Fracture Resistance of Five Different Metal Framework Designs for Metal-Ceramic Restorations

Purpose: This study evaluated fracture resistance of five different metal framework designs for metal-ceramic restorations. Materials and Methods: Twenty-five artificial crowns were fabricated with different degrees of facial metal reduction: metal collar (group 1), and 0, 0.5, 1, and 1.5 mm (groups 2 to 5, respectively). All of the crowns were thermocycled in two different baths of 5 and 60°C for 20 seconds and had a dwell time of 10 seconds in a resting bath at 37°C for 510 cycles. The artificial crowns were then subjected to vertical loading until fracture with a Shimadzu testing machine at a crosshead speed of 1 mm/min. The load at fracture was recorded. Results: There were no statistically significant differences between mean fracture strength of groups 1 and 2 or between groups 4 and 5. There were significant differences between group 3 and groups 1, 2, 4, and 5. Conclusion: As the amount of metal reduction increased, the vertical fracture resistance decreased. Failure loads for all test groups exceeded normal biting forces.