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Torque removal evaluation of prosthetic screws after tightening and loosening cycles: an in vitro study
Author(s) -
Cardoso Mayra,
Torres Marcelo Ferreira,
Lourenço Eduardo José Veras,
de Moraes Telles Daniel,
Rodrigues Renata Cristina Silveira,
Ribeiro Ricardo Faria
Publication year - 2012
Publication title -
clinical oral implants research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.407
H-Index - 161
eISSN - 1600-0501
pISSN - 0905-7161
DOI - 10.1111/j.1600-0501.2011.02165.x
Subject(s) - abutment , torque , materials science , orthodontics , dentistry , implant , significant difference , dental abutments , reduction (mathematics) , mathematics , structural engineering , medicine , engineering , surgery , geometry , physics , statistics , thermodynamics
Objectives: The aim of this study was to evaluate the variation in removal torque of implant prosthetic abutment screws after successive tightening and loosening cycles, in addition to evaluating the influence of the hexagon at the abutment base on screw removal torque.Material and methods: Twenty hexagonal abutments were tightened to 20 regular external hex implants with a titanium alloy screw, with an insertion torque of 32 N cm, measured with a digital torque gauge. The implant/abutment/screw assemblies were divided into two groups: (1) abutments without hexagon at the base and (2) abutments with a hexagon at the base. Each assembly received a provisional restoration and was submitted to mechanical loading cycles. After this, the screws were removed and the removal torque was measured. This sequence was repeated 10 times, then the screw was replaced by a new one, and another cycle was performed. Linear regression analysis was performed.Results: Removal torque values tended to decrease as the number of insertion/removal cycles increased, for both groups. Comparisons of the slopes and the intercepts between groups showed no statistical difference. There was no significant difference between the mean values of last five cycles and the 11th cycle. Within the limitations of this in vitro study, it was concluded that (1) repeated insertion/removal cycles promoted gradual reduction in removal torque of screws, (2) replacing the screw with a new one after 10 cycles did not increase resistance to loosening, and (3) removal of the hexagon from the abutment base had no effect on the removal torque of the screws.To cite this article :
Cardoso M, Torres MF, Lourenço EJV, de Moraes Telles D, Rodrigues RCS, Ribeiro RF. Torque removal evaluation of prosthetic screws after tightening and loosening cycles: an in vitro study.
Clin. Oral Impl. Res . 23 , 2012 475–480.
doi: 10.1111/j.1600‐0501.2011.02165.x