ABSTRACT
Objective @#To prepare the La-doped TiO2 film on the surface of 3Y-TZP ceramics in order to observe its antibacterial properties, providing an experimental basis for the application of antibacterial zirconia ceramics in the clinic.@*Method@# A cylindrical 3Y-TZP specimen with a diameter of 20 mm and a height of 3 mm was prepared. The sol-gel method was used to prepare 1% lanthanum (La)-doped TiO2 sol, and the La-TiO2 film-3Y-TZP ceramic was prepared by dip coating on the surface of 3Y-TZP. The TiO2 thin film-3Y-TZP ceramic was prepared by adding no lanthanum nitrate solution in the same way. The surface morphology of 3Y-TZP ceramic specimens (3Y-TZP group), TiO2 thin film-3Y-TZP ceramic specimens (TiO2 film group), and La-TiO2 thin film-3Y-TZP ceramic specimens (La-TiO2 film group) was observed by scanning electron microscopy, and photocatalysis, antibacterial and cytotoxicity experiments were carried out. For the photocatalytic experiment, four specimens were randomly selected from the La-TiO2 film group and TiO2 film group to observe the degradation rate of methylene blue at different time points under sunlight. In the antimicrobial experiment, five specimens were randomly selected from the La-TiO2 film group, TiO2 film group and 3Y-TZP group. The antimicrobial activity of each group was tested using the bacteriostatic circle method, and the bacteriostatic distance of each group was compared. In the cytotoxicity experiment, three samples were randomly selected from the La-TiO2 film group, TiO2 film group and 3Y-TZP group (negative control group), and the extracts were prepared. Here, 0.064% phenol solution were served as the positive control group. Morphological observation of L-929 cells in four groups was performed after 3 d of culture. Cell viability and relative cell proliferation were measured by MTT assay.@*Results@#La-TiO2 films with uniform distribution can be prepared on a 3Y-TZP surface by the dipping-drawing method. Photocatalytic experiments showed that the degradation rate of methylene blue in the La-TiO2 film group was (41.2 ± 1.5)% in daylight for 2 hours, which was higher than that in TiO2 film group (36.5 ± 2.4)%. A significant difference was noted between the two groups (t=3.321, P=0.016). The antimicrobial experiment showed that the antimicrobial distance of La-TiO2 group was (0.34 ± 0.08) mm, which was larger than that of TiO2 group (0.12 ± 0.02) mm. No obvious antimicrobial circle was noted in 3Y-TZP group, and the antimicrobial distance of the La-TiO2 film group was larger than that of TiO2 film group (F=63.798, P < 0.001). Cytotoxicity test showed that the relative proliferation rate of cells in La-TiO2 film group was (89.5 ± 1.3)%, and the cytotoxicity rating was grade 1. Significant differences were noted among the four groups (F=68.250, P < 0.001).@*Conclusion @#The La-doped TiO2 film can improve its photocatalytic activity and enhance the antibacterial activity of 3Y-TZP without obvious cytotoxicity.
ABSTRACT
PURPOSE: This in vitro study evaluated the effects of four different cements on the color attributes of a zirconia ceramic. MATERIALS AND METHODS: 40 zirconia ceramic disk specimens (0.5 mm thickness, 10 mm diameter, 0.1 mm cement space) were fabricated by a computer-aided design and computer-aided manufacturing system. The specimens were divided into 4 groups of 10 specimens and cemented to composite substrates using four different cements including: Glass Ionomer, Panavia F2.0, Zinc Phosphate, and TempBond. The L*, a*, and b* color attributes of the specimens were measured before and after cementation by a spectrophotometer. Additionally, ΔE values were measured to determine color changes for the groups and then compared with the perceptional threshold of ΔE = 3.3. Repeated Measures ANOVA, Tukey Post Hoc, Bonferroni, One-way ANOVA, and One-sample t-test tests were used to analyze the data. All tests were carried out at the 0.05 level of significance. RESULTS: Statistically significant differences were detected in the ΔE values for Zinc Phosphate (P<.0001) and TempBond (P<.0001) groups. However, there were no statistically significant differences in this respect for Glass Ionomer (P=.99) and Panavia F2.0 (P=1) groups. The means and standard deviations of the ΔE values for Glass Ionomer, Panavia F2.0, Zinc Phosphate, and Tempbond groups were 2.11±0.66, 0.94±0.39, 5.77±0.83, and 7.50±1.16 Unit, respectively. CONCLUSION: Within the limitations of this study, it was concluded that Zinc Phosphate and Tempbond cements affected the color attributes of the tested zirconia ceramic beyond the perceptional threshold. However, Glass Ionomer and Panavia F2.0 cements created acceptable color changes.
