In version 2.0 of Medit i500, you have three choices when processing models at the very end of imaging. There are benefits to each method.
The first option is to not close any holes or remove unreliable data. The second choice is to just close hole, but not create a watertight model, and the third option is to close the holes and create a base / watertight models.
The third choice comes in handy for printing models, but it should be avoided for implant planning. As you can see in these examples, the merging of data sets can actually become more difficult with these extra data sets in the equation. Having no base in the model, makes the stitching much more reliable and automatic