How to Repair STL Files: https://formlabs.com/blog/best-stl-file-repair-software-tools/
How to convert a CT scan to an stl file: https://makezine.com/projects/3d-print-your-medical-scan/
Models exported from dental 3D scanning software often need extra manipulation in order to become printable. The following videos explain how to fix your model using MeshMixer, which can be downloaded for FREE here: http://www.meshmixer.
Clean up the scan: https://www.youtube.com/
Trim the model: https://www.youtube.
Adding a base: https://www.youtube.com/
Hollow the model: https://www.youtube.
How to export the model: https://www.youtube.
How to reduce the size of your file: https://www.youtube.com/watch?v=tpYTo70p4cI