title: Effect of remaining coronal structure on the resistance to fracture of crowned endodontically treated maxillary first premolars.
abstract: OBJECTIVE
  Endodontically treated maxillary first premolars present a restorative challenge. The objective of the present study was to assess the resistance to fracture of crowned endodontically treated maxillary first premolars under simulated occlusal load, while preserving various degrees of remaining coronal structure.
  
  
  METHODS
  The study consisted of 50 intact maxillary first premolars with bifurcated roots and similar root diameter and length, randomly divided into 5 equal experimental groups. All dowels were luted with Flexi-Flow titanium-reinforced composite resin cement. TiCore titanium-reinforced composite resin was used to fabricate the core. Complete cast crowns were fabricated and cemented with zinc phosphate cement. Forces at fracture and mode of failure were recorded.
  
  
  RESULTS
  Statistically significant differences (P < .05) were found among mean failure forces for all tested groups in their resistance to fracture under load with the Kruskal-Wallias test and among all combinations of the 5 groups (Z = -1.56/-2.34; P > .05) with the Mann-Whitney test. This indicates that crowned maxillary first premolars with varying degrees of remaining coronal structure differ significantly in their resistance to fracture under occlusal load. There was increased protection against fracture under occlusal loads with more remaining tooth structure.
  
  
  CONCLUSIONS
  Within the limitations of this study, remaining coronal structure influenced the fracture resistance of crowned endodontically treated maxillary first premolars. Preservation of tooth structure is important for its protection against fracture under occlusal loads and may influence the tooth prognosis.
authors.affiliation: Department of Oral Rehabilitation, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Israel.
authors.forename: Joseph
authors.initials: J
authors.lastname: Nissan
authors.forename: Eitan
authors.initials: E
authors.lastname: Barnea
authors.forename: Doron
authors.initials: D
authors.lastname: Bar Hen
authors.forename: David
authors.initials: D
authors.lastname: Assif
mesh_terms: D001641:Bicuspid; D003188:Composite Resins; D003442:Crowns; D003738:Dental Cements; D003799:Dental Stress Analysis; D006801:Humans; D008437:Maxilla; D019279:Resin Cements; D014025:Titanium; D019228:Tooth Crown / Q000502:physiology*; D014082:Tooth Fractures / Q000209:etiology*; D019231:Tooth Preparation, Prosthodontic / Q000009:adverse effects*; D019553:Tooth, Nonvital
chemical_list: D003188:Composite Resins; D003738:Dental Cements; C101035:Flexi-Flow cement; D019279:Resin Cements; D014025:Titanium