Effects of polishing procedures on optical parameters and surface roughness of composite resins with different viscosities.

The aims of this study were to evaluate the optical properties of flowable and injectable composites after polishing, such as translucency (translucency parameter [TP], TP00), opalescence (OP-BW), chroma (C*ab), refractive index (RI), and change in surface roughness (Ra, Rz). Ninety disc-shaped samples were prepared from micro-hybrid, flowable, and injectable composites and divided into 3 groups according to the polishing systems (n=10). The RI was measured with an Abbe refractometer, and optical measurements were performed with a spectrophotometer. The surface roughness was measured with a two-dimensional profilometer. Data were analyzed with the generalized linear model method and two-way analysis of variance. The results showed that the polishing procedure did not significantly impact the RI (p=0.987). Injectable composite had the highest translucency (TP=28.67; TP00=13.49) and opalescence (OP-BW=13.11); showed the lowest C*ab value (17.95). Also, the effects of the composite type and polishing procedure on surface roughness were statistically significant (p=0.047 and p<0.001).

Gaussian process regression for ultrasound scanline interpolation.

Purpose: In ultrasound imaging, interpolation is a key step in converting scanline data to brightness-mode (B-mode) images. Conventional methods, such as bilinear interpolation, do not fully capture the spatial dependence between data points, which leads to deviations from the underlying probability distribution at the interpolation points. Approach: We propose Gaussian process ( GP ) regression as an improved method for ultrasound scanline interpolation. Using ultrasound scanlines acquired from two different ultrasound scanners during in vivo trials, we compare the scanline conversion accuracy of three standard interpolation methods with that of GP regression, measuring the peak signal-to-noise ratio (PSNR) and mean absolute error (MAE) for each method. Results: The PSNR and MAE scores show that GP regression leads to more accurate scanline conversion compared to the nearest neighbor, bilinear, and cubic spline interpolation methods, for both datasets. Furthermore, limiting the interpolation window size of GP regression to 15 reduces computation time with minimal to no reduction in PSNR. Conclusions: GP regression quantitatively leads to more accurate scanline conversion and provides uncertainty estimates at each of the interpolation points. Our windowing method reduces the computational cost of using GP regression for scanline conversion.

Pre-Heating effect on the microhardness and depth of cure of Bulk-Fill composite resins / Efecto del precalentamiento de las resinas compuestas Bulk-Fill en la microdureza y la profundidad de curado

Abstract The aim of this study was to investigate the effect of preheating three bulk-fill and one conventional composite resin on the Vickers microhardness and depth of cure of these composites. In this study, three bulk-fill composites- SDR Plus (SDR), Estelite BULK FILL Flow (EST), Admira® Fusion x-tra (AFX), and one conventional composite resin G-ænial POSTERIOR (GP) were used as the control group. The samples were obtained at room temperature (24°C) and at 55°C in T2 mode after being placed in a heating device for 10 minutes. The samples were divided into eight groups (n=10) according to the type of material and heating process that was utilized (preheated and nonheated). All samples were tested with a Vickers microhardness (VHN) tester on the bottom and top surfaces. The first measurements were obtained at baseline; the second set of measurements was performed after the samples were stored in distilled water at 37°C for 24 hours. The depth of cure was calculated using a bottom/top hardness ratio of measurements. Statistical analysis was performed utilizing the SPSS V23 and Shapiro-Wilk tests. Lastly, the Duncan test was used for multiple comparisons (p<0.05). While the VHN increased after the preheating procedure in bulk-fill composites, it decreased in GP. There was no difference between the baseline and the 24-hour VHN values in SDR and GP. After 24 hours, while the VHN of EST increased, the VHN of AFX decreased. There was no difference between the hardness ratios of the AFX and EST samples (p<0.001) and hardness ratios were greater than GP and SDR. When comparing the baseline and the 24- hour values, the VHN depended on the type of materials. Sufficient curing depth was obtained in all groups with a thickness of 2mm.

Resumen El objetivo fue investigar el efecto del precalentamiento de tres resinas Bulk-fill, una resina compuesta convencional sobre la microdureza Vickers y la profundidad de curado de estas resinas. Se utilizaron tres composites Bulk-Fill-SDR Plus (SDR), Estelite BULK FILL Flow (EST), Admira® Fusion x-tra (AFX), y una resina compuesta convencional G-ænial POSTERIOR (GP) como grupo de control. Las muestras se obtuvieron a temperatura ambiente (24°C) y a 55°C en modo T2 después de haber sido colocadas en un dispositivo de calentamiento durante 10 minutos. Se dividieron en ocho grupos (n=10) según el tipo de material y el proceso de calentamiento que se utilizó (precalentado y no calentado). Se probaron con un medidor de microdureza Vickers (VHN) en las superficies inferior y superior. Las primeras mediciones se obtuvieron en la línea de base; la segunda se realizó después de que las muestras se almacenaran en agua destilada a 37°C durante 24 horas. La profundidad de curado se calculó utilizando una relación de dureza inferior/ superior de las mediciones. El análisis estadístico se realizó utilizando el SPSS V23 y las pruebas de Shapiro-Wilk. Por último, se utilizó la prueba de Duncan para las comparaciones múltiples (p<0,05). VHN aumentó tras el procedimiento de precalentamiento en las resina Bulk-Fill, disminuyó en los GP. No hubo diferencias entre los valores de VHN de referencia y de 24 horas en SDR y GP. Después de 24 horas, mientras que el VHN de EST aumentó, el VHN de AFX disminuyó. No hubo diferencias entre los ratios de dureza de las muestras de AFX y EST (p<0,001) y los ratios de dureza fueron mayores que los de GP y SDR. Al comparar los valores de referencia y los de 24 horas, el VHN dependió del tipo de materiales. Se obtuvo una profundidad de curado suficiente en todos los grupos con un grosor de 2mm.

Evaluation of gingival displacement methods in terms of periodontal health at crown restorations produced by digital scan: 1-year clinical follow-up.

The purpose of this clinical study was to compare the effects of the gingival displacement techniques of retraction cord, cordless paste system, and Er,Cr:YSGG laser troughing on the periodontal tissues around the crown restoration produced using a digital scan. This was analyzed by recording the probing depth (PD), plaque index, gingival index (GI), mobility, sensitivity, and bleeding on probing (BOP) index. This study included 60 mandibular 1st molars from 52 participants (20 males and 32 females) requiring crown restoration. The margin lines of the crown preparations were placed 1 mm subgingivally. Based on the gingival displacement technique used, the patients were divided into three groups: retraction cord, cordless paste system, and Er,Cr:YSGG laser troughing. A digital scan of the prepared tooth was performed. Follow-up appointments were scheduled at five different times: 1st day, 1st month, 3rd month, 6th month, and 1st year. Six periodontal indices were used to assess the periodontal health. The chi-square test was used to compare categorical variables depending on the groups. There was a significant difference in the PD, GI, and BOP index scores among the three techniques during the 1-year clinical monitoring (p < 0.001). The PD in the three zones of the buccal surface showed a significant increase with time in the retraction cord and cordless paste system groups (p < 0.001). The highest GI scores were observed in the retraction cord group on the 1st day. The Er,Cr:YSGG laser troughing procedure produced lower PD, GI, and BOP index scores as compared to the retraction cord and cordless paste system procedures in the 1-year period.

Automatically steering cardiac catheters in vivo with respiratory motion compensation.

A robotic system for automatically navigating ultrasound (US) imaging catheters can provide real-time intra-cardiac imaging for diagnosis and treatment while reducing the need for clinicians to perform manual catheter steering. Clinical deployment of such a system requires accurate navigation despite the presence of disturbances including cyclical physiological motions (e.g., respiration). In this work, we report results from in vivo trials of automatic target tracking using our system, which is the first to navigate cardiac catheters with respiratory motion compensation. The effects of respiratory disturbances on the US catheter are modeled and then applied to four-degree-of-freedom steering kinematics with predictive filtering. This enables the system to accurately steer the US catheter and aim the US imager at a target despite respiratory motion disturbance. In vivo animal respiratory motion compensation results demonstrate automatic US catheter steering to image a target ablation catheter with 1.05 mm and 1.33° mean absolute error. Robotic US catheter steering with motion compensation can improve cardiac catheterization techniques while reducing clinician effort and X-ray exposure.

Ultrasound Imaging Characterization of Soft Tissue Dynamics of the Seated Human Body.

