Abstract

Purpose: Fluoride compounds have been reported to play a protective role in the host-derived enzymatic degradation of demineralized dentin matrices. The objective of this study was to evaluate the effect of fluoride pretreatment on the immediate and long-term microtensile bond strength (µTBS) of resin-dentin interfaces.

Materials and methods: Mid-coronal dentin surfaces of ninety-nine teeth were etched with 32%wt phosphoric acid and randomly assigned to pretreatment with NaF, KF or CaF2 solutions (6, 24 and 179 mM F content) for 30 s before the application of bonding agent (Scothbond Multi-Purpose, 3 M ESPE). No fluoride pretreatment and a commercially available bonding agent with KF (Excite F, Ivoclar Vivadent) were used as controls. After composite built-up, the specimens were sectioned into µTBS test beams, stored in artificial saliva at 37 °C for 24 h, 6 or 12 months and tested. Fracture types were evaluated under scanning electron microscope. The data were analyzed with ANOVA and Scheffe post-hoc tests (α = 0.05). Pearson Chi-Square test was used to compare the distribution of failure types.

Results: Fluoride compound, fluoride concentration and storage time showed significant effect on µTBS (p < 0.05). NaF, KF and Excite F groups showed higher µTBS than the control (p < 0.05). After 24 h, µTBS ranged between 35.26(±10.25) MPa in control to 54.65(±14.60) MPa in NaF 24 mM group (p < 0.05), and the bond strength of 6 and 24 mM F groups were also found higher than the control (p < 0.05). After 12 months, all F groups showed stable bond strength (p > 0.05), except CaF2 179 mM (p < 0.05). According to Chi-square test, fracture types were also significantly influenced from the test factors (p < 0.05).

Conclusions: NaF and KF treatment after acid-etching step of adhesive bonding procedures do not adversely influence the initial or long-term bond strength to dentin, and can improve the maintenance of bond strength durability.