Forty female Beagle dogs, aged 12 to 24-months were divided into four groups of ten dogs each. Results showed that increasing kibble diameter by 50.0% was associated with a 42.0% calculus reduction. Coating the kibbles with sodium tripolyphosphate, an anti-calculus agent, further induced a 55.0% calculus reduction. Sodium tripolyphosphate was shown to be at least as effective as sodium hexametaphosphate. The calculus reduction effect on teeth differed based on tooth location with the most pronounced effect being observed on caudally-located crushing teeth compared with incisor and canine teeth. The relevance of scoring non-crushing teeth when testing a product with mechanical effect on plaque and calculus needs to be questioned.