Poor marginal fit is one of the most frequent complaints related to digitally fabricated restorations. The root cause may lie in clinical scanning, data processing, or laboratory design and manufacturing. A systematic approach is required to identify and correct the problem.
Clinical Causes (Approximately 70% of Cases)
Insufficient finish-line exposure
Gingival coverage and inadequate retraction are the most common reasons. When equigingival or subgingival margins are not properly retracted, the finish line is obscured and the technician is forced to estimate its position.
Blood or saliva contamination
Blood causes reflections and saliva causes refraction, both of which can blur or distort the margin data.
Retraction cord left in place
Cord that is not removed or that covers the shoulder hides the true finish line in the scan.
Tooth preparation issues
Sharp overhangs/flashes are rounded during scanning → restoration margin becomes too long.
Indistinct shoulder definition due to incorrect bur selection.
Unpolished surfaces reduce scanning accuracy.
Undercuts prevent proper seating of the restoration.
Adjacent tooth interference
Proximal surfaces of neighboring teeth can create steps that obscure the preparation margin.
Incorrect scanning angle
Failure to capture the finish line from a sufficiently perpendicular direction produces shadows and incomplete data.
Inaccurate bite registration
Incorrect occlusion leads to restorations that are too high or too low.
Data-Processing Causes
Unfilled voids that the software automatically interpolates incorrectly.
Stitching discontinuities that shift the margin position.
Soft-tissue deformation caused by pressure from the scanner tip; after the tip is removed the gingiva rebounds but the recorded data remains distorted.
Incorrect automatic AI margin detection that is not manually verified and corrected.
Laboratory Causes
Incorrect manual or automatic margin-line drawing by the technician.
Inappropriate cement-gap / marginal-gap settings during design.
Milling or 3D-printing inaccuracies.
Insufficient compensation for material shrinkage.
Systematic Troubleshooting Process
First examine the original scan data: rotate the model carefully and check whether the finish line is clear and free of deformation.
Verify that the margin line drawn in the software accurately follows the true finish line.
Compare the digital model with the actual clinical situation in the mouth.
If the clinical data appear correct, discuss design parameters and manufacturing steps with the laboratory.
When necessary, re-scan the preparation or re-prepare the tooth.
How the Right Scanner Reduces Marginal-Fit Problems
Many clinical and data-related issues can be minimized with a scanner that delivers high accuracy, good depth of field, and clear real-time feedback. The Aident AI-30 Intraoral Scanner helps clinicians capture cleaner finish lines with:
≤10 μm accuracy for precise margin definition
20–25 mm ultra-deep depth of field that improves capture of slightly subgingival areas
Intelligent anti-fog heating and powder-free true-color imaging for better visibility in moist conditions
Lightweight design (156–198 g) that enhances control during multi-angle margin scanning
Fully open STL/PLY/OBJ output that supports accurate communication with any laboratory
These features contribute to higher first-fit rates and fewer remakes for crowns, bridges, and other fixed restorations.
Achieve Better Marginal Fit Consistently
Most cases of poor marginal adaptation originate from incomplete finish-line exposure or data quality issues at the clinical stage. Combining disciplined preparation, proper retraction, correct scanning technique, and a reliable intraoral scanner significantly reduces these problems.
Explore the Aident AI-30 and complete digital dentistry solutions:
https://www.aident3d.com/3d-scanner/intraoral-scanner/
Request a free demonstration, technical brochure, or personalized quote:
https://www.aident3d.com/contact-us
Accurate marginal fit starts with clear clinical data and the right technology - choose a scanner that helps you deliver precise restorations every time.
