Earticle

Purpose: The aim of this research was to investigate difference in shear bond strengths of full-contour zirconia layered with porcelain. Methods: Disk-shaped (diameter: 12.0mm; height:3.0mm) zirconia were randomly divided into six groups according to the surface conditioning method to be applied (N=90, n=15 per group): group 1-contol group(ZC); group 2- airborne particle abrasion with 50-um Al2O3(5A); group 3-50-um Al2O3 + liner(5AL), group 4-110-um Al2O3(1A); group 5-110-um Al2O3 + liner(1AL); group 6-liner(LC). On each block, zirconia porcelain was build up according to manufacturer’s instructions. All samples were fixed with measuring jigs and shear bond strength were measured with Universal testing machine. Collected data were analyzed using SPSS(Statistical Package for Social Sciences) Win 12.0 statistics program. Results: LC showed the highest value(29.92±2.55 MPa) and ZC showed the lowest value(13.22±1.37 MPa). Zirconia liner and Alumina oxide groups was significantly higher shear bond strength than control(p<0.05). 5A (without liner 22.18±2.37, with liner 22.84±1.74 MPa) was higher shear bond strength than 110 (without liner 20.18±2.38, with 20.71±2.67). Conclusion: Surface treatments may have advantage in bond strength improvement for full-contour zirconia layered with porcelain.

The aim of this study is to make some basic materials to find retention force difference based on the total height of CAD/CAM zirconia abutment used for implant, retention force difference based on how to regulate the height of the abutment, retention force difference based on the size and retention force difference based on the design group. The retention force was measured by being pulled at the speed of 1mm/min after being combined with zirconia block and abutment using Temp-BOND of Kerr. The experiment was done at the research lab of OSTEM in Busan by useing UNIVERSAL TESTING MACHINE on March 3rd, 2010. The final conclusion was reached as follows through analyzing the amessed results. 1. After analysing the total height and the retention force, p-value had minor difference by 0.01 statistically. Namely, 3㎜, 4㎜, 5㎜ had the retention force difference and we could see retention force difference on 3㎜ and 5㎜ at the post test. 2. After analyzing how to regulate the height and retention force, p-value had minor difference by 0.000 statistically. Namely, 1㎜ and 2㎜ had the retention difference and we could see that 1㎜ and 2㎜ with the total height had retention difference. 3. After analyzing the retention force based on the size, p-value had minor retention force difference by 0.000 statistically. Namely, 7 different size had retention force difference and we could see the size 21.9㎜, 32.9㎜, 32.9㎜, 38.4㎜ , 48.9㎜ and 54.9㎜ had retention force difference. 4. After analyzing the retention force based the design, p-value had retention force difference by 0.000 statistically. Namely 9 different design group had retention difference and we could see that 9 design group with 5.6.7.8 design group and 9 design group with 1.2.3.4. design group had retention force.

Purpose: Physical and chemical properties of gold is most suitable to be restored of teeth to its original state. Recently zirconia was used instead of gold because of esthetical and intimacy of human body. Because of high strength and high abrasion resistance of zirconia, all zirconia artificial tooth lead to wear the original tooth of opposite site. To preserve this original tooth, zirconia artificial tooth covered with dental ceramic glass was used. When joining the zirconia core and dental ceramic glass, difference of their thermal expansion coefficient and wetting ability is generated the residual stress at interface lead to crack. In order to solve this problem, intermediate layer what is called zir-liner was imported to decrease the residual stress and increase the bonding strength. Methods: In this study, to identify the optimum conditions for manufacturing process, various methods to rough the surface of zirconia core were adopted, and vary the thickness of interlayer, and analyzed bond strength. Results: Bond strength of sanding specimens group showed higher than that of non-sanding specimens group, and once applied intermediate layer with sanding specimens showed highest bond strength with 28 MPa. SEM photomicrographs of zirconia cores fired at 1500℃ showed parallel straight lines in sanding and pockmarked surface in blasting surfaces as abrasion traces. Observation of the destruction section after shear test by SEM were carried out. Liner applied non-sanding group and non-liner applied sanding group all showed interfacial crack. Sandblasting group with non-liner showed remained dental ceramic glass on the surface of zirconia. Sandblasting group with once applied liner showed partially remained liner and dental ceramic glass on the surface of zirconia. XRD analysis revealed that sandblasting group showed higher monoclinic peaks than other specimens group and this result was due to the high collision energy for stress induced phase transformation. Conclusions: A study on the improvement of bonding strength between zirconia and dental ceramic glass steadily carried out for the future to practical use.

