High-frequency ultrasound blood flow imaging based on laser speckle algorithm / 国际生物医学工程杂志

Objective To study the application of laser speckle contrast algorithm in high-frequency ultrasound blood flow imaging. Methods The laser speckle contrast algorithm was extended to the field of high-frequency ultrasound blood flow imaging. The high-frequency ultrasound structure images were processed by using the classic laser speckle temporal contrast algorithm to suppress the static tissue signals, enhance the dynamic blood flow signals, and obtain the high-frequency ultrasound blood flow images. The simulation experiments on flow phantoms were conducted to verify the effectiveness of the algorithm, and then human skin tissue in vivo experiments were performed to verify the applicability of the algorithm. The performances of blood flow images which obtained from ultrasound structure images with different frames by laser speckle contrast algorithm were compared and analyzed. Results The blood flow information in a tube was clearly visible in the flow phantoms experiments. The static skin tissue signals were significantly suppressed, dynamic blood flow signals were strengthened in the human skin tissue in vivo experiments, and high-frequency ultrasound blood flow images were obtained. By comparing and analyzing the performances of blood flow images, the results showed that the best blood flow images could be obtained when the number of frame was set to 10 frames. Conclusions The speckle contrast algorithm is feasible and has good application prospects in high-frequency ultrasound blood flow imaging.

Effect of resin cement color on the color of commercially available zirconia crown / 대한치과재료학회지

The purpose of this study is to evaluate the effect of resin cement color on the color of commercially available zirconia crown. The zirconia and resin cements used for the experiment were NuSmile® ZR Zirconia LT Shade (LT), RelyX™ U200 TR, A2, and A3O (TR, A2, A3O). The disks of zirconia and resin cements with diameters of 5 mm and thicknesses of 1 mm were prepared. Five disks were made for each specimen. The CIE L*a*b* values of zirconia, resin cements and the combinations thereof were measured on black and white backgrounds, respectively, using a spectrophotometer. The color effect of resin cement on the color of the zirconia crown was evaluated by calculating translucency parameter (TP), contrast ratio (CR), and color differences (ΔĖ(ab)) based on the measured CIE L*a*b* values. The statistical significances were verified by one-way ANOVA and the Tukey-multiple comparisons tests. As a result, the TP and CR values were decreased (p < 0.05) and increased, respectively, in the combination of zirconia and resin cement disks compared to zirconia disk per se. When using the black background, the ΔĖ(ab) values between zirconia and the combination of the zirconia and three resin cement disks were imperceptible level. The A3O showed the lowest ΔĖ(ab) value among three resin cements. When using the white background, the ΔĖ(ab) values between zirconia and the combination of zirconia and TR resin cement (LT/TR) disks showed acceptable level. However, the ΔĖ(ab) values between zirconia and the combination of zirconia and A2 resin cement (LT/A2) disks showed unacceptable level. Meanwhile, the ΔĖ(ab) values between zirconia and the combination of zirconia and A3O resin cement (LT/A3O) disks showed perceptible but acceptable level. Within the limits of this study, the colors of resin cements did not cause unacceptable color changes of zirconia except the combination of LT/A2 on the white background. The resin cement that gave the least color changes to zirconia was A3O. This means that the resin cement A3O is recommended to use for minimizing color changes when cementing commercially available zirconia crown to tooth.

