ABSTRACT
The objective of this study was to investigate the effect of different cooling rates and subsequent post-firing heat treatment on the final hardness of a metal-ceramic alloy. For this, Specimens of Pd-Ag-In-Sn alloy underwent simulated firing at two different cooling rates, followed by post-firing heat treatment. Hardness measurement, microstructure observation, and crystal structure analysis were conducted on the firing simulated and post-firing heat-treated specimens to analyze the causes of hardness variations. The experimental results showed that the difference in cooling rates during simulated firing had an impact on the final hardness of the alloy, and the specimens cooled at the slowest rate (Stage 3) exhibited higher hardness at all firing Stages compared to the specimens cooled at the highest rate (Stage 0). Regardless of the difference in cooling rates during the firing process, the hardness of the alloy significantly increased by the post-firing heat treatment. The increase in hardness by the post-firing heat treatment was attributed to the formation of fine precipitates in the matrix, and the precipitation reaction occurred as a result of the decrease in solubility of (Pd, Ag, Au) 3 (In, Sn, Zn) phase in the Pd-Ag-rich matrix. The clinical significance of this study is that performing the post-firing heat treatment demonstrates effectiveness in increasing the reduced hardness after porcelain firing in metal-ceramic alloys.
ABSTRACT
This study investigated the effect of the difference in the cooling rates on the optical properties of zirconia during the simulated firing of porcelain, without a porcelain layer on a zirconia core ceramic. No difference was observed in the average transmittance of zirconia with the cooling rate during simulated firing (p>0.05). In all groups, the average transmittance decreased from approximately 44% to approximately 28% (p0.05). In all groups, the translucency decreased from approximately 16 to approximately 5 (p<0.001), while the opalescence increased from approximately 6 to approximately 11 (p<0.001) as the thickness increased from 0.51 mm to 2.00 mm. Thus, the average transmittance and translucency parameter decreased exponentially as the thickness increased in all groups regardless of the cooling rate during simulated porcelain firing, while the opalescence parameter increased in a parabolic manner. Therefore, in this study, even if porcelain is fired at a cooling rate higher or lower than the typical cooling rate when manufacturing a prosthesis with a zirconia core, the optical properties of zirconia are not expected to be significantly affected.
ABSTRACT
In this study, Au-Pt-Pd metal-ceramic alloy was examined by varying cooling rate during simulated porcelain firing cycles to investigate the effect of cooling rate on hardness and related microstructure during simulated firing. The final hardness was different according to the cooling rate after the simulated porcelain firing cycles. The reduction in hardness value was smaller after cooling at the faster cooling rate (Stage 0) than the value after slower rate (Stage 3). In the ice-quenched specimens after oxidation treatment (OXI-IQ), homogenization was slightly occurred, and the hardness decreased apparently compared to that of the as-cast specimens (AS-CAST). In the specimens cooled at Stage 0 and Stage 3 after oxidation, the hardness increased apparently compared to the ice-quenched specimens, even though the hardness decreased later by further firing simulation.The final hardness was lower in the specimen cooled at the slower rate (Stage 3) than the faster rate (Stage 0), and it seems to be due to the coarsening of the microstructure. The matrix and precipitates were consisted of FCC (face-centered-cubic) structure rich in Au. The Au content was higher in the matrix and the Pt content was higher in the precipitates, which corresponded to the Au-Pt binary phase diagram.
ABSTRACT
In this study, Au-Pt-Pd metal-ceramic alloy was examined by varying cooling rate during simulated porcelain firing cycles to investigate the effect of cooling rate on hardness and related microstructure during simulated firing. The final hardness was different according to the cooling rate after the simulated porcelain firing cycles. The reduction in hardness value was smaller after cooling at the faster cooling rate (Stage 0) than the value after slower rate (Stage 3). In the ice-quenched specimens after oxidation treatment (OXI-IQ), homogenization was slightly occurred, and the hardness decreased apparently compared to that of the as-cast specimens (AS-CAST). In the specimens cooled at Stage 0 and Stage 3 after oxidation, the hardness increased apparently compared to the ice-quenched specimens, even though the hardness decreased later by further firing simulation.The final hardness was lower in the specimen cooled at the slower rate (Stage 3) than the faster rate (Stage 0), and it seems to be due to the coarsening of the microstructure. The matrix and precipitates were consisted of FCC (face-centered-cubic) structure rich in Au. The Au content was higher in the matrix and the Pt content was higher in the precipitates, which corresponded to the Au-Pt binary phase diagram.
