In Season 8, Sam and Dean try to complete three trials to close the gates of Hell. The third trial is to cure a demon, but Dean calls it off when he finds out Sam would die when he completes it.
In seasons 9 and 10,
Dean becomes a demon, and then Sam cures him.
Why didn't this complete the third trial? The storyline was resolved pretty quickly (just a few episodes), so I'm wondering if it is in fact resolved, or if Dean might not be completely healed.
Is there anything to suggest that Dean isn't cured? If not, why wouldn't this complete the third trial?