Color and translucency stability of CAD/CAM restorative materials

Aim: This study assessed the color and translucency stability of a polymer infiltrated ceramic network (PICN) and compared it with a resin composite (RC) and a feldspathic ceramic (FEL). Methods: Disc-shaped samples of a PICN (Vita Enamic), a feldspathic ceramic (Vitablocks Mark II), and a resin composite (Brava block) were prepared from CAD/CAM blocks. PICN and RC surfaces were finished with a sequence of polishing discs and diamond paste. FEL samples received a glaze layer. The samples were subjected to 30-min immersions in red wine twice a day for 30 days. CIEL*a*b* coordinates were assessed with a spectrophotometer at baseline and after 15 and 30 days of immersion. Color alteration (ΔE00) and translucency parameter (TP00) were calculated with CIEDE2000. Average roughness was measured before the staining procedures. Color difference and translucency data were analyzed with repeated-measures ANOVA and Tukey’s tests. Roughness was analyzed with the Kruskal-Wallis test. Results: Roughness was similar among the experimental groups. All materials had their color alteration significantly increased from 15 to 30 days of staining. PICN reached an intermediate ΔE00 between FEL and RC at 15 days. PICN revealed a color alteration as high as the composite after 30 days. No statistical difference was observed regarding translucency. Conclusion: PICN was not as color stable as the feldspathic ceramic at the end of the study. Its color alteration was comparable to the resin composite when exposed to red wine. However, the translucency of the tested materials was stable throughout the 30-day staining.

SURFACE ROUGHNESS OF LITHIUM DISILICATE PRESS CERAMICS AFTER DIFFERENT TYPES OF POLISHING

INTRODUCTION: The smoothness of a ceramic’s surface is very important of its esthetic and prophylactic qualities. AIM: The purpose of this investigation is to study the possibilities of polishing lithium disilicate ceramics after making a correction on the glazed ceramic surface. MATERIALS AND METHODS: The subject of the study were 20 test samples made of lithium disilicate press ceramics. They were divided into 4 groups according to the method of processing and polishing. Group 1 was treated with a red diamond bur and polishing set; Group 2 was treated with a green diamond bur and polishing set; Group 3 was treated with a red diamond bur, polishing set and diamond paste; Group 4 was treated with a diamond bur with green coding, polishing set and diamond paste. The samples were examined with an atomic force microscope to observe the change in surface relief. The reference point for comparison was the surface of the glazed ceramic. RESULTS: After polishing with diamond paste, the surface became smoother compared to the treatment of the surface with a polishing kit alone. CONCLUSION: Regardless of the polishing protocol used, there was a difference in the topography of the ceramic surface before and after treatment.

Surface properties of composite resins with and without fluorides for bracket bonding / Propriedades de superfície de resinas compostas com e sem fluoretos para colagem de suportes

The aim of this study was to evaluate the surface properties of orthodontic resins with and without fluoride. Forty disks, measuring 2 mm thick by 6 mm in diameter, were made of 4 bracket-bonding composite resins (n=10): Transbond Plus Color Change-3M/Unitek (TPCC); Transbond XT- 3M/Unitek (TXT), Orthocem -FGM (OC); Orthocem UV Trace-FGM (OCUV). The discs were photoactivated for 40 seconds with irradiance of 450 mW/cm2 and manually polished in sequence by silicon carbide sandpapers with 1200 and 2000 grain size and finished with diamond paste and felt disc. The surface microhardness analysis was performed using a Shimadzu Micro Hardness Tester HMV-2,000 (Shimadzu Corporation, Kyoto, Japan) with a load of 50 gF and a 5 second penetration time. Surface roughness readings were taken using a Surf Corder Roughness Meter (SE 1700- Kosaka, Lisboa-Portugal). For data analysis, ANOVA (one-way) was used, followed by Tukey's post-test (?=0.05). The microhardness results showed a difference (p?0.05) in the means of the orthodontic resins between TPCC and TXT with the other groups. After the surface roughness analysis, the averages showed that TPCC resin showed higher roughness compared to OC and OCUV (p?0.05), and there was no statistical difference with TXT. It was concluded that statistically the composite resins with fluoride showed significant difference regarding hardness and roughness.

Validation of a Screening Method Based on a Needle Stochastic Sensor for the Determination of Interleukins 1β, 6, and 12 in Biological Samples

Interleukins proved to be valuable biomarkers for different diseases. Interleukins 1β, 6, and 12 can be used as biomarkers for brain cancer diagnosis, and therefore this paper proposed a needle stochastic sensor based on protoporphyrin IX immobilized in nano-diamond paste for fast screening of biological samples, such as whole blood, urine and brain tumoral tissue, for these interleukins. The results obtained using this needle stochastic sensor proved that the interleukins 1β, 6, and 12 can be reliably determined from whole blood, urine and brain tumoral tissue, with recoveries higher than 96.00% and with relative standard deviations lower than 1.00%. The validation of the method was performed using whole blood and tissue samples collected from the patients confirmed with brain tumor.

