title: The effects of bone density and crestal cortical bone thickness on micromotion and peri-implant bone strain distribution in an immediately loaded implant: a nonlinear finite element analysis.
abstract: OBJECTIVE
  This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions.
  
  
  METHODS
  A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment.
  
  
  RESULTS
  The maximum extent of micromotion was approximately 100 μm in the low-density cancellous bone models, whereas it was under 30 μm in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness.
  
  
  CONCLUSIONS
  Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan .
authors.forename: Tsutomu
authors.identifier: 0000-0001-9601-9248
authors.initials: T
authors.lastname: Sugiura
authors.affiliation: Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan .
authors.forename: Kazuhiko
authors.identifier: 0000-0002-9931-889X
authors.initials: K
authors.lastname: Yamamoto
authors.affiliation: Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan .
authors.forename: Satoshi
authors.identifier: 0000-0002-1061-1986
authors.initials: S
authors.lastname: Horita
authors.affiliation: Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan .
authors.forename: Kazuhiro
authors.identifier: 0000-0002-2144-5020
authors.initials: K
authors.lastname: Murakami
authors.affiliation: Applied Electronics Laboratory, Kanazawa Institute of Technology, Tokyo, Japan .
authors.forename: Sadami
authors.identifier: 0000-0002-0672-5892
authors.initials: S
authors.lastname: Tsutsumi
authors.affiliation: Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan .
authors.forename: Tadaaki
authors.identifier: 0000-0002-6900-0397
authors.initials: T
authors.lastname: Kirita
keywords: Bone density; Dental implants; Finite element analysis