Prodelphinidins enhance dentin matrix properties and promote adhesion to methacrylate resin.

Objective: Investigate the bioactivity and stability of Rhodiola rosea (RR) fractions as a natural source of prodelphinidin gallate (PDg) on dentin collagen via analysis of the viscoelastic and resin-dentin adhesive properties of the dentin matrix.

Methods: The biomimicry and stability of RR subfractions (F1, F2, F3 and F4) with collagen were determined by dynamic mechanical analysis (DMA). DMA used a strain sweep method to assess the dentin matrix viscoelastic properties [storage (E'), loss (E"), and complex (E*) moduli and tan δ] after treatment, 7-, 30- and 90-days of storage in simulated body fluids (SBF). Resin-dentin interface properties were assessed after 1 and 90-days in SBF by microtensile bond strength test and confocal laser scanning microscopy. Data were analyzed using two and one-way ANOVA and post-hoc tests (α = 0.05).

Results: RR fractions increased dentin matrix complex (96 - 69 MPa) and storage (95 - 68 MPa) moduli, compared to the control (∼9 MPa) in the ranking order: F2 ≥ F3 = F1 = F4 > control (p < 0.001). Treatment did not affect tan δ values. After 30- and 90-days, RR-treated dentin E*, E' and tan δ decreased (p < 0.001). F2 fraction yielded the highest microtensile bond strength (43.9 MPa), compared to F1, F4 (35.9 - 31.7 MPa), and control (29 MPa). RR-treated interfaces mediated stable surface modifications and enhanced collagen-methacrylate resin interactions at the bioadhesive interface.

Significance: Prodelphinidin gallates from RR are potent and reasonably stable biomimetic agents to dentin. Higher potency of F2 fraction with the dentin matrix and the adhesive interface is associated with a degree of polymerization of 2-3 and gallo(yl) motifs.