What material should never be used on dentin or certain restorations during dental polishing?

The correct answer highlights that coarse pumice should never be used on dentin or certain restorations during dental polishing due to its abrasive nature. Dentin is a softer tissue compared to enamel, and using a coarse abrasive can lead to excessive material removal, damage the underlying structure, and potentially expose the pulp, leading to sensitivity or other complications.

Certain restorations, especially those made with composite materials or glass ionomers, are more susceptible to damage from rougher abrasives. Coarse pumice can scratch or alter the finish of these materials, compromising their integrity and aesthetics. Therefore, it is essential to select polishing materials that are appropriate for the surface being treated, and finer abrasives should be favored to preserve the health of dentin and the quality of restorations.

Finer pumice, medium grit abrasives, or super fine pumice are much more suitable options for polishing teeth and restorations, as they provide a smoother finish without the risk of damaging softer substances.