Bottcher forced Dunstone to play a gentle tap for one in the 10th end and the Canada skip made a nose hit for the victory in the 11th to improve to 6-0.
It was the first round-robin loss for Dunstone (6-1), who could have locked up first place in Pool A with a win.
The only undefeated team in Pool B, Wild Card One’s Brad Gushue, was scheduled to play Nova Scotia’s Paul Flemming in the afternoon draw at the Enmax Centre.
In other early games, Ontario’s Glenn Howard topped Nathan Young of Newfoundland and Labrador 7-3 and New Brunswick’s James Grattan defeated Prince Edward Island’s Tyler Smith 9-3. Saskatchewan’s Colton Flasch dumped Yukon’s Thomas Scoffin 12-3.
Round-robin play continues through Thursday night. The top three teams in each pool will advance to the playoffs.
The final is set for Sunday. The winner will represent Canada at the April 2-10 world men’s curling championship in Las Vegas.