Scanning Laser Technique Research Articles

Performance of two laser motion modes versus conventional orthodontic ceramic brackets debonding technique on enamel surface topography.

The risk of enamel deterioration that frequently coexists with debonding of orthodontic teeth brackets elevates the mandate for finding an optimum approach for debonding them without harmful effects. This in-vitro study is intended to compare the effects of two different laser modes (scanning and circular) and a conventional method on the enamel surface after debonding orthodontic brackets. 66 extracted premolars were assigned into 3 groups. After that, light-cure composite resin was used to attach the ceramic brackets to the teeth. Amongst the test groups, Group I: specimens that were debonded using conventional debonding using pliers; Group 2: specimens that were debonded using Er, Cr: YSGG laser applications using the circular motion method; and Group 3: specimens that were debonded using Er, Cr: YSGG laser applications using the scanning motion method. Adhesive Remnant Index (ARI) assessment, intra-pulpal temperature increase, enamel surface roughness after polishing, and assessment of the microstructure of enamel were carried out with scanning electron microscopy. The gathered information was examined statistically. The conventional debonding method had a significantly higher proportion of adhesive remnant index (ARI) scores of 2 and 3 in comparison to the circular (p < .004) and scanning laser groups (p < .001). There was no significant difference in ARI scores between the circular and scanning laser groups (p > .05). Moreover, the circular and scanning laser debonding methods resulted in a significantly higher proportion of Enamel Surface Roughness (ESR) scores of 0 and a lower proportion of ESR scores of 3 compared to the conventional technique group (p < .001). However, there was no significant difference in ESR scores between the circular and scanning laser methods (p = .945). Lastly, the average intra-pulpal temperature was significantly higher in the circular laser group (1.9 ± 0.5 ) compared to the scanning laser group (0.9 ± 0.2) with p < .001. Er, Cr: YSGG laser irradiation is a tool that shows promise for debonding ceramic brackets with minimal harm to the enamel surface. The scanning laser technique is more desirable due to the lower intra-pulpal temperature increase.

Bulk properties of honeycomb lattices of superconducting microwave resonators

We have realized different honeycomb lattices for microwave photons in the 4 to 8 GHz band using superconducting spiral resonators. Each lattice comprises a few hundred sites. Two designs have been studied, one leading to two bands touching at the Dirac points and one where a gap opens at the Dirac points. Using a scanning laser technique to image the eigenmodes of this new type of photonic lattices, we are able to reconstruct their band structure. The measured bands are in excellent agreement with ab initio models that combine numerical simulations of the electromagnetic properties of the spiral resonator and analytical calculations.

Assessment of vitreous haze using ultra-wide field retinal imaging.

BackgroundConventional fundus imaging has been used to assess vitreous haze (VH) in patients with uveitis. Ultra-wide field (UWF) retinal imaging that uses scanning laser technology has not been evaluated for the detection of VH. This pilot study evaluates the ability of UWF imaging in detecting VH.Patients with intermediate, posterior, or panuveitis were examined to assess the level of VH using slit-lamp biomicroscopy. Colored fundus images were acquired using a Carl Zeiss FF450 camera. The same photographer obtained fundus images of the same eyes during the same visit by Optos UWF P200Tx retinal camera. Two graders independently analyzed UWF fundus images for presence or absence of VH, without quantifying the degree of VH using any scale. The images were analyzed using the composite red plus red-free wavelengths utilized by the Optos UWF camera and by using each wavelength exclusively. These findings were compared to clinical detection of VH and detection of VH using conventional fundus photography.ResultsNinety-two eyes were included in the study. For composite UWF images, sensitivity was 0.27, specificity was 0.88, PPV was 0.31, NPV was 0.86, positive LR was 2.25, and negative LR was 0.83. For the conventional Zeiss images, sensitivity was 0.5, specificity was 0.84, PPV was 0.33, NPV was 0.91, positive LR was 3.13, and negative LR was 0.6.Agreement between the composite UWF and Zeiss techniques was substantial with k = 0.64. Inter-observer agreement for composite UWF images was also substantial with k = 0.65. Inter-observer agreement for Zeiss images was moderate with k = 0.471. Intra-observer agreement for both imaging modalities was substantial with a composite UWF k = 0.76 and Zeiss k = 0.7.ConclusionsUWF fundus imaging using scanning laser technique may be used to assess VH and employed in the management of intermediate, posterior, and panuveitis.

