Methods: Flat dentine
surfaces were prepared from twenty extracted non-carious human third molars.
Dentine surfaces were etched with 35% phosphoric acid for 15 s, rinsed and
blot-dried before bonding. The teeth were divided into four groups for bonding
using EWB or EWB with 1%, 2% and 3% CHX incorporated in the final step of
ethanol application. An experimental hydrophobic adhesive was prepared and
applied to dentine surface and light-cured. Composite build-ups were performed
using Filtek Z250 (3M ESPE). For microtensile bond strength (μTBS) evaluation, composite-dentine beams
were stressed to failure at a crosshead speed of 1 mm/min. The μTBS data
was analyzed using one-way ANOVA and Student-Newman-Keuls multiple comparison
test. Representative fractured beams from each group were prepared for
fractographic analysis under SEM.
Results: One-way ANOVA showed that the
incorporation of CHX in EWB significantly affected (P<0.05) the μTBS of
hydrophobic adhesive to dentine. No significant difference in μTBS was
observed among EWB (30.12 ± 9.83 MPa), EWB/1% CHX (30.24 ± 5.65 MPa) and
EWB/2% CHX (26.51 ± 7.34 MPa) groups. However, significant reduction (P<0.05)
in μTBS was observed in EWB/3% CHX group (25.19 ± 6.25 MPa). The majority of
failures in EWB, EWB/1% CHX and EWB/2% CHX groups adhesive and mixed failure
involving the adhesive and composite interface; the failure mode was largely
adhesive involving the adhesive-dentine interfaces.
Conclusions: The adjunctive application of 1% and 2% of chlorhexidine with ethanol wet-bonding has no
adverse effect on the immediate resin-dentine bond strength.