My DIL does her poodles. She uses a people dental pick -- looks like this only she has a smaller one:
Dental Pick and Scaler - Plaque and Tartar Removers | Dentek I cannot get mine to keep still enough for me to brave sticking anything sharp into their mouths. But her poodles stay nice and still for her to clean them. She never has to get the dentals done at the vet.