| Objective: The purpose of this study was to evaluate the bond strengthof porcelain and pure titanium fabricated by CAD/CAM and cast technology.This experiment explores the effect of these two kinds of different processingtechnology on titanium-ceramic bonding strength and aim to provideexperimental and theoretical evidence for the improvement of mental-ceramictitanium-ceramic bonding strength.Method:1Specimen making: Design a three-dimensional model of25mm×3mm×0.6mm and transfer it to the CAM system. Then the CAM control system ofmachine tool cutting out of ten pure titanium specimens experimentalrequirements, such as the A group. Ten rectangular wax patters were makingby a double-layer0.3mm thick dental wax based on the above dimensions.According to the pure titanium casting requirements, sprue was placed.Invested it with magnesium oxide embedded material for pure titanium, cast itwith pure titanium special casting machine and the obtained specimens weregrouped as B. The two groups of pure titanium specimens was burnished withtungsten carbide bur at low speed (<10000rpm) and flattened the surface inthe same direction by grinding and polishing on coarse, medium and finegrained alumina polishing strip. In the process, control specimen thicknesswas maintained0.5±0.05mm range with an electronic digital caliper. Then itwas sand-blasted by the100-μ m aluminum oxide particles for20s,passivated the specimens for ten minutes after Rinsing by running water. Thenall specimens were ultrasonically cleaned in distilled water sample for twominutes and made them dry fully. At the central8mm area of the surface of25mm×3mm titanium side, combination agent Ti-Bond was coated by puretitanium special porcelain-Duceratin Kiss ceramic powder (DK ceramic powder). First, combination agent Ti-Bond was coated immediately withglass rod after the specimens dry fully and sinter them according to theprocess that the manufacturers provided. Second, sheltered ceramic wascoated by two steps-method with glass rod and kept the thickness0.1mm±0.01mm, which were burned according to the programs provided by themanufacturer. Then, dentin porcelain was coated and the thickness was keptabout1mm±0.1mm, which were burned according to the manufactureinstruction. Dressed porcelain body with the same grinding machine and thesame speed grinding of each specimen, force must be gentle. The size ofporcelain body was in (8±0.1) mm×(3±0.1) mm×(1.1±0.1) mm range.Finally, glaze to the specimens. All the steps such as grinding, polishing,sandblasting, passivating, distilled water cleaning and coating layer should goon consecutively. All the specimens divided in2group randomly, each grouphaving8in number and was ready for three point bending test. The remainingspecimens were polished on the lateral side. One specimen was selected forscanning electron microscope analysis or observation and the other wasselected for energy spectrum analysis.2Three point bending test: According to the ISO9693standard, placedthe porcelain sintered titanium porcelain specimens in the universal testingmachine. The distance between the two supporting points were20mm. Theradius of curvature of fulcrum points and pressure heads were1.0mm.Specimen porcelain faced the force loading surface. Vertical pressure wasapplied in the center of corresponding titanium ceramic body load at the speedof1.0mm/min until one end of the ceramic layer broke and recorded thefracture force values--Ffail(N) at the fracturing moments. Calculated thebonding strength of titanium porcelain by formula rb=k Ffail.3Scanning Electron Microscope observations: Selected one specimenfrom the reserved titanium porcelains randomly and placed in the sample table.Then measured surface were sprayed with gold powder. Observe themorphology and structure of the porcelain with titanium by scanning electronmicroscope. 4Energy Dispersive Spectrometer analyses: The remaining titaniumporcelain specimens were placed in the sample table and measured surfacewere upward. The titanium-ceramic combination interface were examined byline mode multipoint scanning with EDS. Observed specimen, content anddistribution of the elements in titanium substrate and the ceramic layer oftitanium porcelain bonding interface elements from10μm.5Statistical analysis: Experimental data were analyzed with SPSS13.0statistical software. Independent-samples t-test was chosen such as datanormality and homogeneity of variance. If the data is not normal or variancenot neat, separate variance estimation(t′test) or Wilcoxon rank sum test wasselected. The test level wasα=0.05.Result:1Eye observation of two groups of titanium specimens: Group ASurface of the CAD/CAM pure titanium specimen is clean and smooth. GroupB Casting pure titanium specimen has residual embedding material attached tothe surface.2The results of three-point bending test: Group A Bond strength ofporcelain to CAD/CAM pure titanium was35.95±3.74MPa. Group BBond strength of porcelain to casting pure titanium was28.37±1.98MPa.Exploratory analysis showed that two sets of dates were normal andhomogeneity of variance. Independent-samples t-test showed there werestatistically significant differences in A, B two groups of the titanium-ceramicbonding strength（P﹤0.05）.3The results of Scanning Electron Microscope: Group A Titanium andporcelain combined closely, and no obvious pores existed in titanium-ceramiccombining surface. Group B Titanium-ceramic bonding interface has smallpore.4The results of Energy Dispersive Spectrometer: Elements such as Ti, Si,O, Na, K, Al and Ce exist in two groups of pure titanium porcelain specimens’bonding zone and Zr only exists in group A. Conclusion:1The bonding strength of porcelain to CAD/CAM pure titanium isgreater than porcelain to casting pure titanium and the difference wasstatistically significant.2The bond strength of porcelain to CAD/CAM and cast pure titanium ismore than25MPa, the standard of ISO, which meet the requirements ofclinical application. |
PDF Full Text Request