Adjunctive use of an anti-oxidant agent to improve resistance of hybrid layers to degradation.

Objective: To determine the role of an anti-oxidant agent (ascorbic acid-AA) on resin-dentin bonds resistance to degradation of two adhesives.

Methods: Flat dentin surfaces from 48 human molars were bonded as per manufacturer's instructions with: a two-step etch-and-rinse self-priming adhesive (Single Bond-SB) and a two-step self-etch adhesive (Clearfil SE Bond-CSE). Half of the specimens were bonded with the same adhesives, but after the addition of 10% AA into their formulation. Resin composite build-ups were constructed incrementally and sectioned into resin-dentin beams (1.0mm(2)) that were stored under four conditions: (1) water immersion for 24h; (2) water immersion for 1 year; (3) water immersion for 4 years; and (4) chemical challenging (immersion in 10% NaOCl for 5 h). Beams were pulled to failure in tension at 0.5mm/min. Mean microtensile bond strength (MTBS) data were analysed with ANOVA and multiple comparisons tests (P<0.05). Analysis of debonded dentin beams was performed by scanning electron microscopy (SEM).

Results: After 24 h, SB and CSE performed equally, regardless of AA incorporation. Inclusion of AA on CSE formulation decreased MTBS following one-year water storage, but maintained SB bond strength values even after four years of water storage. NaOCl challenge diminished MTBS for both adhesives, but when AA was added to SB, this reduction was significantly lower.

Conclusions: The inclusion of AA on adhesive's formulation exerts a protective role on resin-dentin bonds resistance to degradation when SB is used. Bonding durability of CSE may be compromised by the addition of sodium ascorbate.