Study In Precision Of Casting Crown With Bonded Investments In Different Proportion And Increased Temperature Means

Objections: To investigate the effect of the precision of casting crown with phosphate-bonded investment with different proportion and ascending temperature means, in order to direct choosing appropriate investments and means, improve the accuracy of casting in clinic. Methods: We chose molar as our objects, made taper brass-caped testing flip, it's aggregate angle was 6.8°, shoulder was 90°and width was 1.0mm. We used corresponding brass cannulation to control the fusing mode's height and width, the difference of it's height was 1.8±0.1mm. We used liquid paraffin as separating varnish to spread in the tooting. Then we covered the inner part of the tooting to the outer part of it, took a big wax scoop to melt the inlay wax, when the wax was melted, we put them into the tooting. When the wax was cooling to the room temperature, we divided the inner part and the outer part of the tooting, then we obtained the full crown wax model. After that, we used non-band embedding method to band 8 casting rings, in which there were 2 casting rings with Bellavest fast band investment, the proportion of the special liquid of the bond investment was 60%, 100%, respectively. The method of ascending the temperature was fast speed method. And there were 3 casting rings with Bellavest fast band investment, the proportion of the special liquid of the bond investment was 80%, 3 casting rings with pro-vest fast band investment, the proportion of the special liquid of the bond investment was 40%. The method of ascending the temperature of the 6 casting rings was fast speed after embedding 0.5 hour, then embedded 1 hour, after that, low speed 24 hours. After embedding, we did high-frequency centrifugal force casting, sand blasted and fitted. Then we used additional type silicone rubber impression material to obtain the clearance model between the casting crown and tooting, observed the thickness of the silicone rubber impression film and took pictures with metallurgical microscope, measured the thickness of the silicone rubber impression film with metallurgical analysis software system, so that we could get the value of the clearance between the casting crown and tooting, measured the width of the silicon rubber impression film at the top of silicon rubber impression model, 1 mm from axis face to the top, 1 mm from axis face to tooting, when we fitted the casting crown to the tooting, we could use the photo took by the metallurgical microscope and measured the margin opening of the casting crown. Results: In the three groups of the fast speed ascending temperature methods used Bellavest fast band investment with the proportion of the special liquid of the bond investment was 60%, 80%, 100%, respectively. There were statistic meanings in the thickness of top side of the silicone rubber impression film, the margin opening of the metal. But there was no statistic meaning in the thickness of the axis side. When we compared with different methods of ascending temperature between the two fast embedding materials of Bellavest with 80% special liquid and Pro-vest with 40% special liquid, there were no statistic meaning in those three variables. Conclusions: There is significant difference in effecting of the precision of the casting full crown with different proportion of phosphate-bonded investment. But there is no significant difference in effecting of that with different methods of ascending the temperature. In the same conditions, the precision of the casting full crown used Bellavest fast band investment is higher than Pro-vest fast band investment.