Clinical factors associated with ledged canals in maxillary and mandibular molars.

No clinical studies have been done to explore the relationship of ledging to the clinical practice of endodontics. The purpose of this study was to examine 171 cases completed by third-year dental students and to identify variables that were associated with ledging. A total of 336 canals were examined and tooth number, canal location, working length, the master apical file size, and root canal curvature were recorded. Of 336 canals, 46% were found to have been ledged. Analysis of variance revealed that No. 15 had a significantly higher incidence of ledging. Working lengths and master apical file sizes were not found to be significant variables. The main factor consistently related to the presence of ledges was canal curvature. The number of ledged canals increased significantly after 20 degrees and surpassed the number not ledged after 30 degrees. Multiple regression with the use of the five categories as the dependent variables and ledging as the independent variable resulted in an r = 0.397 and F = 12.216, p less than 0.0001. Curvature was found to have the highest significant t value (7.412) followed by "teeth" (2.471), whereas no other categories were identified as being significant. All the determinants for ledging were not identified with this study, and further research is indicated.