[aimee]

I agree with others that brushing is best. There are several dental diets marketed which have gone through the Veterinary Oral Health Council protocol and shown to be effective in reducing plaque and calculus accumulation. These diets have a relatively larger kibble and different textures or coatings that contribute to decreased formation of plaque and calculus.

I hadn’t heard that kibble size alone could decrease calculus formation, but I found a study that evaluated just that “Results showed that increasing kibble diameter by 50.0% was associated with a 42.0% calculus reduction……with the most pronounced effect being observed on caudally-located crushing teeth compared with incisor and canine teeth. ” Hennet 2007 I haven’t read the full text so I don’t know what the original and test diet kibble size was but did find it interesting.

Just as human dentists don’t recommend gnawing on a piece of food as our sole dental health program I don’t think gnawing on food should be the total answer for a dog’s dental health program either. However, apparently kibble size plays a role in calculus reduction on the back teeth which is what the OP vet recommended the larger kibble size for. For those that wondered where the OP vet ever came up with that idea, it could be that the OP vet was sharing what he/she learned from reading the veterinary dental literature.