Purpose: The aim of this research was to evaluate the shear bond strength of different zirconia veneering ceramics with and without liner glass materials to yttria partially-stabilized tetragonal zirconia polycrystalline(Y-TZP). Methods: Five co mmercial zirconia veneering ceramics were used in this study, E-Max(EM), Creation ZI(CR), Cercon ceram kiss(CE), Triceram(TR) and Zirkonzahn ICE(ZI). All samples were prepared according to manufacturer’s instructions. Experimental industrially manufactured Y-TZP ceramic blocks(diameter: 2.7 ; height: 13.5 ) were used in this study. Shear bond strength between zirconia ceramic coping and zirconia veneering ceramics were evaluated by the push-shear bond test. The fracture load data were analyzed using ANOVA and Scheffe’s test( =0.05). The fractured surfaces of zirconia core ceraimc and zirconia veneering ceramics were observed using a scanning electron microscope(SEM). Results: The mean shear bond strengths ranged from 20 (20.12 6.34 ) to 66.6 (66.62 10.01 ). The Triceram(TRG) showed the highest value and Creation ZI(CR) showed the lowest value. In all groups, Zirconia liner and glass material groups was significantly higher shear bond strength than without liner(P<0.05), with the exception of Cercon ceram kiss(CE)groups. Conclusion: Zirconia bonding materials may have the advantage of improved bond strength between zirconia ceramic core and veneering ceramics.

Purpose: To examine the shear bond strengths of zirconia and veneering ceramic according to their surface processing. Methods: The test samples were divided into three groups: one without zirconia surface processing, one sandblasted, and one sandblasted then 3% etched. Then veneering ceramic was fired on all test samples, and their shear bond strengths were measured. Results: The test samples of the control group (Z1) showed the lowest shear bond strengths of 21.82±1.02 MPa. The shear bond strengths of Z2 and Z3 (28.25±0.72 and 26.23±0.82 MPa, respectively) were relatively higher than those of the control group. The fracture surface of the control group showed adhesive fractures while the test groups had relatively large numbers of cohesive fractures. Conclusion: The shear bond strength was high in the test groups with surface processing while the fracture surfaces showed compound fractures of adhesive and cohesive fractures.

Purpose: This study was conducted to examine the phase transition according to the zirconia surface treatment. Methods: The specimens were divided to four groups. The first group was sintered at 1,500 and ground; the second group was sintered at 700 , ground, and sintered at 1,500 ; the third group was sintered at 1,500 , ground, and 110 -sandblasted; and the fourth group was sintered at 1,500 , ground, 110 -sandblasted, treated with 9.5% hydrofluoric acid, and ultrasonic cleaner-washed for two minutes. The monoclinic fractions were measured, and the surface was observed via SEM. Results: The monoclinic fraction was 0.13 0.19% in the control group Zr1, 1.91 0.15% in the experimental group Zr2, 7.71 0.34% in Zr3, and 8.39 0.25% in Zr4. On the surface, the phase transition hardly occurred in the control group Zr1, but it increasingly occurred in the experimental groups Zr3 and Zr4. Conclusion: The monoclinic fraction was high in the experimental groups Zr3 and Zr4. The phase transition did not occur in the control group, but increasingly occurred in the experimental

Purpose: It is to compare and evaluate the change of the wear rate and phase variation of the Zirconia before and after the sintering after the grinding by a high speed equipment manufactured for the Zirconia. Methods: The specimen of the sintered Zirconia was manufactured as size of 15㎜×15㎜×2㎜. The grinding has been applied to each of all pieces of each test groups for a minute fit for each condition at same speed of 50,000 rpm by a diamond bur at high speed handpiece with injection of the air and water. For the observation of the surface before and after the sintering of the each test piece, the cross section of it was observed as 100 magnification by a scanning electron microscope after it was coated by PT, and the diffraction analysis was performed by XDR to compare the crystal phase of the Zirconia. The average surface roughness value of all specimens were evaluated. The wear test was performed at room temperature by applying a load of 1kg for 120,000 cycles for the chewing period 6 months. Wear was analyzed for the enamel cusps by measurement of the vertical substance loss with a laser scanner. Conclusion: The phase variation from the tetragonal phase to the monoclinic phase was confirmed in the test group of the pre-sintered Zirconia after the grinding, and the value of the surface roughness and the wear rate was increased in experimental group.

