SEM observations on stress corrosion cracking of commercially pure titanium in a topical fluoride solution.

UNLABELLED

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.

SIGNIFICANCE

Topical fluoride solutions can cause stress corrosion cracking of commercially pure titanium.