Screw Preload Analysis in a Repeated Torque of Variobase Type Abutments

Area of Science:

• Biomaterials Science
• Dental Implantology
• Mechanical Engineering

Background:

• Implant-abutment connections are critical for prosthetic stability.
• Understanding the mechanical behavior of different Variobase configurations under cyclic loading is essential.

Purpose of the Study:

• To quantify preload efficiency (PE%) and energy transfer (Et/Er) in Variobase implant-abutment assemblies over ten torque cycles.
• To compare the performance of Regular-Neck (RN) and Regular-CrossFit (RC) interfaces under repeated loading.

Main Methods:

• Four Variobase configurations (RNC, RNB, RCC, RCB) were tested in ten repeated tightening-loosening cycles at 35 Ncm.
• A linear-torsion testing machine was used, and friction fit was assessed after cycles 5 and 10.

Main Results:

• Preload efficiency (PE%) decreased progressively with repeated cycles in most groups.
• Regular-Neck (RN) interfaces showed better preload stability and predictability compared to bone-level (RC) assemblies.
• Friction fit, observed only in RC groups, significantly impacted energy loss and torque-angle signatures.

Conclusions:

• Initial PE% is highest in new assemblies, with RN connections maintaining superior stability over repeated cycles.
• RC interfaces exhibit lower, more variable PE% and energy profiles, influenced by friction fit.
• Understanding these platform-specific variations is key for clinicians to enhance long-term prosthetic stability and minimize screw loosening.