NAME: SOUMYADEEP JANA
FINAL PROF. B.D.S. EXAMINATION
REGISTRATION NO- 2512 OF 2010-2011
Topic under the Project:
Introduction- Normal Tooth Colour
Discolouration of Tooth & Causes
Types of Tooth Discolouration
Different Treatments of Tooth Discolouration
Introduction Of Bleaching
Indication & Contraindication of Bleaching
Brief History of Bleaching
Ideal Properties Bleaching Materials
Different Bleaching Agents
Legal Values & Ethical Consideration Of Bleaching
Classification of Bleaching Procedure
Vital Tooth Bleaching- Steps, Technique, Complication
Non-vital Tooth Bleaching- Steps, Technique, Complication
Human teeth are polychromatic in nature. Normal colour of
primary teeth is bluish white. The colour of permanent teeth is grayish-
yellow, grayish-white, yellowish-white. The colour of teeth is
determined by the translucency and thickness of the underlying dentin,
and the colour of the pulp. Tooth colour also varies in different clinical
position (incisal/occlusal 3rd
, middle 3rd
), from one group of
teeth to the next, and from person to person.
Factors Modifying Tooth Colour :
a) Colour of enamel covering the crown.
b) Translucency of enamel.
c) Thickness of the enamel at different level.
d) Age of the tooth.
e) Parafunctional habit of the patient.
Classification of Tooth Discolouration :
Tooth discolouration varies with etiology, appearance, localization, severity
and adherence to the tooth structure. It can be broadly classified as,
1)Extrinsic discolouration 2)Intrinsic discolouration 3)Combination of both
The stains deposited on the tooth surface are a result of attractive forces
which are long range interactions such as van der Walls and electrostatic forces
and short range interactions such as hydratin forces, hydrophobic interactions,
and hydrogen bonds.
Due to amalgam restoration Due to tobacco smoking
: causes & colours
Extrinsic Factors Characteristics
Chromogenic bacteria stains Green, black-brown & orange
Tobacco Black, brown
Amalgam Black, grey
Medicaments Silver-nitrate : Grey black
Stannous-fluoride : Black brown
Chlorhexidine : Black brown
Food & Beverages Coffee, tea, wine etc.; colour of
Iron Black cervical discolouration
Classification Based on Chemistry of Staining put forth
by Nathoo  :
a) N1 Type or Direct Dental Stain: The coloured materials
(chromogens) bind to the tooth surface & cause
discolouration. The colour of the dental stain is same as the
colour of the chromogens.
b) N2 Type or Direct Dental Stain: The chromogens change colour
after binding to the tooth.
This is actually N1 type of food stain darkens with time.
c) N3 type or Indirect Dental Stain: Colourless materials or a
prechromogen binds to the tooth & undergoes chemical reaction
to cause a stain.
Aetiology of Intrinsic Tooth Discolouration-
Within Enamel :
Local – caries, idiopathic, injury/infection of primary
Pre-decessor, internal resorption.
Systemic – amelogenesis imperfecta, drugs e.g.
Tetracycline, fluorosis, idiopathic, systemic
illness during tooth formation.
Within Dentin :
Local – caries, internal resorption, metallic restorative
material, necrotic Pulp tissue, root canal filling
Systemic – bilirubin (haemolytic disease of a newborn),
Congenital porphyria, dentinogenesis
imperfect, drugs e.g. Tetracycline.
(causes & colours)
Intrinsic Factor Colours
Yellow or grey-brown
Dental Fluorosis Opaque white yellow- brown patch
Sulphur Drugs Black staining
Tetracycline Grey-brown to yellow-brown
Hyperbilirubinemia Yellow-green to blue brown & grey
Red or brown
Indication Advantages Disadvantages
No Treatment Patient with poor
Non invasive, no
Will not address
May achieve a
Ideal Properties of A Bleaching Material :
It should have neutral pH.
It should be easy to apply, maximum patient compliance.
It should not irritate or dehydrate oral tissue.
It should not cause any harm to the tooth being bleached.
It should adhere to the tooth structure i.e., controllable flow.
It should have contrasting colour with the oral structure.
It should have adjustable peroxide concentration.
It should give desired result within short time.
Be well controlled by the dentist to customize to the
YEAR AUTHOR INNOVATION
1799 Macintosh Chloride of Lime is invented- called
1884 Harian 1st
used Hydrogen Peroxide.
1958 Pearson Used 35%HP inside tooth & suggested
25% HP with heated lamp.
1961 Spasser Perborate sealed within tooth –
1965 Stewart Thermocatalytic Technique- pellet
saturated with superoxyl & heated
with an instrument inside pulp
1987 Feinmann In office bleaching using 30% H2O2 &
heat from bleaching light.
1989 Croll Micro abrasion Technique
1989 Haywood &
10% CP used in trays overnight –
‘Night-guard Vital Bleaching’
1996 Rayto Laser Tooth Whitening
1997 Settembrini et al. Inside-Outside bleaching technique.
1998 Carillo et al. Open pulp chamber with CP inside.
1990 Numerous authors Bleaching materials were investigated
& the FDA called for safety studies.
1991 Numerous authors Power Bleaching using 30% HP & light
Bleaching Agents :
Sodium Dioxide -
Historical Interest – limited use.
When sodium dioxide combines with water, the reaction yields
sodium hydroxide & oxygen.
Na2O2 +H2O = 2NaOH +1/2H2O
The molecular oxygen produced is a powerful antiseptic &
When used in high concentrations on pulp less teeth, it has a
strong caustic effects that render it dangerous for the
Chloride & Chloride Derivative -
Chlorine acts indirectly as it is capable of releasing the oxygen
from a water molecule.
Cl2 + H2o = 2HCl + 1/2O2
Hydrogen Peroxide -
It is the main bleaching agent used for tooth whitening,
produced by the following reaction.
H2O +1/2O2 =H2O
The resulting molecule is unstable & ready to split & release a
molecule of oxygen.
The concentration of H2O2 solutions are usually given in
percentage or in volumes that indicate the quantity of oxygen
released as a result of the breakdown reaction.
Because molecular dissociation occurs differently depending on
the pH, the efficacy of H2O2 can be improved by modifying the
pH of the solution.
In an alkaline solution, the hydroxyl groups neutralises the
protons & accelerate the bleaching process.
The consumption of an element produced by the oxidation-
reduction reaction will modify the balance, leading to the
yielding of highly reactive OH2-, a molecule with a low
molecular weight, far more oxidative than molecular oxygen.
And which diffuses easily through the enamel barrier.
Sodium Perborate (BO3Na4H2O) -
It’s a fine white powder, which is antiseptic & chemically
stable when anhydrous.
When combined with water, it reacts to produce metaborate
& molecular oxygen.
Na2[B2(O2)2(OH)4] +2H2O =2NaBO3 = 2H2O
BO3Na + H2O =1/2O2 +H2O
Metal peroxides, persulphates, calcium perborate &
magnesium perborate (acting as anion breakdown
activators) may also yield molecular oxygen, & are used by
some in preference to sodium perborate.
The final product is an oxidizing molecule produced by the
breakdown of the hydrogen peroxide.
Carbamide Peroxide -
It is also known as Urea-Hydrogen Peroxide.
Approved by FDA as an oral antiseptic in 1979 & as a
medicament in 1991.
It is most widely used vital tooth bleaching product.
Obtained by the syncrystallisation of H2O2 & urea into
colourless & odourless crystals.
Its chemical formula contains about 30% hydrogen peroxide.
In other words, a 10% carbamide peroxide solution breaks
down into 3% H2O2.
H2N-CO-NH2*H2O2 =H2NCONH2 = H2O2
Carbamide peroxide yields urea that further decomposes into
CO2 & ammonia.
A high pH facilitates the bleaching process , i.e., in alkaline
solution , the formation of free radicals requires less energy,
& the reaction yield is higher, with larger quantities of H2O2
being produced than in an acidic solution.
Improve the efficacy of tooth bleaching products.
Not always clearly mentioned by the
Thickeners such as carbopol (acrylic acid polymer
resin) which helps to maintain contact between the
gel & dental tissue as long as possible & thus allows
a progressive release of the oxidising agents.
Urea, which stabilises the hydrogen peroxide,
increases solution pH, & has an anti-cariogenic
Glycerine, which increases the viscosity of the
preparation & facilitates its manipulation. The only
problem is the tooth dehydration it incures.
Stabilisers (e.g., Citroxain, citric acid, phosphoric
acid), which increase the shelf life of bleaching
Flavouring agents, which make the product
pleasanter to use.
Different Commercially Available Bleaching Agents :
General Mode of Action of Bleaching Agent :
Mode of action-1
Factors Affecting Bleaching :
Surface cleanliness: Clean enamel surface is important to distinguish
between intrinsic & extrinsic stains. Moreover the debris on the surface
minimizes the contact of the bleaching agent with the tooth surface.
Concentration of peroxide: The effect of the bleaching is increased
with the increased concentration of peroxide. In office bleaching
employs 35% hydrogen peroxide which is more caustic in nature. The
usual concentration of at home bleaching is 10% carbamide peroxide,
which is relatively safe in contact with the soft tissue.
Shelf life: Carbamide per oxide is more stable than hydrogen peroxide
& has a shelf life of 1-2 years, while hydrogen peroxide has a shelf life
of few weeks.
Temperature: This is of important during in office bleaching. Increase
in temperature accelerates the release of oxygen free radicals. The
reaction gets doubled with an increase of 10 degree centigrade.
However increase in temperature to an uncomfortable level causes
tooth sensitivity & irreversible pulpal damage. Local anaesthesia should
not be administered during bleaching.
PH: Hydrogen peroxide is active in alkaline pH. The optimum pH for
hydrogen peroxide ranges from 9.5 to 10.8.
Time: Concentration of the bleaching agent & the time of contact with
the tooth are the most important factors in effective bleaching.
Increased contact time increases the bleaching efficacy. However,
prolonged contact results in tooth sensitivity.
Sealed environment: This is of relevance in non-vital tooth
bleaching. Hydrogen peroxide sealed in the access cavity maintains the
required concentration for active bleaching.
Additives: In order to increase the viscosity of the bleaching materials,
additives like glycerine, glycol & tooth paste like materials are added.
These agents may reduce the efficacy of the bleaching materials.
Other factors: like age of the patient, initial colour of the tooth &
gender may also play a vital role in bleaching process.
Vital Tooth Bleaching
Moderate tooth discolouration –healthy tooth with perfectly sealed
coronal fillings (perfectly composite resin fillings), & teeth with no
significant structural defect.
Discolouration related genetic disorders.
Permanent acquired discolouration – fluorosis staining, with stains
ranging from simple, white, opaque spots to a darker discoloration, or
other type of staining caused by excessive intake of fluoride.
Discolouration related to the physiological ageing of teeth.
Post-traumatic discolouration (vital tooth with sclerotic dentin).
Improvement of the teeth’s natural colour before the placement of a
prosthetic restoration in the adjacent area.
Very pronounced tooth stains with dull & saturated coloration, where
colour bands are visible, and treatment in this case 9is a prosthetic
alternative, i.e.; the application on the affected teeth of a thin layer of
covering material (veneer).
Tooth bleaching will be used here primarily to lighten the underlying
tooth colour, thus limiting tissue destruction & improving the overall
appearance of the restorations.
Teeth with extensive crown filling.
Presence of cervical lesions due to wear, &dentin “islands” caused by
Stains mainly due to permeation by metal salts (amalgam).
Relative contraindications specific to the night –guard technique ;
Advanced periodontal disease
Multiple & extensive amalgam restoration or temporary fillings.
Young patient aged under 15-16(immature tissues & large pulp volume)
Teeth that shows initial hypersensitivity during the presurgical clinical
Teeth with non leak-proof filling, &initial or recurring caries. It is an
absolute prerequisite to any bleaching treatment that carious lesions be
fully treated & that all restorations fit perfectly.
Smoking (possible interactions with peroxides)
Vital Tooth Bleaching Technique
At Home Bleaching
It is the more commonly used technique because it is easy to perform & is
usually less expensive for the patient. It uses a custom fit tray with 10%
carbamide peroxide. Carbamide peroxide is more stable than hydrogen
peroxide & can be active up to several hours.
Severe enamel loss
Mild yellow discolouration Hypersensitive tooth
Brown fluorosis discolouration Bruxism
Age related discolouration Presence of caries & Defective coronal
Dental & Medical History
Radiographs of Tooth to Be Treated
Impression of the dental arches for the construction of
Recall visit to assess the progress & compliance
Alginate impressions of the arches are made.
