Application of nanotechnology to dentistry: Impact of graphene nanocomposites on clinical air quality

Abstract

Concerns about air quality in dental clinics where aerosol generation during procedures poses significant health risks, have prompted investigations on advanced disinfection technologies. This editorial describes the strengths and limitations of ventilation and aerosol control measures in dental offices, especially with respect to the use of graphene nanocomposites. The potential of graphene nanocomposites as an innovative solution to aerosol-associated health risks is examined in this review due to the unique properties of graphene (e.g., high conductivity, mechanical strength, and antimicrobial activity). These properties have produced promising results in various fields, but the application of graphene in dentistry remains unexplored. The recent study by Ju et al which was published in World Journal of Clinical Cases evaluated the effectiveness of graphene-based air disinfection systems in dental clinics. The study demonstrated that graphene-based disinfection techniques produced significant reductions in suspended particulate matter and bacterial colony counts, when compared with traditional methods. Despite these positive results, challenges such as material saturation, frequency of filter replacement, and associated costs must be addressed before widespread adoption of graphene-based disinfection techniques in clinical practice. Therefore, there is need for further research on material structure optimization, long-term safety evaluations, and broader clinical applications, in order to maximize their positive impact on public health.

Key Words: Graphene; Nanocomposites; Antibacterial activity; Biomedical applications; Air disinfection

Core Tip: This editorial highlights the potential of graphene nanocomposites as a transformative solution for improving air quality in dental clinics. By leveraging graphene’s unique properties, including its antimicrobial activity and high adsorption capacity, these materials offer significant advantages over traditional air purification systems. The study by Ju et al demonstrated the effectiveness of graphene-based air disinfection, paving the way for its broader adoption in clinical practice. However, challenges such as cost, material saturation, and long-term safety must be addressed through continued research to optimize its application in dental and other medical environments.

INTRODUCTION

The primary factor that contributes to air pollution in dental offices is the use of aerosol-producing instruments such as high-speed handpieces. These instruments which are often used by dentists, may harbor microorganisms from the oral cavity, upper respiratory tract, and possibly blood. During dental procedures, tiny particles are released into the air where they remain suspended briefly before settling on surfaces as well as the respiratory tract, skin, and eyes of both patients and dentists. On the other hand, larger particles tend to settle more quickly on environmental surfaces such as furniture or clothing[1]. In the dental office, microorganisms on surfaces may become re-suspended in the air, or transferred to the hands of the dentist and the patient, in addition to transfer to objects and environmental surfaces[2]. Additionally, increases in colony-forming units have been reported in dental offices, particularly around air inlets and outlets[3].

Bacteria are present in any area of the buccal cavity. However, saliva is the key route of bacterial distribution and dentification in the oral cavity. The most prevalent microorganisms in saliva are Streptococcus, Neisseria, Rothia, Prevotella, Actinomyces, Granulicatella, Porphyromonas, Haemophilus, and Porphyromonas species[4]. In the study carried out by Shanmugaraj and Rao[5], it was observed that, in the atmosphere of dental offices, Staphylococcus is one of the most common bacterial isolates, followed by Micrococcus, Diphteroids and Aspergillus species[5]. Water activates the discharge of bacteria by acting as the main aerosol generator. Various studies have evaluated air quality, with focus on the quantity of suspended microorganisms[6-10].

The need to implement air disinfection technologies in dental offices has become increasingly important due to the coronavirus disease 2019 (COVID-19) pandemic. The severe acute respiratory syndrome coronavirus 2 virus is primarily transmitted through aerosols and saliva droplets which are spread when talking, sneezing, or during dental procedures[11]. During the COVID-19 pandemic, various patient care measures were implemented in order to prevent cross-infection. These measures comprised adjustment of staff schedules, limitation or postponement of non-emergency appointments, enhancement of environmental disinfection protocols, and usage of online consultation services[12].

