Manual closing torque in five implant abutment systems: an in vitro comparative study

Area of Science:

• Dental Implantology
• Biomaterials Engineering
• Prosthodontics

Background:

• Abutment/implant (A/I) assemblies are prone to loosening under functional loads.
• Ensuring adequate preload is critical for the long-term stability of dental restorations.

Purpose of the Study:

• To evaluate the maximum manual closing torque applied to abutment/implant assemblies.
• To compare manually generated torque with manufacturer-recommended closing torque values across five dental implant systems.

Main Methods:

• An in vitro study utilizing a mannequin and torque gauge assembly.
• Nine operators applied closing torque using five different manual torque drivers.
• Torque measurements were recorded for both habitual and maximum manual closures.

Main Results:

• Significant differences in closing torque were observed between operators (P <.0001) and implant systems (P <.0001).
• Mean closing torque ranged from 7 to 14.6 N/cm for habitual closures and 9.4 to 19.9 N/cm for maximum closures.
• Maximum manual closure torque did not reach recommended levels for any tested system.

Conclusions:

• Manual tightening of abutment/implant assemblies frequently fails to achieve recommended torque values.
• Substantial interoperator and intraoperator variability exists in manual torque application.
• Driver diameter and grip likely influence the generation of closing torque.