 Astra Tech
BioManagement Complex
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 Atlantis
Atlantis'" is the patient-specific abutment for all major implant systems. The abutments are designed from the final tooth shape using unique software, enabling the production of milled titanium and zirconia abutments.
 A comparison of fabrication precision and mechanical reliability of 2 zirconia implant abutments
Purpose: Published studies indicate that zirconia is a reliable implant abutment material. Zirconia possesses several positive characteristics such as bio-compatibility, favourable color and mechanical properties, which makes the material suitable for use in modern dentistry. The purpose of the study was to compare fabrication precision and fracture strength of two types of commercially available zirconia abutments; the Atlantis™ Abutment Zirconia (Astra Tech) and the Procera AllZirkon abutment (Nobel Biocare).
Material and Methods: Twenty-nine abutments of each type (Atlantis and Procera AllZirkon) were created by their respective manufacturers to fit a Branemark System implant with external hex, diameter 4.0 mm (Nobel Biocare). Ten abutments of each type were randomly selected for precision measurements using a coordinate measuring machine with a smalldiameter touch probe (Brown and Sharpe, North Kingston, USA). The following dimensions of the abutment interface area were recorded in order to evaluate fabrication precision: hex dimensions (mean of three measurements of opposite hex walls), bore diameter concentricity, mean counterbore diameter, and mean true position of the counterbore to bore.
The remaining specimens were used to measure fracture strength, and to analyze fracture origin and propagation characteristics. Each test specimen (connected implant and abutment) was loaded in a standardized testing machine (Instron Corporation) in an angled manner, simulating maximum implant-abutment misalignment and off-axis loading. Increasing loads were applied until fracture of the specimens. Maximum failure load was recorded and the probability of failure was evaluated for the two abutment types. Next, the characteristics (location and nature of fracture origin) of the fractures were analyzed.
Results: The calculations performed on the fabrication precision of the abutment interface determined that there were no statistically significant difference between the two abutment designs. The mean load to fracture values were 831 ±69 N for the Atlantis abut-ments and 740±96 N for the Procera AllZirkon abutments. This difference was statistically significant. Furthermore, the load to failure data demonstrated a higher probability of failure for the Procera AllZirkon abutment compared to the Atlantis abutment under intraoral occlusal loads.
Scanning electron microscopy analyses of the fractures showed that fracture origins for both types of abutments were typically small irregularities in the asprocessed surface. However, the analyses revealed noticeable differences in the crack propagation between Procera AllZirkon and the Atlantis abutment, with the Atlantis abutments showing consistent fracture origin of the inner hex interface surface for all test abutments. The fractured surface appeared smooth and continuous throughout the fractured surface. The Procera AllZirkon, on the other hand, exhibited fracture origin at the radius inside the hex, and the fractured surface was visibly irregular.
Discussion and Conclusions: The authors conclude that both types of zirconia abutments showed failure loads exceeding maximum human bite force, however, mean load to failure was significantly higher for the Atlantis abutment compared to the Procera AllZirkon abutment. In addition, the Atlantis abutment showed a statistically significant higher probability to survive occlusal loads. There were no significant differences between the interface features measurements for the two abutments types. The difference in strength would therefore most probably not be related to the precision of the respective fabrication process, but rather a result of the raw stock material that each company uses in its abutment fabrication process. |
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