Graphene as a promising material in orthodontics: A review

Abstract

Graphene is an extraordinary material with unique mechanical, chemical, and thermal properties. Additionally, it boasts high surface area and antimicrobial properties, making it an attractive option for researchers exploring innovative materials for biomedical applications. Although there have been various studies on graphene applications in different biomedical fields, limited reviews have been conducted on its use in dentistry, and no reviews have focused on its application in the orthodontic field. This review aims to present a comprehensive overview of graphene-based materials, with an emphasis on their antibacterial mechanisms and the factors that influence these properties. Additionally, the review summarizes the dental applications of graphene, spotlighting the studies of its orthodontic application as they can be used to enhance the antibacterial and mechanical properties of orthodontic materials such as adhesives, archwires, and splints. Also, they can be utilized to enhance bone remodeling during orthodontic tooth movement. An electronic search was carried out in Scopus, PubMed, Science Direct, and Wiley Online Library digital database platforms using graphene and orthodontics as keywords. The search was restricted to English language publications without a time limit. This review highlights the need for further laboratory and clinical research using graphene-based materials to improve the properties of orthodontic materials to make them available for clinical use.

Introduction

Carbon is extensively utilized in various scientific disciplines owing to its abundant presence and diverse structural configurations.[1] Nanomaterials made of carbon are currently receiving much attention in biomedicine.[2] Carbon nanomaterials can be categorized into various dimensional structures. Zero-dimensional structures (material with all X, Y, and Z dimensions in nanoscale levels) encompass carbon dots and fullerenes and one-dimensional structures such as nanotubes. Additionally, graphene represents a two-dimensional carbon structure.[3] Furthermore, a hybrid of carbon nano components gives rise to three-dimensional structures.[4]

Graphene is one of the strongest and thinnest materials that arise from single crystalline carbon arranged in a honeycomb pattern.[5,6,7] They possess unique mechanical, chemical, and thermal characteristics with high surface area and antimicrobial properties.[8] Graphene and its derivatives have many biomedical applications as they can easily be functionalized and modified, producing different graphene-based materials.[8,9,10]

Following their isolation in 2004, graphene and its derivatives have become a promising material for biomaterial research,[11] and the unique physical and chemical properties of graphene-based materials[12] attract their dental application.[13] They have been investigated in many fields and excessively researched for biomedical applications such as tissue engineering, drug delivery, and cancer treatment.[14] In recent years, with the advancement of properties of graphene-based material, they have been widely investigated in the field of dentistry.[15] The unique antibacterial and mechanical properties of graphene-based materials encourage researchers to investigate them in orthodontics. To date, there has been no review summary of their specific application in orthodontics.

In this review, we summarized the main graphene derivatives, the mechanism of their antibacterial properties and the factors influencing them. We further summarized their possible application in dentistry, application to enhance bone remodeling, and potential application in orthodontic materials including adhesive, archwire, and acrylic.

Information Sources, Search Strategy, and Study Selection

An electronic search was carried out in Scopus, PubMed, Science Direct, and Wiley Online Library digital database platforms using graphene and orthodontics as keywords. The search was restricted to English language publications without a time limit. A total of 524 publications were identified from PubMed (51), Scopus (20), Science Direct (320), and Wiley Online Library (133) databases. The removal of 14 duplicated studies resulted in 510 studies; among them 487 studies were excluded from the research after assessing the title and abstract (121 were not relevant to the topic, 181 review articles, 127 book chapters, 10 conference review articles, and 48 others). The remaining 23 studies were retrieved and screened by the first author, and this process resulted in the exclusion of 12 studies (4 were not available as full text and 8 were not relevant to the topic). One study was selected and added after screening the references of the selected studies. Therefore, this resulted in the inclusion of 12 studies in the current review [Figure 1]. Any concern regarding the selection of studies was resolved by discussion with the second author.

Figure 1.

