title: Fatigue resistance and crack propensity of novel "super-closed" sandwich composite resin restorations in large MOD defects.
abstract: OBJECTIVE
  To assess the influence of conventional glass ionomer cement (GIC) vs resin-modified GIC (RMGIC) as a base material for novel, super-closed sandwich restorations (SCSR) and its effect on shrinkage-induced crack propensity and in vitro accelerated fatigue resistance.
  
  
  METHODS
  A standardized MOD slottype tooth preparation was applied to 30 extracted maxillary molars (5 mm depth/5 mm buccolingual width). A modified sandwich restoration was used, in which the enamel/dentin bonding agent was applied first (Optibond FL, Kerr), followed by a Ketac Molar (3M ESPE)(group KM, n = 15) or Fuji II LC (GC) (group FJ, n = 15) base, leaving 2 mm for composite resin material (Miris 2, Coltène-Whaledent). Shrinkageinduced enamel cracks were tracked with photography and transillumination. Samples were loaded until fracture or to a maximum of 185,000 cycles under isometric chewing (5 H z), starting with a load of 200 N (5,000 X), followed by stages of 400, 600, 800, 1,000, 1,200, and 1,400 N at a maximum of 30,000 X each. Groups were compared using the life table survival analysis (α = .008, Bonferroni method).
  
  
  RESULTS
  Group FJ showed the highest survival rate (40% intact specimens) but did not differ from group KM (20%) or traditional direct restorations (13%, previous data). SCSR generated less shrinkage-induced cracks. Most failures were re-restorable (above the cementoenamel junction [CEJ]).
  
  
  CONCLUSIONS
  Inclusion of GIC/RMGIC bases under large direct SCSRs does not affect their fatigue strength but tends to decrease the shrinkage-induced crack propensity.
  
  
  CONCLUSIONS
  The use of GIC/ RMGIC bases and the SCSR is an easy way to minimize polymerization shrinkage stress in large MOD defects without weakening the restoration.
authors.forename: Pascal
authors.initials: P
authors.lastname: Magne
authors.forename: Silvana
authors.initials: S
authors.lastname: Silva
authors.forename: Mauro de
authors.initials: Md
authors.lastname: Andrada
authors.forename: Hamilton
authors.initials: H
authors.lastname: Maia
mesh_terms: D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation / Q000145:classification; D003743:Dental Enamel / Q000293:injuries / Q000648:ultrastructure; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000145:classification* / Q000379:methods; D003804:Dentin / Q000648:ultrastructure; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D015993:Life Tables; D055115:Light-Curing of Dental Adhesives / Q000379:methods; D008422:Materials Testing; D055595:Mechanical Phenomena; D010781:Photography / Q000379:methods; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D016019:Survival Analysis; D014172:Transillumination / Q000379:methods
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; C000602431:Miris 2; C469607:OptiBond FL; D019279:Resin Cements; D012117:Resins, Synthetic; C110712:ketac-molar