Scientific changes have made our perception, our way of thinking and attitude about today and tomorrow. Keeping this in mind the increasing number of beneficiary fields, we can establish the fact that even the field of dentistry is not spared. In recent years, lots of researches have been launched on nanomaterials for biomedical applications and shown that the performances of many biomaterials used in prosthodontics have been significantly enhanced after their scales were reduced by nanotechnology, from micron-size into nano size. This is an attempt to give an overview about the nanotechnology, nanomaterials and its applications in the field of Prosthodontics.
Key words: Nanoworld, Nanodentistry, Prosthodontics
“You have to be able to fabricate things, you have
to be able to analyze things, and you have to be
able to handle things smaller than ever imagined
in ways not done before” - Cloude Levi Strauss and Winfred Phillips. At present the science is
undergoing a great evolution, taking humanity to
a new era, “The Era of Nanotechnology”. Nanotechnology is the scientific ability to control and
restructure the matter at the atomic and molecular
levels within the nanoscale. Also, nanotechnology
refers to using minute machinery that is capable of
manipulating matter on an extremely small scale
at dimensions between approximately 1-100 nm
where unique phenomenon enables novel applications. In other terms Nano technology means
science of small1
. 1nm is 1 billionth a meter.
Nanotechnology improves existing processes,
materials and applications by scaling them down
to the nanoscale in order to ultimately fully exploit
the unique quantum and surface phenomena that
matter exhibit at nano scale. Also, nanotechnology
establishes link between nanoscopic and macroscopic universe by inventing adequate methods
and enables to arrange atoms as we desire and
subsequently to achieve effective, complete control
of the structure of matter2,3.
Metals were used in powder form used as medicine in Ayurveda (600-10000 BC). They were converted
into very fine and absorbable powders which were
therapeutically most effective and least toxic4, 5.
In Modern Era the vision of Nanotechnology was
born by Richard P Feynman (1959) who predicted
the potential of nanoparticles in his historic lecture
‘there is plenty of room at the bottom’. Norio Taniguchi in 1974 defined Nanotechnology as process
of separation, consolidation and deformation of
material by one atom or one molecule. In 1981 Gerd
Binnig and Heinrich Rohrer introduced scanning
tunneling microscope which could image nonconducting organic molecules6
. Nanotechnology
enables analysis of structures at Nanoscale and
understand the physical structures at nano level
dimension. Nanotechnology helps in manufacture
Nano level structures and to develop devices with
Nanoprecision.
There are mainly three approaches in nanotechnology.7,8 Bottom-up approach is to arrange smaller
molecules into complex assemblies using chemical
or physical forces operating at the nanoscale to
assemble basic units into large structures. Top-Down Approach is to create smaller equipment/
materials by using larger ones to direct their assembly. The most common top-down approach
involves lithographic patterning techniques using
short wavelength optical sources. In functional
approach, components of a desired functionality
are developed without regard to how they might
be assembled.
Nanomaterials can be one dimensional, two dimensional or three dimensional. One dimensional nanomaterial has only one parameter,
either length, or breadth, or height (E.g - Sheets
or thin coatings).Two dimensional material has
its length and breadth (E.g - Nano wires & nano
tubes). 3D material has all parameters; length,
breadth and height (E.g – Nanoring).
Prosthodontics is the dental specialty pertaining to
the diagnosis, treatment planning, rehabilitation,
and maintenance of the oral function, comfort,
appearance, and health of patients with clinical
conditions associated with missing or deficient
teeth and/or maxillofacial tissues by using biocompatible substitutes, fixed prosthodontics, implant prosthodontics, maxillofacial prosthetics,
removable prosthodontics.9
Materials reduced to
the nanoscale can suddenly show a very different
properties enabling unique applications: opaque
substances can become transparent(Copper), inert
materials may become catalyst(Platinum), stable
materials become combustible(Aluminium), solids
turns into liquid at room temperature(Gold) and
insulators can become conductors(Silicone).