Flow diagram for literature searches

Types of Graphene-Based Materials

The structures of graphene derivatives are similar; however, they have distinct physicochemical properties resulting from a slight structure variation.[16] They can be classified according to layer numbers, dimensions, and functional surface modification. In addition to single and few-layer graphene, they have two essential derivatives: graphene oxide and reduced graphene oxide.[15]

Graphene is a bi-dimensional, single-layer carbon-based hexagonal structure,[17] they are produced by the exfoliation of graphite as it represents their basic structure. Also, graphene can be deposited utilizing chemical vapor.[18]

Graphene oxide is a highly oxidative flake-like water-soluble graphene derivative with carboxyl, epoxy, and hydroxyl functional groups.[19,20] It is usually produced by the exfoliation of graphite oxide.[7] The partial reduction of the oxygen group from graphene oxide will generate reduced graphene oxide[21,22] with an intermediate structure between graphene and graphene oxide.[23] Additionally, graphene materials can be functionalized by physical or chemical processes utilizing the defect sites, and this can be achieved by nitrogen and fluorine atoms; also, functionalization can be performed with amino, hydroxyl, or carboxyl functional groups,[17] metal nanoparticles to produce graphene nanocomposite.[19] The physicochemical properties of graphene material can be enhanced with functionalization[24,25] [Figure 2].

Figure 2.

Structure of graphite and graphene-based materials

Proposed Antibacterial Mechanism of Graphene-Based Materials

Numerous graphene-based materials have antibacterial properties from different physical and chemical processes [Figure 3]. Besides minimizing bacterial adhesion,[26,27] these processes involve:

Figure 3.

Antibacterial mechanism of graphene-based materials

1. Membrane stress: The strong interaction between graphene-based material and lipid molecule[21,22] leads to the extraction of phospholipid from the bacterial membrane, destroying the bacterial cells while maintaining cell integrity.[26,28]

2. Oxidative stress: In the presence of bacteria, graphene material can produce reactive oxygen species (such as hydrogen peroxide, hydroxyl radical, or superoxide radical), which can destroy bacteria by the evolution of lipid peroxide as they contact bacterial membranes.[29] That leads to oxidation and degradation of different bacterial parts including nucleic acid, protein, and membrane components,[26,30] and reducing their proliferation ability.[31]

3. Electron transfer: Graphene behaves as an electron receptor, extracting electrons from the bacterial membrane and damaging their integrity.[5,28]

4. Wrapping isolation: Graphene sheets can surround the bacteria, isolating them from their growth media and preventing the crossing of nutrients to bacteria and subsequent inhibition of their growth.[32,33] This antibacterial mechanism is reversible, and the viability can be recovered by bacterial separation from graphene materials.[34]

5. Nano knife effect: Bacterial damage can occur by direct contact of bacteria with the sharp edge of graphene layers,[30,35] damaging the bacterial wall integrity and leading to leakage of cellular content,[36] such as protein, phospholipids, ribonucleic acid (RNA), and deoxynucleic acid (DNA).[30]

Factors and Circumstances Determining the Antibacterial Properties of Graphene-Based Materials

The biomedical research community has recently shown considerable interest in the antibacterial properties of graphene and their derivatives,[37] many researchers evaluated the antibacterial behavior of graphene-based material against gram-positive and gram-negative bacteria such as S. aureus,[32,38,39,40] E. coli,[34,39,40,41,42] P. aeruginosa,[38,39] and P. syringae.[43]

The interaction between bacteria and graphene materials can be affected by several factors:

1. Physiochemical characteristics of graphene material: larger sheet sizes provide better bacterial isolation,[20,44] while smaller sheet sizes have better mechanical disruption properties with more production of reactive oxygen species[27,45] and more effortless penetration of phospholipid layer.[36] Additionally, fewer layers show the utmost antibacterial properties[28,46] as higher graphene accumulation and thickness are observed with increasing layers, reducing the interaction with microorganisms.[36] However, antibacterial efficacy can be improved with a smooth surface as bacterial colonization and biofilm formation mainly increase on rough surfaces.[26,45]

2. Exposure condition: The antibacterial properties of graphene materials depend on their concentration and exposure time[38,41] and mainly occur in aerobic conditions, as the presence of oxygen is necessary for the production of reactive species.[26,46]

3. Type and shape of bacteria: The antibacterial mechanism of graphene materials varies with different types, sizes, and shapes of bacteria.[25,26,28] The damage of cell membranes by graphene oxide is more effective on gram-positive bacterial with thin cytoplasmic membranes,[38] while oxidative stress is responsible for the antibacterial properties of reduced graphene oxide on gram-negative bacteria with more resistant cytoplasmic membranes.[28,32]

4. Surface modification of graphene material: Graphene functionalization with hydroxyl or epoxy group reduces bacterial proliferation compared to the carboxylic-rich group.[27] Also, the antibacterial property of graphene material can be enhanced by surface modification with antibiotics, enzymes, metal ions/oxide, or polymers.[5,11,33] Therefore, graphene oxide has higher antibacterial properties when compared to other graphene materials as they possess more functional groups.[41,42]

Application of Graphene and Its Derivatives in Dentistry

Many researchers investigated the antibacterial properties of graphene-based material to oral pathogens; some of these investigations are summarized in Table 1.

