Cross infection control measures and the treatment of patients at risk of Creutzfeldt Jakob disease in UK general dental practice

The experience of dental practices that use automatic washer disinfectors

Background

Understanding the collective sociotechnical experiences of the staff in dental practices with automatic washer disinfectors (AWDs) may help shape future strategies that encourage the transition towards best practice in dental instrument decontamination and reprocessing.

Objectives

To find the emerging themes that reflect the experience of working with an AWD in dental practice. To compare the experience of practice owners to that of the dental nurses.

Methods

A qualitative semi-structured interview-based methodology was applied using a convenience sample of dentists and dental nurses. Verbatim transcripts of audio recordings underwent thematic analysis.

Results

Dental practice owners and dental nurses were interviewed. Four themes were common to both groups: impact on daily routine; mundane technology; the decontamination cycle; and safety. Three themes were unique to the dentists: impact on the business; professionalism; and external motivators for change.

Discussion

AWDs are a mundane form of technology that dental nurses find simple to operate. The extended time it takes to reprocess instruments using an AWD means that dental nurses must adapt their daily working practices to accommodate this. Initial funding to purchase an AWD, especially where there is a professional expert leading a campaign championing their use, can be effective.

Human Immunodeficiency Virus (HIV) Transmission in Dentistry

HIV transmission in the health-care setting is of concern. To assess the current position in dentistry, we have reviewed the evidence to November 1, 2005. Transmission is evidently rare in the industrialized nations and can be significantly reduced or prevented by the use of standard infection control measures, appropriate clinical and instrument-handling procedures, and the use of safety equipment and safety needles. We hope that breaches in standard infection control will become vanishingly small. When occupational exposure to HIV is suspected, the application of post-exposure protocols for investigating the incident and protecting those involved from possible HIV infection further reduces the likelihood of HIV disease, and also stress and anxiety.

Microbial contamination of light curing units: a pilot study

Visible light units (LCU) used in routine dentistry to cure light activated materials may become contaminated with oral micro-organisms. This pilot study was designed to investigate whether the fan, handle and base unit mains on/off button areas of three different designs of quartz tungsten halogen LCUs (3M Unitek 2500, Elipar Highlight, Demetron Optilux 401) were effectively disinfected after use in a dental teaching hospital. Over a period of seven days 52 LCUs were swabbed before clinics in the morning and 28 were swabbed again after clinics in the afternoon. Bacterial contamination was detected on approximately 40% (20/52) of units before use and 64% (18/28) after use: few viable organisms were detected on the fan or handle areas, but many were isolated from the mains button, including Staphylococus aureus. These findings highlight the need for greater awareness of the potential risk of contamination of the base unit and compliance with recommendations to clean and disinfect all areas of the units.

Management of infection control in dental practice

This was an observational study in which the management policies and procedures associated with infection control and instrument decontamination were examined in 179 dental surgeries by a team of trained surveyors. Information relating to the management of a wide range of infection control procedures, in particular the decontamination of dental instruments, was collected by interview and by examination of practice documentation. This study found that although the majority of surgeries (70%) claimed to have a management policy on infection control, only 50% of these were documented. For infection control policies, 79% of surgeries had access to the British Dental Association Advice Sheet A12. Infection control policies were claimed to be present in 89% of surgeries, of which 62% were documented. Seventy-seven per cent of staff claimed to have received specific infection control training, but for instrument decontamination this was provided mainly by demonstration (97%) or observed practice (88%). Many dental nurses (74%) and dental practitioners (57%) did not recognise the symbol used to designate a single-use device. Audit of infection control or decontamination activities was undertaken in 11% of surgeries. The majority of surgeries have policies and procedures for the management of infection control in dental practice, but in many instances these are not documented. The training of staff in infection control and its documentation is poorly managed and consideration should be given to development of quality management systems for use in dental practice.

Risk assessment of transmission of sporadic Creutzfeldt-Jakob disease in endodontic practice in absence of adequate prion inactivation

BACKGROUND

Experimental results evidenced the infectious potential of the dental pulp of animals infected with transmissible spongiform encephalopathies (TSE). This route of iatrogenic transmission of sporadic Creutzfeldt-Jakob disease (sCJD) may exist in humans via reused endodontic instruments if inadequate prion decontamination procedures are used.

METHODOLOGY/PRINCIPAL FINDINGS

To assess this risk, 10 critical parameters in the transmission process were identified, starting with contamination of an endodontic file during treatment of an infectious sCJD patient and ending with possible infection of a subsequent susceptible patient. It was assumed that a dose-risk response existed, with no-risk below threshold values. Plausible ranges of those parameters were obtained through literature search and expert opinions, and a sensitivity analysis was conducted. Without effective prion-deactivation procedures, the risk of being infected during endodontic treatment ranged between 3.4 and 13 per million procedures. The probability that more than one case was infected secondary to endodontic treatment of an infected sCJD patient ranged from 47% to 77% depending on the assumed quantity of infective material necessary for disease transmission. If current official recommendations on endodontic instrument decontamination were strictly followed, the risk of secondary infection would become quasi-null.

CONCLUSION

The risk of sCJD transmission through endodontic procedure compares with other health care risks of current concern such as death after liver biopsy or during general anaesthesia. These results show that single instrument use or adequate prion-decontamination procedures like those recently implemented in dental practice must be rigorously enforced.

Infection Control: A Survey of UK Special Care Dentists and Dental Care Professionals

Aim

To determine attitudes to and practice of infection control among practitioners involved in special care dentistry.

Methods

A questionnaire on the issues of decontamination and infection control was sent to all 680 members of the British Society for Disability and Oral Health.

Results

The response rate was 63.5%. Almost all respondents (95%) reported having a local infection-control policy; most (97%) had local protocols for the management of inoculation injuries; most (81%) gave new staff training in infection-control procedures and most (74%) provided updates for established staff. Most respondents ‘usually’ or ‘always’ provided eye protection for patients (95%) and themselves (93%). Virtually all routinely wore gloves, and nearly all (94%) ‘always’ changed gloves between patients. The majority ‘usually’ or ‘always’ disinfected or disposed of surface coverings between patients (98%), sterilised all non-disposable instruments that had been set out for the patient (99%), and disinfected laboratory work (96%).

Conclusions

There was high awareness of infection-control issues, and good reported compliance among these dental workers.

Activity of an alkaline 'cleaner' in the inactivation of the scrapie agent

The capacity of a routinely available alkaline cleaner for medical devices to inactivate the causative agent of a transmissible spongiform encephalopathy (TSE) was tested. The co-incubation of brain homogenates, prepared from terminally ill scrapie-infected hamsters, with the cleaner led to the denaturation of misfolded protein as the proteinase K-resistant prion protein was no longer detectable after such treatment. In addition, intra-cerebral inoculation of hamsters with the alkaline cleaner-treated and subsequently neutralized samples reduced the level of infectivity of the material below the limit of detection. This report shows the possibility that a routinely available alkaline cleaner could reduce the infectivity of TSE agents and so minimize the risk of iatrogenic transmission of TSEs by asymptomatic carriers. This study is intended to encourage further investigations in this field.

Comparison of the efficacies of disinfectants to control microbial contamination in dental unit water systems in general dental practices across the European Union

Water delivered by dental unit water systems (DUWS) in general dental practices can harbor high numbers of bacteria, including opportunistic pathogens. Biofilms on tubing within DUWS provide a reservoir for microorganisms and should be controlled. This study compared disinfection products for their ability to meet the American Dental Association's guideline of <200 CFU x ml(-1) for DUWS water. Alpron, BioBlue, Dentosept, Oxygenal, Sanosil, Sterilex Ultra, and Ster4Spray were tested in DUWS (n = 134) in Denmark, Germany, Greece, Ireland, The Netherlands, Spain, and the United Kingdom. Weekly water samples were tested for total viable counts (TVCs) on yeast extract agar, and, where possible, the effects of products on established biofilm (TVCs) were measured. A 4- to 5-week baseline measurement period was followed by 6 to 8 weeks of disinfection (intermittent or continuous product application). DUWS water TVCs before disinfection ranged from 0 to 5.41 log CFU x ml(-1). Disinfectants achieved reductions in the median water TVC ranging from 0.69 (Ster4Spray) to 3.11 (Dentosept) log CFU x ml(-1), although occasional high values (up to 4.88 log CFU x ml(-1)) occurred with all products. Before treatment, 64% of all baseline samples exceeded American Dental Association guidelines, compared to only 17% following commencement of treatment; where tested, biofilm TVCs were reduced to below detectable levels. The antimicrobial efficacies of products varied (e.g., 91% of water samples from DUWS treated with Dentosept or Oxygenal met American Dental Association guidelines, compared to 60% of those treated with Ster4Spray). Overall, the continuously applied products performed better than those applied intermittently. The most effective products were Dentosept and Oxygenal, although Dentosept gave the most consistent and sustained antimicrobial effect over time.

Residual protein levels on reprocessed dental instruments

Reduction of the initial bioburden on instruments, prior to sterilization, is believed to reduce transmission risks of iatrogenic Creutzfeldt-Jakob disease. Endodontic files are used in the preparation of root canals and are likely to have close contact and become contaminated with neural material from branches of the maxillary and mandibular cranial nerves. This study examined methods used by 22 dental practices to clean endodontic files, and scored visible debris and residual protein levels adhering to 220 dental endodontic files that had been used, cleaned, autoclaved and were deemed ready for re-use. Visible debris was scored after examination under a dissecting light microscope. Residual protein was quantified using a fluorescent assay based on reaction of proteins with o-phthaldialdehyde/N-acetyl cysteine. There was wide variation in the methods used by practices to clean endodontic files. The cleaning process varied from a wipe with an alcohol-impregnated cloth to hand scrubbing and/or use of an ultrasonic bath. Surface debris was visually detected on 98% of files. Residual protein was detected on all the files examined (median amount: 5.4 microg; range: 0.5-63.2 microg). These results demonstrate that the cleaning of some instruments reprocessed routinely in primary care is incomplete, and such instruments cannot be excluded as a potential source of cross-infection.

A study of visual and blood contamination on reprocessed endodontic files from general dental practice

OBJECTIVE

This study examined methods used for reprocessing endodontic instruments in general dental practice and determined the degree of residual visual contamination and blood contamination on 250 reprocessed files collected from 25 general dental practices.

MATERIALS AND METHODS

A questionnaire was administered to 25 general dental practitioners to obtain information on the re-processing of used endodontic files. Ten files which had been used and reprocessed were also collected from each practice. These were examined visually under a dissecting light microscope for residual contamination and then tested for blood deposits using the Kastle-Meyer test.

RESULTS

Nineteen of the 25 practices used stainless steel hand files. No practitioners used endodontic files as single use devices. Ninety-two per cent of the practitioners discarded and replaced files when they were bent or damaged. Several decontamination methods were reported. The two combinations employed most frequently were manual cleaning and autoclaving or manual cleaning, followed by ultrasonic cleaning and autoclaving. Of the 250 files, 75% showed some degree of visual contamination and seven percent tested positive for residual blood. Blood contaminated files were significantly more heavily contaminated when examined visually. Large variations were found in residual contamination of files collected from practices using the same methods of decontamination.

CONCLUSIONS

While all practitioners re-used endodontic files, the variations in decontamination methods reported indicate a lack of clarity on best practice. This study demonstrates that endodontic files are not reliably decontaminated by methods currently employed in dental practice.

Autoclave use in dental practice in the Republic of Ireland

AIMS

To assess by postal questionnaire, cross-infection control methods, especially sterilisation procedures, of 700 general dental practitioners in the Republic of Ireland, and to biologically monitor steam pressure sterilisers or autoclaves in their practices.

MAIN OUTCOME MEASURES

Methods of instrument cleaning and sterilisation, autoclave efficacy.

RESULTS

A response rate of 40% with all, except one practitioner, using steam sterilisation. 49% also reported the use of chemical sterilisation with a quarter of these using glutaraldehyde. However, instrument soaking time varied greatly from 2.5 minutes to 74 hours. Methods of instrument cleaning prior to autoclaving were as follows: scrubbing by hand 41.5%, ultrasonic cleaning 7.0%, combination of both 50%. 52.9% of the respondents did not autoclave their dental handpieces and only 44.7% disinfected impressions before sending them to the laboratory. The autoclaves of thirty practitioners (11.3%) did not pass the initial biological test. Following counselling about possible causes of failure, four autoclaves (1.5%) failed a repeat biological test. However, seven practitioners did not return the repeat biological test.

CONCLUSIONS

Some aspects of recommended cross-infection control procedures are well adhered to, e.g. instrument cleaning, but further education is required in certain key areas, in particular the use of chemical sterilisation, dental handpiece autoclaving and impression disinfection. There is also a need to increase awareness of the importance of routine autoclave servicing and calibration, along with validation and monitoring.

Plasma cleaning of dental instruments

The theoretical risk of prion transmission via surgical instruments is of current public and professional concern. These concerns are further heightened by reports of the strong surface affinity of the prion protein, and that the removal of organic material by conventional sterilization is often inadequate. Recent reports of contamination on sterilized endodontic files are of particular relevance given the close contact that these instruments may make with peripheral nerve tissue. In this paper, we report the effective use of a commercial gas plasma etcher in the cleaning of endodontic files. A representative sample of cleaned, sterilized, files was screened, using scanning electron microscopy and energy-dispersive X-ray analysis, to determine the level of contamination before plasma cleaning. The files were then exposed for a short-term to a low-pressure oxygen-argon plasma, before being re-examined. In all cases, the amount of organic material (in particular that which may have comprised protein) was reduced to a level below the detection limit of the instrument. This work suggests that plasma cleaning offers a safe and effective method for decontamination of dental instruments, thus reducing the risk of iatrogenic transmission of disease during dental procedures. Furthermore, whilst this study focuses on dental files, the findings indicate that the method may be readily extended to the decontamination of general surgical instruments.

Problems with the decontamination of dental handpieces and other intra-oral dental equipment in hospitals

Dental departments within district general hospitals contain items of equipment that require decontamination between patients. Some of these items are complex and expensive, and in busy clinics, may be required in large numbers if a sterile services department (SSD) were to be used. This may result in local manual cleaning of these instruments and sterilization in non-vacuum downward displacement autoclaves within dental departments, despite some items having narrow lumens, deep recesses and cavities, which will not adequately sterilize these instruments. Infection control teams should be aware of these difficulties particularly when arranging satisfactory infection control and decontamination procedures in hospital dental departments.

Managing the risk of nosocomial transmission of prion diseases

PURPOSE OF REVIEW

Prion diseases such as Creutzfeldt-Jakob disease represent a unique infection control problem because prions exhibit an unusual resistance to conventional chemical and physical decontamination methods. This paper reviews the recent literature and provides recommendations for the prevention of nosocomial transmission of prion agents.

RECENT FINDINGS

Recommendations to prevent the cross-transmission of infection from medical devices potentially contaminated with prions have been based primarily on prion inactivation studies. Newer recommendations consider inactivation data, but also use epidemiological studies of prion transmission, the infectivity of human tissues, and the efficacy of removing microbes by cleaning. Prion-specific disinfection/sterilization is required in only limited settings. Healthcare workers are not at risk of acquiring transmissible spongiform encephalopathies. Blood or blood products have not been demonstrated to be vehicles for transmission.

SUMMARY

On the basis of scientific data, only critical (e.g. surgical instruments) and semicritical devices contaminated with high-risk tissue (i.e. brain, spinal cord, eye) from high-risk patients (e.g. with known or suspected Creutzfeldt-Jakob disease) require special treatment.

Contaminated dental instruments

There is current concern in the UK over the possible transmission of prions via contaminated surgical instruments. Some dental instruments (endodontic files) raise particular concerns by virtue of their intimate contact with terminal branches of the trigeminal nerve. A visual assessment using a dissecting light microscope and scanning electron microscopy of endodontic files after clinical use and subsequent decontamination was performed. The instruments examined were collected from general dental practices and from a dental hospital. Seventy-six per cent (22/29) of the files retrieved from general dental practices remained visibly contaminated, compared with 14% (5/37) from the dental hospital. Current methods for decontaminating endodontic instruments used in dentistry may be of an insufficient standard to completely remove biological material. Improved cleaning methods and the feasibility of single use endodontic instruments require further investigation.

Variant Creutzfeldt-Jakob disease--a problem for general dental practitioners?

Over a hundred deaths from variant Creutzfeldt-Jakob disease (vCJD) have now been recorded. The incubation period for vCJD may be up to 40 years and the number of asymptomatic carriers in the population could be as many as 100,000. Confirmed iatrogenic transmission of other human transmissible spongiform encephalopathies raises the possibility of cross-infection from apparently healthy persons who are incubating vCJD. Decontamination techniques routinely used in general dental practice are incapable of inactivating the infective protein responsible for transmitting the disease. So far, no evidence exists to preclude the risk of iatrogenic infection occurring during dental procedures. The author reviews present knowledge of the infective agent, its transmissibility, its origins, current guidelines and the implications for dental practice.

Systematic review of adherence to infection control guidelines in dentistry

OBJECTIVES

The purpose of this study was to determine the knowledge and attitudes of dental health care workers (DHCWs) towards infection control procedures, to examine DHCWs' practising behaviour in respect of infection control, and to determine whether a relationship exists between knowledge, attitudes and behaviour.

METHODS

Within this systematic review, study quality was assessed in line with selection criteria relating to study design, participants, interventions and outcome measures. Following data extraction, the heterogeneity of study design, targeted participants, sample size and outcome measures precluded a quantitative analysis. Qualitative data synthesis followed.

RESULTS

Overall, the quality of the studies reviewed was poor. Only 71 studies meeting the selection criteria were identified. Data indicated that over the period of the review there have been substantial improvements with compliance in some areas of infection control in dentistry, for example glove wearing. However, other aspects, such as the effective management of needlestick injuries, remain problematic.

CONCLUSIONS

More rigorously designed studies are required to assess accurately dental team members' adherence to infection control guidelines.