Gregory Echenique added 15 points and eight rebounds for the Bluejays (11-1), who won their fifth straight.
James Woodard had 15 points and 10 rebounds to lead Tulsa (6-5), which shot 38 percent and committed a season-high 25 turnovers.
Dingman was good on his first seven shots and made a career-high five 3-pointers, getting friendly bounces off the rim and backboard on his third and fourth tries. Dingman also had three steals to go with three rebounds.
McDermott, averaging 23.7 points and coming off games of 30 and 34 points, was just 4 of 9 from the field but made 7 of 8 free throws.
The visitors from Conference USA, who trailed by 22 points in the middle of the second half, got a 3 from Scottie Haralson and two free throws from James Woodard to cut the deficit to 12 with 5:03 left.
McDermott's two free throws and Dingman's 3-pointer pushed the lead to 64-47 with four minutes left.
Echenique's performance helped offset an otherwise miserable start for the Bluejays, who turned over the ball six times in the first six minutes and 10 times in the opening half.
With his parents from Venezuela watching him in person for the first time this season, Echenique scored 10 of the Bluejays' first 14 points.
The 6-foot-9, 260-pounder had two thunderous dunks early. The second came after Zeldric King, whose momentum carried him out of bounds along the baseline, tried to throw the ball off of Dingman's leg. Dingman made a sudden move, causing King to miss, and Echenique picked up the ball and slammed it in.
It was a tough start for McDermott, who was trying to become the first Creighton player with three straight 30-point games since Benoit Benjamin in 1985.
McDermott, who had 35 in a win over Tulsa last season, drew lots of attention from the Hurricane and seemed out of sync until he hit a 3-pointer from the corner to put the Bluejays up 46-28 with 13:35 left.
Kauri Black held McDermott in check for much of the game, but at one point four defenders swarmed him after he took an entry pass. He missed five of his first six shots, including a couple near air balls, and was held to five points in the first half.
Creighton's Grant Gibbs, who shifts from off guard to the point to spell Austin Chatman, came into the night with 30 assists and only two turnovers in four games. He committed two in the first three minutes, but no others. He finished with six assists.
Tulsa struggled more than the Bluejays, missing 12 of its first 15 shots, committing 13 turnovers in the opening half and not reaching double figures until more than 15 minutes had elapsed.
Creighton started pulling away in the middle of the first half. Dingman and Ethan Wragge hit back-to-back 3s to make it 24-8, and long shots by Jahenns Manigat stretched the lead to 32-15.
Heavy snow in eastern Nebraska held the crowd to about 6,000 (15,102 paid). In the middle of the first half, the public-address announcer asked fans in the upper balcony to take unoccupied seats in the lower bowl—a rare invitation at an arena in which attendance averages better than 16,000 a game.
The Bluejays are off until they open Missouri Valley Conference play at home against Evansville on Dec. 29.