Dental Sterilization

Monitoring

How is the sterilization process monitored?

Sterilization procedures should be monitored through a combination of mechanical, chemical, and biological techniques designed to evaluate the sterilizing conditions and the procedure's effectiveness.

• Mechanical techniques for monitoring sterilization include assessing the cycle time, temperature, and pressure of sterilization equipment by observing the gauges or displays on the sterilizer. Some tabletop sterilizers have recording devices that print out these parameters. Correct readings do not ensure sterilization, but incorrect readings could be the first indication that a problem has occurred with the sterilization cycle.

• Chemical indicators, internal and external, use sensitive chemicals to assess physical conditions such as temperature during the sterilization process. Chemical indicators such as heat sensitive tape change color rapidly when a given parameter is reached. An internal chemical indicator should be placed in every sterilization package to ensure the sterilization agent has penetrated the packaging material and actually reached the instruments inside. An external indicator should be used when the internal indicator cannot be seen from outside the package. Single-parameter internal indicators provide information on only one sterilization parameter and are available for steam, dry heat, and unsaturated chemical vapor. Multiparameter internal indicators measure 2–3 parameters and can provide a more reliable indication that sterilization conditions have been met. Multiparameter internal indicators are only available for steam sterilizers (i.e., autoclaves). Refer to manufacturer instructions for proper use and placement of chemical indicators.

Indicator test results are shown immediately after the sterilization cycle is complete and could provide an early indication of a problem and where the problem occurred in the process. If the internal or external indicator suggests inadequate processing, the item that has been processed should not be used. Because chemical indicators do not prove sterilization has been achieved, a biological indicator (i.e., spore test) is required.

• Biological indicators (BIs) are the most accepted means of monitoring the sterilization process because they directly determine whether the most resistant microorganisms (e.g., Geobacillus or Bacillus species) are present rather than merely determine whether the physical and chemical conditions necessary for sterilization are met. Because spores used in BIs are more resistant and present in greater numbers than are the common microbial contaminants found on patient care equipment, an inactivated BI indicates that other potential pathogens in the load have also been killed.

How often should I perform biological monitoring (BI) (spore testing)?

Correct functioning of sterilization cycles should be verified for each sterilizer by the periodic (at least weekly) use of BIs. Users should follow the manufacturer's directions concerning the appropriate placement of the BI in the sterilizer. A control BI (not processed through the sterilizer) from the same lot as the test indicator should be incubated with the test BI. The control BI should yield positive results for bacterial growth. In addition to conducting routine biological monitoring, equipment users should perform biological monitoring.

• Whenever a new type of packaging material or tray is used.
• After training new sterilization personnel.
• After a sterilizer has been repaired.
• After any change in the sterilizer loading procedures.

If sterilizing an implantable device, should users perform biological monitoring (spore testing) more frequently?

Any load containing implantable devices should be monitored. Ideally, implantable items should not be used until the results of tests are known to be negative. As previously noted, the manufacturer's directions concerning the appropriate placement of the biologic indicator (BI) in the sterilizer must be followed. A control BI (not processed through the sterilizer) from the same lot as the test indicator should be incubated in the same manner as the test BI. The control biological indicator should yield positive results for bacterial growth.

What should I do if a spore test result is positive?

If the mechanical (e.g., time, temperature, pressure) and chemical (internal or external) indicators suggest that the sterilizer is functioning properly, a single positive spore test result probably does not indicate sterilizer malfunction. Items other than implantable items do not necessarily need to be recalled; however, sterilizer operators should repeat the spore test immediately using the same cycle that produced the positive BI. The sterilizer should be removed from service and sterilization operating procedures reviewed to determine whether operator error could be responsible.

If the result of the repeat spore test is negative and operating procedures were correct, then the sterilizer can be returned to service. If the repeat spore test result is positive, do not use the sterilizer until it has been inspected or repaired and rechallenged with BI tests in three consecutive empty-chamber sterilization cycles. When possible, items from suspect loads dating back to the last negative BI should be recalled, rewrapped, and resterilized.

Results of biological monitoring and sterilization monitoring reports should be recorded.

Common Factors Influencing the Effectiveness of Sterilization

Modified from Miller CH and Palenik CJ (2010).

