Antimicrobials – antiseptics and disinfectants
- • Overview of sterilisation, disinfection and antisepsis
- • Antiseptics
- Root canal treatment medicaments
- Hand hygiene
- • Disinfectants
- Surface cleaning agents
- Instrument cleaning agents
- Impression and prosthesis disinfection
- • Specific agents
- Quaternary ammonium compounds
- Oxidising agents
- Essential oils
- • To understand the difference between sterilisation, disinfection and antisepsis
- • To understand the mechanism of action of agents used for disinfection and antisepsis
- • To be aware of the most effective agents for infection control in the dental surgery
Antiseptics and disinfectants are agents used to reduce the pathogenicity of microorganisms capable of causing infection. Antiseptics are used as medications in humans or animals, whereas disinfectants are used on inanimate objects or surfaces.
Antiseptics are commonly used in dentistry as mouthwashes, root canal medicaments, and hand hygiene products.
Disinfectants relevant to dental practice include those used to clean surfaces in the dental surgery and agents used for cleaning instruments.
It is important to understand the difference between the concepts of sterilization, disinfection and antisepsis. Sterilization implies the complete removal of all viable microorganisms, including viruses and spores. This requires the sustained application of high temperatures, chemicals and/or radiation. It is the highest level of cleansing that may be attained and is a requirement for the re-use of dental instruments, in order to prevent cross-infection in the dental practice setting.
Disinfection involves the use of chemicals to destroy the majority of pathogenic organisms on surfaces or objects. Disinfection leads to a reduction in pathogenicity but does not completely remove all microorganisms. It is not practical or possible to sterilize some objects in the dental surgery, such as benchtops, however it is well recognized that these objects do pose a risk of transmission of infection due to viable microorganisms being deposited on their surfaces via droplets, aerosols or direct contact from instruments or clinicians’ hands and gloves. Disinfection is a key component in the prevention of cross-infection in the dental practice setting.
Antisepsis refers to the use of chemicals to reduce the number of pathogenic organisms on a living surface, such as skin or oral mucosa. Antisepsis may be used to prevent the development of infection, assist in management of an active infection or to prevent cross-infection.
The use of antiseptics and disinfectants will be considered in turn. This will be followed by a consideration of individual agents.
The ideal qualities of an antiseptic are shown in Table 4.1.
Table 4.1 Ideal properties of an antiseptic
|• Active against a broad spectrum of pathogens, including bacteria, fungi, viruses and protozoa|
|• Cidal (killing) as well as static (limiting the growth of organisms)|
|• Capable of destroying spores|
|• Non-toxic and non-irritating to tissues|
|• Rapid onset and long duration of action|
|• Chemically stable, non-staining|
|• Acceptable smell and taste|
|• Active even in the presence of bodily oils, fluids, blood and other exudates|
|• Low cost|
Antisepsis in dentistry involves a variety of different indications. Hand hygiene is aimed at reducing the number of pathogenic organisms on the hands of dental clinical staff, as part of standard infection control precautions to reduce the risk of cross-infection.
The use of antiseptic mouthwashes is indicated for situations in which it is important to try to prevent infection, as well as part of treatment for an active infection. Antiseptic mouthwashes can form part of periodontal treatment as well as the management of other types of oral infective processes, including fungal and bacterial infections.
Concern has been raised about the high alcohol content of many mouthwashes and the possibility that this may be carcinogenic. Alcohol-free mouthwashes are widely available.
Antiseptic chemicals are often used as part of root canal treatment protocols, in order to reduce the number of viable bacteria in an infected root canal and reduce the risk of ongoing symptoms or infection.
The use of antiseptics in the oral cavity is affected by the presence of biofilms. Biofilms are an organized structure consisting of bacteria and extracellular material produced by bacteria, within which organisms may exist in a protected environment. This has implications for the efficacy of antiseptic agents as they may not be able to reach the most pathogenic bacteria, which exist deep within the biofilm. Various chemical properties of antiseptics have been trialled in an attempt to disrupt and penetrate biofilms for better antiseptic activity.
Mouthwashes used in dentistry include a variety of antiseptic agents, such as chlorhexidine, essential oils (menthol, thymol and eucalyptol) and cetylpyridinium chloride. Hydrogen peroxide is also available as a mouthwash.
Chlorhexidine is available in 0.12% and 0.2% mouthwash formulations, as well as a toothpaste and gel formula. Chlorhexidine mouthwash has excellent substantivity on the oral mucosa (up to 12 hours). It will inhibit the formation of plaque in a clean mouth, and as such is a useful adjunct to mechanical oral hygiene practices. It can also be useful in the symptomatic management of oral mucosal disorders.
Essential oils are used in proprietary mouthwashes such as Listerine, and their antimicrobial activity is due to their ability to damage cell membranes, causing leakage of cell contents and cell lysis. They also inhibit bacterial enzymes and are able to penetrate biofilms and inhibit plaque formation. Some essential oils also have anti-inflammatory activity. The essential oils eucalyptol, thymol, methyl salicylate and menthol have been utilized in combination with alcohol as a mouthwash formulation.
Cetylpyridinium chloride is a quaternary ammonium compound used in some mouthwashes. Its mechanism of action is similar to chlorhexidine in that it is cationic and binds to bacterial cell membranes, causing membrane disruption and cell lysis.
Hydrogen peroxide produces free radicals which can attack microbial membranes, DNA and other cellular components. It has a wide spectrum of activity against fungi, bacteria, viruses and spores. Hydrogen peroxide 1.5% is available as a mouthwash and is particularly effective against anaerobic bacteria, due to the oxygen released as it degrades.
Root canal treatment medicaments
Sodium hypochlorite (bleach) is commonly used as an irrigation agent during root canal therapy. It is toxic to living tissues and able to dissolve organic material. It will cause significant irritation if extruded beyond the apical area of the tooth.
Chlorhexidine has also been used as a root canal irrigant and in its gel form, as a root canal dressing.