VINYL POLYETHER-2020

Abstract

Background: A new elastomeric impression material which is a combination of vinyl polysiloxane (VPS) and polyether (PE) elastomers called “polyvinyl ether silicone” (PVES) has been introduced with predictable accuracy and high‑quality impressions. There is insufficient data on mechanical properties of this material. Materials and Methods: A comparative study of mechanical properties of VPS, PE, and PVES was carried out using light‑ and heavy‑body consistencies of the three materials. Three standardized stainless steel molds were made to fabricate study specimens (n = 96). The specimens were tested for elastic recovery, strain under compression, tear energy, and tensile strength (TS) using the universal testing machine. Statistical analysis was done using two‑way analysis of variance test. Results: Elastic recovery was higher in VPS as compared to other two materials. Strain under compression was higher for PE followed by PVES. Tensile energy was significantly higher in PVS while TS was higher in VPS, followed by PVES and PE. Conclusion: PVES tested was found to be more flexible with high tensile energy. This material can be preferred in cases with undercut areas favoring the removal of impressions without tear and distortion. Keywords: Elastic recovery, strain under compression, tear strength, tensile strength

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Contemporary Clinical Dentistry • Volume 10 • Issue 2 • April-June 2019 • Pages 1-182
Volume 10 / Issue 2 /April - June 2019
Spine 8 mm

203 © 2020 Contemporary Clinical Dentistry | Published by Wolters Kluwer - Medknow
Introduction
The successful fabrication of restorations
largely depends on an accurate
impression from which a replica of the
intraoral structures can be precisely
created.[1,2] Elastomeric impression
materials have always been the choice
of material in xed prosthodontics, due
to inherent qualities such as reduced
marginal voids and distortion resulting in
improvedqualityofgypsumdies.[3]Among
available elastomeric materials, the vinyl
polysiloxanes (VPS) and polyethers (PEs)
are used most frequently. Advances in
elastomeric chemistries have led to the
inventionofanewgenerationofimpression
materials which is a combination of
polyvinyl and PE called “polyvinyl ether
silicone(PVES).”[4]
Few of the properties of this newly
introduced material, that is, PVES have
beenreportedbyseveralauthors.[5‑12]Nassar
etal.[5]investigatedthedimensionalstability
of ve PVES consistencies when stored
for up to 2 weeks, with and without using
Address for correspondence:
Dr. Suryakant C. Deogade,
C/o Vivek Thombre, Flat
No-301, Maharshi Gajanan
Apartment-3, Wanjari Nagar,
Nagpur - 440 003, Maharashtra,
India.
E-mail: dr_deogade@yahoo.
co.in
Abstract
Background: A new elastomeric impression material which is a combination of vinyl
polysiloxane (VPS) and polyether (PE) elastomers called “polyvinyl ether silicone” (PVES) has
beenintroduced withpredictable accuracyandhigh‑qualityimpressions.Thereis insucientdataon
mechanicalproperties ofthismaterial. Materials and Methods:Acomparative studyofmechanical
properties of VPS, PE, and PVES was carried out using light‑ and heavy‑body consistencies
of the three materials. Three standardized stainless steel molds were made to fabricate study
specimens(n = 96).The specimens were tested for elastic recovery,strainundercompression,tear
energy,and tensile strength (TS) using the universal testing machine. Statistical analysis was done
usingtwo‑wayanalysisofvariancetest.Results:Elasticrecovery was higher inVPSascompared
to other two materials. Strain under compression was higher for PE followed by PVES. Tensile
energy was signicantly higher in PVS while TS was higher in VPS, followed by PVES and PE.
Conclusion: PVES tested was found to be more exible with high tensile energy. This material
canbepreferredincases with undercut areas favoring theremovalofimpressionswithouttear and
distortion.
Keywords: Elastic recovery, strain under compression, tear strength, tensile strength
Mechanical Properties of a New Vinyl Polyether Silicone in Comparison to
Vinyl Polysiloxane and Polyether Elastomeric Impression Materials
Original Article
Pragya Pandey,
Sneha Mantri1,
Abhilasha Bhasin1,
Suryakant C.
