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

Abstract

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.