Long Quan Shao

The Color of Fe2O3 and Bi2O3 Pigmented Dental Zirconia Ceramic

The aim of this study was to explored the effects of Fe2O3 and Bi2O3 on the color properties of a 3Y-TZP zirconia ceramics for dental application. Pigmented dental ZrO2 powders were prepared by mixing different concentration of Fe2O3 and Bi2O3, also in their combinations with 3Y-TZP powders. The mixture was compacted by isostastic pressure, then densely sintered. Color parameters were measured by Minolta CM2600d spectrophotometer. XRD was used to exam the structure of colored 3Y-TZP. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the Fe2O3 and Bi2O3. Combined use of Fe2O3 and Bi2O3 could further decrease the L* value, which color scope was suitable for dental color matching. The XRD spectra showed only tetragonal phase was detected.

Surface Microhardness and Flexural Strength of Colored Zirconia

The surface microhardness and flexural strength of colored zirconia were examined. Two groups of zirconia disks (1mm thick, 20mm in diameter) within 5 disks each were shading with the same coloring liquids IL2 (Vita Classic-scale) when another group of 5 disks measured in no color. The shading time of one group was 3s and that of the other group was prolonged to 30s. The mechanical properties were tested after sintering at 1500°C. Data were evaluated using ANOVA analysis. Disks of shading 30s showed a lower strength 712  53 MPa. The value of 3s was 853  46 MPa. There were no significant difference on microhardness between the two shading time. Prolonged the shading time lowered the biaxial flexural strength of zirconia ceramic, but shading time did no effect on surface microhardness.

Preparation and Properties of Porous β–Tricalcium Phosphate Bone Graft

The need for bone repair has increased as the population ages. However, currently, the bone grafts still have some disadvantages, such as low compressive strength and porosity, which limit their use. In order to solve these disadvantages, in this study, the porous beta-tricalcium phosphate (β-TCP) anorganic bone graft were prepared from healthy bovine cancellous bone by cell-free, defat and twice calcinations. X-ray diffraction (XRD) was used to investigate the chemical composition of the bone graft. And the morphology, porosity and mechanical strength of the bone graft were also evaluated. The results showed that most constituent of the bone graft was β-TCP. In addition, the bone graft scaffold exhibited the macro and micro porous structure and the porosity was 57.63%, just as the nature cancellous bone. The compressive strength was 4.47±0.63MPa. Above all, the porous β-TCP anorganic bone graft not only has similar chemical composites as the nature cancellous bone, but also it can effectively retain the porous structure of natural cancellous bone and provides optimal channels for the ingrowth of new bone and blood vessels.Therefore, the porous β-TCP anorganic bone graft is a potential biomaterial in bone tissue engineering.

Effects of Surface Treatment on the Microstructural and Crystallographic Changes of Dental 3Y-TZP Ceramic

Objective: To investigate the effects of different surface treatments on the microstructural and crystallographic changes of dental 3Y-TZP ceramics. Methods: 21 pieces of zirconia specimens (15 ´ 15 ´ 1.5 mm) were prepared and divided into 7 groups: control group; grinding group; polishing group; sandblasting group; sandblasting + veneer porcelain sintering group; sandblasting + veneer porcelain sintering twice group and sandblasting + annealing group. The crystal structure of specimen was monitored by X-ray diffraction (XRD) before morphological observation with scanning electron microscope. Results: monoclinic phase increased after grinding while decreased little after polishing, bigger phase change presented after sandblasting compared with decreased phase change induced by veneer porcelain sintering; annealing eradicated the surface m phase. Grinding produced coarse scratches on the surface of samples with removal of surface particles; after grinding and polishing to 7 um level, the surface particles were removed massively, and the surface became smooth with remaining scare scratches and substantial micro cracks. Sandblasting removed scratches near completely producing coarse and irregular surface of samples. Conclusions: Grinding, sandblasting and polishing could produce the transition of Zirconia Ceramic surface from t to m phase. It is better to use heat treatment after mechanical treatment to reverse the changed surface phase.

Effects of Aging on the Mechanical Properties of Dental Pigmented 3Y-TZP Ceramics

The purpose of this study was to investigate the structure, mechanical and low temperature aging properties of colored dental zirconia ceramics. Colored 3Y-TZP zirconia dental zirconia ceramics were made by mixing colorants and their combinations into a 3Y-TZP powder, the green body were compacted at 200MPa, presinter at 1050°C and densely sintered at 1500°C for 2h. Specimens were subjected to an accelerated aging test carried out in an autoclave in steam at 134°C, 2bar, for 4hs. XRD was used to identify the crystal phases, three-point bending strength were tested before and after aging according to the ISO 6872 standard, polished and aging specimens were observed by Atomic Force Microscopy (AFM) to evaluate surface microstructure. Tetragonal-to-monoclinic phase transformation was detected for both uncolored and colored specimens, the relative content of monoclinic phase was increased with the prolonged aging time. Aging had no significant negative effects on flexural strength on colored 3Y-TZP. The nucleation and growth of monoclinic phase were detected by AFM in surface of both colored and uncolored zirconia.

