title: Abutment rotational freedom evaluation of external hexagon single-implant restorations after mechanical cycling.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the rotational freedom between implant and abutment counterpart of two abutments types over external hexagon implants submitted to mechanical cycling.
  
  
  METHODS
  Ten implants with external hexagon (3.75 mm × 13 mm), five cast abutments, and five premachined abutments both with 4.1 mm plataform size were used in this study. Ten metallic crowns were fabricated using the two types of abutments and were fixed to each implant using titanium screws (Ti6Al4V). Rotational freedom measurements were made before and after the cast procedure and after the mechanical cycling. Groups were classified according to the rotational misfit register using University of California, Los Angeles abutment and implants as new (group 1 = G1); using crowns and implants after crown casting (group 2 = G2); and using crowns and implants after mechanical cycling (group 3 = G3). Oblique loading of 120N at 1.8 Hz and 5 × 10(5) cycles was applied on specimen.
  
  
  RESULTS
  Statistical analysis (p < .05) showed that no significant difference was observed when cast abutment was compared with premachined abutment after casting (p = .390) and mechanical cycling (p = .439); however, significant difference was noted before the casting (p = .005) with higher values for the cast abutments.
  
  
  CONCLUSIONS
  Within the limitations of this in vitro study, it could be concluded that the abutment type used do not influenced the rotational freedom after casting and the amount of applied cycles (500,000 cycles) was not sufficient to significantly alter the values of rotational freedom at the implant/abutment joint.
authors.affiliation: postgraduated student, titular professor, research laboratory specialist, associated professor, Department of Dental Materials and Prosthodontics, Dental School of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil.
authors.forename: Marcela C
authors.initials: MC
authors.lastname: Junqueira
authors.forename: Thales Eduardo P
authors.initials: TE
authors.lastname: Silva
authors.forename: Ricardo F
authors.initials: RF
authors.lastname: Ribeiro
authors.forename: Adriana Cláudia L
authors.initials: AC
authors.lastname: Faria
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Macedo
authors.forename: Rossana P
authors.initials: RP
authors.lastname: de Almeida
mesh_terms: D001696:Biomechanical Phenomena; D000044:Dental Abutments; D019250:Dental Implants, Single-Tooth; D006801:Humans