"That's vitally important [to have defenders scoring] and we know how crucial set-pieces are," said Bruce, with seven of the Magpies past nine league goals coming from the backline.
"When you have three centre-backs playing, if you can capitalise, then good."
Bruce also backed his attacking three of Joelinton, Miguel Almiron and Allan Saint-Maximin, who again failed to find the net. Only Joelinton has scored this season, and that was back in August.
He added: "They are doing everything but [score]. They are creating chances, and as long as they keep contributing, I am sure the rest will come."
Bournemouth boss Eddie Howe: "They punished our sloppy mistakes. In the end we created chances, but did not put them away.
"We had the initiative of the game, but gave it away, I felt we should have kept the ball better and we need to learn from it.
"We are looking for consistency; backing up a great win with another one, and today we missed an opportunity. This result will really hurt for the next two weeks."
On their goal from a well-worked set-piece: "Credit to Jason Tindall [Bournemouth's assistant manager] - this is something we work on in training - and credit to the players too.
"Moments like that can really win you the games, but right now I have got something else in my mind."