After O’Driscoll finally called time on his a storied career, Ulster’s Darren Cave got the first shot at filling the number 13 jersey and stated his intentions with an early break, but the visitors had just two Sexton penalties to show for the bulk of the play.
Argentina, who chose to reserve their elite overseas-based players ahead of the upcoming Rugby Championship, looked more threatening in possession and cut the Irish defence into pieces on the half hour to pull in front.
Flyhalf Nicolas Sanchez, one of a handful of experienced starters, broke through the centre before finding the imposing Montero, who brushed Sexton aside with ease to superbly finish in the corner for his 12th try in 11 internationals.
Sanchez added the tricky conversion but Ireland, playing with an extra man after Benjamin Macome was sent to the sin bin, replied immediately to retake the lead as Henry emerged with the ball following a furious drive over the try line.
Ireland had a second try two minutes after the break. The impressive debutant Robbie Diack robbed a lineout, back row partner Jordi Murphy streamrollered his way through the middle and Sexton created some space before blasting his way over.
It was the Racing Metro flyhalf’s fifth try in his last three internationals and, after weathering some more pressure from the home side, Sexton finally got an easy conversion after wing Trimble intercepted on the halfway line to run clear.
Ireland, who were also without a number of the first choice players and for whom lock Iain Henderson impressed greatly, added a couple more penalties through replacement Ian Madigan before Tomas De la Vega got a late and deserved consolation try.
(Writing by Padraic Halpin in Dublin, editing by Mitch Phillips)