Effect of sodium ascorbate on the shear bond strength of orthodontic brackets to bleached enamel using universal dental adhesive

Abstract

Background: The aim of this study was to investigate the effect of bleaching agent, sodium ascorbate
as an antioxidant, and delay time on the shear bond strength (SBS) of orthodontic brackets to
enamel using Transbond XT and universal adhesive.
Materials and Methods: In this in vitro experimental study, 80 extracted maxillary
premolars without any defect or decay were randomly divided into eight groups of 1: no
bleaching + Transbond XT (NB/TX) bonding agent, 2: no bleaching + All‑Bond Universal (NB/AB),
3: bleaching + Transbond XT (B/TX), 4: bleaching + All‑Bond Universal (B/AB), 5: bleaching + sodium
ascorbate + Transbond XT (B/SA/TX), 6: bleaching + sodium ascorbate + All‑Bond Universal
(B/SA/AB), 7: bleaching + Transbond XT after a 3‑week delay (B/3W/TX), and 8: bleaching + All‑Bond
Universal after a 3‑week delay (B/3W/AB). After thermocycling (1000 cycles, 5–55°C), the SBS was
measured, and the adhesive remnant index scores were determined to assess the failure mode.
Data were analyzed by one‑way analysis of variance, Tamhane’s post hoc test, Kruskal–Wallis, and
Mann–Whitney U‑test at the significance level of P < 0.05.
Results: The mean SBS range was 5.5–29.78 MPa. The highest SBS values were related to
Group 2 (NB/AB) which were significantly higher than all groups (P < 0.05) and the lowest values
were observed in Group 5 (B/SA/TX) which were significantly lower than all groups except
Group 3 (B/TX) (P < 0.05).
Conclusion: Bleaching with 40% hydrogen peroxide significantly decreased the SBS of orthodontic
brackets, and 10% sodium ascorbate could not reverse the adverse effect of bleaching on SBS.
Delaying the bonding procedure by 3 weeks using Universal adhesive considerably decreased
the adverse effect of bleaching on SBS and increased the SBS to a clinically acceptable level for
orthodontic treatment.
Key Words: Antioxidant, dental bonding, orthodontic bracket, shear strength, tooth bleaching