Sir, I write further to a recent publication in the BDJ entitled ‘Toxic ties', which raised the issue of PFAS being present in certain varieties of dental floss.1

In a press release referring to K. E. Boronow et al.,2 the American Dental Association remarked that the ADA Science Institute did not find the data sufficient to draw the conclusions which the research did.3

The study evaluated the blood samples of 178 women who self-reported on the usage of a particular brand of dental floss, to have greater PFHxS (perfluorohexanesulfonic acid) as compared to those who did not.2

The ADA Science Institute stated that a shortcoming of the study was the utilisation of fluorine measurements as a PTFE (polytetrafluoroethylene) marker, even though the subjects reporting floss usage were observed to have increased PFHxS levels.3

As PTFE is utilised in pharmaceutical, cosmetic, food and beverage applications, identifying the PTFE marker in dental floss would not establish it as the source of PFHxS in the study subjects.3

The ADA also noted that the retrospective study including self-reported data was likely to have other differences between the subjects reporting floss usage and otherwise.3