Infection Control Protocol
1. General Principle
MicroDental Laboratories is concerned with preventing the transmission of infectious diseases and cross-contamination. In particular, the oral environment is inhabited with commensal oral flora and blood-borne pathogens are potentially present on incoming items that have had contact with the patient’s mucosa. On the other hand, pathogens and contaminants that came into contact with cases during processing at the laboratory could potentially remain and pose a risk to patients when placed in contact with their mucosa. As such, our main objective is to prevent cross-contamination before, during, and after processing and eliminate pathogenic micro-organisms on items that are highly likely to come into contact with patients’ mucosa. According to Spaulding Classification, these items are considered semicritical. Aside from that, the Guidelines for Infection Control in Dental Health-Care Settings (CDC, 2003) contain a specific section for dental laboratories to address what needs to be done. It stated that incoming items that may be contaminated “should be thoroughly cleaned, disinfected with an EPA-registered hospital disinfectant with a tuberculocidal claim, and thoroughly rinsed.” Also, the laboratory should establish a “separate receiving and disinfecting area” “to reduce contamination in the production area.” Waste generated, such as disposable trays or impression materials, “can be discarded with general waste” unless otherwise falling under the category of regulated medical waste. Appliances and prostheses delivered should be disinfected with “an EPA registered hospital disinfectant (low to intermediate),” and the item placed in a “tamper-evident container” before returning.
2. Disinfection Protocol
While some materials (e.g., impression materials) may require specific disinfection procedures, a general disinfecting protocol for intermediate-level disinfection and for low-level disinfection is adopted for ease of application. Further, since
EPA registration only applies to products sold within the United States. Products with similar effectiveness are selected for disinfection. The Guideline for Disinfection and Sterilization in Healthcare Facilities (CDC, 2008) is therefore consulted to further explain the meaning of various levels of disinfection as well as the effectiveness of multiple chemicals employed as disinfectants. The 2008 Guideline stated that in that low-level disinfectants can kill “most vegetative bacteria, some fungi, and some viruses in a practical period of time(≤10 minutes)”. While intermediate-level disinfectants might kill “mycobacteria, vegetative bacteria, most viruses, and most fungi but do not necessarily kill bacterial spores.” Chlorine products, also commonly referred to as household bleach, are “aqueous solutions of 5.25%-6.15% sodium hypochlorite”, have a “broad spectrum of antimicrobial activity”, are “fast-acting” and can “remove dried or fixed organisms and biofilms from surfaces”. “Higher concentrations (1,000 ppm) of chlorine are required to kill M.tuberculosis,” while concentrations as low as 100 ppm can be effective against some types of bacteria. Because household bleach contains “52,500 – 61,500 ppm available chlorine”, a 1:50 dilution provides in excess of 1,000 ppm of available chlorine, while a 1:200 dilution provides in excess of 250 ppm of available chlorine. Consequently, immersion in bleach solution diluted to 1:50 for 10 minutes is selected as a method for general intermediate-level disinfection. Unless the material is incompatible with sodium hypochlorite or cannot be immersed. For general low-level disinfection, saturation spraying of bleach solution diluted to 1:200 is employed. Sprayed items are given a minimum of 1 minute of exposure time. A list of disinfection protocols is shown in Table 1.
3. Incoming Cases
Incoming cases are handled in a receiving area separate from the production area. Only trained personnel are involved in the process and are directed to use appropriate protective equipment, including the wearing of a clean uniform, face mask, and gloves. Countertops and work surfaces are cleaned daily. All cases are disinfected as they are received. Impressions are rinsed to remove saliva, blood, debris, and other residue and disinfected by immersion in 2% Dentavon solution for 10 minutes as impression materials may not be compatible with sodium hypochlorite. Prostheses and other items that may not be compatible with sodium hypochlorite are similarly disinfected. Dentavon by Schülke is an aldehyde-free disinfectant based on active oxygen with an extensive spectrum of efficacy. The manufacturer claims that a 2% solution can deactivate tuberculosis bacteria as well as hepatitis B virus and HIV at a reaction time of 10 minutes. 100g of Dentavon contains 45g pentapotassium-bis(peroxymonosulphate)-bis(sulphate). Ethyl alcohol is rapidly bactericidal, tuberculocidal, fungicidal, and virucidal but does not destroy bacterial spores. 60%–90% solutions in water provide the optimum bactericidal concentration. Thus, articulators or other items that cannot be immersed are disinfected by wiping with 70-80% ethyl alcohol. Other items are disinfected by general intermediate-level disinfection.
4. Outgoing Cases
Outgoing cases are handled in a separate shipping area and cleaned regularly. Personnel responsible for performing the disinfection have received appropriate training and are instructed to wear appropriate protective clothing. All outgoing cases are cleaned and disinfected before being shipped to remove any debris or pathogenic microorganisms that came into contact with the case during processing. Prostheses are disinfected by immersion in Sporox II for 10 minutes as the materials may not be compatible with sodium hypochlorite. Sporox II by Sultan Healthcare contains 7.5% hydrogen peroxide and 0.85% phosphoric acid and is a sterilant and high-level disinfectant that claims to achieve high-level disinfection in 30 minutes. However, the Guideline for Disinfection and Sterilization in Healthcare Facilities (CDC, 2008) indicated that the mycobactericidal activity of this chemical mix “has been corroborated in a study showing the inactivation of >105 multidrug-resistant M. tuberculosis after a 10-minute exposure”. Therefore, immersion time was set at 10 minutes to achieve intermediate-level disinfection. Stone models, on the other hand, do not come into contact with the patient’s mucosa and thus carry a much-reduced risk of cross-infection. Given that, they are processed according to general low-level disinfection. After this, they are dried in the hot-air oven and cooled before being packaged to prevent mold formation. All other items are disinfected by general low-level disinfection. After disinfection, prostheses are placed back onto stone models where appropriate and placed in a plastic bag. All packaging materials used are new and disposable.
5. Recommendations for Dentists
The process adopted by MicroDental Laboratories eliminates many of the pathogenic micro-organisms on dental objects with the exception of bacterial spores. However, practitioners are recommended to consider sterilization or additional intermediate-level disinfection prior to insertion as to reduce the risks to patients to an absolute minimum.