title: A novel coping design to decrease maximum principal stress in zirconia ceramic restorations.
abstract: OBJECTIVE
  The objective of this study was to evaluate the influence of coping design modifications on maximum first principal stress (MPS) in a mathematical zirconia ceramic crown model.
  
  
  METHODS
  For a nonlinear, 3D finite element analysis, a simplified tooth model was built on the basis of the average dimensions of mandibular second molars. Virtual tooth reduction was performed to model an abutment with a flat occlusal surface and 16° convergence angle between facing walls. The cement layer was set to a thickness of 100 μm. Three different copings-one with 0.5-mm constant thickness; one with constant thickness and extended lingual and proximal collars; and a novel design with zirconia beam reinforcement-were designed to simulate zirconia ceramic restorations. The novel design had strategically positioned zirconia beams on the lingual and marginal ridges to protect veneer ceramics, and was divided into three subdesigns according to the width of the zirconia beam (0.5, 0.8, and 1 mm). Combinations of vertical and horizontal load were applied over the distolingual marginal ridge, and the MPSs were evaluated.
  
  
  RESULTS
  The novel design showed the lowest MPS in veneer ceramics under most loading conditions. The only exception to this was the novel design with a 0.5-mm zirconia beam width under mesial horizontal load.
  
  
  CONCLUSIONS
  Compared to constant thickness coping with or without extended collars, the novel coping design reduced MPS in veneer ceramics; however, narrow zirconia beams should be avoided to prevent elevations in MPS in veneer ceramic layers.
authors.affiliation: Private Practice, Dental Office Drs. Sung & Oh, Seoul, Korea.
authors.forename: MooGyung
authors.initials: M
authors.lastname: Sung
authors.forename: Chong-Hyun
authors.initials: CH
authors.lastname: Han
authors.forename: Sunjai
authors.initials: S
authors.lastname: Kim
mesh_terms: D001732:Bite Force; D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003801:Dental Veneers; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008422:Materials Testing; D017711:Nonlinear Dynamics; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014584:User-Computer Interface; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; D019279:Resin Cements; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium
keywords: Zirconia; coping; design; finite element analysis; stress