Smart materials

1. PRESENTED BY:
ROSHNI MAURYA
IST YEAR PGT

2.  By definition and general agreement, “Smart
materials ” are materials that have properties
which may be altered in a controlled fashion by
stimuli, such as stress, temperature, moisture, pH,
electric or magnetic fields. A key feature of smart
behaviour includes an ability to return to the
original state after the stimulus has been removed.
 Smart materials are highly responsive and are
often called as “responsive materials”. The recent
advances in the design of smart materials have
created novel opportunities for their applications in
bio-medical fields. One of the applications is the
dental restoratives.

3. Earlier smart material applications started with
magnetostrictive technologies. This involved the
use of nickel as a sonar source during World War I
to find German U-boats by Allied forces.
Depending on changes in some external
conditions, "smart" materials change their
properties (mechanical , electrical, appearance),
their structure or composition, or their functions

4.  strain
 stress,
 temperature,
 chemicals (including pH stimuli),
 electric field,
 magnetic field,
 hydrostatic pressure,
 different types of radiation,
 other forms of stimuli

5. EFFECT CAUSED BY: EFFECT PRODUCED
 absorption of a proton
 a chemical reaction
 integration of a series
of events
 translation or rotation
of segments within the
molecular structure
 Creation and motion
of crystallographic
defects or other
localized
conformations,
 alteration of localized
stress and strain fields
 a color change
 a change in index of
refraction
 a change in the
distribution of stresses
and strains
 a volume change

6.  action of receiving and responding to stimuli
to produce a useful effect must be
reversible.
 asymmetrical nature (primarily critical for
piezoelectric materials)
 inclusion in smart structures i.e. structures
with at least one smart material
incorporated within its structure and
 from the effect of the smart material causes
an action.

7.  Their degree of smartness is measured in
terms of their “responsiveness” to
environmental stimuli and their “agility”.
 Responsiveness implies a large amplitude
change while agility implies a fast response.
 Their classification is based on the
relationship between the stimulus and
response.
A smart structure may have sensors (nerves),
actuators (muscles), and a control (brain). Thus,
the term biomimetic is associated with smart
structures

8. Type 1 Property-changing
INPUT OUTPUT
Thermomochromics Temperature difference Color change
Photochromics Radiation (light) Color change
Mechanochromics Deformation Color change
Chemochromics Chemical concentration Color change
Electrochromics Electrical potential
difference
Color change
Liquid crystals Electrical potential
difference
Color change
Suspended particle change Electrical potential
difference
Color change
Electroheological Electrical potential Stiffness/

9. Type 2 Energy-exchanging
Electroluminescents Electric potential difference Light
Photoluminescents Radiation Light
Chemoluminescents Chemical concentration Light
Thermoluminescents Temperature difference Light
Light – emitting diodes Electrical potential difference Light
Photovoltaics Radiation (light) Electrical
potential
difference

10. Piezoelectric deformation Electric potential
difference
Pyroelectirc Temperature
difference
Electric potential
difference
Thermoelectric Temperature
difference
Electric potential
difference
Electrorestrictive Electric potential
difference
deformation
Magnetorestrictive Magnetic field deformation

11. The Basic Five Components of a
Smart Structure

13. RESTORATIVE DENTISTRY TYPES
A. Passive Smart Restorative Material Glass Ionomer Cement
Resin Modified Glass Ionomer Cement
Compomer
Dental Composite
B. Active Smart Restorative Material Smart Composites
Ariston pHc
ACP Composites
C. Prosthetic Dentistry Smart Ceramics
Smart Impression Material

14. D. ORTHODONTICS Shape memory alloys
E. Preventive Dentistry Fluoride releasing pits and fissures
sealants , ACP releasing pit &fissure
sealants
F. Endodontics Niti Rotary instruments
Cited from Textbook of
Pedodontics by Shobha
Tandon ( 2nd edition)

