title: Morphological evaluation of maxillary second molars with fused roots: a micro-CT study.
abstract: OBJECTIVE
  To evaluate the internal and external morphologies of fused-rooted maxillary second molars by means of micro-computed tomography (micro-CT) analysis.
  
  
  METHODS
  A total of 100 fused-rooted maxillary second molars from a Brazilian subpopulation were divided into six groups according to the root morphology. The samples were scanned at a resolution of 19.6 μm and evaluated with regard to the external morphology of the roots, the root canal configuration, the percentage frequency of C-shaped canals and isthmuses, as well as the morphology of the root canal system at 1, 2 and 3 mm from the anatomical apex of the fused roots.
  
  
  RESULTS
  The most prevalent root canal fusions were type 1, mesiobuccal root fused with distobuccal root (32%), followed by type 3, DB root fused with P root (27%), and type 4, MB root fused with DB root, and P root fused with MB or DB roots (21%). The prevalence of C-shaped root canal systems were 22%. Depending on the type of root fusion, the percentage frequency of isthmuses in the apical level varied from 9.3% to 42.8%, whilst the presence of apical deltas ranged from 18.5% to 57.1% of teeth.
  
  
  CONCLUSIONS
  The root canal system of maxillary second molars with fused roots may have a high incidence of merging canals, isthmuses, apical deltas and C-shaped configurations.
authors.affiliation: Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, Brazil.|Bender Division of Endodontics, Albert Einstein Medical Center, Philadelphia, PA, USA.
authors.forename: R
authors.identifier: http://orcid.org/0000-0001-9738-0828
authors.initials: R
authors.lastname: Ordinola-Zapata
authors.affiliation: Department of Endodontics, Faculdade de Medicina Dentária da Universidade de Lisboa, Lisboa, Portugal.
authors.forename: J N R
authors.identifier: http://orcid.org/0000-0002-6932-2038
authors.initials: JNR
authors.lastname: Martins
authors.affiliation: Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, Brazil.
authors.forename: C M
authors.initials: CM
authors.lastname: Bramante
authors.affiliation: Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, Brazil.
authors.forename: M H
authors.initials: MH
authors.lastname: Villas-Boas
authors.affiliation: Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, Brazil.
authors.forename: M H
authors.initials: MH
authors.lastname: Duarte
authors.affiliation: Department of Restorative Dentistry, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: M A
authors.initials: MA
authors.lastname: Versiani
mesh_terms: D006801:Humans; D021621:Imaging, Three-Dimensional; D008437:Maxilla; D008963:Molar / Q000002:abnormalities* / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014092:Tooth Root / Q000002:abnormalities* / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D055114:X-Ray Microtomography
keywords: dental anatomy; fused roots; maxillary molars; micro-computed tomography