title: Assessment of the resistance to fracture of endodontically treated molars restored with amalgam.
abstract: BACKGROUND
  Controversy exists concerning the preferred type of final restoration of endodontically treated molars regarding their resistance to fracture under occlusal load.
  
  
  OBJECTIVE
  The aim of this study was to assess the resistance to fracture of endodontically treated molars with various degrees of tooth structure loss restored with amalgam under simulated occlusal load.
  
  
  METHODS
  . The study teeth consisted of 90 noncarious, nonrestored molars stored in physiological saline solution. The teeth were endodontically treated and randomly divided into 9 experimental groups of 10 specimens each with various degrees of tooth loss, ranging from a conservative endodontic access to removal of all cusps. All teeth were restored with a standardized technique to their original contour with amalgam. Each specimen was mounted onto a specialized jig for loading at the central fossa at a 30-degree angle to the long tooth axis. The resistance to fracture, under continuous compressive force at a cross-head speed of 2 mm/minute, was applied by a universal testing machine and was recorded. One-way analysis of variance with Scheffé contrast was used to statistically compare the differences between the groups at significance level P<.05.
  
  
  RESULTS
  One-way analysis of variance showed that the group with a conservative endodontic access (1137.6 +/- 311.6 N) and the group with removal of all cusps (1261.4 +/- 195.1 N) presented a significantly higher resistance to fracture when compared with the other groups (P<.05). There was no significant difference in resistance to fracture under the simulated load between the other 7 groups, which ranged from 655.8 +/- 229.4 to 906.3 +/- 168.1 N (P>.05).
  
  
  CONCLUSIONS
  Within the limitations of this study, the endodontically treated molars with a conservative endodontic access or after removal of all cusps that were restored to their original contour with amalgam presented the highest resistance to fracture under a simulated occlusal load.
authors.affiliation: Department of Oral Rehabilitation, The Maurice and Gabriela Goldshleger School of Dental Medicine, Tel Aviv University, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Assif
authors.forename: Joseph
authors.initials: J
authors.lastname: Nissan
authors.forename: Yaron
authors.initials: Y
authors.lastname: Gafni
authors.forename: Moshe
authors.initials: M
authors.lastname: Gordon
mesh_terms: D000704:Analysis of Variance; D001732:Bite Force; D003723:Dental Amalgam / Q000737:chemistry; D003737:Dental Cavity Preparation / Q000145:classification; D003793:Dental Restoration, Permanent / Q000145:classification / Q000379:methods*; D006801:Humans; D008963:Molar / Q000503:physiopathology*; D018915:Root Canal Preparation / Q000379:methods; D012390:Root Canal Therapy; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000503:physiopathology*; D019553:Tooth, Nonvital / Q000503:physiopathology / Q000628:therapy*
chemical_list: D003723:Dental Amalgam