Vibrational algorithms for quantitative crystallographic analyses of hydroxyapatite-based biomaterials: II, application to decayed human teeth

Abstract

A systematic investigation, based on highly spectrally resolved Raman spectroscopy, was undertaken to research the efficacy of vibrational assessments in locating chemical and crystallographic fingerprints for the characterization of dental caries and the early detection of non-cavitated carious lesions. Raman results published by other authors have indicated possible approaches for this method. However, they conspicuously lacked physical insight at the molecular scale and, thus, the rigor necessary to prove the efficacy of this spectroscopy method. After solving basic physical challenges in a companion paper, we apply them here in the form of newly developed Raman algorithms for practical dental research. Relevant differences in mineral crystallite (average) orientation and texture distribution were revealed for diseased enamel at different stages compared with healthy mineralized enamel. Clear spectroscopy features could be directly translated in terms of a rigorous and quantitative classification of crystallography and chemical characteristics of diseased enamel structures. The Raman procedure enabled us to trace back otherwise invisible characteristics in early caries, in the translucent zone (i.e., the advancing front of the disease) and in the body of lesion of cavitated caries.

Analysis of root surface properties by fluorescence/Raman intensity ratio

“…Hence, we used values showing the ratio of fluorescence intensity of calculus to the intensity of the HA Raman band, as previous studies reported that the amount of calculus present was in proportion to fluorescence intensity [ 22 ] and the HA Raman band provided quantitative information regarding minerals in biomaterials such as bones [ 16 ] and teeth [ 20 ]. In our study, the corrected spectrum values were normalized to the HA Raman band intensity at 960 cm −1 to produce quantitative results.…”

“…Furthermore, it has been applied to the pathology of hard tissues including bones and teeth, by obtaining Raman spectra of hydroxyapatite (HA) and organic components such as proteins [ 16 – 18 ]. It has also been reported that detailed Raman spectral analysis of HA was highly useful for assessments of decayed teeth [ 19 , 20 ].…”

Molecular Fingerprint Imaging to Identify Dental Caries Using Raman Spectroscopy

“…In previous works [1,6,7], we have systematically and quantitatively monitored the evolution of tooth enamel demineralization according to the chemical formula, Ca 5-y (HPO 4 ) y (PO 4 ) 3−y (OH) 1−y (H 2 O) y . This is a generally valid chemical representation of the enamel apatite structure in the presence of a fraction y of Ca vacancies.…”

“…Evaluations of crystallinity, residual stress analyses, and chemical assessments of molecular structures can thus be performed without contact, damage, or radiation exposure. Since Raman spectroscopy allows analysis at the molecular level without requiring fluorescent probes, fixation, or other types of manipulation, it has recently received attention for its potential applications in several fields of medical science, including dentistry [1]. Various methods of dental analysis using Raman spectroscopy have recently been reported, such as the detection of trace elements in the enamel [2] and the detection of dentin formation in the dental pulp tissue [3].…”

“…Furthermore, modern devices have enabled us to collect Raman data at various measurement sites and configurations and to construct highly reliable algorithms with suitable precision [6]. When such algorithms are used as diagnostic tools, as we have recently reported, Raman spectroscopy can be used as a novel method for the early diagnosis of dental caries [1]. Moreover, Raman spectroscopy allows for the detection of a threshold state of irreversible structural change at the very early stages of tooth enamel demineralization, as caused, for example, by carbonated beverages (e.g., Coca-Cola TM ) [7].…”