Time-Resolved Laser-Induced Fluorescence Spectroscopy as a Guidance Tool for Laser Lithotripsy of Gallbladder Stones.

BACKGROUND AND OBJECTIVES: Although laser lithotripsy for fragmentation of gallbladder stones has been applied successfully in many clinical situations, this approach has two major limitations: (1) the potential to damage or perforate the bile duct and (2) the efficiency can be affected by the chemical composition of the gallstones. The present study evaluated the use of time-resolved laser-induced fluorescence spectroscopy to classify stone types and distinguish stone from tissue. MATERIALS AND METHODS: Ex vivo time-resolved laser-induced fluorescence analysis (excitation wavelength λex = 400 nm and emission wavelength = 450-700 nm) of 54 gallbladder stones and seven gallbladder tissue samples was conducted. The spectral and temporal parameters were analyzed using linear discrimination analysis (LDA) to differentiate stone from tissue and to classify different stone types using two wavelength regions (λ1 = 510-530 nm and λ2 = 550-570 nm). RESULTS: Examination of 54 gallbladder stones and seven gallbladder tissue samples showed a significant difference in spectral- and temporal-derived parameters. The data were classified using LDA, and the overall accuracy was 94.88%, 84.39%, and 85.79% for both spectral and temporal parameters, only spectral parameters, and only temporal parameters, respectively. CONCLUSIONS: Our findings establish the feasibility of using time-resolved laser-induced fluorescence spectroscopy as a tool to identify gallbladder stone types and as a stone-tissue detection system to improve the effectiveness of laser lithotripsy procedures and reduce the risk of damaging biliary tract tissues.

Satellite bands of the RbCs molecule in the range of highly excited states.

We report on the observation of three RbCs satellite bands in the blue and green ranges of the visible spectrum. Absorption measurements are performed using all-sapphire cell filled with a mixture of Rb and Cs. We compare high resolution absorption spectrum of Rb-Cs vapor mixture with pure Rb and Cs vapor spectra from the literature. After detailed analysis, the new satellite bands of RbCs molecule at 418.3 nm, 468.3, and 527.5 nm are identified. The origin of these bands is discussed by direct comparison with difference potentials derived from quantum chemistry calculations of RbCs potential energy curves. These bands originate from the lower Rydberg states of the RbCs molecule. This study thus provides further insight into photoassociation of lower Rydberg molecular states, approximately between Cs(7s) + Rb(5s) and Cs(6s) + Rb(6p) asymptotes, in ultracold gases.

Real-time local experimental monitoring of the bleaching process.

OBJECTIVE: The purpose of this article was to investigate a new setup for tooth bleaching and monitoring of the same process in real time, so to prevent overbleaching and related sideeffects of the bleaching procedure. BACKGROUND DATA: So far, known bleaching procedures cannot simultaneously monitor and perform the bleaching process or provide any local control over bleaching. MATERIALS AND METHODS: The experimental setup was developed at the Institute of Physics, Zagreb. The setup consists of a camera, a controller, and optical fibers. The bleaching was performed with 25% hydrogen peroxide activated by ultraviolet light diodes, and the light for monitoring was emitted by white light diodes. The collected light was analyzed using a red-green-blue (RGB) index. A K-type thermocouple was used for temperature measurements. Pastilles made from hydroxylapatite powder as well as human teeth served as experimental objects. RESULTS: Optimal bleaching time substantially varied among differently stained specimens. To reach reference color (A1, Chromascop shade guide), measured as an RGB index, bleaching time for pastilles ranged from 8 to >20 min, whereas for teeth it ranged from 3.5 to >20 min. The reflected light intensity of each R, G, and B component at the end of bleaching process (after 20 min) had increased up to 56% of the baseline intensity. CONCLUSIONS: The presented experimental setup provides essential information about when to stop the bleaching process to achieve the desired optical results so that the bleaching process can be completely responsive to the characteristics of every individual, leading to more satisfying results.

Comparison of composite curing parameters: effects of light source and curing mode on conversion, temperature rise and polymerization shrinkage.

This study analyzed the degree of conversion, temperature increase and polymerization shrinkage of two hybrid composite materials polymerized with a halogen lamp using three illumination modes and a photopolymerization device based on blue light emitting diodes. The degree of conversion of Tetric Ceram (TC) (Ivoclar Vivadent) and Filtek Z 250 (F) (3M/ESPE) was measured by Fourier transformation infrared spectroscopy at the surface and 2-mm depth; temperature rise was measured by digital multimeter, and linear polymerization shrinkage was measured during cure by digital laser interferometry. Composite samples were illuminated by quartz-tungsten-halogen curing unit (QTH) (Astralis 7, Ivoclar Vivadent) under the following modes: "high power" (HH) 40 seconds at 750 mW/cm2, "low power" (HL) 40 seconds at 400 mW/cm2 and "pulse/soft-start" (HP) increasing from 150 to 400 mW/cm2 during 15 seconds followed by 25 seconds pulsating between 400 and 750 mW/cm2 in 2-second intervals and by light emitting diodes (LED) (Lux-o-Max, Akeda Dental) with emitted intensity 10 seconds at 50 mW/cm2 and 30 seconds at 150 mW/cm2. A significantly higher temperature increase was obtained for both materials using the HH curing mode of halogen light compared to the HP and HL modes and the LED curing unit after 40 seconds. Significantly lower temperature values after 10-second illumination were obtained when LED was used compared to all halogen modes. For all curing modes, there was no significant difference in temperature rise between 20 and 40 seconds of illumination. Results for the degree of conversion measurements show that there is a significant difference in the case of illumination of resin composite samples with LED at the surface and 2 mm depth. For polymerization shrinkage, lower values after 40 seconds were obtained using LED compared to QTH.

The influence of age on tooth root colour changes.

The purpose of this study was to examine the relationship between tooth root colour and age, and its possible application in age assessment. In this research altogether 100 tooth roots have been analysed. All teeth, that is their roots, were digitally recorded and the colorimetric treatment was made using Adobe Photoshop 7.0 computer program. Studies have shown no significant difference between RGB values analysed on the whole root surface or only on its central part, with certainty p >0.99. It is also established that there is no statistically significant difference in colouration on four anatomical surfaces (buccal, mesial, lingual, distal) of tooth roots with certaintyp>0.99 for red, p>0.99 for green and p>0.50 for blue colouration component. Statistical data interpretation showed that there is a linear correlation between obtained RGB values and age, with r=-0.994, p>0.99 for red component, r=-0.972, p>0.99 for green and r=-0.982, p>0.95 for blue colouration component. From the obtained results it is possible to conclude that analysing the above mentioned parameter we can easily establish dental age and this technique can be the basis of practical application in establishing chronological age of man.

Measurement of linear polymerization contraction using digital laser interferometry.

Polymerization shrinkage is an unavoidable consequence of resin composite photopolymerization and is one of the most important factors in determining the clinical quality and durability of composite filling. Many different methods of measuring polymerization shrinkage are described in the literature. Digital laser interferometry is a method that enables direct observation of polymerization shrinkage in real time. This study used the digital holographic interferometry method to measure the linear polymerization contraction of composite materials: Tetric Ceram (Vivadent), Spectrum TPH (Dentsply) and Valux Plus (3M Dental Products) polymerized with three different curing modes of the Elipar Trilight (ESPE) halogen curing unit. The highest polymerization contraction was recorded by "standard mode" (ETS) (1.24 +/- 2.66% lin), and the lowest by "medium mode" (ETM) (0.40 +/- 0.41% lin) during 40 second illumination. The "exponentional mode" (ETE) showed the highest expansion during the first 10 seconds of illumination. Curing units with initial low intensity enable better inner adaptation of composite material, preventing the detachment of material from dentin during polymerization and avoiding the negative consequences of polymerization shrinkage.