Due to the generation of aerosols during clinical procedures, the Dentistry profession faces significant air pollution risks as a result of dispersal of small particles, including particulate matter (PM_2.5), into the air. These particles have particle size of 2.5 μmol/L, and they readily bind to toxic substances such as microorganisms, polycyclic aromatic hydrocarbons (PAHs), and heavy metals[13-16]. Studies have shown that PM_2.5 concentrations are relatively high in dental clinics[17]. The United States Environmental Protection Agency (USEPA) standard stipulates that the maximum allowable concentration of suspended particles in the air is 35 μg/m³. However, several studies have shown levels of PM_2.5 above the standard average. In a study in which PM_2.5 levels were determined in the clinic and waiting room, Hsu et al[17] found high concentrations of benzo (b) fluoranthene, benzo (k) fluoranthene, benzo (a) pyrene, and indenopyrene, with significant differences in levels of benzo (b) fluoranthene and benzo (k) fluoranthene between the clinic and waiting room. Furthermore, after using an air purifier, the concentration of benzo (b) fluoranthene was decreased.

To minimize exposure to PM_2.5 and other aerosols in the dental office, adequate ventilation and aerosol control measures must be implemented. In recent years, attempts have been made to implement measures for maintenance of air quality in dental offices using mechanical ventilation systems, natural aeration, air purifiers with high efficiency particulate air (HEPA) filters, and extraction hoods[18]. However, many of these methods have considerable limitations such as high airflow resistance, risk of secondary contamination, and limited capacity for adsorption of multiple contaminants[17,19].

A promising solution with potential to set new standards for air purification in dental clinics is the use of graphene nanocomposites. As shown in Figure 1, graphene is a remarkable two-dimensional material composed of a single layer of carbon atoms arranged in a hexagonal lattice[20]. It is remarkable for its exceptional conductivity, strength, and large specific surface area. While its use in air purification is not new, its application in dental environments has been limited[13].

Figure 1 Graphene structure. Graphene is a material with molecular structure of a two-dimensional crystal organized in a hexagonal network like a honeycomb, with the thickness of one atom. It is made up of carbon atoms and covalent bonds. Each carbon molecule bonds to 3 carbons. C: Carbon.

It has been demonstrated that addition of graphene to polymer matrices greatly enhances the gas barrier characteristics of the resultant nanocomposites. For example, research suggests that graphene forms wavy channels in polymer membranes, thereby improving the effectiveness of removal of contaminants and hazardous compounds from air mixtures[21]. This feature is beneficial in clinical settings where preservation of air quality is essential for the safety of patients. Graphene is an excellent option for air purification applications because its dual properties allow it to act as a barrier against pollutants while facilitating gas diffusion[22,23]. Additionally, graphene-based nanocomposites possess excellent mechanical and thermal properties that are useful in the design of long-lasting air filtration systems. Studies have shown that addition of graphene to polymeric materials improves their thermal stability and mechanical strength, thereby extending the life and efficiency of air filtration devices[24,25].

This editorial was aimed at offering a balanced perspective on the potential impact of graphene nanocomposites on air disinfection in dental clinics.

VENTILATION AND AEROSOL CONTROL MEASURES IN DENTAL OFFICES

In a dental office, the maintenance of high air quality is crucial for ensuring the safety of both patients and healthcare personnel. Aerosols and other contaminants generated during clinical procedures elevate the risk of transmission of infectious diseases and respiratory complications. To mitigate these risks, it is essential to implement an air quality system tailored to the specific needs of the dental clinic. The available options are air purifiers, advanced ventilation systems, HEPA filtration systems, ultraviolet technology (UV), and graphene nanocomposites[26,27].

The air purifier system is designed to filter particles, microorganisms, and other contaminants from the air, through the use of mechanical filters and, in some instances, ionization or UV light to disinfect the air. These air purifiers, particularly those fitted with HEPA filters, are very effective at capturing small particles such as bacteria and viruses. Additionally, air purifier systems are easily movable to various areas of the office. However, the capacity of these devices depends on the size of the room and their airflow-handling capacities. Therefore, a single purifier may not be enough in a large area. Filters are often replaced regularly to maintain effectiveness, a requirement which incurs additional costs and often leads to generation of annoying noise[26,27].

