Topographic study of root trunk type on Chinese molars with Class III furcation involvements: molar type and...

This study investigated the relationship between root trunk length and prognosis for molars with furcation involvement. Molars with furcation involvement were obtained from 169 patients affected with periodontitis. The test group consisted of 174 hopeless molars screened from a total of 441 molars with Class III involvement; the remaining 267 molars formed the control group. Both arches showed a significantly higher missing rate for teeth with a long root trunk length (type C) in second molars (41.3% and 32.4% in the maxilla and mandible, respectively), with a high degree of Class III furcation involvement for the test group (extracted hopeless or poor prognosis), compared to first molars (9.9% and 0.9% in the maxilla and mandible, respectively). Both arches had a significantly higher prevalence of long root trunk lengths in the second molars compared to first molars, irrespective of furcation site. Although first molars had an early and higher prevalence of Class III furcation involvement than second molars, the latter reached a significantly higher missing rate. Molars with longer root trunk lengths had a higher risk for poor prognosis than shorter root trunks when teeth were affected by Class III furcation involvement. For extracted furcation-involved maxillary second molars that failed to respond to periodontal therapy, long root trunk length (C) accounted for the greatest prevalence at the mesial furcation site (41.8%), followed by the distal (33.0%) and buccal sites (25.2%); the greatest prevalence of root trunk length C was found at the lingual (47.9%) and buccal furcation sites (45.1%) of mandibular second molars. When a molar with root trunk type C has a Class III involvement, the prognosis is poor; for the disease to reach that level, greater amounts of attachment must be destroyed.