|Year : 2015 | Volume
| Issue : 2 | Page : 78-83
The changing phase of prosthodontics: Nanotechnology
Anne Gopinadh, Manne Prakash, Kalluri Lohitha, Kadiyala Krishna Kishore, Anche Sampath Chowdary, J. Ravi Rakesh Dev
Department of Prosthodontics, Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh, India
|Date of Web Publication||11-Dec-2015|
Department of Prosthodontics, Sibar Institute of Dental Sciences, Guntur - 522 009, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Science is presently undergoing a great evolution, taking humanity to a new era: The era of nanotechnology. Nanotechnology is the field of science and technology pertaining to the creation and use of materials or devices at nanometer scale. Nanoscale is small in size, but its potential is vast. Since 1990s, nanotechnology has been exploited for potential medical and dental applications. Nanotechnology has numerous applications in the field of nanomedicine, nanomaterials, nanorobotics, implantology, and biotechnology. Nanomaterials in dentistry can be metals, ceramics, polymers, implant modifications, and composite materials that demonstrate novel properties when compared with conventional materials due to their nanoscale features. The present article focuses on the various applications of nanotechnology in the field of dentistry, especially prosthodontics.
Keywords: Nanodentistry, nanomaterials, nanotechnology, prosthodontics
|How to cite this article:|
Gopinadh A, Prakash M, Lohitha K, Kishore KK, Chowdary AS, Dev JR. The changing phase of prosthodontics: Nanotechnology. J Dent Allied Sci 2015;4:78-83
|How to cite this URL:|
Gopinadh A, Prakash M, Lohitha K, Kishore KK, Chowdary AS, Dev JR. The changing phase of prosthodontics: Nanotechnology. J Dent Allied Sci [serial online] 2015 [cited 2019 Jun 25];4:78-83. Available from: http://www.jdas.in/text.asp?2015/4/2/78/171523
| Introduction|| |
At present, the revolutionary development of nanotechnology has become the most highly energized discipline in science and technology. It is "the art and science of manipulating matter at the nanoscale (1-100 nm)."  National Nanotechnology Initiative defined nanotechnology as the "Research and technology development at the atomic, molecular and macromolecular levels in the length scale of approximately 1-100 nm range, to provide a fundamental understanding of phenomena and materials at the nanoscale and to create and use structures, devices and systems that have novel properties and functions because of their small and/or intermediate size." The future trend in dentistry is nanotechnology, aptly termed as nanodentistry. 
| History of Nanotechnology|| |
Nanotechnology is not a new term. This phenomenon is seen in nature in the locomotor organs of various organisms and our biological system as ferritin in red blood cells. Although nanotechnology has been around since the beginning of time, the discovery of nanotechnology is widely attributed to the American Physicist and Nobel Laureate, Dr. Richard Phillips Feynman. The first use of the word "nanotechnology" attributed to Taniguchi in 1974. Later, in 1986, Eric Drexler introduced and popularized the term "nanotechnology" in his book "Engines of Creation." , It was introduced into dentistry first as nanocomposites in the year 2002 by Filtek Supreme.
| Need for Nanotechnology in Dentistry|| |
Materials reduced to the nanoscale can suddenly show very different properties enabling unique applications. For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum); stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). Materials such as gold, which are chemically inert at normal scales, can serve as a potent chemical catalyst at nanoscales. Much of the fascination with nanotechnology stems from these unique quanta and surface phenomena exhibited by the matter at the nanoscale. It is this desirable alteration in the physicochemical properties of a bulk material when reduced to a nanoscale that highlights the importance of applied nanotechnology in various fields including dentistry.
| Approaches in Nanotechnology|| |
Three approaches have been followed in the production of nanoparticles, namely bottom up approach, top-down approach, and functional approach.  The functional approach disregards the method of production of a nanoparticle, and the objective is to produce a nanoparticle with a specific functionality.
The fields of science and technology have witnessed the fabrication of several nanoparticles that we come across and use in our daily lives, many a times not realizing it is part of the future revolution. The various nanoparticles are nanopores, nanotubes, quantum dots, nanoshells, dendrimers, liposomes, nanorods, fullerenes, nanospheres, nanowires, nanobelts, nanorings, nanocapsules.  This list of nanoparticles is by no means exhaustive.
| Nanotechnology in Prosthodontics|| |
Nanotechnology has been incorporated in various aspects of removable and fixed prosthodontics.
