Purpose: One-size implant-abutment (OSIA) connection systems have been developed for

simplicity of clinical use and for a range of implant diameters. The aim of this in vitro study was

to investigate the rotational load fatigue performance of different implant diameters and

abutment platforms of an OSIA connection system. Methodology: Narrow, regular and wide

diameter implants were tested with Regular Base (RB/WB) abutments of an OSIA system

(Straumann. BLX). Wide diameter implants were also tested with Wide Base (WB) abutments.

This resulted in 4 test groups (n=5): N-RB/WB (Narrow, 3.5mm, RB/WB abutment), R-RB/WB

(Regular, 4.0mm, RB/WB abutment), W-RB/WB (Wide, 5.0mm, RB/WB abutment) and W-WB

(Wide, 5.0mm, WB abutment). A rotational load fatigue machine applied a sinusoidally varying

stress at an angle of 45o, producing an effective bending moment of 35Ncm at a frequency of 10

Hz in air at 20 oC. The number of cycles to failure was recorded. Results were evaluated using

ANOVA. Failed specimens were examined with SEM to evaluate the failure mode. Pristine

specimens were sectioned to examine the implant-abutment connection. Results: All specimens

in the 3 test groups with RB/WB abutments failed within the range of 558,750 cycles to

4,497,619 cycles, while the W-WB test group reached the upper limit of 5 million cycles without

failure. Significant difference was found between abutment platforms (P < .001). There were no

significant differences found for implant diameters (P =.857). However, with increasing implant

diameter, implant fracture was less common and the location of failure was more coronal and

consistently at the level of the implant platform for the abutment, and at the screw neck.

Conclusions: For wide diameter implants, WB abutments exhibited a superior fatigue

performance than RB/WB abutments, and would be preferred in situations of high mechanical

risk. Increasing implant diameter, when used with RB/WB abutments, did not improve fatigue

performance due to the one-size prosthetic connection, but failures were less catastrophic, and

coronally located, which may be advantageous in managing failures.