|| Print ISSN: 2589-7837 || Online ISSN: 2581-3935 || International Journal of Medical Science and Diagnosis Research (IJMSDR) Available Online at www.ijmsdr.com NLM (National Library of Medicine ID: 101738824) Original Research Article Volume 4, Issue 11; November: 2020; Page No. 34-37 34 | Page EFFECT OF RECASTING CO-CR ALLOYS ON THE MARGINAL FIT OF CROWN WITH SHOULDER MARGIN - AN INVITRO STUDY N. Ranjith Kumar 1 , G. Sheela Prakash 2 , B.Vinay Goud 3 1 Asssisstant Professor, Department of Prosthodontics Crown & Bridge, Malla Reddy Dental College For Women Hyderabad 2 Senior Resident, Department of Oral & Maxillofacial Surgery, Government Dental College, Hyderabad 3 Senior Resident Department of Conservative Dentistry & Endodontics, Government Dental College, Hyderabad Conflicts of Interest: Nil Corresponding author: N. Ranjith Kumar DOI: https://doi.org/10.32553/ijmsdr.v4i11.710 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. Introduction: Casting procedures requires use of more metal than is needed to produce a restoration. Dental laboratories often reuse the casting surplus to produce castings when high cost alloy are used. Marginal adaptation is one of the most important and weakest links in the success of cast restorations. 1 The base metal alloys were introduced in dentistry in 1930 by R.W.Eardle and C.H Prange. These alloys were so inexpensive that every time casting was performed using new alloy ingot and left over metal was either discarded or sold back. 2 Due to toxicity of nickel and beryllium, cobalt-chromium alloys for use in metal ceramic restorations were developed which are corrosive resistant and biological environments. Marginal and internal accuracy of fit is an important consideration for success of complete coverage crowns. 3 Results have shown that repeated casting could interfere with composition of alloy by reducing elements such as copper, tin, zinc, chromium, and titanium. 4 Therefore, this study was designed to evaluate the vertical marginal fitness and internal fit of metal copings of cobalt-chromium alloy produced from three different base metal alloys(100new, 50new+50recasted, and 25new+75recasted) using shoulder finish line. 5 Methodology: An invitro study was conducted at the Department of Prosthodontics, G.Pulla Reddy dental college and hospital, Kurnool, to comparatively evaluate the marginal fit and occlusal discrepancy of Co-Cr copings obtained by recasting the alloy. A custom made stainless steel die was made with appropriate dimensions of maxillary first molar. 30 test samples were grouped into 3 groups of which 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. These 30 patterns were prepared using inlay casting wax patterns were prepared to obtain a uniform thickness of