Deogade2
Consultant Prosthodontist,
Clove Dental, Jaipur, Rajasthan,
1Department of Prosthodontics
and Crown and Bridge,
Hitkarini Dental College and
Hospital, Jabalpur,
Madhya Pradesh, 2Department
of Prosthodontics and Crown
and Bridge, Government Dental
College and Hospital, Medical
Campus, Medical Square,
Nagpur, Maharashtra, India
How to cite this article: Pandey P, Mantri S,
Bhasin A, Deogade SC. Mechanical properties of a
new vinyl polyether silicone in comparison to vinyl
polysiloxane and polyether elastomeric impression
materials. Contemp Clin Dent 2019;10:203‑7.
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distributed under the terms of the Creave Commons
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licensed under the idencal terms.
For reprints contact: reprints@medknow.com
a standard disinfection procedure. They
found that the PVES was dimensionally
stable for clinical use after disinfection for
30 min in glutaraldehyde and storage for
upto2weeks.Shetaaetal.[6]comparedthe
wettability,dimensionalchanges,exibility,
andtearresistance(TR)ofPVESandVPS
containing nanollers with conventional
VPS and PE impression materials. They
found that all materials were hydrophilic,
especially PVES and PE which recorded
the highest wettability. VPS containing
nanollersshowedthegreatestdimensional
stability.Asrelatedtoexibility,PE,VPES,
and PVS recorded the higher exibility
thanVPS containingnanollers,whileVPS
containingnanollersandPVESshowedthe
highestTR.PandeyandMehtra.[7]compared
the dimensional stability and accuracy
of PE, VPS, and PVES materials and
observed that PVES yielded more accurate
impressions than those of VPS and PE.
Nassar etal.[8] compared the advancing
contact angle of water on the surface of
severalsetelastomericimpressionmaterials
such as VPS, PVES, and PE. They found
that set VPS was more hydrophilic than
PVES and PE. Lakshmi etal.[9] evaluated
Access this article online
Website:
www.contempclindent.org
DOI: 10.4103/ccd.ccd_324_18
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Pandey, et al.: Mechanical properties of a new elastomeric impression material
the compatibility of VPS, PVES, and PE impression
materialstodierenttraymaterials.TheyreportedthatPE
showed highest bond strength with acrylic resin tray than
PVES,whilelight‑activatedresintrayproducedtheweakest
bond strength with all the three impression materials.
However, PVES showed higher bond strength than VPS.
Tabeshetal.[10] comparedtheimplantimpressionprecision
usingPE,VPS,andPVESmaterialswithdirectandindirect
techniques. They concluded that PE is recommended for
directtechniquewhilePE and PVES arerecommendedfor
indirect technique. Recommended technique for PVES is
eitherdirectorindirectandforPEandVPSisdirect.Other
studies[11,12] stated that PVES monophase impressions and
PVES dual‑viscosity impressions display the acceptable
accuracyforclinicalusewith immersion disinfection since
the results for PVES were comparable to the results for
representativePE andVPSmaterials.
For a successful clinical outcome, an impression material
should inherently have desirable physical as well as
mechanicalproperties.[13]Adequatemechanicalpropertiessuch
aselasticrecovery(K%),strainincompression(E%),TR,and
tensile strength (TS) ensure that the impression material can
withstand the various stresses upon removal of impression
from the mouth while maintaining dimensional stability and
integrity.[14] Elastic recovery is the ability of the impression
material to recover after deformation.[15] This deformation
is dependent on the depth of the undercut and is one of the
most important properties in assessing the suitability of an
impression material for clinical use. Strain in compression is
ameasureofthe exibility/stinessofmaterialsandindicates
whether the polymerized impression can be removed from
the mouth and have adequate stiness in the more exible
portions of impressions so that the poured gypsum cast can
be removed from the impression without fracture.[16] TR
indicates the ability of a material to withstand tearing in thin
interproximal and undercut areas and in the depth of the
gingivalsulcus, whileretrievalof impression.[17,18]
TS reects the maximum stress; a material can bear
under tension before the breaking limit. Maximum tensile
removal forces of impression materials have been shown
to be greater than maximum compressive seating forces,
especially when materials are stretched in tension as
they are pulled from undercuts, sharp line angles, and
interproximal spaces.[19‑21] The purpose of this in vitro
study was to comparatively evaluate the above‑mentioned
mechanical properties of VPS, PE, and new PVES
elastomeric impression materials. Null hypothesis stated
that there was no signicant dierence in the mechanical
propertiesof theimpressionmaterials andconsistencies.
Materials and Methods
The materials tested in the study were VPS (Flexceed, GC
DentalProductsCorp.,Japan),PE(ImpregumTMSoft‑3MESP,
3MDeutschland GmbH, Germany), and VPS (EXA’lenceTM,
GC Dental Products Corp., Japan). Light‑ and heavy‑body
consistencieswereusedfor all threematerials.Foreachtype
of material, 32 specimens were made and divided into four
subgroups(n=8)accordingtothepropertiestobetested,the
three standardized stainless steel (SS) molds were made for
three variable forms of specimens for dierent mechanical
properties to be tested. To fabricate rectangular specimens
forTE,arectangularSSmoldof 75 mm × 25 mm × 1 mm
dimension was made. For studying TS and K%, a 2 mm
wide and 1.5 mm thick dumbbell‑shaped mold with an
inner bar was made. A 25‑mm long section of the inner bar
was delineated by four semicircular notches in the mold.
For analyzing E%, a hollow cylindrical mold with internal
diameterof15mmandheight20mmwas made [Figure 1].
For each type of material, 32 specimens were made and
divided into four subgroups (n = 8) according to the
propertiestobetested[Figure 2].
Elastic recovery was tested according to ISO4823. The
specimensweredeformedby30%ofitsoriginallength(L),
then the load was released and after 2 min, the change
in length (DL) was measured. For measuring strain in
compression,loadwas added into the specimens gradually
overaperiodof10stoproduceastressof1000g/cm2,the
load was maintained for 30 s and the DL was measured.
Tear energy (TE)/Tear strength was measured using
specimenswithdimensions(75mm×25mm×1mm)as
speciedbyWebberand Ryge.Usingasharp razor blade,
a 50‑mm slit was made, producing trouser leg‑shaped
specimens (12.5 mm wide). The legs of the specimens
were placed vertically in opposite directions. The grip
separation speed was 20 mm/min. When testing TE, the
tearcandeviatefromthe central axis of thetestspecimen,
and then the calculation for the observed extension ratio
would not be accurate, so such specimens were discarded.
TS was measured following ASTMD412 (Test Method)
on dumbbell‑shaped specimens. Three measurements (for
thickness and width, respectively) were made, 1 at
the center and 1 at each reduced end.  The rate of
grip separation was 50 mm/min. TS was recorded and
calculatedbysoftware(Series IX,Version 7.27.00, Instron
Corp). All the tests were conducted using a screw‑driven
Universal Testing Machine (Model Mini4, Instron corp)
andDigimaticVernierCaliper.Statisticalanalysiswasdone
usingtwo‑way analysisofvariance (ANOVA).
Results
Table 1 lists the mean and standard deviations of tested
properties. For all the tested materials, K% was ≥98%.
E% was signicantly higher in PE material. Overall, the
light‑body material had signicantly lower TE and TS
than heavy‑body materials. TE was highest with PVES
and TS was highest with VPS material. ANOVA shown
in Table 2 describes that interaction between the material
and consistencies had statistically signicant inuence on
the properties tested. Pearson’s correlation coecient was
stronglypositive betweenK%andTS[Table3].