Acrylic resin: The main component of PMMA is
polymethyl methacrylate, also containing small
amounts of ethylene glycol dimethacrylate. It
shows poor strength particularly under fatigue
failure inside the mouth and has low abrasion
resistance. Microbial adhesion onto PMMA is
high. Much attention has been given towards
the incorporation of inorganic nanoparticles into
Polymethyl methacrylate to improve its physical
properties. Various nanoparticles such as ZrO2,
TiO2, and CNT have been used to improve the
performance of PMMA and the results showed that
desired mechanical property enhancement can
be achieved. TiO2 nanoparticle can reinforce the
mechanical behavior of PMMA. Dispersion nano
ZrO2 particles can improve the elastic modulus
and maintain or even improve ductility. Ag, TiO2
and Fe2O3 particles significantly reduce adherence of C.Albicans to PMMA. Addition of modified
ZrO2 nanomaterials in different percentages (2
wt%, 3 wt%, and 5 wt%) to heat-cure acrylic resin
materials results in increased abrasive wear resistance, tensile and fatigue strength with 3 wt% and 5 wt% addition of nanofillers10.
Denture teeth: Wear resistance is the most desired
physical property of denture teeth. Porcelain teeth
are more wear resistant but they are brittle, bond
mechanically to the denture base and difficult to
polish. Acrylic resin denture teeth are easier to
manipulate but undergo excessive wear. Nanocomposite denture tooth comprises of polymethylmethacrylate and uniformly dispersed nano sized
filler particles11. They are highly polishable, stain
and impact resistant material. They offer lively
surface structure and superior surface hardness
and wear resistance (Veracia by Shofu, Japan).
Tissue conditioners: Tissue conditioners have
been commonly used to enhance the recovery of
denture bearing tissues from trauma, damage
or residual ridge resorption usually caused by
ill-fitting dentures. Silver nanoparticles, which
has antimicrobial properties, are added in tissue
conditioners. Modified tissue conditioner combined
with silver nanoparticles displayed antimicrobial
properties against S. Aureus, S. Mutans at 0.1%
and C. Albicans at 0.5% after a 24 hrs and 72 hrs
of incubation period12.
Dental Adhesive: Polymerizable silane is added
to dental adhesives in order to increase the cohesive strength. Since the adhesive liquid are not
that much viscous, the filler particles tend to settle
during storage that leads to inconsistency during their performance. To overcome this discrete
silane treated nanoparticles of silica or zirconia,
size ranges of 5-7 nm are added to it. According
to a study by N. Silikaset al., no decrease in bond
strength of dental adhesives after the incorporation
of silica or zirconia nanoparticles was obtained13.
Maxillofacial Silicone: Maxillofacial prostheses
are made of artificial substitutes like silicone and
used to replace facial parts lost through disease or trauma. They are also used to restore and maintain
the health of the tissues and to improve aesthetics
for better social acceptance of facial injuries. Current materials used for maxillofacial applications
experience some problems like low tear strength
and unacceptable color stability. Thus, it is necessary to have a material with satisfactory tear
strength, tensile properties, appropriate hardness
and color stability. The properties of ideal material
should be similar to missing facial tissue to match
optimally to patient’s articulate features of mastication, speech resonance, and facial gesture. Consequently, there is a need for improved materials
with superior physical and mechanical properties
which are comparable to those of human tissues
and skin. SiO2 nanoparticles are characterized
by their small size, large interface area, active
function, and strong interfacial interaction with
the organic polymer. Therefore, they can improve
the physical, mechanical, and optical properties
of the organic polymer and provide resistance to
environmental stress-caused cracking and aging14.
Nanocomposite resins15,16: Nano fill composites
are the dental composites in which the fillers are
of 1-100 nm range. Most common materials are
nanomeric particles which are essentially monodispersed non-aggregated and non-agglomerated
particles of silica. Optical properties of such materials are good with improved dispersion rate. Polish
retention and surface gloss are more. Handling
and rheological properties are poor. The 2nd type
of nanoparticle used for nanofill composite is nanoclusters. This is done in order to overcome the
disadvantages of the previously used nanomeric
nanoparticle. In nanohybrid Composites, repolymerized organic fillers are incorporated so as to
improve the undesirable rheological properties of
composites. Titanium Di-Oxide Reinforced Resin
Based Composites have been used to improve
the microhardness and flexural strength of the resin-based composites. Inclusion of alumina
nanoparticles in nanocomposite increases the
hardness of the nanocomposite as compared to
other nanocomposites. Calcium phosphate and
calcium fluoride nanoparticles-based composites
release calcium fluoride or phosphate ions and
are shown to provide remineralization to tooth
structure. Nano-hydroxyapatites having a particle
size of 20 nm, were synthesized to mimic human
enamel and were found to provide anticaries effect.
Nano Impression Materials17: Vinyl polysiloxanes
are currently the most popular materials these
days. These materials are highly hydrophobic.
