A full-arch restoration can look perfect on the screen and still rock or fail to seat after milling.
One common cause is a mismatch between the implant interfaces and the restoration’s path of insertion. PMMA and printed try-ins may flex enough to hide this discrepancy, but rigid materials such as zirconia and titanium cannot.
The free Passive Fit Check App in the Alien Milling Arcade helps identify these concerns before you submit the case for production.
Upload your full-arch STL, mark the interfaces, and let the app calculate the best shared path of insertion. In 2 seconds, you will receive a clear pass-or-fail result and a detailed PDF report for the case.
Why Interface Parallelism Matters
For a rigid, screw-retained full-arch restoration to seat properly, every interface must be compatible with the restoration’s path of insertion.
If one or more Multi-Unit Abutments are positioned outside the acceptable range, the restoration may bind at those interfaces. This can result in:
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Rocking during seating
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Incomplete seating
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Excessive pressure at an interface
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Screw-access complications
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Delivery delays
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Additional scans, redesigns, or remakes
The Passive Fit Check App analyzes the relationship between the selected interfaces so potential insertion-path concerns can be addressed before the final restoration is manufactured.
How to Use Passive Fit Check
The process is fast, visual, and designed to fit directly into your existing full-arch workflow.
Step 1: Upload Your Full-Arch Design
Open the Passive Fit Check App in the Alien Milling Arcade and drop your completed full-arch STL design into the upload area.
The restoration will appear in the interactive 3D viewer, where you can rotate, zoom, and inspect the design before beginning the analysis.
Step 2: Mark the First Interface
Begin by clicking the inverted cone wall inside the first implant interface.
Be sure to select the actual interface wall—not the screw channel, surrounding tissue surface, or another part of the restoration.
Once selected, the interface will be identified within the viewer.
Step 3: Continue Marking Every Interface
Continue selecting the inverted cone wall of every remaining interface.
Each marked interface will appear in a unique color, making it easy to confirm that all implant positions have been included in the analysis.
Carefully rotate the restoration as needed and verify that every interface has been selected before continuing.
Step 4: Calculate the Best Path of Insertion
After marking all interfaces, click Compute Best Axis.
The app will automatically calculate the most favorable shared path of insertion based on the selected interfaces.
If you already have a specific insertion path you want to evaluate, you may also set the path of insertion manually.
Step 5: Review the Pass-or-Fail Result
Once the calculation is complete, a result window will appear showing whether the case passed or failed the analysis.
A pass indicates that the selected interfaces are within the app’s acceptable angulation range for the calculated path of insertion. This provides greater confidence that the rigid restoration can seat without an interface-related path-of-insertion conflict.
A fail indicates that one or more interfaces may interfere with passive seating.
If the case fails, the report can help identify which MUA positions require attention. In some cases, replacing a straight MUA with a 17-degree or 30-degree angled MUA may improve the shared insertion path.
After changing the MUAs, the case should be rescanned, redesigned, and checked again before production.
Download the Detailed PDF Report
After completing the analysis, download the PDF report for a detailed record of the results.
The report includes:
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The original STL filename
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An image of the full-arch design
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Each selected implant interface
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A unique color identifying each interface
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The measured degree of angulation for every interface
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An individual pass-or-fail result for each position
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The overall result for the case
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Recommendations for interfaces requiring attention
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Suggested MUA corrections when applicable
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Guidance indicating whether a 17-degree or 30-degree angled MUA may be appropriate
The PDF can be saved with the case files, reviewed by the designer, or shared with the clinician before proceeding.
Use Passive Fit Check with Scan Bodies
You do not need to wait until the full-arch restoration has been designed.
Passive Fit Check can also analyze scan bodies before the design process begins. This allows you to evaluate the interface relationship earlier in the workflow and identify potential angulation concerns before spending time designing the restoration.
Upload the STL containing the scan bodies, then select the same flat top portion of every scan body. After all scan bodies are marked, calculate the best axis and review the results.
Checking the scan bodies before design may help determine whether the existing MUA configuration provides a compatible path of insertion or whether an angled MUA should be considered first.
A Smarter Full-Arch Workflow
For greater predictability, use Passive Fit Check at multiple stages of the case:
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Check the scan bodies before beginning the design.
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Address any MUA angulation concerns identified by the report.
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Complete the full-arch design.
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Upload the final STL and run Passive Fit Check again.
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Review and save the PDF report.
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Submit the approved design for an Alien Full-Arch Zirconia Try-In.
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Clinically verify fit, occlusion, and phonetics before ordering the definitive restoration.
This workflow combines digital interface analysis with a physical evaluation in rigid zirconia, helping identify potential problems while they can still be corrected.
Designed to Prevent Expensive Surprises
A flexible PMMA or printed try-in may seat even when a rigid zirconia restoration cannot. Passive Fit Check gives your team an opportunity to identify interface angulation and insertion-path concerns before milling.
It takes only a few seconds, generates a detailed case report, and is available free in the Alien Milling Arcade.
Check the scan bodies. Check the design. Verify the path. Then go final with confidence.
Open the Passive Fit Check App
Passive Fit Check is a workflow-assistance tool. Its results should be reviewed together with the accuracy of the scan data, restoration design, components, models, and clinical conditions.
This report is a geometric screening aid, not a clinical determination. Verify fit with a verification jig before final prosthesis fabrication.