Volume 11, Issue 4 p. 323-329

Stability of Prototype Two-Piece Zirconia and Titanium Implants after Artificial Aging: An In Vitro Pilot Study

Ralf-Joachim Kohal DMD, PhD

Corresponding Author

Ralf-Joachim Kohal DMD, PhD

Associate professor, Department of Prosthodontics, Albert-Ludwigs-University, Hugstetter Strasse 55; 79106 Freiburg, Germany;

Prof. Dr. med. dent., Ralf-Joachim Kohal, Department of Prosthodontics, School of Dentistry, University Clinic Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany; e-mail-address: [email protected]Search for more papers by this author
Hans Christian Finke DMD

Hans Christian Finke DMD

research assistant, Department of Prosthodontics, Albert-Ludwigs-University, Hugstetter Strasse 55, 79106 Freiburg, Germany;

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Gerold Klaus DMD

Gerold Klaus DMD

private practice, An der Sonnhalde 11, 79336 Herbolzheim, Germany

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First published: 06 November 2009
Citations: 48

ABSTRACT

Background: Zirconia oral implants are a new topic in implant dentistry. So far, no data are available on the biomechanical behavior of two-piece zirconia implants. Therefore, the purpose of this pilot investigation was to test in vitro the fracture strength of two-piece cylindrical zirconia implants after aging in a chewing simulator.

Materials and Methods: This laboratory in vitro investigation comprised three different treatment groups. Each group consisted of 16 specimens. In group 1, two-piece zirconia implants were restored with zirconia crowns (zirconia copings veneered with Triceram®; Esprident, Ispringen, Germany), and in group 2 zirconia implants received Empress® 2 single crowns (Ivoclar Vivadent AG, Schaan, Liechtenstein). The implants, including the abutments, in the two zirconia groups were identical. In group 3, similar titanium implants were reconstructed with porcelain-fused-to-metal crowns. Eight samples of each group were submitted to artificial aging with a long-term load test in the artificial mouth (chewing simulator). Subsequently, all not artificially aged samples and all artificially aged samples that survived the long-term loading of each group were submitted to a fracture strength test in a universal testing machine.

For the pairwise comparisons in the different test groups with or without artificial loading and between the different groups at a given artificial loading condition, the Wilcoxon rank-sum test for independent samples was used. The significance level was set at 5%.

Results: One sample of group 1 (veneer fracture), none of group 2, and six samples of group 3 (implant abutment screw fractures) failed while exposed to the artificial mouth. The values for the fracture strength after artificial loading with 1.2 million cycles for group 1 were between 45 and 377 N (mean: 275.7 N), in group 2 between 240 and 314 N (mean: 280.7 N), and in the titanium group between 45 and 582 N (mean: 165.7 N). The fracture strength results without artificial load for group 1 amounted to between 270 and 393 N (mean: 325.1 N), for group 2 between 235 and 321 N (mean: 281.8 N), and between 474 and 765 N (mean: 595.2 N) for the titanium group. The failure mode during the fracture testing in the zirconia implant groups was a fracture of the implant head and a bending/fracture of the abutment screw in the titanium group.

Conclusions: Within the limits of this pilot investigation, the biomechanical stability of all tested prototype implant groups seems to be – compared with the possibly exerted occlusal forces – borderline for clinical use. A high number of failures occurred already during the artificial loading in the titanium group at the abutment screw level. The zirconia implant groups showed irreparable implant head fractures at relatively low fracture loads. Therefore, the clinical use of the presented prototype implants has to be questioned.

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