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

Objectives. To investigate the influence of the implant-abutment connection on the long-term in vitro performance and fracture resistance of two-piece zirconia implant systems for anterior application. Methods. Six groups of two-piece zirconia implant systems (n = 10/group) with screw-retained (5x) or bonded (1x) connections were restored with full-contour zirconia crowns. A two-piece screw-retained titanium system served as reference. For simulating anterior loading the specimens (n = 8/group) were mounted at an angle of 135 degrees in the chewing simulator, and subjected to thermal cycling (TC: 2 x 9000 x 5 degrees/55 degrees C) and mechanical loading (ML: 3.6 x 10(6) x 100 N). Failed restorations were examined (scanning electron microscopy). Fracture resistance and maximum bending stress of surviving restorations were determined. 2 specimens per group were loaded to fracture after 24h water storage without TCML. Data were statistically analyzed (ANOVA; Bonferroni; Kaplan-Meier-Log-Rank; alpha = 0.05). Results. The bonded zirconia system and the titanium reference survived TCML without any failures. Screw-retained zirconia systems showed fractures of abutments and/or implants, partly combined with screw fracture/loosening. Failure frequency (F) varied between the groups (F = 8 x : 3 groups, F= 3 x: 1 group, F =1 x : 1 group). The Log-Rank test showed significant (p = 0.000) differences. Fracture forces and maximum bending stresses (mean +/- standard deviation) differed significantly (ANOVA: p = 0.000) between 233.4 +/- 31.4 N/317.1 +/- 42.6 N/mm(2) and 404.3 +/- 15.1 N/549.2 +/- 20.5 N/mm(2). Fracture forces after TCML were similar to 24 h fracture forces. Significance. Screw-retained two-piece zirconia implant systems showed higher failure rates and lower fracture resistance than a screw-retained titanium system, and may be appropriate for clinical anterior requirements with limitations. Failures involved the abutment/implant region around the screw, indicating that the connecting design is crucial for clinical success. (C) 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved

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 (ITS, reference) implant systems were restored with identical monolithic zirconia crowns (n = 10/group). Eight specimens per group were mounted at an angle of 135 degrees in the chewing simulator and subjected to thermal cycling (TC:18,000 cycles; 5 degrees/55 degrees) and mechanical loading (ML:3.6 x 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 24 h water storage. SEM pictures were used for failure analysis. Data were statistically analysed (one-way-ANOVA, post-hoc Bonferroni, Kaplan-Meier-Log-Rank, alpha = 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 x (1 group) and 5 x (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 +/- 44.80 NI 381.02 +/- 80.15 N/mm(2) and 508.67 107.00 N/751.45 +/- 36.73 N/mm(2). Mean fracture values after 24 h 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. (C) 2016 Elsevier Ltd. All rights reserved