Abstract
Nanotechnology in dentistry refers to new generation research carried out to develop newer technologies, restorative materials and drugs of Nano dimensions. The word “Nano” refers to Nanoscale particles. Although the science of nanotechnology in dentistry is recent and less developed, but still has vast potential to show advancement and improvement in the field of dentistry. As nanotechnology is making firm grip in other fields such as drug delivery system and reducing toxicity by the emergence of more biocompatible materials. Clinicians, researchers, and manufacturers are taking keen interest and participation in the advancement of this field. This paper is an attempt in unleashing the hidden gems of nanotechnology-focusing latest developments in field restorative and surgical dentistry to enhance the quality and biocompatibility of newer generation dental materials and technology. This paper will also focus on potential hurdles encountered in the development of newer materials by utilizing the science of nanotechnology and their potential safety issues concern.
Key words: Nano dentistry, nanomedicine, nanoparticle, nanorobotics, nanotechnology
INTRODUCTION
Size does not define greatness, often surprises come in small packages. Nanotechnology is a science that deal with physical and biochemical properties of materials and its constitutions at nanoscale dimensions.[1]
The word “Nano” in Greek means “dwarf” and was coined by Prof. Keric E Dexler. Concept of nanotechnology was brought into limelight by Late Richard Feynman a Nobel Prize winning physicist in a lecture titled, “There's plenty of room at the bottom” at the annual meeting held at American Physical Society, California Institute of Technology, Pasadena, CA. (1959). Norio Taniguchi (1974), defined the term nanotechnology as a technology consisting of the processing, separation, consolidation, and formation of material by one atom or one molecule.[1]
Nanoparticles are being used by Mother Nature from the beginning of evolution.[1] Excellent and target-specific coordination demonstrated by receptors and their corresponding specific enzymes in and out of cell membranes is an unremarkable example of nanoscience that Mother Nature use.[2]
Despite decades of research in the field of dental materials and their chemistry, still no material can be considered as ideal for dental application without any limitations.[3] In addition, synthetic materials lack intelligence which makes them unable to respond to external stimuli and respond the way natural particles and molecules made by Mother Nature do.[4]
Keeping in mind the setbacks in science, biotechnology and developments in dental materials, there is an emerging need of advanced technologies in current era. Nanotechnologies are giving rise to better dental materials and improved oral health-related diagnostic methods.[3,4]
Nanotechnology has inherent excellent potential to give newer era materials and techniques, but public acceptance, human safety, and legal regulations must be adequately tackled before nanotechnology can flourish in providing quality based dental care. In addition, science of nanotechnology also possesses the risk of misuse and abuse on a scale never imagined by mankind.[5,6,7]
The main aim of this paper is to review potential areas where nanotechnology can play an important role in dentistry and to clear the mist of doubts that dental practitioners hold regarding the importance of nanotechnology in dentistry. In addition, this paper will also try to provide a glimpse of what future nanotechnology holds for dentistry.
WHEN CAN BE A NEW TECHNOLOGY BE DEFINED AS NANOTECHNOLOGY?
Three major ingredients are essential to define a technology as nanotechnology:[8]
The technology in question makes changes in the matter at a Nanoscale dimensions
Originated structures must exhibit periodic repetition (i.e., Nanoparticle should periodically repeating itself in along one or more directions)
Their novel properties and functions should be similar to parent matter or superior to parent matter in spite being nanometric.
Approaches to nano dentistry
Bottom-up approaches
This approach simply means to aggregate smaller Nano-sized particles to form complex assemblies with improved functional properties. This aims for designing custom-made Nano-sized particles which demonstrate the ability of self-assembling or self-organizing into complex high order mesoscale/macroscale particles or structures.
For example, synthetic DNA fabrication and replication by pairing nucleic acids of nanosize dimensions.
Top-down approaches
In simpler terms, means to create smaller nano-sized particles from complex structures with improved functional properties. As size of the particles in a system decreases, there is an increase in surface area resulting in pronounced increase in physical phenomena or properties due statistical as well as quantum mechanical effects.
Nano technology in dental composite restorations
The rationale to use nanoparticles in dental composites can be understood in two ways:
Use of nanoparticles makes the dental composite material more translucent hence improving esthetics [9]
To increase the wear resistance of the composite material.[9]
On the other hand, incorporation of nanoparticles in composite material have inherent challenges as nanoparticles exhibits extremely high-surface area and thus high-surface charge/gram of powder which can result in severe and almost permanent clumping agglomeration of the particles during placement and curing leading to loss or unsatisfactory achievement of the desired properties such as brittleness, cracking, or fracturing after curing.[9]
Two different commonly available varieties of nanocomposites are nanofills and nanohybrids. Nanofills mainly consist of filler particles of size 1–100 nm, while nanohybrids utilizes larger particles (0.4–5 μm), and hence are not considered as true nanofilled.[3]
Nano technology in dental implants
It is well known that implant-tissue interface is the key factor in a dental implant success which depends primarily on peri-implant healing process (Contact osteogenesis) entirely relying on deployment of bone cells from persistent blood clot to implant surface, i.e., osteoconduction phase to de novo bone formation and finally bone remodeling.[10,11]
Extent of contact osteogenesis is dependent on two factors:[12]
Intimate contact and proximity of the neck area of the implant with the adjacent surrounded gingival tissue preventing bacterial invasion and growth
Fusion of the root part of the implant with adjacent surrounded bone combined at structural and functional levels (osseointegration).
