BOSTON: Ray Allen scored 23 points and Paul Pierce chipped in 20 as the defending champion Boston Celtics beat the Chicago Bulls 109-99 in the seventh game of their first round playoff series.

"It was a long, grueling series. I thought this was one of the most mentally tough series I've ever been in," Pierce said.

"Thank goodness we were battle-tested and we were able to pull this out in seven games. We still are the champs until somebody knocks us off."

Boston pulled away just before halftime then held on to oust Chicago in regulation time. The clubs played a record seven overtimes in the first six games of the series.

"I don't see great. I just see hard," said Celtics coach Doc Rivers. "For a coach, it's just: Win the series."

Allen had a 51 point performance in game six for Boston who will play Orlando in the next round which begins Monday.

The seventh-seeded Bulls return to Chicago knowing they took the defending NBA champions to the maximum.

Ben Gordon scored 33 and Kirk Hinrich scored 14 of his 16 in the fourth quarter to help Chicago cut it to three points.

Boston made all 11 of its free throws in the last two minutes to hold on.

The four overtime games was a record for a series, and the seven overtimes total were the most any team has ever played in an entire playoff.

Kendrick Perkins had 13 rebounds, Rajon Rondo had 11 assists and Eddie House scored 16 points - going five-for-five from the floor, including four three-pointers. Joakim Noah had 15 rebounds for Chicago.

Celtics forward Glen "Big Baby" Davis, who scored 15 as the sub for injured star Kevin Garnett, said he was glad to finish this one off in the regulation 48 minutes.

"Oh, my God. Overtime after overtime after overtime," Davis said. "We did what we had to do to get the job done."

Bulls point guard Derrick Rose scored 18 with three assists, failing to follow up on his game one playoff debut in which he scored 36 points with 11 rebounds. The NBA rookie of the year averaged just 12.7 points and 4.2 assists in the four Chicago losses.

"We had a lot of young guys who went through it for the first time. I think that will help us in the future," said Bulls coach Vinny Del Negro. "Whenever you can go through an experience like this, I think it's only going to make you better. Knowing how the level of physicality goes up, knowing how playoff basketball is played. ... It's a great learning experience for us."