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Compend. Oral Sci:vol1(4);2015;21-31

materials is a desirable property in ensuring and McCabe & Carrick (10) had attempted to
accurate casts (6). Polyether has been shown simulate moist surface during impression mak-
to be one of the most hydrophilic impression ing by utilising fine mist of water on stainless
material (1,3,7,8) owing to the functional groups steel surface and moist gypsum casts respec-
that chemically attract and interact with water tively.
molecules via hydrogen bonding (9,10). Whilst
Although the literature had addressed the is-
polyvinylsiloxane has been rendered hydro-
sues of hydrophilicity and surface reproduction
philic by the addition of nonionic surfactants
of elastomeric impression materials on moist
(11,12). The increased in wettability results
surfaces, there is lack of information on the ef-
from the surfactants acting through a diffusion
fect of different finishing margins of tooth prepa-
transfer of surfactant molecules from the polyvi-
ration either supra- or subgingivally placed.
nylsiloxane into the aqueous phase (5).
McCabe & Carrick., 2006 (10) investigated the
The literature revealed that various methods effect of depth of V-shaped grooves between 5
has been employed to determine the hydro- μm to 180 μm. They reported that polyether
philicity of elastomeric impression materials. exhibited the best surface detail reproduction
Contact angle measurement is the most popu- when impression were made on moist gypsum
lar (6,8,10,13) and some had used the Drop casts (10,18,19). Finger et al (20) investigated
Shape Analysis System (14,15). Most of the the depth reproduction of different sulcus width
studies showed that polyether is most hydro- (50,100 and 200) μm. They found that polyeth-
philic followed by polyvinylsiloxane er material reproduced narrow sulcus better
(14,16,17,18) but has not been demonstrated in than other impression materials.
a simulated clinical condition. The ability of
Finishing margins for extracoronal restorations
elastomeric impression materials to reproduce
can either be knife-edged, chamfer, bevel,
surface details accurately on moist surface is
shoulder or shoulder with bevel. Geometrically
directly linked to the hydrophilic behaviour of
the V-shaped groove can represent the knife-
these materials and the accuracy of surface
edge, chamfer and beveled type finishing mar-
detail reproduction can be assessed using the
gins. However, a U-shaped groove is probably
standard method for elastomer as described by
more appropriate to represent the shoulder or
ISO 4823: 2000 where three engraved lines;
shoulder with bevel typed finishing margins
20, 50 and 75 μm in width on a stainless steel
(Figure 1).
reference block must be reproduced in full
length between two perpendicular reference Furthermore, there is no information in the liter-
lines when inspected under a stereomicroscope ature correlating both shapes and depth of
at 12x magnification. However, this testing tooth preparation margins surface detail repro-

model is primarily a method to assess the con- duction of elastomeric impression materials.
sistent quality of the impression material and
Therefore, the objective of this study is to inves-
does not simulate clinical conditions where
tigate the effect of shape and depth of grooves
moisture on dental substrate and surrounding
on moist stone cast on the surface detail repro-
soft tissues is a major concern. Petrie et al (8)
duction of elastomeric impression materials.

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