Maxilloprosth material /orthodontic courses by Indian dental academy

METHACRYLOXYPROPYL
TERMINATEDPOLYDIMETHYL
SILOXANE
)A NEW ORGANOSILICON
MAXILLOFACIALPROSTHETIC
MATRERIAL(
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INDIAN DENTAL ACADEMY
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INTRODUCTION
• The most widely used silicone elastomers
for maxillofacial prosthesis are ,MDX4-
4210,A -2186 AND DOW ORNING
MEDICAL ADHESIVE TYPE A

• The components in A-2186 and MD4-
4210 are available as two contents and
both materials cure by same mechanism.

• Although these materials have improved
tear strength, both A-2186 and MDX4 –
4210 have low adhesiveness due to their
hydrophobic nature and the curing
reaction starts immediately after mixing of
the two components , which decrees the
working time.

• Medical adhesive type A is hydroxyl
terminated polydimethyl silioxane and it
requires moisture to cure, therefore
material inside a mold require long time to
cure.

• Methacryloxy propyl –terminated
polymethylsiloxane is silicone elastomer
with a unique chemical structure. The
cross linkable polysiloxane provides the
silicone with electrometric characteristics.

• The dimethacrylate groups located on the
chain ends readily undergo free radical
thermal polymerization and cross linking.
• Incorporation of methacrylate group in the
silicone reduces the hydrophobicity of the
silicone that enhances the adhesive bond
strength to non – silicone – based
adhesives.

• Because MPDS cures thermally , its
working time for prosthesis fabrication is
long.

Manipulation
• MPDS based maxillofacial materials were
prepared by dispersing the thermal
initiator into the MPDS first, fallowed by
through mixing of the mixture with the
fillers and additives. Later the material is
introduced in to the stone or stainless
steel mold to cure thermally.

• Physical and mechanical properties of
MPDS – MF depends upon the degree of
cross linking and the type and
concentration of fillers in the elastomer net
work.
Physical & Mechanical Properties

cure method Hardness
(khn)
Elongation
(%)
Tensilestength
(mpa)
Tear
strength/cm)
Non-pigmented
(mpds)
Ss mold oven
cured
34.0 358 4.61 162.80
Stone mold
oven cured
30.7 404 4.84 181.03
Stone mold
water bath
cured
28.7 471 4.76 184.15
Mechanical properties of MPDS

cure method Hardness Elongation(%) Tensile
strength
(mpa)
Tear
strength/cm)
Pigmented
(mpds)
Ss mold oven
cure
31.1 358 3.91 160.57
Stone mould
oven cure
31.5 383 4.48 187.26
Stone mold water
bath cure
27.8 455 4.31 202.82

Discussion
• The mechanical properties of MPDS
materials cured In convection oven using
stainless steel mold were compared
those of the MPDS material cured in stone
• The non pigmented materials cured in a
stainless steel mold are harder than those
cured in stone mold.

• The water bath cured specimen are softer
and more stretchable when compared with
the cured materials in stainless steel mold
or stone mold .
• Pigments have effect on the material
cured in the stainless steel molds, but not
those cured in the stone molds.

• The hardness of MPDS material is same
when compared with A-2186, how ever ,
the tensile strength ,tear strength and
adhesive bonding strength of MPDS is
higher than A-2186.

conclusion
• The improved properties of MPDS-MF are
related to its chemical structure and the
polydimethysiloxane polymer MPDS
provides the silicone elastomer
characteristics

• The dimethacrylate groups locate other
chain ends readily undergo free radical
thermal polymerization and cross linking .
• Presence of methacrylate groups in the
polymer network enhances the tear
strength, tensile strength, bonding
strength to the adhesives and
dispensability with the pigments.

• The results obtained from the studies
suggest that MPDS –MF is suitable for
use as maxillofacial prosthetic materail.

Maxilloprosth material /orthodontic courses by Indian dental academy

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