Abutment screw torque changes with straight and angled screw-access channels.

Area of Science:

• Dental Implantology
• Prosthodontics
• Biomaterials Science

Background:

• Angle-correcting options enable screw-retained implant prostheses (SRCs) with facial-inclined implants.
• Manufacturer torque value variations raise questions about the performance equivalence of angulated versus traditional SRCs under cyclic loading.

Purpose of the Study:

• To compare torque differences in conventional straight-line screw access and angulated access SRCs.
• To evaluate torque retention before and after simulated functional loading in vitro.

Main Methods:

• Five groups of 10 SRCs and implants were tested: NB-20, DA-20, C3D-20 (20-degree access), NB-0 (0-degree access), and GA-0 (gold alloy).
• Specimens underwent thermocycling, preload torque application, and reverse torque measurements before cyclic loading (1 million cycles at 0-100 N).
• Post-cyclic loading torque measurements determined percentage torque loss.

Main Results:

• No significant torque loss differences were found between 0-degree and 20-degree SRCs after cyclic loading.
• DA-20 and C3D-20 showed significantly higher torque loss than NB-0; C3D-20 had 34.5% loss.
• The GA-0 group exhibited the highest overall torque loss (35.9%); no crown mobility was observed.

Conclusions:

• Angulated access channel crowns demonstrated comparable percentage torque values to conventional SRCs post-loading.
• Angulated access crowns with lower manufacturer-recommended torque values experienced greater percentage torque differences.