Nanotechnology is based on the Nanoparticles (NPS) which are insoluble particles smaller than 100 nm in size and the set of technologies that enables manipulation of these particles on an atomic, molecular and supramolecular scale is termed ‘Nanotechnology’. Applications of nanotechnology are various in different domains including health care and have also carved their way into various specialties of dentistry. This article presents various type of nanoparticles and their application in the field of Orthodontics. The various tests were performed using nanoparticles, to detect the physical and biological properties of the new material, and are also summarized for easy referral.
Nanotechnology has gained importance in pa last few years due to its ability to the enhancement of materials’ properties and other specifications such as antiparasitic properties. Nano-sized materials have been applied in various areas of dentistry. Nanotechnology can be used in orthodontics to enhance the quality of treatment. In the current study, a comprehensive review is carried out on the applications of nanotechnology in dentistry.
The concept of nanotechnology was introduced in 1959 by renowned physicist Richard Feynman who described that it could be possible to manipulate atoms directly. Norio Taniguchi first used the term “Nanotechnology” in 1974 but K. Eric Drexler published it. He proposed the idea of a nanoscale ‘assembler’ which would be able to reproduce and have molecular control.
Nanotechnology has a very wide applications range in various medical purposes such as drug cancer detection and therapy, cell repairing, etc. For example, root-canaled teeth can be effectively disinfected by using nano-based antimicrobial agents.
The use of nano-materials in devices makes it possible to enhance the mechanical strength and efficiency of the device. Several types of research going on on the applications of nanotechnology in different areas to achieve more efficient and reliable performance.
Nano-sized materials and instruments have been widely used in various medical aspects to get better treatment and diagnosis. Ghaziyani et al.  conducted a study on a CT imaging nanoprobe and concluded that it is used for finding out the tumors of the breast. Some nano-particles can be applied in radiotherapy for example gold. Zabihzadeh et al. Carried out research on gold nanoparticles in radiotherapy to remove colorectal cancer cells. They observed that using these nanoparticles can improve radiotherapy performance.
To cover all the related research carried out on the usage of nanotechnology in orthodontics, a primary search was performed in various databases including Google Scholar, Scopus, and PubMed. The keywords used in the search process were “Dentistry”, “Nanotechnology”, and “Medical Application”. All the study materials between 1990 till 2019 were considered for analysis in this article. Afterward, the subjects of the resources were analyzed and evaluated. The resources for the present study (applications of nanotechnology in orthodontics) were selected.
In the next step, the resources were studied, and their outputs were analyzed. The research was summarized and classified to have a well-structured study. At last, the results and important things related to resources were extracted and represented here. The process and conducted activities in each step are shown in hashing 1.
As was mentioned previously, nanotechnology has a large application range in various fields of dentistry including endodontics, prosthodontics, and pediatric dentistry. Nano-based materials can be applied for diagnostics, delivery of drugs, dental adhesives, and sensors utilized in biosciences [3–5]. The current study focused on the field of nanotechnology-related to dentistry aspects archwires.
Several studies have been going on on the materials used for orthodontic archwires and brackets. Mechanical and medical characteristics of the archwires gained importance due to their probable allergic issues and corrosion during the treatment. Nanotechnology is applicable in these wires to achieve so desired properties.
Friction against the movement of archwires causes many difficulties. In addition, it can lead to some serious pain. By using appropriate lubricants, it is possible to eliminate these problems. Nanotechnology has been used to improve lubricant properties. Nano-based lubricants can be used in archwires for smoothing their motion Katz et al . Utilized a self-lubrication coating that contained fullerene-like nano-sized particles. Results indicated that the use of this lubricant reduced friction and therefore, a more ffavorablmovement of archwires was observed. In addition to using lubricants, the appropriate coating can result in lower frictional force against archwire movement.
In a study, three wires made of stainless steel, nickel-titanium, and titanium molybdenum alloy were coated with nanoparticle film (nanoceramics) which was smooth, and uniform as compared to traditional materials. It was observed that using the coating can enhance the surface topology, therefore, problems related to friction are reduced.