Magnetic Abrasive Finishing of Beta-Titanium Wire Using Multiple Transfer Movement Method

Titanium is often used in various important applications in transportation and the healthcare industry. The goal of this study was to determine the optimum processing of magnetic abrasives in beta-titanium wire, which is often used in frames for eyeglasses because of its excellent elasticity among titanium alloys. To check the performance of the magnetic abrasive finishing process, the surface roughness (Ra) was measured when the specimen was machined at various rotational speeds (700, 1500, and 2000 rpm) in the presence of diamond paste of various particle sizes (0.5, 1, and 3 μm). We concluded that the surface roughness (Ra) was the best at 2000 rpm, 1 μm particle size, and 300 s processing time, and the surface roughness of β-titanium improved from 0.32 to 0.05 μm. In addition, the optimal conditions were used to test the influence of the finishing gap, and it was found that the processing power was superior at a gap of 3 mm than at 5 mm when processing was conducted for 300 s.

INVESTIGATION OF ULTRA-THIN SILICON WAFERS STRENGTH DEPENDING ON WAFER MATERIAL GROWING METHODS AND SURFACE TREATMENT

The mechanical strength of ultra-thin 100 μm Si wafers was measured depending on Si growing methods and machining modes of wafer surface preparation (abrasive grinding, diamond paste polishing, chemical-mechanical polishing — CMP)

Surface roughness of monolithic zirconia ceramic submitted to different polishing systems

Aim: The objective was to evaluate, quantitative and qualitative, the abrasive effect of three polishing systems on the monolithic zirconia ceramic. Methods: Thirty disk-shaped samples of Yttria Tetragonal Zirconia Polycrystal (Y-TZP) were randomly distributed in three groups (n = 10) according to polishing system: G1- Komet system (KO); G2 - CeraGloss system (CG); G3 - Eve Diacera system (EV). The surface roughness (Ra) was obtained with Rugosimeter in four different moments: a) initial - glaze sample (Ra0); b) after occlusal adjustment with diamond burs (Ra1); c) after polishing with the abrasive systems (Ra2); d) after polishing with felt disc and diamond paste (Ra3). Four additional samples were observed in scanning electron microscopy (SEM). Results: According to the Generalized Estimating Equation followed by the Bonferroni test (α = 0.05), the CG provided the lowest Ra2 (0.63 μm), not differing significantly from the KO (0.78 μm). The highest Ra2 was obtained with the EV (0.97 μm), which did not differ significantly from the KO. There was no statistical difference in Ra between the polishing with the abrasive systems (Ra2) and the final polishing with diamond paste (Ra3). SEM images showed that the polishing systems did not completely remove the grooves caused by the diamond burs during the occlusal adjustment. Conclusion: It was concluded that CG promoted smoother surface of the monolithic zirconia ceramic compared to EV, and intermediate smoothness was obtained with KO.

Single Edge Precrack V-Notched Beam (SEPVNB) Fracture Toughness Testing on Silicon Nitride

The previous Measurement of fracture toughness test by using bright indentation for precracked beam method (ASTM C1421) was found difficult to be carried out due to difficulty in precrack generation and measurement of the crack size. In this research single edge precrack V-notch beam (SEPVNB) is introduced as an alternative to solve the problem from previous standardized method. A real crack that can created with referred size is recognized as the best condition for fracture toughness test. The material prepared for this purpose was silicon nitride (Si3N4) produced by CeramTec (Plochingen, Germany) under the name SL200 B. It is a gas pressure sintered ceramic containing 3 wt.% Al2O3 and 3 wt.% Y2O3. The V Notch was prepared by using razor blade with diamond paste following ISO/FDIS 23146 standard preparation with more addition on precrack introduction. The precrack was introduced by so called opposite roller loading. The fracture toughness test was carried out by following procedure in ISO/FDIS 23146 . The result then was compared for validation with both single edge V-notch beam standard (ISO/FDIS 23146 ) and Surface crack in Flexure SCF (ASTM C 1421). The result of fracture toughness by using method that is introduce in this research is found 5.8270.275 MPa1/2 which is close to the result of SCF (5.335 0.222 MPa1/2). Meanwhile the value of fracture toughness by using V-notch beam is 4.9130.098 MPa1/2