title: Influence of Alveolar Bone Loss and Different Alloys on the Biomechanical Behavior of Internal-and External-Connection Implants: A Three-Dimensional Finite Element Analysis.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the stress distribution during application of occlusal loads to maxillary anterior single external- and internal-connection implant-supported restorations with different amounts of bone loss and with the use of different metal alloys for restorations and fixation screws.
  
  
  METHODS
  Models of external- and internal-connection implants, corresponding abutments/crowns, and fixation screws were developed. These models were then imported into finite element analysis software to study the impact of forces on different implant connections and materials. Each prosthesis was subjected to a 200-N compressive shear force applied at 130 degrees relative to the long axis of the implant. The materials were considered linear, isotropic, and homogenous. The parameters changed for each connection type included: bone resorption in relation to the prosthetic platform (no, 2 mm, or 4 mm of resorption); alloys of the restorations (nonprecious vs precious); and alloys of the abutment screws (titanium vs gold). Von Mises stresses were used to display the stress in five models: implant, restoration, screw, cancellous bone, and cortical bone.
  
  
  RESULTS
  Statistically significant differences in the stresses of all involved structures occurred when the bone level decreased by 2 mm and by 4 mm. The connection type contributed to statistically significant differences in the stresses in both the restoration and the screw. The alloy type resulted in statistically significant differences in the implant, the superstructure, and the cortical bone stresses.
  
  
  CONCLUSIONS
  As bone resorbed, the stresses generated within the internal-connection implant were greater than those generated in the external-connection implant. The same findings applied for the restoration and for cancellous and cortical bone. The stresses generated in the fixation screw were greater in the external-connection implant than in the internal-connection implant for all bone resorption scenarios.
authors.forename: Alexander
authors.initials: A
authors.lastname: Tsouknidas
authors.forename: Evdokia
authors.initials: E
authors.lastname: Lympoudi
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Michalakis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Giannopoulos
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Michailidis
authors.forename: Argirios
authors.initials: A
authors.lastname: Pissiotis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Fytanidis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Kugiumtzis
mesh_terms: D016301:Alveolar Bone Loss / Q000503:physiopathology*; D003442:Crowns; D000044:Dental Abutments; D003722:Dental Alloys; D019094:Dental Prosthesis, Implant-Supported; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D008437:Maxilla; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry
chemical_list: D003722:Dental Alloys; D014025:Titanium