Estudo de lesão de cárie experimental via espectroscopia fotoacústica e raman

Abstract

Dental caries are chemical-parasitic, in which the bacteria present in the oral cavity metabolize dietary sugars and produce weak acids which demineralize the dental tissues. The standard methods used by dental surgeons for detection and treatment of caries are visual inspection and radiographic examinations. The researches for new caries detection methods aims to increase the reliability of diagnosis. The caries detection method should present some features such as the ability to detect caries at an early stage. in this point of view spectroscopic methods can be used for detection and analysis of dental caries process, allowing to obtain information about the structural changes presented by the infected tissues. This study aims to evaluate in vitro, through photoacoustic spectroscopy (in the visible-ultraviolet regions) and por Raman spectroscopy (medium infrared region), structural and molecular changes of carious dentin compared to sound dentin. The results obtained by means of photoacoustic spectroscopy analysis indicate demineralization in dentin caries induced with greater exposure of the organic matrix mainly composed of collagen. The photoacoustic phase resolved method in collagen bands showed initial process of demineralization of tooth tissue analyzed, because the phase of the signal in collagen band centered at 325 nm showed a decrease for the dentin with induced caries when compared to sound dentin. The same behavior was observed in the phase difference between the bands attributed to the collagen and the porphyrin, proteins found in dentin, showing the exposure of the organic matrix in dentin with induced caries. Raman spectroscopy was used to study possible structural changes in dentin collagen and the results also indicated demineralization of dentin, monitored by reducing the peak Raman attributed to phosphate group, which is a component of the hydroxyapatite crystals in the mineral portion of the dentin. The technique also indicates that the collagen denaturation has not occurred, a common process in advanced caries that can be analyzed evaluating the cross linked bound through the variation of the ratio between the bands at 1660 and 1690 cm-1, attributed to amide I. In addition to the demineralization, Raman spectroscopy also showed exposure of the organic matrix, the collagen bands, observed by the increase in the band area correlated to amide I, according to the results obtained with the photoacoustic spectroscopy. The results obtained in this work showed that the initial stages of dentin caries lesion was possible feature a demineralization and increased exposure of organic matrix, showing that the photoacoustic and Raman spectroscopies are promising for in vitro study of dental caries in initial stages.