WHEN CAN YOU ACTUALLY USE CHEMICAL FOR STERILIZATION? AND, WHAT ARE DIFFERENT KIND OF SOLUTIONS AVAILABLE?
The term chemical sterilization is a process of disinfection where instruments are exposed in the solution for a certain amount of time. The process starts when the items are left in the solution for the required time, typically 30 minutes to 6 hours or is applied directly to a specific item.
A device is considered sterilized when the disinfectant completely kills and removes microbial infecting agents. The ability of a disinfectant to deactivate a microbe depends on the mode of action of the chemical, the molecular structure of the pathogen's surface, and the intracellular vulnerability. Although, physical methods are often superior to chemical sterilization, some instruments are not practical to autoclave or be subjected to high temperature, especially if the items can be damaged through repeated exposure to heat.
On this article, let's discuss the types and modes of action of chemical sterilization in the practice modern dentistry. We need to identify them and the types of instruments we are dealing with. According to the Centers for Disease Control and Prevention, dental instruments are classified into three categories according on the risk of transmitting infection.
These are instruments used to penetrate soft tissue or bone, or enter into or will have possible contact with the bloodstream or other normally sterile tissue. These instruments should be sterilized after each use. The recommended sterilization is steam under pressure (autoclave). Other optional method of sterilization are dry heat and heat or chemical vapor. Critical instruments include forceps, scalpels, bone chisels, scalers, highspeed handpieces and burs.
These are instruments that do not penetrate soft tissues or bone but may come into contact mucous membranes or non-intact skin. These include mirrors, reusable impression trays, and amalgam condensers. These devices should also be sterilized after each use. In some cases, however, if sterilization is not feasible, high-level of disinfection maybe appropriate as an alternative option. A high-level disinfectant must be used on these instruments with a label of (EPA-Environmental Protection Agency) as a “sterilant/disinfectant”.
These are instruments that come into contact only with intact skin. These include the external components of x-ray heads, blood pressure cuffs, and pulse oximeters. Such devices have a relatively low risk of transmitting infection. Therefore, they may be reprocessed between patients by intermediate-level or low-level disinfection. An intermediate-level disinfectant is EPA-registered as a “hospital disinfectant” and will be labeled for “tuberculocidal” activity (e.g., phenolics, iodophors, and chlorine-containing compounds). A low-level disinfectant is EPA-registered as a “hospital disinfectant” but is not labeled for “tuberculocidal” activity (e.g., quaternary ammonium compounds).
TYPES OF CHEMICAL DISINFECTANTS
I. A. Aldehydes (Glutaraldehyde)
Is a type of disinfectant that acts as broad-spectrum biocidal. It is effective for sterilizing equipment, though to effect sterilization often requires many hours of exposure. Its biocidal action is through alkylation of carboxyl, hydroxyl and sulfhydryl groups on proteins which alters RNA, DNA, and protein synthesis.
2% of glutaraldehyde exhibit very good activity against vegetative bacteria, spores and viruses. It is 10X more effective than formaldehyde and less toxic. However, it must be limited and controlled because of its toxic properties and hazards it can cause. It is important to avoid skin contact with glutaraldehyde as it has been documented to cause skin sensitization. Glutaraldehyde is also an inhalation hazard.
Cidex, a commercially prepared glutaraldehyde disinfectant is used routinely for cold surface sterilization of clinical instruments. Glutaraldehyde disinfectants should always be used in accordance with the manufacturer’s directions.
B. Halogen-Based Biocides: (Chlorine Compounds and Iodophores)
➢ Chlorine Compounds
Chlorine compounds are good disinfectants on clean surfaces, but are quickly inactivated by organic matter, and, thus, reducing the biocidal activity. They have a broad spectrum of antimicrobial activity, inexpensive and fast acting.
The mechanism by which chlorine destroys microorganisms is through inactivation which results: oxidation of sulfhydryl enzymes and amino acids; ring chlorination of amino acids; loss of intracellular contents; decreased uptake of nutrients; inhibition of protein synthesis; decreased oxygen uptake; oxidation of respiratory components; decreased adenosine triphosphate production; breaks in DNA; and depressed DNA synthesis of the microorganism.
Hypochlorites, the most widely used of the chlorine disinfectants, are available in liquid (e.g., Sodium Hypochlorite), household bleach and solid (e.g., calcium hypochlorite, sodium dichloroisocyanurate) forms. Take note that chlorine based disinfectants can corrode or damage metal, rubber, and other susceptible surfaces.
Household bleach has an available chlorine content of 5.25%, because of its oxidizing power, it loses potency quickly and should be made fresh and used within the same day it is prepared. The efficacy of an opened bottle hypochlorite solutions in over a period of one month (at room temperature) are reduced to 40% to 50% of the original concentration.
There are two potential occupational exposure hazards when using hypochlorite solutions. The first is the production of the carcinogen bis-chloromethyl ether when hypochlorite solutions come in contact with aldehyde solutions. The second is the rapid production of chlorine gas when hypochlorite solutions are mixed with an acid. Care must also be exercised when using this solution.
Iodophors are used both as antiseptics and disinfectants. An iodophor is a combination of iodine and a solubilizing agent or carrier; the resulting complex provides a sustained-release reservoir of iodine and releases small amounts of free iodine in aqueous solution. The iodine acts by penetrating the cell wall of microorganisms disrupting the protein and nucleic acid structure and synthesis. Iodophors demonstrate bactericidal, mycobactericidal, and virucidal activity but can requires prolonged exposure to kill certain fungi and bacterial spores.
Wescodyne, Betadyne, Povidone-Iodine and other iodophors are commercially available Iodine-based disinfectants, which give good control when the manufacturer’s instructions for formulation and application are followed.
II. Quaternary Ammonium Compounds
Quaternary ammonium compounds are generally odorless, colorless, nonirritating, and deodorizing. They also have some detergent action, and they are good disinfectants. However, some quaternary ammonium compounds activity is reduced in the presence of some soaps or soap residues, detergents, acids and heavy organic matter loads.
In today’s time, quaternary compounds are active against coronaviruses at less than 1% concentration and within an exposure time of a minute or less. Basically these compounds is suitable for any type of disinfection.
The mode of action of these compounds is through inactivation of energy producing enzymes, denaturation of essential cell proteins, and disruption of the cell membrane. Many of these compounds are better used in water baths, incubators, and other applications where halide or phenolic residues are not desired. The popularity of quaternary is due to their ability to retain biocidal activity in the presence of anionic residues and hard water.
The quaternaries commonly are used in ordinary environmental sanitation of noncritical surfaces such as floors, furniture, and walls. EPA-registered quaternary ammonium compounds are appropriate to use for disinfecting medical equipment that contacts intact skin (e.g., blood pressure cuffs).
Phenolics are phenol (carbolic acid) derivatives. It acts through as a gross protoplasmic poison, penetrating and disrupting the cell wall and precipitating the cell proteins. Low concentrations of phenol and higher molecular-weight phenol derivatives cause bacterial death by inactivation of essential enzyme systems and leakage of essential metabolites from the cell wall. Phenol derivatives can deactivate viruses, such as HIV, and other hydrophilic viruses within minutes at a concentration range of 0.5–5%. These compounds deactivate pathogens floating into the area being disinfected.
The use of phenolic as disinfectants are applied on environmental surfaces (e.g., tables, dental chairs, and laboratory surfaces) and noncritical medical devices. Phenolics are not FDA-cleared as high-level disinfectants for use with semicritical items but could be used to preclean or decontaminate critical and semicritical devices before terminal sterilization or high-level disinfection.
Available commercial products are Lysol, Pine-Sol, Amphyl, O-syl, Tergisyl, Vesphene, L- Phase and Expose.
Alcohols work through the denaturation of proteins by acting directly on S-H functional groups , disruption of cellular membranes and solubilization of lipids. Ethyl and isopropyl alcohols are the two most widely used alcohols for their biocidal activity. These alcohols are effective against lipid-containing viruses and a broad spectrum of bacterial species, but ineffective against spore-forming bacteria. They evaporate rapidly, which makes extended contact times difficult to achieve unless the items are immersed.
The optimum bactericidal concentration for ethanol and isopropanol is in the range of 60% to 90% by volume where ethanol is superior to isopropanol against hydrophilic viruses, such as rotavirus, human immunodeficiency virus (HIV), and coronaviruses, while isopropanol is more active against lipophilic viruses, such poliovirus and hepatitis A virus (HAV). Their biocidal activity drops sharply when diluted below 50% concentration.
Alcohols are not recommended for sterilizing dental and other surgical materials principally because they lack sporicidal action and they cannot penetrate protein-rich materials. Postoperative wound infections with Clostridium may occurred when alcohols were used to sterilize surgical instruments contaminated with bacterial spores. Furthermore, alcohol occasionally is used to disinfect external surfaces of equipment.
HANDLING SAFETY PROTOCOLS
Wear your personal protective equipment (PPE), such as gloves, mask, and safety eyewear, and isolation gowns, lab coats, or aprons when working in the sterilization area. Think of these as standard precautions. Treat these chemicals like with caution. Everything in that room should be considered harmful. Ensure your assistant to have proper ventilation and always follow the manufacturer’s instructions for use.
Various chemical disinfectants are widely available and they provide an effective tool against bacterias, mycobacterias, fungi and even SARS-CoV viruses. Several of these chemical disinfectants are household chemicals, such as alcohols and hypochlorite solutions. They are inexpensive, easy to use and have low level of toxicity while showing excellent biocidal activity within a very short time. Other more specialized chemicals are used in medical facilities for thorough sterilization of medical devices and hard-to-reach surfaces. And, though, they are effective to protect us, proper use and handling must be followed to the letter according to the manufacturer's instructions to ensure they deliver the actual function we expect them to deliver. Moreover, the appropriate protective gear and strict protocol must also be observed in handling them to avoid any harmful effects towards our health safety and well-being.
Dr. Bryan Anduiza - Writer
Dr. Mary Jean Villanueva - Editor