SEM OBSERVATIONS ON STRESS-CORROSION CRACKING OF COMMERCIALLY PURE TITANIUM IN A TOPICAL FLUORIDE SOLUTION

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 preven tive 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 treat ment types were stressed into a radius of curvature of 30 mm. Then, th e 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 microscop e. In addition, mechanically fractured surfaces of cold-rolled titaniu m specimens exposed and not exposed to the fluoride solution were exam ined by SEM. A qualitative evaluation of the surfaces was conducted. R esults. 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 co ld-rolled specimen exposed to the fluoride solution exhibited a brittl e fracture. In contrast, the fracture mode of the unexposed specimen w as ductile in nature. Significance. Topical fluoride solutions can cau se stress corrosion cracking of commercially pure titanium.