Nanoscale changes in topography and chemistry of the implant surface play a most crucial role in increasing the implant osseointegration.
Nanoscale topographic modification consists of procedures such as ionic implantation, anodization, lithography, and radiofrequency plasma treatments, which are used to induce controlled nanosurface features on dental implants such as tubes, dots, and nodules.[13,14,15,16,17] while nanoscale chemical modification of implant surface includes biofunctionalization of implant surface, i.e., immobilization of specific, active biomolecules known for their central role in osteogenesis on the surface of implants (e.g., Alkaline phosphatase, calcium phosphate (CaP), extracellular matrix proteins, adhesion molecule peptide (RGD) and coating and bone morphogenetic protein.[18,19,20,21,22]
Nano technology in local anesthesia
A future nanotechnology based local anesthetic suspensions will consist of micron size millions of active analgesic ambulating dental robots suspended in a colloidal suspension. These hi-tech anesthetic suspensions when in contact with tooth surface or gingiva will reach the pulp resulting in temporary and reversible shut down all the sensitivity or pain in the tooth specific to the area of interest that requires the treatment. Nanotechnology based anesthetic suspensions will exhibit a remarkable property of being able to be remotely controlled by dentist by an on-board computer which can be restored or reversed at any moment when the procedure will be finished.[23]
Nanotechnology in endodontic sealer
Nowadays, nanotechnology is not limited to restorative materials. Recently, a bioceramic-based nanomaterial sealer (EndoSequence BC Sealer - Brasseler USA) is developed consisting of nano-sized particles of calcium silicate, calcium hydroxide, CaP, zirconia in addition to a thickening agent. The specialty of the material is the formation of complex nanocomposite structural particles of hydroxyapatite and calcium silicate during hydration reaction in the root canal. Use of nano-sized particles helps in easy delivery of material with ultrafine capillary needle of 0.0012 size. These Nano-particulate materials provide excellent seal and dimensional stability even in complex and irregular dentinal surfaces. Once set, it forms hydroxyapatite, which not only exhibits excellent biocompatibility and bioactivity but also exhibits excellent antimicrobial properties at high alkaline pH of 12.8.[3]
Nanotechnology in dental tissue regeneration
In recent times, newer scaffold materials are being developed for teeth tissue regeneration. For regeneration of pulp, pulp-derived stem cells from third molars are treated in laboratory to be purified and grown in sheets on scaffolds.[24] These scaffolds act as a blueprint and are structurally composed of nanofibers of fibronectin or biodegradable collagen Type I and act as precursor for the formation of nanofiber mesh for supporting the growth of cells during tissue engineering. Recently, an injectable version of self-assembling collagen-I scaffold with inclusion of exfoliated stem cells from teeth have shown excellent results in the formation of tissue that resembles functional-like pulp and odontoblasts.[25,26,27] Other materials which had shown a great future are Puramatrix (repeating units of amino acids like alanine, arginine and aspartate) and natural silk-based nanomaterials. Although tissue regeneration techniques are not practical and feasible in implementation at present, but who knows what the future holds for us.[28,29]
Nanotechnology in surgical field
Development of Nano sized stainless-steel crystals had made it possible to develop Nano sized suture needles and tweezers giving a promising future for the surgeries to be carried out even at the cellular level. These Nano sized instruments will not only exhibit good ductility but also exceptional strength and corrosion resistance.
Carbon nanotubes, a nanomaterial based catheters are playing a remarkable role in minimally invasive surgery by exhibiting increased strength, flexibility and non-thrombogenic effect. Thus avoiding the issue of thrombus formation on the device surface.
Advances in the knowledge about anti-infective properties of Silver metal at Nano scale had let to the development of Nano porous silver powder which enters the wound through body fluids and can reportedly kill bacteria in minutes. These properties are properties are remarkably increased by greater surface area.[30]
Nanotechnology in correcting bone deformities and defect
Nanophase materials had shown promising results in the treatment of various bone deformities and defects. Basically, Nanophase hydroxyapatite (HA) and Nanophase carbon are the two main promising types of nanophase materials which are used for treatment of bone defects.
