Nano Clusters-the Aesthetic Revolution- a Review

ABSTRACT

Nanoclusters and Aesthetics as made its way into various arenas of dentistry in an optimistic way. The present article will give a vision into the numerous claims of nanotechnology in Aesthetic dentistry. The disperse phase of resins is made up of a filler material which, in crux, regulates the physical and mechanical properties of the composite resins.¹ The kind of the filler, how it is attained and how much is added principally decide the physical and mechanical properties of the restorative material. The filler particles are added to the organic resin to enhance the physical and mechanical properties of the organic matrix, so incorporating as right proportion as possible of filler is an aim.¹² The filler reduces the thermal expansion coefficient and overall curing shrinkage, along with it improves handling and aesthetic results. The filler particles used vary widely in their chemical composition, morphology and dimensions. The search is currently on for materials, which provide good polish and cause less wear on the opposing tooth. Nanotechnology has led to the development of an innovative true nano composite resin characterized by containing nanoparticles measuring approximately 25 nm and nanoclusters of approximately 75 nm, which are made up of zirconium and Silica.^1,13
Keywords: Nano, Composites, Aesthetics, Restorative, Layering, Filler

INTRODUCTION

Rationalizing has become a new vogue in the domain of science and technology. Over last 20 years, Nanotechnology has ascended to become the most promising technologies, and one which will bring revolution in different fields.¹ The quality of dental biomaterials has been improved by the emergence of nanotechnology. The largest application of Nano technology has been in dental composites where they have been used to enrich the abiding properties by their size and filler loading. The word nano invents from the Greek word “dwarf”. The concept of nanotechnology was first elaborated in 1959 by Richard Feynman, a Nobel Prize winning physicist, in a lecture titled, “There’s plenty of room at the bottom”. He ended the lecture concluding “this is a development which I think cannot be avoided”. Since then, nanotechnology has found use in an innumerable application including dental materials.^1,14
The purpose of this article is to review nanocluster and true nano technology and its role in dentistry along with how it is different from Nanohybrids.

HISTORY

The thought of nanoclusters dates to primitive times. The formation of stable nanoclusters has been recommended to have occurred during the creation of the world. The first experiments to form nanoclusters was done in 1950s and 1960s.During that period, nanoclusters were produced from intense molecular beams by supersonic expansion. Since then, there has been tremendous work on nanoclusters of metals, semiconductors and composites. Nanoclusters are biologically compatible and very small, hence capable for their role in dentistry.
Why there is need of Nano clusters?
One of the key drives of using nanoparticles is to reduce the particle size than the wavelength of visible light (400 nm to 800 nm) in order to get highly translucency, high surface area to volume ratio and molecular interactions. Despite of recent improvements in physical properties and better understanding of new technology, no material has been found that is perfect for any dental application.² Dental tissues (enamel, dentin) are composed of nanoparticles, so biomaterials of a similar nature are required to closely match the properties of natural tooth. Hybrids and nanohybrids contain a broad distribution of particle sizes with resultant high strength and wear resistance. While they contain a small fraction of filler particles in the nanoparticle size range (less than 0.1µ or 100 nm), they also contain a range of substantially larger filler particles which influences the optical properties of these composites and detracts from polish retention.³ Moreover, composites using only nanoparticles of the same size have a poor effect on viscosity.
Science behind development
In 2002, 3M ESPE discovered a way to modify the sintering process to produce loosely agglomerated nanoparticles, i.e., nanoclusters (silica and zirconia) resulting in controlled particle size distribution. Although structurally different from densified particles, these nanoclusters behaved similarly to the densified particles found in other composites in terms of providing high filler loading. The addition of engineered nanoparticles to formulations containing nanoclusters reduces the interstitial spacing of the filler particles leading to higher filler loadings.^4,11
This filler technology was improved again (Filtek Z350XT), where the clusters are formed, was modified to produce less sintering. As the particles are not as strongly sintered, the cluster size range could be broadened without affecting properties such as polish retention. They contain 100% nanofiller, which means the primary particles are below 100 nanometers. These nanoclusters are also surface treated with silane to improve chemical bonding and adhesion with the organic resin matrix.^5,11

OUTCOME

Nanocluster makes a big difference between true Nano (Filtek Z350XT) and nano hybrids.^4,6 Unlike the ground filler of micro- and nanohybrids, the nanoclusters retain characteristics of the primary nanoparticles from which they are derived. So, under oral challenges such as toothbrush abrasion, the wear rate of the nanoclusters is like the wear rate of the surrounding resin matrix—which means the nanocomposite maintains a smooth surface gloss better than the hybrid composites, giving restorations unsurpassed polish retention for superb esthetics as required for Anterior and optimum physical properties and wear resistance making it excellent for posterior restorations.^4,7

APPLICATIONS OF NANO CLUSTERS IN DENTISTRY

Nano cluster as they provide natural tooth like gloss and long term polish retention, it is always preferred for various cases like Class IV build up, Midline diastema using Multilayering technique (Enamel, Dentin, Body and Translucent opacity of Filtek Z350XT) or Dual layering technique (Enamel and Dentin opacity) or single layer technique (Body opacity). It is also indicated for posterior class I and Class II restorations because of enamel like wear and high strength using layering technique.
As most of us have concerned regarding composites in a patient with excessive salivation, time consuming procedure, reduced mouth opening as even for posteriors it is incremental technique.
Patient also complains of postoperative sensitivity and fracture of restorations as one of the reasons is contamination while restoring a cavity. Recently most of us are using bulk fill posterior restorative technique for most of the Class I and Class II to overcome all these challenges. This bulk fill material also has nano cluster in its composition to enhance physical and mechanical properties in it. It can also be used as one of the choices of material with occlusal stamp technique. Even In these current times, as everyone is looking for single patient solutions for patient safety and efficacy of dentist compule form of bulk fill is always preferred.
True Nano technology is adopted by style Italiano concept because of its excellent handling, polish and strength in which they take appearance of natural teeth with chroma from dentin core and gloss from enamel layer of 0.5mm thickness.⁸
Bioclear method also recommends 3M true nano filled composites (Nano filler and Nano cluster) because these composites can be heated up to 70-degree Celsius without change in properties. In continual search to achieve good adaptation, most of the dentists place a heated 3M nano filled flowable (Z350XT Flowable) in their restoration, followed by heated Z350XT body opacity or Bulk fill compules to move the flowable, pushing out of the way. Lastly, they cure both the composite and the flowable together.^9,10

CONCLUSION

The properties of nanoclusters in combination with Nano particles offers outstanding translucency, contouring, surface finish, handling, wear resistance and polish retention and it can restore lost or damaged tissues both in Anterior and posteriors as well as direct and indirect restorations.

ACKNOWLEDGEMENT

I would like to express my gratitude to the one who supported the opportunity to complete this review article. I acknowledge Mr. Ramanathan Gopalakrishnan and Dr Manesh Lahori for his Guidance and support

REFERENCES