Contemporary Clinical Dentistry | Volume 10 | Issue 2 | April-June 2019 204

Pandey, et al.: Mechanical properties of a new elastomeric impression material
Discussion
The viscoelastic properties of the elastomeric impression
materialsplay a major role in their successfulapplications
as high accuracy impression materials.[13] The amount
of permanent deformation attributed to the dashpot is
dictatedby the duration of tension or compressionexerted
on the material.[22] An arbitrary 0.4% deformation has
been estimated to be the clinically signicant deformation
limit.[23]
Inthe present study,theviscoelastic/mechanical properties
of VPS, PE, and PVES were compared and correlated.
The null hypothesis that there is no dierence in the
mechanical properties of the impression materials and
consistencies tested was rejected. Elastic recovery is
important in determining the accuracy of an impression
material.[24]Jorgensendemonstratedthata60%deformation
was induced in an elastomeric impression material when
removing it from structures with undercuts 1 mm high
and deep.[25] de Araujo etal.[26] recorded the relationship
between the induced and permanent deformation of
elastomeric dental impression materials during and after
setting.Theyreported the meanrecoverytimerangesfrom
2.8–6.8min.Inthepresentstudy,allofthematerialstested
met the requirement of ISO4823, which requires ≥96.5%
recovery.[27]The PE and PVES had lower elastic recovery
than VPS and showed statistically signicant dierence.
The greater elastic recovery of PVS is attributed to the
excellent cross‑linking with the hydride group between
the polymeric chains.[13] However, among consistencies,
heavy body had higher K% than light body, due to the
presence of llers in the heavy body.These ndings were
inagreementwitha studybyLuetal.[14]in which silicone
materials showed greater recovery than PE. Inoue etal.[28]
have demonstrated that there was increase in permanent
deformation in thinner sections of set material than the
thicksections whensubjectedto shear.
The results of the present study showed that all the
tested values for E% were within the range required by
ISO4823(0.8%–20%forlight‑bodymaterial and 2%–20%
forheavy‑body material).[27]TheVPSwas more rigid than
Table 1: Elastic recovery, strain in compression, tear energy, and tensile strength of tested impression materials
Properties
VPS PE VPES
LB HB LB HB LB HB
K% 98.49±0.34 99.81±0.15 98.07±0.63 98.59±0.07 98.32±0.67 98.75±0.63
E% 5.66±0.25 3.38±0.24 9.22±0.13 8.41±0.86 8.16±0.95 7.41±0.48
TE(J/m2) 596.25±51.65 669.00±19.10 685.75±26.11 749.75±29.40 746.50±49.65 987.50±5.80
TS(MPa) 3.49±0.13 5.60±0.54 1.80±0.36 2.40±0.42 2.55±0.45 3.52±0.34
K%:Elasticrecovery;E%:Strainincompression;TE:Tearenergy;TS:Tensilestrength;VPS:Vinylpolysiloxane;PE:Polyether;
VPES:Vinylpolyethersilicone;HB:Heavybody;LB:Lightbody
Table 2: Summary of two‑way analysis of variance
K% E% TE TS
F P F P F P F P
Material 6.373 0.008* 120.099 0.000*(<0.001) 95.462 0.000*(<0.001) 79.301 0.000*(<0.001)
Consistency 14.847 0.001* 29.232 0.000*(<0.001) 80.648 0.000*(<0.001) 58.794 0.000*(<0.001)
Interaction 3.120 0.044* 4.514 0.026*(<0.05) 16.874 0.000*(<0.001) 8.066 0.003*(<0.001)
*Eectissignicantat0.05levels.K%:Elasticrecovery;E%:Strainincompression;TE:Tearenergy;TS:Tensilestrength
Table 3: Correlation between the mechanical properties
tested
Correlation between Pearson’s correlation coecient P
K%andE% −0.666
(strongnegativerelationship)
0.000*
K%andTE −0.016
(noornegligiblerelationship)
0.939
K%andTS 0.746
(verystrongpositiverelationship)
0.000*
E%andTE 0.319
(moderatepositiverelationship)
0.128
E%andTS −0.898
(verystrongnegativerelationship)
0.000*
TEandTS −0.056
(noornegligiblerelationship)
0.794
*Correlationissignicantat0.05levels.K%:Elasticrecovery;
E%:Strainincompression;TE:Tearenergy;TS:Tensilestrength
Figure1:Preparationofthreedierenttypesofspecimens
205 Contemporary Clinical Dentistry | Volume 10 | Issue 2 | April-June 2019

Pandey, et al.: Mechanical properties of a new elastomeric impression material
the PE and PVES. However, the newer generation of PE
has been incorporated with more amount of plasticizes,
renderingitmoreexible.[29]According to Jamani etal.[30],
rigidity of material is always greater when tested 30 min
after the start of mix than when tested at the setting time.
