A Study on Mechanical Advantages of Angulated Abutments for Implants

Objectives: The present study was to investigate whether the angulated abutment has mechanical advantages for the implants placed with the inclination to the vertical by the stress analysis with 3-dimensional finite element methods (FEM), and by measuring the release torque of the screw to which the cyclic loading test (CLT) was employed. Methods: FEM analysis: Two FEM models, a model with standard abutments (STD) and that with angulated abutments (ANG), were generated. Each model included a fixture, 4mm in diameter and 13mm in length, that was installed in the mandibular posterior region with the inclination of 17 degrees to the vertical. The models were analyzed using the ANSYS Ver. 5.6 software program (Swanson Analysis Systems, USA) and the stress values were compared. The static load of 100N was applied. CLT: Ten fixture replicas (Novel Biocare, SWEDEN) were embedded in the aluminum block with 17-degrees inclined to the vertical. Five straight abutments and five angulated abutments(Novel Biocare, SWEDEN) were placed on the fixture replica. The load of 78.4N for 100,000 cycles was applied to each specimen. The release torque values of retaining screws were measured using the torque gauge (TONICHI, JAPAN), and results were submitted to the statistical analysis. Results: The result of FEM analysis revealed that the stress values in the implant components for ANG showed 30% reduction from that for STD. The results of CLT experiment showed that the release torque of the screw for ANG was significantly greater than that for STD (p< 0.001, t test). Conclusion: The introduction of the angulated abutment reduced the stresses in the implant components, and increased the release torque of the retaining screw after the employment of CLT. Therefore, it was suggested the angulated abutments have mechanical advantages for the implants placed with the inclination to the vertical.