In removable prosthodontics
Incorporation of carbon nanotubes [Figure 1] into heat cure monomer has reduced the polymerization shrinkage and improved the mechanical properties. 
Incorporation of metal oxide nanoparticles [Figure 2] into conventional polymethyl methacrylate has improved the flexural strength, antimicrobial property and reduced porosity.
Main reasons for mechanical failure in maxillofacial prostheses include tensile and tearing loads. The use of polyhedral oligomeric silse squiox, as a reinforcing agent, has enhanced the tensile and tearing strengths of conventional materials. Nanocomposite denture teeth [Figure 3] are stain and impact resistant with lively surface texture. 
In fixed prosthodontics
The introduction of nanofillers into the resin matrix has led to the development of newer light cure nanocomposites [Figure 4] , with numerous advantages as:
- Highest mechanical strength.
- Low polymerization shrinkage.
- Low thermal expansion coefficient.
- Low water sorption.
- Excellent marginal integrity.
- Excellent handling characteristics.
The use of silica nanofiller nanotechnology contributes to higher bond strength performance and provides a stable, filled adhesive [Figure 5]. When used as coating agent over esthetic restorations, it produces stain and wear resistant surface with smooth luster. ,
Use of nanocare gold [Figure 6] before embedding composite/ceramic restorations enhanced adhesive and antibacterial properties. 
Nanofillers are integrated in the vinylpolysiloxanes,  producing a unique addition siloxane impression material with better flow, improved hydrophilic properties, and enhanced detail precision [Figure 7].
|Figure 7: Addition siloxane impression material with incorporated nanofillers|
Click here to view
Nanofillers in nano-optimized moldable ceramics  enhance polishability and reduce wear. Nanopigments improve the esthetics. Nanomodifiers improve the handling characteristics [Figure 8].
The use of newer resin luting agents  with incorporation of nanomodifiers has improved the mechanical properties [Figure 9].
In the field of implantology, coating the implant surface with nanoceramics, such as hydroxyapatite (HA) particles and nanopolymers, has markedly enhanced interfacial attachment to bone tissue with advantages of faster healing time, enhanced bone formation, firmer implant bone attachment, and a reduction of metallic ion release.  The use of nano-titanium implants [Figure 10] wherein modifying the surface topography of the implant down to its nanosize has been recognized to offer fast and optimum osseointegration. This approach is based on the basic concept of significantly increasing the mechanical bonding of the cells by roughening its surface to a nanolevel in order to induce better implant stability. 
| Applications of Nanotechnology in Other Fields of Dentistry|| |
Nanodentistry will make possible the maintenance of comprehensive oral health by employing nanomaterials, biotechnology including tissue engineering, and ultimately dental nanorobotics.
Application in local anesthesia
To induce oral anesthesia in the era of nanodentistry, a colloidal suspension containing millions of active analgesic micron-size dental nanorobots will be instilled on the patient's gingiva, then they reaches the dentin by migrating into the gingival sulcus and passing painlessly through the lamina propria. On reaching the dentin, the nanorobots enter 1-4 μ diameter dentinal tubules and proceed toward the pulp, guided by a combination of chemical gradients, temperature differentials, and even positional navigation, all of which are controlled by an onboard nanocomputer. Assuming a total path length of about 10 mm from the tooth surface to pulp and a very modest travel speed of 100 μ/s, a nanorobot completes the journey into the pulp chamber in approximately 100 s. 
Nanodental techniques for major tooth repair may evolve through several changes of technological development, first using genetic engineering, tissue regeneration, and later growing whole new teeth in vitro and installing them. Ultimately, nanorobotic manufacturer and installation of a biologically autologous whole replacement tooth including both mineral and cellular components e.g., complete dentition replacement therapy, should become feasible to be undertaken within the time and economic constraints of an ordinary office visit using an affordable desktop manufacturing facility in dentist's office. 
