Investigation of the effect of Tideglusib on the hydroxyapatite formation, crystallinity and elasticity of conditioned resin-dentin interfaces

Abstract

Objectives: To investigate the effect of dentin infiltration with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs) on hydroxyapatite formation, crystallinity and elasticity of conditioned resin-dentin interfaces. Methods: Dentin conditioned surfaces were infiltrated with NPs or TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nanoindentation to determine the modulus of elasticity, X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-filed imaging. Results: TDg-NPs provoked peaks narrowing after the diffraction-intensity analysis that corresponded with high crystallinity, with an increased modulus of Young after load cycling in comparison with the samples treated with undoped NPs. New minerals, in the group of TDg-NPs, showed the greatest both deviation of line profile from perfect crystal diffraction and dimension of the lattice strain, i.e., crystallite, grain size and microstrain and 002 plane-texture. The new minerals generated after TDg-NPs application and mechanical loading followed a well defined lineation. Undoped NPs mostly produced small hydroxyapatite crystallites, non crystalline or amorphous in nature with poor maturity. Conclusions: Tideglusib promoted the precipitation of hydroxyapatite, as a major crystalline phase, at the intrafibrillar compartment of the collagen fibrils, enabling functional mineralization. TDg-NPs facilitated nucleation of crystals randomly oriented, showing less structural variation in angles and distances that improved crystallographic relative order of atoms and maturity. Nanocrystals inducted by TDg-NPs were hexagonal prisms of submicron size. Thermal challenging of dentin treated with TDg-NPs have provoked a decrease of functional mineralization and crystallinity, associated to immature hydroxyapatite. Clinical significance: New polycrystalline lattice formation generated after TDg-NPs infiltration may become correlated with high mechanical performance. This association can be inferred from the superior crystallinity that was obtained in presence of tideglusib. Immature crystallites formed in dentin treated with undoped NPs will account for a high remineralizing activity.