ABSTRACT
In this experiment, the alloy having the composition of 49.5Pd-40Ag-9In-1Ga (wt.%) was used to find the most effective cooling rate for the hardening of alloy during porcelain firing simulation. In each stage of firing simulation, ice-quenching or cooling at the most effective cooling rate for hardening of the alloy was done after firing to observe changes in the hardness and associated microstructures during the firing and subsequent cooling. For this purpose, the firing simulated alloy was characterized by analyzing the changes in hardness, microstructure, crystal structure and the elemental distribution. The hardness of alloy decreased by cooling after oxidation treatment, which was induced by the homogenization of the specimen. In this alloy, the most effective cooling rate for alloy hardening after oxidation treatment was Stage 0. During the porcelain firing simulation until the final firing stage, the cooling rate was set to Stage 0, and the complete firing simulation was performed until the final firing stage, Glaze. As a result, the final hardness of the metal substructure obtained after complete firing simulation was lower than that of the as-cast specimen. The decrease in hardness caused by the porcelain firing simulation results from a reduction in the interface between the precipitates of face-centered tetragonal structures and the matrix of face-centered cubic structures as the precipitates coarsen.
ABSTRACT
Effect of cooling rate during oxidation treatment on the hardness change by post firing heat treatment of a Pd-Cu-Ga-Zn alloy after simulated porcelain firing was investigated and the following results were obtained. In the firing simulated specimens after quenching during the oxidation treatment, the hardness did not increase by post-firing heat treatment. However, in the firing simulated specimens after slow cooling during the oxidation treatment, post-firing heat treatment for 25 minutes was effective in increasing the hardness (p < 0.05). In the firing simulated specimens after quenching during the oxidation treatment, the significant decrease in hardness during the post-firing heat treatment was attributed to the coarsening of fine precipitates formed in the matrix and plate-like precipitates. In the firing simulated specimens after slow cooling during the oxidation treatment, the increase in hardness during the post-firing heat treatment for 25 minutes was due to precipitation hardening. From these results, it was found that the cooling rate during the oxidation treatment affected the change of hardness by the post-firing heat treatment after the simulated firing. From these results, post-firing heat treatment increased the hardness of the Pd-Cu-Ga-Zn alloy only when the cooling rate during the oxidation treatment was slow.
Subject(s)
Alloys , Dental Porcelain , Fires , Hardness , Hot TemperatureABSTRACT
PURPOSE: The purpose of the study was to test the effects of music therapy on postoperative pain in patients with total hip replacement. METHOD: The research design was a nonequivalent control group pretest-posttest design. The subjects were composed of thirty patients with total hip replacement. Fifteen of them were assigned to the experimental group and fifteen to the control group. Fifteen minutes tailored music therapy was given to the experimental group during five consecutive days. The instruments used for this study were pain NRS(numerical rating scale). The data were analyzed using percent, mean, standard deviation, chi-square-test and repeated measure ANOVA using SPSS WIN 11.0. RESULTS: Hypothesis 1 "The score of pain NRS of experimental group will be lower than those of control group" was accepted(F=15.945, p<.001). Hypothesis 2 "The frequency of PCA analgesics of experimental group will be fewer than those of control group" was accepted (t=-2.312, p=.028). Hypothesis 3 "The vital signs(pulse, systolic BP and diastolic BP) of experimental group will be different from those of control group" was rejected. CONCLUSION: This music therapy can be recommended as an efficient nursing intervention to reduce postoperative pain in patients with total hip replacement.