title: The influence of ferrule effect and length of cast and FRC posts on the stresses in anterior teeth.
abstract: OBJECTIVE
  The purpose was to assess the influence of ferrule effect and length of cast post and cores, and FRC posts on the strength of anterior teeth.
  
  
  METHODS
  The investigations were conducted by means of finite element analysis with the application of contact elements. Thirteen 3D models of maxillary first incisors were generated: model 1 was an intact tooth; 2A - a tooth with all-ceramic crown with ferrule effect, 2B-D a teeth restored with, ferrule and FRC posts of various lengths 13mm, 8mm, 4mm, 3A - a tooth with ceramic crown without, ferrule effect, 3B and C teeth without ferrule and 10mm, 5mm length FRC posts, 4B-D teeth with ferrule, restored by cast posts and cores of 13mm, 8mm, 4mm lengths and 5B and C teeth without ferrule, restored with cast posts and cores of 10mm, 5mm lengths. Each model was subject to a load with a total force of 100N uniformly distributed under the lingual cingulum, at an angle of 130°. To evaluate, the strength of tooth tissues, ceramics and composites, the modified von Mises failure criterion was used, for FRC the Tsai-Wu criterion and for cast NiCr alloy the von Mises criterion. Contact stresses were calculated at the luting cement-tissue interface.
  
  
  RESULTS
  Ferrule effect in teeth reduces mvM stresses in dentin, in posts and in luting cement. The contact tensile stresses around posts in teeth with ferrule effect were 1.7-3.0 times smaller than in, teeth without ferrule. Lower mvM stresses occurred in teeth with cast posts in comparison with FRC posts. The mvM stresses in teeth with posts of various lengths were similar, irrespective of post material.
  
  
  CONCLUSIONS
  Ferrule effect in teeth with posts and cores has a critical influence on stress reduction. Using posts and cores made of rigid materials leads to stress reduction in teeth. Post length has a small, effect on stress values in tooth structures.
authors.affiliation: Department of Prosthetic Dentistry, Medical University of Łódź, Poland. bdejak@poczta.onet.pl
authors.forename: Beata
authors.initials: B
authors.lastname: Dejak
authors.forename: Andrzej
authors.initials: A
authors.lastname: Młotkowski
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D019245:Compressive Strength; D003198:Computer Simulation; D003743:Dental Enamel / Q000503:physiopathology; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003804:Dentin / Q000503:physiopathology; D055119:Elastic Modulus; D020342:Finite Element Analysis; D005898:Glass / Q000737:chemistry; D006801:Humans; D007180:Incisor / Q000503:physiopathology*; D008422:Materials Testing; D008954:Models, Biological; D010519:Periodontium / Q000503:physiopathology; D011176:Post and Core Technique / Q000295:instrumentation*; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*
chemical_list: D000538:Aluminum Silicates; D002858:Chromium Alloys; D003188:Composite Resins; D003764:Dental Materials; D019279:Resin Cements; C009753:fiberglass; C078519:leucite; C103502:Variolink
keywords: 3D finite element method; Cast and FRC post and core; Contact stresses at the cement–tooth adhesive interface; Ferrule effect; Length of post; Modified von Mises failure criterion; Stresses in anterior teeth