Leinster back Jordan Larmour is the only uncapped player in a 36-man Ireland squad for the Six Nations games against France and Italy.
Larmour, 20, has impressed at full-back in try-scoring displays against Munster and Ulster in recent weeks and started his first European game on Sunday.
Garry Ringrose and Sean O'Brien are among those ruled out through injury.
Centres Chris Farrell and Bundee Aki, who won their first caps in the autumn series, are included in the squad.
Larmour was selected in preference to regular Ireland international Rob Kearney for the Champions Cup Pool 1 win over Glasgow at the weekend which sealed a home quarter-final for the Irish province.
The highly-rated former Leinster Academy player has scored six tries in 13 appearances this season.
Other players who were not considered for the opening two fixtures are long-term absentee Jamie Heaslip, Finlay Bealham, Rhys Ruddock, Tommy O'Donnell, Luke Marshall, Jared Payne and Niall Scannell, who is due to return to action in the coming weeks.
There is still no place for Racing 92's Donnacha Ryan or his future team-mate Simon Zebo as the Irish RFU continues to favour players based in Ireland, or intending to remain playing there.
Joey Carbery has recovered after suffering three broken bones in his wrist against Fiji last November to take his place in the extended training group.
Leinster's Sean Cronin, who missed out on selection for the November international wins over South Africa, Fiji and Argentina, also returns.
Fergus McFadden is back and will hope to make his first Test appearance since the 35-25 triumph over Scotland in Dublin in March 2016.
Ulster hooker Rory Best retains the captaincy as Ireland aim to improve on their second-place finish in last year's tournament.
Ireland, unbeaten in their past seven matches, face France in Paris on 3 February and then play Italy at the Aviva Stadium in Dublin on 10 February.
"It's been great to witness some quality performances from provincial teams over the last seven weeks of European and derby matches, with a number of players performing well," said Ireland head coach Joe Schmidt.
"There were some very tight decisions but it's great to see some competitive depth in a number of positions."
Ireland squad to face France and Italy in Six Nations
Forwards: Rory Best (Ulster), Jack Conan (Leinster), Sean Cronin (Leinster), Ultan Dillane (Connacht), Tadhg Furlong (Leinster), Cian Healy (Leinster), Iain Henderson (Ulster), Rob Herring (Ulster), Dave Kilcoyne (Munster), Dan Leavy (Leinster), Jack McGrath (Leinster), Jordi Murphy (Leinster), Peter O'Mahony (Munster), Andrew Porter (Leinster), Quinn Roux (Connacht), James Ryan (Leinster), John Ryan (Munster), CJ Stander (Munster), Devin Toner (Leinster), Josh van der Flier (Leinster).
Backs: Bundee Aki (Connacht), Joey Carbery (Leinster), Andrew Conway (Munster), Keith Earls (Munster), Chris Farrell (Munster), Robbie Henshaw (Leinster), Rob Kearney (Leinster), Ian Keatley (Munster), Jordan Larmour (Leinster), Kieran Marmion (Connacht), Fergus McFadden (Leinster), Luke McGrath (Leinster), Conor Murray (Munster), Johnny Sexton (Leinster), Rory Scannell (Munster), Jacob Stockdale (Ulster).