Vibrational algorithms for quantitative crystallographic analyses of hydroxyapatite-based biomaterials: I, theoretical foundations

Abstract

The Raman spectroscopic method has quantitatively been applied to the analysis of local crystallographic orientation in both single-crystal hydroxyapatite and human teeth. Raman selection rules for all the vibrational modes of the hexagonal structure were expanded into explicit functions of Euler angles in space and six Raman tensor elements (RTE). A theoretical treatment has also been put forward according to the orientation distribution function (ODF) formalism, which allows one to resolve the statistical orientation patterns of the nm-sized hydroxyapatite crystallite comprised in the Raman microprobe. Close-form solutions could be obtained for the Euler angles and their statistical distributions resolved with respect to the direction of the average texture axis. Polarized Raman spectra from single-crystalline hydroxyapatite and textured polycrystalline (teeth enamel) samples were compared, and a validation of the proposed Raman method could be obtained through confirming the agreement between RTE values obtained from different samples.

Raman spectroscopy analysis of dental enamel treated with whitening product – Influence of saliva in the remineralization

“…Hydroxyapatite is an anisotropic material, thus, signal intensity might be affected by the crystallographic orientation. According to the research of Pezzotti et al [9,10] this deviation in the orientation is enhanced for molar teeth and mainly in the occlusal region. This way, and in order to minimize the effects of crystallographic orientation the samples were obtained only from the vestibular surface of incisor teeth with a precision diamond saw (Buehler Isomet 1000, USA) in order to obtain 12 samples with 8 mm × 2 mm and only with dental enamel.…”

A pilot study on high wavenumber Raman analysis of human dental tissues

“…The alignments of the HAP crystals are not random in enamel, and the c‐axis of majority crystals appear roughly along the direction that is perpendicular to the external surface of the enamel layer (see the inset of Figure ) . The intensity of the Raman signal at 3,570 cm −1 is maximum when the polarization of the laser beam is aligned along the c‐axis (i.e., p ∥ c‐axis) and decreases while the polarization rotates away.…”

Green Tea Polyphenols Coupled with a Bioactive Titanium Alloy Surface: In Vitro Characterization of Osteoinductive Behavior through a KUSA A1 Cell Study

“…In Figure 3a, for the samples cultured in the normal medium, bands are barely visible on the CT sample, while they are well present on the spectrum of the sample functionalized with polyphenols. It is also possible to deconvolute the bands into two peaks at 940 cm −1 and 960 cm −1 , numbered as 1 and 2 in Figure 3, which are respectively correlated with the vibration of amorphous HAp and crystalline HAp [44,45,46,47]. …”