Examining the influence of parathyroid hormone-doped nanoparticles on resin-dentin interface strength and composition

This study aims to determine the remineralization capacity of etched dentin treated with polymeric nanoparticles (NPs) functionalized with parathyroid hormone (PTH) (PTH-NPs).

Dentin etched surfaces were treated with NPs and PTH-NPs. Treated interfaces were 24 h stored and, then, mechanically or thermally loaded. Interfaces were assessed through modulus of Young, Raman analysis and Masson's trichrome staining microscopy.

Specimens treated with PTH-NPs infiltration which were load cycled attained the highest modulus of Young. Remineralization throughout the total resin-dentin interface, referred to both phosphate and carbonate ions was unveiled in presence of PTH and dynamic loading, forming peritubular and intertubular dentin. The absence of NPs at the interface conditioned a scarce remineralization. After thermocycling, phosphate remineralization diminished at the interface in all groups, and carbonate only increased in the control group. Load cycling produced a higher minerals content and a major collagen crosslinking, contributing to generally augment both the mineral to matrix ratio and crystallinity.

PTH-NPs provoked a higher modulus of Young and a lower unprotected collagen web after conditioning and further resin infiltration, in load cycled samples. After dynamic load cycling, amorphous mineral was lower at the resin dentin interface, and crystallinity relative to phosphate was also greater after thermocycling at both hybrid layer and bottom of hybrid layer in case of PTH-NPs infiltration.

Parathyroid hormone dentin infiltration, after phosphoric acid conditioning, has facilitated the reparative dentin formation at the resin-dentin interface, based on the nucleation of a more mature and soluble hydroxyapatite which facilitated remineralization.