Rotational Load Fatigue Performance of Implants with Cylindrical and Conical Internal Cam-Groove Connections

Implant-abutment complexes from the same brand have evolved with time, retaining similar design features while improving on other aspects. This study investigated the rotational load fatigue performance of narrow, regular, and wide diameter implants with cylindrical and conical internal cam-groove configurations.

Narrow (3.3mm), regular (4.3mm), wide (5.0mm) diameter cylindrical internal cam-groove implants (CAM); and narrow (3.3mm), regular (4.3mm), wide (5.0mm) diameter conical internal cam-groove implants (CNL) were tested with their corresponding universal abutments. The 6 test groups: CAM33, CAM43, CAM50, CNL33, CNL43, CNL50; had five specimens in each group (n=5). A rotational load fatigue machine subjected the implant-abutment test assemblies to sinusoidally varying loads at an angle of 45°, producing an effective bending moment of 35Ncm, at a frequency of 12 Hz, at room temperature of 20°C. The number of cycles to failure was recorded, with the upper limit set at 5 x 106 cycles. Results were evaluated using ANOVA and failed samples were analyzed under SEM to investigate fracture patterns indicative of the mode of failure.

5 out of 30 samples, all from the CAM33 group failed. The locations of failure varied across the length of the abutments but the site of fractures on the implants were generally located below the anti-rotational features of the implants. Damage to the abutment, abutment screw and implants were seen in four samples, while one sample had abutment and implant fracture only. All regular and wide diameter implants, and the narrow diameter Conelog implants reached the upper limit without failure. The rotational load fatigue performance of CAM33 was significantly poorer than all the other five tests groups (P = <.001).

CAM33 performed significantly poorer than the other diameters and internal connection. Failures seen in the CAM33 group occurred below the simulated bone level, and these will present a significant clinical challenge to retrieve and replace should any components fail in service.