Effect of different pattern size and pattern shape on castability of commercially pure titanium / 대한치과보철학회지

PURPOSE: The purpose of this study was to investigate the effect of geometrically different wax pattern shapes and sizes on the castability of Grade2 Cp-Ti (commercially pure titanium). MATERIALS AND METHODS: Total of 40 mesh wax pattern (61 mm x 24 mm, 207 grids), (61 mm x 17 mm, 138 grids) was cast in this experiment. Depending on the geometrical shape of the wax pattern, 8 groups was organized; Flat, Semicircular, Horse-shoe and V-shape, each consisting 5 samples. Runner-bar sprue was used in all patterns. The number of completely cast grid in wax pattern served as a measure for the castability of comercially pure titanium. RESULTS: The mean value of square count in each group was as followed; 133.20 squares in group SS (96.52%), 132.40 squares in group SH (95.94%), 132.00 squares in group SF (95.65%), 127.60 squares in SV (91.43%), 198.60 squares in group LF (95.94%), 197.80 squares in group LV (95.56%), 196.40 squares in group LS (94.88%), and 188.00 squares in group LH (90.82%). CONCLUSION: Within the limitations of this study the results indicate that there were no sttistically significant difference in castability of titanium regarding wax pattern shape (P>.05). However, Small size wax patterns were showing the noticeable castability more than Large size pattern.

Evaluation of titanium surface properties by Nd: YVO4 laser irradiation: pilot study / 대한치과보철학회지

PURPOSE: This study was conducted to evaluate the roughness and surface alternations of three differently blasted titanium discs treated by Nd: YVO4 Laser irradiation in different conditions. MATERIALS AND METHODS: Thirty commercially pure titanium discs were prepared and divided into three groups. Each group was consisted of 10 samples and blasted by ZrO2 (zirconium dioxide), Al2O3 (aluminum oxide), and RBM (resorbable blasted media). All the samples were degreased by ultrasonic cleaner afterward. Nine different conditions were established by changing scanning speed (100, 300, 500 mm/s) and repetition rate (5, 15, 35 kHz) of Nd: YVO4 Laser (Laser Pro D-20, Laserval Korea(R) Seoul, South Korea). After laser irradiation, a scanning electron microscope, X-ray diffraction analysis, energy dispersive X-ray spectroscopic analysis, and surface roughness analysis were used to assess the roughness and surface alternations of the samples. RESULTS: According to a scanning electron microscope (SEM), titanium discs treated with laser irradiation showed characteristic patterns in contrast to the control which showed irregular patterns. According to the X-ray diffraction analysis, only Al2O3 group showed its own peak. The oxidation tendency and surface roughness of titanium were similar to the control in the energy dispersive X-ray spectroscopic analysis. The surface roughness was inversely proportional to the scanning speed, whereas proportional to the repetition rate of Nd: YVO4. CONCLUSION: The surface microstructures and roughness of the test discs were modified by the radiation of Nd: YVO4 laser. Therefore, laser irradiation could be considered one of the methods to modify implant surfaces for the enhancement of osseointegration.

Effects of chromium chloride addition on coloration and mechanical properties of 3Y-TZP / 대한치과보철학회지

PURPOSE: The purpose of this study was to examine the effects of chromium chloride addition on coloration, mechanical property and microstructure of 3Y-TZP. MATERIALS AND METHODS: Chromium chloride was weighed as 0.06, 0.12, and 0.25 wt% and each measured amount was dissolved in alcohol. ZrO2 powder was mixed with each of the individual slurry to prepare chromium doped zirconia specimen. The color, physical properties and microstructure were observed after the zirconia specimen were sintered at 1450degrees C. In order to evaluate the color, spectrophotometer was used to analyze the value of L*, C*, a* and b*, after placing the specimen on a white plate, and measured according to the International Commission on Illumination (CIE) standard, Illuminant D65 and SCE system. The density was measured in the Archimedes method, while microstructures were evaluated by using the scanning electron microscopy (SEM) and XRD. Fracture toughness was calculated Vickers indentation method and indentation size was measured by using the optical microscope. The data were analyzed with 1-way ANOVA test (alpha= 0.05). The Tukey multiple comparison test was used for post hoc analysis. RESULTS: 1. Chromium chloride rendered zirconia a brownish color. While chromium chloride content was increased, the color of zirconia was changed from brownish to brownish-red. 2. Chromium chloride content was increased; density of the specimen was decreased. 3. More chromium chloride in the ratio showed increase size of grains. 4. But the addition of chromium chloride did not affect the crystal phase of zirconia, and all specimens showed tetragonal phase. 5. The chromium chloride in zirconia did not showed statistically significant difference in fracture toughness, but addition of 0.25 wt% showed a statistically significant difference (P<.05). CONCLUSION: Based on the above results, this study suggests that chromium chlorides can make colored zirconia while adding in a liquid form. The new colored zirconia showed a slight difference in color to that of the natural tooth, nevertheless this material can be used as an all ceramic core material.

Adaptability of zirconia core fabricated by cold isostatic pressing / 대한치과보철학회지

PURPOSE: The purpose of this study is to fabricate the new zirconia block (CNU block) and to evaluate fit of core and porcelain veneered zirconia crown. MATERIAL AND METHODS: The experimental blocks were fabricated from the commercial ytrria-stabilized zirconia powder (KZ-3YE Type A). The powder was uniaxial pressing and the green bodies were conducted using the Cold Isostatic Pressing. The zirconia blocks were presintered at 1040degrees C and the final sintering was performed at 1450degrees C. The Kavo Everest ZS blank(R) (KaVo, Biberach/Ri beta.) was used as a control group. The linear shrinkage of CNU block and Kavo block were compared. Twenty-one cores for porcelain veneered crowns were fabricated with CAD/CAM system (Everest(R), Biberach/Ribeta.). Group I: seven cores fabricated from Kavo blocks, Group II: seven cores fabricated from CNU blocks, Group III: seven cores from CNU blocks and porcelain veneering for crowns. All specimens were cemented and sectioned into two planes: diagonal and bucco-lingual. The measurement of the marginal, internal, and occlusal fit was carried out using SEM (S-4800(R)) at 30 x. The results were analyzed by one-way ANOVA test. RESULTS: The linear shrinkage of the CNU block and the KaVo block was 19.00% and 20.09%. The marginal gap of cores (29.67 +/- 6.58 micrometer) fabricated from CNU blocks showed significantly smaller than that of the cores of Kavo blocks (36.84 +/- 7.18 micrometer) (P < .05). The internal gaps of the porcelain veneered crowns (32.23 +/- 6.33 micrometer) were larger than those of the other two groups (37.57 +/- 6.81 micrometer and 38.14 +/- 6.81 micrometer). CONCLUSION: No statistically significant difference was found in between experimental groups and control group. The experimental groups in marginal gap showed significantly smaller than the control group.