Journal of Advanced Research (Mar 2020)

Nanoscale chemical and mechanical heterogeneity of human dentin characterized by AFM-IR and bimodal AFM

  • Lijia Huang,
  • Xiaoyue Zhang,
  • Jian Shao,
  • Ziyu Zhou,
  • Yanan Chen,
  • Xiaoli Hu

Journal volume & issue
Vol. 22
pp. 163 – 171

Abstract

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Human dentin, as an important calcified tissue in the body, plays significant roles in withstanding masticatory forces and has a complex hierarchical organization. Understanding the composition and ultrastructure of dentin is critical for elucidating mechanisms of biomineralization under healthy and pathological states. Here, atomic force microscope infrared spectroscopy (AFM-IR) and AFM-based amplitude modulation-frequency modulation (AM-FM) techniques were utilized to detect the heterogeneity in chemical composition and mechanical properties between peritubular and intertubular dentin at the nanoscale. AFM-IR spectra collected from peritubular and intertubular dentin contained similar vibrational bands in the amide regions (I, II and III), suggesting that collagen may exist in both structures. A distinctive band at 1336 cm−1 indicative of SO stretching vibrations was detected only in peritubular dentin. AFM-IR imaging showed an uneven distribution of chemical components at different locations, confirming the heterogeneity of dentin. The Young’s modulus of peritubular dentin was higher, and was associated to a higher mineral content. This study demonstrated distinctive chemical and mechanical properties of peritubular dentin, implying the different development and mineralization processes between peritubular and intertubular dentin. AFM-IR is useful to provide compositional information on the heterogeneity of human dentin, helping to understand the mineral deposition mechanisms of dentin. Keywords: Infrared spectroscopy, Human dentin, Atomic force microscopy, Amplitude modulation, Frequency modulation, Young’s modulus