ABSTRACT
Translucent monolithic zirconia is widely used because it has continuously enhanced color and translucency. However, when translucent monolithic zirconia are used for esthetic zone like anterior, it has problem to be exposed to color of titanium abutment. The purpose of this study was to evaluate the effect of coloring and cementing of translucent zirconia on the color masking of titanium abutments. The CIE L*, a*, and b* values were measured using a spectrophotometer in three subgroups after coloring with A2 colorant and white opaque colorant, and the color difference and translucency of each group were analyzed. In the A2 colorant application group, the color difference (ΔE* ) between zirconia and zirconia on titanium abutments was not clinically acceptable (ΔE* > 3.3). In the white opaque group and the white opaque plus A2 colorant group, the color difference (ΔE* ) between zirconia and zirconia on titanium abutments was clinically acceptable (1<ΔE* <3.3). The translucency of zirconia was significantly affected by the coloring treatment (P<.001). The Pearson correlation between color difference and translucency parameters was high (r=0.982, R2 =0.965). The white coloring treatment to translucent zirconia affected masking of titanium abutment. The combination of A2 colorant and white opaque colorant increased the color masking effect of titanium abutments and achieved a shade similar to natural teeth. Resin cement adhesion to translucent zirconia did not affect the color masking of titanium zirconia. As the zirconia translucency increases, it had less of an effect on the titanium abutment.
ABSTRACT
The purpose of this in vitro study was to evaluate the effect of speed sintering on flexural strength, density, and linear shrinkage of monolithic zirconia. Four hundred Ø18.7×1.7-mm presintered zirconia specimens were divided into 8 groups (n=50) based on the sintering times (speed (60, 90, and 120 min) or normal (540 min)) and temperatures (1400, 1450, 1500, and 1550 ℃). The mechanical properties (Vickers hardness, biaxial flexural strength, and fracture toughness) and physical properties (linear shrinkage, density, and porosity) were examined. The crystallite size of zirconia was calculated using scherer’s formula. The mechanical properties (biaxial flexural strength, Vickers hardness, and fracture toughness) of all specimens increased with increasing sintering times and temperatures. The biaxial flexural strength of the SS groups sintered 1500 ℃ and 1550 ℃ with 120 min showed similar value compared with NS groups. The SS 120 and NS groups showed similar the linear shrinkage percentages at all temperatures. The porosity decreased with increasing sintering times and temperatures in all specimens.The sintered and relative density and the average crystallite size increased with increasing sintering times and temperatures in all specimens. The average crystallite size ranged from 70.1 nm to 129.8 nm. XRD analysis showed the presence of a tetragonal metastable phase in all groups before and after sintering. The biaxial flexural strength values under speed sintering (1500 ℃ and 1550 ℃, 120 min) were similar to those of normal sintering groups.
ABSTRACT
The purpose of this study was to examine the effect of hardness and optical properties of dental zirconia in accordance to sintering condition and aging. 10.0 mm×10.0 mm×1.5 mm zirconia specimens were prepared using Luxen Enamel E2.According to aging, zirconia specimens were sintered under fifteen different conditions. Specimens were divided into six subgroup and sintered with various durations (4 h, 5 h, 6 h, 7 h, and 12 h) at the various maximum temperature (1,500℃, 1,530℃, and 1,560℃). The hardness was measured four times per specimen using a Micro Vickers hardness tester, CIE L * , a * , b * values of each specimen were measured using a spectrophotometer and the TP values were calculated for translucency comparison.In the specimen with aging, there was a difference in hardness according to the sintering temperature, but there was no difference in hardness according to the sintering time. In the specimen with aging, as sintering temperature increased, CIE L * , a * , b * values decreased, resulting in a decrease in brightness and tendency of green and blue trends. In the specimen with aging, there was no change in L * value with decreasing sintering time and as sintering time decreased, CIE a * , b * values decreased, resulting in tendency of green and blue. In the specimen with aging, even if the sintering time decreases from 12 hours to 5 hours, there was no reduce in TP values.
ABSTRACT
The purpose of this study was to examine the effect of hardness and optical properties of dental zirconia in accordance to sintering condition and aging. 10.0 mm×10.0 mm×1.5 mm zirconia specimens were prepared using Luxen Enamel E2.According to aging, zirconia specimens were sintered under fifteen different conditions. Specimens were divided into six subgroup and sintered with various durations (4 h, 5 h, 6 h, 7 h, and 12 h) at the various maximum temperature (1,500℃, 1,530℃, and 1,560℃). The hardness was measured four times per specimen using a Micro Vickers hardness tester, CIE L * , a * , b * values of each specimen were measured using a spectrophotometer and the TP values were calculated for translucency comparison.In the specimen with aging, there was a difference in hardness according to the sintering temperature, but there was no difference in hardness according to the sintering time. In the specimen with aging, as sintering temperature increased, CIE L * , a * , b * values decreased, resulting in a decrease in brightness and tendency of green and blue trends. In the specimen with aging, there was no change in L * value with decreasing sintering time and as sintering time decreased, CIE a * , b * values decreased, resulting in tendency of green and blue. In the specimen with aging, even if the sintering time decreases from 12 hours to 5 hours, there was no reduce in TP values.
ABSTRACT
PURPOSE: The purpose of this study was to evaluate the effect of two coloring liquids (aqueous and acid-based coloring liquids) and the position of multilayered zirconia on the flexural strength of multilayered zirconia. MATERIALS AND METHODS: The multilayered zirconia specimens were divided into upper and lower positions. The specimens were divided into three subgroups (n=10): non-shaded, acid-based coloring liquid, and aqueous coloring liquid. The specimens were cut using a milling machine and were immersed in either a acid-based coloring liquid or aqueous coloring liquid 2 times for 5 seconds. The specimens were sintered in a sintering furnace according to the manufacturer's introduction. The flexural strength of the specimen was measured using a universal testing machine and the surface of the specimen was observed using a field emission scanning electron microscope. RESULTS: The flexural strength of multilayered zirconia was 400 – 500 MPa. There was no statistically significant difference among all groups (P>.05).The flexural strength of the multilayered zirconia was not influenced by the kind of coloring liquid used (P>.05). The flexural strength of the multilayered zirconia colored with the coloring liquids was not influenced by its position (P>.05). CONCLUSION: The different coloring liquid application did not affect the flexural strength of multilayered zirconia of all positions.
ABSTRACT
The purpose of this study is to evaluate the effects of polymerization conditions on the flexural strength and transparency of orthodontic acrylic resin. Materials and methods: The specimens were prepared by applying pressure of 1 bar, 2 bar and 4 bar in air, room temperature water, 50℃ water and 70℃ water. The flexural strength of each specimen was measured using a universal testing machine and the translucency parameter (TP) was calculated by measuring the CIE L*a*b* value of each specimen using a spectrophotometer. The flexural strength of orthodontic acrylic resin was the highest in water at 50℃, and the flexural strength was significantly lower in the order of 70℃ water, room temperature water and air (P 0.05). The transparency of orthodontic acrylic resin showed the highest value in air and was significantly lower in the order of room temperature, 50℃ water and 70℃ water (P 0.05). Within the limits of this study, the flexural strength and transparency of the orthodontic acrylic resin differ according to polymerization conditions, but there is no difference according to the pressure.