After a slow start, Sweden took control in the second period with four goals in six minutes to take a 6-1 lead in the Group A game.
Playing without the NHL stars that led the team to the title in 2006, Sweden looked shaky early on.
Goaltender Johan Backlund gave up a generous rebound that Giorgio de Bettin fired in from a sharp angle at 3:06 of the first period to give Italy a surprise 1-0 lead.
Sweden then had a 5-on-3 power play midway through the first period but couldn't capitalize.
However, Italy's lead didn't last long.
Davidsson got the Olympic gold medallists on the board with a superb individual effort at 15:31 of the first.
After picking up a loose puck at his own end, Davidsson skated past several defenders and rifled a low shot past Italy goaltender Andrea Carpano to tie the game.
"We were a bit off our game at first," Davidsson said. "But we knew that if we just kept playing our system we would be OK. It was good that we went into the first break up 2-1 instead of down 1-0."
Playing with a man advantage, Fredrik Emvall deflected a shot from the point by Dick Tarnstrom at 17:19 to give Sweden a 2-1 lead heading into the first intermission.
The second period was all Sweden.
Tony Martensson started the four-goal onslaught when he picked up a rebound at the side of the net and tucked the puck past Carpano.
Fredrik Bremberg gave Sweden a 4-1 lead, taking a perfect pass from Davidsson and scoring on a slapshot from the edge of the faceoff circle. Davidsson scored his second goal of the night at 8:43 as Sweden went up 5-1.
Jonathan Hedstrom completed the scoring in the second period with a goal at 9:53 on a two-man breakaway.
Alex Steen of the Toronto Maple Leafs is the only NHL player currently on Sweden's roster.
Without the likes of Henrik Zetterberg, Michael Nylander and Niklas Kronwall, who all played on the 2006 world championship team, Sweden will need players like Davidsson, Emvall and young star Nicklas Backstrom to step forward.
Daviddson also assisted on Per Hallberg's goal in the third.
Also in Group A, Sandy Jeannin scored the winning goal in the last minute of the second period to lift Switzerland to a 2-1 win over Latvia, while in Group C, Germany gave Canada all they could handle, but the Canadians held on for a 3-2 victory and Montreal Canadiens goalkeeper Jaroslav Halak made 24 saves to lead Slovakia to a 3-0 win over Norway.
Marek Uram opened the scoring 12 minutes into the first period, with Boston Bruins defenceman Zdeno Chara doubling the team's advantage just 51 seconds later.
The Norwegians became visibly frustrated in the second period, clocking 10 minutes in the penalty box as the Slovaks kept their spotless record intact.
Minnesota Wild forward Branko Radivojevic converted one of the power plays to put the 2002 champions ahead 3-0 at 17:39 before a scoreless third period.
Norway only returned to the top division last year with Edmonton Oilers forward Patrick Thoresen the only NHL player on its roster.