CT of Impression Merged Based on Markers using the "Import Scan Appliance" functionality

Here is a video that is based on a technique suggested by Dr Rick Ferguson.
For high scatter cases, the impression, with markers can be imported using the "Import Scan Appliance" functionality. Since the markers for the impression, and the markers for the CT are each displayed in their own windows, with their own density threshold the merge can be done accurately even if the markers are covered by impression material.
The impression is merged using the markers, and then inverted using the inversion functionality in the "Model Manipulation" panel

[@arch0051]

This may be a dumb question but is there an impression material which you recommend which shows up best in a CT?