Boosting Second Harmonic Generation Efficiency and Nonlinear Susceptibility via Metasurfaces Featuring Split-Ring Resonators and Bowtie Nanoantennas.

This work investigates a metasurface design to achieve remarkable second harmonic generation (SHG) conversion efficiency and enhance effective nonlinear susceptibility using the finite element method. The elements of the designed structure are composed of a rectangular split-ring resonator Ag film, a bowtie-shaped Ag nanoantenna, and a pair of Bi bars that induce nonlinear optical phenomena due to the nonuniform distribution of the electric and magnetic fields within the device surface. The simulation results agree perfectly with the theory and demonstrate outstanding achievements in terms of SHG conversion efficiency (η) and effective nonlinear susceptibility (χeff(2)). Specifically, the metasurface reaches a peak η value of 4.544×10-8 and an effective nonlinear susceptibility of 3.4×104 pm/V. This work presents a novel and versatile design to achieve high η and χeff(2) in an SHG metasurface.

Age-dependent nuclear lipid droplet deposition is a cellular hallmark of aging in Caenorhabditis elegans.

Aging is the major risk factor for several life-threatening pathologies and impairs the function of multiple cellular compartments and organelles. Age-dependent deterioration of nuclear morphology is a common feature in evolutionarily divergent organisms. Lipid droplets have been shown to localize in most nuclear compartments, where they impinge on genome architecture and integrity. However, the significance of progressive nuclear lipid accumulation and its impact on organismal homeostasis remain obscure. Here, we implement non-linear imaging modalities to monitor and quantify age-dependent nuclear lipid deposition in Caenorhabditis elegans. We find that lipid droplets increasingly accumulate in the nuclear envelope, during aging. Longevity-promoting interventions, such as low insulin signaling and caloric restriction, abolish the rate of nuclear lipid accrual and decrease the size of lipid droplets. Suppression of lipotoxic lipid accumulation in hypodermal and intestinal nuclei is dependent on the transcription factor HLH-30/TFEB and the triglyceride lipase ATGL-1. HLH-30 regulates the expression of ATGL-1 to reduce nuclear lipid droplet abundance in response to lifespan-extending conditions. Notably, ATGL-1 localizes to the nuclear envelope and moderates lipid content in long-lived mutant nematodes during aging. Our findings indicate that the reduced ATGL-1 activity leads to excessive nuclear lipid accumulation, perturbing nuclear homeostasis and undermining organismal physiology, during aging.

Intolerance of a non-diffractive extended-depth-of-focus IOL with mini-monovision.

Purpose: The use of a non-diffractive extended-depth-of-focus (EDOF) intraocular lens (IOL) with slight myopia of -0.5 D on the non-dominant eye increases the spectacle independence and has good subjective tolerance with optical phenomena comparable to those of a monofocal IOL. This case report describes the course of a myopic patient who underwent refractive lens exchange, didn't tolerate mini-monovision and received IOL exchange therefore. Observations: A healthy, 62-year-old male with myopia of approximately -5 D underwent refractive lens exchange with a non-diffractive EDOF-IOL on both eyes with slight myopia on the non-dominant left eye (mini-monovision). The operation was performed without any complications, postoperative treatment was due to the clinic's standard procedure. Two weeks postoperative the patient presented with uncorrected distance visual acuity of 0.0 logMAR, a subjective refraction of -0.25/-0.25/142° and corrected distance visual acuity of 0.1 logMAR on the right eye. On the left eye, distance visual acuity was 0.4 logMAR with a subjective refraction of -0.5/-0.75/9° (intended mini-monovision) and corrected distance visual acuity of 0.0 logMAR. Binocular distance visual acuity was 0.0 logMAR. The patient complained about the occurrence of optical phenomena at dim light while driving a car and subjective reduced visual acuity. After an IOL exchange on the left eye with the implantation of the same type of non-diffractive EDOF-IOL aimed for emmetropia, the patient was symptom-free and reported no more subjective complaints. Conclusions: Despite the satisfying subjective and objective visual outcome which is proven in multiple studies, the subjective perception of a mini-monovision with a non-diffractive EDOF-IOL can vary individually. A preoperative assessment of the patient's needs and tolerance of a mini-monovision is crucial for a satisfying postoperative outcome.

Influence of number and position of porcelain specimens in the furnace on flexural strength and translucency

The aim of this study was to investigate the influence of the quantity and positioning of feldspathic ceramic specimens inside the furnace on their flexural strength and translucency. The tested hypotheses were that the arrangement of specimens in the furnance would not influence 1) the translucency or 2) the biaxial strength of the porcelain. Methods: Ninety porcelain specimens were made (1.2 mm thickness and 13.5 mm diameter) and assigned into two main groups (n=15): G1 group - 15 firing cycles containing only one specimen each, always at the center of the refractory; and G5 group - 15 firing cycles containing five specimen each, where one specimen was at the center of the refractory and four specimens positioned equidistantly on the periphery. The translucency test was performed using a spectrophotometer, followed by the flexural strength test, according to ISO 6872:2015. T-student test was performed for both the mechanical and optical obtained data. Results: The flexural strength of the porcelain was not affected by the positioning (center x periphery) of the specimens inside the furnace (p =0.08), but the translucency was affected (periphery > center; p =0.009). Regarding to the number of feldspathic ceramic specimens, the biaxial flexural strength was affected (p =0.025), as well as the translucency (p <0.05). Conclusion: A higher quantity of feldspathic ceramic specimens for each firing cycle decreased its biaxial flexural strength and translucency. Also, specimens positioned at the center of the refractory became less translucent than those positioned at the periphery.

Ray Tracing versus Thin-Lens Formulas for IOL Power Calculation Using Swept-Source Optical Coherence Tomography Biometry.

Purpose: To evaluate the ray tracing method's accuracy employing Okulix ray tracing software and thin-lens formulas to calculate intraocular lens (IOL) power using a swept-source optical coherence tomography (SS-OCT) biometer (OA2000). Methods: A total of 188 eyes from 180 patients were included in this study. An OA-2000 optical biometer was used to collect biometric data. The predicted postoperative refraction based on thin-lens formulas including SRK/T, Hoffer Q, Holladay 1, and Haigis formulas and the ray tracing method utilizing the OKULIX software was determined for each patient. To compare the accuracy of approaches, the prediction error and the absolute prediction error were determined. Results: The mean axial length (AL) was 23.66 mm (range: 19-35). In subgroup analysis based on AL, in all ranges of ALs the ray tracing method had the lowest mean absolute error (0.56), the lowest standard deviation (SD; 0.55), and the greatest proportion of patients within 1 diopter of predicted refraction (87.43%) and the lowest absolute prediction error compared to the other formulas (except to SRK/T) in the AL range between 22 and 24 mm (all P < 0.05). In addition, the OKULIX and Haigis formulas had the least variance (variability) in the prediction error in different ranges of AL. Conclusion: The ray tracing method had the lowest mean absolute error, the lowest standard deviation, and the greatest proportion of patients within 1 diopter of predicted refraction. So, the OKULIX software in combination with SS-OCT biometry (OA2000) performed on par with the third-generation and Haigis formulas, notwithstanding the potential for increased accuracy in the normal range and more consistent results in different ranges of AL.

Effects of milling method and artificial ageing on optical properties of high translucent zirconia for chairside restorations.

OBJECTIVES: This study aimed to evaluate the optical properties of highly translucent 5 mol% yttria, partially stabilised monolithic zirconia, and 3 mol% yttria-stabilised tetragonal zirconia after their subjection to different milling methods and artificial ageing. METHODS: Two types of pre-shaded zirconia materials were used: inCoris TZI C and Katana STML. A total of 120 specimens were categorised according to the milling method (dry or wet-milling) and the solution used for milling (fresh distilled water or impregnated water with residues of CAD/CAM ceramic materials). The translucency and contrast ratios of all specimens were calculated after they were subjected to sintering and accelerated ageing. The material phase composition was tested before and after ageing, using X-ray diffraction analysis to evaluate T-M phase transformation. Data were statistically analysed via a three-way analysis of variance between the subject factors, the material and milling method, and the within-subject factor, ageing. The analysis of covariance model was used to analyse the changes in translucency and contrast ratio between baseline and ageing, with statistical significance set at p < 0.05. RESULTS: Katana STML and inCoris TZI C showed the highest translucency when dry-milled (21.9 ± 1.4, and 11.8 ± 0.7, respectively), and the lowest when milled with used impregnated water (5.4 ± 1.2 and 10.7 ± 1.3, respectively). Wet-milling using impregnated water, should be avoided owing to the saturation of alumina particles. Accelerated ageing resulted in the same pattern for both materials. Significance Dry milling of highly translucent zirconia can result in higher translucency and lower contrast ratio values.