Plaster casts are poured.
Reservoirs are made that deliver the bleaching agent, at a
distance of 1 mm from the gingiva. The light-cured resin
spacers should be 0.5 mm to 2 mm thick, depending on the
technique that will be used & above all, on the concentration
of the product & the intensity of the stain.
Thermo forming a polyvinyl sheet over these models.
Trimming the tray along the gingival line using scissors once
the tray has cooled down- or better still, directly on the
model using a scalpel with an 11 mm blade.
Smoothing the edges with a micro torch.
Cleaning & cold sterilisation of the mouth guard before
Fitting of the Mouthguard & Choice of Bleaching Product:
The mouth guard should fit the patient’s mouth perfectly.
The tray should be in close contact only with the hard
tissues; as this prevents leakage of the bleaching product in
the area of the gingiva, & encourages an in-depth action of
lower-concentration bleaching agents.
The mouth guard should have a constricting effect in the
critical area of the neck of the tooth.
The operator should choose the bleaching product & its
concentration according to the case, & determine the length
of time during which the mouthguard should be worn
The active compound is carbamide peroxide, which breaks
down into urea & H2O2. It usually comes as a gel in a syringe,
with concentration ranging from 10% to 35%. It may be
combined with thickeners (such as Carbapol) that slow down
the degradation process of the Carbamide Peroxide, & with
sodium fluoride that prevents dental sensitivity.
1. Discoloured Teeth 2. Alginate impression Taken
3. Preparation of a Bleaching Tray on the Cast 4.Proper Shaping of the Tray
5. Prepared Bleaching Tray 6. Applying Bleaching Agent on The Tray
7. Applying the Bleaching Agent in the Mouth 8. Bleached Teeth
Instruction to the Patient:
After through tooth brushing, the patient should use the
needle-tipped syringe to fill the reservoirs with moderate
quantities of gel.
Then place the tray inside the mouth & finally rinse off any gel
that may have leaked onto the gingiva.
The dentist will determine the length of time the mouthguard
should be worn according to the product used.
Wearing time will last between three to five hours in one or
two sessions every day, depending on the patient’s availability
& motivation, on dental sensitivity observed during treatment,
& on the results aimed at.
Nightguard systems with concentration ranging from 10% to
16% are highly effective, owing to the fact that the salivary
flow is reduced at night & that the bleaching agent & the
tooth therefore stay in contact much longer.
After removal, the mouthguard should be washed in cold
water & the teeth cleaned thoroughly.
The practitioner should check results every five to six days, in
order to adapt the treatment to change in tooth-shade & to
clinical signs. To facilitate the monitoring of the process both
by the practitioner & by the patient, & for psychological
reasons. It is recommended to bleach 1st
the upper & then the
The outcome depends on -
A) The length of time during which the treatment
mouthguard is worn.
B) The duration of the treatment.
C) Concentration of & sensitivity to the product.
D) On the intensity of the staining.
In case of light staining, teeth are lightened up to 80% in 5-6
In case of severe staining (tetracycline), tooth shade may be
improved to a more or less important extent in the first month
of treatment, particularly in the occlusal third, by increasing
the duration o0f the treatment. In such cases, the at home
treatment may be continued over many weeks, sometimes
even for months.
Used for more severe & patients who are “in a hurry” – Baumgartner
et al. 1983.
Torres-Zaragoza (1984) : 70% H2O2 be used in associated with
a reagent, & a source of heat.
Goldstein (1976), Goldstein & Garber (1995): 35% H2O2
exposed to a beam of light with an adjustable temperature of
45 to 60 degree centigrade.
Baratieri et al. (1995: employed 35% H2O2 activated by the
light of curing lamp.
Dissatisfaction of tooth colour as a result of mild fluorosis, &
In severe discolouration, bleaching could be performed to
lighten the tooth colour before restoration with bonded resin
or porcelain veneers or crowns.
In order to match the existing colour of the crown that is
lighter than the natural teeth.
Superficial stains that can be removed with rubber cap &
Carious tooth structure or dark coloured resin restoration.
Children with large pulp chamber.