Table 1.

Studies investigated the antibacterial properties of graphene-based materials against oral pathogens

Author		Year		Bacteria		Graphene-based material		Findings of the study
Zanni et al.[47]		2016		S. mutans		Zinc oxide nanorods decorated with graphene nanoplatelets		The developed nanomaterial can reduce planktonic bacterial viability in a dose-dependent pattern (99.9% with the highest concentration) and inhibit bacterial biofilm formation.
Bregnocchi et al.[35]		2017		S. mutans		Graphene nanoplatelets		Graphene nanoplatelets can combine the antibacterial properties of graphene-based nanomaterials and the antiadhesion properties of two-dimensional graphene material. They can be used as a filler for antimicrobial dental adhesives without affecting their mechanical properties.
He et al.[48]		2017		S. mutans		Graphene oxide nanosheets		Graphene oxide nanosheets can effectively reduce living bacterial cells and inhibit biofilm development, but they have minimum effect on mature biofilm.
Sun et al.[49]		2018		S. mutans		Fluorinated graphene		The bacterial colony count decreases with increasing fluorinated graphene, and the antibacterial rate is up to 85.27% with fluorinated graphene.
Wu et al.[50]		2018		S. mutans		Reduced graphene oxide, silver nanocomposite		The modified nanocomposite has auspicious antibacterial properties against S. mutans to prevent dental caries.
Pulingam et al.[38]		2019		E. faecalis		Graphene oxide		The antibacterial characteristic of graphene oxide is concentration and time-dependent, with most bacterial inhibition of gram-positive bacteria occurring by wrapping isolation.
Qin et al.[51]		2020		S. mutans, P . gingiv alis and F. nucleatum		Graphene Oxide		The bacterial biofilm in contaminated titanium surfaces can be removed using graphene oxide with brushing, with enhanced osteogenic potential providing a possible treatment for peri-implantation.
Martini et al.[52]		2020		E. faecalis		Graphene oxide		Graphene oxide observed acceptable adhesion to root dentin with the ability to inhibit bacterial biofilm formation and development.
Wu et al.[53]		2020		S. mutans		Nano graphene oxide with antisense vicR RNA		The developed material can reduce biofilm aggregation and exopolysaccharide production within the biofilm.
Zhao et al.[54]		2020		S. mutans		Graphene oxide		Graphene oxide exhibited a concentration-dependent, highly effective (about 80%) antibacterial activity against biofilm and planktonic form of S. mutans
Guo et al.[55]		2021		S. mutans, P . gin givalis and F. nucleatum		Graphene Oxide		Graphene oxide can be used as an antibacterial coating for Polyetheretherketone dental implants to reduce implant-related complications.
Jang et al. 2021[56]		2021		S. mutans		Graphene oxide		Zirconia coated with graphene oxide can inhibit bacterial adhesion with stimulation of proliferation and stimulation of osteoblast.
Lu et al.[57]		2021		S. mutans		Graphene oxide nanosheets		The antibacterial properties of graphene oxide nanosheets are concentration and time-dependent, and infrared irradiation can enhance their antibacterial properties to 98%.
Mao et al.[58]		2021		S. mutans		Graphene oxide-copper nanocomposites		The investigated nanocomposite has antibacterial properties with low cytotoxicity.
Trusek and Kijak[59]		2021		E. faecalis		Graphene oxide		Enzymes encapsulated with graphene oxide can act as antibiotic drug carriers and effectively inhibit the growth of bacteria sensitive to antibiotics.
Wei et al.[60]		2021		S. mutans, P. gingivalis and F. nucleatum		Graphene		Graphene-reinforced dental implant has antimicrobial properties with convenient fibroblast response.
Cheng et al.[61]		2022		S. mutans and P. gingivalis		Graphene oxide		The peptide-loaded graphene oxide coating of dental implant pretend to have excellent antibacterial characteristics with no cytotoxic effect.
Gamal et al.[62]		2022		S. mutans		Graphene oxide		Antibacterial properties can be achieved by including graphene oxide nanoparticles within the composition of self-etch adhesive without affecting the bond strength.
Gao et al.[63]		2022		S. mutans, P. gingivalis and F. nucleatum		Graphene oxide		The graphene oxide coating of dental implants has antibacterial properties against gram-positive and gram-negative bacteria with adequate cytocompatibility.
Salgado et al.[64]		2022		S. mutans		Graphene		The dental resin modified with graphene effectively inhibits bacterial growth and adhesion to the resin surface.
Eskandari et al.[65]		2023		E. faecalis		Graphene oxide		Combining graphene oxide and double antibiotic paste improves root canal disinfection and could be considered a promising intracanal antibacterial medication.
Kim et al.[66]		2023		E. faecalis		Graphene oxide Reduced graphene oxide		The antibacterial characteristic of graphene oxide and reduced graphene oxide is similar, while the cytotoxicity of reduced graphene oxide is lower than graphene oxide; therefore, the reduced graphene oxide can be used as a more effective antibacterial agent.
Kim et al.[67]		2023		E. faecalis		Reduced graphene oxide		Combining apigenin and reduced graphene oxide could be an effective endodontic antibacterial disinfectant agent.
Park et al.[68]		2023		S. mutans and P. gingivalis		Graphene oxide		The infrared irradiation of graphene oxide with photothermal characteristics can reduce bacterial adhesion, minimizing peri-implantation when used as a dental implant coating.

