Abstract
The biomimetic remineralization of collagen fibrils has increased interest in restoring the demineralized dentine generated by dental caries. Carboxyl-terminated polyamidoamine dendrimers (PAMAM-COOH), hyperbranched polymeric macromolecules, can act as non-collagenous proteins to induce biomimetic remineralization on a dentine organic matrix. However, in vivo remineralization is an extremely time-consuming process; before complete remineralization, demineralized dentine collagen fibrils are susceptible to degradation by host-derived matrix metalloproteinases (MMPs). Therefore, we examined the effect of fourth-generation PAMAM-COOH (G4-PAMAM-COOH) on the collagenolytic activities of endogenous MMPs, the interaction between G4-PAMAM-COOH and demineralized dentine collagen and the influence of G4-PAMAM-COOH pre-treatment on resin–dentine bonding. G4-PAMAN-COOH not only inhibited exogenous soluble rhMMP9 but also hampered the proteolytic activities of dentine collagen-bound MMPs. Cooperated with the results of G4-PAMAM-COOH absorption and desorption, FTIR spectroscopy provided evidence for the exclusive electrostatic interaction rather than hydrogen or covalent bonding between G4-PAMAM-COOH and dentine collagen. Furthermore, G4-PAMAM-COOH pre-treatment showed no damage to resin–dentine bonding because it did not significantly decrease the elastic modulus of the demineralized dentine, degree of conversion, penetration of the adhesive into the dentinal tubules or ultimate tensile strength. Thus, G4-PAMAM-COOH can effectively inactivate MMPs, retard the enzymolysis of collagen by MMPs and scarcely influence the application of resin–dentine bonding.
Highlights
Resin adhesive restoration is a popular preferred procedure for repairing dental tissue defects due to caries and uses an etchant or acidic monomers to expose collagen fibres for the purpose of permitting adhesive resin monomers to infiltrate dentine and form a resin–dentine hybrid layer (HL)
The effect of G4-Polyamidoamine dendrimers (PAMAM)-COOH on soluble rhMMP9 is shown in figure 1
Over 90% soluble rhMMP9 was inhibited by different concentrations of G4-PAMAM-COOH, ranging from 1 to 10 mg ml−1
Summary
Resin adhesive restoration is a popular preferred procedure for repairing dental tissue defects due to caries and uses an etchant or acidic monomers to expose collagen fibres for the purpose of permitting adhesive resin monomers to infiltrate dentine and form a resin–dentine hybrid layer (HL). Due to incomplete resin infiltration, the mineral-depleted, resin-sparse, water-rich collagen at the bottom of the HL is susceptible to deterioration during prolonged function, adversely affecting the durability of the resin–dentine bonding. Similar to collagen cross-linkers, the main drawback of non-specific inhibitors to inactivate MMPs and cysteine cathepsins is the residue of the water-rich, resin-sparse and mineral-depleted collagen matrix within the HL. Data reported in the literature suggested that biomimetic remineralization can restore water-filled, resin-sparse regions within the HL to intact mineralized dentine characterized by excellent mechanical properties and fossilize endogenous collagenolytic enzymes [20,21,22], resulting in enhanced resistance of collagen against fatigue rupture and degradation. The implementation of biomimetic remineralization is closely dependent on three elements, involving non-collagenous proteins (NCPs), collagen scaffold and extraneous minerals (calcium and phosphorus)
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