Sir, given that much of the newly released Cross-Infection Control Directives HTM 01-05 has been driven by the 'theoretical' risks of prion transmission in dentistry, I am amazed that no mention has been made into products that have been proven to deactivate prions,1 rather than just removal techniques to try and eliminate proteins, where prions are tightly bound.

I am also disappointed that where HTM 01-05 states best practice, many impositions are either not evidence-based or even increase risks of transmission of disease, rather than reduce them. A good example of this is the use of unreliable and complex washer-disinfectors that finish with a high temperature rinse. It is well documented that proteins start to coagulate significantly above 40°C and the higher the temperature, the more stubbornly these proteins coagulate and harden on to surfaces, making their removal more difficult or impossible.2

HTM 01-05 is moving dentistry towards hospital-style sterilisation processes, which use washer-disinfectors and autoclaves routinely in central sterilisation facilities, yet scientific studies clearly show these methods leave significant levels of protein deposits on surgical instruments that are wrapped/processed and ready to use on patients.3 Printouts of completed cycles from equipment such as this may please bureaucrats but only prove that there was ink in the printer. Clinically leaving proteins that may bind active prions is worse. Surely this alone is an evidence-based reason to NOT follow HTM 01-05 to the letter in this respect, never mind enthusiastically labelling it 'best practice'?

I would suggest if any washer or washer-disinfectors are used as a pre-autoclave cleaning stage, the hot cycle is turned off. This will allow removal of any gross physical contamination and should inspection afterwards show minute protein deposits, these can still be further processed to allow removal, which otherwise may be impossible if proteins have been super-heated and super-coagulated on to instruments. Why should dentistry copy previously flawed methods?4

I would also suggest it is best practice to use a proven material that deactivates prions to a level that prevents transmissibility of disease. I find this most effective as a pre-cleaning soak and/or processing instruments with Prionzymeâ„¢ in a heated ultrasonic bath.

I am concerned that if practitioners do a proper risk assessment and evaluation of the current evidence, find that acting in the patients' best interests means they may be in conflict with recently released and compromised 'directives', which are rules that must be followed, that this brings us (unnecessarily) into conflict with our GDC professional standards. I therefore ask that HTM 01-05 be revised as soon as possible, but appreciate this still may not happen 'administratively' for some time. Perhaps now that the BDA have produced their new A12 Guidance online, this is the document the dental profession should refer to for any latest developments or new evidence for cross infection control. Updating our profession in an evidence based way and in a timely manner is critical. I am concerned that HTM 01-05 directives could be slow or even obstructive to amendment by comparison.