Effect of commercial desensitizing agents and eggshell derived nano-hydroxyapatite on bond strength of a universal adhesive to dentin

Background: The combined demineralized and remineralized dentin in hypersensitive teeth makes bonding to it enigmatic. Aim: The aim of this in vitro study is to determine the effect of three commercially available desensitizing agents and a naturally sourced, chicken eggshell-derived nano-hydroxyapatite (CES-nHAp) on the wettability and shear bond strength (SBS) of a universal adhesive to dentin. Material and Methods: Flat dentin surface was exposed in 218 extracted human molars, treated with 17% ethylenediaminetetraacetic acid (EDTA) for 5 min and patency of the tubules was confirmed in three samples under a field emission scanning electron microscope (FESEM). The remaining samples were randomly divided into 5 groups (n = 43) based on the 14-day desensitizing protocol as: group 1: no desensitizing treatment (control), group 2: casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), group 3: NovaMin (NM), group 4: Pro-Argin® (PA) and group 5: CES-nHAp. Tubule occlusion was analyzed under FESEM (n = 3). The contact angle (CA) of a universal adhesive resin (Single Bond Universal Adhesive, 3 M ESPE, MN, USA) to dentin was evaluated using a goniometer (n = 20). SBS was evaluated in a universal testing machine following resin composite build-up and the mode of fracture was analyzed using a stereomicroscope (n = 20). The data were statistically analyzed using Kruskal-Wallis test and Dunn's post-hoc test with Bonferroni correction (p<0.05). Results: PA (36.61±3.88) and CES-nHAp (35.33±3.75) treated dentin showed significantly higher CA compared to the other groups (p<0.05). CES-nHAp (16.52±7.22) treated dentin showed significantly higher SBS, compared to CPP-ACP (10.65±4.60, p<0.05). Conclusion: Within the limitations of this study, it can be concluded that desensitizers alter the wetting characteristics of the adhesive to dentin, with CPP-ACP and NM-based desensitizers showing the least influence on CA. The application of the desensitizer does not affect the self-etch bond strength of the universal adhesive used in the study.