Crown-to-root ratio

This X-ray film reveals a poor crown-to-root ratio for tooth #21 (right), the lower left first premolar. The tooth exhibits 50% bone loss, adding roughly 5-7 mm to the clinical crown of what is actually anatomical root. The fulcrum, existing somewhere immediately apical to the height of the bone, does not allow for any adjacent bone to avoid compression or tension, resulting in virtually complete widening of the PDL and a grim prognosis, due to secondary occlusal trauma.

Crown-to-root-ratio is the ratio of the length of the part of a tooth that appears above the alveolar bone versus what lies below it.[1] It is an important consideration in the diagnosis, treatment planning and restoration of teeth, one that hopefully guides the plan of treatment to the proper end result.

  1. ^ Page 114 in: Czochrowska, E.; Stenvik, A.; Bjercke, B.; Zachrisson, B. (2002). "Outcome of tooth transplantation: Survival and success rates 17-41 years posttreatment". American Journal of Orthodontics and Dentofacial Orthopedics. 121 (2): 110–119. doi:10.1067/mod.2002.119979. PMID 11840123. "Archived copy" (PDF). Archived from the original (PDF) on 2011-08-15. Retrieved 2010-08-16.{{cite web}}: CS1 maint: archived copy as title (link)