As the Bruins began to slowly rebuild their game in the last couple of weeks, not everything clicked. Perhaps the most consistent positive was the play of the reunited fourth line. The trio of Daniel Paille, Gregory Campbell and Shawn Thornton, so instrumental in the Stanley Cup championship season of 2011, broke up due to injuries and under-performance among the regular top line forwards. Paille saw some time with David Krejci while Campbell played effectively with Jaromir Jagr for a short time. However, as the team got healthier and the old Milan Lucic returned to the mix after a one-game scratch, the B’s playoff lineup came more into focus. And now with Paille, Campbell and Thornton back together, all three seem re-energized, and the Bruins are the beneficiaries of that. The Merlot line, as the group is commonly referred because of the color of their practice jersey, was front and center in the B’s dominant 4-1 victory over the Maple Leafs in Game 1 on Wednesday. Both Campbell and Paille picked up an assist on the B’s first goal, thanks to Paille crashing the corner on a Campbell dump-in. He got the puck back for Campbell, who tried a wrap-in that failed but bounced out to Wade Redden, who fired in a long shot. In all, the line accounted for 10 of the B’s 30 hits, including a team-high five from Thornton in a pretty loud 9:18 of ice time. If you sensed a renewed vigor, you’re right. “When me and Soupy were able to play with other players, it just gives you a lot more confidence in what to do,” Paille said yesterday at the Garden on the team’s day off. “When we came back to play together, we just realized that we can play when we need to, and we want to continue to not only play our role and doing the simple things, but also help out as much as we can like we used to.”