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LEIPZIG, Germany: It is said that it is the small things that make a big difference. This applies literally to the field of nanotechnology, which over the years has been increasingly applied in various areas. Today, nanotechnology is used in everything, from developing smart fabrics that can be used for personal thermal management to methods of curing cancer, and has also found its way into dental applications. Nanomaterials are used as filling materials in restorative dentistry and endodontists work with nanotechnology-based root-end sealants. In implantology, nanomaterials are employed for tissue regeneration, as implant materials and also to optimise the surfaces of dental implants, since these surface characteristics are crucial for successful osseointegration.
Dr Eric Drexler, often described as “the founding father of nanotechnology”, introduced the concept. In 1981, he published a paper which established fundamental principles of molecular engineering and outlined development paths to advanced nanotechnologies. Nanotechnology has been defined as the science of the design and application of materials whose smallest functional organisation, in at least one dimension, is on the nanometre scale. As nanomedicine advanced, dentistry also started evolving in the field of nanotechnology and thus the term nanodentistry was born. According to Dr Katarzyna Gurzawska, academic clinical lecturer in oral surgery at the school of dentistry at the University of Birmingham, it was introduced by research scientist Robert Freitas in 2000, who had the vision of using nanorobots for orthodontics and dentition regeneration, and nanomaterials and robots in dentifrices. “Although most of his ideas were, and remain, science fiction, these ideas are gradually being realised in practice,” she commented.
Nanodentistry in implantology
Nanotechnologies are increasingly being used for surface modifications of dental implants, as surface properties play an important role in achieving and maintaining their long-term stability in bone tissue. Nanostructured surfaces can enhance osseointegration, bone formation and also antibacterial activities, as reported previously by DTI. According to Prof. Ann Wennerberg from the Department of Prosthodontics at Sahlgrenska Academy at the University of Gothenburg in Sweden, “In vivo and in vitro studies have demonstrated that nanostructures influence cell behaviour and bone formation in terms of improved adhesion and proliferation”. Ultimately, these aspects increase the prognosis of the implant and thus decrease the length and number of appointments for patients.
“Scientists believe that nanoparticles mimic the natural structure of human molecules and in this way directly stimulate bone cells to create bone around implants”
Swiss based implant manufacturer Straumann said, when one of their implant surfaces was launched 14 years ago: “SLActive made faster treatment, shorter healing time and highly predictable outcomes a reality. Now, the extensive healing potential of SLActive can be seen even in medically compromised patients and other challenging treatment protocols.”
According to Gurzawska, the mechanism of nano-coatings is not yet fully understood. She continued: “However, scientists believe that nanoparticles mimic the natural structure of human molecules and in this way directly stimulate bone cells to create bone around implants.”
Different types of nanostructured implant coatings that have been developed include nanostructured diamond, nanostructurally processed hydroxyapatite and nanostructured metal-ceramic coatings. Today, there are several implants available on the market that claim to possess such nanoscale characteristics. Comparative studies performed in vitro and in vivo preclinical models have shown that nanomodified surfaces yielded a result superior to that of conventional surfaces. Nevertheless, in the absence of long-term randomised controlled trials it cannot be stated with certainty whether these nanostructured surfaces indeed have a significant clinical impact. Therefore, in order to acknowledge the full potential of this fairly new field, more research is required.
Nanodentistry as growing market
Some of the major players in the nanotechnology dental implant market are Nobel Biocare, Dentsply Sirona, Straumann, 3M, Danaher, Ivoclar, Heraeus Kulzer and Zimmer Biomet Dental. Investing in the research and development of nanomodified dental implants will help to strengthen the position of these leaders on the global market.
According to a market report, owing to the claimed advantages of nanostructured dental implants, demand in this area is expected to increase in the coming years. In addition, high numbers of edentulous people in the western world and rising disposable income in Asia Pacific, Africa and South America are expected to drive demand in the near future. Another factor might be that the general awareness of dental care is increasing and this, in interaction with the other factors, will result in the expansion of the global nanotechnology dental implants market. For the moment, North America and Europe dominate the global nanotechnology market after recovering from a significant slump caused by the economic crisis in 2009.
According to Straumann, the company started its research in nanotechnology in 2010 and published its first papers on the topic in 2012 and 2013. “Today, SLActive is available in Europe, North America, Latin America and in more than 40 markets in Asia Pacific regions. The demand is especially high in Europe, US, Brazil and Japan and by now, it has been sold more than 6.5 million times.”