Selected References and Additional Resources

American Dental Association. Biological indicators for verifying sterilization. J Am Dent Assoc 1988; 117:653–654.

American Dental Association. Guidelines for infection control in the dental office and the commercial dental laboratory. J Am Dent Assoc 1996;127:672–680.

Andres MT, Tejerina JM, Fierro JF. Reliability of biologic indicators in a mail-return sterilization-monitoring service: A review of 3 years, Quintessence Intern 1995;25:865–870.

ANSI/AAMI ST-79 2006/AI:2008 Comprehensive Guide to Steam Sterilization and Sterility Assurance in Health Care Facilities (2008 ed., pages 43–79 and 116).

Association of Operating Room Nurses. AORN standards and recommended practices for perioperative nursing. 1987;Section III:14.1-III:14.11.

Association of Operating Room Nurses. Recommended practices for sterilization in perioperative practice settings. In: Fogg D, Parker N, Shevlin D, eds. Standards, Recommended Practices, and Guidelines, Denver: AORN, 2002;333–342.

Baird RM. Sterility Assurance: Concepts, Methods and Problems. In Russell AD, Hugo WB, Ayliffe GAF, eds. Principles and Practice of Disinfection, Preservation, and Sterilization. Oxford, England: Blackwell Scientific Publications, 3rd edition. Oxford, England: Blackwell Scientific Publications, 1999;787–800.

CDC. Guidelines for Infection Control in Dental Health-Care Settings, 2003. MMWR, December 19, 2003:52(RR-17).

CDC Recommended infection control practices for dentistry, 1993. MMWR 1993;42(No. RR-8):1–12.

Favero MS. Developing indicators for monitoring sterilization. In: Rutala W, ed. Disinfection, Sterilization, and Antisepsis in Healthcare. Washington, DC: Association for Professionals in Infection Control and Epidemiology, Inc.,1998:119–132.

Garner JS, Favero MS. Guideline for handwashing and hospital environmental control. Atlanta: U.S. Department of Health and Human Services, Public Health Service, CDC, 1985.

Maki DG, Hassemer CA. Flash sterilization: Carefully measured haste. Infect Control 1987;18:307–310.

Miller CH, Sheldrake MA. The ability of biological indicators to detect sterilization failures. Am J Dent 1994;7:95–97.

Miller CH, Palenik CJ. Instrument processing. In: Miller CH, Palenik DJ, eds. Infection Control and Management of Hazardous Materials for the Dental Team, 2nd ed. St. Louis: Mosby, 1998;135–174.

Miller, CH. Use of spore test for quality assurance in infection control. Am J Dent 2001;14:114.

Molinari JA, Rosen S, Runnells RR. Heat sterilization and monitoring. In: Cottone JA, Terezhalmy GT, Molinari JA, eds. Practical Infection Control in Dentistry, 2nd ed. Baltimore: Williams & Wilkins, 1996: 149–160.

Packaging and Storage

What types of packaging materials are available for sterilizing instruments?

Packaging materials (e.g., wrapped or container systems) allow penetration of the sterilization agent and maintain sterility of the processed item after sterilization. Materials for maintaining sterility of instruments during transport and storage include wrapped perforated instrument cassettes, peel pouches of plastic or paper, and sterilization wraps (which can be either woven or unwoven). Packaging materials should be designed for the type of sterilization process being used. Packaging materials also should be appropriate for the items being sterilized. For example, nonpaper materials should be used to package sharp instruments which can easily puncture paper packaging. Avoid using metal closures (e.g., staples, paper clips) that can puncture packaging materials. A chemical indicator/integrator should be placed among the instruments, inside the package, as well as on the outside of each package (see FAQ Sterilization – Monitoring).

Types and Use of Sterilization Packaging Materials

Modified from Miller CH and Palenik CJ (2010).

Can cassettes be used for sterilizing instruments?

The use of instrument cassettes facilitates instrument processing and can greatly enhance the organization of instruments. It also keeps all the instruments for a specific procedure together from the chairside procedure through cleaning, rinsing, drying, and sterilization. Following completion of dental treatment, instruments can be arranged in the cassette, transported to the instrument processing area, and placed in the ultrasonic cleaner as a unit. The cassette also can be rinsed and dried in this manner. In addition, a cassette system can reduce direct handling of potentially contaminated instruments before sterilization. Furthermore, instruments prearranged in the cassette will require less handling following sterilization.

