Victory over Samoa in Newcastle on Saturday would put the Scots through to the last eight while defeat would end their involvement in the tournament if Japan beat the United States in their last game.
If Scotland lost and failed to pick up a bonus point in defeat they would also exit the tournament in the unlikely event that Japan drew and scored four or more tries.
"For a lot of us this is going to be the biggest match of our careers," Denton told reporters.
"For most of the people on our team this is our first World Cup but now we’ve essentially got a playoff game... If we win we’re into the quarter-finals, if we lose we’re probably not."
Scotland overwhelmed Japan and the U.S. in their first two matches before losing 34-16 to South Africa.
"We can’t go into a game and let a team impose what they want to do on us, we need to do it the other way around, so for the coming weekend we need to impose our game on Samoa," Denton said.
"We need to make sure we get a good first half. We need to come out of the blocks raring to go and not give them a foothold in the game."
Scotland coach Vern Cotter has rotated his squad in the first three matches and Denton believes that policy will pay dividends.
"It means that most players haven’t been run into the ground. Most players have had sufficient rest between the games," he said.
Prop Gordon Reid is expecting a very physical challenge from the Samoans who cannot reach the last eight.
"Samoa are quite a difficult team, big straight-line-running forwards," he said. "The last time we played them they actually beat us, so we need to take that into consideration.
"Everyone says it’s a nothing match for them but Samoa’s a proud nation and they’ll come out guns blazing and they’ll want to win. They’ll want to finish on a high."
Scotland started slowly against Japan and the U.S. before racking up points in the second half.
"We’ve spoken about that," flanker Ryan Wilson said. "Even if it is tight in the second half we know we can edge our way through it and win the game.
"The set-piece is massive for us, we need that to function. We know that if we’re in the game we can go on and win it."
(Reporting by Ed Osmond; editing by Toby Davis)
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