Autodesk Meshmixer - a free program for 3D printing to view, edit, analyze and repair STL files.
MeshLab - Open source software for processing and editing of unstructured 3D triangular meshes. It also has an extremely fast slide function.
Models exported from dental 3D scanning software often need extra manipulation in order to become printable. The following youtube playlist explains how to fix your dental model using MeshMixer.
Below is a list of some helpful videos from the playlist:
