INTRODUCTION:

The word “nano,” which is derived from the Greek word (nannos) meaning “dwarf,” is a prefix that literally refers to 1 billionth of a physical size. Thus 1 nm is 1 billionth of a meter ^{1, 2}.

According to the definition of the National Nanotechnology Initiative, nanotechnology is the manipulation of materials at nanoscale measurement. This term defines a technology that enables almost complete control of the structure of matter at nanoscale dimensions. Nanotechnology will give us the ability to rearrange atoms as per our requirements and subsequently enabling us to achieve effective control of the structure of matter^{3, 4}.

Nanotechnology is the science which deals with the physical, chemical, and biological properties of structures and their components with dimensions in a nanoscale.

Nanotechnology is based on the creation of functional structures by controlling atoms and molecules on a one after the other basis. The use of this technology will allow many developments in the health sciences as well as in materials science, biotechnology, electronic and computer technology. With developments in biotechnology, nanotechnology is especially anticipated to provide advances in dentistry and innovations in oral health-related diagnostic and therapeutic methods⁵.

The availability of molecular nanotechnology will give rise to speedy progress to address medical problems and will use developing molecular knowledge to maintain and improve human health even at a molecular level^{6, 7}. Nanomedicine could develop devices that are able to function within the human body in order to diagnose the presence of a disease early, and to identify and quantify toxic molecules and tumour cells. Nanodentistry will enable the maintenance of comprehensive oral health by the use nanomaterials, including tissue engineering and, subsequently, dental nanorobots⁸.

The aim of this paper is to review the progress of the field of nanotechnology and its applications and advancements in the field of dentistry in the form of nanodentistry.

The development of nanotechnology

Nano-phase materials were first introduced in an academic context in 1959 at a meeting of the American Physical Society. At this meeting, Nobel Prize winning physicist Richard P. Feynman gave a speech which is considered the foundation for the field of nanotechnology. In his speech, Feynman stated that manufacturing at the scale of atoms and molecules would result in many new innovations; in addition, he also stated that particular methods for measurement and manufacturing at the nanoscale dimensions should first be developed to realize such advanced possibilities⁹.

Nanomedicine

This concept was proposed first in 1993 by Robert A. Freitas Jr. and was defined as observing, controlling, and treating the various systems of the human body at the molecular level using nano-structures and nano-devices¹⁰. Nanomedicine has far reaching applications ranging from the release of drugs with nanospheres to tissue scaffolds based on nanotechnologic design that follows tissue formation, and even nanorobots for diagnostic and therapeutic purposes¹¹. Drug molecules transported through the body by circulation may cause undesirable adverse effects in untargeted regions. On the other hand, nanorobots can identify unhealthy cells and can find and destroy them wherever they are located^11-13. Nanomedicine provides improvements and advancements in available and existing techniques in addition to developing fully new techniques ^{6, 7}.

Nanorobots in medicine:

Nanorobots are about 0.5–3 microns in diameter and will be constructed of parts with dimensions in the range of 1–100 nanometers. Carbon will be mainly used, which can be either in the diamond or fullerene form. Programmable nanorobotic devices would be capable of allowing physicians to perform precise interventions at a cellular and molecular level. Medical nanorobots have been proposed for applications in pharmaceutical research, clinical diagnosis and also for improving respiratory capacity, enabling instantaneous homeostasis, supplementing the immune system, replacing DNA sequences in cells, repairing brain damage, and resolving gross cellular insults whether caused by cryogenic storage of biological tissues or other processes which may be irreversible¹⁴.

Nanotechnology in dentistry:

The progress of nanodentistry will allow nearly perfect oral health by the use of nanomaterials and biotechnologies, including the use of tissue engineering and nanorobots⁸.

Nanodentistry in Tissue engineering:

Nanoscale fibres are similar in shape to the arrangement between the fibrils of collagen and hydroxyapatite crystals present in bone. The biodegradable polymers or ceramic materials that are mostly preferred in bone tissue engineering do not always have the required mechanical endurance despite their osteoconductive and biocompatible properties. Recent studies indicate that nanoparticles can be used to enhance the mechanical properties of these materials. The primary reason for preferring nanoparticles is that the range of dimension of these nanostructures is the same as that of cellular and molecular components^{15, 16}.Bone replacement materials developed using nanotechnology are commercially available^17-19.

Dental nanorobots and dentifrobots:

Dental nanorobots are able to move through teeth and surrounding tissues by using specific mechanisms for their movement. They are controlled by nanocomputers which have been previously programmed via acoustic signals used for ultrasonography.Nanorobots (dentifrobots) left through the use of mouthwash or toothpaste on the occlusal surfaces of teeth can clean organic residues by moving throughout the supragingival and subgingival surfaces, continuously preventing the accumulation of calculus⁸. These nanorobots, which are capable of moving as fast as 1 to 10 micron/second, are safely deactivated when they are swallowed^{1, 17}. Subocclusal-dwelling nanorobotic dentifrice delivered by mouthwash or toothpaste could patrol all supragingival and subgingival regions at least once a day, metabolizing trapped organic matter into harmless vapours and performing continuous calculus debridement. Dentifrobots are extremely small (1–10 micron), with 103–105 nanodevices/ oral cavity, crawling at 1–10 microns/second¹⁷.

Nanocomposites:

Nanotechnology has enabled production of nano-dimensional filler particles, which are added either individually or as nanoclusters into composite resins²⁰. Nanofillers differ from traditional fillers^{21, 22}. Nanotechnology allows the production of filler particles of nano-size that are compatible with dental composites; this in turn allows a greater amount of filler to be added into the composite resin matrix²⁰. Nanoparticles allow the production of composites with smooth surfaces after polishing and confer superior aesthetic features to the material. Composite resins containing such particles are easy to mould and have a high degree of strength and resistance to abrasion. Therefore, the area of use of resins containing nanoparticles is more widespread than that of composites containing hybrid and microfillers^23,24. The fillers in nanocomposites have a higher degree of translucence since they are smaller than the wavelength of light, allowing the preparation of more aesthetic restorations with a vast range of colour options²². Nanocomposite systems have the capability to enhance this continuity between the tooth surface and the nanosized filler particle and provide a more stable and natural interface between the mineralized hard tissues of the teeth and these advanced restorative biomaterials. Molecular manufacturing, within nanotechnology may provide composite resin with filler particles that are much smaller, can be dissolved in higher concentrations, and can be polymerized into the resin system with molecules designed to be compatible when coupled with a polymer, and provide physical, mechanical, and optical characteristics of a unique nature. The mineral component of the composite, a filler, is termed the "dispersed phase” and has been markedly advanced with the addition of small particles. In dental composites, fillers provide not only strength but also reinforcement to the matrix^14,25,26. Nanoproducts Corporation has successfully manufactured non-agglomerated coatings to produce nanocomposites. The nanofiller thus used includes an aluminosilicate powder with a mean particle size of 80 nm and a 1:4 M ratio of alumina to silica and a refractive index of 1.508¹⁴. Advantages include:

· Superior hardness

· Superior flexural strength

· Superior modulus of elasticity and translucency

· 50% reduction in filling shrinkage

· Excellent handling properties.

Nanotechnology in prevention of dental caries:

The use of toothpaste containing nano-sized calcium carbonate enhances remineralization of early enamel lesions. A study that investigated the bacteriostatic effects of silver, zinc oxide, and gold nanoparticles on Streptococcus mutans, the primary microbe causing dental caries, reported that compared to the other nanoparticles, silver nanoparticles had an antimicrobial action at lower concentrations and with lower toxicity as compared to the other nanoparticles^{27, 28}.

Role of nanotechnology in Diagnosis and Treatment of oral cancer

Nanotechnology is also used in molecular imaging with tomography and photo-acoustic imaging of tumours and in the therapy of cancer as photothermal therapy and radiotherapy. Nanotechnology has opened windows to next generation techniques that have the capability to treat cancer patients from diagnosis to treatment²⁹.

Nanoscale cantilevers:

These are flexible beams resembling a row of diving boards that can be engineered to bind to molecules associated with cancerous cells.

Nanopores:

These are tiny holes that allow DNA to pass through up to only the thickness of one strand. They increase the efficiency of DNA sequencing.

Nanotubes:

These are carbon rods with a size about half the diameter of a molecule of DNA that not only can detect the presence of altered genes but also play a role in pinpointing the exact location of those changes.

Quantum dots:

Quantum dots are nanomaterials that glow very brightly when illuminated by ultraviolet light. They are capable of being coated with a material that makes the dots attach specifically to the molecule to be tracked. Quantum dots bind themselves to proteins unique to cancer cells, thus identifying tumours^{30, 31}.

Fields for application in the future in dentistry:

Nanodental techniques for major dental repair have been progressively furthered by technologic developments such as genetic engineering, tissue engineering, and tissue regeneration. There are future possibilities for new teeth formation in-vitro. Preparation of such autologous teeth that have mineral and cellular dental components will be made possible by future innovations in research. Nanotechnology will offer advanced therapeutic methods for aesthetic dentistry. All teeth that undergo treatment such as fillings or crowns will be restored with natural biologic materials in a manner that is almost identical to natural dentition.

Dentin sensitivity is another pathology that can be addressed by nanodental treatment. Many therapeutic agents provide only a temporary relief for this common, painful condition. Dental nanorobots on the other hand can seal specific tubules by using natural biomaterials and provide a quick and permanent recovery from this condition. Orthodontic nanorobots can directly manipulate the periodontal tissues which comprises of gingival, periodontal ligament, cement, and alveolar bone. They can correct, rotate, or reposition the teeth in a vertical manner within a short span of time in a pain-free manner^{1, 8}.

Scope of Nanotechnology in India:

The commercialization and research activity in India is supported by improvements in the Private Public partnership sectors and the need based research developments. To promote this innovation the Government of India has increased the central Science and Technology budget for its departments to over US $30 billion in the Eleventh Five-Year Plan (2007-2012). This has been estimated to be an increase of about five-fold from the expenditure of the previous Plan³².

Limitation faced in India:

India is still a developing country and encounters some obstacles in the path of development, namely-

· Painfully slow strategic decisions

· Sub-optimal funding in certain ventures

· insufficient engagement of private enterprises

· Problem of retention of trained manpower¹⁷

CONCLUSION:

Nanotechnology is a relatively new and developing technology whose incorporation in the various existing fields of science will soon change the face of molecular and cellular technology in the future.

In the current period the use of nanotechnology is limited to the enhancement of existing dental materials and treatment techniques. However the utilization of Nanotechnology in Dentistry giving rise to the field of Nanodentistry will facilitate great progress in oral healthcare which in turn will bring improvements in the materials, diagnostic and therapeutic methods associated with Dental care and oral hygiene. Nanotechnology in Dentistry and Medicine also provides the potential for highly specific treatment with action only on target tissues and at the same time decreasing the incidence of pain and the time period required for treatment. The field of Nanotechnology in relation to the Indian scenario is receiving much attention and Government efforts but is still in developing stages with respect to many disciplines.

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Received on 30.04.2016 Modified on 22.05.2016

Research J. Pharm. and Tech 2016; 9(8):1249-1252.

DOI: 10.5958/0974-360X.2016.00236.5