Using a professional DSLR camera to measure total shrinkage of resin composites

Abstract This study evaluated the optical method for measuring free total shrinkage using a Digital Single Lens Reflex (DSLR) camera. Eight composites were evaluated, conventional, bulk fill and low-shrinkage: Z100 (3M Oral Care), Gradia Direct Anterior (GC corporation), Spectra Smart (Dentsply), Filtek Z350 XT (3M Oral Care), Aura Bulk Fill (SDI), Vittra APS (FGM), Opus Bulk Fill APS (FGM), and Beautifil II LS (Shofu Inc.). The samples (6 mm diameter and 1.5 mm thick, n = 10) were placed on a polyvinylsiloxane impression material. An image of the uncured sample was captured using a DSLR camera with 105 mm macro lens and a ring flash. Samples were light cured with a 700 mW/cm2 LED light-cure unit for 40s. Post-polymerization images were captured at 2, 10 and 60 min. Projected circumferential areas of the specimens were drawn using the ImageJ software. Volumetric total shrinkage was calculated from the ratio of the areas obtained from pre- and post-curing. Results were analyzed using One-way ANOVA (α = 0.05) and Tukey test. Volumetric total shrinkage values were significantly different among the composite materials (p < .001). The volumetric shrinkage (%) mean and results of Tukey test at 60 min were: Z100: 3.45±0.30 (A); Gradia Direct Anterior: 3.00 ± 0.23 (B); Spectra Smart 2.89 ± 0.35 (B); Filtek Z350 XT: 2.65 ± 0.37 (BC); Aura Bulk Fill: 2.42 ± 0.25 (CD); Vittra APS: 2.14 ± 0.35 (DE); Opus Bulk Fill APS: 1.91 ± 0.24 (E); Beautifil II LS: 1.18 ± 0.16 (F). The optical method using a DSLR camera, was suitable for total shrinkage evaluation and will allow assessment of total shrinkage without the need for specialized equipment.

Effect of Staining and Aging on Translucency Parameter of CAD-CAM Materials.

OBJECTIVES: To evaluate different intervals of exposure to staining solutions and artificial aging on translucency parameter (TP00) of CAD-CAM materials. MATERIAL AND METHODS: One millimeter thick square-shaped specimens (N = 288) were cut from Cerasmart (CS), IPS e.max (IE), Lava Ultimate (LU), Shofu HC (SH), Vita Enamic (VE), and Vita Suprinity (VS) and were divided into laboratory and chairside polishing. Reflection wavelength spectra, CIE D65 standard illuminant, 2 ° standard observer, SCI, UV included, SAV aperture, 6 mm diameter, were recorded at 10 nm sensitivity against white and black calibration tiles using a benchtop spectrophotometer. Subsequently, they were converted into CIEDE 2000 TP00. After baseline measurements (T0), the specimens were divided as follows (n = 8): staining in coffee (C) and wine (W), for 60 (T1) and 120 hours (T2), and accelerated artificial aging (A). Artificial aging (ISO 4892-2 standard) was performed in two cycles of 150 KJ/m2, for T1 and T2, respectively. TP measurements were repeated at T1 and T2. Data of TP00 retention were submitted to analysis of variance and Fisher's PLSD multiple comparison test (α=0.05). RESULTS: Fisher's PLSD critical differences among materials, time intervals and staining/aging were 0.16, 0.11 and 0.11, respectively. SH showed the highest TP00 followed by LU > CS > IE = VS > VE. For all time intervals, the lowest TP00 retention was observed with C. W, and A presented similar values. CONCLUSIONS: Translucency Parameter was a time and staining/aging-dependent material. In majority of cases, it decreased upon staining/aging.

