Oklahoma and Kelley Newton (22) found themselves in precarious positions all game long against Indiana State.(AP)

Block scored five of his 17 points in overtime after he dramatically returned from the locker room just before the tipoff of the extra period.

"He's on his way to the oral surgeon," coach Royce Waltman said. "I had said yesterday about how tough I thought Oklahoma was. We said our only opportunity to win was to display some toughness of our own and we did that today."

The Sycamores (22-11) became the latest double-digit seed to advance in this year's tournament. They will face 12th-seeded Gonzaga on Sunday in the second round. The Bulldogs beat fifth-seeded Virginia 86-85 in the first round.

Matt Renn had 22 points to lead Indiana State, which overcame a second-half deficit that at one point matched its seeding. Renn scored 16 points over the final 14½ minutes of regulation as the Sycamores rallied from a 47-34 deficit.

"In the first half I thought I got some good looks and didn't hit them," said Renn, 2-for-9 from the field in the first half and 5-for-16 overall, while going 12-for-17 from the free-throw line. "In the second half we spread out and I took advantage of it."

Renn scored with 2:52 left to give Indiana State a 57-56 lead, its first since 16-15, then added two free throws with 2:18 left to make it 59-56.

Oklahoma (26-7) got within 59-57 on a free throw by Nolan Johnson with 1:23 to play, then came the play that altered Block's dental status.

Hollis Price of Oklahoma drove the lane and was fouled by Block. As the two went to the ground, Price struck him in the face with an inadvertent elbow. While Block was being attended to for the teeth problem, so was Price, whose right elbow was cut on the play.

"Hollis had his triceps tendon torn," Oklahoma coach Kelvin Sampson said. "You could see three teeth on the floor. He was really gouged right down to the triceps muscle. I didn't think there was any way he could have even stayed on the floor."

Price, an 81-percent free-throw shooter, was replaced at the line by Tim Heskett, who shoots 85 percent. Heskett missed both foul shots, but grabbed the rebound.

Johnson tied the score with 34 seconds to play on a drive. Djibril Kante made two free throws with 28 seconds left, giving the Sycamores a two-point lead, but Price, who returned with his elbow heavily taped, scored on a drive with 19 seconds left in regulation.

Block, cheered by the Indiana State fans as he ran in from the locker room, gave the Sycamores a quick lead in the overtime with a steal and layup. Marcus Howard gave them the lead for good at 65-63 on a drive with 3:19 left and Block's drive with 1:44 left made it 68-65.

"That was a huge lift," Indiana State point guard Michael Menser said of Block's return. "The first play he got the steal and the layup. You could see with his teeth out he was in a lot of pain. He's a tough kid."

Johnson, an 83 percent free-throw shooter, made one of two with 5.5 seconds left, bringing the Sooners within 69-68. Block made one free throw with four seconds left and Oklahoma's final chance ended when Johnson's driving jumper from the left side went off the rim at the buzzer.

"I had a real good look," Johnson said. "I thought it was one of my good shots I normally take. It didn't fall for me."

Kelley Newton matched his career-high with 26 points for Oklahoma, while Johnson had 15 and Price 11.

"When you get here you better play well," Sampson said. "Indiana State did. We didn't."

Indiana State has won both its NCAA Tournament meetings with Oklahoma, the first in 1979, when the Sycamores advanced to the title game behind Larry Bird.