15. This material was developed by Wilson and Kent in 1971.
 These are adhesive tooth color anticariogenic restorative
material.
 It can be used as a luting cement, a lining under another
restorative material or as a restoration.
 It also known as Poly Alkenoate Cement and Alumino
Silicate Polyacrylic Acid (ASPA)

16. Glass ionomer materials can be said to
be mimicking the behaviour of human
dentine through a type of smart
behaviour. The smart behaviour of glass
ionomers and related materials is
closely linked to their water content
and the way in which this can react to
changes in the environment

17. Critical property for GIC that makes them unique and
desirable : ability to release fluoride from the glass fillers
to adjacent tooth surfaces.
Water- one of the constituents of GIC, part of the acid-base
reaction for setting; plays a critical role in the fluoride release
of GIC.
The aqueous phases of the set GIC exist in the form of
hydrogels that allow a chemical equilibrium with an ion
movement between the GIC and the environment – the oral
cavity and the surrounding tooth structures.
It has been shown that fluoride-releasing materials are
effective in inhibiting demineralization while providing for the
remineralization of adjacent tooth structure. This has
important implications for GIC as restorative and
preventive materials.

18. GIC described as a “smart” restorative material because the fluoride
they contain is not only released to surrounding tooth structure but can
also be recharged in the glass ionomer.
Referred to as the “reservoir effect” : an important feature of GIC.
GIC release fluoride from the unreacted glass fillers over time into the
saliva. From the saliva there is an ion exchange that occurs, with the
fluoride ions diffusing from the GIC (area of high concentration) to the
tooth (lower fluoride concentration).
Over time there is an equilibrium as the fluoride is incorporated into the
hydroxyapatite crystals of the enamel and dentin, over an area of
approximately 1-3 mm surrounding the restoration, forming
hydroxyfluorapatite.
Recharging of GIC with fluoride in unreacted glass ionomer filler : accomplished with
fluoride-containing oral care products, like topical fluoride gel applications , fluoride-
containing toothpastes and mouth rinses. This recharging effect allows GIC to retain
their caries protective abilities.

19.  These are materials which have a small quantity of a resin
into the liquid formula.
 The advantages include early resistance to water uptake in
the nearly set cement as well as enhanced translucency.
 The resin utilized in these materials is Hydroxy Ethyl Meth
Acrylate(HEMA) and its incorporated into the liquid in
about 15-25% so as to have a powder liquid ratio of about
3:1

20. Major development in tooth restoration related
to resin-modified glass-ionomer systems is that
the light-curing resin component of the glass-
ionomer cement chemically combines with resin-
based composite material. Because certain glass-
ionomer cements are the best direct-application
dentin-replacement materials presently
available, and resin-based composites simulate
enamel closely, using the two in combination
makes for biomimetic, or “tissue-specific” tooth
repair. This concept has been called “layering,”
“the sandwich technique,” or “stratification.”

21.  Consist of a paste containing Ca, Al, F silicate glass
filler in dimethacrylate monomers with acrylic acid
like molecules;
 Are set by polymerization of C=C of methacrylate
(delayed acid/base reaction between glass and acid
molecules);
 Promote adhesion to teeth, mediated by the adhesive.
 Offer good strength, biocompatible, low solubility
 Have higher wear than composite, lower F release than
conventional glass- ionomers and packable composites.

22.  Ceramic braces are translucent in appearance so they blend
in with natural tooth colour. So ceramic braces won’t make
the smile look “metallic”.
.
ceramic braces may cause wear to the teeth as they are harder
than the teeth enamel ,have the potential to cause a wear or
even a severe wear on those teeth that touch against them.
Thus the orthodontist should decide that on which all teeth
that the braces can be placed.
Mostly placed on the upper teeth especially on the centre six
upper front teeth so that wear is less, are not placed on the
patient’s lower teeth for the fear of creating excessive wear.
Smart brackets braces are containing microchip capable of
measuring the forces applied to the bracket/tooth line, this
could significantly reduce the treatment times and to set the
non-harmful applied forces.

