Bond Strength of a Universal-Adhesive to Bleached & Desensitized Enamel

Objectives: To assess the influence of different bleaching methods and desensitizing agents over the bond strength of a universal adhesive system to enamel.
Methods: Ninty non-carious mandibular incisor enamel surfaces were selected and ground flat with 600, 1000, 2500 and 4000 grits of SiC papers, then randomly divided into nine experimental groups (n=10): (1) No bleaching agent and desensitizer were applied (control group), (2) Office-Bleaching (Total Blanc Office Dental Whitening 35% Hydrogen-Peroxide/DFL), (3) Office-Bleaching + Desensitizing Agent (DA) (Potassium nitrate&Fluoride/UltraEZ, Ultradent), (4) Office-Bleaching + DA (Hydroxyapatite & Potassium nitrate/ExSense, Cavex), (5) Office-Bleaching + DA (Hydroxyapatite/Teethmate Desensitizer, Kuraray), (6) Home-Bleaching (Total Blanc Home Dental Whitening 16% Carbamid-Peroxide/DFL), (7) Home-Bleaching + (DA) (Potassium nitrate&Fluoride/UltraEZ, Ultradent), (8) Home-Bleaching + DA (Hydroxyapatite & Potassium nitrate/ExSense, Cavex), (9) Home-Bleaching + DA (Hydroxyapatite/Teethmate Desensitizer, Kuraray). Composite cylinders (Clearfil MajestyES-2 Premium A1, Kuraray) were bonded using a jig with universal adhesive (Clearfil Universal Bond, Kuraray) regard to total-etch procedure after 14 days. After storing the specimens in distilled water 24 hours, the shear bond strengths (SBS) (MPa) were examined using a universal testing device at a crosshead speed of 1 mm/min. Failure mode distribution was also evaluated. Two-way ANOVA test, with a significance level of 5%, was used for data analysis.
Results: The highest mean SBS value was observed in Group 4 (25.70±7.29) whereas the lowest bond strength value was observed in Group 9 (7.01±4.04) Group 4 showed significantly higher SBS than the other groups (p<0.05). The SBS of universal adhesive to the enamel was not affected by the bleaching methods (p>0.05). The failure modes were mainly adhesive for all of the groups.
Conclusions: Application of desensitizers after bleaching could influence the bond strength of universal adhesive to enamel.