Ralf Kohal1,*; Kirstin Vach2; Julian Nold1; Christopher von Schierholz1

1Department of Prosthetic Dentistry, Medical Center - University of Freiburg, Center for Dental Medicine, Faculty of Medicine, University of Freiburg; 2Faculty of Medicine and Medical Center - University of Freiburg, Institute of Medical Biometry and Statistics, Freiburg, Germany

Background: Biomechanical stability data on two-piece zirconia oral implants restored with zirconia restorations are rarely reported.

Aim/Hypothesis: The objective of this investigation was, therefore, to evaluate the long-term stability of a two-piece zirconia implant restored with a zirconia abutment.

Material and Methods: Thirty-two implants (Ø 4.0 mm; Ceralog, Altatec, Wimsheim, Germany) were embedded according to ISO 14801 and restored with zirconia abutments (DEDICAM, Camlog) (lever arm for all implants: 5.59 ± 0.03 mm). Three subgroups (n = 8) were exposed either to dynamic loading alone (group DL, 107 chewing cycles; load 98 N), to hydrothermal treatment alone (group HT, aging in 85 0C hot water, 107 cycles, no load) or to a combination of both (group DL/HT) in a chewing simulator. One subgroup (group 0) served as untreated control group. One sample of each subgroup was evaluated for phase-transformation (not part of this abstract). The remaining samples were loaded until fracture in a universal testing machine. A one-way ANOVA was used to analyze loading/bending moment differences between treatment groups. The Student-Newman-Keuls method was applied to correct for multiple testing. A t-test was used for within-group comparisons. The probability level for statistical significance was set to p < 0.05.

Results: Three out of seven samples in the DL group and six out of seven samples in the DL/HT group fractured during artificial loading. The load to failure attributed to these implants was 98 N. The mean fracture strength for the DL group was 471 N (±354 N) and 193 N (±251 N) for the DL/HT group (Table 1). The stability test in the universal testing machine of groups 0 and HT lead either to implant or to abutment fractures. In group 0, four crowns fractured at the abutment level at a mean load of 564 N. The implants of these four samples, hence, showed no damage on a macro- and microscopic level. In the same group, three implants fractured at a mean of 673 N (implant/abutment values together: 611 N). In group HT, three abutments fractured at a mean load of 625 N, and four of the implants at 666 N (implant/abutment values together: 648 N) (Table 1).

Conclusion and Clinical implications: The fracture stability/bending moments of the not loaded implants (0 and HT) were comparable to other two-piece implants. The number of fractured implants in the artificial chewing simulator, however, was high in comparison to other studies. Within the limits of this investigation, it can be concluded that loading reduces the stability of the investigated two-piece zirconia implant and therefore its reliability.

The implants and abutments were kindly provided by CAMLOG Biotechnologies, GmbH.

Disclosure of Interest: None Declared

Keywords: biomechanical stability, implant stability, zirconia