title: Impact of abutment rotation and angulation on marginal fit: theoretical considerations.
abstract: OBJECTIVE
  Rotational freedom of various implant positional index designs has been previously calculated. To investigate its clinical relevance, a three-dimensional simulation was performed to demonstrate the influence of rotational displacements of the abutment on the marginal fit of prosthetic superstructures.
  
  
  METHODS
  Idealized abutments with different angulations (0, 5, 10, 15, and 20 degrees) were virtually constructed (SolidWorks Office Premium 2007). Then, rotational displacement was simulated with various degrees of rotational freedom (0.7, 0.95, 1.5, 1.65, and 1.85 degrees). The resulting horizontal displacement of the abutment from the original position was quantified in microns, followed by a simulated pressure-less positioning of superstructures with defined internal gaps (5 µm, 60 µm, and 100 µm). The resulting marginal gap between the abutment and the superstructure was measured vertically with the SolidWorks measurement tool.
  
  
  RESULTS
  Rotation resulted in a displacement of the abutment of up to 157 µm at maximum rotation and angulation. Interference of a superstructure with a defined internal gap of 5 µm placed on the abutment resulted in marginal gaps up to 2.33 mm at maximum rotation and angulation; with a 60-µm internal gap, the marginal gaps reached a maximum of 802 µm. Simulation using a superstructure with an internal gap of 100 µm revealed a marginal gap of 162 µm at abutment angulation of 20 degrees and rotation of 1.85 degrees. The marginal gaps increased with the degree of abutment angulation and the extent of rotational freedom.
  
  
  CONCLUSIONS
  Rotational displacement of the abutment influenced prosthesis misfit. The marginal gaps between the abutment and the superstructure increased with the rotational freedom of the index and the angulation of the abutment.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Clinical Navigation and Robotics, Charité – University Medicine Berlin, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Semper
authors.forename: Silvan
authors.initials: S
authors.lastname: Kraft
authors.forename: Jurgen
authors.initials: J
authors.lastname: Mehrhof
authors.forename: Katja
authors.initials: K
authors.lastname: Nelson
mesh_terms: D003198:Computer Simulation; D000044:Dental Abutments; D015921:Dental Implants; D018772:Dental Marginal Adaptation; D006801:Humans; D021621:Imaging, Three-Dimensional; D008422:Materials Testing; D008962:Models, Theoretical; D012399:Rotation; D013499:Surface Properties; D014584:User-Computer Interface
chemical_list: D015921:Dental Implants