Laser-induced breakdown spectroscopy; melanocyte; skin; pigmentation; nevus;MELANIN SYNTHESIS; NEVUS CELLS; TISSUE; PH; DIFFERENTIATION; ULTRAVIOLET; MELANOSOMES; TYROSINASE; MECHANISM; EXCHANGER

The concentration difference of major elements in melanocytic skin with respect to pigmentation level is analysed by laser-induced breakdown spectroscopy(LIBS) to investigate the applicability of LIBS as an in situ feedback tool for selective and complete laser removal of melanocytic skin tissue like nevus. The skin of black silkie chicken which had a characteristic darkly pigmented perifollicular skin surrounded by lightly pigmented extrafollicular skin was used as the sample. The results showed higher LIBS signal intensities of Ca2+ and Mg2+ but lower intensities of Na+, Cl- and K+ in the perifollicular skin than in the extrafollicular skin, which demonstrated the feasibility to use LIBS as a reliable method to distinguish skin tissues with difference in pigmentation level.

Spectrum Analysis [E05.1962.867]; Laser-Induced Breakdown-Spectroscopy; Tissues [A10]; Optical Tissue Differentiation and Identification;NORMAL HUMAN ENAMEL; HUMAN TOOTH ENAMEL; LINGUAL NERVE; MINERAL-COMPOSITION; FEEDBACK MECHANISM; PERIPHERAL-NERVES; CHEMICAL-ANALYSIS; LIBS PROSPECTS; SURGICAL LASER; DENTAL-CARIES

Compared to conventional techniques, Laser surgery procedures provide a number of advantages, but may be associated with an increased risk of iatrogenic damage to important anatomical structures. The type of tissue ablated in the focus spot is unknown. Laser-Induced Breakdown-Spectroscopy (LIBS) has the potential to gain information about the type of material that is being ablated by the laser beam. This may form the basis for tissue selective laser surgery. In the present study, 7 different porcine tissues (cortical and cancellous bone, nerve, mucosa, enamel, dentine and pulp) from 6 animals were analyzed for their qualitative and semiquantitative molecular composition using LIBS. The so gathered data was used to first differentiate between the soft-and hard-tissues using a Calcium-Carbon emission based classifier. The tissues were then further classified using emission-ratio based analysis, principal component analysis (PCA) and linear discriminant analysis (LDA). The relatively higher concentration of Calcium in the hard tissues allows for an accurate first differentiation of soft-and hard tissues (100% sensitivity and specificity). The ratio based statistical dif-ferentiation approach yields results in the range from 65% (enamel-dentine pair) to 100% (nerve-pulp, cancellous bone-dentine, cancellous bone-enamel pairs) sensitivity and specificity. 

dental caries; ultra-short lasers; thermal effects; atomic spectroscopy;INDUCED BREAKDOWN SPECTROSCOPY; QUANTITATIVE-ANALYSIS; REPETITION-RATE; TISSUE; FLUORESCENCE; CARIES; LIBS; BONE; IDENTIFICATION; ENAMEL

The goal of this work is to investigate the thermal effects of femtosecond laser (fs-laser) ablation for the removal of carious dental tissue. Additional studies identify different tooth tissues through femtosecond laser induced breakdown spectroscopy (fsLIBS) for the development of a feedback loop that could be utilized during ablation in a clinical setting. Scanning Election Microscope (SEM) images reveal that minimal morphological damages are incurred at repetition rates below the carbonization threshold of each tooth tissue. Thermal studies measure the temperature distribution and temperature decay during laserablation and after laser cessation, and demonstrate that repetition rates at or below 10kHz with a laser fluence of 40 J/cm(2) would inflict minimal thermal damage on the surrounding nerve tissues and provide acceptable clinical removal rates. Spectral analysis of the different tooth tissues is also conducted and differences between the visible wavelength fsLIBS spectra are evident, though more robust classification studies are needed for clinical trans-lation. These results have initiated a set of precautionary recommendations that would enable the clinician to utilize femtosecond laser ablation for the removal of carious lesions while ensuring that the solidity and utility of the tooth remain intact.