The Spell Disintegrate states that
A disintegrated creature and everything it is wearing and carrying, except Magic Items, are reduced to a pile of fine gray dust. The creature can be restored to life only by means of a True Resurrection or a wish spell.
And a Demon does this when it dies:
…the fiend dissolves into foul ichor. It then instantly reforms in the Abyss, its mind and essence intact.
How do these two effects interact? Does being "reduced to a pile of fine gray dust" effectively destroy the Demon for good? Or is it still a Demon and not a pile of fine gray dust and still capable of reforming in the Abyss?