title: Effectiveness and dentin bond strengths of two materials for reinforcing thin-walled roots.
abstract: OBJECTIVE
  To investigate the effectiveness of two restorative materials for reinforcing thin-walled roots and their microtensile bond strengths to root canal dentin.
  
  
  METHODS
  Twenty-one decoronated maxillary central incisor roots were root filled and the canals enlarged to leave approximately 1.0 mm thick dentin walls. The roots were distributed randomly to three equal groups. Group 1 (control): a large tapered cast post-core was fabricated. Group 2 (BIS-CORE): a thick layer of dual-cured composite was placed in the post-hole before fabrication of a small-diameter tapered cast post-core. Group 3 (ChemFil Superior): a thick layer of glass-ionomer was placed, as before. Metal-ceramic crowns were fabricated for all teeth. Microtensile bond strength tests and optical and atomic force microscope observations were employed to examine adhesion between the two restorative materials and the root canal dentin.
  
  
  RESULTS
  Mechanical loading (kN) demonstrated that composite 0.64 (S.D. 0.05), but not glass-ionomer 0.49 (0.05), significantly reinforced the fracture resistance of thin-walled roots, P<0.001. Microtensile bond strengths (MPa) were 21.7 (1.6) for composite and 12.9 (1.7) for glass-ionomer, P=002.
  
  
  CONCLUSIONS
  A thick intermediate layer of resin-bonded composite, sandwiched between the root dentin and a small-diameter cast Ni-Cr post or dowel, increased significantly the fracture resistance of the roots.
authors.affiliation: Department of Prosthetic Dentistry, College of Stomatology, Nanjing Medical University, Nanjing, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wu
authors.forename: Anna T T
authors.initials: AT
authors.lastname: Chan
authors.forename: Ya-Ming
authors.initials: YM
authors.lastname: Chen
authors.forename: Kevin H-K
authors.initials: KH
authors.lastname: Yip
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Smales
mesh_terms: D000328:Adult; D003188:Composite Resins; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents; D005899:Glass Ionomer Cements; D006801:Humans; D007180:Incisor; D008297:Male; D018625:Microscopy, Atomic Force; D011176:Post and Core Technique / Q000009:adverse effects; D013718:Tensile Strength; D014082:Tooth Fractures / Q000209:etiology / Q000517:prevention & control*; D014092:Tooth Root / Q000502:physiology
chemical_list: C520518:BIS-Core Resin-bonded Composite; C501420:Chemfil Superior; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D005899:Glass Ionomer Cements