title: Biomechanical evaluation of platform switching: different mismatch sizes, connection types, and implant protocols.
abstract: BACKGROUND
  It is not yet well understood to what extent different implant-abutment mismatch sizes and implant-abutment connection types may influence the peri-implant biomechanical environment of implants in different clinical situations.
  
  
  METHODS
  Computed tomography-based finite element models comprising a maxillary central incisor socket and 4.5 × 13 mm outer-diameter implants with external and internal hex connection types were constructed. The abutments were designed with diameters of 3.5 mm (platform switching [PS] with 1 mm of diametral mismatch [PS - 1]), 4.0 mm (PS with 0.5 mm of diametral mismatch [PS - 0.5]), and 4.5 mm (conventional matching implant-abutment design [CD]). Analysis of variance at the 95% confidence interval was used to evaluate peak equivalent strain (EQV strain) in the bone, bone volume affected by a strain >4,000 με (EQV strain >4,000 με), the peak von Mises stress (EQV stress) in abutment screw, and the bone-implant relative displacement.
  
  
  RESULTS
  Similar bone strain levels (EQV strain and EQV strain >4,000 με) were encountered in PS - 1, PS - 0.5, and CD models for immediately placed implants, independent of the connection type. For immediately loaded implants, slightly smaller peak EQV strain and EQV strain >4,000 με were found for PS - 1. However, for both connection types in osseointegrated models, the higher the mismatch size, the lesser the amount of strain found.
  
  
  CONCLUSIONS
  The increase in mismatch size of PS configuration results in a significant decrease of strain levels in bone for osseointegrated implants, principally for external hex connections. No significant effect of PS could be noted in immediately placed implants.
authors.affiliation: Faculty of Odontology, Federal University of Uberlandia, Uberlandia, Brazil.
authors.forename: Roberto S
authors.initials: RS
authors.lastname: Pessoa
authors.forename: Fábio J B
authors.initials: FJ
authors.lastname: Bezerra
authors.forename: Ravel M
authors.initials: RM
authors.lastname: Sousa
authors.forename: Jos
authors.initials: J
authors.lastname: Vander Sloten
authors.forename: Marcio Zaffalon
authors.initials: MZ
authors.lastname: Casati
authors.forename: Siegfried V N
authors.initials: SV
authors.lastname: Jaecques
mesh_terms: D000539:Alveolar Process / Q000502:physiology; D001696:Biomechanical Phenomena; D017076:Computer-Aided Design; D059605:Dental Implant-Abutment Design; D003758:Dental Implantation, Endosseous / Q000379:methods*; D020342:Finite Element Analysis; D017276:Friction; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D057893:Immediate Dental Implant Loading / Q000379:methods; D007180:Incisor / Q000502:physiology; D008437:Maxilla / Q000502:physiology; D016348:Osseointegration / Q000502:physiology; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed / Q000379:methods; D020390:Tooth Socket / Q000502:physiology
keywords: Biomechanics; dental implant, abutment design; dental implants; finite element analysis; immediate dental implant loading; tensile strength