vCJD and the Cleanability of Endodontic Files

A case for single use

By JT Walker, C Budge, M Vassey, JM Sutton, ND Raven, PD Marsh, P Bennett

This article considers the evidence underpinning the UK Health Department’s guidance that root canal instruments must be treated as single use as a precaution to reduce any risk of variant Creutzfeldt-Jakob disease (vCJD) transmission.


Some instruments such as endodontic files are inherently difficult to clean and may come into contact with peripheral nerves known to carry vCJD. Hence, the provision of clear and unambiguous advice to dentists from the Department of Health in a communication Advice for dentists on re-use of endodontic instruments and variant Creutzfeldt-Jakob Disease (vCJD) will ensure that endodontic reamers and files are treated as single use to further reduce any risk of vCJD transmission through dentistry.

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Are Routine Sterilization Procedures Effective?

by Archie Morrison, DDS, MS, FRCD(C), and Susan Conrod, DDS


Purpose: The complex miniature architecture of dental burs and endodontic files makes precleaning and sterilization difficult. Devising a sterilization protocol for endodontic files and dental burs requires care, and some have suggested that these instruments be considered single-use devices. One purpose of this study was to determine the effectiveness of various sterilization techniques currently used in dentistry for the resterilization of dental burs and endodontic files. The second aim was to determine whether new dental burs and endodontic files, as supplied in packages from the manufacturer, are sterile.

Materials and Methods: The sterility of new (unused) and used dental burs and endodontic files before and after various sterilization procedures was analyzed. New burs and files were tested immediately after removal from manufacturers' packaging, with or without prior sterilization. Burs and files that had been used in various dental offices were precleaned, packaged, resterilized and then tested for various pathogens. Each item was individually removed from the sterilization packaging, transferred by sterile technique into Todd-Hewitt broth, incubated at 37°C for 72 hours and observed for bacterial growth.

Results: Sterilization procedures were 100% effective for unused burs and unused files but were less than 100% effective for all other test groups. Contamination rates following sterilization ranged from 15% for one group of used burs (p = 0.01) to 58% for one group of used files (p < 0.001).

Conclusions: Dental burs and endodontic files, as packaged by the manufacturer, are not sterile and should therefore be sterilized before first use. The resterilization procedures tested here were not adequate, and more rigorous sterilization procedures are needed. If such procedures cannot be devised, these instruments should perhaps be considered single-use devices.

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Resterilization of Instruments

By Nicholas J.V. Hogg, MSc, DDS, and Archibald D. Morrison, DDS, MSc, FRCD(C)


Objective: The transmission of pathogens from one patient to another via contaminated devices has been a high- profile issue in infection control. Although single-use devices have been promoted as a preventative strategy, resterilization of instruments has been a common practice in dentistry. The purpose of this study was to investigate the rate of bacterial contamination of instruments resterilized for use in oral and maxillofacial procedures in a hospital-based clinic.

Methods: The experiment was a prospective randomized controlled study. The test group consisted of burs that had been used in surgical procedures. These burs were grossly debrided before being cleaned and gas sterilized in the central sterilizing department of the hospital. The burs were transferred in a sterile fashion into a culture medium selected to grow oral bacteria. The control group comprised new unused instruments treated in an identical fashion before culturing. All burs were incubated and monitored daily for 72 h.

Results: The rate of bacterial contamination in the test groups was significantly higher than in the control group (p < 0.05).

Conclusions: Reuse of instruments can be cost-effective if the safety of patients can be assured; however, there is increasing evidence that the sterilization process may not be completely effective. Consideration should be given to the classification of certain types of dental burs as single-use devices if sterilization cannot be guaranteed.

MeSH Key Words: cross infection/prevention & control; dental instruments; disinfection methods; equipment reuse

Sterilization of instruments ensures that they are free of “all microbial life including microbial spores which1 are the most difficult of micro-organisms to kill.” If the sterilization process is effective in killing bacterial spores, it will also be effective against mycobacteria and all viruses, including herpes simplex virus, hepatitis and HIV.1

Resterilization is “the repeated application of a terminal process designed to remove or destroy all viable forms of microbial life, including bacterial spores, to an acceptable sterility assurance level.”2 Resterilization of instruments used on one patient for reuse on another has been common practice in dentistry and oral and maxillofacial surgery. Some instruments used in oral and maxillofacial and orthopedic procedures, such as bone drills and saws, are Class I instruments as defined by the United States’ Food and Drug Administration and can be reused if sterility can be guaranteed.3 However, there is now evidence that the sterilization process is complex and that if strict adherence to an effective protocol is not followed, contamination of instruments may result.

In the past decade, single-use devices (SUDs) have been promoted in many dental and medical practices as a strategy to prevent the transmission of blood- and tissue- borne pathogens from patient to patient. This practice has also been influenced by high-profile legal cases that have brought the issue of SUDs to the attention of the media and the public.4 For example, in Toronto in 2002, a case involving a patient who contracted the hepatitis B virus via contaminated electroencephalogram electrodes resulted in a $27.5-million settlement against the neurologist and hospital.4 SUDs are convenient and their use has become widespread in hospitals around the world. However, the use of disposable instruments does not come without a significant cost to the health care system as well as environmental concern.5

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Infection Control Made Simple

Why are endodontic instruments re-used? In a nutshell... to save costs. Material costs are indeed reduced by re-using endodontic instruments. If, however, the costs for single use instruments are compared to the additional costs arising from re-use, such as costs for instrument reprocessing, sterile storage and keeping proper records, the anticipated saving shrinks to a minimum that bears no relation to the possible drawbacks of multiple instrument use.

Current discussions are focussing more and more on the topic of multiple-use. Looking at the mandatory quality management and the extended infection control requirements for dental practices, it can be assumed that this subject will gain even more importance in the near future and that the re-use of endodontic instruments will be questioned even more critically.

The aim of this brochure is to discuss the pros and cons of instrument re-processing and re-use and to help the dentist in making a decision. This brochure is based on German and European statutory and formal requirements for infection control and quality management in a dental practice.

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Single-use Medical Devices

Implications and Consequences of Reuse

by the Department of Health

This publication draws attention to the hazards and risks associated with reprocessing and reusing single-use medical devices. It covers the legal issues and regulatory requirements of such actions. It also considers the implications of damage to the materials or construction of the device and inadequate decontamination procedures.

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Decontamination of Dental Burs


A comparison of decontamination methods used for dental burs

by C. L. Whitworth, M. V. Martin, M. Gallagher and H. V. Worthington Br Dent J 2004; 197: 635-640


This study investigated the bacterial and fungal contamination of used dental burs. A novel assay system for comparison of efficacy of pre-sterilization cleaning techniques for dental burs was used to evaluate manual scrubbing, enzymic agents and washer-disinfectors.


Thirty dental burs contaminated during cavity preparation were analysed for micro biological total viable counts and species of bacteria and fungi present. To simulate clinically contaminated burs, a culture of Streptococcus sanguis NCTC 7863 was used to inoculate unused dental burs, alone and combined with blood, saliva or a mixture of blood and saliva. Contaminated burs were subjected to six pre-sterilisation cleaning techniques and the log reduction in contamination achieved by each method was assessed.


The microbial count from used dental burs ranged from 0 to 6.92x104 CFU ml-1. Many potentially pathogenic species were identified. The decontamination assay demonstrated that autoclaving alone was not sufficient to sterilize dental burs. Manual scrubbing in air was less efficacious than manual scrubbing under water (p<0.001). The most effective method of pre-sterilization cleaning for dental burs was a washer-disinfector.

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Reusing disposable items: saving money or risking cross-contamination?

