Figure 3.

Composition, orientation, and mechanical properties of the newly grown layer. (A) X-ray diffraction patterns of etched enamel and newly grown layer grown in chitosan, amelogenin-chitosan, and matrix metalloproteinase–20 (MMP-20) containing amelogenin-chitosan hydrogel. Diffraction peaks at 2θ = 25.8 (002), 2θ = 31.6 (211), and 2θ = 32.6 (300) can be readily indexed to hexagonal phase hydroxyapatite (JCPDS 09-0432). (B) Orientation degrees and (C) crystallinity of newly grown crystals formed in chitosan, amelogenin-chitosan, and amelogenin-chitosan hydrogel containing MMP-20. (D) Fourier transform infrared (FTIR) spectra of etched enamel, newly grown layer formed in chitosan, amelogenin-chitosan, and amelogenin-chitosan hydrogel with MMP-20. The characteristic bands for hydroxyapatite appeared at 1,000 to 1,120 cm⁻¹ (ν₃ [PO_4]), 916 cm⁻¹ (ν₁ [PO₄]), and 601 cm⁻¹ (ν₄ [PO₄]; Tao 2013). The characteristic peaks for chitosan were found at 1,735 cm⁻¹ (ν [C=O]), 1,458 cm⁻¹ (δ [C-H]), 1,418 cm⁻¹ (δ[O-H]), 1,365 cm⁻¹ (ν [C-H]), 1306 cm⁻¹ (ν [C-N]), 1,228 cm⁻¹ (ν [C-O]), 1,156 cm⁻¹ (ν [C-O-C]), 798 (δ[C-H]), 752 cm⁻¹ (δ[C-H]; Brugnerotto et al. 2001). (E, F) FTIR spectra of newly grown layer formed in amelogenin-chitosan hydrogel (blue) and MMP-20–amelogenin-chitosan hydrogel (red) representing the (B) Amide II and (V) Amide III regions. (G, H) Elastic modulus and hardness of healthy enamel, etched enamel, and repaired enamel treated with chitosan, amelogenin-chitosan, and amelogenin-chitosan hydrogel containing MMP-20. ***P < 0.001.