Bioassay Studies Support the Potential for Iatrogenic Transmission of Variant Creutzfeldt Jakob Disease through Dental Procedures

Abstract

BackgroundEvidence is required to quantify the potential risks of transmission of variant Creutzfeldt Jakob (vCJD) through dental procedures. Studies, using animal models relevant to vCJD, were performed to address two questions. Firstly, whether oral tissues could become infectious following dietary exposure to BSE? Secondly, would a vCJD-contaminated dental instrument be able to transmit disease to another patient?MethodsBSE-301V was used as a clinically relevant model for vCJD. VM-mice were challenged by injection of infected brain homogenate into the small intestine (Q1) or by five minute contact between a deliberately-contaminated dental file and the gingival margin (Q2). Ten tissues were collected from groups of challenged mice at three or four weekly intervals, respectively. Each tissue was pooled, homogenised and bioassayed in indicator mice.FindingsChallenge via the small intestine gave a transmission rate of 100% (mean incubation 157±17 days). Infectivity was found in both dental pulp and the gingival margin within 3 weeks of challenge and was observed in all tissues tested within the oral cavity before the appearance of clinical symptoms. Following exposure to deliberately contaminated dental files, 97% of mice developed clinical disease (mean incubation 234±33 days).InterpretationInfectivity was higher than expected, in a wider range of oral tissues, than was allowed for in previous risk assessments. Disease was transmitted following transient exposure of the gingiva to a contaminated dental file. These observations provide evidence that dental procedures could be a route of cross-infection for vCJD and support the enforcement of single-use for certain dental instruments.

Compliance with infection prevention and control in oral health-care facilities: a global perspective

“…The potential risk of further human-to-human transmission of the disease through contaminated instruments is a further concern 64 . Recently, a study in the UK indicated that the risk of vCJD transmission during oral health-care procedures was higher than previously expected 111 . This study also revealed transmission of vCJD after exposure of a patient's gingival tissues to a contaminated endodontic file, and not just from nerve tissue exposure, as previously suggested.…”

Single-use of endodontic hand files: perceptions and practise

“…• • Difficulty in adequately cleaning endodontic files (Walker et al, 2007); • • The risk of transmission of infectious diseases (Laheij et al, 2001); • • The potential transmission of prion disease (Kirby et al, 2012;Walker et al, 2007);…”

Decontamination technology assessments – who assesses the assessments?

“…Drivers to recent improvements were the identification of poor performance (including quantities of residual protein on instruments ready for re-use [1][2][3][4] ) and the risk assessments undertaken to determine potential for transmission of iatrogenic CJD via surgical routes. 5,6 The scientific principles underpinning the cleaning and sterilisation of surgical instruments has been understood for several decades. Unfortunately, many of these reports [7][8][9] are now frequently overlooked by those new to the field.…”