Australian Dental Journal 2001;46:4. 251 Classical and variant Creutzfeldt-Jakob diseases and their potential impact on the practice of clinical dentistry in Australia SWY Chan,* S Collins,† CL Masters,† DM Walker* Abstract Following recent published evidence regarding the experimental transmission of prion diseases via blood transfusion, dental practitioners have expressed their concern about the potential impact of these transmissible spongiform encephalopathies on dental care provision. This review provides updated information on Creutzfeldt-Jakob disease and related disorders and highlights their potential significance for the practice of clinical dentistry. The current guidelines in Australia relating to infection control and clinical dental procedures are discussed together with recommended guidelines and considerations from the United Kingdom and the World Health Organization (WHO). Key words: Prion disease; Creutzfeldt-Jakob disease; infection control; clinical dentistry. (Received for publication February 2001. Revised March 2001. Accepted May 2001.) characterized histopathologically by microscopic vacuolation (spongiform change) in the cerebral grey matter, astrocytic proliferation and loss of neurones. 2 Considerable scientific data supports the current belief that TSEs are caused by infectious particles (prions) composed predominantly, if not exclusively, by an abnormal conformation of a cell-surface glycoprotein which is protease-resistant and referred to as PrP SC . 2,3 The normal cellular isoform, known otherwise as PrP C , is encoded by a host gene (PRNP) on chromosome 20. 3,4 PrP SC is insoluble and appears inextricably linked to disease pathogenesis in contrast to PrP C which is soluble and protease-sensitive. 4-6 PrP SC is found exclusively in neural tissues in classical CJD, while it is also found in lymphoreticular tissues in vCJD and may accumulate as amyloid-like deposits in the brain (Table 1). Types of CJD There are inherited, acquired or horizontally transmitted (including vCJD derived from BSE) and sporadic forms of human TSEs. 7 The inherited forms of human TSEs are due to mutations in PRNP and include fatal familial insomnia (FFI) and Gerstmann-Sträussler- Scheinker syndrome (GSS). Individuals with FFI present with progressive insomnia, dysautonomia, motor dysfunction and cognitive deterioration; the age of onset is usually between 40 and 60 years. Neuropathologically, abnormalities are located predominantly within the anteroventral and mediodorsal thalamic nuclei. By contrast, individuals with GSS tend to present with progressive cerebellar dysfunction and dementia. Within FFI and GSS families with more variable phenotypes are well recognised, including those more akin to CJD. 2 It has been shown that all forms of TSEs, including the inherited forms can be transmitted to experimental animals. A model that demonstrates the importance of the direct interaction between PrP molecules explains how this is possible. It is proposed that the disease- related isoform of PrP (PrP SC ) interacts with the normal cellular isoform, PrP C and causes a conformational change in the latter leading to progressive accumulation *Oral Pathology Unit, Westmead Dental Clinical School, The University of Sydney. †Department of Pathology, The University of Melbourne. REVIEW Australian Dental Journal 2001;46:(4):251-257 INTRODUCTION This review is aimed at providing information on transmissible spongiform encephalopathies (TSEs), in particular Creutzfeldt-Jakob disease (CJD) and variant CJD (vCJD). The significance of TSEs on clinical dentistry will be discussed. Proposed infection control guidelines for Australia will be provided together with a review of the recommended guidelines and considerations from the United Kingdom (UK) and from the World Health Organization. Background TSEs comprise a group of fatal neurodegenerative diseases which includes CJD in humans, scrapie in sheep and bovine spongiform encephalopathy (BSE) or ‘mad cow disease’. Variant CJD is most likely zoonotically linked to BSE. 1 These diseases are