| IntroductionIn this study, Ti castings were invested by three kinds of investments of which ZrO2content is respectively 30% ,40% and 50%. The castings have a 30 degree edge margin. Casting deficiency of the edge margin were measured ,the spreading of Al,Zr,P,Si and Mg chemical elements were analyzed with electron probe microanalyzer and scanned with X - ray image scanning machine. Thus, the property of casting were evaluated including accuracy of edge and thickness of reaction layer. These results were compared to the casting invested by Ti investment made in Japan, The purpose of this study is to investigate the feasibility of the ZrP99 investment being applied to Ti full crown. It will provide experimental evidence for clinical application of the ZrP99 investment with good capability and relation cheap.Materials and Methods1. Materials1. 1 ZrP99 investmentMix the powder of ZrO2 with ordinary phosphate investment to make the proportion of ZrO2 up to 30% ,40% and 50% , and respectively mark as group1,2,3. Use Morita Ti investment made in Japan as control.1. 2 Making the two - layer collection and edge margin wax pattern1.3 Pure Ti materialsPure Ti blocks were provided by Beijing Yalian Electronic Material And Technology Corp. 2. Experimental methods2.1 Insert sprue24 models were divided into 4 groups in each hoops randomly.2.2 InvestZrPgg investments were mixed respectively in proportion with distilled water in the vacual mixer. Four hoops were invested with each investment.2. 3 Roast casting hoopsThe invested hoop were placed in room temperature for 16 hour before being put into the furnace. The temperature was elevated from room temperature to 260^ at the rate of 6t per minute, kept 60 minutes raised to 850 at the same rate for 60 minutes and then cooled down to 450 naturally for 30 minutes .2.4 CastDuring casting the temperature was kept at 450 . The whole process was controlled by the computer. The electronic was 250A. The disparity of two casting room pressure was 7kgf /cm2. The weight of Ti is 30 g.2. 5 Surface handleAfter casting, the hoops were put into water immediately. After cooled down completely, the investments were removed with sand -spraying machine, pressure 4kg/cm for 20 second. The sprues was cut.3. The assay methodology3.1 Determination of cast deficiency of edge marginSix spots were randomly marked on the slope of edge margin and were divided into three groups (two spots per group). The line of each group should be vertical to the margin as fast as possible. Images were collected with microimage analyzer. The cast deficiency was determined by the distance between the two markers.3.2 Element spreading .analysiseach casting were cut longitudinally, mosaiced in phenol -formaldhyde resin, polished and tripsised and mildly eroded by 3% mixture of hydrofluoric acid and nitric acid. After being cleaned in distilled water, X - ray intensity linear distribution of Zr,P ,Si and Mg of experimental group and Al^S^Mg and Zr of control group were analysed. Then the castings were scanned with the X - ray scanning machine.Results1. The cast deficiency is respectively 133. 79 15. 26 m for groupl, 132. 87 20. 56 m for group2, 144. 13 18. 31 m for group3 and143. 73 11. 50 m for control. There is no statistically significant difference(p >0.05 ).2. Element spreading analysis2.1 The spreading depth of Si is 37 m for groupl ,28 m for group2, 25 m for group3 and 12 m for control.2.2 The spreading of Si and P is synchronic, but Si is deeper than P.2. 3 There is no specific wavelength of Mg and Zr.2.4 The spreading depth of Al in control group is 9 m.2. 5 The results of scanning is consistent with of electron probe.Discussion1. It is demonstrated that the accuracy of all the castings margin have no significantly difference by determination of cast deficiency of edge margin The cast deficiency isles than 160 m, which is the maximal count of cli... |
PDF Full Text Request