Re: Response from Dr. Yokoyama

We would like to thank Dr Swartz for his contribution and comments concerning our article. In this article, we used the word “short-term” unlike in our previous reports,12 in which hydrogen embrittlement of titanium alloys in APF solutions was investigated by immersion tests from a few to 1000 hours. The immersion for 60 minutes was not necessarily performed under usual clinical conditions. Nevertheless, the result of this study indicates that hydrogen absorption occurs for a few minutes. This immersion test was conducted at pH 5.0 without applied stress. The use of a low pH or an applied stress larger than the critical stress for martensite transformation markedly enhanced hydrogen absorption.3 Hydrogen embrittlement prevention must be studied. Dentists should use fluoride in treatment always bearing hydrogen embrittlement in mind.