The improved synthesis and promising characteristics of various graphene-based materials, together with their antibacterial properties, have attracted researchers in different fields of dentistry,[9,69] including [Figure 4]:

Figure 4.

Dental application of graphene-based materials

Regenerative dentistry and tissue engineering

Orofacial tissue is characterized by a unique structure[70] with minimal self-regeneration properties,[71] which challenges their regeneration by tissue engineering.[14] Nanomaterials, with their small size, large surface area, and biocompatibility, promote cell differentiation and proliferation, making them a candidate biomaterial for tissue regeneration.[72]

Various studies concluded that graphene and its derivative show multi-differentiation ability, including dental pulp,[73] bone marrow,[74] cementum,[75] and periodontal ligament stem cell regeneration.[76] So, they can be used for synthesizing or coating scaffolds to improve their repairing and regeneration properties.[15,77]

Improvement of dental material performance

Besides the antibacterial characteristics, the physiochemical and mechanical characteristics of graphene and its derivative can be utilized to improve the properties of various dental materials.[78] Several studies investigated adding graphene-based material into polymers,[79] glass ionomer cement,[49,80] composite,[81,82] primers,[83] implant materials,[84] and adhesives.[85]

Prevention and management of dental caries

Dental caries is a multifactorial, biofilm-mediated common dental disease. The process of caries development starts with the chemical disintegration of dental tissue due to acid generation through the metabolism of dietary carbohydrates by bacterial attachment to the tooth surface as a biofilm,[86] giving rise to subsurface demineralization, which progresses to caries if untreated.[87]

The antibacterial properties of graphene-based material against Streptococcus mutans are utilized by various dental materials to prevent biofilm formation and reduce demineralization and caries development.[88,89]

Periodontal disease management

Periodontitis is a chronic inflammatory disease stimulated by oral pathogens.[90] It leads to the gradual breakdown of the hard and soft tissues of the periodontal structure, with the loss of alveolar bone and periodontal ligament attachment.[91,92]

Periodontal pathogens can be suppressed by graphene and its derivative to control infection and prevent tissue destruction.[15,88] Several research concluded that graphene-based materials are highly effective against P. gingivalis,[51,55,93] the leading bacteria responsible for periodontal disease.[94] Additionally, graphene derivatives can be utilized for guided tissue and bone regeneration. This can be achieved by increasing the biocompatibility of collagen membranes,[95] promoting periodontal stem cell regeneration,[76,96] or a combination of both.[88]

Dental implant coating

A successful dental implant requires optimal osteointegration at the hard tissue interface and intimate gingival attachment at the soft tissue interface to prevent bacterial infiltration since bacterial contamination may cause implant failure by promoting peri-implantation.

