Sixty human third molars free of caries and restorations
were collected and stored in normal saline. One
hundred and twenty standardized class II cavities
were prepared on the mesial and distal surfaces of
each tooth. Each cavity was prepared with a carbide
bur (# 245, SS White). For every five preparations,
a new bur was used. The final preparation showed
the following dimensions: 2.0 mm occlusal extension,
3.0 mm buccal-lingual extension. The gingival seat
was placed at the CEJ [Figure 1 and 2]. Each specimen
was mounted with the adjacent teeth for placement
of Tofflemire matrix which allowed building up of the
proximal wall.
All cavity surfaces were dried with oil free compressed
air followed by etching with 35% phosphoric acid for
15 seconds, rinsed with water for 15 seconds and
excess water was removed with the help of a tissue
paper, leaving a glistening hydrated surface. The
primer (Scotch Bond Multipurpose, 3M Espe) was
applied to etched enamel and dentin and gently dried
for 5 seconds. Then, the Scotch Bond Multipurpose
adhesive was applied to primed enamel and dentin
and light cured for 10 seconds. The specimens were
randomly divided into six groups.
In all the groups, each increment was cured for
40 seconds using the ramp curing mode (initial intensity
of 200 mW/cm2 and increasing over 600 mW/cm2 in
40 seconds). The thickness of the first increment was
0.5 mm and this increment was cured for an additional
20 seconds using conventional curing mode. The
thickness of each increment placed was confirmed
with the help of a graduated probe by measuring the
depth of the walls prior to and after the placement
of the composite. The rest of the cavity was filled
with the help of oblique layering technique, i.e. using
triangular or wedge shaped increments of 1.5 mm
thickness, which contacted only one opposing wall at
a time. The second and third increments were cured
for an additional 10 seconds. The curing was done
from the occlusal aspect with the tip of the curing unit
placed as close to the occlusal surface as possible.
Group (G1) was restored with the microhybrid resin
composite Z 100 (3M, Espe) using oblique layering
technique. Group 2 (G2) was restored with the
Packable/compactable resin composite Filtek P60
(3M Espe), using oblique layering technique. Group 3
(G3) was restored with a first increment of a flowable
resin composite, Filtek Flow (3M Espe), placed on the
cervical wall of the cavity in a thickness of 0.5 mm
and light cured for an additional 20 seconds using
the conventional curing mode. The rest of the cavity
was then restored with microhybrid resin composite
(Z100, 3M) using the oblique layering technique