Yep, I think it's necessary, for the same reasons we use toothpaste!
I use Virbac Enzymatic toothpaste from the vets - the enzymes break down the plaque in the mouth so there's no need for brushing, you can just smear it on a chew or just let them lick it off your finger

__________________
Some days you're the dog: some days you're the lampost

When I feel blue, I start breathing again