title: Stability of external and internal implant connections after a fatigue test.
abstract: OBJECTIVE
  The objective of this study was to compare the torque and detorque values of screw intermediates of external hexagon, internal hexagon, and Morse taper implants in single restorations before and after mechanical cycling.
  
  
  METHODS
  The study sample was divided into three groups (n = 10) as follows: group EH - external hexagon implant, group IH - internal hexagon implant, and group MT - Morse taper implant. Universal abutments were screwed on the implants, and metal crowns were cemented onto the abutment. The samples were submitted to a mechanical testing of 1 million cycles, with a frequency of 8 cycles per second under a 400 N load. The application and registration of the screw torque (T0) and detorque (T1) values of the intermediate were performed before and after the test. The results were statistically evaluated by analysis of variance (ANOVA) and Tukey's test (α = 0.05).
  
  
  RESULTS
  There was no difference between the values of T0 and T1 in the intra-group samples. However, the inter-group difference in T0 between the EH (12.8 N cm) and MT (18.6 N cm) groups and in T1 between the EH (10.4 N cm) and IH (13.8 N cm), EH and MT (19.4 N cm), and MT and IH (P = 0.001) groups were significant. The MT group showed a lower variation of T0 and T1.
  
  
  CONCLUSIONS
  The internal implants, particularly MT, showed better stability in these cases when used for single restorations.
authors.affiliation: Department of Prosthodontics, Dentistry School, University of Taubate, Taubate-SP, Brazil.
authors.forename: Paulo Cesar Pinheiro
authors.initials: PCP
authors.lastname: Feitosa
authors.affiliation: Department of Prosthodontics, Dentistry School, University of Taubate, Taubate-SP, Brazil.
authors.forename: Ana Paula Barbosa
authors.initials: APB
authors.lastname: de Lima
authors.affiliation: Department of Prosthodontics, Dentistry School, University of Taubate, Taubate-SP, Brazil.
authors.forename: Laís Regiane
authors.initials: LR
authors.lastname: Silva-Concílio
authors.affiliation: Department of Dentistry, Area of Implantology, University of Santo Amaro, São Paulo-SP, Brazil.
authors.forename: William Cunha
authors.initials: WC
authors.lastname: Brandt
authors.affiliation: Department of Prosthodontics, Dentistry School, University of Taubate, Taubate-SP, Brazil.
authors.forename: Ana Christina
authors.initials: AC
authors.lastname: Claro Neves
keywords: Dental implant; dental prosthesis; dental prosthesis retention; fatigue