical blowing agents. Also in Table I,
other high-density materials are shown which would give better
compression set resistance, less pack-down, and better cushioning
than both P-Cell and Plastacell-P.
While beneficial, shock absorption is not the primary goal of
the top layer of a diabetic orthotic--conformance is. Several
experiments (see Figure 1) measuring the conformance of pink
Plastazote were performed in athletic and business shoes simulating
the typical use of foot orthotics. The experiments demonstrated the
benefits of this near-the-skin top layer by providing soft comfort,
shock absorption, rapid conformance, and protection to the
immediate skin. Previously published data shows P-Cell and
Plastacell-P's higher densities would slow conformance on
compression set. Since the rapid conformance of Plastazote is most
desirable for the top layer of the orthotic for a diabetic foot,
claims that P-Cell compresses less than pink Plastazote can be
misleading when choosing the most appropriate material to use.
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Figure 3 |
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Pink Plastazote continues to be the material of choice for foot
health professionals, because, as we stated previously, it is
foamed with only pure nitrogen. This eliminates potentially
irritating chemicals, thus limiting the risk to your patients. It
is also an industry standard because the top layer conforms rapidly
to the individual foot, providing a glove-fit which limits rubbing
retarding potential blister or callus formation. The thicker,
stiffer foams and gels used on the lower parts of the orthotic will
provide additional shock absorption for the foot.
In general, but especially when trying to minimize the risk of
potential infection for diabetic patients, the cleanest foams with
the best conformance rates should be used in the top layer of foot
orthotics. Heavier density materials are not the safest choice for
use with foot orthotics for diabetic patients and are best utilized
for shock absorption in lower layers.
Professionals in the healthcare arena have a responsibility to
use the safest and most appropriate material in the care of their
patients. For more than 30 years, pink Plastazote has been proven
the best material for the top layer of foot orthotics, and it
continues to be the most trusted choice. Robert W. Keller, PhD is President of Zotefoams Inc., Walton, Kentucky.
References
Sax, N.I. Dangerous Properties of Industrial Materials. 6th Ed., Van Nostrand Reinhold. New York. 1984. p. 340. United States Government (2002). 21CFR 177.1520. In (Ed.),Code of Federal Regulations, Part 21 (Rev. ed. 2002). Washington, DC: US Government Printing office. Marty, R. 2003 – Data Supports Use of P-cell in Diabe Footwear. Biomechanics, X(3), 69. 
Table Of Contents - November 2003
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