Mechanical testing of thin-walled zirconia abutments

Although the use of zirconia abutments for implant-supported restorations has gainedmomentum with the increasing demand for esthetics, little informed design rationalehas been developed to characterize their fatigue behavior under different clinicalscenarios. However, to prevent the zirconia from fracturing, the use of a titaniumconnection in bicomponent aesthetic abutments has been suggested.

Objective:

Mechanical testing of customized thin-walled titanium-zirconia abutments at theconnection with the implant was performed in order to characterize the fatiguebehavior and the failure modes for straight and angled abutments.

Material and Methods:

Twenty custom-made bi-component abutments were tested according to ISO 14801:2007either at a straight or a 25º angle inclination (n=10 each group). Fatigue wasconducted at 15 Hz for 5 million cycles in dry conditions at 20ºC±5ºC. Mean valuesand standard deviations were calculated for each group. All comparisons wereperformed by t-tests assuming unequal variances. The level of statisticalsignificance was set at p≤0.05. Failed samples were inspected in apolarized-light and then in a scanning electron microscope.

Results:

Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, thedynamic loading mean F^max was 237.4 N and 240.7 N, respectively. Nosignificant differences resulted between the straight and angled bi-componentabutments in both static (p=0.253) and dynamic testing (p=0.135). A significantdifference in the bending moment required for fracture was detected between thegroups (p=0.01). Fractures in the angled group occurred mainly at the point ofload application, whereas in the straight abutments, fractures were locatedcoronally and close to the thinly designed areas at the cervical region.

Conclusion:

Angled or straight thin-walled zirconia abutments presented similarF^max under fatigue testing despite the different bending momentsrequired for fracture. The main implication is that although zirconia angled orstraight abutments presented similar mechanical behavior, the failure mode tendedto be more catastrophic in straight (fracture at the cervical region) compared toangled abutments.