Tooth extraction. Close-up of the lower jaw of a patient, showing the location (centre) of a wisdom tooth after extraction. Here, the built up tartar around the tooth can still be seen (vertical, centre). Tartar (calculus) is a form of hardened dental plaque that builds up on and between teeth. It is caused by the precipitation of minerals from saliva and gingival crevicular fluid (GCF) from plaque.