title: Detorque evaluation of dental abutment screws after immersion in a fluoridated artificial saliva solution.
abstract: OBJECTIVE
  Implant-abutment connections still present failures in the oral cavity due to the loosening of mechanical integrity by detorque and corrosion of the abutment screws. The objective of this study was to evaluate the detorque of dental abutment screws before and after immersion in fluoridated solutions.
  
  
  METHODS
  Five commercial implant-abutment assemblies were assessed in this investigation: (C) Conexão®, (E) Emfils®, (I) INP®, (S) SIN®, and (T) Titanium Fix®. The implants were embedded in an acrylic resin and then placed in a holding device. The abutments were first connected to the implants and torqued to 20 Ncm using a handheld torque meter. The detorque values of the abutments were evaluated after 10 minutes. After applying a second torque of 20 Ncm, implant-abutment assemblies were withdrawn every 3 hours for 12 hours in a fluoridated solution over a period of 90 days. After that period, detorque of the abutments was examined. Scanning electronic microscopy (SEM) associated to energy dispersive spectroscopy (EDS) was applied to inspect the surfaces of abutments.
  
  
  RESULTS
  Detorque values of systems C, E, and I immersed in the fluoridated solution were significantly higher than those of the initial detorque. ANOVA demonstrated no significant differences in detorque values between designs S and T. Signs of localized corrosion could not be detected by SEM although chemical analysis by EDS showed the presence of elements involved in corrosive processes.
  
  
  CONCLUSIONS
  An increase of detorque values recorded on abutments after immersion in fluoridated artificial saliva solutions was noticed in this study. Regarding chemical analysis, such an increase of detorque can result from a corrosion layer formed between metallic surfaces at static contact in the implant-abutment joint during immersion in the fluoridated solutions.
authors.affiliation: Division of Prosthodontics, School of Dentistry-DOD, Universidade Federal do Rio Grande do Norte, 59056-000 Natal, Brazil. rduarte60@yahoo.com.br
authors.forename: Antônio R C
authors.initials: AR
authors.lastname: Duarte
authors.forename: João P Silva
authors.initials: JP
authors.lastname: Neto
authors.forename: Júlio C M
authors.initials: JC
authors.lastname: Souza
authors.forename: Wellington C
authors.initials: WC
authors.lastname: Bonachela
mesh_terms: D000497:Alloys; D002327:Cariostatic Agents / Q000737:chemistry*; D003343:Corrosion; D000044:Dental Abutments; D003722:Dental Alloys / Q000737:chemistry; D059605:Dental Implant-Abutment Design; D019232:Dental Restoration Failure; D005459:Fluorides / Q000737:chemistry*; D007101:Immersion; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012464:Saliva, Artificial / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry; D019415:Torque
chemical_list: D000497:Alloys; D002327:Cariostatic Agents; D003722:Dental Alloys; D012464:Saliva, Artificial; C031462:titanium alloy (TiAl6V4); D014025:Titanium; D005459:Fluorides