A good fit and tooth structure is recommended. In this scenario, the partial fits the existing tooth extremely well.

• Remove the partial and scan the existing tooth as pre-preparation.

• Prep and scan the same area (be sure to include non-prepped dentition in both the pre-prep and prep scans for alignment).

• The pre-prep will be used as a guide for designing the new restoration with appropriate rest and guideplanes.

• If the preop tooth does not fit the partial well, create a temporary that fits the partial accurately. 
• Remove the partial and scan the temporary in place as an additional scan within the case or in a separate case.
• It is much more predictable to match a new crown design to a preop or additional scan than it is to try and fit the scan of a partial (see Scenario 3).

In this scenario, the partial does not fit the existing tooth well or the tooth is broken down.

• Scan the prep with the partial in place as pre-preparation.

• Remove the partial and take a master scan of the prep.

• Take a scan of the partial outside the mouth. Ensure that the partial is clean and dry. If there is a lot of reflective surface on the partial, use scan spray to reduce the reflectivity in order to get a more reliable scan. 
• If the aspects of the partial contacting the restoration are unclear, filled in by the scanner, or distorted, we will not be able to make a crown that fits the partial accurately.