Nanophase HA shows a superior osteoblastic adhesion as compared to traditional HA. Commonly used nanoparticles of HA used for the treatment of bone defects are NanOSSTM HA (Angstrom Medica, USA), Vitosso (Orthovita, Inc, USA) HA + tri-calcium- phosphate (tri CaP), and Ostim HA (Osartis GmbH, Germany).[30]
In contrary to Nanophase HA, the Nanophase carbon shows excellent biomechanical properties due to a combination of not only being Nano-sized but also similar to natural HA. Thus, making it a most potential future material for the correction of maxillofacial defects and maxillofacial implant material.[30]
Nanotechnology in local drug delivery
Nanotechnology has proved itself as a potential frontier in drug delivery to specific cells or localized area of interest using nanoparticles. Localized and controlled drug delivery may significantly reduce drug dosage-related side effects by selectively depositing the controlled amount of drug in close proximity of the area of interest. This in the future may play an important role in reducing the cost and human suffering. One of the most important implications of such nanotechnology-based drugs is cancer treatment which shows tremendous side effects and financial burden. Examples of such drugs in the current research are blocking copolymers, nanoporous materials, and dendrimers which form micelles necessary drug encapsulation and controlled release. Other most important frontier in this field are gold nanoshells to detect and treat cancerous tumors.[31]
Recently, certain characteristic novel drug delivery systems had been developed by emulsification and diffusion process in which nanoparticles are loaded with triclosan, which can play a role of game changer in halting the advancement of periodontal diseases. This nanotechnology-based local drug delivery system behaves as a homogeneous polymer matrix-type delivery system, in which drug molecules are encapsulated with biodegradable Nanospheres which can be controlled externally for timely release of drugs by controlled disintegration in a particular location and time. One such good example is arestin which consist of tetracycline incorporated into biodegradable microspheres for local drug delivery targeted to periodontal pockets.[32,33]
Nanotechnology in treatment of gingival and periodontal diseases
Area-specific configured nanorobots could help in the treatment of dental pathologies by destroying pathogenic disease-specific bacteria harboring the plaque and other specific places while causing no harm to several harmless and beneficial oral microflora to flourish in a healthy ecosystem. This may have a potential benefit against gingival and periodontal related diseases as well as halitosis.[34]
Nanotechnology in dental hypersensitivity
Dentin hypersensitivity results from fluid dynamics-based phenomenon where the pressure is transmitted hydrodynamically to the underlying nerves in pulp resulting in the generation of stimulus. Hypersensitive teeth exhibits eight times increased response of dentinal tubules as compared to nonsensitive teeth. Nano robots can help in overcoming the dentinal hypersensitivity by occluding these dentinal tubules in more target specific and precise approach, thus relieving patients suffering by providing long-lasting cure.[35]
Nanotechnology in orthodontics
Friction is one of the major issues affecting the alignment or retraction of teeth during orthodontic treatment. This issue in the past was overcome by applying higher forces resulting in undesirable anchorage loss. Recent advances in knowledge of orthodontics and nanotechnology had paved an alternate path to counteract these undesirable issues, and one such advancement is Nano-coated arch wires and brackets to reduce undesirable friction. Promising results have been obtained by in-vitro experiments being carried out by coating Nickel-Titanium (NiTi) and stainless steel wires with nanoparticles of tungsten disulfide (WS2) and Nickel-phosphorous Nano particles.
Hollow wires exhibiting an excellent shape-memory and super elasticity are prepared by ultrasonic spray pyrolysis (USP) technique in which wires are coated with composite nanoparticles e.g. NiTi / Ni-TiO2 via a technique called electrospinning followed by removal of wire in order to produce a hollow wire for orthodontic purposes.
Who knows in future Orthodontic Nano robots can manipulate periodontium resulting in rapid, precise, and painless tooth movements within minutes to hours.[36]
Nano technology in oral hygiene maintenance
Continuous removal supra and subgingival plaque and calculus through targeted nanorobots incorporated in future dentifrices will not only help in proper oral hygiene maintenance and preventing the occurrence of dental and periodontal diseases but will also keep a check on bacteria responsible for the production of volatile compounds causing halitosis.[37]
Nanotechnology coupled laser plasma application in periodontics
Nanoparticles of titanium dioxide (TiO2) when applied on human skin surface by means of gel-like emulsion, exhibits extraordinary properties and effects-like shock wave, microabrasion, and stimulation of collagen production by degradation when irradiated with laser pulse. This remarkable properties of TiO2-based nanoparticles coupled with laser irradiation can be utilized in varieties of procedures such as depigmentation of gingiva, soft-tissue incision without anesthesia and periodontal disease treatment.[30]
Nanotechnology in early detection of oral cancer
One of the latest advancement in Nanotechnology is the invention of “Quantum dot.” These “Quantum dots” are tiny nanoparticles measuring same as that of a size of protein molecule or DNA of short sequence acting as photosensitizers and carriers. These nanoparticles show a very bright luminance when viewed under ultraviolet light. These “Quantum dots” can be coated with a material showing affection to cancerous cells to be tracked and help locating and detecting cancer cells by binding themselves to protein sequence unique to cancer cells, thus aiding in early detection.[38]
CONCLUSION
The field of nanotechnology has bright prospects as this evolutionary domain of science offers the possibility of great advances and improvement in the field of dentistry with an extrapolation of current resources to a new scale. Further researches pertaining to dental health care should emphasize on methods of drug delivery system, reducing toxicity by emergence of more biocompatible materials. The need of hour is implication of wide scope of research on this technology in various fields including general and dental care, biomedicine, food, and agriculture.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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