To characterize the dynamics of internal soft organs and external anatomical structures, this paper presents a system that combines medical ultrasound imaging with an optical tracker and a vertical exciter that imparts whole-body vibrations on seated subjects. The spatial and temporal accuracy of the system was validated using a phantom with calibrated internal structures, resulting in 0.224 mm maximum root-mean-square (r.m.s.) position error and 13 ms maximum synchronization error between sensors. In addition to the dynamics of the head and sternum, stomach dynamics were characterized by extracting the centroid of the stomach from the ultrasound images. The system was used to characterize the subject-specific body dynamics as well as the intrasubject variabilities caused by excitation pattern (frequency up-sweep, down-sweep, and white noise, 1-10 Hz), excitation amplitude (1 and 2 m/s2 r.m.s.), seat compliance (rigid and soft), and stomach filling (empty and 500 mL water). Human subjects experiments (n = 3) yielded preliminary results for the frequency response of the head, sternum, and stomach. The method presented here provides the first detailed in vivo characterization of internal and external human body dynamics. Tissue dynamics characterized by the system can inform design of vehicle structures and adaptive control of seat and suspension systems, as well as validate finite element models for predicting passenger comfort in the early stages of vehicle design.

Evaluation the Effect of Different Antioxidants Applied After Bleaching on Teeth Color Stability / Avaliação do efeito de diferentes antioxidantes aplicados após o clareamento na estabilidade da cor dos dentes

Objective: Vital bleaching is a popular treatment option for discolored teeth; but at post-treatment stage, loss of adhesion is highly reported. Literature focused on antioxidant application for the answer of this issue. The aim of this study was to compare the effects of six different antioxidants on color stability of bleached teeth. Material and Methods: This study included total of 84 extracted intact non-carious lower incisors. 35% hydrogen peroxide was applied on the labial surfaces of specimens in accordance with manufacturer's instructions. The bleached teeth were divided into 7 groups. No antioxidants were applied to the control group. For the experimental groups, the following antioxidants were applied for 10 minutes each: 5% proanthocyanidin, 5% sodium ascorbate, 5% lycopene, %5 green tea, %5 white tea and %5 α-tocopherol. CIE L*, a* and b* values of the teeth were measured by a spectrophotometer. One-way ANOVA was used to determine the differences among the groups. Multiple comparisons were examined with Tukey HSD. Results: The one-way ANOVA test revealed a statistically significant difference between the groups (p < 0.005). Highest color change was observed in lycopene group and the lowest in green tea group. Conclusion: Proanthocyanidin, white tea and green tea could be considered as post-bleaching antioxidant alternatives based on their herbal nature. (AU)

Objetivo: O clareamento vital é uma opção popular de tratamento para dentes descoloridos, mas na fase pós-tratamento, a perda de adesão é altamente relatada. A literatura enfocou a aplicação de antioxidantes para a resposta desta questão. O objetivo deste estudo foi comparar os efeitos de seis diferentes antioxidantes na estabilidade da cor de dentes clareados. Material e Métodos: Este estudo incluiu um total de 84 incisivos inferiores extraídos, intactos e não cariados. Peróxido de hidrogênio a 35% foi aplicado nas superfícies labiais dos espécimes de acordo com as instruções do fabricante. Os dentes clareados foram divididos em 7 grupos. Nenhum antioxidante foi aplicado ao grupo controle. Para os grupos experimentais, os seguintes antioxidantes foram aplicados por 10 minutos cada: proantocianidina a 5%, ascorbato de sódio a 5%, licopeno a 5%, chá verde a 5%, chá branco a 5% e α-tocoferol a 5%. Os valores CIE L *, a * e b * dos dentes foram medidos por um espectrofotômetro. ANOVA um fator foi usada para determinar as diferenças entre os grupos. As comparações múltiplas foram examinadas com Tukey HSD. Resultados: O teste ANOVA revelou uma diferença estatisticamente significativa entre os grupos (p <0,005). A maior mudança de cor foi observada no grupo do licopeno e a menor no grupo do chá verde. Conclusão: Proantocianidina, chá branco e chá verde podem ser considerados como alternativas antioxidantes pós-clareamento com base em sua natureza fitoterápica. (AU)

Comparison of the Shear Bond Strength of Metal Orthodontic Brackets Bonded to Long-term Water-aged and Fresh Porcelain and Composite Surfaces.

OBJECTIVE: The aim of the present study was to compare the shear bond strength (SBS) of metal orthodontic brackets bonded to long-term water-aged and fresh porcelain and composite surfaces. METHODS: One porcelain (Vitadur Alpha (VA)) and three composite (Filtek Ultimate (FU), Tetric EvoCeram (TEC), and Gradia Direct Anterior (GDA)) materials were evaluated in the present study. First, 10 discs from each material were prepared and subjected to the aging procedure for 5 years. Then, for comparison, another 10 discs from each material were prepared as fresh surfaces and stored in distilled water for 24 h. Metal brackets were bonded to the prepared disc surfaces, and after being stored in water for 24 h, they were subjected to shear bond test using a universal testing machine. Adhesive remnant index (ARI) scores were obtained by examining the disc surfaces under a stereomicroscope at 10× magnification. Kruskal-Wallis test was used to compare the aged and fresh groups. RESULTS: Although the difference between the SBS between the aged and fresh groups with VA, FU, and TEC was not significant, the SBS was significantly higher in the fresh group with GDA. With regard to ARI scores, there was no significant difference between the aged and fresh groups with FU and GDA, whereas the ARI scores of the aged groups with VA and TEC were higher. CONCLUSION: It was concluded that the aged restoration materials have a distinctive influence on the SBS of metal orthodontic brackets.

