Tramaine Isabell Jr. led all scorers with 24 for Saint Louis, which will meet second seed Davidson in the second semifinal game Saturday. The Billikens (21-12) lost the only regular season meeting with the Wildcats, 54-53, on Jan. 26.
Jordan Goodwin added 17.
Dayton fell to 21-11 with the loss, and will have to sweat out Selection Sunday. Jalen Crutcher led the Flyers with 18. Jordan Davis finished with 12.
The third meeting of the season for the Flyers and Billikens - the teams split in the regular season, as they each won on their home courts - was a defensive affair for the first 23 minutes.
Dayton only led 30-29 at halftime despite making 54 percent of its shots in the first half, compared to Saint Louis' 33 percent shooting percentage.
The team traded free throws for the first three minutes of the second half and found themselves tied at 33 following Trey Landers' layup.
After Landers' lay-in, Saint Louis outscored Dayton 12-5 in a span of 3:47. Isabell Jr. knocked down two 3s in the stretch as the Billikens took a seven point lead, 45-38.
Saint Louis extended its lead to as much as nine after a Bess jumper in the lane before the Flyers fought back with a 7-0 run, highlighted by a long Crutcher 3.
However a Goodwin 3 and a French jump hook on consecutive possessions pushed the Billikens lead back to 58-51. Bess' layup and jumper on back-to-back possessions following a time out extended Saint Louis' advantage to 62-51.
Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.