Fatigue behavior and colorimetric differences of a porcelain-veneered zirconia: effect of quantity and position of specimens during firing.

PURPOSE: To evaluate the influence of quantity and positioning of veneered zirconia specimens during firing of porcelain on their fatigue performance and colorimetric differences. METHODS: Bilayer discs (Ø=15 mm) were made, following ISO 6872 guidelines, using a Y-TZP core (yttria-stabilized tetragonal zirconia polycrystal ceramic; VITA In-Ceram YZ) and a feldspathic veneering material (VITA VM9), being both layers with 0.7 mm thickness. Y-TZP discs were sintered, the veneering material was applied over it, and the bilayer specimens were fired according to two factors (n=20): 'quantity' (1 or 5 samples per firing cycle; G1 and G5 groups respectively) and 'positioning' of the specimens inside the furnace (center or periphery of the refractory tray; G5C and G5P groups, respectively). The CIEL*a*b* parameters were recorded with a spectrophotometer and the color difference (ΔE 00 ) and translucency (TP 00 ) were calculated using CIEDE2000 equations. The step-stress fatigue test was performed with the veneer facing down (region of tensile stress concentration), 10 Hz frequency, initial tension of 20 MPa for 5,000 cycles, followed by steps of 10,000 cycles using a step size of 10 MPa, up to 100 MPa; data from strength and number of cycles for failure were recorded for statistical analysis. RESULTS: Unacceptable color differences (ΔE 00 >1.8) were observed comparing G5C vs. G1 (quantity) and G5C vs. G5P (positioning), meanwhile translucency parameters were not affected. Besides, only the 'quantity' factor influenced the fatigue performance (G1>G5C). None of the tested specimens survived beyond 90N and/or 75000 cycles. CONCLUSIONS: The quantity and position of the specimens during firing influence the final color of porcelain-veneered zirconia, and firing one specimen per cycle improved the fatigue performance of the bilayer system.

Effect of A Rapid-Cooling Protocol on the Optical and Mechanical Properties of Dental Monolithic Zirconia Containing 3-5 mol% Y2O3.

Many attempts have been made to improve the translucency of zirconia in dentistry. The purpose of this study was to evaluate the effect of a rapid-cooling heat treatment on the optical and mechanical properties of dental monolithic zirconia. Zirconia containing 3, 4, and 5 mol% Y2O3 were sintered, sectioned, and polished. The specimens were rapidly cooled from high temperature inducing a diffusionless cubic-to-metastable tetragonal (t') phase transformation. The changes in L*a*b* color coordinates, translucency parameter (TP), and total transmittance (T%) were measured. Three-point bending strength, Vickers hardness, and indentation fracture toughness tests were performed. Quantitative phase analyses were carried out by X-ray diffraction with Rietveld refinement. Scanning electron microscopy (SEM) images were obtained. With increasing Y2O3 contents, TP and T% values increased while strength and toughness decreased. The Rietveld analysis showed that the amount of t'-phase increased after rapid-cooling and annealed 5Y-partially stabilized zirconia (PSZ) contained the highest amount of t'-phase (64.4 wt%). Rapid-cooling improved translucency but the translucency of annealed 5Y-PSZ did not approach that of lithium disilicate glass-ceramic. Rapid-cooling decreased flexural strength significantly, being 306.1 ± 61.8 MPa for annealed 5Y-PSZ. SEM revealed that grains tended to get larger after rapid-cooling. A rapid-cooling treatment can produce t'-phase which can contribute to an increase in translucency but has a negative effect on the mechanical properties of zirconia.

[Interactive training using a smartphone video retinoscope : Video article]. / Interaktives Training mittels Smartphone-Videoskiaskop : Videobeitrag.