23.  In 1995 at ETH Zurich the first “all ceramic teeth and
bridge” was invented based on the process that enables the
direct machining of ceramic teeth and bridges. Then these
materials were introduced and tested in the market as
CERCON – smart ceramics..
The Zircon based ceramic material is created from one unit
with no metal and it is not baked in layers of metals.
Product is metal free, biocompatible with more strength that
helps to resist crack formation.
 Cercon Smart Ceramics deliver excellent aesthetics without
reservations or compromise whether it is a “front” or “back”
teeth, single or multi unit bridges.

24.  A highly stable ceramic oxide which is used in
the industrial applications requiring high
strength and stability is Zirconium oxide
(ZrO2). It has a history as a bio material from
1970’s.
 . Cercon system has properties namely
strength, toughness, reliability and
biocompatibility of zirconium oxide. As
Cercon ceramics are bioresponsive they are
said to be smart materials.

25.  Porcelain veneer restoration
 Full cast or porcelain fused to metal crown
restoration.

26.  Aquasil Ultra Smart Wetting® Impression
Material is an addition silicone impression
material
 This new formula of Aquasil is designed with a
reduced contact angle, an increase in tear
strength, and maintenance of a low viscosity
during the working time.
The material is available as a regular- and fast-
set rigid (light green), heavy (light green),
monophase (maroon), low (teal), and extra-low
(orange) viscosities
.

27. It is available in 50-ml cartridges, and the putty
viscosity is available in the original Aquasil
formulation.

28.  SMAS have a wide use in the field of dentistry
because of 1)exceptional super elasticity, 2)good shape
memory 3)resistance to wear 4) good biocompatibility
.
The shape memory effect was first observed in copper-
zinc and copper-tin alloys by Greninger and
Mooradian in the year 1938. But it was only in early
1960 that Buehler and his collageaue discovered and
patented Nitinol ( Nickel Titanium Naval Ordnance
Laboratory ), a nickel titanium alloy created in Naval
Ordnance Laboratory. These shape memory materials
are in radiology, cardiovascular and other medical
applications as endovascular stents and tissue
connectors.

29. The most commercially important use of SMAs is
the orthodontic applications. The arch wires used as
a corrective measure of misaligned teeth for many
years were made of stainless steel. Due to limited
flexibility and tensile character, they created a great
discomfort during the usage.
Re-tensioning of these wires for every three or four
weeks was necessary for which the patient had to visit
the orthodontist very often.

30.  Super elastic wires are used nowadays for these
corrective measures owing to their flexibility and
resistance.SMA applies gentle , continuous forces,
which are in physiological ranges, over a longer
period. Thus the visits to the orthodontist are reduced
significantly.
The movement of these arch wires is only 6mm for 6
months that causes only a minimal discomfort.
 The superior flexibility, durability, torqueability when
compared to stainless steel is the fundamental
advantage of these materials, thus producing greater
ease to use and increased patient comfort.

31.  Smart devices are also being used for healing
broken bones. Such smart ‘healing’ are reasons
why SMAS are borne in mind for many
application in medical, dentistry , other fields
in future.
 SMA employed in various DISTRACTION
OSTEOGENESIS appliances which do not
require adjustment over a long period of time,
hence dependence on patient compliance is
greatly eliminated.

32. . The Ni-Ti alloy braces were introduced in 1972 that
reduced the length of the orthodontic treatment and
reduction of check-ups. The introduction of SMA
braces gave good results due to their corrective
forces
. The adjustment of any teeth arrangement is due to
the remodeling of the bone by the forces exerted by
the braces that are used. This force should be
minimal and should be of a very narrow range so
that it will lead to proper correction of dental
malformations.

33. ADVANTAGES
Ni-Ti alloys have a unique combination of properties of
i) shape memory,
ii) super elasticity,
iii) great workability in martensitic state and
iv) resistance to fatigue and corrosion.
The Ni-Ti braces are more comfortable for the
patients during installation and also during
treatment. Consumption of a very hot or very cold
food does not lead to any complications in case of
these braces if the austenite and martensite phases are
well chosen.

