Creatures within 5 feet of you provoke opportunity attacks from you even if they take the Disengage action before leaving your reach.
Does this mean any creature at any time leaving your reach provokes an opportunity attack (including if they take Disengage?) If so, then abilities like the following would still trigger an Opportunity Attack:
- Swashbuckler Rogue's Fancy Footwork (SCAG, 135)
During your turn , if you make a melee attack against a creature, that creature can't make opportunity attacks against you for the rest of your turn.
- Mobile Feat (PHB, Chapter 5)
When you make a melee attack against a creature, you don't provoke opportunity attacks from that creature for the rest of the turn, whether you hit or not.
There may be others, but the crux of the question is if Sentinel guarantees an OA.