Nanomaterials can be used as a bonding agent(adhesive) in orthodontics to achieve higher mechanical strength or reduce the risk of enamel damage . Adhesion strength plays important role in orthodontics and must be considered to get reliable treatment and subject to thermo-cycling. As was mentioned, by using nanotechnology in material, the properties can be improved such as shear strength. Chalupa et al. . evaluated the shear bond strength of archwires that were bonded with Nano-filled composites compound. In their study, three composites were applied to join the brackets. In the first group, Transbond XT as a conventional bond was utilized. Two nanocomposites including Filtek TM Supreme XT and ELITE Aesthetic Enamel were applied in the second and third groups, respectively. The shear bond stress values for the first, second, and third composites were equal to MPa, respectively. Therefore, it can be concluded by using specific types of nanocomposite compounds, the shear stress bond can be improved as compared to conventional composites.
Some of the nano-sized materials have antimicrobial properties such as antibacterial, antifungals, etc. This specification can be useful in dentistry treatment to reduce caries and the number of microorganisms. In a study performed by Mirhashemi et al.  effect of adding Zinc oxide (ZnO) and Chitosan (CS) nanoparticles used in the dental composite for orthodontic was investigated. Bacterial growth after curing was equal to and for conventional and nanocomposites, respectively. Therefore, it can be concluded that using antimicrobial nanoparticles in the composite can reduce pathogens. As the composites are used in the form of a paste, antimicrobial nanoparticles can be coated on the archwires. In an in vivo research , silver nanoparticles were coated on archwires used in dentistry. It was observed that the addition of the nanoparticles was influential in S. mutans inhibition and decreased the caries of smoothing of the surface. Other nanoparticles with antimicrobial properties such as CuO are used in o dentistry adhesives to reduce microorganisms. In addition, it was concluded that an increase in the concentration of nanoparticles can improve the antimicrobial performance of the applied adhesives.
As nano-materials are used, nanotechnology can be used in various fields of orthodontics. For instance, nano-indentation tests are used to evaluate the various properties of materials used during dentistry treatment. For instance, Silva et al  utilized this type of test to find out the hardness and modulus of elasticity of coatings used in dentistry brackets. So, it can be concluded that using nano-based tests is a simple and correct method to evaluate the mechanical properties of material required for dentistry. In addition to flexible modulus, nanoindentation tests were applied to estimate other mechanical properties such as surface smoothness , hardness, and surface roughness of two frequently used dentistry brackets. Nano-indentation test can be used to estimate the side effects of orthodontics. For instance, the nano-indentation test is applicable to measure fracture toughness of dental enamel and the effects of bonding-debonding of archwires on it .
Nanorobots have large numbers of applications in medical sciences. These devices can be used in cancer detection and therapy, local anesthesia, etc. In addition to the mentioned applications, nanorobots can be used in orthodontics operations. The time of orthodontic operations can be minimized by using nanorobots. The robots used in orthodontic treatments can rotate without causing pain and vertically reposition the tooth in several minutes while it takes hours by using conventional methods . In addition, nanorobots can directly operate on periodontal tissues which makes them an appropriate tool for orthodontic treatment. In Fig 2, the most important applications of nanotechnology in orthodontics are represented.
The review paper is focused on the research carried out on the applications of nanotechnology in the dentistry field. The most significant outcomes of the reviewed studies were assessed and extracted. According to the literature review, nanotechnology can be applied in four major aspects. First, nano-coating and lubricants, are applicable for reducing friction against their movements. An increase in smoothness results in faster and easier treatment. In addition to dentistry brackets, nanoparticles can be added to composites, and bonding agents are used in dentistry to enhance their mechanical properties such as shear bond strength. According to reviewed papers, the type of nanostructures nanoparticles favorable and their concentrations are the most important factors affecting the mechanical properties of the nanocomposites. It seems that studies should focus on finding favorablenanoparticles favorable types of nanoparticlesfavorable and perfect concentration to obtain the most favorable results.
The antimicrobial properties of some nano-particles are another useful property which makes them used in the dentistry field. Some types of antimicrobial nano-particles such as Zinc Oxide and Silver have been tested during dentistry treatment and have shown their ability to eliminate pathogens. Lnanoparticlesthe clues used for improving mechanical properties, type and, the concentration of nano-particles play important rolrolesecolorless in their antimicrobial property.
Another application of nanotechnology in orthodontics isnanonano-indentation test which can be are used to evaluate the various properties of materials used during dentistry treatment of tools and mediums used in orthodontics procedures. In addition to the mentioned other applications, nanorobots can be used in orthodontic treatments to rotate without causing pain and vertically reposition the tooth treatment more accurately.
Future studies should focus on finding more improved nano-materials used in the dentistry field. Using nano-material-based lubricant for dentistry brackets, nano-particle for coating nanocompositesbrackets, and nanocomposites as bonding agents are among the most useful ideas for upcoming studies.