Journal of
Dental Research
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Effect of Cavity Depth and Application Technique on Marginal Adaptation of Resins in Dentin
Cavities
E.K. Hansen
J DENT RES 1986 65: 1319
DOI: 10.1177/00220345860650110701
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Effect of Cavity Depth and Application Technique
on Marginal Adaptation of Resins in Dentin Cavities
E. K. HANSEN
Department of Technology, Royal Dental College, Blegdamsvej 3C, DK-2200 Copenhagen N, Denmark
The wall-to-wall polymerization contraction of two restorative resins
was investigated in butt-joint dentin cavities prepared in extracted
human teeth. The cavity diameter was 4 mm, and the cavity depth
ranged between 0.5 and 3.0 mm. The width of the maximum marginal
contraction gap was measured, using a light microscope, approximately 0.1 mm below the original free surfaces of the fillings. It was
found that increasing the cavity depth from 0.5 to 3.0 mm did not
influence the marginal contraction gap close to the free surfaces of
the fillings. It was also found that a two-phase application technique,
where the surface of the first layer was placed parallel to the free
surface of the cavity, did not reduce the marginal contraction gap,
while a two-phase technique with oblique layers resulted in approximately a 25% reduction.
One of the basic drawbacks of restorative resins is the inevitable shrinkage during their polymerization; this shrinkage is
often measured as the volume contraction of free test specimens (Lee et al., 1969; Dennison and Craig, 1972; Goldman,
1983). However, the volume polymerization contraction has
little, if any, relationship to the actual wall-to-wall polymerization contraction in a dental cavity (Asmussen and Jorgensen,
1971; Hansen, 1986). One of the reasons for the discrepancy
between the volume contraction of a free test specimen and
the wall-to-wall contraction in a cavity is probably that the
volume contraction is independent of several important variables, such as the cavity design, the filling surplus, the area of
the free surface of the filling, the contraction pattern in a dental
cavity, and the Theological properties of the restorative resin
used (Knappwost, 1951; Bowen, 1967; Asmussen, 1975; Hansen, 1982, 1984, 1986; Davidson et al., 1984).
The purpose of the present study was to investigate the
influence of cavity depth and different application techniques
on the maximum marginal contraction gap of restorative resins
in butt-joint dentin cavities.
traction gap was then measured, using a light microscope
(Reichert MeF Universal Microscope, Vienna, Austria, 8 X
63) with a measuring ocular. All procedures except cavity
preparation and handling/mixing of the restorative materials
were carried out in a room maintained at 36.5 + 0.50C.
In the present investigation, two different experiments were
carried out:
Group 1. - The cavity diameter was 4 mm and the cavity
depth either 0.5, 1.0, 1.5, 2.0, 2.5, or 3.0 mm. The cavities
were cleaned for 10 seconds with a cotton pellet soaked in a
3% hydrogen peroxide solution, followed by water spray and
air-drying, both for 10 seconds. Two composite resins were
tested: Silux, a light-activated microfilled restorative, and Concise, a chemically-activated macrofilled restorative. The materials were applied with a syringe (Hawe-Neos, Gentilino,
Switzerland), and the free surface of the filling was covered
with a matrix (Hawe-Neos). The chemically-activated resin
was polymerized with light finger pressure on the matrix while
the light-activated resin was irradiated for 25 sec with a visiblelight curing unit (3M/LC lamp, 3M A/S); close contact was
ensured between the exit window of the lamp and the matrix.
Silux was tested in all six cavity types, while Concise was
tested only in 0.5 mm and in 3.0-mm-deep cavities. For each
experimental condition, 10 fillings were investigated.
Group 2. - The cavity diameter was 4 mm and the cavity
depth 3.0 mm. Silux was applied with three different twophase techniques, as illustrated in Fig. 1. The first layer was
placed either with the surface parallel to the free surface of the
cavity (Fig. 1, A), obliquely in the apical area of the cavity
(Fig. 1, B), or obliquely in the coronal area (Fig. 1, C), and
was then polymerized. Approximately half the cavity was filled
with the first increment. For each of the three application techniques, the maximum marginal contraction gap of 10 fillings
was recorded.
The results for both groups were analyzed using a one-way
ANOVA and Duncan's multiple-range test (Bruning and Kintz,
1977).
Materials and methods.
Results.
J Dent Res 65(11):1319-1321, November, 1986
Introduction.
The method used has been described in detail in a previous
paper (Hansen, 1982). Briefly, the procedures were as follows:
The investigation was carried out using extracted human
teeth of the permanent dentition. After extraction, the teeth
were cleaned mechanically and stored in tap water at room
temperature for from one to 28 days. One of the root surfaces
was then ground flat on wet carborundum paper No. 220 (Struers
A/S, Denmark), and a cylindrical butt-joint cavity was prepared in the ground dentin surface (the dimensions of the cavities are explained later). Ten minutes after polymerization, a
standardized method of gentle wet-grinding and polishing was
used to remove approximately 0.1 mm of the surface of the
dentin and filling. The width of the maximum marginal conReceived for publication April 1, 1986
Accepted for publication May 27, 1986
The results of this investigation are shown in Figs. 2 and 3,
where the solid circles represent Silux, and the open circles
represent Concise.
Group 1. - Neither restorative resin showed a wider marginal contraction gap, measured 0.1 mm below the original
free surface of the filling, when the cavity depth was increased
from 0.5 to 3.0 mm (Fig. 2). The gap was slightly reduced
from 9.5 pum to 8.2 pum (Silux) and from 7.3 pum to 6.6 pum
(Concise). The statistical analysis showed that the width of the
maximum marginal contraction gap (MG), measured 0.1 mm
below the original free surface of the filling, was independent
of the cavity depth (Silux: P = 0.54; Concise: P = 0.43).
Group 2. - No difference was found between 3.0-mm-deep
cavities filled with a bulk technique and similar cavities filled
with a two-phase technique where the surface of the first layer
was parallel to the free surface of the cavity (Fig. 1, A). The
maximum marginal contraction gap was 8.2 pum (bulk tech-
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1319
1320
HANSEN
J Dent Res November 1986
Fig. 1 Two-phase application
techniques tested. A = Surface of
first layer parallel to the free surface of the cavity. B = First layer
in the apical area of the cavity. C
= First layer in the coronal area of
the cavity. * = apical area.
B
A
MGA
pm
C
nique) and 8.9 pum ("parallel" two-phase technique). The two
"oblique" techniques (Fig. 1, B and C) both resulted in a
statistically-significant reduction of the marginal contraction
gap, independent of the location of the first increment. The
12
reduction was in the order of 25%. The results of group 2 are
shown in Fig. 3, and the statistical analysis is shown in the
Table.
General findings. - The largest polymerization contraction
was nearly always found in the gingival area of the cavities;
only 11% of the fillings had the widest contraction gap in the
coronal region, while the frequency in the gingival region was
51%.
8
4
Discussion.
0.5
1.0
1.5
2.0
2.5
3.0 D mm
Fig. 2- Maximum marginal contraction gap (MG) in relation to cavity
depth (D). * = Silux. 0 = Concise. T-bar = one standard deviation.
MG
1m
12
The present investigation has shown that, for two resins, the
cavity depth does not influence the maximum marginal contraction gap (MG) in butt-joint dentin cavities. The marginal
gap, measured 0.1 mm below the original free surfaces of the
fillings, was not increased even though the volume of the fillings was increased by six times, in the 3.0-mm-deep cavities,
as compared with the 0.5-mm-deep cavities (Fig. 2). It could
be argued that the polymerization of Silux was significantly
reduced in the deeper part of the cavity, because of the reduced
conversion of the light-activated resin, and that this could be
the reason for the unchanged contraction. However, the fact
that the same phenomenon was found with the chemicallyactivated Concise ruled out this possibility.
