title: Effect of intentional abutment disconnection on the micro-movements of the implant-abutment assembly: a 3D digital image correlation analysis.
abstract: BACKGROUND
  Implant-abutment assembly stability is critical for the success of implant-supported rehabilitation. The intentional removal of the prosthetic components may hamper the achievement of the essential stability due to preload reduction in the screw joint and implant-screw mating surface changes.
  
  
  OBJECTIVE
  To evaluate the effect of intentional abutment disconnection and reconnection in the stability of internal locking hex implants and corresponding abutments using the method of 3D digital image correlation.
  
  
  METHODS
  Ten conical shape and internal hexagon connection implants were embedded in acrylic resin and assembled to prosthetic abutments with 30 Ncm torque and assigned to two groups: group 1 - tested for static load-bearing capacity at 30° off-axis for two times and group 2 - underwent intentional disconnection and reconnection between tests. Micro-movements were captured with two high-speed photographic cameras and analyzed with video correlation system in three spacial axes U, V and W. Screw abutment and internal implant thread morphology was observed with a field-emission scanning electron microscopy.
  
  
  RESULTS
  After the intentional disconnection of the abutment, group 2 showed generally higher maximum displacements for U and V directions. Under 50N load, mean difference was 24.7 μm (P = 0.008) for U direction and -7.7 μm (P = 0.008) for V direction. No significant differences were found for maximum and minimum displacements in the W direction. Mean displacement of the speckle surface presented was statistically different in the two groups (P = 0.016). SEM revealed non-homogenous screw surfaces with scoring on group 2 plus striations and debris in the implant threads.
  
  
  CONCLUSIONS
  Micro-movements were higher for the group submitted to intentional disconnection and reconnection of the abutment, particularly under average bite forces.
authors.affiliation: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Ana
authors.identifier: http://orcid.org/0000-0003-4019-9379
authors.initials: A
authors.lastname: Messias
authors.affiliation: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Salomão
authors.initials: S
authors.lastname: Rocha
authors.affiliation: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Calha
authors.affiliation: Centre for Mechanical Engineering, University of Coimbra, Coimbra, Portugal.
authors.forename: Maria Augusta
authors.initials: MA
authors.lastname: Neto
authors.affiliation: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Nicolau
authors.affiliation: Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Fernando
authors.initials: F
authors.lastname: Guerra
mesh_terms: D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D003799:Dental Stress Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants
keywords: SEM; abutment; biomechanics; material sciences; micro-movements; prosthodontics