34.  Smart composites containing ACP (Amorphous
Calcium Phosphate) are very much useful in bio
smart dentistry. Among the most biologically
important calcium phosphate, ACP is the most
soluble one. It also exhibits the property of being
rapidly converted into hydroxyapatite (HAP).
 When ACP is introduced into specially designed and
formulated resin, to make a composite material it
will have an extended time release nature to act as
a source for calcium and phosphate useful in
preventing caries.

35.  Is a vital antecedent in biological formation of
hydroxyapatite.
 Has two properties : preventive ; restorative, justifying
its use in dental cements, adhesives, pit and fissure
sealant, composite.
 Remains in its original form at neutral or high pH.
When low pH values (at or below 5.8) occur in the oral
environment it converts into HAP and precipitates
thus replacing the HAP lost to the acid
 . One clinical trial demonstrated a significant decrease
in root caries among 44 high-risk head and neck
radiation patients with the use of a dual phase ACP
dentifrice containing 1,100 ppm sodium fluoride in
comparison to a toothpaste containing 1,100 ppm
sodium fluoride only.

37. Are referred as “smart material” becoz
 Releases Ca and Phosphate ions only when the
surrounding pH drops at or below 5.8
 Once CaPO4 is released , it will act to neutralize the
acid , buffer the pH.
 ACP acts as a reinforcement of tooth’s natural
defense system only when it is needed
 Has a long life . It does not wash out.
 Is non- reliant on patient compliance
Meyers and Eanes showed that the solubility of ACP enables it
to release supersaturating levels of calcium and phosphate ions
in proportion that is favorable for hydroxyapatite formation. (A
thermodynamic analysis of the amorphous to crystalline
calcium phosphate transformation. Calcif Tissue Res.
1978;25(1):59-68. )

38.  Ivoclar – Vivadent (Liechtenstein) introduced Ariston pHc in 1998
as a new composite material of white colour, indicated for posterior
restorations and providing active caries protection.
 It is a light-cured filling material indicated for posterior restoration.
Its monomer matrix consists of a mixture of dimethylmetacrylates
and inorganic fillers include alkaline glass, Ba-Al fluorosilicate
glass, ytterbium trifluoride and highly dispersed silicon dioxide.
 It also contains a catalyst and stabilisers. Its colour is white so for
aesthetic reasons, it is more acceptable than amalgam.
It is an “ intelligent” restorative material ,releasing three different
types of ions (fluoride, calcium, hydroxyl). The release of these ions
depends on the pH value. When the pH value in the oral cavity is
low ( drop below critical 5.5 level)due to active plaque, Ariston
releases a significantly higher amounts of ions than it does with
neutral pH values.

40. The ion effects are as follows:
 fluoride ions hamper demineralization,
promote remineralisation and inhibit
bacterial growth
 calcium ions hamper demineralization
and promote remineralisation
 hydroxyl ions neutralize the acid
produced by cariogenic bacteria and
inhibit bacterial growth .
 The physical properties of Ariston are
comparable to those of fine-particle
composites.

41.  Ariston pHc is a promising material for posterior
restorations. (SCRIPTA MEDICA (BRNO) – 76 (1):
39–48, January 2003)
 especially for the restoration of primary and young
permanent teeth;
 this material does not require the acid-etching
technique and thus the danger of dental pulp
irritation by phosphoric acid is avoided.
 The application of Ariston pHc is not time
consuming and this may be important in treatment
of less cooperative children.
 Ariston pHc can also be used for preventive filling
restorations.
The fluoride release from this material is claimed by
the manufacturer to be lower than conventional
glass ionomers but more than that of compomers.

42.  Combining the benefits of fluoride release from glass
ionomer cements and good retention and seal from
resins, pit and fissure sealants with fluoride have been
developed.
TWO methods of fluoride application has been used :
 Soluble fluoride is added to unpolymerised resin-
after a sealant is applied to a tooth, the salt dissolves
and fluoride ions are released . Ex –Helioseal –F
 Other method involves an organic fluoride
component which is chemically bound to the resin,
enhancing fluoride release while maintaining the
physical properties of resin material. Ex –methcrylol
fluoride methyl methacrylate (Teethmate F -1) ; acrylic
amine hydrogen fluoride salt.

