Infinite optical thickness of dentine porcelain of IPS E.max A color series / 南方医科大学学报

<p><b>OBJECTIVE</b>To determine the infinite optical thickness of dentine porcelain of IPS E.max A color series.</p><p><b>METHODS</b>Cylindrical dentine porcelain specimens of the IPS E.max A color series were prepared with a diameter of 13 mm and thickness of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 mm. The chromatic value of all the specimens was determined with CM-5 spectrometer against standard black and white background. The chromatic aberration (deltaE) was calculated by regression equation.</p><p><b>RESULTS</b>The infinite optical thickness of dentine porcelain of the IPS E.max A color series ranged from 2.341 to 3.333 mm for a deltaE of 1.0, and from 2.064 to 2.904 mm for a deltaE of 1.5. As the chromaticity or thickness increased, the influence by the background color decreased, and the color of specimens became gradually close to the intrinsic color.</p><p><b>CONCLUSION</b>The thickness of the background dentine porcelain specimens must exceed its infinite optical thickness to represent the intrinsic color and avoid the influence by the extrinsic color.</p>

Effects of three types of veneering porcelain on bending strength of KAVO(TM) Y-TZP/porcelain bilayered structure / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of three types of veneering porcelain on the bending strength of KAVO Y-TZP/porcelain layered structure.</p><p><b>METHODS</b>KAVO zirconia ceramics were used as the substructure. To form Y-TZP/porcelain bilayered structure, a leucite-based veneering porcelain was fired on the zirconia substructures by slip-casting technique with dentin washbake, and two nano-fluorapatite-based veneering porcelains were fired on the zirconia substructures by either slip-casting or pressed-on technique with or without liner coverage. The bending strength was tested according to ISO 6872 standard, and the veneered surfaces of the fracture samples were analyzed by scanning electron microscopy (SEM).</p><p><b>RESULTS</b>For covering KAVO zirconia core material, the conventional veneering slurry-porcelain combined with liner or wash firing had significant higher bending strength than pressed-on porcelain. SEM showed that the main failure type at the interface was adhesive failure.</p><p><b>CONCLUSION</b>Thin layer sintering using washbake program or liner on KAVO zirconia surface increases the surface wettability, and this procedure may be indispensable when veneering on the surface of dental zirconia.</p>

Effect of pigmentation on the strength of dental Y-TZP/porcelain bilayered structure / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of two methods of pigmentation on the flexural strength of dental Y-TZP/porcelain layered structure.</p><p><b>METHODS</b>KaVo zirconia substructures were pigmented by dipping presintered blocks in the coloring solution VITA LL1 and LL5, and colored TZ-3YS zirconia substructures were fabricated by adding pigments before isostatic pressing. The colors No.1 and No.5 were used for the test. The specimens were made in monolithic or bilayered forms, and the flexural strength was tested. XRD and SEM with EDX were used to analyze the characteristics of the surface structure.</p><p><b>RESULTS</b>In KaVo group, no significant differences were found in the flexural strength between white and LL1 and LL5 colored monoclinic materials, nor in bilayered structures. While in TZ-3YS group, significant differences were noted in the flexural strength between color No.5 white and color No.1 monoclinic materials, but not between the latter two subgroups. The flexural strength was significantly lowered by veneering with porcelain in both zirconia groups, and similar findings were observed with the monoclinic materials. Only the tetragonal phase was detected in both of the zirconia groups.</p><p><b>CONCLUSION</b>Pigmentation has no apparent effects on the bonding strength between the veneering porcelain and zirconia. Both coloring methods are appropriate when the concentration of the pigments is under deliberate control.</p>

Measurement of chromaticity of five hued zirconia / 南方医科大学学报

<p><b>OBJECTIVE</b>To determine the chroma value of sintered IL1-IL5 zirconia materials in comparison with the Vita In-Ceram YZ color shade.</p><p><b>METHODS</b>Five types of shading dental zirconia ceramics with color gradient were prepared by adding Fe2O3, CeO2, and Bi2O3 to the zirconia powder, and their chroma values were determined using a spectrophotometer and the color difference was calculated.</p><p><b>RESULTS</b>The chroma value ranges were L: 67.76-77.78, a: -2.19-3.80, and b: 12.13-25.01. Slight deltaE was found between IL1 and LL1, IL2 and LL2, and IL3 and LL3. The deltaE between IL4 and LL4 could be compensated by veneering porcelain, whereas deltaL between IL5 and LL5 could not be compensated in this manner.</p><p><b>CONCLUSION</b>Shading dental zirconia ceramics can be prepared by addition of metal oxides with color similar to the Vita In-Ceram YZ color shades to match that of the veneering porcelain in clinical practice.</p>