A Comparison of Fracture Resistance of Zirconia Copings Made with CAD/CAM Technology and Slip Casting Technique

Statement of Problem: Zirconia has been introduced as an appropriate structure for fabricating metal free copings. A major advantage of such restorations is esthetic concerns; however, due to its high strength, zirconia can also be used in posterior areas. One of the recent methods of making these restorations is CAD/CAM machines. This study aimed to evaluate the fracture resistance of zirconia copings fabricated by two methods, CAD/CAM and slip casting 32 brass dies were fabricated for this study and divided into two groups of 16 dies each. Zirconia copings were made by CAD/CAM machine for one group and by slip casting method for the other. The copings were cemented to dies by a resin-modified glass ionomer (GC plus). A hardened steel ball with a diameter of 5 mm was used to apply the load to the copings in the long axis of the dies at a crosshead speed of 0.5 mm/min. Then the amount of force needed to fracture each coping was recorded. Independent Sample T-test was used to compare the two groups. The average of fracture resistance for the CAD/CAM group was 1411± 424 N and for the slip cast group it was 1542±412 N, having no significant difference (p > 0.05). Zirconia copings made by CAD/CAM and slip casting methods have no significant difference in fracture resistance.