Steam Sterilization: It’s in the Bag!

by Leann Keefer, RDH, MSM

The question, “paper or plastic” takes on an entirely new meaning when related to instrument sterilization in the dental office. Classified as a medical device, there are stringent criteria for manufacturing of sterilization packaging. Quality sterilization pouches, usually constructed of paper and plastic, are a key component of any sterility assurance protocol.

The goal of a dental infection control program is to reduce the risk of disease transmission and to provide a safe environment for everyone who works in or visits a dental office.

ISO standards for performance make it clear – the only way to be sure an item has been effectively steam sterilized is to expose it to all three sterilization variables – time, temperature, and the presence of steam. Yet many traditional sterilization pouches simply have an external Type 1 process indicator validating only exposure to heat (temperature). Advanced technology is now available with one pouch design having both internal and external multi-variable (Type 4) indicators which confirms all three criteria for sterilization have been achieved and the contents have been exposed to the critical variables. Remember that chemical indicators do not contain microbial spores, therefore, they cannot prove that the contents of the pouch are sterile. 1 The use of this multi-variable pouch, in combination with weekly biological monitoring, provides a high level of sterility assurance.

There are a number of factors to consider when selecting packaging materials such as pouches or wraps. Packaging materials must be compatible with the type of sterilizer used (i.e. steam, dry heat, unsaturated chemical vapor). 2 It should be noted, all packaging types and materials are not compatible with all sterilization methods. The use of incorrect materials may prevent or reduce penetration of the sterilizing agent.

Maintaining the sterility of the instruments after sterilization is a critical component of any sterilization program, therefore, the quality and durability of the sterilization packaging is vital. The use of medical-grade surgical Kraft paper and a transparent polypropylene/polyester laminate film are recommended; caution should be exercised as some manufacturers use recycled paper. Surgical kraft paper used in sterilization pouches has a basic weight of 40-60 pounds and contains only approved additives, having controlled porosity, and having no pinholes greater than 0.5mm. 3 The sterilant enters through the paper side of the pouch and the pores must effectively close during the drying process to maintain sterility of the contents. Selection of the appropriate size of the pouch prevents overloading of instruments and helps to ensure penetration of the sterilant with less chance of tearing; there should be a minimum of 1 inch of space between the top of the instruments or cassette and the seal of the pouch.4 Most dental practices would benefit from having a variety of sizes to meet their procedural needs.

Due to the expansion and contraction of the pouch material during the sterilization process, the preferred pouch design should be of multiple side and end seals with a self-sealing adhesive strip to protect the sterility of the internal environment of the pouch. The plastic or laminate side provides strength, sealability, and thermal stability. A properly sealed pouch is indicated when the adhesive covers 50% on the paper and 50% on the laminate. If the adhesive seal is 100% on the laminate, the opening at the top of the pouch is not protected thereby compromising the sterility of the contents. It can be helpful to pre-fold the bag on the perforated line before loading the instruments as the crease will act as a guide after the protective tape is removed for sealing. Any misalignment of the seal can create gaps and compromise the sterility of the package. Before adhering the self-seal to the laminate, expel as much air as possible from the pouch; this action will help to prevent bursting of the seals during sterilization. The pressure sensitive adhesive is special in that it becomes stronger during sterilization and becomes a permanent seal for this single use device. 3

After sterilization and storage, a clean separation of the film from the paper is important to the sterility of the contents. The outer layer of the film has been exposed during transfer and storage and if any portion of the plastic remains attached to the paper, should the instruments contact the plastic surface, they will be considered contaminated and must be reprocessed.

While some controversy exists regarding paper or plastic side up. Best practice dictates placing items on their edges in a rack, like books on a shelf. This configuration allows for efficient circulation and penetration of steam while also being conducive to the drying process. Pouches should not be touched until they are dry to reduce the chance of wicking and tearing of the paper.

Armed with the knowledge of the criteria for selection and correct use of sterilization pouches will assist with safe and successful reprocessing and sterilization of instruments.

References
1. Miller CH, Palenik CJ. Infection Control and Management of Hazardous Materials for the Dental Team, 5th ed. St. Louis: Mosby Elsevier; 2014: 120-151
2. Molinari JA, Harte JA. Cottone’s Practical Infection Control in Dentistry, 3rd ed. Baltimore; Lippincott Williams & Wilkins; 2010: 148-170
3. Nagaraja PA. Hospital Sterilization, 1st ed. New Deli; Jaypee Brothers Medical; 2011: Chapter 6
4. International Association of Healthcare Central Service Material Management. Central Service Technical Manual. 7th ed. Chicago: International Association of Healthcare Central Service Material Management; 2007: 111-316


About the Author
Leann Keefer, RDH, MSM
In her role as Director of Education for Crosstex International, Ms. Keefer works to advance Crosstex’s thought leadership among influential dental care professionals. She proactively identifies trends in the fields of oral care and infection prevention, developing and implementing the corporation’s long-term strategies relating to education and professional relationships.


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