Purpose: This study was to observe the surface and interfacial characteristic of Zirconia by surface treatment. And it was observed the roughness and contact angle according to processing, and the interfacial properties by surface treatment on zirconia. Methods: The oxide formation and ion diffusion between core and veneer ceramic were determined by the X-ray Dot Mapping of EPMA(Electron probe micro analyzer). The roughness was measured by 3D Digital microscope and the contact angle according to processing of zirconia was observed using distilled water on the surface. Results: The surface roughness of the specimens Z04, Z12, Z15 was measured 0.67(±0.03)um, 0.50(±0.12)um, 0.35(±0.09)um, respectively. As results of contact angle test, Z04, Z12, Z15 of specimen group without binder treatment was measured 46.79(±3.17) , 57.47(±4.83) , 56.19(±2.66) , respectively. but, L04, L12, L15 of specimen group without binder treatment was measured 63.84(±2.20) , 66.08(±0.16) , 65.10(±1.01) , respectively. Average contact angle of L15 was measured 65.10(±1.01) . In X-ray Dot Mapping results, thickness of binder including Al element was measured that each of L04, L12, L15 were 20um, 15um, 10um. Conclusion: The more rough surface increases the wettability, but the sintered exclusive binder decreases the wettability.

Purpose: In this study, in order to provide objective standard of the mixed concentration of the zirconia coloringliquids,compare the shade differences after colored zirconia blocks from different concentrations. Methods: After immersion for 2 minutes zirconia specimen (1.5 1.5 0.6 0.01 ) in coloring-liquids that produced different concentrations, were sintered in furnace dedicated. Then, it was measured in spectrophotometer and Shadepilot. It has been determined mean and standard deviation of the color difference for each group, and verified by one-way ANOVA using the (version12.0) SPSS WIN Program the difference in shade according to the concentration at the significance level of 95% confidence, it conducted a Tukey’s multiple range test to post-test. Results: The mean of L* was decreased toward LN35 group, however the mean of a and b was increased(p<.05). There is a statistically significant difference in the results of L post hoc test of each group was LN15-LN30/LN35,LN20-LN30/LN35, LN25-LN30/LN35, and LN30-LN35 group. The a* group, it was found that there is a statistically significant difference in all groups for each(p<.05). The b* group, it was found that there is a statistically significant difference in all groups except the LN25-LN30(p<.05). Conclusion: In order to make effective use of the coloring-liquids of zirconia, the device objective, accurate concentration measurement is required, from the present study, we presented evidence basic to this.

Purpose: Thy yttria tetragonal zirconia polycrystalline(Y-TZP) is a good structural ceramic for dental restoration. But it have a problem that delamination of veneering ceramic from the Y-TZP core materials. The problem generally occur at the interface, thus this study was conducted to evaluate the interface of Y-TZP using scanning electron microscopy(SEM). Methods: To investigate this aspect, high-resolution SEM observations were made of polished and etched (HF content gel) cross-sections of the interface area. Dry and moist veneering porcelain powders were built up on the zirconia base. Results: The extent of this surface faceting is dependent upon the moisture content of the porcelain powder and the firing temperature. More moisture and higher final heating temperature accelerates the observed faceting of the Y-TZP grains at the interface to the veneering ceramic. Conclusion: These changes of the Y-TZP grains indicate that destabilization of the tetragonal phase of zirconia occurs at the interface during veneering with ceramic. It may result in a reduction of the stability of the zirconia and interface.

Purpose: Zirconia blocks for all ceramic dentures are divided into two groups. One is pre-heated block and the other is binder added block. In this study, the possibility of recycling the remained parts of binder added block after CAD/CAM machining with slip casting process was investigated. Methods: Owing to the binder added block contain large amount of organic matter, Binder burn-out was must be carried out before ball milling for preparing the casting slip. Binder burn-out was accomplished at 600 for 10 hours. Ball milling was performed with 5 zirconia ball and 60 polyethylene bottle. From 0% to 5% at 1% intervals of alumina was added to zirconia powder for preparing slip. Solid casting was achieved with plaster mold. Cast bodies were dried and sintered at 1,500 for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM, EDS and XRD analysis were executed. Results: Optimum slips for casting was prepared with 300g ball, 100g powder, and 180g distilled water. Cast body without alumina showed 26% of linear shrinkage, 6.07 of apparent density, and 470 of three point bend strength. On the other hand, as received zirconia block, which was sintered at the same conditions, showed 23% of linear shrinkage, 6.10 of apparent density, and 680 of three point bend strength. When 3% of alumina was added to zirconia, sintered body showed 23% of linear shrinkage, 6.10 of apparent density, and 780 of three point bend strength. SEM photomicrographs and EDS analysis showed alumina particles uniformly dispersed in zirconia matrix, and XRD analysis showed no phase transformation of tetragonal zirconia particles was occurred when alumina was added. Conclusion: According to the all of this experimental results, 3% of alumina added cast zirconia body showed excellent mechanical properties more than as received binder containing zirconia block