Graphene materials can modify the implant surface to improve their biocompatibility[6] and enhance osteointegration[97] with outstanding antibacterial properties.[51,55,61]

Endodontic treatment

Root canal treatment aims to biomechanically clean the infected root canal system by destroying intracanal pathogens, decontaminating infected tissue, and avoiding further infection. The leading cause of endodontic failure is a persistent infection or reinfection in the root canal.[98]

Studies are carried out to improve the properties of endodontic sealer,[99] obturation material,[100] bioactive cement,[101] and irrigation material[102] with graphene derivatives, to enhance their antibacterial and mechanical properties.[9,78]

Teeth whitening

With the increased awareness of dental esthetics, tooth whitening is highly requested as one of the conservative procedures to enhance dental appearance. This can be achieved by physical stain removal or chemically using hydrogen peroxide to whiten the tooth.[103] Besides their widespread use of teeth whitening, they have side effects, including tooth sensitivity and gingival irritation.[104]

With graphene materials, the efficacy of hydrogen peroxide in tooth whitening can be raised while reducing side effects and shortening treatment time.[16]

Drug delivery

The control drug delivery system allows the release of active materials to specific organs at the required concentration with minimal side effects.[105] Graphene materials, with their large surface area, outstanding chemical properties, and biocompatibility, make them promising materials for controlled drug delivery of anticancer, antibiotic, genes, and other pharmaceutical drugs.[106]

Despite the well-known ability of graphene materials as drug carriers in the biomedical field, few studies investigated this property for dental applications.[77] The effective concentration and gradual drug release can be achieved by employing graphene oxide as a drug delivery system for bone morphogenetic protein[107] and antibiotics.[15,59]

Graphene-based biosensors

The large surface area, biocompatibility with the excellent signal response of graphene, and their derivatives encourage their use in biosensor synthesis as they can be used for the detection of antibodies, DNA, proteins, and enzymes.[108]

Graphene-based biosensors are researched for detecting bacterial and viral markers in the oral cavity. Also, they are effective in the early detection of cancer biomarkers in saliva.[15,16]

Potential Application of Graphene-Based Materials in Orthodontic

Due to their unique physiochemical and antibacterial properties, graphene materials are also investigated to improve the properties of orthodontic materials [Figure 5]. Table 2 summarizes some of the studies of graphene and its derivative in the orthodontic field.

Figure 5.

Orthodontic application of graphene-based materials

Table 2.

Summary of the studies that used graphene-based materials in orthodontic materials

Author		Year		The used graphene materials		Method		Material type		The conclusion of the study
Lee et al.[109]		2018		Graphene oxide and bioactive glass		Microhardness, SBS, ARI, cytotoxicity, antibacterial, anti-demineralization tests		Orthodontic adhesive		The modified adhesive has appropriate mechanical and biological properties.
Nam et al.[110]		2019		Fluoridated graphite and bioactive glass		Microhardness, SBS, antibacterial, cytotoxicity, fluorine dissolution, remineralization test		Orthodontic adhesive		The modified resin has physical stability and biological safety for clinical use to prevent WSL.
Mallick and Arunachalam[111]		2019		Graphene nanoplatelet		TEM, XRD, FESEM, FTIR, TGA, XPS, nanoindentation and corrosion resistance		Nitinol wire		There is an improvement in corrosion resistance with graphene coating and post-deposition annealing can increase the coating strength
Alnatheer et al.[112]		2021		Graphene oxide		SBS, ARI, cytotoxicity, antimicrobial tests		Orthodontic adhesive		The modified adhesive has superior antimicrobial and mechanical properties.
Ghorbanzadeh et al.[113]		2021		Curcumin-reduced nano-graphene oxide		SBS, antimicrobial test		Orthodontic adhesive		The modified adhesive has no adverse effect on SBS with improved antimicrobial activity.
Pourhajibagher and Bahador[114]		2021		Graphene oxide		SBS, ARI, antimicrobial tests		Orthodontic adhesive		Improved antibacterial properties with no effect on SBS and ARI
Sawan et al.[115]		2021		Graphene nanoplatelets and silver nanoparticles		SBS, ARI, cytotoxicity, antibacterial tests		Orthodontic adhesive		The modified adhesive has potential antibacterial properties
Jiao et al.[116]		2022		Reduced graphene oxide		Observation and analysis of tooth movement, evaluation of osteogenesis		Gelatin-reduced graphene oxide		The gelatin-reduced graphene oxide promotes bone remodeling
Pan et al.[117]		2022		Graphene sheet		Friction test, immersion test		Orthodontic archwire		The coated wire has improved friction and wear performance
Pourhajibagher et al.[118]		2022		Graphene oxide		Cytotoxicity, antimicrobial tests		Orthodontic adhesive		A modified adhesive has antimicrobial activity against streptococcus mutans
Wang et al.[119]		2022		Graphene sheet		TEM, Raman spectroscopy, hardness, young module, Fretting wear test		Orthodontic archwire		The modified archwire has a low friction coefficient and a low wear rate
Barbur et al.[120]		2023		Graphene oxide with (silver or zinc oxide)		SEM, compressive strength, bending resistance, and tensile strength test		Orthodontic occlusal splint		The graphene based polymethylmethacrylate has good mechanical properties making it a promising material for future use