Reconstructive dental nanorobots could selectively and precisely occlude selected tubules in minutes, using native biological materials, offering patients a quick, and permanent cure. 
Orthodontic nanorobots can directly manipulate the periodontal tissues such as gingival, periodontal ligament, cementum and alveolar bone, causing rapid, painless tooth straightening, rotation and vertical repositioning within minutes to hours, in contrast to traditional orthodontic techniques which require weeks to months. 
Nanorobotic dentifrice (dentifrobots)
Effective prevention has reduced caries in children, and a caries vaccine may soon be available but a subocclusal-dwelling nanorobotic dentifrice delivered by mouthwash or toothpaste could patrol all supragingival and subgingival surfaces at least once a day, metabolizing trapped organic matter into harmless and odorless vapors and performing continuous calculus debridement. These invisibly small (1-10 μ) dentifrobots, perhaps, numbering 103-105 nanodevices per oral cavity and crawling at 1-10 μ/s would be inexpensive purely mechanical devices that would safely deactivate themselves if swallowed and would be programmed with strict occlusal avoidance protocols. Properly configured dentifrobots could identify and destroy pathogenic bacteria residing in the plaque and elsewhere while allowing the 500 species of harmless oral microflora to flourish in a healthy ecosystem. Dentifrobots would also provide a continuous barrier to halitosis since bacterial putrefaction is the central metabolic process involved in oral malodor. With this kind of daily dental care available from an early age, conventional tooth decay and gingival disease will disappear into the annals of medical history. 
Nano whitening toothpaste is a toothpaste that contains synthesized hydroxyapatite, a key component of tooth enamel, as nanosized crystals. It has been proven to freshen breathe as well as whiten teeth. Nanotechnology toothpaste has been shown to be harmful because some of the nanotechnology toothpastes are made with silver hydroxyapatite. 
Suture needles incorporating nanosized stainless steel crystals have been developed. Trade name: Sandvik Bioline, RK 91TM needles (AB Sandvik, Sweden). 
In 1999, Philip Kim and Charles Lieber at Harward University created the first general purpose nanotweezer. Its working end is a pair of electrically controlled carbon nanotubes made from a bundle of multiwalled carbon nanotubes. To operate the tweezers, a voltage is applied across the electrode causing one nanotube arm to develop a positive electrostatic charge and the other to develop a negative charge. 
Nanotechnology in periodontics
Nanomaterials for periodontal drug delivery
Drugs can be incorporated into nanospheres composed of a biodegradable polymer thus allowing for timed release of the drug as the nanospheres degrade. Recently, triclosan-loaded nanoparticles were found to be effective in achieving reduction of inflammation. Tetracycline incorporated into microspheres is available as Arestin for local drug delivery into periodontal pocket. A nanostructured 8.5% doxycycline gel was observed to exhibit favorable results following experimental periodontal disease in rats. 
Lab-on-a-chip (LOC) is a device which integrates several laboratory functions on a single chip. Assays are performed on chemically sensitized beads populated into etched silicon wafers with embedded fluid handling and optical detection capabilities. This device has been used to assess the levels of interleukin-1 beta, C-reactive protein, and matrix metallo proteinase-8 and other molecules in whole saliva, which are potential use of these biomarkers for diagnosing and categorizing the severity and extent of periodontitis. 
Laser plasma application for periodontics
When nanoscale (20-50 nm) titanium dioxide (TiO 2 ) particle sizes are presented on the human skin in the form of a gel-like emulsion, these exhibit some interesting properties such that when irradiated with laser pulses, these particles can be optically broken down with accompanying effects such as shock wave, micro-abrasion of hard tissue, and stimulation of collagen production. Its clinical applications include periodontal treatment, depigmentation, incision of soft tissue without anesthesia, and caries preparation. 
Periodontal bone grafts
With both micro-porosity and nanoporosity, these have greater surface area as compared to other synthetic bone grafting materials, allowing for ideal bone regeneration. 
These include liquids and pastes that contain nanoapatites for biofilm management at the tooth surface, and products that contain nanomaterials for the remineralization of early sub-micrometer-sized enamel lesions. New silver nanotechnology has been documented to be effective against biofilms. Silver has high affinity for negatively charged side groups sulfydryl, carboxyl, and phosphate on the cell membrane of the microbes. 