This is because the polymerization continues after the
settingtime.[30]This wassupportedbyHarcourtwho found
that leaving the impression in the mouth beyond setting
time led to an in increase in rigidity.[31] Furthermore,
E% was correlated with K%, TE, and TS. The exible
materialswouldbeexpectedtohavelesscross‑linking,less
llers, or more plasticizer, so they would be expected to
be weaker than the stier materials and more easily torn.
Elastic recovery and strain in compression were inversely
correlated. When developing materials, a balance should
be chosen that maximizes the elastic recovery, while
maintainingexibility inanacceptablerange.[32]
TEindicates the ability of a material to withstand tearing
inthin interproximalareasandinthedepthofthegingival
sulcus. Tear strength is inuenced by the chemical
composition, consistency, and manner of removal of
material. A rapid rate of force application during removal
usuallyincreasesthetearstrength.[14]Therearenostandard
methods proposed by the American National Standard
Institution/American Dental Association specication No.
19 or ISO4823 to determine the tear strength.[33] Rivlin
and Thomas[34] developed a simple extension tear test,
currentlyusedtostudy the tear strength.The method was
later adapted by Webber and Ryge as “Trouser tear test.”
In the present study, TE was measured by the “Trouser
tear test” developed for thin sections of elastomeric
materials.[24] Results showed that there was statistically
signicantdierenceinTEamongallthree materials.The
TE of PVES and PE was higher than the VPS. Braden
and Elliot. concluded that PE had shear modulus four
times high as that of addition PVS, and there is direct
relationship between the shear modulus and diculty
encounteredin removinganimpressionfromthemouth.[35]
StatisticalanalysisshowedTSofVPSwashigherthan PE
andPVES(mean,TS = 3.49). However,PVESwasbetter
thanPEinthis regard. Thisresultwasinaccordance with
asimilarstudybyLu,[22]in whichTSofadditionsilicones
was greater than the PE. Lawson etal.[36] compared the
elastic recovery from tensile strain for 5‑VPS materials.
This study demonstrated that elastomeric impression
materials permanently deform following 50% and 100%
tensile strains. The variation in tensile elastic recovery
among VPS materials is related to components of their
composition, including the proportions of base silica,
copolymer, ller, and chain extenders.[35,36] Thus, the
selection of an impression material for a particular
application should be based on property data, rather
than on the type and class of the elastomeric impression
material.[37,38]
Thepresentstudywasconductedinan in vitro environment.
Although the impressions were made of standardized SS
dies, the intraoral conditions could not be simulated to
determine the acceptable range of viscoelastic parameters,
a clinical investigation should be undertaken, in which
several materials of known modulus should be used for
impressiontaking.
Conclusion
Within the limitations of this study, it could be concluded
that the newer material PVES tested was found to be
more exible with high‑tensile energy. This material can
be preferred in cases with undercut areas, favoring the
removalof impressionswithouttear anddistortion.
Figure 2: Grouping of specimens
Contemporary Clinical Dentistry | Volume 10 | Issue 2 | April-June 2019 206

Pandey, et al.: Mechanical properties of a new elastomeric impression material
Financial support and sponsorship
Nil.
Conicts of interest
Thereare noconictsof interest.
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207 Contemporary Clinical Dentistry | Volume 10 | Issue 2 | April-June 2019