We have assembled a double-integrating-sphere system to measure the absorption (μa) and reduced scattering (μ's) coefficients of materials with high turbidity. We have employed the Inverse Adding-Doubling (IAD) algorithm to access these optical properties. The experimental system is a homemade setup assembled with broadband sources and 3D printed spheres, equipped with an optical fiber bundle for excitation and a spectrometer for detection. We have used a reference phantom (polyurethane plus Titanium Dioxide) with known optical properties at 633 nm (μa= 0.0019 mm-1 and μ's= 0.477 mm-1 ) to validate the system. The system can reliably measure the optical properties of turbid samples from 400 to 950 nm with one of the experimental setups and from 950 to 1650 nm with a second experimental setup.
Video plethysmography (vPPG) is a noninvasive, remote diagnostics method that monitors cardiac activity by measuring subtle variations in the optical properties of skin driven by heart pulsations. However, the origin of the fluctuations in skin color at the heart rate responsible for the vPPG signal is not well understood. Using optical coherence tomography (OCT), we show evidence that the optical attenuation coefficient of the outermost layer of the epidermis is modulated at heart rate, being the modulation surrogate for the mechanical changes in the skin. We propose a hydraulic shock hypothesis to explain the phenomenon. The mechanical modulation of the non-vascularized epidermis would explain the modulation of optical properties of superficial skin, allowing for detection of pulsation even for non-penetrating radiation wavelengths such as blue light, as it is often observed.
Peri-implantitis is a destructive inflammatory process that affects the tissues that provide support to the dental implant, the bone and gingiva, and can lead to the loss of the implant. Among the treatments of this disease, the irradiation of the contaminated surface with high intensity lasers is considered a promising alternative; Thus, irradiation parameters must be correctly adjusted in order to promote an efficient and safe treatment. This study investigated the temperature changes at the implant-bone interface during simulated implant surface decontamination using an 808nm diode laser. Dental implants were inserted in bovine bone, in which an artificial periimplant bone defect was made. Access holes of 0.5mm diameter were drilled to allow the positioning of four Ktype thermocouples in different regions: T0 Implant-bone interface, T1 inside the implant, T2 In the bone defect, T3 In the apex of the implant. For laser irradiation, an optical fiber was used at a distance of 0.5mm from the implant surface, and the mean output power varied between 0.5 to 3.0W on both pulsed (PW) and continuous (CW) wave modes. Irradiations were performed by 60s, and the temperature rises were registered for a period of 180s. It was observed that the critical threshold of 47ºC was exceeded at T0, T1 e T2 thermocouples when irradiations were performed at 1.0W; for T3 thermocouple, the threshold was exceeded at 3.0W CW mode. For PW mode, the thermocouples T0, T1, T2 had the threshold exceeded at the power of 1,0W and for T3 the threshold was exceeded at 3.0W. Decontamination of implant surfaces using the diode laser did not excessively heat the implant-bone interface within the mean output power ranging from 0.5 to 1.0W; however, the temperature rise is critical when using the mean power of 0.5W CW and 1.0W PW. Thus, using the PW mode up to the power of 1W seems to be a promising parameter for a safe clinical application.
Searching for new methods to provide information of biochemical composition and structure is critical to improve the prognosis of thyroid diseases. The use of time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help develop a portable, minimally invasive, and non-destructive method to assist during surgical procedures. This research looks for employ a fluorescence technique based on lifetime measurements to differentiate healthy and benign lesions from malignant thyroid tissue. We employ a wide range of excitation and chose a more appropriate region for this work: 298-300 nm; and the fluorescence decay was measured at 340-450 nm. We observed fluorescence lifetimes at 340 nm emission of 0.80±0.26 and 3.94±0.47 ns for healthy tissue; 0.90±0.24 and 4.05±0.46 ns for benign lesions; and 1.21±0.14 and 4.63±0.25 ns for malignant lesions. For 450 nm emissions, we obtain lifetimes of 0.25±0.18 and 3.99±0.39 ns for healthy tissue, 0.24±0.17 and 4.20±0.48 ns for benign lesions, 0.33±0.32 and 4.55±0.55 ns for malignant lesions. We successfully demonstrated that fluorescence lifetimes at 340 nm emission can differentiate between thyroid malignant and healthy/benign tissues.
Fine-needle aspiration cytology is the standard technique to diagnose thyroid pathologies. However, this method results in a high percentage of inconclusive and false negatives. The use of time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help to develop a portable, minimally invasive, and nondestructive method to assist during surgical procedures. This study aimed to use fluorescence lifetimes to differentiate healthy and benign tissues from malignant thyroid tissue. The thyroid tissue was excited at 298–300 nm and the fluorescence decay registered at 340 and 450 nm. We observed fluorescence lifetimes at 340 nm emission of 0.80±0.26 and 3.94±0.47 ns for healthy tissue; 0.90±0.24 and 4.05±0.46 ns for benign lesions; and 1.21±0.14 and 4.63±0.25 ns for malignant lesions. For 450 nm emissions, we obtain lifetimes of 0.25±0.18 and 3.99±0.39 ns for healthy tissue, 0.24±0.17 and 4.20±0.48 ns for benign lesions, 0.33±0.32 and 4.55±0.55 ns for malignant lesions. Employing analysis of variance, we differentiate malignant lesions from benign and healthy tissues. In addition, we use quadratic discriminant analysis to distinguish malignant from benign and healthy tissues with an accuracy of 76.1%, sensitivity of 74.7%, and specificity of 83.3%. These results indicate that time-resolved fluorescence can assist medical evaluation of thyroid pathologies during surgeries.
This study aimed to assess how the wear that brushing promotes affects CO 2 laser-irradiated enamel microhardness after cariogenic challenge in vitro. Forty fragments measuring 4×4 mm were randomly assigned to four groups according to the enamel surface treatment: G1—control, G2—CO 2 -laser irradiation, G3—brushing, and G4—CO 2 laser irradiation + brushing. A laser device emitting at 10.6 μm was used (power=0.5 W , energy per pulse=0.05 mJ , and frequency=10 kHz ). Specimens belonging to groups G3 and G4 were brushed (80,000 strokes) with a brushing simulator using toothpaste. Next, the samples were challenged with acid: the specimens were immersed in demineralizing and remineralizing solutions for 8 days. The acid resistance of enamel was evaluated by cross-sectional microhardness tests. The area under the curve (KHN×μm ) was calculated. Analysis of variance (ANOVA) one-away and Fisher’s test were performed for the statistical analysis (p<0.05 ). Group G2 specimens (31,185±4706 ) were statistically different from specimens belonging to groups G1 (26,723±2446 ), G3 (28,194±1376 ), and G4 (28,207±2234 ), which were statistically similar. The brushing time used in the present study probably wore the CO 2 -lased enamel, so demineralization could not be prevented in the brushed group.
The chemical carcinogens from tobacco are related to over 90% of lung cancers around the world. The
risk of death of this kind of cancer is high because the diagnosis usually is made only in advanced stages.
Therefore, it is necessary to develop new diagnostic methods for detecting the lung cancer in earlier
stages. The Fourier Transform Infrared Spectroscopy (FTIR) can offer high sensibility and accuracy to
detect the minimal chemical changes into the biological sample. The aim of this study is to evaluate the
differences on infrared spectra between normal lung cells and precancerous lung cells transformed by
NNK. Non-cancerous lung cell line e10 (ATCC) and NNK-transformed e10 cell lines were maintained in
complete culture medium (1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F12
[DMEM/Ham's F12], supplemented with 100 ng/ml cholera enterotoxin, 10 lg/ml insulin, 0.5 lg/ml.
