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.
Alloys* ; Electrolytes ; Hardness ; Hardness Tests

This study examined the quality characteristics of brown rice Sulgidduk containing acorn powder and the optimal mixing rate (0%, 5%, 10%, and 15%). The moisture contents of brown rice Sulgidduk increased with increasing amount of acorn powder. The DPPH free radical scavenging activities (16.15%~28.06%) and ABTS free radical scavenging activities (22.98%~42.81%) of the brown rice Sulgidduk increased with increasing acorn powder content. The L value of the Hunter's color value decreased with increasing amount of acorn powder. The hardness and chewiness of brown rice Sulgidduk increased with increasing amount of acorn powder. The brown rice Sulgidduk containing 10% acorn powder showed the highest score with regard to the sensory characteristics. These results suggest that the most desirable amount of acorn powder is 10% and the addition of acorn powder could contribute positively toward the quality characteristics of brown rice Sulgidduk.
Hardness

The purpose of this study was to measure the flexural strength and hardness of four core materials in 4 different medias and to evaluate the relationship between the physical properties. For the flexural strength, the specimens were prepared from each of the following materials: Bisfil Core, Core Max, Fuji IX GP, Miracle Mix and randomly divided into four groups and stored at 37 degree C in the following medias: distilled water for 24 hours (DW/1), distilled water for 30 days (DW/30). 2% NaF for 30 days (NF/30), 0.02N lactic acid for 30 days (LA/30). After storage, the specimens were subjected to flexural strength testing and calculated to flexural modulus. For hardness testing, specimens were prepared from four materials and storaged in the uniform way. After storage, the specimens were subjected to Vicker's hardness testing. 1. The flexural strength of Core Max were the highest, and the flexural strength of Miracle Mix were the lowest. 2. The hardness of Bisfil Core were the highest. 3. The hardness of Core Max were the highest. 4. The hardness of Miracle Mix were the lowest. 5. 2% NaF and 0.02N lactic acid negatively affected the flexural strength and hardness of four core materials.
Hardness ; Hardness Tests ; Lactic Acid ; Water

The purpose of this study was to investigate the physical effect of tissue conditioner on polymerized acrylic resins. Surface hardness and transverse strength were measured for evaluating physical effect of tissue conditioner on polymerized acrylic resins. 1) To measured surface hardness, the resin specimens(65x10x10mm size) of each resin material were made, applied tissue conditioner, stored in 37degrees C water for 1week, and changed tissue conditioner every week for 3 weeks. Surface hardness was measured every week with Shore hardness tester for 4 weeks. 2) To measured transverse strength, the resin specimens(65x10x3mm size & 65x10x1.5mm) of each resin material were made. The specimens were divided into four groups, and measured by universial testing machine. Group I (control group) : The resin specimens were stored in 37degrees C water for 5 weeks. Group II : The resin specimens were stored in 37degrees C water for 5 weeks, and relined in 1.5mm thickness with same resin. Group III : The resin specimens were stored in 37degrees C water for 1 week, applied tissue conditioner in 1.5mm thickness, stored in 37degrees C water for 1 week, changed tissue conditioner and water every week for 3 weeks, removed tissue conditioner, reduced 1.5mm thickness from resin surface which was applied tissue conditioner, and relined in 1.5mm thickness with same resin. The following conclusions were obtained : 1. Surface hardness changes of Vertex RS and Vertex SC were not different significantly (p>0.01). 2. Surface hardness of K-33, Tokuso rebase, and Kooliner were decreased (p<0.01). 3. With the exception of Kooliner, transverse strength of all resin materials between control group and groups which applied with tissue conditioner were not different significantly (p>0.01).
Acrylic Resins* ; Hardness ; Hardness Tests ; Polymers* ; Water