SBS=shear bond strength, ARI=adhesive remnant index, WSL=white spot lesion, TEM=transmission electron microscope, XRD=X-ray diffractometer, FESEM=field emission scanning electron microscope, FTIR=Fourier transform infrared spectroscopy, TGA=thermogravimetric analysis, XPS=X-ray photoelectron spectroscopy, SEM=scanning electron microscope

The use of graphene-based material in orthodontic adhesive system

Successful orthodontic treatment is based on enhancing dental esthetic and function by correcting the occlusion[121] without influencing the health of the teeth and the supporting tissue.[122] Fixed orthodontic appliance and their accessories act as a plaque retentive factor that makes maintaining oral hygiene difficult and increases the risk of enamel demineralization and the development of white spot lesions.[123] Since the white spot lesion is visible to the naked eye, it can damage the esthetic outcome of orthodontic treatment.[110]

Preventive treatment of white spot lesions can be accomplished by patient training in tooth brushing and fluoride gargling. These methods require patient cooperation, which is usually unpredictable.[124] Graphen-based materials with unique properties can be incorporated into orthodontic adhesives to improve their biological and mechanical properties. The addition of graphene-based materials to orthodontic adhesive was investigated in many studies. The incorporation of 0.25 wt.% of graphene oxide into orthodontic adhesive shows antibacterial properties against s. mutans of 31% and 47% after 1 and 30 days, with the acceptable bond strength and adhesive remanent index.[112] Another study investigated orthodontic adhesive dopped with 5 wt.% of graphene oxide; the result of the study showed the modified adhesive has antibacterial properties against s. mutans with proper shear bond strength and adhesive remanent index.[114] A study by Pourhajibagher et al.[118] found that the total bacterial count was reduced for up to 30 days by modifying orthodontic adhesive by 5 and 10 wt.% of nano-graphene oxide. Furthermore, Lee et al.[109] concluded that adding a 5% mixture of graphene oxide and bioactive glass observed higher antibacterial and remineralization characteristics. Also, the addition of graphene oxide and fluorinated graphite to high-flow orthodontic adhesive is researched by Nam et al.[110] and reported inhibition in bacterial growth with enhancement of remineralization properties. Additionally, modifying orthodontic adhesive with 5% curcumin-reduced nano-graphene oxide has no adverse effect on antibacterial characteristics or physical and mechanical properties.[113] The incorporation of a methacrylate-based bonding agent with 0.25 wt.% of graphene nanoplatelets functionalized by silver nanoparticles showed sustained enhancement of antibacterial behavior with acceptable bond strength.[115]

The use of graphene-based material as coating material

Fixed orthodontic appliances comprise brackets, archwire, and axillaries.[125] Orthodontic therapy depends on the bracket sliding along the archwire to produce tooth movement;[126] however, tooth movement may be opposed by the frictional force between the bracket and archwire.[127,128] Therefore, controlling friction is advantageous regarding treatment duration, desirable movement,[129] and minimizing root resorption.[130] With the advancement of nanotechnology, they improve orthodontic archwire mechanical and biological properties by coating them with nanomaterials.[131]

