Polymeric nanocarriers doped with a parathyroid hormone-related protein enhances dentin apposition and nanohardness at the resin-dentin interface

Objectives: Restoring the original composition and properties of damaged tissues is aimed by regenerative medicine. The objective of the study was to assess remineralization and bonding capabilities of etched dentin treated with polymeric nanoparticles (NPs) functionalized with parathyroid hormone related proteins (PTHrP). Methods: Dentin etched surfaces were treated with NPs and PTHrP-NPs. The created bonded interfaces were stored for 24 h and further submitted to thermal, chemical and mechanical challenging. Interfaces were assessed through microtensile bond strength, nanohardness, Raman analysis, a fluorescent technique with a confocal laser scanning microscopy, and scanning electron microscopy. Results: Surfaces of dentin treated with PTHrP-NPs and load cycling or immersed in collagenase showed higher bond strength than the other groups. PTHrP promoted the highest nanohardness and phosphate peak intensity at the interface when load cycling was applied. Both porosity and nanoleakage were declined after PTHrP-NPs infiltration. Dentinal tubule walls and hybrid layer showed the strongest signals of xylenol orange stain. Conclusions: The highest dentin bonding efficacy was obtained in samples treated with PTHrP-NPs, as they inducted the greatest remineralization measured by nanoindentation and Raman analysis, high values of bond strength and advanced mineral deposition at the resin-dentin interface and tubules. PTHrP-NPs enabled sealing with scarce nanoleakage and porosity at the interface. Significance: Etched dentin infiltration with hydrophilic polymeric NPs functionalized with parathyroid hormone related proteins, poses an advance in regenerative dentistry, by developing therapeutic bioactivity.