BIRMINGHAM, Ala. --- JaJuan Smith and Tennessee lost the lead, but not their poise.
Smith hit four consecutive free throws in the final 13.6 seconds of overtime, and the Volunteers held on for a 76-71 win over Butler on Sunday in the second round of the NCAA Tournament
But the Volunteers barely survived a game that, at times, they threatened to turn into an East Regional rout.
The first second-round game ever to feature two 30-win teams definitely lived up to the distinction.
The Vols (31-4) scored six consecutive points inside after the Bulldogs took their first lead in the final 2 minutes of overtime, including benched guard Ramar Smith's basket with 27 seconds left to make it 72-68.
Butler still wouldn't go away. Pete Campbell followed a missed shot to make it 72-70 with 16 seconds left.
JaJaun Smith then made both free throws, and Julian Betko rebounded a missed 3-pointer by A.J. Graves and was fouled with 4.9 seconds left for Butler. He made one of two from the line, and Smith grabbed the rebound before icing the game with foul shots at the other end.
Wayne Chism led foul-plagued Tennessee with 16 points, while Tyler Smith added 15 and JaJuan Smith had 11.
The Vols led by 13 in the first half and 10 in the second half, but Butler kept coming back.
The Bulldogs, who were behind for the first 37 minutes, took their first lead on Graves' short jumper in the paint to make it 68-66 with 1:46 left in overtime. Ramar Smith and Chism both scored inside to regain the lead in the final minute.
Graves shot just 6-for-18, but he led Butler with 21 points. Pete Campbell, who made eight 3-pointers in the first round, added 12 points, and Willie Veasley had 11.
NORTH CAROLINA 108, ARKANSAS 77
In Raleigh, N.C., North Carolina put on a show for its home-state fans in its first two NCAA Tournament games. Now, the top overall seed is off and running to the round of 16, where another comfortable setting awaits.
Wayne Ellington scored 20 points, and the Tar Heels raced to a double-digit lead in the first 5 minutes of a second-round win over Arkansas, sending North Carolina to Charlotte for the East Regional semifinals.
Ty Lawson had 19 points and seven assists for the Tar Heels (34-2), who will face fourth-seeded Washington State on Thursday night.
The Tar Heels scored the first nine points, led 51-26 at halftime, and shot 68 percent for the game. They became the first team to score 100 points in their first two NCAA games since Loyola Marymount did it against New Mexico State and Michigan in 1990.
The ninth-seeded Razorbacks (23-12) never got closer than 21 points after the break.
LOUISVILLE 78, OKLAHOMA 48
In Birmingham, Ala., Louisville played to near-perfection, romping past Oklahoma in the second round.
Louisville harassed freshman star Blake Griffin with double teams down low, trapped the Sooners, and ran every chance it got. The Cardinals neatly zipped passes in the paint all night for easy scores inside.
Little-used Will Scott captured a loose ball, twisted his body and hit a heave from near half-court at the halftime buzzer for a 44-22 lead.
Starting five players born outside Kentucky, the third-seeded Cardinals (26-8) reached the round of 16 for the first time since 2005. They will take on Tennessee on Thursday night.
Louisville shot 59 percent for the game.
David Godbold hit four 3s and finished with 15 points for sixth-seeded Oklahoma (23-12). Griffin looked like an average freshman, held without a shot for the opening 12 minutes and limited to eight points.