PURPOSE: Translucency of all-ceramic restorations is an important factor which affects the final appearance and esthetic outcome of the restoration. The aim of this study was to evaluate the effect of the shade of coloring liquid on the translucency of zirconia framework. MATERIALS AND METHODS: Thirty zirconium oxide core plate (15 x 12 x 0.5 mm) were divided into 6 groups of 5 plates each. Each group was classified according to the shade of coloring liquid based on Vita Classic Scale (A2, A3, B1, C2, and D2), and each sample was immersed in coloring liquid for 3 seconds as recommended by the manufacturer, except for the control group. Contrast ratio, as a translucency parameter, was calculated using a spectrophotometer and the data were analyzed with oneway analysis of variance (ANOVA) and Tukey's honestly significant differences (HSD) tests (alpha=.05). RESULTS: Significant differences in translucency among the control and test groups, and the B1 shaded group and other shades was observed. There were no significant differences among A2, A3, C2, and D2 shaded groups. CONCLUSION: The translucency of the zirconium oxide cores was affected by the coloring procedure and significant differences in the translucency measurements were identified between specific shades.
Zirconium

STATEMENT OF PROBLEM: There have been many studies about marginal adaptation of Zirconia core fabricated with various CAD/CAM systems. But, the comparative study has not been conducted much. PURPOSE: This study was to compare marginal adaptations of zirconia cores fabricated with 3 different CAD/CAM systems. MATERIAL AND METHODS: The in vitro marginal adaptations of zirconia cores fabricated with 3 different CAD/CAM systems(Adens(R) system, Lava(R) system, and Cerasys(R) system) were evaluated and compared. In this study 30 zirconia cores were fabricated(10 zirconia cores per each system). The measurements of the marginal adaptatioin were carried out using microscope L-150A(R)(Nikon, Japan). Measurements were recorded at 50 points. The measurements were analyzed using Kruskal-Wallis test and Wilcoxon rank sum test. RESULTS: Within the limits of this study, the results were as follows. 1. Mean marginal gap values obtained were 284.5+/-152.9 micrometer in Adens(R) system, 99.0+/-73.0 micrometer in Lava(R) system, and 153.5+/-85.7 micrometer in Cerasys(R) system. 2. Zirconia core made by Lava(R) system showed the smallest marginal gap(P<0.05). CONCLUSION: In the limitation of this study, we concluded that Lava(R) System was superior than other systems(Adens(R) system and Cerasys(R) system) in the marginal adaptation.
Zirconium

OBJECTIVETo investigate the microstructure of dental zirconia ceramics prepared by two-step sintering.

METHODSNanostructured zirconia powder was dry compacted, cold isostatic pressed, and pre-sintered. The pre-sintered discs were cut processed into samples. Conventional sintering, single-step sintering, and two-step sintering were carried out, and density and grain size of the samples were measured. Afterward, T1 and/or T2 of two-step sintering ranges were measured. Effects on microstructure of different routes, which consisted of two-step sintering and conventional sintering were discussed. The influence of T1 and/or T2 on density and grain size were analyzed as well.

RESULTSThe range of T1 was between 1450 degrees C and 1550 degrees C, and the range of T2 was between 1250 degrees C and 1350 degrees C. Compared with conventional sintering, finer microstructure of higher density and smaller grain could be obtained by two-step sintering. Grain growth was dependent on T1, whereas density was not much related with T1. However, density was dependent on T2, and grain size was minimally influenced.

CONCLUSIONTwo-step sintering could ensure a sintering body with high density and small grain, which is good for optimizing the microstructure of dental zirconia ceramics.

PURPOSE: The purpose of this study was to evaluate the fit of zirconia core using MAD/MAM system comparing to that of conventional metal-ceramic and CAD/CAM system. MATERIALS AND METHODS: Duplicating the prepared resin tooth, 50 improved stone dies were fabricated. These dies are classified as a group of 5 to create the core. The groups were composed of metal-ceramic, Cercon(R), Ceramill(R), Rainbow(TM), and Zirkonzhan(R). Each core was cemented to stone die, and then, absolute marginal discrepancy was measured with microscope at a magnification of x50. Statistical analysis was done with one-way ANOVA test and Tukey's HSD test. RESULTS: The mean absolute marginal discrepancy for metal-ceramic was 51.97 +/- 23.38 micrometer, for Cercon(R) was 62.16 +/- 25.88 micrometer, for Ceramill(R) was 67.64 +/- 40.38 micrometer, for Rainbow(TM) was 125.07 +/- 42.19 micrometer, and for Zirkonzhan(R) was 105 +/- 44.61 micrometer. CONCLUSION: 1. Fit of margin was identified as in the order of metal-ceramic, Cercon(R), Ceramill(R), Zirkonzhan(R), and Rainbow(TM). 2. Absolute marginal discrepancy of the zirconia core that designed by MAD/MAM system had significant differences in order of Ceramill(R), Zirkonzhan(R), and Rainbow(TM). 3. The mean absolute marginal discrepancy between Cercon(R) and Ceramill(R) did not show significant differences.
Tooth ; Zirconium

PURPOSE: The purpose of this study is to compare three different CAD/CAM systems through the fracture strength of zirconia core and to evaluate the clinical availability of each system. MATERIAL AND METHODS: The following three groups of 30 maxillary mesial incisor core for all-ceramics(each group 10) were fabricated as follows: group 1. Adens(R) CAD/CAM system, group 2. Cerasys(R) CAD/CAM system, group 3. 3M LAVA(R)CAD/CAM system. All specimens were manufactured consistently thickness 0.5mm and relief 40 micrometer. Specimens were subjected to compressive loading on the lingual area by Z250/SN5S(R). Each group's mean and standard deviation were calculated and Kruskal Waillis test, Wilcoxon Rank Sum test were utilized to find out the relationship among the groups. RESULTS: The results were as follows: 1. The mean fracture strength of Adens(R) system was 615.89+/-156.1N, the Cerasys(R) system was 863.98+/-151.5N, and the 3M LAVA(R) system was 1143.1+/-286.6N. 2. The fracture strength of the systems showed the significant statistical differences in order of 3M LAVA(R) system, Cerasys(R) system, Adens(R) system. CONCLUSION: In this study, in spite of the differences among the groups, every group showed clinically useful results. It is necessary to study further clinical experiments on a long term basis.
Incisor ; Zirconium

PURPOSE: This study was aimed to compare the margin and internal fitness of 3-unit zirconia bridge cores fabricated by several CAD/CAM systems using replica technique. MATERIALS AND METHODS: Three unit-bridge models in which upper canine and upper second premolar were used as abutments and upper first premolar was missed, were fabricated. Fourty models were classified into 4 groups (Cerasys(R) (Group C), Dentaim(R) (Group D), KaVo Everest(R) (Group K), Lava(TM)(Group L)), and zirconia cores were fabricated by each company. Sixteen points were measured on each abutment by replica technique. Statistical analysis was accomplished with two way ANOVA and Dunnett T3 (alpha=.05). RESULTS: In most systems, there was a larger gap on inter margin than outer margin. In the Group K, overall fitness was excellent, but the incisal gap was very large. In the Group C, marginal gap was significantly larger than Group K, but overall internal gap was uniform (P<.05). The axial gap was under 100 microm in all system. The difference between internal and external gap was small on Group L and C. However, internal gap was significantly larger than external gap in Group D (P<.05). The fitness of canine was better than second premolar among abutments (P<.05). CONCLUSION: The marginal and internal gap was within the clinically allowed range in all of the three systems. There was a larger gap on second premolar than canine on internal and marginal surface. In most systems, there was a larger gap on occlusal surface than axial surface.
Bicuspid ; Replica Techniques ; Zirconium

PURPOSE: The purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed. MATERIAL AND METHODS: Three experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo Everest(R) ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared. RESULTS: Despite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage. CONCLUSION: Within the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block.
Cyclic N-Oxides ; Zirconium

OBJECTIVEIn order to make certain the compaction pressure as well as pre-sintering temperature on the machinability of the zirconia ceramic.

METHODS3 mol nano-size 3 mol yttria partially stabilized zirconia (3Y-TZP) powder were compacted at different isostatic pressure and sintered at different temperature. The cylindrical surface was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy.

RESULTSPre-sintering temperature had the obviously influence on the machinability of 3Y-TZP. The cutting surface was smooth, and the integrality of edge was better when the pre-sintering temperature was chosen between 800 degrees C to 900 degrees C. Compaction pressure showed only a weak influence on machinability of 3Y-TZP blanks, but the higher compaction pressure result in the poor surface quality.

CONCLUSIONThe best machinability of pre-sintered zirconia body was found for 800-900 degrees C pre-sintering temperature, and 200-300 MPa compaction pressure.

Dental Porcelain ; Zirconium

PURPOSE: The purpose of this research was to evaluate the shear bond strength between zirconia core and veneer ceramic after surface treatment. MATERIAL AND METHODS: Zirconia cores (N = 40, n = 10, 10 mm x 10 mm x 3 mm) were fabricated according to the manufacturers??instructions and ultrasonically cleaned. The veneering ceramics (thickness 3 mm) were built and fired onto the zirconia core materials. Four groups of specimens with different surface treatment were prepared. Group I: without any pre-treatment, Group II: treated with sandblasting, Group III: treated with liner, Group IV: treated with sandblasting and liner. The shear bond strength was tested in a universal testing machine. Data were compared with an ANOVA and Scheffe post hoc test (P = .05). RESULTS: The shear bond strength of group VI was significantly higher than the other groups. CONCLUSION: Both mechanically and chemically treated simultaneously on zirconia core surface influenced the shear bond strength between the core and veneering ceramic in all-ceramic systems.
Ceramics ; Collodion ; Fires ; Zirconium