title: Fracture behavior of structurally compromised non-vital maxillary premolars restored using experimental fiber reinforced composite crowns.
abstract: OBJECTIVE
  To study the fracture behavior of direct resin composite crowns with or without experimental fiber reinforcement.
  
  
  METHODS
  Clinical crowns of single-rooted maxillary premolars were cut off at the cemento-enamel junction. Canals were prepared with Gates Glidden drills up to size 4. No additional post-space preparations were made. Roots were embedded in acrylic and canal entrances were standardized (depth 2 mm, diameter 1.75 mm). Three groups of 14 samples were treated as follows: (1) custom-made glass FRC post (EverStick Post); fibers 5 mm deep in the canal, (2) similar post-system as (1) with incorporation of a new type of glass fiber fabric, (3) no fiber reinforcement (control). Posts were cemented with resin cement (Panavia F). Resin composite crowns (Filtek Z250) were made using an anatomically formed mold. Static load until fracture was applied using a universal loading device with a cylindrical bar (diameter 2 mm) with a crosshead speed of 5 mm/minute (loading angle: 30 degrees to the tooth long-axis). Failure modes were categorized as favorable and unfavorable failures.
  
  
  RESULTS
  There was no significant difference in mean failure loads among the four groups (P > 0.05). Favorable failures occurred significantly more often in Group 2 than in the other groups (P < 0.05). The results suggest that an incorporated glass fiber fabric does not affect the load-bearing capacity of resin composite complete crowns on structurally compromised and non-vital premolars. Incorporation of a glass fiber fabric, however, has a beneficial effect on the failure mode.
authors.affiliation: College of Dental Science, Department of Oral Function and Prosthetic Dentistry, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. w.fokkinga@dent.umcn.nl
authors.forename: Wietske A
authors.initials: WA
authors.lastname: Fokkinga
authors.forename: Cees M
authors.initials: CM
authors.lastname: Kreulen
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Le Bell-Rönnlöf
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
authors.forename: Nico H J
authors.initials: NH
authors.lastname: Creugers
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid / Q000293:injuries*; D016009:Chi-Square Distribution; D003188:Composite Resins / Q000737:chemistry*; D003442:Crowns; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D005898:Glass; D006801:Humans; D008422:Materials Testing; D011176:Post and Core Technique; D033081:Shear Strength; D014082:Tooth Fractures / Q000517:prevention & control*; D019553:Tooth, Nonvital / Q000503:physiopathology*
chemical_list: D003188:Composite Resins; C009753:fiberglass