BACKGROUND: The purpose of this project is to apply and optimize a conventional streak retinoscope connected to a smartphone in order to demonstrate and record retinoscopic techniques, related phenomena, typical examination errors in a standardized environment and to use this set-up to produce instructional video clips. The videos enhance and improve the trainer-trainee interaction by instantly visualizing the optical phenomena on the integrated monitor of the retinoscope. METHODS: A smartphone (iPhone 6, Apple, Cupertino, CA, USA) is reversibly connected to a Beta 200 streak retinoscope (HEINE, Herrsching, Germany) via a coupling plate. This allows visualization of the optical phenomena on the screen of a smartphone, which can also be used for recording. To stabilize the recording conditions, the battery handle of the retinoscope is connected to a 3-axis gimbal (Zhiyun Crane Plus, Zhiyun, Guilin, China). In this way the examination unit can be rotated around all axes without any relevant changes in distance. A software-based post-processing (Adobe Premiere Pro CC 2017, Adobe Systems Software Ireland Limited, Dublin. Ireland) of the video sequences almost completely eliminates motion artefacts. RESULTS: With the aforementioned experimental set-up, the following optical phenomena have so far been documented as videos, which are available online: flashing point, with-movement and against-movement, scissors phenomenon, cataract, astigmatic ametropia and refraction scotoma. CONCLUSION: For the first time smartphone video retinoscopy allows optical phenomena to be presented to the examiner (trainee) and trainer at the same time and to produce realistic instructional videos of high quality with comparatively little effort.

Colour stability and surface properties of high-translucency restorative materials for digital dentistry after simulated oral rinsing.

High-translucency restorative materials are commonly used in the restoration of anterior teeth where aesthetics is a critical factor. In this in vitro study, the impact of mouthwash on the colour stability and surface characteristics of high-translucency computer-aided design and computer-aided manufacturing (CAD-CAM) dental restorative materials was evaluated. Two-hundred specimens were fabricated from five high-translucency CAD-CAM materials: a resin nano ceramic; a polymer-infiltrated ceramic network; a feldspathic ceramic; a lithium disilicate glass ceramic; and high-translucency zirconia. Each group of ceramic specimens was then divided into four subgroups: conventional mouthwash (LISTERINE); whitening mouthwash (LISTERINE Healthy White); chlorhexidine gluconate; and distilled water. Oral rinsing was simulated at 100 rpm for 180 h, representing 15 yr of clinical simulation. The specimens were then evaluated for colour, translucency, gloss, roughness, and surface morphology. Two-way ANOVA and linear mixed models were used for intergroup comparisons (α = 0.05). The polymer-infiltrated ceramic network and feldspathic ceramic became brighter, more opaque, less glossy, and rougher after rinsing with the whitening mouthwash. The long-term use of specific mouthwashes can cause deterioration of the optical and surface properties of high-translucency CAD-CAM dental restorations.

Influence of shading technique on mechanical fatigue performance and optical properties of a 4Y-TZP ceramic for monolithic restorations.

This study aimed to evaluate the effect of shading procedures on the fatigue performance and optical properties of an yttria-stabilized tetragonal zirconia polycrystal ceramic (4Y-TZP - stabilized by 4 mol% Y2O3). Disc-shaped specimens were produced at pre-sintered stage and randomly allocated into 5 groups (n=15) considering the shading technique: Ctrl (no pigmentation); Brush 1× and Brush 3× (brushing on 1 or 3 applications, respectively); Immer 2min and Immer 4min (immersion for 2 or 4 min, respectively). Following each pigment application, the specimens were dried in accordance with the manufacturers' guidelines (15 min in a stove at 70 °C) and sintered in a specific furnace. Biaxial flexural fatigue test followed a step-stress approach (initial strength: 200 MPa; step-size: 25 MPa; 10.000 cycles/step; frequency: 20 Hz). Optical measurements were conducted in a spectrophotometer following the CIEDE2000 parameters. Roughness, topography, crystalline grain size, crystalline phase content and fractography analysis were also performed. The flexural fatigue strength (FFS) and the number of cycles to fracture (CFF) were statistically affected by pigmentation techniques (mean FFS in MPa/mean CFF): Ctrl (446.7/105,619) > Brush 1 × (436.7/102,854) ≥ Brush 3 × (405.0/89,962) ≥ Immer 2 min (395.0/85,103) ≥ Immer 4 min (383.3/81,382), although the exposure intensity (increase in number of applications or in application time) to the pigment had no effect (Brush 1 × = Brush 3 × ; Immer 2 min = Immer 4 min). Regarding optical properties, shading techniques similarly affected translucency and opalescence parameters, regardless of the exposure intensity to the pigment (Brush 1 × = Brush 3 × = Immer 2 min = Immer 4 min > Ctrl), whereas the exposure intensity to the pigment only promoted relevant alterations in the color change parameter (ΔE00) for the brushing technique (Brush 3 × > Brush 1 × ). No difference was observed in crystalline phase content, topographic pattern or roughness, although an increase in the zirconia grain size could be detected. Thus, the shading technique might affect the fatigue behavior and promote optical changes in a 4Y-TZP ceramic.

Effects of substrate, ceramic thickness, translucency, and cement shade on the color of CAD/CAM lithium-disilicate crowns.

OBJECTIVE: The aim of this in vitro study was to evaluate the effects of substrate colors, different levels of ceramic thickness and translucency, and cement shades on the color difference from a reference color of lithium-disilicate crowns. MATERIALS AND METHODS: A premolar tooth preparation was made on a study model for 1.0 and 1.5 mm thick full-ceramic crowns. Digital impressions were taken (3Shape TRIOS) and crowns designed in a CAD program (DentalDesigner). Shade A1 crowns were milled (Everest, Kavo) from high-translucency (HT) and low-translucency IPS e.max (Ivoclar Vivadent) blocks. Twelve substrates were made of different colors and materials (Natural Die Material, Co-Cr, zirconia, and gold-colored alloy). Three different shades of try-in pastes were used to simulate the effect of cements (Variolink Esthetic try-in paste; Ivoclar). Shade measurement was done three times for each crown by a spectrophotometer (VITA Easyshade Advance); averages were compared to a reference crown (A1, HT, 1.5 mm, ND2 abutment, neutral try-in paste) with ΔE00 (CIEDE2000, according to the CIE latest standard) calculated. RESULTS: All the examined parameters influenced the ΔE00 of the crowns. The weakest effect was exerted by the try-in paste. CONCLUSIONS: All examined parameters influenced the final color of e.max CAD lithium-disilicate ceramic crowns. CLINICAL SIGNIFICANCE: Matching the shade of ceramic crowns to the natural tooth color is a great challenge in dentistry. To meet patients' increasing esthetical expectations, CAD/CAM methods are very popular for full-ceramic crowns. However, several factors such as the shade of the abutment, luting cement color, ceramic thickness, and translucency may influence the final color. Our objective was to measure the optical effect of these factors on the final shade of CAD/CAM lithium-disilicate ceramic crowns.

Utilizing the optical properties of composite resins to improve esthetics: a layering technique for anterior restorations.

A comprehensive knowledge of the optical properties of composite resins is essential to achieving optimal results in direct anterior restorations. This case report describes an anterior composite resin restoration fabricated with a layering technique and explains how to use a simple photographic method to verify that the desired optical effects are reproduced. A Class IV restoration was completed on a maxillary central incisor with the help of a silicone guide. An esthetic result was achieved through careful color examination as well as material selections that were based on knowledge of the translucency, opacity, and fluorescence of the chosen direct composite resins. The approach of combining a composite resin designed for bleached teeth with highly opalescent and translucent resins as well as matching the natural dental anatomy provided excellent esthetic results. The suitable reproduction of optical characteristics was confirmed by increasing the contrast of the final photograph, which highlighted the translucency achieved in the area of the mamelons.

[Hyperopic Laser-in-situ-Keratomileusis after trifocal intraocular lens implantation : Aberration-free femto-Laser-in-situ-Keratomileusis treatment after implantation of a diffractive, multifocal, toric intraocular lens-case analysis]. / Hyperope Laser-in-situ-Keratomileusis nach trifokaler Intraokularlinsen-Implantation : Aberrationsfreie Femto-Laser-in-situ-Keratomileusis-Behandlung nach Implantation einer diffraktiven, multifokalen, torischen Intraokularlinse ­ Fallanalyse.

