The Nashville Predators prospect completed a lovely passing play with Ivan Provorov and Andrei Svetlakov, scoring five-hole in front of the net at 5:00 of the extra frame. In regulation, Kamenev had tied the game with just 44 seconds left.
"This will really help us to be more like a team, to play with emotion and without mistakes," said Kamenev.
Russia, which earned the silver medal last year after losing 5-4 to Canada in the final, is seeking its first gold since Buffalo 2011. The Russians have medalled five straight times at this tournament.
Under head coach Valeri Bragin, the Russians tend not to do things the easy way, but usually find a way. It would have been the biggest upset in World Junior history if Denmark had prevailed.
"I want to say sorry to our parents!" said Russia's Radel Fazleyev with a smile of relief. "It was really nervous, but we won and that’s what matters."
The underdog Danes can be proud of their effort. This is just the fourth time the Danes have even been in the elite division. They played a disciplined team game to counter Russia's superior individual skills, and it almost paid off.
"They’re just normal people like us, and I think it shows that we can compete with anybody in the world," said Denmark's Alexander True.
The Russians trailed twice, but showed character by not letting this one get away.
Finishing eighth for the second straight year was another major accomplishment for Denmark. The small Scandinavian country will host the IIHF Ice Hockey World Championship in 2018 (Copenhagen and Herning), and this result should help to drum up more hockey fever at home.
"It’ll be fun to get all the hype to Denmark, just to see how it’ll be," said True. "I’m excited to see how the Danish people will welcome the World Championship."
Yegor Korshkov and Artur Lauta added a goal and a helper apiece for Russia, which will face the USA-Czech Republic winner in the semi-finals.
Thomas Olsen had a goal and an assist for Denmark, and Markus Jensen and Emil Christensen also tallied.
Russia outshot Denmark 46-21 as Alexander Georgiev and Thomas Lillie got the call in net.
"I’m happy with the way I played today," said Lillie. "Unfortunately it wasn’t enough to shut down Russia in the last minute."
Just 2:49 in, Russia drew first blood. Korshkov picked up the puck behind the Danish net and surprised Lillie with a swift backhanded wraparound. It was his first goal of the tournament.
Mathias From nearly equalized for Denmark when he split the Russian defence on a spectacular end-to-end rush. However, Georgiev foiled him as the net came off.
The Danes kept on pushing. William Boysen toppled Russian forward Radel Fazleyev with a big open-ice hit in the Russian zone.
Early in the second period, Denmark tied it up. After Olsen took a bad-angle shot from the right corner, Jeppe Holmberg cleverly bounced the puck to Markus Jensen off the side of the Russian net. Jensen cut in front of the Russian net and put it home.
Denmark jumped into a 2-1 lead at 9:20. Kristian Jensen held off Alexander Polunin as he circled around the Russian net and swivelled on the left side boards to slide it on net. Georgiev kicked out the rebound with his left pad and put it right on Olsen’s stick, enabling him to shoot it into the gaping cage.
Russia came in with the tournament’s second-best power play (35.7 percent), but couldn't cash in when the Danes took their first minor of the afternoon to start the third period.
The Russians dominated the play in the final stanza, outshooting Denmark 20-4.
At 12:31, Russia tied it up again. Off a faceoff in the Danish zone, Dergachyov found Lauta right in front and he lifted a forehand that squeaked past Lillie's glove.
With 5:24 remaining, Denmark made it 3-2. Christensen snared the rebound off Anders Krogsgaard's point drive and backhanded it high into the net. The Danes celebrated ecstatically.
"I think I still believed that we were going to win that game," said Fazleyev. "I believed that we’re a better team and we deserved it more than Denmark."
Russia wasn't done yet. It called its timeout with under two minutes left. The Russians controlled the puck in the Danish zone, and Kamenev scored high to the blocker side in the final minute to send the game to overtime.
"It’s just tough right now," said True. "But I know when I look back at this, it’ll be a proud day."
"It shows a lot," Lillie added. "It means that the development in Denmark is getting better and better. Of course we’re disappointed, but hockey in Denmark is getting bigger and bigger."
In the only previous World Junior meeting between these two teams, Russia prevailed 3-2 in a shootout at last year’s tournament.
Russian hockey legend Alexander Yakushev was in attendance. He was shown on the video scoreboard midway through the first period.