Maybe if people would ask their vets to provide some data, that would
increase the number of samples and provide helpful information.

I think bones undoubtedly have a beneficial impact re. tartar build up
relative to soft food (based on my experience in clinic). Mechanical action
is the best way to clean teeth. A lot of the time this action isn't provided
by soft food or by kibble. (my vet will recommend an occaisional
'recreational bone' for minor cases of dental disease, and it seems to
help).

There definitely seems to be a propensity in smaller breed dogs towards
'pirate mouth' (not sure if this correlates with feeding kibble vs. soft, or
perhaps how often small dogs have their mouths opened? or perhaps simply jaw
conformation?).

Of my two dogs (both more or less exclusively kibble fed, the old one can't
take bones, so neither gets them), one has nearly perfect teeth, the other
has some minor scale build up on one of his molars.

Dale