Should you fail to remove {plaque} thoroughly & regularly, calcium salts from saliva may be precipitated into the plaque. This will cause the plaque to harden & become like the scale in a kettle. This hardened plaque is known as calculus or tartar.
Some toothpastes are designed specifically to reduce the build up of calculus. You will need to visit your dentist for removal of calculus. They may use a selection of hand or ultrasonic instruments to do this.