Purpose: All ceramic crown, made from zirconia instead of metal for core material, is recognized the best esthetical prosthesis. Recently, high-priced zirconia blocks and expensive CAD/CAM machines come into use for making zirconia core. In this study, slip casting process is adapted to evaluate the possibility of the recycling the remained parts of zirconia block after machining. Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh sieve. Passed powders were ball milled under various conditions to obtain the optimum zirconia slip for casting. Solid casting method was used for casting the specimens with plaster mold. Formed specimens were dried and biscuit fired at 1,000 for 1 hour. Biscuit fired specimens were finished with exact shape of square pillar. Finished specimens were fired from 1,200 to 1,550 at 50 intervals for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM. Results: Above examinations indicated that the optimum firing temperture was 1,500 , and when fired at this temperature for 1 hour, apparent porosity was 0% and flexural strength was 680 . SEM photomicrographs showed uniform 200~300 grain size, which is equal with microcture of sintered commercial zirconia block. when compare 24% linear shrinkage of cast specimen with 20% linear shrinkage of CAD/CAM machined block, it was estimated that the size controlling of cast core was not so difficult. Conclusion: According to the all of this experimental results, the cast zirconia core produced from the remained parts of zirconia block was possible to use for all ceramic denture.

Purpose : This study was intended to investigate the effect of applying liner for chemical bonding and physical surface roughness created on zirconia by using a sandpaper before sintering on the bond strength between the two materials. Methods: Zirconia blocks were cut using a low-speed cutter. Plate-shaped specimen(6mm×6mm×3mm) was fabricated by sintering after giving surface roughness according to four kinds of sandpapers. Depending on whether or not to use liner, 60 specimens were divided into two groups ZN(non-liner), ZL(liner), and the two groups were subdivided into four groups respectively in accordance with sandpaper used, totaling eight groups (n=10). The surface roughness (Ra) values and shapes before sintering were observed, and shear bond strength after pressing ceramic plasticity was measured with a universal testing machine. For a test of the significance, a one-way ANOVA was performed, and Tukey's multiple comparison test was conducted. Results: The observation of the surface roughness was SB04(2.22±1.16㎛), SB08(2.98±0.33㎛), SB12(2.44±1.32㎛), SB20(2.34±0.59㎛) and SA04(2.34±0.67㎛), SA08(1.28±0.90㎛), SA12(2.03±1.60㎛), SA20(2.19±1.73㎛). In the case of ZN Group, the shear bond strength was ZN04(23.26±3.83㎫), ZN08(21.76±2.33㎫), ZN12(20.49±3.01㎫), ZN20(24.98±4.22㎫)(p<0.05). As for ZL Group, the shear bond strength was ZL04(25.09±5.67㎫), ZL08(22.98±2.26㎫), ZL12(21.54±5.70㎫), ZL20(23.98±3.23㎫)(p<0.05). Conclusion: The research results showed that the bond strength of Zirconia core and Pressing ceramic was further improved by physical surface treatment before sintering, rather than by chemical bonding through liner surface treatment.

Purpose: This study is making a dog dental prosthesis using digital dental technology. The mechanical strength of the prosthetic material was observed in terms of compressive strength and fracture pattern. Methods: The experiment was performed using dog mandibular molars. The teeth were scanned and modeled. The specimens were made of zirconia, PMMA and Ni-Cr. The specimens were subjected to a vertical compression test with an artificial cancellous bone in UTM tester. Vertical compressive strength and fracture behavior of specimen were observed. Results: The result of observing the compressive load between specimen and artificial bone were 184.8 ± 5.7 N in the zirconia specimen, 185.6 ± 8.9 N in the PMMA specimen, and 184.4 ± 4.0 N in the Ni-Cr alloy specimen. Compression marks of artificial bones were observed. The fracture strength of specimen was observed. The fracture strength of the zirconia specimen was an average of 1,381.4N. The fracture strength of the PMMA specimen was an average of 572.2N. Conclusion: The crown made of three kinds(zirconia, PMMA, Ni-Cr alloy) of materials has the strength to chew about the artificial bone. zirconia and PMMA have vertical compressive strength applicable to medium dog dental prosthetic materials.

Purpose: The purpose of this study was to know of photopolymerization effect of self-etch dual-cured resin cement on different transmittance and thickness of zirconia disks. Methods: The two types of transparent and opaque zirconia speciments were prepared. The five speciments of each groups were seperated with 0.5㎜ and 1.0mm thickness. Degree of conversion(DC) were studied by FT-IR spectroscopy using ATR method before and after irradidaion for 40 sec. Results: The relative DC was showed the higher results of ZS5 as compared with ZS10 (p < 0.05). And OP5 and OP10 were lower results than ZS10 (p < 0.05). Conclusion: The photopolymerization effect of dual-cured resin cement were affected by the transmittance and thickness of zirconia.

