Unifying intraoral scanner, computer-aided manufacturing, and final crown accuracy: A virtual-fit method for marginal...

Area of Science:

• Dental technology
• Biomaterials science
• Digital dentistry

Background:

• Accurate marginal gap (MG) measurement is crucial for CAD/CAM crown fabrication.
• Evaluating error accumulation from intraoral scanning (IOS) and computer-aided manufacturing (CAM) is complex.

Purpose of the Study:

• To validate a high-resolution virtual-fit method for MG assessment across CAD/CAM stages.
• To determine if the Root Sum of Squares (RSS) method can reliably estimate total error from IOS and CAM.

Main Methods:

• A typodont model was scanned using IOS, and CAD designs with varying cement space settings were created.
• Hybrid-ceramic crowns were milled and scanned using lab and industrial scanners.
• A virtual-fit method assessed MG at IOS, CAM, and combined (IOS+CAM) stages.
• The RSS formula estimated total error, with sensitivity analysis performed.

Main Results:

• The virtual-fit method showed high statistical power, detecting differences as small as 6 µm.
• The RSS estimate slightly overestimated final MG at 70 µm spacing.
• No significant difference in MG was observed at 100 µm and 140 µm spacing between scanners.
• Final MG was higher at 140 µm than 100 µm spacing (p < 0.05).

Conclusions:

• The virtual-fit method offers consistent, high-resolution MG measurement throughout the CAD/CAM workflow.
• RSS modeling effectively supports cumulative error assessment for IOS and CAM systems.
• Cement spacing of 70-100 µm is recommended for accurate chairside CAD/CAM crown fabrication.