I have used Plaque Off for several years for my dogs teeth. I have no experience of the product on the teeth of cats. After a few weeks of use it softens the plaque on the teeth which is then easily removed by the dogs chewing a toy or similar or it can be brushed off with a toothbrush. I have miniature breeds of dogs who, in my experience, do have more problems with the build up of plaque. I used to own giant breeds of dog and never ever saw any plaque on their teeth!As Plaque Off contains iodine it cannot be given to dogs with thyroid problems.