title: SEM observations on stress corrosion cracking of commercially pure titanium in a topical fluoride solution.
abstract: OBJECTIVES. The purpose of the present study was to determine whether commercially pure titanium is susceptible to stress corrosion cracking/hydrogen embrittlement in a topical fluoride solution used in preventive dentistry.
  
  
  METHODS
  Thin electropolished titanium test specimens were previously cold-rolled or cold-rolled and annealed before testing. For the stress corrosion tests, the U-shaped specimens of both treatment types were stressed into a radius of curvature of 30 mm. Then, the bent part was placed in the fluoride solution at 37 degrees C for 1, 5, 10, and 20 d. The effects of the fluoride solution on cold-rolled and annealed titanium were studied using a scanning electron microscope. In addition, mechanically fractured surfaces of cold-rolled titanium specimens exposed and not exposed to the fluoride solution were examined by SEM. A qualitative evaluation of the surfaces was conducted.
  
  
  RESULTS
  Narrow cracks were observed in cold-rolled specimens following exposure to the fluoride solution for 5 d. The cracks were associated with branching, a characteristic of stress corrosion cracking. The cold-rolled specimen exposed to the fluoride solution exhibited a brittle fracture. In contrast, the fracture mode of the unexposed specimen was ductile in nature.
  
  
  CONCLUSIONS
  Topical fluoride solutions can cause stress corrosion cracking of commercially pure titanium.
authors.affiliation: Department of Prosthetic Dentistry, University of Helsinki, Finland.
authors.forename: M H
authors.initials: MH
authors.lastname: Könönen
authors.forename: E T
authors.initials: ET
authors.lastname: Lavonius
authors.forename: J K
authors.initials: JK
authors.lastname: Kivilahti
mesh_terms: D000588:Amines / Q000737:chemistry; D003343:Corrosion; D003799:Dental Stress Analysis; D003802:Dentifrices / Q000737:chemistry; D003959:Diamines; D005459:Fluorides / Q000737:chemistry; D005460:Fluorides, Topical / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D012969:Sodium Fluoride / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D000588:Amines; D003802:Dentifrices; D003959:Diamines; D005460:Fluorides, Topical; C094808:amine fluoride solution; D006859:Hydrogen; C495399:Olaflur; D012969:Sodium Fluoride; D014025:Titanium; D005459:Fluorides