ABSTRACT

Nanotechnology is the science of manipulating matter, measured in the billionths of a nanometer, roughly the size of two or three atoms. It is widely used in our day-to-day life including its use in medicine and is considered as a vital current technology of the 21^st century based on its economic and scientific potential. Its application is being experimented in various domains in orthodontics, from surface coatings to the development of novel materials. Orthodontic materials must have specific characteristics such as biological safety, functionality, and adequate tissue response. They have to pass specific biocompatibility tests to meet regulatory standards. Any material used in oral cavity might encourage unnecessary disturbance due to its complex and varied environment. The nanomaterials have many advantages in the field of orthodontics, especially with improved mechanical and antimicrobial properties. Nanoparticles can easily penetrate tissues and can affect biological behaviours at different levels. The introduction of nanotechnology gives better opportunities to both patient and orthodontist to new physicochemical, mechanical, and antibacterial properties of nanosized materials and can be used in coating orthodontic wires, elastomeric ligatures, and brackets, producing shape memory polymers and orthodontic bonding materials. The present review article focuses on the application of nanoparticles in orthodontics. This article presents a brief overview of nanotechnology, types of nanoparticles, biological safety of different nanoparticles used in orthodontics and their applications in the field of dentistry and orthodontics.

 

KEY WORDS

Nanoparticles, Biocompatibility, Orthodontics, Nanoscience

BACKGROUND

Nanotechnology is defined as “the direct manipulation of materials at the nanoscale"¹ and one of the most prominent areas for current research and development across a wide range of fields.² Prof. Kerie E. Drexeler coined the term "nanotechnology" in his book "Engines of Creation" in 1986, and Norio Taniguchi, a researcher, defined it as "the processing, separation, integration, and deformation of materials by one atom or one molecule.”

Nanoscience involves the study of materials on the nano - scale level between approximately 1 and 100 nm. These materials have been receiving considerable attention as a result of their unique physical and chemical properties, biological properties, and functionality due to their nano - scale size, and have elicited much interest and important applications in optics and biomedicine.⁴ Nanoparticle presents a greater surface - to - volume ratio when compared with non - nano scale particles, interacting more closely with microbial membranes and provides considerably larger surface area for antimicrobial activity.⁵ There are two ways to produce nanomaterials³

1. Top - down approach: It starts with bulk material and then breaks it into smaller pieces using mechanical, chemical or other forms of energy.
2. Bottom - up approach: It synthesizes the material from atomic or molecular species via chemical reactions, allowing for the precursor particles to grow in size.

Nanoparticles are generally classified based on different shapes of nanoparticles such as rod, rectangle, hexagon, cube, triangle, and star - shaped nanoparticles can be produced. Bulk solution synthetic methods often produce nanoparticles of multiple sizes and shapes and low yield of the desired size and shape.³ In the field of dentistry, orthodontic material must have specific characteristics such as biological safety and functionality, adequate tissue response and resistance to corrosion and metals used are also identified to be cytotoxic, mutagenic and allergenic to oral tissue. Biosafety of nanoparticle materials is a subject of concern, the future in orthodontic treatment will benefit enormously through nanotechnology and its clinical application are at a reasonable cost to the orthodontist and the patients.²

This paper intends to give an extensive understanding of the biological safety of nanoparticles and their use in orthodontics and discuss the new application of nanoparticles in orthodontics with the present research evidence.

FACTORS AFFECTING THE BIOSAFETY OF NANOPARTICLES

Medical nanoparticles as three main categories⁶ soft; hard solid; and other.

1. Soft particles, such as polymer NPs, micelles, vesicles, liposomes, core - shell systems, gels, polymeric medicines, or polymer - drug conjugates, typically made up of polymers, proteins, or lipids.
2.  Metal and ceramic nanoparticles, such as oxides, semiconductors, and carbon nanotubes, as well as nanocrystal medicinal formulations, are examples of hard solid - core nanoparticles.
3. Due to their nano size and structure, other particles in the third category, such as antibody drug conjugates and albumin particles, can also facilitate nano type interactions.

The nanometer size of the nanomaterials renders them

a) A large fraction of surface atoms;

b) High surface energy;

c) Spatial confinement; and

d) Reduced imperfections,

Which normally do not exist in the corresponding bulk material. At the nanometer scale, properties become size - dependent, which include

1. Chemical properties – reactivity, catalysis;
2. Thermal properties – melting temperature;
3. Mechanical properties – adhesion, capillary forces;
4. Optical properties – absorption and scattering of light;
5. Electrical properties – tunnelling current; and
6. Magnetic properties – superparamagnetic effect.⁷

The nanoparticles' enormous surface - to - volume ratio is a major factor in their new physical, chemical, and mechanical capabilities as compared to the bulk state. As particle size fall results in nanoparticles having a substantially bigger surface area per unit volume than bigger particles. This makes nanoparticles more chemically reactive than a similar mass of material made up of bigger particles.⁸

APPLICATION OF NANOPARTICLES IN DENTISTRY &

Despite widespread effectiveness, orthodontic therapy is limited by many issues, including friction, extensive treatment times, and consequences like tissue irritation, tooth decalcification owing to bacterial development, and root resorption. Nanoparticles bond strongly to other materials or each other due to their large surface free energy (agglomeration). The nano - coatings produced are either lubricants to reduce friction or antibacterial to minimize microbial counts and the issues that come with them, including cavities, periodontal illnesses, and decalcification around the bracket.⁵ The unique features of silver and gold nanoparticles can be used to give local anaesthetic, diagnose, and treat oral problems. Nanoparticles are employed in orthodontics because of their biocidal, anti-adhesive, and anti-biofilm properties, as well as their demineralization effect and friction reduction.^{9-15,49,16-19} Based on the coating substance, nanoparticles are biocompatible and less cytotoxic. Friction being the most important in fixed mechanotherapy for alignment and levelling, as well as space closure. Up to 60 % of the force is wasted as friction, reducing the force available for tooth movement and necessitating the application of extra force to counteract the frictional force. Increased friction during orthodontic treatment can cause a variety of issues, including trouble with anchoring management and an increase in the length of orthodontic therapy. Several strategies have been developed to reduce friction and improve both the mechanical and biological properties of orthodontic wires, including changing the bracket design, using various types of alloys, surface treatment or coating of brackets using various techniques and materials, and modifying the surface of both the archwires and brackets. On stainless steel and NiTi wire, nanoparticles such as copper oxide,³⁷ inorganic fullerene - like nanoparticles of tungsten disulphide,^48,28 and Co + fullerene - like WS2 NPs,²⁴ silver - coated nanoparticles¹⁹ and zinc oxide nanoparticles on the orthodontic bracket and an archwire³⁵ showed a 50 % reduction in coefficient of friction. During orthodontic treatment, plaque collection on fixed and removable appliances is also a typical issue. Gingivitis, periodontitis, white spot lesions, increased caries risk, halitosis, superimposed infections, TAD failure, and delayed tooth movement are all possible repercussions of bacterial development. Nanoparticles as antibacterial agents can be included or put on bracket surfaces, resin composites, glass ionomer cement, and mini-implants to reduce these issues.⁵ Nanoparticles coated on bracket which showed excellent antibacterial effect and biocompatibility were silver NP,^21,31,40,50 Titanium nitrite,¹ Nitrogen - doped titanium oxide,^21,22 CuO & ZnO NP.³⁷ Carbon nanoparticles were integrated into stainless steel wire.³⁸ Silver nanoparticles coated on mini-implants used as temporary anchorage devices have antibacterial properties, and are safe and prevent implant infection.^44,51 Nano - composite showed a good antibacterial effect when incorporated with ZnO NP and Chitosan NP,^20,28 titanium oxide NP,⁴⁵ nitrogen doped titanium oxide NP,²⁹ hydroxyapatite NP^20,32 and fluoride releasing nano- composite to prevent demineralization. Nanosized fluorapatite (NFA) or fluorohydroxyapatite (NFHA) particles at a concentration of 25 %,^31,52 silver nanoparticles,^53,54 magnesium oxide,⁵⁵ and quaternary ammonium nanoparticles have all been used to improve GIC.⁴⁰

Nanotechnology is widely used in our day-to-day life including its use in medicine. In 21^stcentury based on its economic and scientific potential, nanotechnology holds promise in many areas like advanced diagnostics, targeted drug delivery and biosensors. It has several applications in dentistry as well, from diagnosis of pathological conditions to local anaesthesia, orthodontic tooth movement and periodontics. In the field of orthodontics, nano-coating on the orthodontic archwire, brackets, bands, elastomeric ligatures, orthodontic power chains, mini-implants are used for its reduced friction properties, excellent corrosion resistance, and good antimicrobial property, fluoride- releasing nano- filled composite (FN) reduces the caries lesion development around the brackets and nanoparticles can be used as agents for remineralization of decalcified enamel.

This present reviewed article summarized the most significant innovation of nanotechnology in the field of orthodontics and reviewed the most recent literature comparing with different research studies and focusing the attention on the application of new nanoparticles and their benefits. The nanomaterials have introduced many advantages in the field of orthodontics, especially with improved mechanical and antimicrobial properties. The future in orthodontic treatment will benefit enormously through nanotechnology should all the current attempts succeed in its clinical application at a reasonable cost to the orthodontist and patients.

CONCLUSIONS

REFERENCES

DISCLOSURE AND FUNDING

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Financial or other competing interests: None.

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COPYRIGHT

Copyright © 2021 Nausheen Mobeen et al. This is an open access article distributed under Creative Commons Attribution License [Attribution 4.0 International (CC BY 4.0)]       

How to cite this article

Mobeen N, Kishore S, Gandhi R, et al. Biosafety of nanoparticles used in orthodontics - a literature review. J Evolution Med Dent Sci 2021;10(32):2658-2664, DOI: 10.14260/jemds/2021/543

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