Cat teeth tartar. Illustration of the mouth and teeth of a cat with an accumulation of tartar, a mineralised and hardened form of dental plaque. Plaque is a bacterial biofilm that can form on teeth and can cause tooth decay. If not treated, the condition can lead to gingivitis, peridontitis and tooth loss. For a sequence of images on cat dental diseases, see images C029/9568 to C029/9571.