A 52-year-old highly myopic female patient was implanted with a multifocal, diffractive, toric intraocular lens because of the wish to be independent of eyeglasses. Despite high-quality, extensive preoperative examinations, a hyperopic refractive error remained postoperatively, which led to the patient's dissatisfaction. This error was treated with Laser-in-situ-Keratomileusis (LASIK). After corneal LASIK treatment and implantation of a diffractive toric multifocal intraocular lens the patient showed a good postoperative visual result without optical phenomena.

Color changes caused by reduction on the dentin shade composite thickness

Resumo Este estudo objetivou determinar o limiar de redução na espessura do compósito de cor da dentina necessário para resultar em mudanças de cor perceptíveis e aceitáveis em restaurações simuladas. Três sistemas de compósitos (Charisma Diamond, IPS Empress Direct e Filtek Z350 XT) foram avaliados utilizando corpos-de-prova cilíndricos construídos com cores de dentina e esmalte. A opacidade dos compósitos foi avaliada usando cilindros de 1,0 mm de espessura sobre fundo preto e branco. Uma cor inicial padrão foi estabelecida para cada sistema pela combinação de esmalte de 1,0 mm de espessura com 3,0 mm de cilindros de resina na cor de dentina sobre um fundo escuro (n = 9). Em seguida, foram calculadas as alterações de cor (∆E00) causadas por reduções sequenciais de 0,1 mm nos cilindros de resina na cor de dentina. Mudanças de opacidade em cilindros na cor de dentina e cilindros combinados de esmalte e dentina foram também avaliadas após cada redução de espessura. Regressão polinomial foi realizada com médias de ∆E00 em função da espessura dos cilindros na cor de dentina; e os limiares de aceitabilidade (∆E00 = 1,77) e perceptibilidade (∆E00 = 0,81) foram calculados. Regressões lineares também foram realizadas para ∆E00 em função da opacidade dos cilindros na cor de dentina e do par combinado de cilindros de esmalte-dentina. Com exceção da Charisma, os compósitos de esmalte apresentaram menor opacidade do que os de dentina. Alterações de cor perceptíveis e aceitáveis foram observadas quando os cilindros na cor de dentina foram mais finos que 2,0-2,4 mm e 1,1-1,4 mm, respectivamente. Nenhuma diferença entre os sistemas compostos foi observada. Em conclusão, reduções no compósito de dentina menor que 0,6 mm não produziu mudanças de cor perceptíveis, e mudanças de cor clinicamente significantes apenas foram observadas com reduções maiores que 1,6 mm.

Abstract This study determined the reduction threshold in thickness of the dentin shade composite necessary to result in perceptible and acceptable color changes on simulated restorations. Three composite systems (Charisma Diamond, IPS Empress Direct, and Filtek Z350 XT) were evaluated using cylinder-shaped specimens built-up with dentin and enamel shades. The opacity of the composites was assessed using 1.0 mm thick specimens over black and white backgrounds. A baseline color was established for each system by combining 1.0 mm thick enamel shade with 3.0 mm of dentin shade cylinders over a dark background (n = 9). Then, the color changes (∆E00) caused by sequential 0.1 mm reductions on dentin shade cylinders were calculated. Opacity changes on dentin shade cylinders and combined enamel-dentin pair cylinders were also assessed after each thickness reduction. Polynomial regression was performed with averages of ∆E00 as a function of thickness of dentin shade cylinders; and acceptability (∆E = 1.77) and perceptibility (∆E = 0.81) thresholds were calculated. Linear regressions were also performed for ∆E00 as function of opacity of dentin shade cylinders and combined enamel-dentin pair of cylinders. Except for Charisma, enamel shades presented the lowest opacity than dentin one. Perceptible and acceptable color changes were observed for dentin shade cylinders thinner than 2.0-2.4 mm and 1.1-1.4 mm, respectively, were used. No difference among the composite systems was observed. In conclusion, reductions on dentin shade composite lower than 0.6-mm did not yield perceptible color changes, and clinically significant color changes only were observed within reductions higher than 1.6-mm.

[Visual improvement by aberration-free excimer laser retreatment : Therapy after combined photorefractive keratectomy and keratome laser in situ keratomileusis treatment]. / Visusverbesserung durch eine aberrationsfreie Excimerlaser-Nachbehandlung : Therapie nach kombinierter photorefraktiver Keratektomie und Keratom-Laser-in-situ-Keratomileusis-Behandlung.

A 23-year-old male patient presented with reduced visual acuity of the right eye, along with halos and starbursts in both eyes after a one-stage tissue-saving treatment, a combination of myopic photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). After an extensive preliminary examination and analysis of the examination results, aberration-free LASIK retreatment for reducing astigmatism and enlargement of the optical zone with an excimer laser was performed on the right eye. The visual performance and the subjectively perceived optical quality improved postoperatively.

Effect of active evaluation on the detection of negative dysphotopsia after sequential cataract surgery: discrepancy between incidences of unsolicited and solicited complaints.

PURPOSE: To evaluate the incidence of negative dysphotopsia after sequential cataract surgery. METHODS: Retrospective cohort study. The incidence of negative dysphotopsia was assessed by retrospective reviewing of medical records and interviews with patients between 2 and 4 months after sequential cataract surgery. Inclusion criteria were uncomplicated surgery, postoperative corrected distance visual acuity (CDVA) ≥20/25 Snellen and the absence of ocular comorbidity. The majority of intra-ocular lens (IOL) implants were one-piece AcrySof SN60WF (161 eyes). Other IOLs (29 eyes) were toric (SN6AT3-6), spherical (SN60AT), three-piece (MN60MA) and multifocal (ReSTOR SN6AD1, PanOptix TFNT00 and Finevision Micro F trifocal). RESULTS: The study population was comprised of 95 patients with a mean age of 72 ± 10 years. Unsolicited complaints of negative dysphotopsia were reported by eight patients (8%), and two of them had a resolution of symptoms within 1 month of follow-up. Eighteen patients (19%) reported negative dysphotopsia at the time of the interview. Two patients reported bothersome negative dysphotopsia, and one of them was successfully treated with implantation of a supplementary IOL in the ciliary sulcus. Patients with negative dysphotopsia were younger than patients without dysphotopsia (p = 0.045) and had shorter axial eye length (p = 0.04), a tendency for higher IOL power (p = 0.09) and a higher CDVA (p = 0.001). CONCLUSION: The incidence of unsolicited negative dysphotopsia after sequential cataract surgery appears to be a substantial underestimation of complaints identified in active interviewing. Although symptoms are not bothersome in the majority of cases, some patients with undiagnosed severe negative dysphotopsia may benefit from reassurance or secondary treatment.

Photoelastic and finite element stress analysis reliability for implant-supported system stress investigation

Aim: To compare the reliability between photoelastic and finite element (FE) analyses by evaluating the effect of different marginal misfit levels on the stresses generated on two different implant-supported systems using conventional and short implants. Methods: Two photoelastic models were obtained: model C with two conventional implants (4.1×11 mm); and model S with a conventional and a short implant (5×6 mm). Three-unit CoCr frameworks were fabricated simulating a superior first pre-molar (P) to first molar (M) fixed dental prosthesis. Different levels of misfit (µm) were selected based on the misfit average of 10 frameworks obtained by the single-screw test protocol: low (<20), medium (>20 and <40) and high (>40). Stress levels and distribution were measured by photoelastic analysis. A similar situation of the in vitro assay was designed and simulated by the in silico analysis. Maximum and minimum principal strain were recorded numerically and color-coded for the models. Von Mises Stress was obtained for the metallic components. Results: Photoelasticity and FE analyses showed similar tendency where the increase of misfit generates higher stress levels despite of the implant design. The short implant showed lower von Mises stress values; however, it presented stresses around its full length for the in vitro and in silico analysis. Also, model S showed higher µstrain values for all simulated misfit levels. The type of implant did not affect the stresses around pillar P. Conclusions: Photoelasticity and FEA are reliable methodologies presenting similarity for the investigation of the biomechanical behavior of implant-supported rehabilitations