UNIVERSAL HUMAN
TEETH & TONGUE TEXTURES DOCUMENTATION
Ensure you've downloaded the most recent versions of the assets
Select the Teeth Upper object and open the Shader Editor
Set the Albedo Mix and Displacement values to 1.0
Load the Teeth Upper Albedo image into the Image Texture node that's connected to the Albedo Image input socket on the Teeth Upper node.
Load the Teeth Upper Displacement image into the Image Texture node that's connected to the Displacement Image socket, and set its Color Space to Non-Color (see image on right).
Repeat the above with the Teeth Lower and Tongue objects and nodes.
Be sure to set the appropriate Cycles Render Device in Edit > Preferences > System, and select GPU Compute (if available) in Render Properties to maximise rendering speed.
Rendering
For best results, make sure Displacement & Bump is selected in Material Properties > Settings > Surface > Displacement for each of the objects, and set the subdivision levels as high as your hardware permits (or until you can't notice any improvement). Keep a close eye on your memory usage while testing subdivision levels, as overdoing it can quickly exceed the available RAM and cause the system to hang.
Displacement detail may take a long time to resolve. When using denoising, make sure the Albedo and Normal passes are enabled.