Self-disinfecting surfaces: The possibility of a better method
By Madisen Bunch; Laura Reyes; Savanna Sam; and Brandy Cowen, MS, RDH
When evaluating the current standard methods of disinfection, researchers identified that fewer than 50% of hospital surfaces can be considered clean after disinfection procedures, and 94.3% of health-care workers do not wash their hands for more than 15 seconds.1 Research suggests that current protocols are not meeting the recommended bacterial load of 250 CFU/cm2, which may be contributing to the current incidence of hospital-acquired infections (HAI).2 These standards are recommended by the Centers for Disease Control and Prevention (CDC). While the CDC is not a regulatory agency, the dental board state laws and practice acts could adopt the standard and enforce the recommendation in the future. Due to these reasons, researchers have been evaluating self-disinfecting surfaces in order to help maintain the recommended bacterial load.
Using biomimicry for self-disinfecting
Self-disinfecting surfaces can be defined as a technology that has the ability to kill and disable microbes on contact.3 Metals, in particular, such as copper alloy, release reactive ions that invade the bacteria’s cell wall, resulting in the destruction of DNA.3 In addition to the method of self-disinfection, biomimicry may also play a role in the future of disinfection. Biomimicry is a broad area of research that involves studying and incorporating aspects of nature to solve modern problems.1 For example, Velcro was inspired and designed based off of the burdock plant. Another example of biomimicry is the technologies that have been developed based off of the footpads of geckos that enable them to climb vertically. By mimicking the hairs on geckos’ feet, scientists were able to create foot pads that enable humans to climb vertically by creating adhesion force.
The study of biomimicry has recently uncovered a possible new method of disinfection through the study of shark skin. It was discovered that shark skin has a microtopography that prevents the attachment of microbes. This finding has led to new technologies that are being developed for possible use in clinical settings. The literature focuses on the efficacy of antibacterial and antifouling (the inability of microbes to adhere to the surface, causing them to starve and die) properties from biomimetic surfaces in the health-care setting.4 Biomimicry offers a possible solution to meeting current infection control standards.
While biomimetic surfaces in dental clinics have not yet been utilized, the idea of biomimicry is not new to the dental field. The use of biomimicry in titanium dental implants has been discussed since the 1950s.5 Titanium is known for its self-disinfecting properties, which prevent bacterial adhesion and therefore decreases implant failure.6 Additionally, hospitals are starting to utilize metallic surfaces such as copper and microtopography technology to help reduce HAI.2 Copper has been used in medicine for many decades and is known for its antibacterial properties.6
Although contact-killing cannot destroy bacteria completely, it is proven effective at reducing large amounts of various bacteria, which include gram-positive and gram-negative bacteria as well as nonenveloped viruses.7 Studies have demonstrated that copper, in combination with current EPA-registered intermediate disinfectants, has a synergistic relationship without compromising the antimicrobial properties but still further limiting bacterial populations.7 There are several different concentrations of copper impregnated into surfaces that are currently available.8 Surfaces with higher concentrations of copper alloy have shown the greatest antimicrobial efficacy.3
Shark skin and copper in the dental office
Another self-disinfecting surface being studied is the newly engineered biomimetic surface “shark skin,” which modifies surfaces to prevent bacterial adhesion.4 This technology is a plastic material that has been imprinted with a microtopography that mimics the epidermis of a shark.4 This microtopography includes a rectangular base with tiny spines located on the surface.1 Shark skin has antibacterial properties that prevent bacterial adhesion due to lack of surface area and is therefore antifouling.1 The lack of surface area means that microbes are unable to effectively attach and colonize, thus preventing biofilm formation.1 In a primary research study, titanium dioxide was added to the shark skin due to its ability to induce cell lysis.4 This shark skin infused with titanium dioxide acts in both passive and active ways by preventing bacterial adhesion and killing any bacteria that may accumulate over time.4 Titanium dioxide was added because, while the lack of surface area prevents bacterial adhesion, bacteria multiplies so rapidly that it would not be possible to fully prevent the total accumulation of bacterial load for an indefinite amount of time.4 Therefore, shark-skin technology may require adjunctive measures to increase antibacterial properties.
Research demonstrates that the most common method of transmission is through infectious particles that have settled on surfaces.9 The aerosols produced commonly in dental settings are due to various instruments producing spatter and a consistently open oral cavity. This allows for an accessible portal of entry and exit, which is part of the chain of infection.10 With the implementation of copper and “shark skin,” the chain of infection could be disrupted, thus preventing portal entry and exit. For example, Staphylococcus aureus remains on surfaces from seven days to seven months.11 Mycobacterium tuberculosis can remain on surfaces for up to six months under the right circumstances (kept away from direct sunlight).12 Candida albicans, a common fungus in the dental setting, can live on a surface for one to 120 days.11 By introducing self-disinfecting technology, the persistence of these bacteria among others can be significantly reduced.
In dentistry, the idea would be to implement copper alloy into high traffic areas such as countertops, handles, sinks, etc. The microtopography adhesives could be utilized as removable barriers to additionally protect hard-to-clean areas. This biomimetic surface contains a textured structure that reduces microbial adhesion through a biocide-free surface.4 These adhesives could be placed on light switches, computer mouses, and control panels.
Obstacles and concerns
One of the obstacles with implementation of self-disinfecting surfaces is the cost of these materials.8 When we evaluate the potential deduction in transmission of infectious agents, the one-time cost of installation of copper surfaces far outweighs the initial financial burden.8 Another concern with copper may be the appearance (discoloration due to corrosion) and its continued effectiveness over time due to a tarnished appearance.8 Studies demonstrate that copper does not lose its efficacy when tarnishing appears, and the rate of contact-killing remains consistent.6 There are more than 450 antimicrobial copper alloys that have a range of colors and rate of degradation if esthetics are a concern.8
Microtopography has been evaluated and questioned as to its need for replacing current practices. It can be argued that current disinfection methods are adequate if done properly, but research shows this is not being completed effectively.13 Not all bacteria are completely removed from surfaces that have been disinfected.13 If a minuscule amount of bacteria remains after disinfection, it will repopulate and exceed the recommended bacterial load.2 This is the reason self-disinfecting surfaces could be used effectively in dental settings.
Further evaluation needed
Even with present research, questions still remain and need to be addressed before implementation. Potential allergies to copper and possible adverse reactions in the general public remain unknown. It is necessary to determine the duration of contact with copper surfaces needed in order to elicit a reaction to determine if the benefit is greater than the probability of an inflammatory response such as contact dermatitis. In regard to microtopography technology, the research and production are still in their infancy and require further evaluation. There are limited companies that are producing supplies in low volume. In the future, greater demand for these materials could lead to more variation and accessibility.
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