To: Editor, The Angle Orthodontist

Re: Kaneko K, et al. Degradation in Performance of Orthodontic Wires Caused by Hydrogen Absorption During Short-term Immersion in 2.0% Acidulated Phosphate Fluoride Solution. Angle Orthod. 2004;74: 487–495.

I read with interest the recent publication of Kaneko and coworkers in The Angle Orthodontist reporting on the degradation in performance of four major alloys of orthodontic wires, namely nickel-titanium, beta titanium, stainless steel, and cobalt-chromium-nickel, caused by hydrogen absorption during short-term immersion in an acid fluoride solution.

This was a carefully done study, and the information reported does contribute to our body of knowledge. However, the title says “Short-term Immersion” in 2% APF and later in the text they report their findings based on events occurring after they had immersed the wires for 60 minutes! That's not my definition of short-term immersion of wire in 2% APF.

If their definition of short term creates a reservation in any reader on the propriety of fluoride treatments for patients wearing orthodontic appliances, it would be very unfortunate.

The recommended time for an APF application is at most four minutes. It is well known that hydrofluoric acid will attack titanium, it is about the only thing that will. But to create a test environment that is supercritical, more than 10 times any expected exposure and then draw any clinical implications is quite a stretch.