Versatile back Lowry and wing Hansen were on Wednesday included in Andy Farrell's 37-man squad.
Flyer Lowe has been ruled out of the tournament due to a muscle injury, but fly-half Joey Carbery is included despite suffering a fractured elbow last month.
Cian Prendergast will take part in a pre-Six Nations training camp in Portugal as a development player.
Ireland face defending champions Wales in their first match of the tournament at the Aviva Stadium on 6 February.
Head coach Farrell said: "In November we challenged the group to get up to speed quickly so that the team could perform at international level.
"The same will apply for this Six Nations campaign, we need to be at our best against Wales on the opening weekend.
"We have a strong squad with competition for places across the board, there is a nice blend of experienced internationals and guys who have had their first taste of this level in the past 12 months.
"The games in November gave us a good foundation to build on and areas where we know we will have to improve. It will be an exciting Championship with so many strong squads and impressive performances across the board during the autumn."
Backs: Bundee Aki, Robert Baloucoune, Joey Carbery, Jack Carty, Craig Casey, Andrew Conway, Keith Earls, Jamison Gibson Park, Mack Hansen, Robbie Henshaw, James Hume, Hugo Keenan, Jordan Larmour, Michael Lowry, Conor Murray, Garry Ringrose, Johnny Sexton (captain).
Forwards: Ryan Baird, Finlay Bealham, Tadhg Beirne, Jack Conan, Gavin Coombes, Caelan Doris, Tadhg Furlong, Cian Healy, Iain Henderson, Rob Herring, Ronan Kelleher, Dave Kilcoyne, Peter O’Mahony, Tom O’Toole, Andrew Porter, James Ryan, Dan Sheehan, Nick Timoney, Kieran Treadwell, Josh van der Flier.