IPFW will play tournament host Eastern Michigan in a 7 p.m. tip on Saturday.
Gaines' point total runs his streak of 20 or more points in a game to an NCAA-leading nine, and the 29th time overall in his career.
The teams battled back-and-forth for the first three minutes, and the teams were tied at three before IPFW ran off a 9-2 run to lead 12-5 nearly halfway through the first half, and would not trail the rest of the half. The first half lead grew to as many as 10 with 5:02 to play, before the Broncs (1-3) cut the gap to five at the break at 30-25.
The 'Dons kept their lead until UTPA took their first lead of the game on a Brandon Provost three-point basket with 12:30 to play in the game. IPFW quickly responded by scoring the next eight points and pushing the advantage to six at 50-44.
The Broncs slowly chipped away at the lead, eventually tying the game at 54, and twice more before the teams found themselves knotted at 62 through the first 40 minutes of play in the game.
UTPA took the first lead of the opening overtime session, leading by two points twice in the game, before Gaines made a free throw with 44 seconds left in the game to knot the score at 69 as a missed jumper and a turnover ended the first overtime where it began, sending the teams into a second five-minute period.
The Mastodons scored the first five points of the second overtime period on a three-point play by Gaines and a jumper by Harden, and would not trail in the period; however, a Justin Leathers tip-in with five seconds left sent the teams into the third - and eventually final - overtime period.
In the third extra session, UTPA jumped ahead by six through the first two minutes, before Kevin Harden drained a three-point basket to cut the gap in half. A free throw and a three-pointer in back-to-back possessions by Gaines capped a 7-0 Mastodon run.
A jumper by Urbanus gave the 'Broncs a one-point, 94-93 lead, before Gaines drained a pair of free throws 12 seconds later to give IPFW a 95-94 lead, one it would not give up for the rest of the game. Harden made a free throw with four seconds left, before McCray picked off the inbounds pass, making one of two free throws, giving IPFW a 97-94 lead, before intercepting the inbounds pass for the second straight possession, securing IPFW's 97-94 win.
Hines pulled down a career-high 13 rebounds for his first double-double with the 'Dons, as Harden also picked up a double-double by adding a dozen rebounds. Joe Reed grabbed a career-high 12 rebounds, with Isaiah McCray adding eight. Pierre Bland dished out a team-best four assists, while Harden and McCray each had three steals.
IPFW hit 30-of-83 shots from the field (36.1 percent), 5-of-26 from three-point range (19.2 percent), and 32-of-57 free throws (56.1 percent), as the Broncs hit 43.7 percent (31-of-71) shots in the game, 8-of-25 from long range (32.0 percent), and 66.7 percent (24-of-36) of its free throws.
UTPA was led by Provost who scored 28 points for the second straight game, while Urbanus had a 20-point, 10-assist double-double, with Leathers adding 18 points and 12 rebounds.