Reverse Torque and Wear of Internal Connections of Metal-Based Abutments Under Cyclic Loading

Objective: Evaluate the reverse torque values and wear of internal connections caused by metal-based zirconia abutments under cyclic loading. Material and Methods: Thirty implants were divided into three groups (n = 10), based on connection systems: Interference-fit cone-screw (Cortical Master Flash MI Fit—MTA and Cortical Master Flash MI RP—MTB), and Internal hexagon (Cortical Titanium Master Connect AR—IH). Metal-based zirconia abutments were tightened into the implant, and zirconia crowns were bonded using resin cement. All specimens underwent cyclic loading at 300 N and 9 Hz for 1,000,000 cycles. Reverse torques were assessed postloading, and wear was analyzed using scanning electron microscopy (SEM). Statistical analysis employed one-way ANOVA for reverse torque and wear values, with significant differences assessed via the Tukey test (α = 0.05). Results: Significant differences in reverse torque values were found among groups: MTA (24.9 N), MTB (24.1 N), and IH (14.4 N). The IH group showed higher mean wear values on the tension side (121.0) and compression side (112.6), with a wear difference of 8.4. Conclusion: The interference-fit cone-screw abutments demonstrated significantly reduced torque loss and morphology after cyclic loading, reflecting enhanced performance. Clinical Significance: Although the stability of the metal base zirconia abutments to the implants was accurate, clinicians should be cautious about torque loss and more wear when using internal hexagon connections.