Among the graphene-based material, graphene sheet was used by Wang et al.[119] as a coating for stainless steel archwire using a plasma sputtering deposition system, the coated archwire showed a remarkable reduction of wear rate and friction coefficient, proposing an advantage for orthodontic tooth movement. Another study investigated the stable and static friction of stainless steel archwire coated with graphene sheets under wet and dry conditions; a low friction coefficient was observed in the wet condition of artificial saliva. Although the friction manner observed some impairment when immersed in wet conditions for a prolonged time, they still followed a moderate friction coefficient after a 30-day immersion in artificial saliva.[117] Additionally, the researched graphene coating of nitinol wire reported enhancement of corrosion resistance, and the coating strength can be enhanced by post-deposition annealing in a vacuum environment. Similarly, the coating of nickel-titanium alloy with graphene oxide was studied by Dai et al.,[132] who concluded that graphene oxide coating can reduce corrosion in artificial saliva and also show antibacterial characteristics against S. mutans.

Application of graphene-based materials to improve bone remodeling

Conventional orthodontic treatment is a lengthy procedure, and there is increasing interest in speeding up orthodontic tooth movement and reducing the duration of treatment.[133] During orthodontic treatment, the main limiting factor for tooth movement is bone remodeling around the teeth.[116]

Biocompatible gelatin of reduced graphene oxide was synthesized by Jiao et al.[134] and evaluated for its ability to modify bone remodeling in a mouse orthodontic tooth movements model; they found that local injection of gelatin-reduced graphene oxide can accelerate tooth movement with more neovascularization and osteoclastic bone resorption without affecting the survival life of animals.[116]

Graphene-based polymethylmethacrylate

Polymethylmethacrylate is a transparent polymer with wide application in dentistry and orthodontics,[135] it can be utilized for the fabrication of myofunctional appliances, occlusal splints, retainers, bite guards, and bite planes.[136] Despite their popular use, they have many drawbacks such as poor mechanical characteristics, polymerization shrinkage, and poor antibacterial properties.[137] Therefore, several studies have been carried out to improve the polymethylmethacrylate properties using different materials.[136,138] Graphene-based materials are among the researched materials to improve the mechanical[139] and antibacterial properties of polymethylmethacrylate.[140] Commercially available orthodontic polymethylmethacrylate (Orthocryl) was modified by Barbur et al.,[120] using 2% graphene oxide-silver and 1% graphene oxide-zinc oxide, after preparation of polymethylmethacrylate by salt and pepper methods, they evaluated for mechanical properties. Modified polymethylmethacrylate has excellent mechanical properties, with the possibility of clinical use in the future.

Conclusion and Future Perspective

According to this review, the following can be concluded in terms of the potential use of graphene-based material in the dental field:

1. The improvement of the antibacterial properties of dental materials, which can be beneficial in the control and management of dental caries, periodontal disease, root canal infection, and peri-implantitis.

2. The physiochemical and mechanical characteristics of graphene-based materials can be used to improve the mechanical properties of dental materials.

3. They might be utilized for enhancing the ability of dental tissue regeneration.

4. They can also be used for drug delivery, biosensors, and teeth whitening.

The application of graphene-based materials in orthodontics is in the primitive stage; however, the available evidence shows that:

1. The antibacterial properties of the orthodontic adhesive system can be improved by the addition of graphene-based materials. This could have a positive role in maintaining good oral hygiene and prevention of white spot lesions during orthodontic treatment.

2. Graphene-based material can be included within or used as a coating of orthodontic material to improve its mechanical properties, such as controlling the archwire-brackets friction.

3. Graphene-based material can be utilized to modify bone remodeling during orthodontic movement.

However, there are limited in vitro studies in orthodontic application of graphene-based material with a lack of in vivo studies. Hence, the provided and discussed evidence can enhance researchers to develop novel orthodontic applications for graphene-based materials to improve the mechanical and antibacterial properties of orthodontic materials. Also, they can be investigated to enhance dental tissue regeneration, which can be beneficial for both acceleration and retention of orthodontic tooth movement. Additionally, enough clinical studies are required to utilize this material in market-oriented investigation areas to become available for clinical use in the future.

Financial support and sponsorship

This study was self-funded. No sponsor was involved in the study design, in the collection, analysis, and interpretation of data, in the writing of the manuscript; and in the decision to submit the manuscript for publication.

Conflicts of interest

There are no conflicts of interest.