X-ray diffraction and IR spectroscopy investigation of synthesized and biogenic nanocrystalline hydroxyapatite

The results of the X-ray diffraction analysis (XRD) and optical (IR) investigations of hydroxyapatite (HAP) produced from the egg-shell of birds and biogenic HAP (a slice of tooth enamel) are presented. The synthesized material is a nanocrystalline hydroxyapatite with an average crystal size similar to 35 nm. The outer and inner sides of the tooth enamel slice include HAPs with a different structural organization. The inner side of the tooth slice containing HAP nanocrystals, with an average size of similar to 15 nm, demonstrates the most similarity with the synthesized material. Hydroxyapatite of the outer enamel consists of hydroxyapatite with a strong texture organization whose common elements, namely hexagonal prisms, are predominantly oriented along the [001] crystallographic direction. The IR spectra of the tooth enamel (in addition to fundamental HAP vibration modes) revealed the vibration modes of the collagen protein. The comparison of the characteristics of the synthesized and biogenic HAP show that synthesized HAP is a promising candidate for medical applications, e.g., for improving the adhesion properties of dental cement pastes.