Rotational Load Fatigue Performance of Ti-6Al-4V ELI Implants with One-Size Implant-Abutment Connection

To investigate the rotational load fatigue performance of different implant diameters and implant neck designs of a Ti-6Al-4V ELI implant system with a one-size implant- abutment (OSIA) connection.

Narrow (N, 3.4mm), regular (R, 4.0mm) and wide diameter (W, 4.6mm) implants of an OSIA system (Axiom®, Anthogyr) were tested with stock abutments. Two implant neck designs (RG, PX) were tested. The implants, abutments and screws were all made of Ti-6Al-4V ELI. This resulted in six test groups: N/RG, R/RG, W/RG, N/PX, R/PX and W/PX. Five specimens were made for each group (n = 5). A rotational load fatigue machine applied a sinusoidally varying load at an angle of 45°, producing an effective bending moment of 35Ncm at a frequency of 10Hz in air at 20°C. The number of cycles to failure was recorded, and the results were evaluated using two-way ANOVA. Failed specimens were examined with a scanning electron microscope (SEM) to evaluate the mode of failure. Pristine specimens were sectioned to examine the implant-abutment connection.

All 30 specimens in the six test groups failed with mean cycle counts that ranged from 523,674 to 1,282,373. No implant fractures were noted regardless of implant diameter or neck design. The mode of failure was abutment fracture at the level of the implant platform, with accompanying screw fracture for all specimens. There was no significant difference in the number of cycles to failure across implant diameters (P = .272) and neck designs (P = .861).

For Ti-6Al-4V ELI implants with an OSIA connection, there was no significant difference in the number of cycles to failure across implant diameters and neck designs. The mode of failure observed was abutment fracture with accompanying screw fracture. This failure pattern may be unfavourable and present challenges for retrieval and subsequent replacement of a failed prosthesis.