Sterilization of instruments: successes and pitfalls Part 1 -- sterilizers and sterilization packaging

March 21, 2011
In Part 1 of this series, Leslie Canham, CDA, RDA, discusses the three types of sterilizers most commonly used in dental offices and how to achieve proper sterilization by adhering to the CDC’s Infection Control Guidelines.

By Leslie Canham, CDA, RDA

The three types of sterilizers most commonly used in dental offices are:

  1. Steam sterilization (autoclave)
  2. Dry heat sterilization
  3. Unsaturated chemical vapor sterilizers

Autoclaves use steam and are either gravity displacement or pre-vacuum-type sterilizers. Temperatures reach approximately 250 degrees F to 273 degrees F. Sterilization times range from four to 30 minutes depending on temperature, whether instruments are wrapped or unwrapped, and manufacturer’s instructions. The drying cycle may be 25 to 40 minutes.

Dry heat sterilizers are either static air or forced air. The high heat and extended time are major factors in achieving sterilization. Temperatures reach approximately 300 degrees F to 375 degrees F. Sterilization times vary from 12 to 150 minutes depending on temperature and manufacturer’s instructions.

Unsaturated chemical vapor sterilizers use a combination of alcohol, formaldehyde, ketone, acetone, and water to create a vapor for sterilizing. The combination of pressure, temperature, and time are the major factors in achieving sterilization. Pressure should measure 20 psi, temperatures should reach 270 degrees F, and sterilization time is approximately 20 to 40 minutes.

All devices used for heat sterilization of dental instruments must be medical sterilization equipment that has been cleared by the FDA. Always follow the manufacturer’s instructions for sterilization times, temperatures, and other operating parameters, as well as instructions for correct use of containers, wraps, and chemical or biological indicators. Toaster ovens or glass bead sterilizers are not considered acceptable devices for sterilizing dental instruments and could jeopardize patient safety.

Pitfalls in achieving sterilization

  • Interrupting the sterilization cycle, or inadequate time, temperature, or pressure
  • Inadequate pre-cleaning of instruments
  • Overloading of sterilizer
  • Inadequate drying cycle (autoclaves)
  • Faulty gaskets or seals
  • Improper packaging
  • Bulky packaging
  • Inadequate spacing of instruments
  • Improper operation of unit

The Centers for Disease Control and Prevention (CDC) recommendations state that instruments should be wrapped or packaged before being placed in the sterilizer. CDC recommendations state:

Cleaned instruments and other dental supplies should be inspected, assembled into sets or trays, and wrapped, packaged, or placed into container systems for sterilization. Packaging materials (e.g., wraps 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 (i.e., woven and nonwoven). Packaging materials should be designed for the type of sterilization process being used.1

Different types of materials are used for packaging instruments. For steam sterilizers, they are paper wrap, nylon “plastic” tubing, paper/plastic peel pouches, thin cloth, and wrapped perforated cassettes.

For dry heat sterilizers, they are paper wrap, appropriate nylon “plastic” tubing, wrapped perforated cassettes, or closed containers. (Closed containers should have biological indicators or spore tests within the container to confirm sterilization.)

For unsaturated chemical vapor sterilizers, they are paper wrap, paper/plastic peel pouches, and wrapped perforated cassettes.

Pitfalls in achieving sterilization

Using the wrong types of sterilization packaging material can hinder sterilization.

  • Some packaging may prevent the sterilizing agent from reaching the instruments inside.
  • Some plastics may melt.
  • Some paper may burn or char.
  • Thick cloths may absorb too much steam.
  • Closed containers are not appropriate for steam or unsaturated chemical vapor sterilizers.
  • Cloths absorb too much chemical vapor.
  • Lint fibers may cause postoperative complication and serve as vehicles for microorganisms, increasing the risk of infection for surgical patients.

Sterilization of unwrapped instruments

An unwrapped cycle (sometimes called flash sterilization) is a method for sterilizing unwrapped patient care items for immediate use. Unwrapped sterilization should be used only under certain conditions:

  1. Thorough cleaning and drying of instruments precedes the unwrapped sterilization cycle.
  2. Mechanical monitors are checked and chemical indicators used for each cycle.
  3. Care is taken to avoid thermal injury to dental workers or patients.
  4. Items are transported aseptically to the point of use to maintain sterility.1

A word of caution when preparing instruments for sterilization

To avoid getting poked with a contaminated instrument, dental workers should wear puncture-resistant utility gloves while cleaning and packaging or wrapping instruments prior to sterilization. In addition, careful handling of contaminated instruments includes techniques such as making sure all instruments are fully inside the sterilization pouch when sealing, and properly placing the cassette before closing.

Maintaining sterility

Always seal the sterilization bag or pouch at the perforation. When a bag or pouch is folded below the perforation, such as folding it in half, the opening of the package will not be sealed, therefore instruments will not maintain sterility inside the package. Most sterilization bags are either self-sealing or heat-sealed. Never use safety pins, staples, or paper clips to seal the bag or pouch. For sterilization bags that are not self- or heat-sealed, use chemical indicator tape to seal the package.

Disposable sterilization bags, pouches, or wraps are single-use items unless otherwise indicated. Instruments are considered sterile indefinitely inside a sterilized sealed pouch, unless an event compromises the package. Events that could compromise sterility include opening the pouch, instruments poking through the pouch, torn or punctured package or wrap, allowing wet packages to come into contact with contaminated surfaces, or placing a sterile package in an area where it could become moist or wet.

The Centers for Disease Control and Prevention Infection Control Guidelines for dental health-care settings provides recommendations for dental infection control. Your state dental board might have separate infection-control regulations or might adopt the CDC guidelines as the infection-control regulations. Check with your state dental board to learn about your infection-control regulations.

In Part 2 of “Sterilization of instruments: successes and pitfalls,” we will cover chemical indicators, process integrators, and spore testing.

Author bio
Leslie Canham is a dental speaker and consultant specializing in infection control and OSHA compliance. She has more than 36 years of experience in dentistry. Canham is the founder of Leslie Canham Seminars, providing in-office training, mock inspections, consulting, and online seminars and webinars to help the dental team navigate state and federal regulations. Reach Canham at (888) 853-7543 or Leslie Canham.


1. Centers for Disease Control and Prevention. Guidelines for Infection Control in Dental Health-Care Settings 2003. MMWR 2003; 52(No. RR-17):21-23.