Long-term follow-up of enamel color changes after treatment with fixed orthodontic appliances.

INTRODUCTION: The aim of this study was the long-term follow-up of enamel color changes observed in the middle third of buccal tooth surfaces after treatment with fixed orthodontic appliances. METHODS: The study included 120 maxillary central and lateral incisors and canines of 20 subjects who had fixed orthodontic treatment. The Spectro Shade Micro device (MHT, Verona, Italy) was used to evaluate the color changes of the teeth. Measurements were made from the middle third of the buccal surfaces of the teeth after fixed orthodontic treatment and in month 3, month 6, and year 1 of the retention phase. The Commission Internationale de l'Echairage L* a* b* system that expresses the color coordinates in L*, a*, and b* symbols was used to determine the tooth color, and ΔE values between the time periods were calculated. Repeated measurement analysis of variance was used in evaluating the color changes. RESULTS: The increases in ΔL values at 3 months, 6 months, and 1 year after treatment were statistically significant, whereas they were not statistically significant from months 3 to 6, month 3 to year 1, or month 6 to year 1. The decrease in Δa and the increase in Δb values were not statistically significant. ΔE values at all time periods were statistically significant within themselves, and the greatest change was observed 1 year after treatment. ΔE values were 1.52 to 3.57, and a visible but clinically acceptable color change occurred. CONCLUSIONS: In the first 3 months, there was a significant increase in the lightness of the tooth color.

High dynamic range ultrasound imaging.

PURPOSE: High dynamic range (HDR) imaging is a popular computational photography technique that has found its way into every modern smartphone and camera. In HDR imaging, images acquired at different exposures are combined to increase the luminance range of the final image, thereby extending the limited dynamic range of the camera. Ultrasound imaging suffers from limited dynamic range as well; at higher power levels, the hyperechogenic tissue is overexposed, whereas at lower power levels, hypoechogenic tissue details are not visible. In this work, we apply HDR techniques to ultrasound imaging, where we combine ultrasound images acquired at different power levels to improve the level of detail visible in the final image. METHODS: Ultrasound images of ex vivo and in vivo tissue are acquired at different acoustic power levels and then combined to generate HDR ultrasound (HDR-US) images. The performance of five tone mapping operators is quantitatively evaluated using a similarity metric to determine the most suitable mapping for HDR-US imaging. RESULTS: The ex vivo and in vivo results demonstrated that HDR-US imaging enables visualizing both hyper- and hypoechogenic tissue at once in a single image. The Durand tone mapping operator preserved the most amount of detail across the dynamic range. CONCLUSIONS: Our results strongly suggest that HDR-US imaging can improve the utility of ultrasound in image-based diagnosis and procedure guidance.

Predictive Filtering in Motion Compensation with Steerable Cardiac Catheters.

Robotic cardiac catheterization using ultrasound (US) imaging catheters provides real time imaging from within the heart while reducing the difficulty in manually steering a four degree-of-freedom (4-DOF) catheter. Accurate robotic catheter navigation in the heart is challenging due to a variety of disturbances including cyclical physiological motions, such as respiration. In this work we compensate for respiratory motion by using an Extended Kalman Filter (EKF) to predict target motion and by applying the predictions to steer the US imaging catheter. The system performance was measured in bench top experiments with phantom vasculature. The robotic system with predictive filtering tracked cyclically moving targets with 1.59 mm and 0.72° mean error. Accurately tracking moving structures can improve intra-procedural treatments and visualization.

Compensation for Unconstrained Catheter Shaft Motion in Cardiac Catheters.

Cardiac catheterization with ultrasound (US) imaging catheters provides real time US imaging from within the heart, but manually navigating a four degree of freedom (DOF) imaging catheter is difficult and requires extensive training. Existing work has demonstrated robotic catheter steering in constrained bench top environments. Closed-loop control in an unconstrained setting, such as patient vasculature, remains a significant challenge due to friction, backlash, and physiological disturbances. In this paper we present a new method for closed-loop control of the catheter tip that can accurately and robustly steer 4-DOF cardiac catheters and other flexible manipulators despite these effects. The performance of the system is demonstrated in a vasculature phantom and an in vivo porcine animal model. During bench top studies the robotic system converged to the desired US imager pose with sub-millimeter and sub-degree-level accuracy. During animal trials the system achieved 2.0 mm and 0.65° accuracy. Accurate and robust robotic navigation of flexible manipulators will enable enhanced visualization and treatment during procedures.

A Four Degree of Freedom Robot for Positioning Ultrasound Imaging Catheters.

In this paper, we present the design, fabrication, and testing of a robot for automatically positioning ultrasound (US) imaging catheters. Our system will point US catheters to provide real-time imaging of anatomical structures and working instruments during minimally invasive procedures. Manually navigating US catheters is difficult and requires extensive training in order to aim the US imager at desired targets. Therefore, a four-degree-of-freedom (4DOF) robotic system was developed to automatically navigate US imaging catheters for enhanced imaging. A rotational transmission enables 3DOF for pitch, yaw, and roll of the imager. This transmission is translated by the 4DOF. An accuracy analysis calculated the maximum allowable joint motion error. Rotational joints must be accurate to within 1.5 deg, and the translational joint must be accurate within 1.4 mm. Motion tests then validated the accuracy of the robot. The average resulting errors in positioning of the rotational joints were 0.04-0.22 deg. The average measured backlash was 0.18-0.86 deg. Measurements of average translational positioning and backlash errors were negligible. The resulting joint motion errors were well within the required specifications for accurate robot motion. The output of the catheter was then tested to verify the effectiveness of the handle motions to transmit torques and translations to the catheter tip. The catheter tip was navigated to desired target poses with average error 1.3 mm and 0.71 deg. Such effective manipulation of US imaging catheters will enable better visualization in various procedures ranging from cardiac arrhythmia treatment to tumor removal in urological cases.

A 4-DOF Robot for Positioning Ultrasound Imaging Catheters.

In this paper we present the design, fabrication, and testing of a robot for automatically positioning ultrasound imaging catheters. Our system will point ultrasound (US) catheters to provide real-time imaging of anatomical structures and working instruments during minimally invasive surgeries. Manually navigating US catheters is difficult and requires extensive training in order to aim the US imager at desired targets. Therefore, a four DOF robotic system was developed to automatically navigate US imaging catheters for enhanced imaging. A rotational transmission enables three DOF for pitch, yaw, and roll of the imager. This transmission is translated by the fourth DOF. An accuracy analysis was conducted to calculate the maximum allowable joint motion error. Rotational joints must be accurate to within 1.5° and the translational joint must be accurate within 1.4 mm. Motion tests were then conducted to validate the accuracy of the robot. The average resulting errors in positioning of the rotational joints were measured to be 0.28°-0.38° with average measured backlash error 0.44°. Average translational positioning and backlash errors were measured to be significantly lower than the reported accuracy of the position sensor. The resulting joint motion errors were well within the required specifications for accurate robot motion. Such effective navigation of US imaging catheters will enable better visualization in various procedures ranging from cardiac arrhythmia treatment to tumor removal in urological cases.

Characterization of an air jet haptic lump display.

During manual palpation, clinicians rely on distributed tactile information to identify and localize hard lumps embedded in soft tissue. The development of tactile feedback systems to enhance palpation using robot-assisted minimally invasive surgery (RMIS) systems is challenging due to size and weight constraints, motivating a pneumatic actuation strategy. Recently, an air jet approach has been proposed for generating a lump percept. We use this technique to direct a thin stream of air through an aperture directly on the finger pad, which indents the skin in a hemispherical manner, producing a compelling lump percept. We hypothesize that the perceived parameters of the lump (e.g. size and stiffness) can be controlled by jointly adjusting air pressure and the aperture size through which air escapes. In this work, we investigate how these control variables interact to affect perceived pressure on the finger pad. First, we used a capacitive tactile sensor array to measure the effect of aperture size on output pressure, and found that peak output pressure increases with aperture size. Second, we performed a psychophysical experiment for each aperture size to determine the just noticeable difference (JND) of air pressure on the finger pad. Subject-averaged pressure JND values ranged from 19.4-24.7 kPa, with no statistical differences observed between aperture sizes. The aperture-pressure relationship and the pressure JND values will be fundamental for future display control.