STATEMENT OF PROBLEM: Implant screw loosening has been remained problem in restorative practices. Surface treatment of screw plays a role of preventing screw from loosening in implant screw mechanism. PURPOSE: The purpose of this study was to investigate surface characteristics of TiN and ZrN film ion plated screw with titanium and gold alloy screw and to evaluate wear resistance, surface roughness, and film adhesion on screw surface using various instruments. MATERIAL AND METHODS: GoldTite screws and titanium screws provided by 3i (Implant Innovation, USA) and TorqTite screws or titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, korea) were selected. Ion plating which is much superior to other surface modification techniques was carried out for gold screws and titanium screws using Ti and Zr coating materials with nitrogen gas. Ion nitrided surface of each abutment screw was observed with field emission scanning electron microscopy(FE-SEM), micro-diamond scratch tester, vickers hardness tester, and surface roughness tester. RESULTS: 1) The surface of gold screw and GoldTite is more smooth than ones of other kinds of non coated screw. 2) The ZrN and TiN coated surface is the more smooth than ones of other kinds of screw. 3) The hardness of TiN and ZrN coated surface showed higher than that of non coated surface. 4) The TiN coated titanium screw and ZrN coated gold screw have a good wear resistance and adhesion on the surface. 5) The surface of ZrN coated screw showed low surface roughness compared with the surface of TiN coated screw. CONCLUSION: It is considered that the TiN and ZrN coated screw which would prevent a screw from loosening can be appilcable to implant system and confirmed that TiN and ZrN film act as lubricant on surface of screw due to decrease of friction for recycled tightening and loosening.
Alloys ; Dental Implants* ; Friction ; Hardness ; Hardness Tests ; Nitrogen ; Tin ; Titanium

PURPOSE: The purpose of present study is to compare mechanical properties and microstructural characteristics of fractured surface for cast, 3-D printing laser sintered and CAD/CAM milled cobalt-chromium (Co-Cr) alloy specimens and to investigate whether laser sintered technique is adequate for dental applications. MATERIALS AND METHODS: Thirty six flat disc shape Co-Cr alloy specimens were fabricated for surface hardness test and divided into three groups according to the manufacturing methods; 12 specimens for casting (n=12), 12 specimens for laser sintered technology (n=12) and 12 specimens for milled technology (n=12). Twelve dumbbell shape specimens for each group were also fabricated for a tensile test. Statistical comparisons of the mechanical properties for the alloys were performed by Kruskal-Wallis test followed by Mann-Whitney and Bonferroni test. The microstructural characteristics of fractured surfaces were examined using SEM. RESULTS: There were significant differences in the mean Vickers hardness values between all groups and the cast specimen showed the highest (455.88 Hv) while the CAD/CAM milled specimen showed the lowest (243.40 Hv). Significant differences were found among the three groups for ultimate tensile strength, 0.2% yield stress, elongation, and elastic modulus. The highest ultimate tensile strength value (1442.94 MPa) was shown in the milled group and the highest 0.2% yield strength (1136.15 MPa) was shown in the laser sintered group. CONCLUSION: Different manufacturing methods influence the mechanical properties and microstructure of the fractured surfaces in Co-Cr alloys. The cast Co-Cr alloy specimens showed the highest Vickers hardness, and the CAD/CAM milled specimens revealed the highest tensile strength value. All alloys represent adequate mechanical properties satisfying the ISO standards of dental alloy.
Alloys* ; Dental Alloys ; Elastic Modulus ; Hardness ; Hardness Tests ; Tensile Strength

Purpose of this research is estimating polymerization depth of different source of light. XL 3000 for halogen light, Apollo 95E for plasma arc light and Easy cure for LED light source were used in this study. Different shade (B1 & A3) resin composites (Esthet-X, Dentsply, U.S.A.) were used to measure depth of cure. 1, 2, and 3 mm thick samples were light cured for three seconds, six seconds or 10 seconds with Apollo 95E and they were light cured with XL-3000 and Easy cure for 10 seconds, 20 seconds, or 40 seconds. Vicker's hardness test carried out after store samples for 24 hours in distilled water. Results were as following. 1. Curing time increases from all source of lights, curing depth increased(p<0.05). 2. Depth (that except 1mm group and 2mm group which lighten to halogen source of light) deepens in all groups, Vickers hardness decreased(p<0.05). 3. Vicker's hardness of A3 shade composite was lower in all depths more than B1 shade composites in group that do polymerization for 10 seconds and 20 seconds using halogen source of light(p<0.05), but group that do polymerization for 40 seconds did not show difference(p>0.05). 4. Groups that do polymerization using Plasma arc and LED source of light did not show Vicker's hardness difference according to color at surface and 1mm depth(p>0.05), but showed difference according to color at 2mm and 3mm depth(p<0.05). The results showed that Apollo 95E need more polymerization times than manufacturer's recommendation (3 seconds), and Easy cure need polymerization time of XL-3000 at least.
Hardness ; Hardness Tests ; Light ; Plasma ; Polymerization ; Polymers ; Polymethyl Methacrylate

