title: Biomechanical evaluation of screw- and cement-retained implant-supported prostheses: a nonlinear finite element analysis.
abstract: BACKGROUND
  The mechanical stability of the prosthetic components in the implant-prosthesis complex is essential to the long-term success of the restorations. However, little is known about the differences in the biomechanical behavior of screw- and cement-retained prostheses.
  
  
  OBJECTIVE
  The purpose of this study was to compare the preload maintenance, stresses, and displacements of prosthetic components of screw- and cement-retained implant-supported prostheses by using the finite element method in a nonlinear analysis.
  
  
  METHODS
  Two 3-dimensional models were constructed: implant-supported fixed partial prostheses with 3 elements retained either by screws (SFP) or cement (CFP). After the simulation of screw tightening, the preload was calculated for both prostheses. Then vertical and oblique loads (100 N) were applied on the models. The preload was identified, the maximum von Mises equivalent stresses (SEQV) were obtained on the screws, and the displacement among the abutment, the implant, and screw was identified by observing the penetration and gap in the contact interfaces.
  
  
  RESULTS
  Under vertical load, there was a higher decrease in the preload and in the SEQV on the screw in the SFP. Under oblique load, the SEQV was 24% higher on the screw of the SFP. In the displacement analysis under vertical load, penetration was concentrated in the threads of the screw in the SFP and between the abutment and implant in the CFP. The gap was 118% greater for the SFP and was concentrated on the abutment extension. Under oblique load, the displacement pattern was similar for both prostheses, but with values 66% higher for penetration and 96% higher for gap for the SFP.
  
  
  CONCLUSIONS
  The SFP showed a higher biomechanical risk of failure than the CFP.
authors: Visiting Professor, Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil. Electronic address: guilhermeccs@ufmg.br.
authors: Guilherme Carvalho
authors: GC
authors: Silva
authors: Adjunct Professor, Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Tulimar Machado
authors: TM
authors: Cornacchia
authors: Associate Professor, Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Cláudia Silami
authors: CS
authors: de Magalhães
authors: Visiting Professor, Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Audrey Cristina
authors: AC
authors: Bueno
authors: Associate Professor, Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Allyson Nogueira
authors: AN
authors: Moreira
mesh_terms: D001696:Biomechanical Phenomena; D002484:Cementation / Q000379:methods; D003198:Computer Simulation; D017076:Computer-Aided Design; D054893:Cone-Beam Computed Tomography / Q000379:methods; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003781:Denture Retention / Q000295:instrumentation; D003830:Denture, Partial, Fixed; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008422:Materials Testing; D008954:Models, Biological; D017711:Nonlinear Dynamics; D013314:Stress, Mechanical; D013499:Surface Properties; D019415:Torque