Deep Cleaning

In the US, the term Deep Cleaning refers to a procedure performed in a regular dental office to remove tartar from below the gum line.  This procedure, covered by most dental plans, is generally preformed as an effort to stave off root planing and scaling procedures that are performed by periodontists.

In a deep cleaning, the dentist or hygienist, using a scaler or other sharp instrument, scrapes at the surface of teeth, the dentin, under the gum line hunting for tartar to remove.  It is painful so numbing is most often required. 

Deep cleanings are done in the blind, meaning the dental professional cannot see what they are doing under the gum-line, so some tartar inevitably remains.  The temporary disruption of some plaque and tartar has clinical value, but relief is short-lived.