This guide explains how to establish a repeatable scan path for complete denture cases to ensure a precise appliance fit, and provides steps to resolve common scan errors and how to take an accurate wash impression.
Capture a Wash Impression
Follow these instructions to prepare the existing denture for 360-degree scanning.
Prepare the Denture or Wax Rim
Clean the denture or rim: Thoroughly clean the existing denture or rim to remove all debris or residue.
Apply adhesive (Optional): Apply a small amount of tray adhesive to the denture base to help the impression material adhere to the surface.
Apply Impression Material
Dispense material: Dispense medium or light body impression material onto the surface of the denture base, starting at the posterior region and working forward.
Smooth and extend: Use a dental spatula to smooth the material and extend it to the borders of the denture.
Verify coverage: Ensure the entire surface of the denture base is covered with impression material.
Perform the Wash Impression
Seat the denture: Have the patient bite down into the impression material. Ensure the material is evenly distributed and covers all areas.
Mould the borders: Complete border moulding movements with the patient. This allows the designer to assess if the denture border needs extension.
Set the material: Allow the impression material to set according to the manufacturer's instructions.
Finalise the Impression
Remove and inspect: Remove the denture from the patient's mouth once the material is set. Inspect the impression for bubbles or defects.
Trim excess: Trim any excess wash material that overlaps onto the anatomical landmarks of the denture.
Dry the surface: Thoroughly dry the impression using a clean towel or compressed air.
[!NOTE]
If wash impression material is unavailable, a soft liner may be used as the anatomical reference.
If fit is good, wash impression is unnecessary.
Lower Denture or Wax Rim Extraoral Scanning Steps
To capture a high-quality lower scan, follow the sequence: Intaglio → Borders → Occlusal → Cameo.
Intaglio Surface: Begin scanning on the intaglio (inner) surface of the lower appliance.
Peripheral Borders: Use a "rocking and rolling" motion to move the scanner from the intaglio toward the border, then roll back toward the intaglio. Repeat until the entire border is captured.
Cameo Surface: Rock the scanner from the buccal border toward the buccal/facial surface, then roll back toward the border.
Occlusal Surface: Rock the scanner from the buccal surface to the occlusal and lingual surfaces, then roll back toward the occlusal until all surfaces are scanned.
Data Evaluation: Check the digital model for missing data and rescan the lower appliance if gaps are found.
Upper Denture or Wax Rim Extraoral Scanning Steps
To capture a high-quality upper scan, follow the sequence: Intaglio → Borders → Occlusal → Cameo.
Intaglio and Palate: Begin on the intaglio surface. Slowly sweep the scanner from side to side to capture the majority of the palate.
Peripheral Borders: Use a "rocking and rolling" motion to move the scanner from the intaglio over the border and back. Repeat until the entire border is scanned.
Cameo Surface: Rock the scanner from the buccal border toward the facial surface and back until all buccal surfaces are captured.
Occlusal Surface: Rock the scanner from the buccal surface to the occlusal and lingual surfaces, then roll back to the occlusal.
Data Evaluation: Check the digital model for holes and rescan the upper appliance as needed.
Capture the Bite Registration
Place the upper and lower prostheses in the patient's mouth and confirm correct occlusion.
Apply blue bite registration material to stabilise the bite and prevent movement.
Scan the first intraoral bite from the molar area to the midline.
Scan the second intraoral bite from the molar area to the midline on the opposite side.
Identify High-Quality Scan Characteristics
Change the scan colour to stone on the review page to verify the following characteristics:
Complete Data: No missing information on the occlusal or intaglio surfaces.
Solid Connection: No unconnected data or visible gapping.
Anatomy Focus: A consistent impression that only captures intraoral anatomy without lifted edges.
Alignment: An accurate and stable bite alignment.
Troubleshoot Common Scan Errors
Use these steps to resolve specific scan quality issues:
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Missing Scan Data: Start the scanner on an area it easily recognises, then move slowly toward the gap.
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Stitching Errors: