title: Vertical fracture and marginal bone loss of internal-connection implants: a finite element analysis.
abstract: OBJECTIVE
  Marginal bone loss around implants is of great concern, and its cause may be multifactorial. Recently, clinical cases presenting marginal bone loss, in most cases accompanied by vertical fracture of internal-connection implants in the buccolingual direction, have been reported, in which unfavorable stress distribution is one possible cause of marginal bone resorption. The purpose of the current study was to characterize this type of marginal bone loss and implant fracture by conducting a finite element analysis (FEA).
  
  
  METHODS
  Clinical and radiographic evaluations showed that the prostheses of all reported cases had implant-level setups and were directly screwed to the internal implants. Intriguingly, all vertical fractures reported were in the buccolingual direction. Therefore, to characterize the specific implant fractures, FEA was conducted with misfit models created for two different setups, abutment-level and implant-level, both with screw-retained prostheses. The models were subjected to initial misfits of 0 μm (representing perfect fit), 50 μm, 100 μm, 150 μm, or 200 μm, and vertical loading was then applied.
  
  
  RESULTS
  FEA revealed that, for the implant-level setup, excessive stress at the neck of the implant gradually increased in the buccolingual direction as the misfit increased. This result was not seen for the abutment-level setup. A broad maximum stress distribution was evident for the implant-level setup but not for the abutment-level setup.
  
  
  CONCLUSIONS
  Broad distribution of excessive stress in the FEA correlated to the clinical cases, and marginal bone loss in these cases may be associated with mechanical alterations. To avoid unnecessary complications, selection of an abutment-level setup is strongly suggested.
authors.affiliation: Department of Prosthodontics, Malmö University, Malmö, Sweden. ryo.jimbo@mah.se
authors.forename: Ryo
authors.initials: R
authors.lastname: Jimbo
authors.forename: Anders
authors.initials: A
authors.lastname: Halldin
authors.forename: Martin
authors.initials: M
authors.lastname: Janda
authors.forename: Ann
authors.initials: A
authors.lastname: Wennerberg
authors.forename: Stefan
authors.initials: S
authors.lastname: Vandeweghe
mesh_terms: D001696:Biomechanical Phenomena; D001862:Bone Resorption / Q000209:etiology*; D000044:Dental Abutments; D015921:Dental Implants / Q000009:adverse effects*; D019232:Dental Restoration Failure; D020342:Finite Element Analysis; D006801:Humans; D008962:Models, Theoretical; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants