Ruben Patterson scored 21 points and Earl Boykins had 15 for the Bucks, who have only two wins in their past 13 games -- both against the Celtics.
The Bucks scored the first seven points, led 56-43 at halftime and never trailed.
"We tried to take their crowd out of it a little bit and get our confidence going," Bell said. "We had a lot of guys that came through for us tonight because we really need this win."
Boston climbed back from a 14-point third-quarter deficit to pull within two in the closing seconds, but the Celtics couldn't get off a shot after Allan Ray's steal with 12 seconds left.
Ray had the best look from the side, but passed up the shot. Sebastian Telfair ended up with the ball but his last-second heave came after the buzzer.
At halftime, the Celtics commemorated the 1957 team on the 50th anniversary of its 125-123 double-overtime win over the St. Louis Hawks to win the first of an NBA-best 16 championships.
Eight of the team's players were on hand -- including Bill Russell, Tom Heinsohn, Bill Sharman and Bob Cousy -- and each player was presented with a plaque.
"I'm still in awe of the Celtic history that was standing out there on the floor," said Delonte West, who returned from a five-game absence with a sprained left ankle and scored 13 for the Celtics. "I feel like I'm a part of that. I would love to when I finish up my career, come back and get that type of applause from the crowd."
The 2006-07 Celtics aren't anywhere near competing for title No. 17.
Ryan Gomes had 13 through three quarters, but watched from the bench in the fourth as Boston clinched the worst record in the Eastern Conference and second worst in the league.
"I probably (would have played), but since we were in the hunt for a high draft pick, of course things are different," Gomes said. "I understand that. Hopefully things get better. Now that we clinched at least having the second-most balls in the lottery, the last three games we'll see what happens. We'll see if we can go out and finish some games."
While battling for lottery position, both teams missed key players.
Boston's Paul Pierce will miss the rest of the season with a sore left elbow, while Milwaukee's Michael Redd is out with a sore left knee. Boston was also without second-leading scorer Al Jefferson, and the Bucks played without Mo Williams.
"Michael Redd is a great weapon to have," Gadzuric said. "We have to find a way to come together and get buckets because he is a great 3-point shooter and a great slasher to the paint."
The Bucks shot 75 percent in the first quarter. ... Bell is the only player on the Bucks to play every game. ... Before the game, Pierce said he'd be able to play if the Celtics were in playoff contention but it's not worth risking further injury. ... Powe had 14 in the fourth quarter. ... Boston outrebounded Milwaukee 41-33.