EFFECT OF RECASTING CO-CR ALLOYS ON THE MARGINAL FIT OF CROWN WITH SHOULDER MARGIN - AN INVITRO STUDY

Abstract

Introduction: Marginal adaptation is one of the most important and weakest links in the success of cast restorations. There is some indication that the quality of marginal adaptation may be as important to gingival health as marginal location.⁰¹

Aims and Objectives: To evaluate the marginal integrity and occlusal discrepancy of base metal alloy copings by recasting method using conventional casting technique.

Methodology: The 30 test samples were grouped into 3groups as Group I: 10 samples will be prepared using 100% new co-cr alloy.Group II: 10 samples will be prepared using 50% new alloy and 50% reused alloy.Group III:10 samples will be prepared using 25% new alloy and 75% reused alloy. The patterns obtained were casted with an induction casting machine and Co-Cr copings, the vertical gap and internal gap/occlusal discrepancy of all the 30 Co-Cr cast copings are obtained, with the use of stereo microscope.

Results: Paired t test and tukey Kramer tests were conducted to determine p value. The p value for marginal integrity  was found to be less than 0.01 which indicates that there is a significant difference between groups on buccal,lingual,mesial and distal surfaces . p value for occlusal discrepancy was found to be greater than 0.01 indicating that there is no significant  difference between groups on occlusal mesial surfaces while distal side it is less than 0.01 which is significant.

Summary and Conclusion: The patterns were prepared with inlay casting wax on the custom-made stainless steel die. 30 of the patterns were invested with a metal ring during investment.  The vertical marginal gaps of three groups cast copings obtained by conventional casting were statistically significant to each other with higher value in group 2 followed by group 3 and group 1.