Celtics 117, Raptors 116 (OT): Marcus Smart’s follow shot beat the buzzer and lifted visiting Boston to a dramatic victory over Toronto.

Lou Williams drained a 3-pointer with 4.9 seconds left to give the Raptors a two-point advantage and Celtics guard Isaiah Thomas hurried a shot in the final second and Smart tipped the ball in to move Boston into eighth place in the Eastern Conference. Thomas scored 25 points, Tyler Zeller had 20 points on 8-of-10 shooting and grabbed nine rebounds and Evan Turner added 18 points, 10 assists and six rebounds.

DeMar DeRozan scored 38 points and Williams added 27 for the Raptors, who fell 1 1/2 games behind third-place Chicago in the East. Tyler Hansbrough had 18 points and eight rebounds and Jonas Valanciunas added 12 points and 14 rebounds.

A dunk by Brandon Bass gave the Celtics a 100-94 edge with 2:18 left in regulation before DeRozan and Williams scored consecutive baskets and DeRozan added two free throws to tie it, while Turner twice scored baskets to push Boston back in the lead and DeRozan answered with a tying hoop both times. The Raptors led most of the overtime but the Celtics took a 114-113 lead on Smart’s 3-pointer with 32.9 seconds left and Bass split two free throws before Williams briefly put Toronto ahead.

DeRozan had 17 first-half points but the Raptors let a 12-point second-quarter deficit slip away and the score was knotted at 47 at the break. Boston opened the third quarter with a 15-2 burst to take a 13-point advantage and held an 81-70 lead entering the final stanza.

GAME NOTEBOOK: Toronto standout PG Kyle Lowry (back) missed his sixth consecutive game. … Celtics PF Jared Sullinger was scoreless in 12 minutes in his second game back from a foot injury but did collect seven rebounds. … Raptors PF Amir Johnson (ankle) sat out due to an injury suffered in Friday’s game against Brooklyn.