Calculus is dental biofilm (plaque) that has mineralized by crystals of calcium phosphate mineral salts.  Calculus is a hard tenacious mass that forms on the clinical crowns of natural teeth, dental implants, dentures, and other dental prosthesis.  Calculus is classified by its location on a tooth surface related to the adjacent free gingival margin, that is, supragingival and subgingival. (Wilkins’ 13th Edition Clinical Practice of the Dental Hygienist)

My clinical experience:

I had a lot of experiences with calculus during my clinical semesters.  Unfortunately, I was unable to get many pictures but below I have a few cases of before and after removal as well as a photo of a mandibular anterior lingual surface “calculus bridge”.

Before and After- Calculus removal from a dental bridge prosthesis

Clinical photo of # 24 & #25 after calculus removal- The calculus was causing severe BOP and recession

Clinical photo of “Calculus Bridge” on mandibular lingual anterior surface