Published in Dental Economics by Mary Govoni, CDA, RDA, RDH, MBA


Burs and diamonds can be particularly difficult to clean, therefore increasing the risk of cross-infection. Hand-scrubbing of these items may be the most effective means of removing debris; however, it poses a greater risk of spatter exposure or puncture injuries to the team members who are performing this function. And although burs should be heat-sterilized in packages, they are frequently placed in chemical sterilants and stored in large bur blocks in the treatment rooms that are not packaged, and therefore potentially recontaminated prior to use.

Not only does the reuse of single-use items pose a risk of cross-infection, it can decrease efficiency in terms of the time spent in cleaning and disinfecting these difficult-to-clean items and the time necessary for chemical sterilization. Using new disposables each time, such as disposable burs, can actually increase efficiency and possibly comfort for the patient. Since the burs are always sharp and can cut tooth surfaces more quickly than reusable burs, a procedure can be completed in a shorter time.

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Biofilm on and structural damage of rotary cutting instruments after 5 cycles of clinical use and processing

Francisco Antonio Uchoa-JuniorTerezinha de Jesus Esteves BarataLara Stefânia Netto de Oliveira Leão-VasconcelosEvandro Leão RibeiroAnaclara Ferreira Veiga Tipple


Background: Rotary cutting instruments (RCIs) are sterilized routinely. The authors aimed to analyze the structural integrity, presence of dirt, and microbial contamination of RCIs used in clinical practice after processing.

Methods: Eighty-four RCIs (42 carbide burs, 42 diamond burs) were divided into baseline, control, and test groups. The RCIs were evaluated by means of scanning electron microscopy and microbiological analysis. Evaluation criteria included presence of structural damage, dirt, biofilm, and isolated cells and their phenotypic profile.

Results: The carbide burs from all groups and diamond burs from the test groups had structural damage. Dirt was observed in the baseline and test groups. Three bacterial species were isolated from 4 RCIs (9.52%). An isolated cell was observed from 1 carbide bur. Biofilm was observed on 3 RCIs (7.14%).

Conclusions: RCIs should not be subjected to multiple uses; after the first clinical use they accumulate structural damage and dirt that hampers the cleaning step, causing failure in the sterilization process.

Practical implications: The presence of microorganisms and structural damage on the RCIs confirmed that they are not amenable to processing, a fact that characterizes them as a single-use health care product.

Keywords: Dental instruments; biofilm; microbiological analysis; scanning electron microscopy; sterilization.

Should Surgical Burs Be Used as Single-Use Devices to Avoid Cross Infection? A Case-Control Study

Badr A Al-Jandan1Mohamed Gafar AhmedKhalifa Sulaiman Al-KhalifaImran Farooq

Objective: The purpose of this study was to evaluate and compare the rate of bacterial contamination of reused and new unused burs after different sterilization sessions.

Materials and methods: The test group consisted of 40 used fissure burs, and the control group of 40 unused new fissure burs (total n = 80). The burs from both groups were precleaned according to standard protocols and then subjected to two sterilization sessions (high- and low-steam pressure autoclaving). After each sterilization session, the burs were transferred into incubation tubes which contained thioglycollate culture medium and were monitored daily for a period of 48 h to detect any bacterial growth. Data were collected and statistical analysis was done using Fisher's exact test.

Results: Of the 40 burs of the test group, 2 burs (5%) showed positive bacterial growth, whereas no bur from the control group showed any sign of bacterial growth after high-pressure autoclaving. The colony structure and Gram staining were compatible with the growth of Staphylococcus epidermis. After a second sterilization session at low-pressure steam autoclaving, no bacterial growth was observed for the test group, but 1 bur (2.5%) from the control group showed bacterial growth and Gram-positive staining matched well with the growth of Brevibacterium species.

Conclusions: The new and unused burs were 100% sterile after high-pressure steam autoclaving, whereas 5% of the reused burs appeared positive with bacterial contamination. After low-pressure steam autoclaving, reused burs were 100% sterile, but 1 new bur demonstrated bacterial contamination.