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.
Marginal integrity of direct and indirect castings of implant abutments
Purpose: The purpose of this study was to measure and compare the marginal gap size (accuracy) of metal copings fabricated on direct i.e. computermilled abutments (CMA), or with indirect technique i.e. on epoxy and stone dies. This in order to evaluate if the Atlantis technique has clinical advantages such as reducing the steps (positive-to-negative transformations) in implant laboratory restorative procedures.
Materials and methods: Ten computermilled abutments were used in the experiment. They were milled from a block of commercially pure titanium into a standardized premolar shape (mesialdistal width of 7 mm, buccolingual width of 8 mm, 10" occlusal convergence, 11 mm high and the apical 3 mm serving as the collar). 5 Atlantis abutments were placed on each side on implant analogs positioned in a jaw model only having the incisors left for orientation.
After impression with vinyl polysiloxane material two full arch working casts were produced.
The casts which had removable dies, were made of epoxy resin and type IV die stone. Marginals were exposed after careful trimming. Casts in type III alloy were then made for all three modeling techniques, a) directly on the titanium computer-milled abutments coated with 2 layers of die spacer prior to wax up and casting; b) indirect wax ups on the epoxy resin dies coated with 3 layers of die spacer; c) indirect wax ups on the stone dies coated with 2 layers of spacer and casting. The castings were cleaned and fitted to respectively epoxy or stone dies, or if computermilled fitted to the abutment prior to analysis. At imaging in the microscope (60X Olympus SZX12 equipped with a USB camera) a custom built holder was used fixating the abutment and castings (a finger pressure level) to ensure complete seating. The images were analyzed with a specialized imaging and measurement software program (Bioquant 2000, Biometrics) at five uniform sites along the marginal interface. A mean marginal gap value was calculated for each casting, and was compared using a 1-way analysis of variance and pairwise comparison (Scheffe test). Additionally, casts made from epoxy and stone dies were photographed and measured as controls.
Result: A comparison of the marginal gap of metal copings between indirectly made dies (on epoxy and stone) and those made directly on duplicate abut-ments was performed. Further, in order to reveal the quality of the CMA, the gap at copings seated on the abutment from which they were waxed were compared with the gap after transfer to a duplicate abutment. The castings made from direct technique had the smallest mean marginal gap (P <0.001). The gap was not significantly changed when these casts were transferred to the duplicate abutment. The result for the direct technique was clinically acceptable. Using the indirect technique resulted in larger gap sizes irrespective of die material (epoxy or stone). The marginal gap of indirect castings were also larger on casts from epoxy dies compared to stone dies.
Discussion: The uncertainty of the impression steps and provisional abutment can be avoided with an even higher accuracy of the final cast when using the Atlantis technique. The result from this study show that computermilled abutments can be duplicated with sufficient accuracy and allow an exchange of casting between the original abutment and the duplicate abutment. In the clinic this result in shortened treatment time, increased fit and reduced number of laboratory remakes.
Astra Tech
BioManagement Complex 
