title: Morphology and microhardness of dentin at the furcation area of mandibular molars.
abstract: BACKGROUND
  This study evaluated dentin morphology and microhardness at the furcation area of mandibular molars.
  
  
  METHODS
  Tooth segments of mandibular molars were embedded in resin blocks and bisected longitudinally (n = 20), and the furcation area was delimited by tracing 2 orthogonal lines from the most concave point of the outer surface of the furcation toward the mesial and distal canal entrances. In half of the specimens, Knoop microhardness was measured in 2 directions in the furcation area: vertically, parallel to the orthogonal lines and the bisector of the angle formed by them; and horizontally, in the outer (close to the pulp chamber floor), inner (close to the cementum), and middle dentin layers. Data were analyzed statistically by one-way analysis of variance and Tukey-Kramer test (α = 0.05). The other half of the specimens were examined by scanning electron microscopy to evaluate dentin morphology and trajectory of the tubules.
  
  
  RESULTS
  No statistically significant difference (P > .05) was found among the mesial (46.5 ± 6.4), central (47.3 ± 8.1), and distal (49.7 ± 6.5) orthogonal lines. The inner dentin layer (51.7 ± 2.5) was statistically similar to the middle (46.3 ± 2.9) (P > .05), which was similar to the outer layer (41.4 ± 2.4) (P > .05). The inner layer was significantly harder than the outer layer (P < .05). The morphologic analysis revealed a tendency of calcification of the tubules from the outer toward the inner layer.
  
  
  CONCLUSIONS
  Dentin microhardness at the furcation area is uniform in its 3 vertical axes, but the inner dentin layer is harder than the outer layer. The dentinal tubules follow a centripetal direction toward the inner layer, in which dentin is much more mineralized.
authors: Department of Endodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil. Electronic address: cruz@forp.usp.br.
authors: Antonio M
authors: AM
authors: Cruz-Filho
authors: Department of Endodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors: Luis Eduardo
authors: LE
authors: Souza Flamini
authors: Department of Endodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors: Jesus Djalma
authors: JD
authors: Pécora
mesh_terms: D003739:Dental Cementum / Q000648:ultrastructure; D003786:Dental Pulp Cavity / Q000648:ultrastructure; D003804:Dentin / Q000648:ultrastructure*; D006244:Hardness; D006801:Humans; D008334:Mandible; D008855:Microscopy, Electron, Scanning; D008963:Molar / Q000648:ultrastructure*; D014092:Tooth Root / Q000648:ultrastructure*
keywords: Dentin; furcation area; mandibular molar; microhardness