Application of Raman Spectroscopy for Dental Enamel Surface Characterization

Dental enamel is the most complex and highly mineralized human body tissue, containing more than 95% of carbonated hydroxyapatite and less than 1% of organic matter. Current diagnostic methods for enamel caries detection are unable to detect incipient caries lesions. Many papers determine the re-mineralizing effect using many fluorinated compounds and different demineralizing solutions to test physical characterizations such as microhardness, roughness, wettability, among others, but there is not much information about the use of Raman Spectroscopy. Raman Spectroscopy is an efficient technique of chemical characterization to identify functional groups (phosphate-hydroxyl groups) found in the hydroxyapatite formula, which helps identify the level of mineralization on dental enamel surface. Raman spectroscopy is applicable to any state of aggregation of the material, indicated for biological samples. Given the minimum bandwidth of a laser source, as with all spectroscopic techniques that use a laser source, a small sample is sufficient, which makes it an important technique in the analysis of reactive products with very low yield. Raman spectroscopy can be used to obtain the main functional groups in order to determine the remineralization of dental enamel; these results are highly valuable as they can help us make the best decisions on dental treatments

Microhardness, Structure, and Morphology of Primary Enamel after Phosphoric Acid, Self-Etching Adhesive, and Er:YAG Laser Etching

Background. Phosphoric acid is the traditional etching agent; self-etching adhesives and Er:YAG laser are alternative methods. Knowledge of deciduous enamel etching is required. Aim. To evaluate primary enamel microhardness, structure, and morphology after phosphoric acid, self-etching, and Er:YAG laser etching. Design. Seventy primary incisors were assigned to five groups (n=14): I (control), II (35% phosphoric acid), III (self-etching adhesive), IV (Er:YAG laser at 15 J/cm2), and V (Er:YAG laser at 19.1 J/cm2). Microhardness was evaluated by Vickers indentation. Chemical composition was analyzed by energy dispersive X-ray spectroscopy and morphological changes by scanning electron microscopy. One-way ANOVA, Kruskal–Wallis, Mann–Whitney U, and Pearson bivariate correlation were employed (α=0.05). Results. Vickers microhardness showed differences and no correlation with Ca/P ratio. Group II showed differences in carbon, oxygen, and phosphorus atomic percent and group V in Ca/P ratio. Morphological changes included exposed prisms, fractures, craters, and fusion. Conclusions. Enamel treated with phosphoric acid showed different chemical characterization among groups. Self-etching and Er:YAG laser irradiation at 19.1 J/cm2 showed similar microhardness and chemical characterization. Er:YAG laser irradiation at 15 J/cm2 maintained microhardness as untreated enamel. Er:YAG laser irradiation at 19.1 J/cm2 enhanced mineral content. Morphological retentive changes were specific to each type of etching protocol