title: In vitro fracture strength of teeth restored with different all-ceramic crown systems.
abstract: BACKGROUND
  There is insufficient knowledge of the strength of all-ceramic crowns bonded to natural teeth to warrant the use of all-ceramic crowns in place of metal-ceramic crowns.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate and compare fracture resistance of crowns made of 3 different types of 2 all-ceramic crown systems-0.4-mm and 0.6-mm aluminum oxide coping crowns and zirconia ceramic coping crowns-and metal-ceramic crowns.
  
  
  METHODS
  Forty intact, noncarious human maxillary central incisors were divided into 4 groups (n=10): Group MCC (control), metal-ceramic crown (JRVT High Noble Alloy); Group AC4, crown with 0.4-mm aluminum oxide coping (Procera AllCeram); Group AC6, crown with 0.6-mm aluminum oxide coping (Procera AllCeram); and Group ZC6, crown with 0.6-mm zirconia ceramic coping (Procera AllZirkon). Teeth were prepared for complete-coverage all-ceramic crowns so that a final dimension of 5.5 +/- 0.5 mm was achieved incisocervically, mesiodistally, and faciolingually. A 1.0-mm deep shoulder finish line was used with a rounded internal line angle. All restorations were treated with bonding agent (Clearfil SE Bond) and luted with phosphate-monomer-modified adhesive cement (Panavia 21). Fracture strength was tested with a universal testing machine at a crosshead speed of 2 mm per minute with an angle of 30 degrees to the long axis of the tooth after restorations were stored in 100% relative humidity of a normal saline solution for 7 days. The mode of fracture was examined visually. Means were calculated and analyzed with 1-way ANOVA and Tukey's HSD (alpha=.05).
  
  
  RESULTS
  The means of fracture strength were: Group MCC, 405 +/- 130 N; Group AC4, 447 +/- 123 N; Group AC6, 476 +/- 174 N; and Group ZC6, 381 +/- 166 N. There was no significant difference between groups ( P =.501). The mode of failure for all specimens was fracture of the natural tooth.
  
  
  CONCLUSIONS
  There was no significant difference in the fracture strength of the teeth restored with all-ceramic crowns with 0.4- and 0.6-mm aluminum oxide copings, 0.6-mm zirconia ceramic copings, and metal ceramic crowns.
authors.affiliation: School of Dentistry, Louisiana State University Health Sciences Center, 1100 Florida Avenue, New Orleans, LA 70119, USA. npotik@lsuhsc.edu
authors.forename: Narong
authors.initials: N
authors.lastname: Potiket
authors.forename: Gerard
authors.initials: G
authors.lastname: Chiche
authors.forename: Israel M
authors.initials: IM
authors.lastname: Finger
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002484:Cementation; D002516:Ceramics / Q000737:chemistry*; D003442:Crowns; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D007180:Incisor; D016876:Metal Ceramic Alloys / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000503:physiopathology* / Q000517:prevention & control; D019231:Tooth Preparation, Prosthodontic; D015040:Zirconium / Q000737:chemistry
chemical_list: C105314:AllCeram; C438313:Clearfil SE Bond; D003764:Dental Materials; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; C093719:Panavia TPN-S; D010710:Phosphates; D019279:Resin Cements; D003776:Dental Porcelain; D010984:Platinum; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide