An Indirect Method to Measure Abutment Screw Preload: A Pilot Study Based on Micro-CT Scanning

Area of Science:

• Biomaterials Science
• Dental Implantology
• Medical Imaging

Background:

• Dental implant stability is crucial for successful osseointegration.
• Accurate preload measurement is essential for understanding implant biomechanics.
• Different implant platform designs may influence preload distribution and retention.

Purpose of the Study:

• To measure and compare preload in external hexagon (EH) and Morse tapered (MT) dental implants.
• To evaluate the accuracy and repeatability of micro-computed tomography (micro-CT) for preload assessment.
• To analyze the relationship between preload and removal torque in different implant geometries.

Main Methods:

• Dental implants (EH and MT) were subjected to a standardized torque (20 Ncm).
• Micro-CT imaging was used to obtain virtual models of abutment screws before and after torque application.
• Screw elongation was measured from micro-CT scans to calculate preload using Hooke's Law; removal torque was also recorded.

Main Results:

• No significant difference in preload was found between EH (461.6 N) and MT (477.4 N) implants.
• The EH group exhibited significantly higher removal torque (13.8 N cm) compared to the MT group (8.2 N cm).
• Micro-CT demonstrated high accuracy (0.053% variability) and repeatability (0.23-0.28% error) for preload measurement.

Conclusions:

• Micro-CT is a viable and accurate method for calculating preload in dental implants.
• Implant platform geometry (EH vs. MT) did not significantly affect preload under the tested conditions.
• External hexagon implants may offer superior resistance to loosening compared to Morse taper implants, as indicated by removal torque.