Prescription Diet canine t/d and feline t/d are specifically formulated as nutritional aids for
pets with periodontal disease.  Every bite helps reduce plaque and control tarter. 
It also reduces bad breath in dogs.  The kibble are like edible toothbrushes!

Prescription diet t/d is different from other dry food in that the kibbles are larger and do
not shatter immediately when chewed.  Instead, the tooth penetrates the
kibble causing plaque and other debris to be losened from the surface.
  This helps fight bad breath and disease.