An overview of the active ingredients used in dental disinfectants

As stated in Ministerial Decree 135/90 of 15 December 1990, “The prevention of infectious diseases is an ethical and moral duty, but it is also a precise legal obligation” (1).

In clinical practice, the management of practice hygiene and thus of infectious risk is therefore a de facto obligation incumbent upon the dentist and also upon the employees who perform this task. To achieve this prevention, dentists and all those acting on their behalf must know and be trained in the hygiene, disinfection and sterilisation practices to be implemented in the dental surgery/outpatient clinic.

Risk of cross-infections in the field of dentistry

Cross-infections are considered to rank among the major healthcare-related complications; they affect 5-10% of hospitalised patients, incurring an estimated annual cost of about $4.5 billion in the United States (2).

In a dental care setting, it is difficult to provide an estimate for this, but the risk of cross-infection is nonetheless present (3). It is present not only between healthcare staff and patient, but also from one patient to another and may even involve the dental technician, associates and/or technical support staff who visit the practice occasionally (4).

Disinfection in dental surgeries

Certainly one of the most widely used, but not the only method of preventing infection in dental surgeries is disinfection. Disinfection is defined as the process of removing microorganisms, including potential pathogens, from the surfaces of inanimate objects (5,6).

In fact, it is well known that a great many pathogens can be transmitted from host to host not only directly but also via surfaces or instruments in the environment. Numerous biofilms can be created and persist in these areas for quite some time until removed by active intervention, whether physical, chemical or both (7).

Importance of chemical action

Mechanical cleaning action certainly plays an important role, but it needs to be assisted by useful chemical action that can totally eliminate microorganisms and prevent the recolonisation of surfaces.

The effectiveness of a disinfectant depends on the degree of action of its active ingredients and the type of microorganism on which it must act (8). Disinfectants can be sporostatic, but are not necessarily sporicidal, since many of them do not kill spores (9).

Main types of dental disinfectants

In fact, there are “high”-, “intermediate”- or “low”-level disinfectants based on the potency of the disinfectant.
“High-level” disinfectants are those active across the entire microbial spectrum except for dealing with spores when present in high concentration.

Some of these disinfectants, when used in appropriate concentrations and for long contact times of 6-10 hours, are also capable of destroying spores and are classified as disinfectants/sterilisers (glutaraldehyde-based disinfectants, peracetic acid) (10).

Active ingredients such as chlorine dioxide, polyphenols and chloroderivatives are “intermediate level” and act on almost all microorganisms except spores.

Then there are other “low-level” active ingredients such as quaternary ammonium salts and chlorine derivatives at a Cl concentration < 100 ppm, which are capable of killing most bacteria, some fungi and viruses, but not resistant microorganisms such as tuberculosis mycobacterium or spores.

Antimicrobial mechanisms of dental disinfectants

Almost all of these active ingredients are found to be active primarily against the external surface (wall/capsid/cell membrane) of microorganisms but are inactive within them (9).

Perforation of the outer coating or changes induced by interaction with surface proteins generate therefore a significant effect on the microorganism’s osmotic balance, which ultimately leads to its death (9).

Moreover, some disinfectants have different antimicrobial mechanisms depending on the type of microorganism they come into contact with. For example, glutaraldehyde is active against a large number of microorganisms:

• In the presence of bacterial spores, low concentrations of glutaraldehyde inhibit germination, while high concentrations can be sporicidal, probably as a consequence of interaction with the outer cell layers. However, penetration capacity also depends on the type of glutaraldehyde (more or less acid/alkaline), which may or may not facilitate penetration of the spore’s inner layers (11);
• In mycobacteria, glutaraldehyde has an action that is still partly unknown, but probably involves attacking the mycobacterium’s cell wall (12);
• In Gram+ and Gram- bacteria, glutaraldehyde reacts by cross-linking with the amino groups of surface proteins, thereby going on to inhibit the transport processes from outside to inside the cell, and the enzymatic systems in charge of reacting with various substrates (9);
• Against fungi, on the other hand, glutaraldehyde interacts primarily with the fungal cell wall’s chitin, in an action similar to that against the peptidoglycan in the bacterial wall (13);
• Glutaraldehyde is a potent virucide. Its action appears to be geared towards the formation of cross-links with capsid proteins and with viral DNA, inhibiting their synthesis (14).

Despite its excellent efficacy profile, the use of glutaraldehyde has been gradually abandoned nowadays due to its low safety profile: in fact, it has a strong irritant effect on the ocular and nasal mucous membranes and is a mild skin irritant, showing possible signs of sensitisation.

Moreover, the most recent studies seem to rule out mutagenic and carcinogenic effects, but central nervous system changes and fetotoxicity have been described in animals.

Which disinfectant to choose in a dental surgery

In conclusion, disinfection is an essential practice in preventing cross-infection in dental surgeries. An appropriate disinfectant should always be chosen according to the characteristics of the surfaces to be treated, the procedures adopted within the facility and the level of efficacy required and guaranteed by the disinfectant within its stated spectrum of action.

The proper use of high-, intermediate-, or low-level disinfectants, along with mechanical cleaning practices, reduces the risk of contamination, protecting all who work and receive treatment in the dental care setting.

Zeta Hygiene by Zhermack is a complete range of cleaning and disinfection products for dental surgeries, which are free of aldehydes and phenols – toxic substances – and do not cause any damage to dental surgery and laboratory instruments and surfaces.

Innovative solutions, subjected to stringent production standards, monitored and tested in accordance with the most recent European regulations. Its rapid action, ease of use and high compatibility with materials make Zeta Hygiene the ideal solution for the most demanding professionals, guaranteeing excellent safety and absolute protection for users and patients.

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References

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