The purpose of this in vitro study was to evaluate the efficiency of Er:YAG laser on calculus removal and the morphologic changes and hardness of the irradiated surface at different power settings. This experiment used human teeth which were extracted due to periodontal disease and had a band of calculus. Forty root slabs (5x5x2mm3) were made and divided into control group and irradiated groups. Experimental groups were as follows; Control group (root planing), Group 1 (irradiated with laser at 30mJ), Group 2 (irradiated with laser at 60mJ), Group 3 (irradiated with laser at 100mJ). Twelve root slab embedded in resin block were used in each group. Er:YAG laser was applied under water irrigation with the tip held perpendicular to the root surface in contact mode. The treatment time was measured until the calculus was removed completely under naked eyes. The efficiency of calculus removal was evaluated by the time for removal. Morphological changes of laser irradiated site were observed under SEM and the surface hardness was measured using a Vickers Hardness tester. The results were as follows; 1. The efficiency of laser scaling was increased with increasing the energy level of irradiation(p<0.05). 2. The morphological changes such as carbonization, crater and scale-like defects in the irradiated root surface were frequently observed with increasing the energy level. 3. The surface hardness increased at 60mJ and 100mJ irradiated groups than that of control group(p<0.05). From the results evaluting on the efficiency, morphological change and surface hardness, appropriate lower energy level was suggested for the clinical application of the Er:YAG laser in scaling.
Calculi* ; Carbon ; Hardness ; Hardness Tests ; Humans ; Periodontal Diseases ; Tooth ; Water

Micro-hardness of human teeth was measured by micro hardnessmentry at different depths i.e. enamal, enamelo-dentinal junction and dentin. A simulated dental friction test was conducted of respectively in these three areas, opposing pure titanium ball under a modified fretting machine. The results showed that micro-hardness is 320.40 +/- 22.77 HV of enamal, 232.26 +/- 32.31 HV of enamelo-dentinal junction, and 61.17 +/- 9.42 HV of dentin (P < 0.05). Wear depth is 17.33 +/- 0.58 microns of enamal, 49.44 +/- 16.47 microns of enamelo-dentinal junction and 95.20 +/- 15.07 microns of dentin(P < 0.05). Wear resistance of enamal is much better than that of dentin's. This preliminary investigation should be very useful in clinical applications.
Adult ; Hardness ; Hardness Tests ; methods ; Humans ; Tooth ; anatomy & histology ; physiology

Sterilization has received much attention in orthodontic practices over the past several years. The present study was undertaken to investigate the effects of sterilization on the physical properties of orthodontic pliers-AEZ, Unitek, and Dentronix ligature cutters. This study was designed to examine the tips of ligature cutters before and after 200 and 400 sterilization cycles using the Bowmar RHT-1000, the Dentronix DDS-5000, and the Eschmann SES-2000. The tip surface and the fracture surface were observed with a scanning electron microscope. The microstructure was observed with an optical microscope. The hardness test was carried out with the micro-Vickers hardness tester and the Rockwell C Scale hardness tester. The chemical composition was analyzed_ by energy dispersive X-ray spectrometer. The results of this study were as follows: 1. The number and the size of corrosion products on the tip surface and the proportion of cleavage planes in fractured specimen increased, but the hardness of the tip decreased in proportion to sterilization cycles. From these observations, it was considered that mechanical properities decreased in proportion to sterilization cycles. 2. The number and the size of chromium carbides increased in proportion to sterilization cycles. Coarse microstructure decreased mechanical properities. 3. The AEZ and Unitek ligature cutters were Fe-Cr stainless steels, but the Dentronix ligature cutter was Co-Cr alloy. There were many differences among manufactures, but the chemical composition was not changed after sterilization cycles. 4. The tip edge of ligature cutter used in a clinic revealed microcracks with the SEM observation. Clinical experience confirmed that ligature cutters were gradually degraded by sterilization.
Alloys ; Chromium ; Corrosion ; Hardness ; Hardness Tests ; Ligation ; Stainless Steel ; Sterilization*