Interfacial Characterization of Dentin Conditioned with Chitosan Hydroxyapatite Precursor Nanocomplexes Using Time-of-flight Secondary Ion Mass Spectrometry

IntroductionThe purpose of this study was to evaluate the effect of chitosan-hydroxyapatite precursor (C-HA) nanocomplex conditioning on the chemical modifications at the tricalcium silicate sealer-dentin interface using time-of-flight secondary ion mass spectrometry.MethodsDentin slabs from human premolar root dentin were prepared, demineralized, and randomly distributed between control and C-HA nanocomplex conditioned groups. Tricalcium silicate sealer was applied, and the slabs were allowed to set in 100% humidity for 10 days. The cross-sectional area was exposed, and the sealer-dentin interface was characterized for chemical/ultrastructural evaluation with time-of-flight secondary ion mass spectrometry and transmission electron microscopy, respectively.ResultsChemical analysis revealed the presence of an ion-rich layer constituted of abundant phosphates (PO₂^?, PO₃^?, and PO₄^?), hydroxide (OH^?), and chitosan fragments (C₂H₄NO^?, C₃H₄NO₂^?, C₂H₅O₂⁺, C₂H₆NO⁺, C₄H₆NO₂⁺, C₅H₆NO⁺, and C₅H₅O₂⁺) on the dentin surface at the sealer-dentin interface and subsurface dentin after conditioning with C-HA nanocomplexes. In contrast, a decreased interfacial presence of calcium (Ca⁺) and calcium phosphates (CaPO₂⁺, CaPO₃⁺, CaPO₄⁺, and Ca₂PO₃⁺) and the absence of phosphate fragments in the control were noted. Ultrastructural evaluation showed an interfacial layer (<1 μm) with interrupted mineral aggregates in the controls as opposed to a continuous (5 μm) mineral layer formation on the conditioned dentin.ConclusionsC-HA nanocomplex conditioning of dentin before tricalcium silicate sealer application resulted in a chemically modified dentin substrate with an ion-rich layer consisting of phosphate, calcium, calcium phosphates, and chitosan that chemically modified the dentin surface/subsurface.