• Vanthana Sattabanasuk D.D.S., Ph.D. (Dental Science)
• Songsiri Pongburanakit D.D.S., Grad. Dip. in Clinical Science (Endodontology)

Objective To evaluate the effectiveness of antioxidants on bond strengths of a two-step self-etch
adhesive (Clearfil SE Bond) to pulp chamber dentine after bleaching with high concentration hydrogen
peroxide (Opalescence^® Boost).

Materials and methods Intact, non-carious, non-restored maxillary premolars were used. The roots
were cut and the crown was bucco-lingually sectioned through the pulp chamber. Taper diamond bur
was used to prepare the pulp chamber wall, imitating access opening step of the root canal therapy.
The teeth were assigned to 4 groups: (1) Control group which was not bleached, (2) Bleach with
Opalescence^® Boost, (3) Bleach followed by sodium ascorbate solution, and (4) Bleach followed by
catalase solution. Resin composite was afterward bonded to the treated dentine surface using Clearfil
SE Bond. After storage under 100% relative humidity at 37°C for 24 hours, all bonded teeth were
subjected to microshear bond strength test. The fractured surfaces were observed using an intra-oral
camera with imaging computer software. Representative dentine surfaces under each experimental
condition were examined using scanning electron microscope (SEM).

Results Upon statistical analyses, unbleach group presented highest shear bond strength to dentine
(p < 0.001), followed by the groups using sodium ascorbate solution and catalase solution (p < 0.001
and p ≤ 0.007, respectively). Bleach group showed significantly lower shear bond strength compared
with others (p ≤ 0.0035) and most specimens failed in bonding/resin composite layer. Moreover, 40 per
cent of the specimens in this group were also recorded as çpre-test failureé. Under SEM observations,
most of smear layer and smear plug were dissolved after treatment with primer of Clearfil SE Bond.
Collagen fibres were also clearly observed.

Conclusion Application of sodium ascorbate solution and catalase solution could improve the
bonding effectiveness of Clearfil SE Bond to pulp chamber dentine after bleaching with Opalescence^®
Boost, however not equal to the dentine that was not bleached. Sodium ascorbate solution showed
better result than catalase solution significantly.

(CU Dent J. 2012;35:79-92)