Despite the technical fouls, there was little of the tension that characterised Game 4, when Jimmy Butler and Marcus Smart got in each other's face on the court and continued the criticism in their postgame comments.
Horford had 21 points, nine assists and seven rebounds for Boston, which entered the playoffs as the No. 1 seed in the East. The Celtics lost the first two games at home - with Game 1 just a day after Thomas' sister died in a car crash.
After Bulls point guard Rajon Rondo broke his thumb, though, the Celtics took Games 3 and 4 in Chicago to tie the series.
The Celtics started slowly on their home court, making just one of their first nine shots to fall behind 12-4. Boston missed its first eight three-point attempts before making three in a row at the end of the first quarter.
Rondo, who was the point guard on the 2008 Celtics team that won the franchise's record 17th NBA title, did not play for the third straight game because of the broken thumb and strained ligament in his right wrist. He was on the court handling a basketball with his left hand before the game, then sat on the Bulls bench in a suit and cheered on his teammates.
