The purpose of this study was to evaluate the effect of different etching time on the
shear bond strength and adaptibility of composite to enamel and dentin when used
one-bottle adhesive Prime & BondTM 2.0. The proximal and occlusal
surfaces of 88 extracted human molars were ground to expose enamel(n=44) and
dentin(=44) using diamond wheel saw. Teeth were randomly assigned to four test
groups(n=110 and received the following treatments : Control group were conditioned
with 36% phosphoric acid for 20 sec. according to the manufacturer's directions.
Experimental 10 sec. group, 30 sec. group and 60 sec. group were conditioned with 36%
phosphoric acid for 10 sec., 30 sec. and 60 sec., respectively. Teeth were rinsed and
dried for 2 sec. Prime & BondTM 2.0 were applied according to the
manufacturer's directions and SpectrumTM TPH composite resins were
bonded to enamel and dentin surfaces. All specimens were stored in distilled water for
24 hours. Eighty specimens were sheared in a Universal Testing Machine with a
crosshead speed of 5mm/minute. One way ANOVA and LSD test were used for
statistical analysis of the data.
Failure modes of all specimens after shear bond strength test were examined and
listed. Also, representive postfracture modes and eight specimens were examined under
scanning electron microscope.
The results of this study were as follows: 1. The shear bond strength to enamel was
the highest value in 30 sec. group (20.68±8.54MPa) and the lowest value in 10 sec.
group (14.92±6.07MPa), so there was significant difference of shear bond strength
between two groups (p<0.05). But there was no significant difference among other
groups (p>0.05). With longer etching time to enamel from 10 sec. to 30 sec., higher the
shear bond strength was obtained, but the shear bond strength was decreased at 60 sec.
etching time.
2. The shear bond strength to dentin was the highest value in control group (13.08±
6.25MPa) and the lowest value in 60 sec. group (9.47±3.35MPa), but there was no
significant difference among the all groups (p>0.05). etching time over 20 sec. decreased
the shear bond strength to dentin.
3. In SEM observation, the enamel and resin interfaces were showed close adaptation
with no relation to etching time of enamel. And the dentin and resin interfaces were
showed close adaptation at 20 sec. and 30 sec. etching time, but showed some gaps at
10 sec. and 60 sec. etching time.
Accordingly, these results indicated that a appropriate etching time in Prime &
BondTM 2.0 was required to be 30 sec. in enamel and 20 sec. in dentin
for the high shear bond strength and good adaptation between the composite resin and
tooth substance.
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