Presbyopia and the optical changes in the human crystalline lens with age.

Lenses from 27 human eyes ranging in age from 10 to 87 years were used to determine how accommodation and age affect the optical properties of the lens. A scanning laser technique was used to measure focal length and spherical aberration of the lenses, while the lenses were subjected to stretching forces applied through the ciliary body/zonular complex. The focal length of all unstretched lenses increased linearly with increasing age. Younger lenses were able to undergo significant changes in focal length with stretching, whereas lenses older than 60 years of age showed no changes in focal length with stretching. These data provide additional evidence for predominantly lens-based theories of presbyopia. Further, these results show that there are substantial optical changes in the human lens with increasing age and during accommodation, since both the magnitude and the sign of the spherical aberration change with age and stretching. These results show that the optical properties of the older presbyopic lens are quite different from the younger, accommodated lens.

Imaging of retinal autofluorescence in patients with age-related macular degeneration.

Several studies have demonstrated an accumulation of autofluorescent materials in the retinal pigment epithelium (RPE) with increasing age. Histologic analysis revealed that lipofuscin is the most potential fluorescent substance in the aging RPE. Therefore, it has been speculated that lipofuscin precedes the presence of drusen and the development of age-related macular degeneration (ARMD). A scanning laser ophthalmoscope was used to visualize autofluorescence in the fundus of patients with early ARMD. The digital recordings were analyzed offline with a digital image analyzing system. In 85 of 103 patients, focal areas of increased autofluorescence were visible. Areas of hyperpigmentation at the level of the RPE showed increased autofluorescence in all cases, whereas areas of depigmentation demonstrated decreased autofluorescence. Patients with ARMD demonstrated focal accumulation of fluorescent material most likely lipofuscin. Thus, the scanning laser technique combined with an image analyzing system may help to identify eyes at risk for developing exudative ARMD.

Curvature changes during thermal cycling of a compositionally graded NiAl 2O 3 multi-layered material

The elastoplastic deformation characteristics of a plasma-sprayed, tri-layered composite plate subjected to thermal cycling from 20°C up to 800°C were studied experimentally and numerically. The tri-layered solid comprised polycrystalline Ni and Al 2O 3 outer layers and a 2.2 mm thick compositionally graded NiAl 2O 3 composite interlayer (FGM) wherein the composition varied approximately linearly along the layer thickness. The experiments involved in situ and ex situ measurements, employing a scanning laser technique, of the changes in the overall curvature of the unconstrained plate arising from the thermal mismatch between the constituent phases. The variations of curvature, accumulated plastic strains and thermal stresses at different locations in the layered solid were also assessed numerically with the aid of available continuum formulations, and the numerical predictions were compared with experiments, wherever appropriate. It is shown that when only small plastic strains exist in the Ni layer or in the Ni-rich end of the FGM layer, known formulations are capable of providing approximate predictions of the cyclic variations in curvature, the onset of plasticity and some features of the initiation of cracking (and its location). We also examine possible sources of error in the experimental measurements of curvature and in the interpretation of thermally induced deformation due to some processing conditions.

In vitro changes in back vertex distance of chick and pigeon lenses: Species differences and the effects of aging

We have used a scanning laser technique to measure in vitro changes in back vertex distance of chick and pigeon lenses. Enucleated eyes were dissected, leaving the lens naturally suspended by the ciliary body and intraocular muscles. Ray tracing techniques were used to measure the resting back vertex distance of the lenses by passing a laser beam through the lens and scanning it across the pupillary aperture. The pupil diameter was measured videographically. The measurements were repeated while the intraocular muscles were pharmacologically stimulated with increasing concentrations of either nicotine or carbachol. Drug stimulation caused changes in pupil diameter and changes in the back vertex distance of the lenses. These experiments were conducted on the eyes of young chicks, young pigeons, and on the eyes of three pigeons older than 10 yr. The lenses from the eyes of the old pigeons had the greatest resting back vertex distance, followed by those of the young pigeons and finally those of the young chicks. Lenses from the eyes of young chicks and young pigeons underwent similar drug-induced changes in back vertex distance, but the lenses from old pigeon eyes showed an almost complete absence of such changes. Further, we demonstrated that, just as in the chick eye, lenticular changes in pigeon eyes are due to a contraction of the iris muscle. This is evident because after the iris has been removed the lens undergoes no change in back vertex distance during stimulation. We conclude with a discussion of the lenticular accommodative ability of the pigeon eye with reference to the recently reported accommodative mechanism of the chick eye and a comparison of chick and pigeon iris morphology.

