Linked from
The 11 pages that link to Dental calculus, each with the reason it gives.
Oral hygieneCompared with: Unlike fresh plaque, calculus generally requires professional removal.
GingivitisRelated: Calculus retains plaque and can make effective home cleaning more difficult.
Dental abrasionRelated: Scraping calculus with instruments can accidentally abrade tooth tissue.
ToothbrushRelated: Once plaque mineralizes, ordinary toothbrush bristles cannot remove it.