Scaling involve removing plaque (soft, sticky, bacteria infested film) and calculus that consist of hard deposits that have built up on the teeth over time, usually using an ultrasound instrument.
Polishing involve removing the stains and plaque from the teeth surfaces.
The purpose of the scaling and polishing is basically to leave the surfaces of the teeth clean and smooth so that bacteria are unable to stick to them. Bacteria existing in the plaque and calculus can cause gingivitis, destruction to the gingival attachment, bone resorption and pockets formation. It does not replace your regular home care; it is rather a deeper cleaning that removes what your toothbrush failed to remove over the time.
Dental Cleaning
(Scaling and Polishing)