“The majority of our customers are switching to implants with the new surfaces”
The Xeal abutment surface, produced by Nobel Biocare, an implant manufacturer from Switzerland, is directly sold in all major European markets as well as in Canada, Hong Kong, Australia and New Zealand. It is also available in dealer markets such as Croatia, Turkey, Greece, Indonesia and Vietnam, according to the company. “The Xeal and TiUltra surfaces are based on decades of experience in anodising implant surfaces and developing the products took about five years. This year, clinical studies on the topic have been published in a supplement of the Clinical Implant Dentistry and Related Research Journal and further studies will follow in the course of next year,” added Nobel Biocare.
The report furthermore states that dentists and general practitioners are using this new technology more and more in comparison with available alternatives. “The majority of our customers are switching to implants with the new surfaces, meaning NobelActive and NobelParallel,” confirmed Nobel Biocare.
In answer to the question of whether she has already worked with nanomodified surfaces, Wennerberg replied: “Yes, in fact several of the most sold implants have nanostructures on their surface, spontaneously formed as a result of the etching and cleaning procedure. Well-known brands are TiUnite from Nobel Biocare, OsseoSpeed from Dentsply Sirona and SLActive from Straumann. Then there are others with an intentionally applied coating such as NanoTite from Zimmer Biomet, which possesses a calcium phosphate (CaP) coating.”
Could “nano” be too small?
Even though nanotechnology provides humankind with many solutions, it may also hold risks. Nanomaterials are more reactive and possess an increased rate of absorption through skin, lungs and digestive tract. Therefore, continuous use can lead to nanoparticles being transported via the blood to various organs, where they accumulate. They may cause inflammation in the lungs and can cause mutations. In addition, scientists are concerned about risks for soil and plant life.
“The clinical impact of nanofeatures remains unknown. It is very difficult to separate the influence of nanoparticles since there are so many other factors influencing the clinical outcome. Particle release has been discussed as a possible danger that may enhance inflammatory response; however, so far, the clinical impact of this potential factor is unknown too,” said Wennerberg.
In April 2017, the European Parliament approved a regulation on medical devices, that among other topics, dealt with the issue of nanotechnology. The paper stresses the importance of a uniform definition for nanomaterials in order to guarantee a high level of health protection, free movement of goods and legal certainty for manufacturers. The regulation defines nanomaterials as a “natural, incidental or manufactured material containing particles in an unbound state or as an aggregate or as an agglomerate and where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1–100 nm”. Manufacturers are advised to “take special care” when using nanoparticles for which there is a high or medium potential for internal exposure.
“The clinical impact of nanofeatures remains unknown. Particle release has been discussed as a possible danger that may enhance inflammatory response”
According to the European Union Observatory for Nanomaterials, a new EU regulation on medical devices, that will become applicable in spring 2020, includes specific requirements for devices incorporating or consisting of nanomaterials. This regulation specifies the requirement of reducing the risk of nanoparticles being released into the user’s body. Moreover, the regulation classifies medical devices which have been manufactured with the help of nanomaterials as Class III—the highest risk class—if they present a high or medium potential for internal exposure and should be more strictly evaluated.
When asked about her view on the upcoming EU regulation, Gurzawska replied: “In my opinion, new medical devices should be strictly evaluated and follow all ISO standards. The ISO standards are however limited in nanotechnology, therefore extended tests in vitro, in vivo and human trials should be performed before the new product is introduced.”
Besides the concern of regulations to protect patients, nanotechnology poses a couple of other challenges. According to a 2015 study, these include, among many other things, engineering, biological and social aspects. Firstly, owing to their size, positioning and assembling nanoparticles precisely is very demanding. Secondly, nanomaterials can be pyrogenic, making it more difficult to manufacture biofriendly products. Ethics and public acceptance are another major concern.
Only time will tell
Nanotechnology and thus nanodentistry are relatively newer fields, in which neither the benefits nor the possible threats are yet completely realised. Therefore, more research and long-term clinical trials are needed in order to increase the quality of dental implant care in the future. The market for nanomodified dental implant surfaces is expected to grow, owing to the improved results already attributed to them and an increasing number of edentulous people, in combination with rising disposable incomes in different regions of the world. The previously mentioned study claims that “nanotechnology conceptually has reached to the level, where one day it would be possible to repair the whole tooth.” Whether or not this will become a reality, only time will tell.
In the future, in Gurzawska’s opinion: “Nanotechnology will be a tool to create smart biomaterials to deliver organic and inorganic molecules, that will directly stimulate or block specific human cells to regenerate tissue and prevent inflammation.”