Efficacy of amelogenin-chitosan hydrogel in biomimetic repair of human enamel in pH-cycling systems

Abstract

Amelogenin-chitosan (CS-AMEL) hydrogel has shown great potential for the prevention, restoration, and treatment of defective enamel. As a step prior to clinical trials, this study aimed to examine the efficacy of CS-AMEL hydrogel in biomimetic repair of human enamel with erosive or caries-like lesions in pH-cycling systems. Two models for enamel defects, erosion and early caries, were addressed in this study. Two pH-cycling systems were designed to simulate the daily cariogenic challenge as well as the nocturnal pH conditions in the oral cavity. After pH cycling and treatment with CS-AMEL hydrogel, a synthetic layer composed of oriented apatite crystals was formed on the eroded enamel surface. CS-AMEL repaired the artificial incipient caries by re-growing oriented crystals and reducing the depth of the lesions by up to 70% in the pH-cycling systems. The results clearly demonstrate that the CS-AMEL hydrogel is effective at the restoration of erosive and carious lesions under pH-cycling conditions.

Keywords: Amelogenin-chitosan hydrogel; Early carious lesion; Enamel biomimetic; Enamel erosion; pH-cycling.

Figure 1

Schematic illustration of the pH-cycling models

Figure 2

(A) SEM image of enamel etched with 30% H₃PO₄ for 30 seconds. (B–C) SEM images of enamel blocks after 5 days of cycle I (B) without and (C) with CS-AMEL hydrogel treatment. Insets show the images at a higher magnification. (D) XRD spectra of etched enamel (black) and repaired enamel blocks after 5 days of cycle I (blue) with and (red) without CS-AMEL hydrogel treatment.

Figure 3

Representative fluorescent images of cross-sections of (A) healthy enamel and (C) demineralized enamel. Inset: photograph of a demineralized enamel block showing a white spot lesion on the tooth sample (red square). XRD spectra of (B) healthy enamel surface and (D) enamel surface with the caries-like lesions.

Figure 4

Representative fluorescent images of cross-sections of enamel blocks after 7 days of cycle I without (A) and with (B) CS-AMEL hydrogel treatment

Figure 5

XRD spectrum of enamel surface after 7 days of cycle I with CS-AMEL hydrogel treatment

Figure 6

Representative fluorescent images of cross-sections of enamel blocks after 7 days of cycle II without (top) and with (bottom) CS-AMEL hydrogel treatment. Rectangle in (A) represents the selected area corresponding to (B).