Teeth after ultrasonic cleaning. Close-up of a dental patient's lower teeth that have had a large accumulation of plaque and tartar cleaned off with an ultrasonic scaler. Plaque is a bacterial biofilm that can form on teeth and can cause tooth decay. Tartar is a mineralised and hardened form of dental plaque. If not treated, the condition can lead to gingivitis, peridontitis and tooth loss. For the teeth before cleaning, see image C034/2622.