The lack of a relation between cavity depth and marginal
adaptation can be explained by one of the results found in a
previous analysis of marginal adaptation of restorative resins
in dentin cavities (Hansen and Asmussen, 1985b). In that paper, five variables were analyzed: area of the cavity walls, the
total area of both cavity walls and cavity bottom, cavity depth,
area of the free surface of the filling, and cavity volume. The
best explanation for the "linearity" between the maximum
marginal contraction gap (MG), measured 0.1 mm below the
original free surface of the filling, and one or more of the five
8 _
4
TABLE
DUNCAN'S MULTIPLE-RANGE TEST
A
B
C
A
B
C
D
Fig. 3 Maximum marginal contraction gap (MG) in relation to different two-phase application techniques. A
Surface of the first layer
parallel to the free surface of the cavity. B First layer in the apical area
of the cavity. C = First layer in the coronal area of the cavity. D = Bulk
technique. (See also Fig. 1). T-bar one standard deviation.
=
=
=
A
B
C
**
**
-
NS
D.
NS
**
*
Statistical analysis of differences in maximum marginal contraction gap.
A, B, and C = different two-phase application techniques (see Fig. 1).
D = bulk technique.
NS = P>0.05.
* = P<O.05.
** P<0.01.
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MARGINAL ADAPTATION OF RESINS IN DENTIN CAVITIES
Vol. 65 No. 11
variables was found with MG = a + b-V/A, where V is the
cavity volume and A is the area of the cavity walls. The correlation coefficient was 0.935, i.e., 87% of the variation of
the marginal contraction gap could be explained by variations
in the V/A ratio.
In cylindrical butt-joint cavities, the ratio V/A is a constant,
when the cavity diameter is constant, no matter how deep the
cavity, because
V
A
Trr2h
2Trh
r
2
1321
gap from 8 to 6 Rxm (Fig. 3) may seem of minor importance,
because the gap is still unacceptable. However, a reduced contraction gap improves the conditions both for dentin-bonding
agents (Hansen, 1984, 1986; Munksgaard et al., 1984; Hansen
and Asmussen, 1985a) and for the possibility of a faster closure
of the contraction gap by later hygroscopic expansion of the
restorative resin (Hansen and Asmussen, 1985a).
REFERENCES
aide.,
r
MG = a + b-V/A = a + b2-2
This means that the polymerization contraction close to the
free surface of the filling is independent of the cavity depth,
as was actually found in the present investigation. It also means
that the contraction gap will be increased if the cavity diameter
r
is enlarged, because V/A = 2 . The relationship between MG
and cavity diameter is in accordance with earlier findings
(Munksgaard et al., 1984; Hansen and Asmussen, 1985a; Hansen, 1986). This relationship is independent of the cavosurface
angle, as well as whether the free surface of the filling is
circular, bean-shaped, rectangular, triangular, or oval (Hansen
and Asmussen, 1985a).
Rupp (1979) advocated the use of an incremental technique,
but the present results show that such a technique will have no
reducing effect on the marginal contraction gap in dentin cavities if the applied layer results only in a reduction of the cavity
depth (Fig. 1, A). In order to reduce the V/A ratio, one should
use "oblique" layers (Fig. 1, B and C), which results in a
significant reduction of the marginal contraction. If the cavity
is filled in this manner, the original cavity bottom will become
part of the cavity walls, reducing the V/A ratio and, in so
doing, reducing the marginal contraction gap (Fig. 3).
in accordance with previous results (Hansen, 1982), the largest
contraction was most often found in the apical area of the
cavity, also when using techniques B and C. The rationale for
testing two different oblique techniques was that placing the
first increment in the coronal area would result in a small
residual cavity in the apical area, where the largest contraction
was most often found. The hypothesis was that this method
would result in a more pronounced reduction of the apical
contraction than if the first increment were placed apically, but
no statistically-significant difference for marginal gap width
was found betweeli the two oblique techniques (Fig. 3 and
Table).
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