Hello,
Thanks for your question!
If you're using 3ds Max 2021, please note that the Arnold default render engine (which also displays the material sample swatches in either the Compact or Slate Material Editor) does not natively support all 3ds Max legacy maps.
However, if you go to the Rendering > Render Setup > Arnold > Systems tab, and check the "Legacy 3ds Max Map Support" button, you should then be able to pick the Dent map type from the Material Editor and render it with Arnold.
Can you please try this and let us know if this works for you? Thanks!
Jon A. Bell
Senior Technical Support Specialist, 3ds Max