Physical properties can be improved by the addition of nano sized fumed silica. Better flow,
improved hydrophilic properties, fewer voids at
margin and enhanced detail precision are the advantages. Nanotech Elite HD+ from the company
Zhermack is manufactured with nanotechnology
application. Here nanofillers are integrated in
the vinyl polysiloxanes, producing a unique addition siloxane impression material having added
advantages of better flow and enhanced surface
detail reproduction.
Nanoceramics18: Ceramics have been used in
manufacture of dental prosthesis because of their
high strength, suitable color, and low thermal
and electrical conductivity. Traditional ceramics
are made of clay and other natural occurring
materials, while modern high-tech ceramics use
zirconia, silicon carbide etc. Nanoceramics has
superplasticity and shows good toughness as well
as ductility. The arrangement of atoms in nanoceramics is such that they are very easy to migrate
under forced formation. Superior mechanical
properties such as strength and hardness are
significantly more. The hardness and strength of
nanoceramics is 4 to 5 times higher than those of
the conventional ceramic materials.
Nano Light cure Glass ionomer cement: Glass
ionomers were introduced by Wilson and Kent in
the 1970s as dental filling material. Cellulose fibers, hydroxyapatite and fluoroapatite are added to
improve their properties. Luting agents based on
nanotechnology are being produced for permanent
cementing of conventional prosthesis including all
ceramic constructions. This material displays high
pulpal friendliness and also minimum leakage
at the margin. More recently, addition of nanoparticles resulted in the aesthetic improvement
of the final restoration and polishablilty. Fluoride
release property is not affected by the addition of
nanoparticles.
Dental Implant Surface modifications Nanotopographically19: Dental implant therapy has been
one of the most significant advances in dentistry
in the past three decades. Osseointegration is
widely accepted in implant dentistry as the basis
for implant success. The most frequent cause of
failure of implants is insufficient bone formation
around the implant. Many research efforts have
been directed toward improving the bone-implant
interface, with the aim of accelerating bone healing and improving bone anchorage to the implant
Surface properties of dental implants play an
important role in biological interactions. The nanometer sized roughness and the surface chemistry
have a vital role in the interactions of surfaces with
proteins and cells. With the introduction of nanotechnology, nanostructured hydroxyapatite and
calcium Phosphates coating for dental implants,
have attracted much attention. Hydroxyapatite
and calcium phosphates coatings promotes bone
formation around implant, by increasing osteoblasts function such as adhesion, proliferation
and increases mineralization.
Nanotechnology in COVID-19 Scenario: As of
now as we are moving towards pre-covid times & COVID -19 vaccination is playing a crucial role in
returning life to normal, we can’t neglect the role
of nanotechnology in vaccination development.
The COVID-19 pandemic has infected millions
of people with high prevalence, long incubation
period and lack of treatments or vaccines. As of
now it is proven that vaccines are the most promising solution to mitigate new viral strains. The
genome sequence and protein structure of the
novel coronavirus were made available in record
time, allowing the development of inactivated or
attenuated viral vaccines along with subunit vaccines for prophylaxis. Lipid nanoparticles are a
vital component of the mRNA COVID – 19 vaccines,
playing a key role in protecting and transporting
the mRNA effectively to the right place in cells.
They are next generation liposomes that uses
nanotechnology and are well suited to stable and
efficient delivery of various therapeutics.
Nano technology carries a significant potential
for misuse and abuse, if not properly controlled &
directed. Nanoparticles have large surface area.
The more the surface area, greater the chance
to increase the rate of absorption through skin,
lungs, digestive tract. This could cause unwanted
effects in the body as non-degradable nanoparticles gets accumulated. Decreasing the size of the
particle has been identified as main parameter
for the increased toxicity of different materials20.
Accumulation of nano particles is seen in spleen,
liver and kidney in animals. Nanoparticles are so
small that they can easily cross the blood-brain
barrier. Proper care should be taken regarding
nano particles and nanotechnology. Safety issues for personal health and safety of the workers involved in the nanomanufacturing and also
consumers is a great concern.
Nanotechnology is set to revolutionize clinical
dental practice. The future holds in store an era
of Prosthodontics in which every procedure will be performed using equipment and devices based on
nanotechnology. With a diverse range of applications in all spheres, it has a capacity to change
the world we live in. Oral health care services will
become less stressful for dental professionals,
more acceptable to patients and the outcome will
become significantly more favorable. THE BEST
IS YET TO COME!!