title: The influence of various core designs on stress distribution in the veneered zirconia crown: a finite element analysis study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns.
  
  
  METHODS
  Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a 45° angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position.
  
  
  RESULTS
  In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased.
  
  
  CONCLUSIONS
  This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder.
authors.affiliation: Department of Dentistry, Ajou University School of Medicine, Suwon, Republic of Korea.
authors.forename: Seung-Ryong
authors.initials: SR
authors.lastname: Ha
authors.forename: Sung-Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Han
authors.forename: Seung-Hyun
authors.initials: SH
authors.lastname: Yoo
authors.forename: Se-Chul
authors.initials: SC
authors.lastname: Jeong
authors.forename: Jai-Bong
authors.initials: JB
authors.lastname: Lee
authors.forename: In-Sung
authors.initials: IS
authors.lastname: Yeo
keywords: Dental crowns; Dental prosthesis designs; Dental stress analyses; Finite element analyses; Zirconia