The effect of kaempferol on the dentin bonding stability through matrix metalloproteinases inhibition and collagen crosslink in dentin biomodification

Abstract

Background/purpose: Naturally derived collagen crosslinkers with matrix metalloproteinases (MMPs) inhibitory activity for dentin bonding have been previously studied. One of these crosslinkers is flavonoids. The purpose of this study was to investigate whether dentin pretreatment with kaempferol (KEM), one of the flavonoids, enhances dentin bond stability and nanoleakage at the dentin-resin interface through MMPs inhibition and collagen crosslinking.

Materials and methods: The experimental KEM-containing solution was used to pretreat demineralized dentin prior to the application of a universal adhesive. KEM is a natural flavonoid and those which did not take the experimental solution served as the control group (CON). Microtensile bond strength (μTBS) and nanoleakage tests were conducted before and after the thermocycling to evaluate the influence of KEM on dentin bond strength. The MMPs inhibition activity of KEM was analyzed via MMPs zymography using a confocal microscopy. Fourier-transform infrared (FTIR) spectroscopy was used to demonstrate that KEM inhibits MMPs and enhances collagen crosslinking.

Results: The μTBS values of KEM group exhibited a higher bond strength after thermocycling. At the resin-dentin interface, the KEM group did not exhibit any signs of nanoleakage after thermocycling. Furthermore, MMPs zymography confirmed that there was a relatively low activity of MMPs in the presence of KEM. In FTIR analysis, the PO₄ peak representing the cross-link between dentin and collagen was significantly higher in the KEM group.

Conclusion: Our findings suggest that pretreatment with KEM enhances the dentin bonding stability at the resin-dentin interface by acting as a collagen crosslinker and MMPs inhibitor.

Keywords: Collagen crosslink; Kaempferol; Matrix metalloproteinase (MMP) inhibition; Resin-dentin bonding.

Fig. 1

Representative scanning electron microscopy images of the resin-dentin bonded interfaces assayed at 24 h and after thermocycling (TC). A) Control group at 24 h, B) Control group after thermocycling, C) KEM group at 24 h, D) KEM group after thermocycling. The arrows represent noticeable silver infiltration into the hybrid layer. The silver uptake was shown only in the thermocycled control (CON) group. C: composite resin, D: dentin.

Fig. 2

The confocal laser scanning microscopy (CLSM) images of the matrix metalloproteinases (MMPs) zymography at the bonded resin-dentin interfaces. (A, B, C) The control (CON) group (D, E, F) and the Kaempferol (KEM) group. Each scale bar at the bottom of the image represents 50 ㎛.

Fig. 3

FTIR spectra of samples. a) 4000-400 cm⁻¹, and b) 2000-400 cm⁻¹. The PO₄ related peaks (1029, 860 and 557 cm⁻¹) representing collagen cross-linking are sharper and show stronger intensity in the KEM sample.