title: Adaptation of adhesive post and cores to dentin after in vitro occlusal loading: evaluation of post material influence.
abstract: OBJECTIVE
  Fatigue resistance of post and cores is critical to the long term behavior of restored nonvital teeth. The purpose of this in vitro trial was to evaluate the influence of the post material's physical properties on the adaptation of adhesive post and core restorations after cyclic mechanical loading.
  
  
  METHODS
  Composite post and cores were made on endodontically treated deciduous bovine teeth using 3 anisotropic posts (made of carbon, quartz, or quartz-and-carbon fibers) and 3 isotropic posts (zirconium, stainless steel, titanium). Specimens were submitted to 3 successive loading phases--250,000 cycles at 50 N, 250,000 at 75 N, and 500,000 at 100 N--at a rate of 1.5 Hz. Restoration adaptation was evaluated under SEM, before and during loading (margins) and after test completion (margins and internal interfaces). Six additional samples were fabricated for the characterization of interface micromorphology using confocal microscopy.
  
  
  RESULTS
  Mechanical loading increased the proportion of marginal gaps in all groups; carbon fiber posts presented the lowest final gap proportion (7.11%) compared to other stiffer metal-ceramic or softer fiber posts (11.0% to 19.1%). For internal adaptation, proportions of debonding between dentin and core or cement varied from 21.69% (carbon post) to 47.37% (stainless steel post). Debonding at the post-cement interface occurred only with isotropic materials. Confocal microscopy observation revealed that gaps were generally associated with an incomplete hybrid layer and reduced resin tags.
  
  
  CONCLUSIONS
  Regardless of their rigidity, metal and ceramic isotropic posts proved less effective than fiber posts at stabilizing the post and core structure in the absence of the ferrule effect, due to the development of more interfacial defects with either composite or dentin.
authors.affiliation: Department of Cariology and Endodontics, School of Dentistry, University of Geneva, Switzerland. dider.dietschi@medecine.unige.ch
authors.forename: Dider
authors.initials: D
authors.lastname: Dietschi
authors.forename: Stefano
authors.initials: S
authors.lastname: Ardu
authors.forename: Anne
authors.initials: A
authors.lastname: Rossier-Gerber
authors.forename: Ivo
authors.initials: I
authors.lastname: Krejci
mesh_terms: D000134:Acid Etching, Dental; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D001732:Bite Force; D002244:Carbon / Q000737:chemistry; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000648:ultrastructure; D003804:Dentin / Q000648:ultrastructure*; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011176:Post and Core Technique / Q000295:instrumentation*; D011791:Quartz / Q000737:chemistry; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013193:Stainless Steel / Q000737:chemistry; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D014094:Tooth, Deciduous / Q000648:ultrastructure; D019553:Tooth, Nonvital / Q000473:pathology; D015040:Zirconium / Q000737:chemistry
chemical_list: C098721:Aelitefil; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D019279:Resin Cements; D012821:Silanes; D013193:Stainless Steel; D011791:Quartz; C100742:All-Bond 2; D017438:Bisphenol A-Glycidyl Methacrylate; D002244:Carbon; D012822:Silicon Dioxide; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide