title: Influence of lubricant on screw preload and stresses in a finite element model for a dental implant.
abstract: BACKGROUND
  Loosening or fracture of the abutment screw are frequent complications in implant dentistry and are detrimental to the long-term success of the restorations. However, little is known about the factors influencing the stability of the screw-abutment complex.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the influence of lubricant action during implant assembly on screw preload and stresses in a dental implant-abutment complex.
  
  
  METHODS
  A dental implant was modeled for finite element stress analysis. Different friction coefficients (μ=0.2 to 0.5) were chosen for the interfaces between implant components to simulate lubricant action or dry conditions. The stress analyses were each divided into 2 load steps. First, the abutment screw was virtually tightened with a torque of 25 Ncm. This was achieved by applying an equivalent preload calculated according to the different friction coefficients chosen. Second, the construction was externally loaded with a force of 200 N inclined by 30 degrees relative to the implant axis.
  
  
  RESULTS
  The screw preload increased with the decreasing friction coefficient. In all components, stresses increased with decreasing friction coefficient. Plastic deformation was observed at the implant neck in an area that expanded with decreasing friction coefficient. No plastic deformation occurred in the abutment.
  
  
  CONCLUSIONS
  The results of this study indicated that screw preload should be included in the finite element analysis of dental implants for a realistic evaluation of stresses in the implant-abutment complex. The friction coefficient significantly influenced the screw preload value and modified the stresses in the implant-abutment complex.
authors: Scientific Assistant, Department of Prosthetic Dentistry and Biomedical Materials Science, Hannover Medical School, Hannover, Germany.
authors: Daniela
authors: D
authors: Jörn
authors: Associate Professor, Department of Prosthetic Dentistry and Biomedical Materials Science, Hannover Medical School, Hannover, Germany. Electronic address: kohorst.philipp@mh-hannover.de.
authors: Philipp
authors: P
authors: Kohorst
authors: Assistant Professor, Institute of Continuum Mechanics, Leibniz University Hannover, Hannover, Germany.
authors: Silke
authors: S
authors: Besdo
authors: Associate Professor, Department of Cranio-Maxillofacial Surgery, Hannover Medical School, Hannover, Germany.
authors: Martin
authors: M
authors: Rücker
authors: Professor, Head of Department of Prosthetic Dentistry and Biomedical Materials Science, Hannover Medical School, Hannover, Germany.
authors: Meike
authors: M
authors: Stiesch
authors: Senior Lecturer, Department of Prosthetic Dentistry and Biomedical Materials Science, Hannover Medical School, Hannover, Germany.
authors: Lothar
authors: L
authors: Borchers
mesh_terms: D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D003890:Desiccation; D055119:Elastic Modulus; D020342:Finite Element Analysis; D017276:Friction; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D054327:Lubricants / Q000737:chemistry*; D017711:Nonlinear Dynamics; D012463:Saliva / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019415:Torque; D014584:User-Computer Interface
chemical_list: D015921:Dental Implants; D054327:Lubricants