Assessment of the efficiency of dental excavation methods using laser speckle imaging.

This paper introduces a novel application of the laser speckle technique in dentistry, focusing on assessing the efficiency of dental excavation methods used to remove decayed tooth structure. The aim is to evaluate the efficiency of two chemo-mechanical agents and the high-speed drill using the laser speckle technique, which offers objective, non-invasive, and real-time evaluation capabilities. Extracted human primary molars with active occlusal carious lesions were sectioned into three parts, with each part allocated to one of three groups: Group 1 (Brix3000®), Group 2 (Papacarie DUO®), and Group 3 (High-speed drill mechanical caries removal). Caries removal was performed using the designated agent or method for each group. After caries excavation, speckle imaging using a 632.8 nm laser was conducted. Additionally, SEM was used to acquire micro-photographs of the surface morphology of the treated samples. The findings reveal insights into the comparative efficiency of the three dental excavation agents and methods using the laser speckle technique. The speckle parameters extracted from speckle patterns generated by treated teeth provide valuable information for evaluating the performance of the excavation methods. The scanning electron microscopy images also offer detailed visual evidence to support the analysis. This paper demonstrates the potential of the laser speckle technique for assessing the efficiency of dental excavation methods. The objective, non-invasive, and real-time evaluation provided offers advantages over subjective visual assessment and manual measurements.

Radiofrequency modulator for marine lidar radar systems featuring compact and agile extra-cavity architecture using a polarimetric effect.

This paper proposes a new, to the best of our knowledge, modulator architecture for a microwave-modulated lidar for marine applications. The principle is based on the use of an infrared picosecond laser source, coupled to an external cavity, ensuring wavelength conversion in the visible range as well as radiofrequency modulation. Wavelength conversion is performed by a nonlinear crystal associated with adapted mirrors, while multiple round trips and polarization control in the cavity ensure microwave modulation. This paper presents both modeling of the emitted signal and the practical realization of this device.

Interpretation of the bacterial growth process based on the analysis of the speckle field generated by calibrated scattering media.

The speckle imaging technique has been proven to be a reliable and effective method for real-time monitoring of the growth kinetics of any bacterium in suspension. To understand the interaction between the light and the bacterial density, a simulation of the bacterial growth of Bacillus thuringiensis was performed using calibrated microspheres of different concentrations and sizes. Results show that the decrease of speckle grain size with the increase of the medium scattering coefficient reveals the two essential phases of the bacterial growth: the exponential phase where the number of the bacteria increases and the stationary phase where sporulation and cell lysis occur.

Single speckle image analysis for monitoring the hardening kinetics of glass ionomer cements.

In this paper, we monitor the setting reaction of commercial glass ionomer cements using a laser speckle technique and adopting a spatial approach in the analysis of recorded speckle images. Experimental results showed that spatial contrast and speckle grain size increased as two studied cements underwent their setting reactions. After combining two geometrical configurations to measure the intensities of backscattered and transmitted light, we concluded that the increase in speckle grain size was caused by an increase in size of the scattering centers, since cement components aggregate and hence transition from a Rayleigh to a Mie scattering regime. Finally, two main phases were distinguished in the hardening process, as reported in the literature; however, the technique we propose has the advantage of easily identifying these two phases. The analysis of a single speckle image offers multiple advantages over the temporal analysis of a series of speckle images, in particular due to the low number of images recorded and a far shorter image processing time.

Monitoring the curing kinetics of glass ionomer cements by modeling the temporal correlation of speckle images.

Glass ionomer cements (GIC) originated in the mid-twentieth century with the rising demand for dental materials to be biocompatible and cost-effective. Due to their unique ability to bond to tooth structure, coupled with their fluoride-releasing potential, GIC are widely used in pediatric dentistry. However, the curing kinetics of these materials are not extensively documented. In this study, we show that dynamic laser speckle is an efficient method for monitoring the acid-base reaction that occurs during the self-setting of conventional GIC. Plotted temporal correlation curves, showing the degree of similarity between several recorded speckle patterns, indicate that the GIC kinetics reaction slows down during the curing phenomenon. Furthermore, the numerical fit of the temporal correlation curves with a Lorentzian profile gives the characteristic times of the reaction and reveals two phases during GIC hardening.

Dentinal tubule penetration of AH Plus, BC Sealer and a novel tricalcium silicate sealer: a confocal laser scanning microscopy study.

OBJECTIVES: The aim of this in vitro study was to assess the dentinal tubule penetration of three different sealers, AH Plus, BC Sealer and a novel tricalcium silicate sealer (NTS). MATERIALS AND METHODS: Ninety-six human maxillary central incisors were divided into three experimental groups (n = 32) and were filled with gutta-percha using a single-cone technique in conjunction with one of the three sealers: AH Plus, BC Sealer or NTS. The roots in each group were cross-sectioned at 1 and 5 mm from the root apex, and the surfaces were examined under confocal laser scanning microscopy (CLSM). The sealer penetration depths were measured at their maximum depths and at four circumferential depths (12, 3, 6 and 9 o'clock) and were evaluated using ImageJ software (ImageJ, NIH). RESULTS: The maximum and mean penetration depths were significantly higher at 5 mm compared to 1 mm from the apex in the AH Plus (p < 0.001), BC Sealer (p < 0.001) and NTS groups (p < 0.001). No significant difference was observed between the groups at 1 mm for both parameters. The maximum and mean penetration depths were significantly lower at 5 mm for AH Plus compared with the other two groups (p = 0.012). CONCLUSIONS: Within the study limitations, the BC Sealer and NTS demonstrated better tubule penetration results than the AH Plus sealer. CLINICAL RELEVANCE: Although no study has confirmed a relationship between the penetration depth of root canal sealers and the prevention of apical periodontitis, dentinal tubule sealer penetration may improve obturation quality.

Extra-cavity radiofrequency modulator for a lidar radar designed for underwater target detection.

The hybrid lidar-radar technique is commonly used for shallow underwater target detection. This technique requires a powerful blue-green RF-modulated laser with stable microwave frequency. In this paper, a novel modulator design perfectly suited for this application is proposed. It consists of an extra-cavity modulator composed of two plane mirrors and a second-harmonic generator stage within the cavity to maximize the energy efficiency. This modulator is coupled with a picosecond Nd:YAG infrared laser source to insure the emission of a powerful pulse (up to 5 mJ). Results considering this architecture show stable modulation frequency and a powerful modulated beam. As the emitted signal lasts only a few nanoseconds, a range-gating method can be used for target localization. This emitted signal has experimentally proven to preserve input beam polarization, which also can be employed to enhance the target return.

Assessing White Wine Viscosity Variation Using Polarized Laser Speckle: A Promising Alternative to Wine Sensory Analysis.

In this paper, we report measurements of wine viscosity, correlated to polarized laser speckle results. Experiments were performed on white wine samples produced with a single grape variety. Effects of the wine making cellar, the grape variety, and the vintage on wine Brix degree, alcohol content, viscosity, and speckle parameters are considered. We show that speckle parameters, namely, spatial contrast and speckle decorrelation time, as well as the inertia moment extracted from the temporal history speckle pattern, are mainly affected by the alcohol and sugar content and hence the wine viscosity. Principal component analysis revealed a high correlation between laser speckle results on the one hand and viscosity and Brix degree values on the other. As speckle analysis proved to be an efficient method of measuring the variation of the viscosity of white mono-variety wine, one can therefore consider it as an alternative method to wine sensory analysis.

Evaluation of low viscosity variations in fluids using temporal and spatial analysis of the speckle pattern.

The noninvasive detection of a material's viscoelasticity is of great importance in the medical field. In fact, certain diseases cause changes in tissue structure and biological fluid viscosity; tracking those changes allows for detection of these diseases. Rheological measurements are also imperative in the industrial field, where it is necessary to characterize a material's viscoelasticity for manufacturing purposes. In this Letter, we present a noncontact, noninvasive, and low cost method for determining low viscosity values and variations in fluids. Laser speckle and viscometric measurements are performed on test samples having low scattering coefficients and low viscosities. The speckle spatial analysis proved to be as accurate as the speckle temporal correlation method reported in previous studies. Very low viscosities of the order of 1 mPa.s were retrieved for the first time using speckle images with either a frame rate of 1950 fps or a single acquired image.

Analysis of experimental depolarizing Mueller matrices through a hybrid decomposition.

We propose a new decomposition for depolarizing Mueller matrices. This decomposition, which consists of a product of four basic optical devices (two diattenuators, a retarder, and a depolarizer) is derived from a previous one known as "symmetric decomposition" [J. Opt. Soc. Am. A26, 1109 (2009)10.1364/JOSAA.26.001109JOAOD61084-7529] and makes it easier to interpret polarization properties of Mueller matrices and improves estimation of the extracted parameters. Its application is illustrated by several theoretical and experimental examples.