Purpose : This study was to investigate usage satisfaction of multi type handpiece with equipped air-jet function Methods : The subjects of this study through the survey was conducted for fifty-nine dental technicians in Daegu and Gyeongsangbukdo from the May 7 to 19, after the June 23 to July 4 2014. The survey was about the function and quality through user testing environment by cutting zirconia specimens using appliance for zirconia. The collected date was analyzed by the statistical program SPSS Win Ver 19.0 for the satisfaction of handpiece and control system. To test for significance on each item, p<0.05 had been decided a standard. General characteristics and relationship between the handpiece and control system was performed correlation analysis. Results : The results of this study is as follows. 35 dental technicians had 1~2 years career in zirconia part as the highest 59.3%, 95% of subjects expected that the prospects for the zirconia material have bright prospects. The satisfaction of multi type handpiece and control system design and function showed a significant difference. Subjects satisfied with the design and function of the multi type showed negative correlation with those of Standard. The satisfaction of multi type handpiece showed 3.37 points of air jet, 3.05 points of noise level, 2.69 points of water flow rate, and 1.98 points of cruise function. Sample differences in all parameters showed a statistically higher difference. Conclusions : High-speed cutting mechanism of multi-type is recommended working with zirconia materials and the multi-type unit combined handpiece motor, air-turbine and air-gun will be expected the increase of user due to the high satisfaction of air jet.

Purpose: The purpose of this study was to investigate the transmittance differences of pressable ceramic core due to thickness within the visible light spectrum. Methods: 36 specimens were divided into 2 groups (0.6 , 0.8 ) which have each 3 specimens. The size of specimens was 10mm high and 10 wide. The transmittance of specimens are measured by spectrophotometer Model Cary 500 that can measure infrared-ray, visible wave and ultraviolet-ray. Results: The results shows that there was no significant difference between specimen’s thickness(0.6 , 0.8 ) and transmittance. Conclusion: The individual’s color perception is personal and there are numerous factors that influence on it. In general, human eye can perceive the color of thing only within visible light spectrum but in this experiment through spectrophotometer there was no big difference between specimen’s thickness(0.6 , 0.8 ) and transmittance. To sum up, The most important factors were a layed porcelain structure and its thickness rather than core thickness in the porcelain crown. Also, When making all ceramic core with dead pulp(nervous treatment tooth) when used as a restorative esthetic think is more efficient to improve.

Purpose: The purpose of this study was to evaluate flexural strength of full zirconia crown using block after clinical work. Methods: The three point bending test was used to measure the flexural strength of zirconia block. Statistical analysis was done using the Statistical Package for Social Sciences version 19.0 for Windows. As for the analysis methods, the study used analysis of variance, Tukey’'s test. Results: The ave Rage value of flexural strengths of WIELAND, Zirkonzahn, Hass, D-MAX were 516.2 , 612.6 , 566.2 , 744.6 . The ave Rage value of Surface Roughness of WIELAND, Zirkonzahn, Hass, D-MAX were 0.39Ra, 0.33Ra, 0.33Ra, 0.47Ra. Conclusion: Flexural strength of zirconia block decreased after clinical work. Flexural strength of zirconia block is equal to or higher than flexural strength of dental metal, so zirconia block can be used as dental material.

Purpose: The purpose of this study was to compare two-dimensional fitness of the monolithic zirconia prosthesis by using different type of scanner. Methods: No. 26 abutment tooth of FDI system was selected for the study. Using the extraoral scanner and intraoral scanner, the abutment tooth was scanned 10 times and the scanned files were saved as STL files. CAD/CAM system was used to produce the monolithic zirconia prosthesis. marginal and internal gap of the monolithic zirconia prosthesis were measured by digital microscope(x160) and applied silicone replica technique was applied. t-test, a statistical software, was used to perform data analysis. Results: Marginal gap mean±SD of the monolithic zirconia prosthesis was 33±7.5㎛ with extra oral scanner and 34.7±11.1㎛ with intraoral scanner. axial gap mean was 40.5±3.5㎛ with extra oral scanner and 44.6±11.6㎛ with intraoral scanner. occlusal gap mean was 110.1±25.4㎛ with extra oral scanner and 64±9.7㎛ with intraoral scanner. Conclusion: In this study, fabricating zirconia prosthesis with different type of scanner was clinically applicable.