Subject(s)
Cementation , Ceramics , Computer-Aided Design , Dental Cements , Glass , In Vitro Techniques , Spectrophotometry , ZincABSTRACT
PURPOSE: This study investigated the effect of amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics. MATERIALS AND METHODS: One-hundred sixty-five monolithic zirconia specimens (16.3 mm x 16.3 mm x 2.0 mm) were divided into 5 groups (Group I to V) according to the number of A2-coloring liquid applications. Each group was then divided into 11 subgroups by reducing the thickness up to 1.0 mm in 0.1-mm increments (Subgroup 0 to 10, n=3). Colors and spectral distributions were measured according to CIELAB on a reflection spectrophotometer. All measurements were performed on five different areas of each specimen. Color difference (DeltaE*(ab)) and translucency parameter (TP) were calculated. Data were analyzed using one-way ANOVA and multiple comparison Scheffe test (alpha=.05). RESULTS: There were significant differences in CIE L* between Subgroup 0 and other subgroups in all groups. CIE a* increased (0.523.7) were obtained between Subgroup 0 and other subgroups. TP values generally increased as the thickness reduction increased in all groups (R2>0.89, P<.001). CONCLUSION: Increasing thickness reduction reduces lightness and increases a reddish, bluish appearance, and translucency of monolithic zirconia ceramics.
Subject(s)
Ceramics , Prosthesis ColoringABSTRACT
STATEMENT OF PROBLEM: Recently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. Although zirconia has outstanding mechanical properties, the phenomenon of decrease in the life-time of zirconia resulted from degradation in flexural strength after low temperature aging has been reported. PURPOSE: The objective of this study was to investigate degradation of flexural strength of Y-TZP ceramics after various low temperature aging treatments and to evaluate the phase stability and micro-structural change after aging by using X-ray diffraction analysis and a scanning electron microscope (SEM). MATERIAL AND METHODS: Y-TZP blocks of Vita In-Ceram YZ (Vita Zahnfabrik, Bad Sackingen, Germany) were prepared in 40 mm (length) x 4 mm (width) x 3 mm (height) samples. Specimens were artificially aged in distilled water by heat-treatment at a temperature of 75, 100, 125, 150, 175, 200, and 225degrees C for 10 hours, in order to induce the phase transformation at the surface. To measure the mechanical property, the specimens were subjected to a four-point bending test using a universal testing machine (Instron model 3365; Instron, Canton, Mass, USA). In addition, X-ray diffraction analysis (DMAX 2500; Rigaku, Tokyo, Japan) and SEM (Hitachi s4700; Jeol Ltd, Tokyo, Japan) were performed to estimate the phase transformation. The statistical analysis was done using SAS 9.1.3 (SAS institute, USA). The flexural strength data of the experimental groups were analyzed by one-way analysis of variance and to detect statistically significant differences (alpha= .05). RESULTS: The mean flexural strength of sintered Vita In-Ceram YZ without autoclaving was 798 MPa. When applied aging temperature at below 125degrees C for 10 hours, the flexural strength of Vita In-Ceram YZ increased up to 1,161 MPa. However, at above 150degrees C, the flexural strength started to decrease. Although low temperature aging caused the tetragonal-to-monoclinic phase transformation related to temperature, the minimum flexural strength was above 700 MPa. CONCLUSION: The monoclinic phase started to appear after aging treatment above 100degrees C. With the higher aging temperature, the fraction of monoclinic phase increased. The ratio of monoclinic/tetragonal + monoclinic phase reached a plateau value, circa 75% above 175degrees C. The point of monoclinic concentration at which the flexural strength begins to decrease was between 12% and 54%.