page_title: Crown-to-root ratio
hierarchical_section_title: Crown-to-root ratio
caption_attribution_description: English: Periodontal bone loss shown in X-Ray image.
context_page_description: 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. 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.
context_section_description: 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. 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.
caption: 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.
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