Russell Westbrook added 15 points for the Thunder, who will have a chance to pull even with San Antonio atop the Western Conference when they meet the Spurs Monday.
Oklahoma City improved to 47-16 with its latest win.
Paul Pierce netted 20 points for the Celtics, whose five-game winning streak came to an end.
Former Thunder player Jeff Green was held to eight points in his first game at Oklahoma City since a Feb. 24, 2011, trade.
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