It was also Wideman's first NHL goal since October 13, 2018.
Forwards Joel Armia and Mathieu Perreault earned helpers on the play.
Buffalo retook a two-goal lead with 2:55 to go in the middle frame while on the power play, when Victor Olofsson's shot found its way past Montembeault.
Anders Bjork got on the scoresheet with just 56 seconds left in the second period when he pounced on a rebound.
The Canadiens trailed 4-1 after 40 minutes.
Tage Thompson gave the Sabres their third power play goal of the night at 4:29 of the third period to make it 5-1.
The Canadiens are back in action on Saturday for their home opener at the Bell Centre, with the New York Rangers in town. For tickets to that game,
click here
.