hydrocortisol, 20 ng/ml epidermal growth factor, and 5% horse serum. The cultures were maintained in
alcohol 70%. The infrared spectra were acquired on ATR-FTIR Nicolet 6700 spectrophotometer at 4 cm-1
resolution, 30 scans, in the 1800-900 cm-1 spectral range. Each sample had 3 spectra recorded, 30
infrared spectra were obtained from each cell line. The second derivate of spectra indicates that there are
displacement in 1646 cm-1 (amine I) and 1255 cm-1(DNA), allowing the possibility to differentiate the
two king of cells, with accuracy of 89,9%. These preliminary results indicate that ATR-FTIR is useful to
differentiate normal e10 lung cells from precancerous e10 transformed by NNK.
This study investigated the compositional and crystallographic changes on enamel when irradiated by Er,Cr:YSGG (λ=2.7μm, 8.5J/cm2) or Nd:YAG (λ=1064nm, 84.9J/cm2 associated with black coating), its resistance to demineralization when irradiation is associated with fluoride (APF-gel), and CaF2-like material formation and retention. Sample surfaces were analyzed by ATR-FTIR (4000-650cm-1, 4cm-1) resolution. Irradiation with Er,Cr:YSGG laser promoted a significant decrease on carbonate content of enamel. After
Nd:YAG irradiation, it was observed a significant decrease of carbonate and amides I and II. X-ray diffraction showed that both laser irradiations promoted formation of α-tricalcium phosphate and tetracalcium phosphate, and a significant increase on the crystal growth of the enamel apatite (ANOVA, p<0.05 was used for all analysis). These changes can explain the improved resistance of enamel to demineralization observed in the second part of the study, in which 240 enamel slices were divided in 8 groups, received 4 min of professional fluoride gel (APF-gel 1.23%F-) applied before or after irradiation. After treatments, the formation of calcium fluoride (CaF2) was determined. The remaining slabs of each group were submitted to a 10-day pH-cycling
model and, subsequently, enamel demineralization was evaluated by cross-sectional microhardness. Both lasers significantly reduced enamel demineralization (ANOVA, p<0.05), and the previous APF-gel application followed by laser showed the higher reduction of enamel demineralization. CaF2 formed before pH-cycling was
significantly higher in groups were APF was associated with laser irradiation. After demineralization, these groups also presented higher CaF2 retention in respect to isolated treatments (only APF or only laser), suggesting its anticaries potential.
We aim to characterize natural caries enamel lesions by fluorescence spectroscopy. Sixty human samples with natural noncavitated caries lesions on smooth surfaces were selected and classified into three groups: dull, shiny, and brown lesions. All the samples were analyzed externally at the natural surface and after hemisectionig internally at the center of the lesion. The lesions were excited with a 405-nm InGaN diode laser and the fluorescence was collected with a single grating spectrometer. Four emission bands (455, 500, 582, and 622 nm) are identified in both sound and carious regions. The area under each emission band is correlated with the total area of the four bands for the sound and carious regions. The detected fluorescence from natural and cut surfaces through the caries lesions is not statistically different for the shiny and dull lesion, but is different [analysis of variance (ANOVA) (p<0.05)] for brown lesion at all emission bands. At the 405-nm excitation wavelength, the area of the fluorescence bands at 455 and 500 nm differ statistically for natural carious lesions and sound tissue.
The aim of this study was to determine safe parameters for intracanal laser irradiation. Single rooted extracted teeth were irradiated with the pulsed Er:YAG laser (2.94 μm) and Nd:YAG (1.06 μm) laser. The teeth with remaining root thickness ≥ 1mm on the apical portion were selected and divided in eight groups according to the laser parameters: output energy of 40-100 mJ/pulse; repetition rate of 10-15 Hz. The root canals were irradiated for 4 periods with a 20s breaks in between with the fiber stationary 1mm from the apical foramen, during 3s or from the apical to coronal surface in a continuous, circling fashion, with 2mm/s. Morphological changes were also observed by scanning electron microscopy.
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