Evaluation and comparison of the effect of three different finish line designs on the marginal discrepancy of zirconia copings - An in vitro study

Statement of problem: This study was designed to compare the marginal discrepancy of zirconia copings (Ziecon) with heavy chamfer, shoulder and rounded shoulder finish line, pre and post-cementation to provide clinicians a guideline for tooth preparation and cementation.
Material and method: Stainless steel die was fabricated for each finish line design and duplicated with addition silicone impression material to obtain dies in Type IV die stone (n=60). The specimens were tested for marginal discrepancies before cementation, post-cementation and after sectioning. Marginal discrepancies were recorded in microns, statistically analyzed, and compared.
Results: Finish line designs significantly influenced the marginal fit of the zirconia copings (p >0.05) and their mean marginal fit was acceptable for clinical application ( 120 μm). Mean marginal discrepancies post-cementation were larger than respective pre-cementation values. Shoulder specimens exhibited least discrepancy. In sectioned specimens, marginal gaps were lowest and occlusal gaps were highest.