Paul Pierce led Boston (2-1) with 15 points on 5-for-6 shooting from the field. Glen Davis had 12 points, Kevin Garnett and Leon Powe added 10 each, and Pruitt had eight.
Yao Ming led Houston (2-1) with 16 points.
After Pruitt's jumper, the game saw a frantic final seconds when Scola drove the lane and had his layup attempt blocked off the backboard by Boston's Darius Miles with a second left.
The Rockets retained possession with 0.4 seconds remaining when Scola took an inbound pass from Von Wafer and hit a 10-foot jumper as the horn sounded. Officials reviewed the play and ruled that time had expired before Scola released the shot, preserving the Celtics' victory.
Both teams were physical, combining for 52 fouls, including four technicals over the first three quarters.
Houston trailed 48-46 at the half, but built a nine-point lead in the third quarter after back-to-back jumpers from Landry. The Rockets outscored the Celtics 31-24 in the third quarter to take a 77-72 lead into the fourth.
The Celtics went on to outscore the Rockets 18-12 in the fourth, helped by five Houston turnovers.