laser induced breakdown spectroscopy; teeth; caries; enamel; calcium; phosphorus; zinc;DENTAL-CARIES; ZINC-DEFICIENCY; ENAMEL; MODELS; SR

The aim of this work is a multi-component analysis of the element composition of the enamel and carious parts of teeth and the quantification of enamel demineralization using laser-induced breakdown spectroscopy (LIBS). For each tooth the P/Ca ratios of the emission line intensities in the enamel part and those in the carious regions were compared. Since zinc is a trace element, the same procedure was performed for Zn/Ca ratios in the enamel and carious parts. These comparisons showed that the mineral loss from carious lesions occurs at different rates for the studied elements. Calcium has the highest casualty rate. On the other hand, the zinc level diminishes also in the carious region but at a lower rate. The lines were obtained from plume plasma emission generated on the enamel and carious regions.

Laser-Induced Breakdown Spectroscopy (LIBS); tooth decay; caries; demineralization; element analysis;DECIDUOUS TEETH

The carious decay develops a tiny area of demineralization on the enamel, which could be detected by element analytic techniques such as laser-inducedbreakdown spectroscopy (LIBS). That demineralization can quickly turn into a large lesion inside the tooth, it is often discovered too late to prevent the kind of decay that leads to cavities. The same optical LIBS detection approach could be used for monitoring of the caries removal using laser ablation or drilling techniques. For LIBS measurements we applied LIBS 2500Plus (Ocean Optics Inc., Dunedin, USA) system, which consists of seven spectrometric channels, covering spectral region from 200 to 980 nm, which optical resolution 0,05 nm, the spectrometers are connected with sample fiber bundle for 7-channels spectral system to the chamber for solid and liquid samples, Q-switched Nd:YAG laser, at 1 064 nm, with energy per pulse - 40 mJ, which is applied to induce plasma in the samples. LIBS spectra were obtained after single shot of the laser in the region of pathology. Samples investigated by LIBS are extracted teeth from patients, with periodontal problems on different stage of carious lesions, and their LIBS spectra are compared with the LIBS signals obtained from normal enamel and dentine tissues to receive complete picture of the carious lesion development. The major line of our investigations is related to the development of a methodology for real-time optical feedback control during selective ablation of tooth tissues using LIBS. Tooth structures, with and without pathological changes, are compared and their LIBS element analysis is used to differentiate major changes, which occur during tooth carious process and growth.