Effect of Thermodynamic Cyclic Loading on Screw Loosening of Tightened Versus New Abutment Screw in Bone Level and Tissue Level Implants in DIO Implant Company (In-Vitro Study).

OBJECTIVES

The loosening of abutment screws is a common mechanical complication in dental implants, potentially leading to treatment failure. It is generally believed that dynamic forces may accelerate and facilitate screw loosening. Two approaches exist to address this issue: replacing the screw or re-tightening the existing one. However, there is no consensus on the efficacy of either method in preventing re-loosening.

MATERIAL AND METHODS

In this laboratory study, 20 implant-abutment sets with a diameter of 4.5 mm were randomly placed in resin blocks simulating bone tissue. The samples were tightened with a torque of 30 N cm and subjected to 10,000 dynamic cycles in a thermocycler device at temperatures ranging from 5°C to 55°C because it is the usual temperature of the mouth while drinking or eating cold and hot things. After dynamic cycling, the torque required to unscrew the abutment screws was measured using a digital torque meter, and the torque reduction in both groups was calculated.

RESULTS

The results showed a significant reduction in the torque of abutment screws in both implant types after dynamic loading. Additionally, tissue-level implants experienced greater loosening than Bone-level implants, requiring less force to unscrew the abutment in the Tissue-level group. New screws showed less torque reduction compared to previously tightened screws. Opening torque scores in the new bone-level implants after applying the primary thermodynamic cycle (26.7 N cm) were more than in the new tissue-level implants (24.7 N cm). The torque reduction percentage values of the implant after the primary thermodynamic cycle were significantly higher in the tissue-level (17.67 N cm) group than in the bone-level (11 N cm) group.

CONCLUSIONS

Overall, dynamic loading can cause loosening of abutment screws in dental implants, with Tissue level implants being more susceptible. It is recommended to periodically replace screws with new ones to prevent torque reduction and related complications.