الفهرس 
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Abstract
The present study was designed to evaluate in vitro the shear bond
strength of a multi-mode adhesive resin cement when bonded to enamel and
dentin in different application modes and to assess the morphological
characterization of the tooth/adhesive interface microscopically.
A total of 40 sound extracted human permanent anterior teeth and 40
extracted molar teeth were used in this study. Anterior teeth had their labial
surface ground to obtain flat enamel surfaces and embedded into the acrylic
resin with their labial surfaces facing upwards, Molar teeth had their occlusal
surfaces ground to expose flat dentinal surfaces and they were embedded into
the acrylic resin with their occlusal surface facing upwards. Each substrate
specimens were then divided into four groups of 10 specimens each according
to resin cement applied: RelyX Ultimate in total-etch mode, RelyX Ultimate in
self-etch mode, Variolink II total-etch resin cement and Multilink Automix
self-etch resin cement. A thin walled plastic tube, was placed over the surfaces
and the resin cements were built up following manufacturer’s instructions.
Specimens were secured to the universal testing machine and the shear
load was applied at a constant cross-head speed of 0.5mm/min, then shear
bond strength was calculated in MPa. The fractured surfaces were observed
with a stereomicroscope for assessment of the ARI which has a range between
0 and 3 which is assigned according to the following criteria; 0 = No adhesive
left on the tooth, 1 = Less than half of the adhesive left on the tooth, 2 = More
than half of the adhesive left on the tooth, 3 = All the adhesive left on the
tooth. Three specimens from each group after shear bond strength test were
sectioned, air-dried, gold-sputtered and then observed by SEM. The resintooth
interfaces were photomicrographed to be evaluated.
The results were recorded, tabulated, and statistically analyzed.
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When bonded to enamel, the studied cements showed a statistically
significant difference with P<0.001. RelyX Ultimate in total-etch mode and
variolink II showed the highest mean values. On dentin, studied cements
showed non-significant difference with P=0.053. An etching step prior to RelyX
Ultimate cement yielded higher shear bond strength values on enamel and
dentin. The difference in mean values of ARI scores between studied cements
were statistically significant with P<0.001 on enamel and P=0.022 on dentin.
There was also a significant positive correlation between shear bond strength
with ARI scores. Interfacial morphology of etched specimens showed thin
resin tags penetrating into enamel. On dentin RelyX Ultimate in total-etch
mode showed better interface morphology and improved tag length compared
to respective self-etch counterpart.
It was concluded that the multi-mode adhesive resin cement (RelyX
Ultimate) has to be applied in the total-etch mode when bonded to enamel,
while for dentin both self-etch and total-etch modes could be applied with
improved penetration pattern in the total-etch mode. Higher shear bond
strength values did correlate with higher ARI scores and the length of resin
tags formed by total-etch adhesives seems not to play an important role in
determining bond strengt