In vitro performance of one- and two-piece zirconia implant systems for anterior application.

OBJECTIVES: To investigate the long-term in vitro performance and fracture resistance of one-piece and bonded two-piece zirconia implant systems for anterior application.

METHODS: Two groups of bonded two-piece zirconia (ZZB), four groups of one-piece zirconia (Z), and two groups of two-piece titanium (TTS, reference) implant systems were restored with identical monolithic zirconia crowns (n=10/group). Eight specimens per group were mounted at an angle of 135° in the chewing simulator and subjected to thermal cycling (TC:18,000 cycles; 5°/55°) and mechanical loading (ML:3.6×10(6) cycles; 100N) simulating an anterior situation. Fracture resistance and maximum bending stress were determined for specimens that survived aging and for two references per group after 24h water storage. SEM pictures were used for failure analysis. Data were statistically analysed (one-way-ANOVA, post-hoc Bonferroni, Kaplan-Meier-Log-Rank, α=0.05).

RESULTS: A one-piece zirconia and a two-piece titanium implant system survived TCML without failures. Both bonded two-piece zirconia implant systems and a one-piece zirconia implant system totally failed (fractures of abutment or implant). Failure numbers of the other systems varied between 1× (1 group) and 5× (2 groups). Significantly different survival rates were found (Log-Rank-test: p=0.000). Maximum fracture forces/bending stresses varied significantly (

ANOVA: p=0.000) between 188.00±44.80N/381.02±80.15N/mm(2) and 508.67±107.00N/751.45±36.73N/mm(2). Mean fracture values after 24h water storage and TCML were not significantly different.

CONCLUSION: Zirconia implant systems partly showed material defects or connection insufficiencies. Bonded two-piece systems had higher failure rates and lower fracture resistance than one-piece implants.

CLINICAL SIGNIFICANCE: Individual zirconia implant systems may be applied in anterior regions with limitations.