title: 3D finite element analysis to detect stress distribution: spiral family implants.
abstract: OBJECTIVE
  Spiral family implants are a root-form fixtures with increasing thickness of tread. This characteristic gives a self-tapping and self-condensing bone properties to implants. To study spiral family implant inserted in different bone quality and connected with abutments of different angulations a Finite Element Analysis (FEA) was performed. Once drawn the systems that were object of the study by CAD (Computer Aided Design), the FEA discretized solids composing the system in many infinitesimal little elementary solids defined finite elements. This lead to a mesh formation where the single finite elements were connected among them by nodes. For the 3 units bone-implant-abutments several thousand of tetrahedral elements having 10 parabolic nodes were employed.
  
  
  METHODS
  The biomechanical behaviour of 4.2 mm × 13 mm dental implants, connecting screw, straight and 15° and 25° angulated abutment subjected to static loads, in contact with high and poor bone quality was evaluated by FEA. A double system was analyzed: a) FY strength acting along Y axis and having 200 N intensity; b) FY and FZ couple of strengths applied along Y and Z directions and having respectively 200N and 140N intensity. The materials were considered as homogeneous, linear and isotropic. Then the FEA simulation was performed hypothesizing a linearity between loads and deformations.
  
  
  RESULTS
  The lowest stress value was found in the system composed by implants and straight abutments loaded with a vertical strength, while the highest stress value were found in implants and 15° angulated abutment loaded with a angulated strength. In addition, the lower is the bone quality (i.e. D4) the higher is the distribution of the stress within the bone.
  
  
  CONCLUSIONS
  Spiral family implants can be used successfully in low bone quality but a straight force is recommended.
authors.affiliation: Dental School, University of Chieti, Chieti, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Danza
authors.forename: Ilaria
authors.initials: I
authors.lastname: Zollino
authors.forename: Luigi
authors.initials: L
authors.lastname: Paracchini
authors.forename: Guidi
authors.initials: G
authors.lastname: Riccardo
authors.forename: Stefano
authors.initials: S
authors.lastname: Fanali
authors.forename: Francesco
authors.initials: F
authors.lastname: Carinci
keywords: Biomechanics; Distribution; Finite element analysis; Implant; Spiral; Stress