Influence of size, proportion, and absorption coefficient of spherical scatterers on the degree of light polarization and the grain size of speckle pattern.

In this paper, we present the evolution of speckle pattern polarimetric parameters in response to controlled changes in scatterer sizes, proportions, and the absorption coefficient in media. The experimental study was performed on mixtures of polystyrene microspheres with dye in order to ensure biological medium-like properties. The speckle grain sizes and degrees of polarization for linear and circular light were monitored. We observed helicity flipping in the degree of circular polarization for small scatterer proportion around 25%. Furthermore, linear depolarization decreased slightly for media containing more small particles. Good agreement was shown with numerical results computed using a Monte Carlo simulation of polarized light taking into account our experimental configuration. Speckle grain size also evolves with the increase of small scatterers as well as the media absorption coefficient. Such variations of properties are encountered during fruit maturation, in tissues in precancerous stages, and any transformation that causes a modification in particle proportions and absorption coefficient in biological media. The computed parameters proved to be sensitive to these changes.

Detection of Golden apples' climacteric peak by laser biospeckle measurements.

In this paper, we report a study in which a laser biospeckle technique is used to detect the climacteric peak indicating the optimal ripeness of fruits. We monitor two batches of harvested Golden apples going through the ripening phase in low- and room-temperature environments, determine speckle parameters, and measure the emitted ethylene concentration using gas chromatography as reference method. Speckle results are then correlated to the emitted ethylene concentration by a principal component analysis. From a practical point of view, this approach allows us to validate biospeckle as a noninvasive and alternative method to respiration rate and ethylene production for climacteric peak detection as a ripening index.

Retrieving controlled motion parameters using two speckle pattern analysis techniques: spatiotemporal correlation and the temporal history speckle pattern.

This paper presents simulation of speckle activity through controlling a moving plate. We present two procedures to extract the initial movement frequency and amplitude, either through correlation calculus or through processing the temporal history of the speckle pattern. We compare and discuss these two methods in terms of efficiency and the ability to retrieve motion parameters. The correlation technique seems to be more suitable for monitoring biospeckle activity as it provides more reliable parameter estimation than the temporal history of the speckle pattern. The evolution of temporal history of the speckle pattern parameters and their response sensibility with amplitude and frequency variations have been studied and quantified. Briers contrast appears to depend only on movement amplitude, whereas inertia moment varies with amplitude and frequency.

Scattering through fruits during ripening: laser speckle technique correlated to biochemical and fluorescence measurements.

This paper reports monitoring fruits maturation using speckle technique. Performed measurements aim the assessing of biological inner fruit variation effect on the speckle image. We show that the speckle grain size is both affected by the glucose level inside the fruits and by the chlorophyll content. Moreover, the determination of circular polarization degree and circular grain size indicate that a Rayleigh diffusion regime gradually becomes predominant in fruits. Principal component analysis is used to highlight high correlation between results and strengthen the establishment of speckle as a novel non invasive method to monitor fruits ripening.

Detection of an underwater target through modulated lidar experiments at grazing incidence in a deep wave basin.

The effectiveness of a pulsed radiofrequency modulated lidar and associated processing for underwater target detection at grazing incidence was experimentally assessed in a wave basin 50 m long and 20 m deep, under different conditions of swell produced within this facility to benefit from a controlled interface. This paper reports our experiments and offline data processing results, and describes significant improvements in the probability of detection that demonstrate the interest of using such a technique in this context.

Lack of Correlation Between the Penetration of Two Types of Sealers and Interfacial Adaptation to Root Dentine.

OBJECTIVE: This study aimed to determine the correlation between sealer penetration into dentinal tubules and interfacial adaptation to root canal walls using a hydraulic calcium silicate-based sealer, Endosequence Bioceramic Sealer (Brasseler USA, Savannah, GA, USA), and an epoxy resin-based sealer, AH Plus (Dentsply DeTrey, Konstanz, Germany). METHODS: Sixty-four maxillary central incisors were endodontically prepared with nickel-titanium rotary instruments and randomly assigned into two groups (n=32). Roots were filled with gutta-percha using a single-cone technique in conjunction with one of the two sealers, AHP or BCS. Sealers were mixed with Rhodamine B and analysed under a confocal laser scanning microscope. Transverse sections at 5 mm from root apex were obtained. The circumference of the root canal wall was first outlined and measured to determine the circumferential percentage of sealer penetration. The regions along the canal walls where the sealer had penetrated the dentinal tubules were delineated and measured. Then, the outlined distances were divided by the canal circumference. The width of each gap was measured and pooled for each specimen for comparison to determine the interfacial adaptation. The measurements were repeated twice to ensure reproducibility. Mann-Whitney tests were performed to compare continuous variables between AHP and BCS groups. The correlation between gap width and percentage of sealer penetration was investigated using the Spearman correlation coefficient. RESULTS: No significant difference was observed between groups regarding the percentage of sealer penetration (P>0.05) and the gap width (P>0.05). Also, there was no significant correlation between the two variables analysed for AHP (r=0.165; P>0.05) and BCS (r=-0.147; P>0.05) and in the overall sample (r=0.061; P>0.05). CONCLUSION: The present results show no correlation between interfacial adaptation and sealer penetration in dentinal tubules in the total sample and among sealer subgroups. The ability of root canal sealers to penetrate dentinal tubules cannot be considered a sign of better interfacial adaptation.

Real-time monitoring of bacterial growth kinetics in suspensions using laser speckle imaging.

In microbiology, monitoring the growth of any microorganism in culture is important for studying and optimizing the growth kinetics, the biomass and the metabolite production. In this work, we show that laser speckle imaging is a reliable technique that can be used to perform real-time monitoring of bacteria growth kinetic in liquid culture media. Speckle parameters, specifically speckle grain size and the spatial contrast of the speckle images, and standard analytical parameters (optical density, pH and colony forming units) were measured during the culture of different strains of Bacillus thuringiensis. Our results show that both speckle grain size and spatial contrast decrease with bacterial growth. Furthermore, speckle parameters are sensitive to the fermentation conditions. Statistical analysis revealed a relatively high correlation between speckle and analytical parameters.

Influence of the EndoActivator Irrigation System on Dentinal Tubule Penetration of a Novel Tricalcium Silicate-Based Sealer.

This study compared the effects of a conventional endodontic needle with an agitation system on a novel tricalcium silicate-based sealer (NTS) in terms of dentinal tubule penetration and interfacial adaptation to a root canal. Fifty single-rooted, recently-extracted human maxillary central incisors were randomly distributed into two homogeneous groups characterized by two different final cleansing systems: Conventional endodontic needle, or EndoActivator®. After instrumentation, all the teeth were filled with the gutta-percha single cone technique in conjunction with the novel tricalcium silicate-based sealer. Teeth were horizontally sectioned at 1 and 5 mm from the apex and were observed under a confocal laser scanning microscope (CLSM) at five magnifications. The maximum, mean, and the circumferential percentage of the sealer penetration inside the tubules were measured. Moreover, the gap width was evaluated using Image J software (National Institutes of Health, Bethesda, MD). EndoActivator® did not result in a significantly higher circumferential percentage of sealer penetration than conventional irrigation (p > 0.05). However, the gap width was significantly lower with EndoActivator®, compared to conventional needles at both 1 mm (p = 0.035) and 5 mm (p = 0.038). The EndoActivator® irrigation system did not significantly improve the NTS penetration, as compared to the conventional endodontic needle irrigation. Activation of the irrigation reduced the gap width significantly.

Early diagnosis of teeth erosion using polarized laser speckle imaging.

Dental erosion starts with a chemical attack on dental tissue causing tooth demineralization, altering the tooth structure and making it more sensitive to mechanical erosion. Medical diagnosis of dental erosion is commonly achieved through a visual inspection by the dentist during dental checkups and is therefore highly dependent on the operator's experience. The detection of this disease at preliminary stages is important since, once the damage is done, cares become more complicated. We investigate the difference in light-scattering properties between healthy and eroded teeth. A change in light-scattering properties is observed and a transition from volume to surface backscattering is detected by means of polarized laser speckle imaging as teeth undergo acid etching, suggesting an increase in enamel surface roughness.

Second-harmonic-generation-polarimeter calibration by means of a quartz plate.

A dual-rotating-retarder polarimeter was used to determine the six measurable observables of the first hyperpolarizability tensor. Calibration of such an instrument requires a reference sample dedicated to wavelength conversion. We calibrated our experimental setup by using a quartz-plate sample in a two step procedure: at first the first retarder then the second one. The retardance and ellipticity angle of both retarders were estimated by minimizing a chi(2) function. We estimated the standard deviation of each parameter from noise spreading and performed this calibration procedure for two experimental case studies, i.e., two angular positions of the quartz sample.