title: Effect of remaining tooth structure on the fracture resistance of endodontically-treated maxillary premolars: An in vitro study.
abstract: BACKGROUND
  Assessing the quantity and distribution of residual coronal dentin is important in deciding the restorability of endodontically treated teeth.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to investigate the relationship between the cross-sectional area and location of remaining coronal tooth structure and the fracture resistance of restored teeth after endodontic treatment.
  
  
  METHODS
  Fifty-five extracted maxillary premolars received endodontic treatment and crown preparations. The teeth were assigned to 11 groups of 5 teeth according to the number and the location of missing axial walls. Impressions of the prepared teeth were made to fabricate dies. Each die was sectioned 1 mm above the finish line, and the dentin surface area was measured. All teeth were restored with composite resin cores and cast metal crowns. The specimens were thermocycled between 5°C and 55°C for 500 cycles before loading until failure with a universal testing machine. The results were analyzed with 1-way ANOVA and post hoc comparisons.
  
  
  RESULTS
  Specimens with all axial walls intact around the access cavity had the highest mean fracture strength (1380.5 ±393.9 N). Groups with the palatal and 1 or 2 proximal walls missing showed the lowest mean failure loads (398.4 N ±149.5 N and 344.7 N ±91.2 N). The correlation between the surface area and the fracture resistance was 0.72 CONCLUSIONS: For restored endodontically treated maxillary premolars, a positive linear relationship was found between the remaining coronal dentin surface area and fracture strength. Residual dentin location influences fracture resistance.
authors.affiliation: Lecturer, Department of Conservative Dentistry, School of Dentistry, University of Adelaide, SA, Australia. Electronic address: amal.ibrahim@adelaide.edu.au.
authors.forename: Amal Mamdouh B R
authors.initials: AM
authors.lastname: Ibrahim
authors.affiliation: Professor, School of Dentistry, University of Adelaide, SA, Australia.
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Richards
authors.affiliation: Clinical Senior Lecturer, School of Dentistry, University of Adelaide, SA, Australia.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Berekally
mesh_terms: D001641:Bicuspid; D003188:Composite Resins; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D011176:Post and Core Technique; D019228:Tooth Crown / Q000033:anatomy & histology*; D014082:Tooth Fractures / Q000517:prevention & control*; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*; D019553:Tooth, Nonvital
chemical_list: D003188:Composite Resins