Study on Dental Colored Zirconia Restoration

This paper explored the color and mechanical properties of CeO2 and Er2O3 shaded zirconia ceramics for dental application. Twelve kinds of colored dental ZrO2 powders were prepared. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the CeO2 and Er2O3, while reducing of the brightness( L* ) value was little. Three-point bending strength decreased form 1209MPa to 845MPa after coloring, which was lower than the uncolored materials (1301MPa). The fracture toughness decrease slightly. SEM observation revealed more porous microstructure in specimen containing both two additives. Cerium oxide and erbium oxide are candidates of color additives for shading dental zirconia ceramics.

A Comparative Study on Relative Translucency of Four Dental All-Ceramic Core Materials

The aim of this study were to compare the relative translucency of four dental all-ceramic core materialsIPS e.max Press,Zenostar,Lava Zirconia and Upcera Zirconia.All core materials were fabricated into samples at the diameter of 10mm and the thickness of 0.50.02mm.The relative translucency of samples were determined with color difference meter and analysed with SPSS 13.0 software.It was showed that the relative translucency of 4 all-ceramic core materials were statistically different.There was a decreasing order of their relative translucency,IPS e.max PressLava Zirconia ZenostarUpcera Zirconia.IPS e.max Press has the hightest translucency,and it was advisably used to restore anterior tooth.Upcera Zirconia was the most opaque of 4 all-ceramic core materials,and it was suitable for post tooth.

Effect of Vitique Esthetic Cementation on Tetracycline Stained Teeth-Mask with Different Simulated Staining Levels Following IPS-Empress II Ceramic Veneers

Abstract. To evaluate the color changes of tetracycline stained teeth after restored with IPS-EMPRESS Ⅱ ceramics. Simulated tetracycline stained teeth were divided according to staining degree into four groups: mild, moderate, severe, and very severe groups; each group had ten specimens which were repaired with IPS-EMPRESS Ⅱ ceramics veneers, bonded with Vitique Esthetic Cementation System. The ShadeEye-NCC color system was used to analyze the change in L, a and b. ΔE were calculated to compare color difference among the four groups.Before and after bonding, the values of L, a, b were significantly different (P <0.05). Mild tetracycline stained teeth bonded using resin adhesive without opaque bonding have a better effect than moderate and severe tetracycline stained teeth bonded with opaque resin adhesive; while, it is best to use other restorations to repair very severe tetracycline stained teeth. The IPS-EMPRESS Ⅱ ceramics can effectively improve the color of discolored tooth, however , the final color of the veneered teeth is easily influenced by the color of the abutment teeth. Aluting agent with color masking ability can do some improvements in the final color. An appropriate bonding agent should be chosen to perfect the final results of the veneered tooth.

Flexure Strength and Elastic Modulus of Four Types of Dental Fiber Posts

Objective. To investigate the flexure strengths and elastic modulus of four types of dental fiber posts. Methods. The flexure strengths of ParaPost Taper Lux, Tenax Fiber White, Luxa Post and Rebilda Post fiber post were measured. The rupture modes were analyzed with SEM. Results. There was no significant difference between ParaPost Taper Lux (591.47±35.15MPa) and Rebilda Post (614.67±58.36MPa) in flexure strength (P>0.05), and Tenax Fiber White (846.62±71.15MPa) had significantly higher flexure strength than the other groups. There was no significant difference between Tenax Fiber White (23.93±2.14GPa) and Luxa Post (22.67±1.39GPa) in elastic modulus (P>0.05), and Tenax Fiber White and Luxa Post had significantly lower elastic modulus than other groups. It could be observed by transverse SEM that the combine of fiber and resin was even and compact and plenty of resin fragment adhered to the surface of fiber in Tenax Fiber White group, multitudinous cracks were observed by lengthwise SEM. Conclusion. The flexural properties and rupture modes of four kinds of dental fiber posts were significantly different.

Effect of Zirconia Surface Roughness on Shear Bond Strength to Resin Cements

Despite the expanded application for zirconia in restoration dentistry, there is less clear recommendation in the literature regarding the relation between zirconia surface roughness and its shear bond strength to resin cements. The aim of this study was to assess the effect of surface roughness of Cercon zirconia on its shear bond strength to resin cements. 66 Zirconia rectangular specimens (10 mm×10 mm×3 mm) were prepared from Cercon zirconia blocks, finished using a diamond rotary cutting instrument, sintered, and then assigned into 6 groups. The specimens in the first group without polishing were used as control. Other groups were polished against 120#, 240#, 360#, 500# and 600# sand paper after sintered, respectively. Ceramic surface were analyzed by scanning electron microscopy (SEM) and Surface profilometer. 10 samples of each group were bonded with Variolink N resin cements respectively and submitted to shear bond strength test. Shear bond strength was measured and statistically analyzed. The results showed that the population means of 6 groups of samples were not equal. There was no significant difference between control group and 600# sand paper treated group, 500#, 360# and 240# sand paper treated groups (P>0.05), but a significant difference among the other groups (P<0.05). Findings of this study revealed that the shear bond strength might be raised by increasing the surface roughness of Cercon zirconia. Therefore, the surface roughness of Cercon zirconia has an effect on the shear bond strength, but is not the determining factor in clinical use.