Perifoveal microcirculation with non-insulin-dependent diabetes mellitus

Fluorescein angiograms were performed to evaluate perifoveal capillary blood velocities (v), capillary density (perifoveal intercapillary areas: PIA) and the foveal avascular zone (FAZ) by means of the scanning laser technique (SLO-101 Rodenstock). The angiograms were digitally stored and the data quantified off-line with an image analyzing system (IBAS). In the present study 46 patients with non-insulin-dependent diabetes mellitus (NIDDM) were examined and their data compared with that of 31 healthy volunteers. The perifoveal capillary flow velocity of the NIDDM subjects (v = 2.33 +/- 0.36 mm/s) was significantly (P < 0.01) decreased as compared to healthy subjects (v = 2.86 +/- 0.41 mm/s). The perifoveal intercapillary areas in the foveal avascular zone were significantly increased in patients with NIDDM (PIA = 10029 +/- 3402 microns2; FAZ = 0.415 +/- 0.272 mm2) as compared with healthy subjects (PIA = 3965 +/- 467 microns2; FAZ = 0.221 +/- 0.071 mm2). These data suggest the possibility that a decrease in perifoveal capillary blood velocities in combination with decreased capillary density (enlarged PIA) and an enlargement of the foveal avascular zone may occur in patients with NIDDM. The determination of these parameters could help in monitoring the progress of diabetic retinopathy and diabetic maculopathy.

Retinal microcirculation in patients with diabetes mellitus: dynamic and morphological analysis of perifoveal capillary network.

The new scanning laser technique allows one to quantify the retinal microcirculation. A digital image analysing system was used to study capillary blood flow velocities and morphological parameters of perifoveal intercapillary areas and foveal avascular zones in normal and diabetic subjects. Diabetic patients showed a significant reduction in capillary blood cell velocities in comparison with normal subjects. Perifoveal intercapillary areas and foveal avascular zones were significantly increased in all stages of diabetic retinopathy, and both parameters increased with progressing diabetic retinopathy. Significant changes in the perifoveal intercapillary areas were observed between normal subjects and patients with no retinopathy.

Retinal Capillary Blood Flow Measurement with a Scanning Laser Ophthalmoscope Preliminary Results

AbstractThe scanning laser technique in combination with digital image analysis allows direct objective measurement of flow velocities in perimacular capillaries. In addition, the complete macular network of capillaries can be observed. By means of digital frame-to-frame picture analysis of digital recordings, blood flow velocities and morphologic data have been measured. The mean flow velocity in perimacular capillaries observed with the scanning laser ophthalmoscope in healthy subjects (n = 21) amounted to 3.28 ± 0.45 mm/second. In patients (n = 13) with diabetes mellitus (no or background retinopathy), the mean flow velocity was significantly reduced (2.89 ± 0.57 mm/seconds) compared with healthy subjects. Morphologic data of the perifoveal capillary bed showed a significant reduction of capillaries in patients with diabetes mellitus when compared with healthy subjects.

Boundary Conditions and Spatial Variations Associated with the Dynamic Modes of Josephson Tunnel Junctions

The Dynamic modes of Josephson Tunnel junctions have been investigated by the scanning laser technique and numerical simulations. The results clearly demonstrate the existence of the vortex mode and electromagnetic cavity mode which have distinctly different dc current distributions. The appropriate boundary condition used for calculations to describe our junctions was found to have the bias current fed from the edges.

A lecture on lenses

Lenses from 27 human eyes ranging in age from 10 to 87 years were used to determine how accommodation and age affect the optical properties of the lens. A scanning laser technique was used to measure focal length and spherical aberration of the lenses, while the lenses were subjected to stretching forces applied through the ciliary body/zonular complex. The focal length of all unstretched lenses increased linearly with increasing age. Younger lenses were able to undergo significant changes in focal length with stretching, whereas lenses older than 60 years of age showed no changes in focal length with stretching. These data provide additional evidence for predominantly lens-based theories of presbyopia. Further, these results show that there are substantial optical changes in the human lens with increasing age and during accommodation, since both the magnitude and the sign of the spherical aberration change with age and stretching. These results show that the optical properties of the older presbyopic lens are quite different from the younger, accommodated lens.