By Dr. Rashid Hassan
Nanotechnology is used to characterize and tailor-make the properties and performance of a material at an atomic or molecular level. Richard Feynman in 1959 was the first one to set up the concept of nanotechnology. The idea was entitled as “There is plenty of room at the bottom” and was presented at an American Physical Society Meeting at the California Institute of Technology in 1959. The term nanotechnology was defined by Dr. Nori Taniguci IN 1974 as “the processing of separation, consolidation and deformation of materials by one atom or molecule”. This idea of Nanotechnology was later probed in depth by Dr. Drexier who published a book entitled “Engines of Creation-The Coming Era of Nanotechnology” around late 1980s. In 1991, the publication by Sumio Lijima “Helical microtubules of Graphitic Carbon” boosted nanotechnology research to the next level.
Despite the better understanding of the chemistry, properties and recent advancements, no material has come even close to be rated as an ideal dental material for any specific application in Dentistry. A material good in aesthetics compromises on the properties and vice versa. Nanotechnology helps to minimize the drawbacks to a minimum level and enhance the properties as close as possible to an ideal dental material. Top Down and Bottom up are the two types of approaches used in nanotechnology for creating smaller or better materials with enhanced properties as compared to the macro level materials.
Top Down Approach is based upon a solid state processing of materials that is through Milling, Machining and Lithography. The Top Down Approaches such as Chemical Vapor Deposition (CVD), Wet and Plasma Etching and Monolithic Processing are used to fabricate functional structures at a Micro or Nano scale. CVD technology is used for coatings of Medical Implants and stents in order to enhance the blood flow and increase the biocompatibility. On the other hand Bottom Up Approach uses the fabrication of materials via Edifice up the particles by harvesting the atomic elements. Growth of a material and a very organized chemical synthesis as the basis of Bottom Up Approach. Protein synthesis and repairing of cells tissues and organ systems are the best examples of Bottom Up Approach in Nanomaterials.
The remarkable research on nanomaterials in the recent years has moved the concept of nanotechnology from theoretical idea to the world of clinical dental practice. Currently there is a wide range of nanomaterials applications in different specialties of dentistry such as Conservative dentistry, Prosthodontics, Oral Implantology, Periodontics, Preventive dentistry and Endodontics. Regarding conservative dentistry, there has been a drastic evolution in recent years particularly in aesthetic restorative materials. Nanotechnologies have been applied for the manufacturing of Dental Composites (Nano-Composites), Glass Ionomer Cements (Nano-Ionomers) and Endodontic Sealers.
At the time when Bowen developed {Bis-GMA} resin and used Silane coupling agents for dental composites, around the same era noble laureate Sir Richard Feynman introduced the word “Nano” which proved to be a landmark for advances in Dental Composites.
Nancomposites include Resin matrix and Nanoscale particles. In nanocomposites it is possible to operate the mechanical properties by incorporating the secondary nanoparticles to obtain the same characteristic features of natural bone. The properties of nanostructured composite materials are controlled by their processing, synthesis methodand chemistry.
Conventional Resin Based Composites use organic polymer matrix mainly Bis-GMA and TEG-DMA. Bis-GMA being viscous is mixed with a more fluid and less viscous monomer to obtain a workable viscosity. In order to overcome the issues of shrinkage, aging and environmental issues, Bis-GMA is replaced by UDMA. Good translucency, contouring and surface finish are best in case of nanocomposites. Currently the research is now being focused on reducing the polymerization shrinkage which is a major drawback in conventional dental composites. Addition of monovinyl methacrylate in the resin by Decker has resulted in enhanced polymerization kinetics and increased mechanical properties. They are also referred to as Ultra Rapid Monomethacrylates.
Nanofills and Nanohybrids are the two most commonly available Nanocomposites. Nanofills contain inorganic filler nanomparticles in the range of 1 to 100nm whereas nonohybrids are composed of large particles within the range of 0.4 to 5 µ. Due to this they are not truly nanofilled that’s why they are called as nano hybrids. The key purpose of using nanoparticles is to reduce the particle size than the wavelength of visible light (400 nm to 800 nm). This helps in obtaining highly translucent materials, high surface area to volume ratio and molecular interactions as the polymer size range is usually in the same dimensions.
There is no doubt that demand for an ideal dental biomaterial is on a rapid rise in order to enhance the properties of all the dental materials and facilitate the patients. The last decade or so has seen remarkable advances in the field of nanotechnology in dentistry, particularly in the field of nanocomposites.