The enhanced ventilation system focuses on increasing air renewal in the office space by introducing fresh air and expelling stale air. This method dilutes the contaminants present in the indoor air by increasing the outdoor air intake, thereby improving air freshness in the environment. However, it requires significant structural modifications and considerable investment. Ventilation with outside air increases heating or cooling costs, which could be an economic disadvantage[26,27].

Heating, ventilation, and air conditioning (HVAC) systems with HEPA filters offer advanced filtration that captures particles of size as small as 0.3 microns. These filters ensure that all recirculated air is clean and free of toxic particles. On the other hand, the installation of HEPA filters in HVAC systems is expensive, particularly in areas that require additional space and areas that do not have a previously installed HVAC system[26,27].

The UV technology has a long history of use in air disinfection, and it has been proven effective in inactivating a wide range of microorganisms, including bacteria, viruses, and fungi[27]. This radiation technique penetrates the cells of bacteria, viruses, and fungi, and is absorbed by DNA and RNA. This energy absorption causes the formation of thymine dimers which distort DNA structure and interfere with cell replication, leading to the inactivation of the microorganism. These qualities make it a valuable tool for air disinfection in dental offices[27,28]. However, since UV radiation is harmful to the skin and eyes, there is need for provision of safety measures to protect staff and patients[27].

Graphene nanocomposites are innovative materials made by combining graphene with other elements so as to improve its properties, and they have been applied in air quality systems[13,14,28,29]. Graphene is a two-dimensional material characterized by excellent thermal and electrical conductivity, high mechanical resistance, large specific surface area, and antimicrobial properties[13,29]. This material is incorporated into air quality systems in filters or on surfaces for efficient capture of fine particles, bacteria, viruses, and other air pollutants. These systems are highly durable, and they remain effective for long periods without the need for frequent replacement. Additionally, graphene-based systems have a high adsorption capacity, which means that they remove various contaminants such as particles, volatile organic compounds (VOCs), and other gaseous pollutants from the air, thereby significantly improving indoor air quality[13,15,29]. Therefore, air purification systems may be made more effective by incorporating graphene-based materials because of their large surface area and adsorption capacity which allow them to adsorb and neutralize airborne pathogens[27].

GRAPHENE NANOCOMPOSITES AND ANTIMICROBIAL PROPERTIES

Graphene nanocomposites have remarkable mechanical improvements and remarkable antimicrobial properties. The antimicrobial mechanism of graphene effectively kills pathogens by physically and chemically disrupting bacterial membranes and producing reactive oxygen species[30].

These characteristics reduce the chance of formation of biofilms on dental surfaces, which is especially helpful in preventing infections linked to dental procedures and materials. Research has demonstrated that graphene oxide and graphene nanoplatelets exhibit noteworthy antibacterial effects against prevalent oral pathogens such as Porphyromonas gingivalis and Streptococcus mutans[31,32].

Another vital consideration in the choice of dental materials is biocompatibility, particularly for those that come into direct contact with oral tissues. It has been demonstrated that materials based on graphene improve cell adhesion and proliferation, thereby making them suitable for use in regenerative dentistry and tissue engineering. For instance, graphene oxide has been shown to enhance the expressions of genes related to osteogenesis and odontogenicity in dental pulp stem cells, indicating its potential for use in regenerative medicine[33,34]. Moreover, research has shown that graphene composites efficiently enhance the differentiation of stem cells from the periodontal ligament into osteoblast-like cells, which is necessary for bone regeneration[34].

Due to its adaptability, graphene is suitable for use in various dental applications such as implants, composites, and adhesives. Graphene-based dental adhesives have been developed for enhanced mechanical properties and anti-biofilm activity, thereby extending the lifespan and efficacy of dental restorations[32,35,36]. Furthermore, the capacity of graphene for functionalization with bioactive molecules creates new opportunities for developing cutting-edge dental materials that actively enhance tissue integration and healing[37].

The usage of graphene in dental materials goes beyond consideration of its antibacterial qualities. It has been shown that graphene-enhanced composites have improved mechanical qualities such as high tensile strength and durability. These qualities are critical for materials used in high-stress situations, e.g., dental restorations[38]. Graphene is a desirable alternative for dental applications due to its biocompatibility and mechanical and antimicrobial properties. Research has demonstrated that the integration of dental implants with surrounding tissues depends on the capacity of graphene and its derivatives to enhance cell adhesion and proliferation[39]. Moreover, graphene may be used with current technologies to manage air quality in dental offices. For example, it has been shown that the combination of graphene-based air purification systems with conventional HVAC systems efficiently removes pathogens and particulate matter from the air, thereby improving indoor air quality[40]. This integrated approach is beneficial to the general health and well-being of patients and the dental staff, and it improves the safety of dental procedures.

In the recent 2024 issue of the World Journal of Clinical Cases, Ju et al[41] published an interesting original paper. In the study, the effectiveness of the implementation of graphene nanocomposites as a method of air disinfection in dental clinics in order to reduce secondary contamination produced by aerosols during dental procedures, was evaluated. Sixty patients were randomly divided into three groups. A suction device with graphene nanocomposites was used in group A. In group B, a suction device with an ordinary filter was used, while no suction device was used in group C. The methodology consisted of measuring air quality levels (in terms of PM_2.5) and the count of bacterial colonies in the rooms before, during, and after ultrasonic cleaning treatment. Additionally, samples of the number of colonies were taken in the exhaust ports of the suction devices and on the surfaces of the filters. During and after treatment, group A showed significantly better air quality (lower PM_2.5) and lower colony counts than group B or group C. The colony counts in the exhaust port of the device and on the filter surface were significantly lower in group A than in group B. This research demonstrated that graphene nanocomposites have great potential for application in air disinfection in dental clinics, and they present an efficient solution to the transmission of pathogens in these environments, without secondary contamination[41]. On the other hand, in the study by Hsu et al[17], air quality was evaluated in the dental department of a hospital, with focus on the concentrations of suspended particles (PM_2.5) and VOCs, particularly the composition of PAHs and metals present in the particles. Additionally, the Blueair 480i air purifier was used to reduce the concentrations of contaminants in the air. A gravimetric method was used for determination of the final concentration of PM_2.5, while the compositions of PAHs and metals were measured using gas chromatography coupled to mass spectrometry and inductively-coupled plasma mass spectrometry, respectively[17]. The findings showed high concentrations of PM_2.5 in excess of the USEPA standards. The concentrations of PM_2.5 ranged between 41.08 μg/m³ and 108.23 μg/m³ in the dental clinic, while in the waiting room, they ranged from 17.89 μg/m³ to 62.72 μg/m³. These values exceed the air quality guidelines established by the WHO. In addition, high levels of priority PAHs such as benzo (b) fluoranthene, benzo (k) fluoranthene, and benzo (a) pyrene, were identified. These substances are recognized for their carcinogenic potential, and were present at significantly higher concentrations in the dental clinic than in the waiting room. Several metals were present. The presence of lead in higher concentrations in the dental clinic is particularly worrying due to its neurotoxicity, even at low levels. There was a significant reduction in the concentration of benzo (b) fluoranthene in the dental clinic. This demonstrated the effectiveness of the purifiers in improving air quality in this environment. Despite the valuable findings presented by Hsu et al[17], one of the most important limitations of the study its sole focus on measuring PM2.5, PAHs, and certain metals, without considering other possible air pollutants such as bioaerosols, microorganisms, and nanoparticles generated during dental procedures. The study by Ju et al[41] highlights the relevance of monitoring and regulating air quality in dental areas, given the high concentrations of PM_2.5. Likewise, it emphasizes the need to consider appropriate air quality regulations in dental clinics so as to ensure a safe work environment. Therefore, future research should focus on the effectiveness of different methods in improvement of air quality in these spaces.

