If you are adjusting margins or occlusion before exporting, ensure you are adjusting the "facial," "lower boundary," and "morph points" in the control panel to ensure the final STL is accurate.
If you do not have access to the original dental CAD software, specialized conversion tools may work: Sdfa File To Stl
Tools like Spin 3D Mesh Converter by NCH Software are reported to handle various mesh conversions, including some SDF/SDFA variations. Why Convert SDFA to STL? If you are adjusting margins or occlusion before
Try using (free for hobbyists) or Blender : ensure you are adjusting the "facial