Comparison among three translucency parameters / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aims to compare the three commonly used translucency parameters in prosthodontics: transmittance (T), contrast ratio (CR), and translucency parameter (TP).</p><p><b>METHODS</b>Six platelet specimens were composed of Vita enamel and dental porcelain. The initial thickness was 1.2 mm. The specimens were gradually ground to 1.0, 0.8, 0.6, 0.4, and 0.2 mm. T, color parameters, and reflection were measured by a spectrocolorimeter for each corresponding thickness. T, CR and TP were calculated and compared.</p><p><b>RESULTS</b>TP increased, whereas CR decreased, with decreasing thickness. Moreover, 
T increased with decreasing thickness, and exponential relationships were found. Two-way ANOVA showed statistical significance between T and thickness, except between T and the 1.2 mm and 1.0 mm enamel porcelain groups. No difference was found among the coefficient variations (CV) of T, CR and TP. Curve fitting indicated the existence of exponential relationships between T and CR and between T and TP. The values for goodness of fit with statistical significance were 0.951 and 0.939, respectively (P<0.05).</p><p><b>CONCLUSIONS</b>Under the experimental conditions, T, TP and CR achieved the same CV. T and TP, as well as T and CR, were found with exponential relationships. The value of CR and TP could not represent the translucency precisely, especially when comparing the changing ratios.</p>

Evaluation of translucency of monolithic zirconia and framework zirconia materials

PURPOSE: The opacity of zirconia is an esthetic disadvantage that hinders achieving natural and shade-matched restorations. The aim of this study was to evaluate the translucency of non-colored and colored framework zirconia and monolithic zirconia. MATERIALS AND METHODS: The three groups tested were: non-colored framework zirconia, colored framework zirconia with the A3 shade according to Vita Classic Scale, and monolithic zirconia (n=5). The specimens were fabricated in the dimensions of 15×12×0.5 mm. A spectrophotometer was used to measure the contrast ratio, which is indicative of translucency. Three measurements were made to obtain the contrast ratios of the materials over a white background (L*w) and a black background (L*b). The data were analyzed using the one-way analysis of variance and Tukey HSD tests. One specimen from each group was chosen for scanning electron microscope analysis. The determined areas of the SEM images were divided by the number of grains in order to calculate the mean grain size. RESULTS: Statistically significant differences were observed among all groups (P<.05). Non-colored zirconia had the highest translucency with a contrast ratio of 0.75, while monolithic zirconia had the lowest translucency with a contrast ratio of 0.8. The mean grain sizes of the non-colored, colored, and monolithic zirconia were 233, 256, and 361 nm, respectively. CONCLUSION: The translucency of the zirconia was affected by the coloring procedure and the grain size. Although monolithic zirconia may not be the best esthetic material for the anterior region, it may serve as an alternative in the posterior region for the bilayered zirconia restorations.

The influence of the vital bleaching agents on translucency of the bovine enamel / 대한치과보존학회지

This study was done to evaluate whether vital bleaching agents could influence on the translucency of the bovine enamel. The anterior bovine teeth that were extracted one day before and without any gross discoloration were obtained and then were preserved in physiologic saline. 6 mm cylindrical tooth specimens were fabricated with diamond puncher perpendicularly on labial surface of bovine tooth. After embedded in transparent acrylic resin with labial surface being exposed, they were cut to a thickness of 1.2 mm with low speed diamond saw (Isomat, Buehler Co., Lake Bluff, IL, USA). They were smoothly ground to 1 mm thickness of enamel with sandpaper. 24 specimens were randomly divided into 3 groups and control group respectively. Opalescence (10% carbamide peroxide, Ultradent, South Jordan, USA), Rembrandt (10% carbamide peroxide, DenMat, USA) and Opalescence F (15% carbamide peroxide with fluoride, Ultradent, USA) were applied on labial sides of the bovine enamel for 7 days (bleaching agents were reapplied every 24 hours) and the opposite surface was contacted to cotton that soaked in distilled water. The control group was soaked in distilled water. Three stimulus value X, Y and Z were evaluated with colorimeter (Color & Color Differencemeter, Model TC-6FX, Tokyo Denshoku Co., Japan) on the labial surface of all specimen three times on white and black background plate before the bleaching agents were applied and on 3rd, 5th and 7th day after applied. The degree of translucency was normally assessed by measuring the inverse property, opacity (contrast ratio). 10% Opalescence, 15% Opalescence-F, and control group showed no significant variation in the translucency of bovine enamel, However Rembrandt decreased the translucency of it (p < 0.01).