title: Ex vivo fracture resistance of direct resin composite complete crowns with and without posts on maxillary premolars.
abstract: OBJECTIVE
  To investigate ex vivo the fracture resistance and failure mode of direct resin composite complete crowns with and without various root canal posts made on maxillary premolars.
  
  
  METHODS
  The clinical crowns of 40 human extracted single-rooted maxillary premolars were sectioned at the cemento-enamel junction. The canals were prepared with Gates Glidden drills up to size 4. Thirty samples were provided with standardized post spaces in the palatal canal and all roots were embedded in acrylic. Minimal standardized preparations in the canal entrances were made. Groups of 10 samples were treated with (i) prefabricated metal posts, (ii) prefabricated glass fibre posts, (iii) custom-made glass fibre posts, and (iv) no posts (control). Posts were cemented with resin cement and resin composite complete crowns were made. All specimens were thermocycled (6000x, 5-55 degrees C). Static load until fracture was applied using a universal loading device (crosshead speed 5 mm min(-1)) at a loading angle of 30 degrees . Failure modes were categorized as favourable and unfavourable failures.
  
  
  RESULTS
  No significant difference was observed between the mean failure loads (group 1: 1386 N, group 2: 1276 N, group 3: 1281 N, and group 4: 1717 N, P > 0.05), nor between frequencies of failure modes (P > 0.05). All failures were fractures of the resin composite crown in combination with tooth material (cohesive failures).
  
  
  CONCLUSIONS
  Within the limits of this laboratory investigation it is concluded that severely damaged and root filled maxillary premolars, restored with direct resin composite complete crowns without posts have similar fracture resistances and failure modes compared to those with various posts, which suggest that posts are not necessarily required.
authors.affiliation: Department of Oral Function and Prosthetic Dentistry, College of Dental Science, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. w.fokkinga@dent.umcn.nl
authors.forename: W A
authors.initials: WA
authors.lastname: Fokkinga
authors.forename: A-M
authors.initials: AM
authors.lastname: Le Bell
authors.forename: C M
authors.initials: CM
authors.lastname: Kreulen
authors.forename: L V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: P K
authors.initials: PK
authors.lastname: Vallittu
authors.forename: N H J
authors.initials: NH
authors.lastname: Creugers
mesh_terms: D001641:Bicuspid; D016009:Chi-Square Distribution; D003188:Composite Resins; D003442:Crowns; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D005898:Glass; D006801:Humans; D008422:Materials Testing; D008437:Maxilla; D008670:Metals; D011176:Post and Core Technique; D019553:Tooth, Nonvital
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D008670:Metals; C009753:fiberglass