Kieffer Moore had put the hosts two goals to the good shortly after half-time, leaving Spurs staring at a third successive Premier League defeat, but second-half-goals by Ryan Sessegnon, Ben Davies and Bentancur kept them in third place.
With one eye on next week's vital Champions League clash away in Marseille, Tottenham manager Antonio Conte made several changes to his side and Bournemouth took full advantage.
Moore finished off a flowing move in the 22nd minute when he curled a low shot past Hugo Lloris after a ball in from the right wing by Marcus Tavernier.
Moore then added a second shortly after halftime with a header from Adam Smith's cross.
Sessegnon was about to be substituted when he popped up to fire home left-footed in the 57th minute and then Davies powered a header in from a corner in the 73rd minute.
Tottenham piled on the pressure and were rewarded in stoppage time when Bentancur, on as a substitute, fired in after a corner was not cleared by the Bournemouth defence.
Tottenham stayed in third place with 26 points from 13 games with Bournemouth on 13 points.
Additional reporting by Reuters.