title: Fracture resistance and stress distribution of simulated immature teeth after apexification with mineral trioxide aggregate.
abstract: OBJECTIVE
  To evaluate the effect of adhesive restorations on fracture resistance and stress distribution in teeth with simulated immature apices and apical plugs of mineral trioxide aggregate (MTA).
  
  
  METHODS
  Sixty bovine incisors were sectioned 8 mm above and 12 mm below the cemento-enamel junction (CEJ). The root canal was enlarged using a diamond bur, resulting in remaining root canal walls with 0.1-0.2 mm of thickness. A 5-mm apical plug of MTA was placed and the teeth were restored according to the following groups: GP--the root canal was filled with gutta-percha and endodontic sealer; CR--the root canal was filled with light-cured composite resin inserted incrementally; FP--a fibre post was cemented into the root canal; and RFP--the fibre post was relined with composite resin prior to the cementation into the root canal. A load was applied on the crown of all teeth at 135° to their long axis until fracture. Data was analysed by one-way anova and SNK tests (α = 0.05), whilst the fracture pattern was evaluated according to the position of the fracture. Stress distributions in the restored teeth were verified by finite element analysis.
  
  
  RESULTS
  Teeth restored with fibre posts and relined fibre posts were associated with the highest fracture resistance, whilst the GP group had the lowest values. GP and RC groups had similar fracture resistance values (P = 0.109). All fractures types involved the cervical and middle thirds of roots. The GP model had high levels of stress concentration in the cervical and middle thirds of roots. No difference was found amongst the stress concentration in the RC, FP and RFP models.
  
  
  CONCLUSIONS
  Restorative protocols alter the fracture resistance and stress distribution of immature teeth after placement of MTA apical plugs.
authors.affiliation: Interinstitutional PhD program, State University of Montes Claros, Montes Claros, Brazil; Department of Restorative Dentistry, Faculty of Dentistry, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Brito-Júnior
authors.forename: R D
authors.initials: RD
authors.lastname: Pereira
authors.forename: C
authors.initials: C
authors.lastname: Veríssimo
authors.forename: C J
authors.initials: CJ
authors.lastname: Soares
authors.forename: A L
authors.initials: AL
authors.lastname: Faria-e-Silva
authors.forename: C C
authors.initials: CC
authors.lastname: Camilo
authors.forename: M D
authors.initials: MD
authors.lastname: Sousa-Neto
mesh_terms: D017607:Aluminum Compounds; D000818:Animals; D017610:Calcium Compounds; D002417:Cattle; D004338:Drug Combinations; D020342:Finite Element Analysis; D010087:Oxides; D017640:Silicates; D013314:Stress, Mechanical; D019227:Tooth Apex / Q000473:pathology*; D014082:Tooth Fractures
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D017640:Silicates; C086631:mineral trioxide aggregate
keywords: apexification; dental restoration, permanent; mineral trioxide aggregate; post and core technique; tooth fracture