Effect of cyclic loading on reverse torque values of angled screw channel systems

Area of Science:

• Dental Implantology
• Biomaterials Science
• Mechanical Engineering

Background:

• The angled screw channel concept is increasingly used in dental restorations.
• Limited research exists on the long-term cyclic loading performance of non-axially tightened implant crowns compared to axially tightened ones.

Purpose of the Study:

• To evaluate torque application accuracy of 25-degree angled screw channel systems.
• To assess the effect of cyclic loading on reverse torque values.
• To compare the survival of angled screw channel restorations with conventional cement-retained crowns.

Main Methods:

• Four groups of 28 implants were tested: three with 25-degree angled screw channels (DY, DE, ASC) and one control with conventional abutments (UB).
• Initial and reverse torque values were recorded before and after 5 million cycles of 200-N loading.
• Preload efficiency and survival analysis were performed.

Main Results:

• Significant differences in initial torque deviation were observed among angled systems and the control.
• ASC and DE systems achieved lower initial torque values than their targets.
• All groups showed significant changes in reverse torque values after 24 hours and cyclic loading, with similar time-to-failure survival rates.

Conclusions:

• The DY angled system demonstrated comparable initial torque to the control.
• ASC and DE systems under-applied torque compared to the control.
• Despite torque variations, all tested systems exhibited similar long-term survival, though ASC crowns experienced fractures.