Different types of cassettes are available. It is important to follow the manufacturer's recommendations for cleaning, wrapping, and sterilizing the cassettes. Perforated cassettes are preferable, since completely solid containers will not allow steam or chemical vapor to reach the contents and allow sterilization to occur. Cassettes can occupy more space than individual packages, so you should consider the size of the sterilizer and amount of storage space available before purchasing any cassette systems.

How should items be stored following sterilization?

Sterile items and disposable (single-use) items should be stored in an enclosed storage area (e.g., cabinet or drawer). Dental supplies and instruments should not be stored under sinks or in other locations where they might become wet. Sterilized items should remain wrapped until they are needed for use.

Unwrapped items are susceptible to contamination. Avoid storing items loose in drawers or cabinets because unwrapped items cannot be kept sterile. Items stored in this manner are subject to contamination from dust, aerosols generated during treatment, and the hands of personnel who must handle them.

What is the shelf-life of sterilized instruments?

Sterilized instruments should be stored in a manner that preserves the integrity of the packaging material. Storage practices can be either date- or event-related. Although some facilities continue to date every sterilized package and use shelf-life practices (first in, first out), other facilities have switched to event-related practices. This approach recognizes that the product should remain sterile until some event causes the item to become contaminated (e.g., a package becomes torn or wet). The quality of the packaging material, the conditions under which items are stored and transported, and the amount that they are handled all affect the chances that the package and its contents will remain sterile. All packages containing sterile items should be inspected before use to verify barrier integrity and dryness. Any package that is wet, torn, dropped on the floor, or damaged in any way should not be used. The instruments should be recleaned, packaged in new wrap, and sterilized again.

Even for event-related packaging, the date of sterilization should be placed on the package. If multiple sterilizers are used in the facility, the sterilizer used should also be indicated on the outside of the packaging material. This information can facilitate retrieval of processed items in the event of a sterilization failure.

Selected References and Additional Resources

Association of Operating Room Nurses. Recommended practices for sterilization in perioperative practice settings. In: Fogg D, Parker N, Shevlin D, eds. Standards, Recommended Practices, and Guidelines, Denver: AORN, 2002;333–342.

Butt WE, Bradley DV Jr, Mayhew RB, Schwartz RS. Evaluation of the shelf life of sterile instrument packs. Oral Surgery, Oral Medicine, Oral Pathology 1991;72:650–654.

CDC. Guidelines for Infection Control in Dental Health-Care Settings, 2003. MMWR, December 19, 2003:52(RR–17).

Harte JA, Molinari JA. Instrument Processing and Recirculation. In: Molinari JA, Harte JA, eds. Practical Infection Control in Dentistry, 3rd ed. Baltimore: Lippincott Williams & Wilkins, 2010;221–231.

Klapes NA, Greene VW, Angholz AC, Hunstiger C. Effect of long-term storage on sterile status of devices in surgical packs. Infection Control 1987;8:289–293.

Mayworm D. Sterile shelf life and expiration dating. Journal of Hospital Supply, Processing, and Distribution 1984;2:32–35.

Miller CH, Palenik CJ. Instrument processing. In: Miller CH, Palenik CJ, eds. Infection Control and Management of Hazardous Materials for the Dental Team, 2nd ed. St. Louis: Mosby, 1998;135–174.

Miller CH, Palenik CJ. Sterilization, disinfection, and asepsis in dentistry. In: Block SS, ed. Disinfection, Sterilization, and Preservation, 5th ed. Philadelphia: Lippincott Williams and Wilkins, 2001;1049–1068.

Molinari JA, Rosen S, Runnells RR. Heat sterilization and monitoring. In: Cottone JA, Terexhalmy GT, Molinari JA, eds. Practical Infection Control in Dentistry, 2nd ed. Baltimore: Williams & Wilkins, 1996;149–160.

Schwartz RS, Butt WE, Bradley DV, Mayhew RB. Safe storage times for sterile dental packs. Military Medicine 1992;157:406–409.

Schwartz RS, Davis RD. Safe storage times for sterile dental packs. Oral Surgery 1990;70:297–300.