The effect of gold electroforming procedure on gold-silver-palladium alloy / 대한치과보철학회지

STATEMENT OF PROBLEM: The effect of gold electroforming on gold alloy was not studied. PURPOSE: This in vitro study investigate the effect of gold electroforming on gold-silver-palladium alloy. MATERIAL AND METHODS: Three pieces of gold strips had undergone the electroforming procedures on one side and then half of the side again electroformed. The set mode for this study was program 1 (200 micrometer). And the processing time was 15min (1/20 time to form 200 micrometer coping). The confocal laser scanning microscope (PASCAL 5, Carl Zeiss, Bernried, Germany) was used to measure the thickness of the pure gold layer electroformed on the gold strips. Half of the gold strip was coated two times with electroformed gold, and the other half one time. The data from the cone focal laser system was processed to get the vertical profile of the strips and the difference of the vertical height between the double coated and single coated layer was regarded as the thickness of the gold coating. The layer thickness value to built 3D image of the cone-focal laser was set 0.5 micrometer. Next to the measurement of the thickness of the coating, the Vicker's hardness test was done. It was performed on the double coated surface, single coated surface and non-coated surface (back side) three times each. RESULTS: The mean thickness value gained from gold electroforming technique was measured to be 22 micrometer for sample 1, 23 micrometer for sample 2, 21 micrometer for sample 3. In the same condition of time, power and the amount of electrolyte, the data showed no difference between samples. According to the results of variance analysis, the differences among the variations in number of coating were statistically insignificant (p>0.05), meaning that the two times of gold electroforming coating did not change the hardness of gold-silver-palladium alloy. CONCLUSION: The test of thickness of gold coating proved the coherency of the gold electroforming procedure, in other words, when the power, the exposed surface area, processing time and the amount of electrolytes were set same, the same thickness of gold would be coated on. The hardness test showed that the electroformed gold coating did not change the hardness of the gold-silver-palladium alloy when it is coated not more than 45 micrometer.

Effect of taper and surface area of inner crown on the retentive force of electroformed outer crown / 대한치과보철학회지

PURPOSE: With gold electroforming system for the double crown, the secondary crown is electroformed directly onto the primary crown. An even thick layer of high precision can be acquired. It is thought that the retention of electroformed outer crown is primarily acquired by the adhesive force (surface tension) through the saliva which is interposed between precisely fitted inner and outer crown. The purpose of this study was to investigate the effect of taper and surface area of inner crown on the retentive force of electroformed outer crown according to the presence of saliva. MATERIALS AND METHODS: 32 titanium inner crowns with cervical diameter of 8 mm and cone angles of 0, 2, 4, 6 degrees, which had same surface area by regulated height, were machined on a lathe. Another 32 titanium inner crowns with cone angles of 0, 2, 4, 6 degrees, which had doubled surface area by increased cervical diameter, were fabricated. Eight specimens of each group, for a total of 64 titanium inner crowns, were prepared. The electroformed outer crowns were fabricated directly on the inner crowns by using electroforming machine(GAMMAT free, Gramm Technik, Germany). The tertiary frameworks were waxed-up on the electroformed outer crown and cast using nonprecious alloy(Rexillium(R)III, Jeneric(R)/ Pentronh(R) Inc., USA). The cast metal frameworks were sandblasted with alubimium oxides and cemented using resin cement(Superbond C and B, Sun Medical Co., Japan) over the electroformed copings of each specimen. Then, artificial saliva(Taliva(R), Halim Pharm Co., Korea) was sprayed between the inner and outer crown, and they were connected under 5 kg force. The retentive force was measured by the universal testing machine(Tinius Olsen 1000, Tinius Olsen, USA) with a cross-head speed of 66.67 mm/sec. The direction of cross-head travel was exactly aligned with the path of removal of the respective specimens. This measurement procedures for retentive force of electroformed outer crown with artificial saliva were repeated in the same way without presence of artificial saliva. RESULTS AND CONCLUSION: The following conclusions were drawn: 1. The retentive force of electroformed outer crown was decreased according to increased taper of inner crown(P.05).

Marginal fit of the auro galvano crown system made using the electroforming technique / 대한치과보철학회지

STATEMENT OF PROBLEM: There have been few studies about the marginal fit of Auro Galvano Crowns. PURPOSE: The purpose of this study was to compare the marginal fit of the anterior single restorations. MATERIAL AND METHODS: The in vitro marginal discrepancies of metal-ceramic, Auro Galvano Crown and coping were evaluated and compared. The Auro Gavano Crowns were made from one extracted maxillary central incisor prepared by milling machine. 30crowns per each system were fabricated. Measurements of a crown were recorded at 50 points that were randomly selected for marginal gap evaluation. Parametric statistical analysis was performed for the results. RESULTS: Mean marginal gap dimensions and standard deviations at the marginal opening for the anterior single crowns were 74+/-21micrometer for the control (metal-ceramic restoration), 45+/-11 micrometer for Auro Galvano Crown coping, and 51+/-9 micrometer for the Auro Galvano Crown. CONCLUSIONS: Auro Galvano Crown showed significantly smaller (P .05)

Spectrophotometric analysis of the influence of metal substrate on the color of ceramic / 대한치과보철학회지

STATEMENT OF PROBLEM: Metal-ceramic restorations have been used extensively by dental clinicians for nearly 40 years. Strength an functional ability of metal-ceramic restorations are proved to be satisfying, However esthetics and biocompatibility of metal alloy which is used in metal-ceramic restoration is not ideal. Using pure gold as an alternative, have advantage of esthetics, biocompatibility over conventional metal alloy. But there had been little article which studied on the color effect of pure gold on final porcelain color. PURPOSE: The purpose of this study was to spectrophotometrically evaluate the difference between color of metal alloy(Au-Pt, Ni-Cr) and pure gold, during color masking procedure with opaque porcelain and to analyze the differences. MATERIAL AND METHODS: Three types of metal-base metal(Ni-Cr), high gold alloy(Au-Pt), pure gold(GES)-specimen were fabricated 1cm in diameter. Four steps were established-after finishing, after pre-coditioning, after application of first opaque porcelain(0.08mm in thickness), after application of second opaque porcelain(0.15mm in thickness)- and tested color with spectrophotometer every each steps and analyzed with CIEL* a* b* color order system. One-Way ANOVA test was used to find out if there were significant differences between groups tested and Shaffe multiple comparison was used to identify where the differences were. RESULTS: 1. After finishing and pre-conditioning, pure gold(GES) group showed most high values in L*, a*, b*. 2. After application of first opaque porcelain(0.08mm in thickness), after appllication of second opaque porcelain(0.15mm in thickness), pure gold(GES) group showed the least difference in L*, a*, b* values and the lowest .E value(.E=0.63). 3. After application of first opaque porcelain and after application of second opaque porcelain differences that were significant (P< 0.05) between groups were found only in a values. 4. Base metal alloy group showed the lowest a value in test after application of first opaque porcelain and the highest value in test after application of first opaque porcelain. CONCLUSION: Pure gold group and high gold group showed higher a values than base metal group when tested after 0.08mm thickness of opaque porcelain was applied and pure gold group showed much similar L*, a*, b* values between 0.08mm thickness and 0.15mm thickness of opaque porcelain. This meant that pure gold was more easily masked by opaque porcelain than the other two groups.