Easy-to-clean, wear-resistant, and biocompatible nanocomposite surface coatings for biofilm management are close to being used in the dental practice. 
It is an ultra-thin, ultra-glide, completely non-shredding floss with excellent tensile strength. The unique nanostructure of dental tape allows for the addition of flavors and delivery of medications. 
Biodegradable nanofibers are used to produce hemostasis. Nanocrystalline silver particles with antimicrobial properties are used on wound dressings. 
Digital dental imaging
Advances in digital dental imaging techniques are expected in nanotechnology. The radiation dose obtained using digital radiography with nanophosphor scintillators is diminished, and high-quality images are obtained. 
Nano bone fibers
These have a tensile strength 100 times that of steel (polyphosphazene nanofibers). These are assuming great interest in local drug delivery system because of their superior properties. 
Photosensitizers and carriers
These reside on the surface of the target cell and when activated by ultraviolet light, produce free oxygen radicals which are harmful to the target cells. 
The new developed deep probe detectors consisting of the electromagnetic spectrum will be available to screen the human body to reveal hidden matter such as deep tumors and occult caries in teeth. This is known as Terahertz radiation, which lies in between light and radio waves in the spectrum. 
Nanotechnology in endodontics
Nanoparticles reinforced glass ionomer cement
Hydroxyapatite and fluorhydroxyapatite nanoparticles with fluoride substitution levels ranging from 0% to 95% are added to improve the mechanical properties and fluoride releasing ability of the traditional glass ionomer cement.
Nanoparticles as antimicrobial agents
Nano particulates display higher antibacterial activity because of their polycationic or polyanionic nature. These disinfect the canal by removing the residual microbes in the canal and enhance the antibacterial action of the intracanal medicaments. 
Nanotechnology based root-end sealant
Nanomaterial enhanced retrofill polymers (NERPs) provide superior strength and contour to the tooth structure. Bio-aggregate, white nanoparticle ceramic cement is new-end filling material composed primarily of calcium silicate, calcium hydroxide, and hydroxyapatite. NERP materials were found to significantly reduce the micro-leakage, demonstrating their ability to seal effectively. 
Surface disinfectants in sterilization
A new sterilizing solution following nanoemulsion concept has been developed by Gandly Enterprises Inc., Florida, the USA. Nanosized oil droplets attack and destroy the pathogens. Eco-True is a surface disinfectant that safely kills 100% of HIV and other particles. It has been used to sterilize tools and incisions to prevent postoperative infections. 
Protective clothing and filtration masks using antipathogenic nanoemulsions and nanoparticles, medical appendages for instantaneous healing and bone targeting nanocarriers such as calcium phosphate based biomaterials are developed. 
| Potential Hazards of Nanoparticles|| |
The extensive application of nanomaterials in a wide range of products for human use possesses a potential risk for toxicity risk to human health and the environment. American health association concluded that short-term exposure to elevated particulate matter concentrations in outdoor air significantly contributes to increased acute cardiovascular mortality, particularly in at-risk subset of the population.  An in vitro cytotoxicity assessment of an orthodontic composite containing TiO 2 nanoparticles by Heravi et al. revealed that orthodontic adhesive containing TiO 2 nanoparticles indicated comparable or even lower toxicity than its nanoparticle free counterpart. It was concluded that incorporation of 1% by weight of TiO 2 nanoparticles to the composite structure does not result in additional health hazards compared to that occurring with pure adhesive.  In another study, it was reported that leached components from composite material induced embryotoxicity in mouse blastocyst in vitro while no toxicity was observed when subcutaneously implanted in vivo. 
| Conclusion|| |
Nanotechnology is set to revolutionize clinical dental practice. In no distant future, oral health care services will become less stressful for the dental surgeons, more acceptable to patients and the outcome will significantly become more favorable. Rapidly progressing investigations will ensure that developments that seem unbelievable today are possible in the future. However, as with all technologies, nanotechnology carries a significant potential for misuse and abuse on a scale and scope never seen before if not properly controlled and directed. 
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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