To evaluate the shear bond strength of conventional (CF) and self-adhesive (SA) flowable composites to tooth enamel cyclic immersion in fluids with different acidities.
Method:
Both conventional (Tetric N Flow) and self-adhesive flowable composites (Fusio) were bonded to the enamel surfaces of extracted human teeth in three groups (n=20). In Groups I and III cylinders of CF and SA were built up against etched enamel surfaces utilizing single-component adhesive, while, in group II SA was built up directly against the non-etched enamel surfaces. Half the number of specimens in each group (n=10) were then subjected to cyclic immersion in Acetic acid, distilled water and sodium hydroxide solution with 30s dwelling and for 500 cycles. All specimens were then stressed to failure to determine the shear bond strength and bond rigidity. The mode of bond failure was also considered.
Result:
: pH cycling had no adverse effect on the bond strength of composite to tooth enamel (Tukey's comparison, P>0.05). No difference was noticed between the bond strength recorded for group I and III specimens before and after pH cycling (Tukey's comparison, P>0.05). However, the specimens of group II showed lower values of bond strength in comparison to those of groups I and III. Higher bond rigidity was obtained when etching and bonding is performed regardless the type of composite used. The adhesive bond failure was characteristic for the self-adhesive composite specimens in group II, while both admix and cohesive bond failures were recorded more frequently for the specimens of groups I and III.
Conclusion:
Short-term pH cycling seems to have no adverse effect on composite bond strength to tooth enamel. Using etching and bonding usually results in more rigid adhesive junction. The adhesive type of bond failure characterizes the bonding behavior of the self-adhesive composites to tooth enamel.