Implant Screw Tightening — Torque and Control Parameters

Tightening an implant screw "by feel" is a clinical error. Both undertightening and overtightening have consequences – loosening or fracture of the screw. Below, we've compiled parameters and procedures from daily clinical and laboratory practice.

What is torque?

Torque is the rotational force expressed in Newton centimeters (Ncm) that must be applied to a screw to achieve stable preload without the risk of damage. Each implant system manufacturer provides recommended values in the technical data sheet.

The value is not the same for all screws – it depends on the system and the type of connection (external/internal, locking taper).

Tightening Parameters — System Overview

Always verify with the manufacturer's technical data sheet for the specific implant lot.

Proper Tightening Procedure

1. Use a torque wrench calibrated by the manufacturer – not a regular hex key.
2. Tighten slowly, with a steady motion – rapid tightening does not allow for even force distribution.
3. Wait 10 seconds after the initial tightening and repeat – the screw "seats" and loses some of its initial preload.
4. Document the Ncm value in the patient's record – essential for eventual disassembly.
5. For multiple implants, tighten in a cross-pattern, not sequentially.

Most Common Errors

Undertightening – the screw does not achieve the required preload. Result: loosening under functional forces within the first few weeks of use.

Overtightening – exceeding the manufacturer's recommended value can cause permanent deformation of the thread or screw fracture. With locking taper connections, the risk is particularly high.

Lack of documentation – during subsequent disassembly (aesthetic revision, repair), you do not know the force with which the screw was seated. Lack of documentation carries the risk of component damage during removal.

Loose screw – what to do? Loosening within the first 6 months is the most common time for the problem to occur. Procedure: remove the prosthesis, replace the screw (do not re-tighten the loosened one), tighten to the correct torque, document. Loosening can also indicate occlusal overload – check occlusion before re-seating.