Graphene and UV technology have been presented as promising alternatives for air purification in dental offices[26,27]. However, the UV system has a broader history of use, and it has been tested against a more diverse range of microorganisms[27]. On the other hand, graphene offers the added benefit of particle adsorption which improves overall air quality[27,41]. While graphene is generally considered safe for use in biomedical applications, UV technology poses a potential health risk due to radiation exposure. However, it is cheaper to implement UV systems than graphene techniques, especially in terms of initial costs. On the other hand, long-term operating costs may vary, depending on the maintenance required for each technology[26,27,41].

Graphene nanocomposites present an advanced and effective solution for improving air quality in dental offices. Its characteristics of high filtration efficiency, durability, and antimicrobial properties offer advantages over traditional systems. On the other hand, this nanotechnology also presents certain limitations such as adsorption saturation, effect on the different graphene layers, challenges in installation, and cost and long-term viability considerations. A relevant aspect that must be kept in mind is the adsorption saturation of grapheme. This material has adequate filtration performance in the stable stage. However, its dust holding capacity is limited, when compared to other materials. Thus, there is need for frequent replacement of the filter material. Research has so far been focused on single-layer graphene. Therefore, there is need to investigate the bacteriostatic effects of different layers of graphene. Although the application of graphene nanocomposites in suction filters has produced promising results, there are still challenges associated with installation on ceilings and walls where most aerosols are deposited. Large-scale production of graphene nanocomposites with suitable characteristics for air purification is expensive. Therefore, the feasibility and viability of application of graphene nanocomposites in dental offices will depend on the profitability and durability of these materials.

PERSPECTIVES FOR FUTURE RESEARCH

The effectiveness of graphene in air disinfection in the dental clinical area has opened the door to several important directions for future research around the development of graphene nanocomposites, with potential significant impact on clinical practice and public health.

Several studies have demonstrated the effectiveness of graphene nanocomposites in air purification. However, it is essential to continue investigating the optimal structures and compositions of these materials. It would be interesting to explore the capacities of materials with three-dimensional structures to increase dust retention capacity and enhance the continuity of the filtration process. For graphene technology to be implemented in the clinical environment, it is necessary to evaluate the adsorption saturation of graphene. Knowledge of the precise moments at which materials reach their maximum adsorption capacities will optimize replacement cycles and maintain filtration efficiency without significantly increasing operating costs.

One area of research that is necessary concerns investigation on the effectiveness of graphene nanocomposites on various dental clinic surfaces such as ceilings and walls where aerosol deposition is high. This could be achieved by implementing electrospinning technology which will allow for the application of graphene in critical areas, thereby increasing air quality and reducing cross-contamination. In this context, one crucial area of research is the expansion of the clinical scope of graphene nanocomposites to other areas of medicine such as operating rooms or intensive care units, where air quality is critical for preventing nosocomial infections.

The antimicrobial benefits of graphene have been widely documented. However, it is crucial to conduct long-term studies to evaluate its safety and toxicity, particularly regarding chronic exposure of patients and clinical staff to graphene particles. These investigations are essential in order to ensure that prolonged use of these materials does not cause adverse health effects.

Although graphene nanocomposites show great potential in air disinfection in dental clinics, it is essential to continue multidisciplinary research that should focus on optimizing the materials, understanding their long-term performance, and exploring applications in different clinical contexts.

CONCLUSION

The use of graphene nanocomposites is a promising innovation in air disinfection in dental clinics, as it offers a novel method for mitigating secondary contamination caused by aerosols during dental procedures. This air quality enhancer system provides an advanced and efficient solution to aerosol-associated contamination due to its antimicrobial properties, high adsorption capacity, and durability. However, before it is widely adopted, it is crucial to investigate its long-term safety and impact on health, and to optimize its performance in different clinical contexts. As research and development continue, this technology may become a standard in preventing infections and improving clinical safety.