Denmon scored all his points in the second half, going 5 of 8 from 3-point range in the half, and Ricardo Ratliffe finished with 13 points and a career-high 15 rebounds.
The Tigers (27-4, 14-3 Big 12) slowly pulled away in the second half with 12 of their 3s coming after halftime.
The win gave Missouri a school record for victories in the regular season.
Texas Tech (8-22, 1-17) stayed with the Tigers in the first half but couldn't keep up with Missouri's long-range barrage, walking away with its worst ever finish in Big 12 play.
Jaye Crockett scored 17 points and Ty Nurse added 12 for the Red Raiders.
The Tigers turned to the 3-pointer early in the second half and got nine of their first 11 field goals in the opening 12 minutes from beyond the arc to go up 64-48.
They had six in a row at one point, with Denmon hitting four of them after going scoreless in the first half.
They hit 16 of 26 from 3-point range (61.5 percent). Ratliffe dominated the offensive glass, grabbing his 12th rebound with 10 minutes remaining in the game.
Missouri outrebounded the Red Raiders 30-23 and got 14 second-chance points off 11 offensive rebounds. Ratliffe had eight of those 11.
After a somewhat lethargic opening half, the Tigers moved the ball around and shared it after the break, finishing with 18 assists - led by Phil Pressey's eight.
Missouri turned the ball over just once in the second half.
Robert Lewandowski, the lone senior playing his final home game, pulled Texas Tech to 32-30 to open the second half, but back-to-back 3s by Matt Pressey put the Tigers up 38-30.
Ratliffe added a bucket and Denmon, Missouri's leading scorer, got his first points of the game on a 3-pointer to put the Tigers up 43-33 with 16:32 remaining.
Missouri struggled from the field early, hitting on just 10 of 25 from the field in the first half.
The Tigers dominated the boards, however, but scored only three field goals - two of them putbacks - in the final 11 minutes of the first half.
The Red Raiders used a 10-4 run, including five points from Luke Adams, who hit a 3 to pull them to 21-20 with 5:13 remaining. Missouri then stretched the lead to 32-26 on two free throws each from English and Michael Dixon.
Texas Tech's Clark Lammert scored off a rebound to close the half with the Tigers up 32-28.