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.
Mold the borders: Complete border molding 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.
Finalize 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.