I brush their teeth regularly with poultry flavored toothpaste. The kind I buy is from the vets. It's C.E.T enzymatic toothpaste. I have used Petrodex from PetSmart, but thought the enzymes in the C.E.T. might be more effective for cleaning, since I cannot brush theirs as thoroughly as I do my own. I keep forgetting to ask the vet about that.
They all love to have their teeth brushed, because I let them lick their toothbrushes between brush strokes. Geordie and Chockie are fairly easy to brush, but India is a little less cooperative That's why she's going to need a dental before Geordie.