Introduction: Resin cements are used for cementation of indirect restorations. A high-quality adhesion to tooth structure is primordial for the
success of indirect cemented restorations.
Objectives: Were to assess the shear bond strength of RelyX ultimate adhesive resin cement to both enamel and dentin when used in different
application modes (self-etch and total-etch) and to study resin-tooth interfaces using SEM.
Materials and methods: 40 enamel specimens and 40 dentin specimens were used in this study. Each substrate specimens were randomly
divided into four groups of 10 specimens each according to resin cement applied: Enamel groups: Group A1: RelyX ultimate as total-etch; Group < br />A2: RelyX ultimate as self-etch; Group A3: Variolink II; Group A4: Multilink automix. Dentin groups: Group B1: RelyX ultimate as total-etch;
Group B2: RelyX ultimate as self-etch; Group B3: Variolink II; Group B4: Multilink automix. Resin cements were built over the surfaces following
manufacturer's instructions in a plastic tube. All specimens were thermocycled (500 cycles, 5°/55°C, 15 sec dwell time) then shear bond strength was
measured in MPa and data were analyzed using F-test (ANOVA) and Post Hoc test. Three specimens from each group were further sectioned, gold
sputtered and evaluated under SEM.
Results: All enamel groups showed a statistically significant difference for shear bond strength with P value of 35.60 MPa. While for dentin, there was no statistically significant differences among groups with P=0.053. Interfacial morphology of
RelyX ultimate in total-etch mode showed better interface morphology and improved tag length compared to respective self-etch counterpart
Conclusions: An etching step prior to multi-mode adhesive resin cement increased its bond strength values and improved its penetration pattern to
both enamel and dentin, also length of resin tags formed by total-etch adhesives seems not to play an important role in determining bond strength