The prosthodontic concept of crown-to-root ratio: a review of the literature.

Crown-to-root ratio is intended to serve as an aid in predicting the prognosis of teeth. However, controversy persists as to its impact on diagnosis and treatment planning. This article critically reviews the available literature on the crown-to-root ratio assessment and criteria for evaluation of abutment use of periodontally compromised teeth. A Medline search was completed for the time period from 1966 to 2003, along with a manual search, to locate relevant peer-reviewed articles and textbooks published in English. Key words used were "crown-to-root ratio," "periodontal compromised dentition," "mobility," and "biomechanics." There was a dearth of evidence-based research on the topic. Although the use of the crown-to-root ratio in addition to other clinical indices may offer the best clinical predictors, no definitive recommendations could be ascertained.