43. Godoy et al. measured the amount of fluoride released by various
fluoridated sealants. Results showed that Teethmate F-1 released
significantly more fluoride in comparison to Helioseal-F. In a similar study
conducted by Loyola-Rodriguez and Garcia-Godoy, Teethmate F-1 ] was the
only material that showed antibacterial activity against several strains of
Streptococcus mutans and Streptococcus sobrinus .

44.  Tooth enamel begins to demineralize in the presence of
bacteria-produced acid once the oral cavity's pH level drops
below 5.5 and demineralization eliminates the calcium and
phosphate ions that compose enamel's hydroxyapatite.
 In the remineralization process, calcium and phosphate ions
are redeposited into the tooth mineral. Fluoride contributes
to the remineralization process in several ways.
 It accumulates on the surface of the enamel crystal, which
cre- ates a physical barrier that makes the tooth more acid
resistant.
 The negatively charged fluoride ion attracts the positively
charged calcium during this repair process, ultimately
changing carbonated apatite to a fluorapatite - like form that
is larger and stronger than the original hydroxyapatite.
 Fluoride may also provide antimicrobial effects through the
inhibition of bacterial intracellular enzymes. Although
fluoride serves as a catalyst for remineralization,
remineralization will not occur unless adequate amounts of
calcium and phosphate ions are available.

45.  *Aegis® products contain the “smart material” Amorphous
Calcium Phosphate (ACP). ACP slowly releases calcium and
phosphate ions, the basic building blocks of teeth.
 In scientific testing ACP has demonstrated the ability to
remineralize tooth structure by enhancing the tooth’s natural
repair mechanism.
 ACP is referred to as a “smart material” because it only releases
calcium and phosphate ions when the pH drops to 5.8. Once the
calcium phosphate is released, it will act to neutralize the acid and
buffer the pH.
 ACP acts as a reinforcement to the tooth’s natural defense system
only when it’s needed. A simple swish of water will bring the pH
back to a neutral 7.4.

46. Technical Tips
A diet with reduced acidic beverages such as juice and soda
may extend the life of the ACP

48.  The first investigation of nickel titanium in
endodontics was reported in 1988 by Walia,
Brantley, and Gerstein.
 Introduction of these rotary inst. has made
endodontics easier , faster than hand
instrumentation.
 Results in consistent , predictable root canal
shaping
 Technique is less fatiguing for practitioner
 Decreases postoperative pain for patient

49.  Laser radiation of high- fluency can be easily delivered by
Hollow-core photonic-fibers (PCFs) i.e., the laser radiations
can easily be snaked through the body using this hollow-core
photonic-fibers which are capable of ablating tooth enamel
.Through a hollow-core photonic –fiber, sequences of
picoseconds pulses of Nd : YAG laser radiation with a core
diameter of approximately 14µm is transmitted and these
pulses are focused on the tooth surface to ablate dental tissue.
.
The same fiber is also used in transmitting emission
from plasmas that are produced by laser pulses on the
tooth surface in the backward direction for detection
and optical diagnostics. While using these fibers we
ought to be very careful because there is a risk factor
that in some cases the fiber walls fail and the laser
light may escape and harm the healthy tissue.

50.  Science and technology in the 21st century relies
heavily on the development of new materials that
are expected to respond to the environmental
changes and manifest their own functions according
to the optimum conditions. Smart materials are an
answer to this requirement of environment friendly
and responsive materials which alter their
properties to perform specific functions. Due to a
rapid progress in this area of science, smart
materials hold a good promise for the future and in
field of BIO SMART. DENTISTRY.. Dental
practitioners should aware of these innovative
materials to enable their use and utilize their
optimal properties in day to day practice to provide
quality and effective solution to dental problems.