title: Fracture resistance of simulated immature tooth roots reinforced with MTA or restorative materials.
abstract: OBJECTIVE
  Immature endodontically treated teeth may require reinforcing to reduce the risk of root fracture. This study assessed the fracture resistance of simulated immature tooth roots reinforced with mineral trioxide aggregate (MTA) or two composite resin (CR) materials.
  
  
  METHODS
  One hundred extracted roots of mature human maxillary incisors were decoronated and sectioned 9 mm further apically from the decoronation line and randomly divided into five groups (n = 20). In Group 1 (negative control), roots received no treatment. In groups 2-5, canals were enlarged to 2.1 mm diameter to simulate immature roots, dressed with calcium hydroxide (Ca(OH)2 ) and incubated for 7 days. After removal of Ca(OH)2 , canals in Group 2 (positive control) were left unfilled. Canals in groups 3, 4 and 5 were filled with MTA, BisFil 2B flowable CR or BisFil II posterior CR, respectively. After further incubation for 30 days, specimens were embedded in acrylic cylinders and horizontally loaded in a universal testing machine at cross head speed of 5 mm min(-1) until fracture occurred. Load (N) at and pattern of fracture were recorded.
  
  
  RESULTS
  Load at fracture was significantly lower (t-test, P = 0.003) in Group 2 (630 ± 199.12) than in Group 1 (896.98 ± 311.79). It did not differ significantly among groups 1, 3, 4 and 5 (anova, P > 0.07). Pattern of fracture did not differ among the groups either.
  
  
  CONCLUSIONS
  Within the limitations of this study, root canal filling with MTA and two CR materials affected reinforcement of simulated immature roots to levels comparable with intact roots.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Yeditepe University, Istanbul, Turkey.
authors.forename: Meric
authors.initials: M
authors.lastname: Karapinar-Kazandag
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.
authors.forename: Bettina
authors.initials: B
authors.lastname: Basrani
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.
authors.forename: Valerie
authors.initials: V
authors.lastname: Tom-Kun Yamagishi
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.|Discipline of Dental Public Health, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.
authors.forename: Amir
authors.initials: A
authors.lastname: Azarpazhooh
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.
authors.forename: Shimon
authors.initials: S
authors.lastname: Friedman
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D002126:Calcium Hydroxide / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D004338:Drug Combinations; D006801:Humans; D066298:In Vitro Techniques; D007180:Incisor; D010087:Oxides / Q000737:chemistry*; D012387:Root Canal Filling Materials / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D014082:Tooth Fractures / Q000517:prevention & control*; D019553:Tooth, Nonvital
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D003188:Composite Resins; D004338:Drug Combinations; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate; C078905:Bisfil; D002126:Calcium Hydroxide
keywords: permanent tooth; root fracture; tooth injury