title: Fracture resistance of monolithic zirconia molar crowns with reduced thickness.
abstract: OBJECTIVE
  The purpose of the present study was to analyze the relationship between fracture load of monolithic zirconia crowns and axial/occlusal thickness and to evaluate the fracture resistance of monolithic zirconia crowns with reduced thickness in comparison with that of monolithic lithium disilicate crowns with regular thickness.
  
  
  METHODS
  Monolithic zirconia crowns (Lava Plus Zirconia, 3M/ESPE) with specified axial/occlusal thicknesses and lithium disilicate crowns (IPS e.max press, Ivoclar/Vivadent) with regular thickness were fabricated using a dental CAD/CAM system and a press technique, respectively. The crowns cemented onto dies were loaded until fracture. Based on measurements of the crown thickness made by micro-CT and the fracture load, multiple regression analysis was performed.
  
  
  RESULTS
  It was revealed that the occlusal thickness significantly affected the fracture load (p < 0.01), but the axial thickness did not (p = 0.2828). Although the reduction of the occlusal thickness decreased the fracture resistance of the monolithic zirconia crowns, the fracture load of the zirconia crowns with the occlusal thickness of 0.5 mm (5558 ± 522 N) was significantly higher than that of lithium disilicate crowns with an occlusal thickness of 1.5 mm (3147 ± 409 N).
  
  
  CONCLUSIONS
  Within the limitations of the present study, it is suggested that monolithic zirconia crown with chamfer width of 0.5 mm and occlusal thickness of 0.5 mm can be used in the molar region in terms of fracture resistance.
authors: Department of Prosthetic Dentistry/Dental Materials Science, Institute of Odontology, University of Gothenburg , Gothenburg , Sweden.
authors: Keisuke
authors: K
authors: Nakamura
authors: Akio
authors: A
authors: Harada
authors: Ryoichi
authors: R
authors: Inagaki
authors: Taro
authors: T
authors: Kanno
authors: Yoshimi
authors: Y
authors: Niwano
authors: Percy
authors: P
authors: Milleding
authors: Ulf
authors: U
authors: Örtengren
mesh_terms: D017076:Computer-Aided Design; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods; D055119:Elastic Modulus; D006801:Humans; D008422:Materials Testing; D008963:Molar / Q000033:anatomy & histology; D018583:Pliability; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D055114:X-Ray Microtomography / Q000379:methods; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; C508050:IPS e.max Press; D019279:Resin Cements; C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: X-ray microtomography; computer-aided design; lithium disilicate; zirconium oxide