Pregnant & lactating woman.
Exposed root surface.
Take a radiograph to detect the presence of caries, defective
restorations, & proximity to pulp horns. Well –sealed small
restorations & minimal amounts of exposed incisal dentin
are not usually a contraindication for bleaching.
Evaluate the tooth colour with a shade guide & take clinical
photographs before & throughout the procedure.
Protect the gingival tissues with Orabase or Vaseline &
isolate the teeth with a rubber dam.
Do not inject a local anaesthetic.
Place protective sunglasses over the patient’s & the
Clean the enamel surface with pumice & water.
Apply 30-35% hydrogen peroxide liquid on the labial surface
of the teeth using a small cotton pellet or a piece of gauze. A
bleaching gel containing hydrogen peroxide may be used
instead of the aqueous solution.
Apply heat with a heating device or a light source. The
temperature should be maintained between 125 & 140
degree F (52-60 degree C).
The treatment time should not exceed 30 minutes even if
the result is not satisfactory. Re move the heat source &
allow the teeth to cool down for at least 5 minutes.
Pumice is used on the teeth to remove residual exposed gel
from enamel surface.
Remove the bleaching agent & irrigate thoroughly.
Dry the teeth & gently polish them with a composite resin
polishing cup. Apply neutral sodium fluoride gel for 3-5
Instruct the patient to use to use a fluoride rinse daily for 2
Any bounded restoration on bleached surfaces must be
postponed by 7-10 days.
Light Sources Used for In-office Bleach:
Conventional Bleaching Light
Uses heat & light to activate bleaching materials.
More heat is generated during bleaching.
Causes tooth dehydration.
Uncomfortable for the patient.
Slower in action.
Tungsten Halogen Curing Light
Uses light & heat to activate bleaching solution.
Application of light 40 to 60 seconds per application per
Xenon Plasma Arc Light
High intensity light, so more heat is liberated during
Application requires 3 seconds per tooth.
Action is thermal & stimulates the catalyst in chemicals.
Greater potential for thermal trauma to pulp &
surrounding soft tissues.
Argon & CO2 Laser
True laser light stimulates the catalyst in chemical so there
is no thermal effect.
Requires 10 seconds per application per tooth.
Diode Laser Light
The laser light produced from a solid state source.
Requires 3 to 5 seconds to activate bleaching agent.
No heat is generated during bleaching.
Less time than overall time needed for home bleaching.
Protection of soft tissue.
More chair time.
Unpredictable & deterioration of colour is quicker.
Dehydration of teeth.
Serious safety consideration.
Not much research to support its use.
Discomfort of rubber dam.
Complications of Vital Tooth Bleaching:
Mercury release from amalgam restoration
Non-vital Tooth Bleaching
Any discolouration secondary to ;
- a loss of pulp vitality, & more particularly to a pulp
haemorrhage or to the decomposition of residual pulp
tissues that were not removed during root canal therapy
- The use of medication, or the placement of root canal filling
materials or non-leak-proof restoration materials.
Blackish coloration of the root, which is visible under a
thin gingiva. The bleaching treatment will have to
reach deep into the root.
Stains incurred by root canal filling pastes (phenolic resins,
radiopacifiers) or metal salts (amalgam), for which treatment
prognosis is guarded.
Teeth with extensive crown restorations.
Permanent teeth in children & young adolescents.
Teeth that have undergone a periodontal treatment & root
Traumatised teeth (luxation, avulsion, intrusion)
Teeth that shows external root resorption.
Non-vital Tooth Bleaching Technique
Rely on the permeability of the dentin, which allows the oxidising agent to
reach the pigments directly, the latter being concentrated mostly at the
dentin-enamel-junction. Prognosis is usually extremely good when case
selection is correct.
Preliminary Steps :
1 ) Thorough clinical examination of the tooth & sarrounding
2 ) X-rays are assess the quality of the endodontic treatment & to
visualise any root &/or periodontal defects.
3 ) Photographs are taken to keep record of the state of the tooth
prior to treatment.
4 ) Conscent- to guarantee the all legal & ethical obligations are met,
the practitioners give the patient a precise quote for the bleaching
treatment, as well all the usual recommendations & any other
Initial Tooth Preperation :
The first phase of the treatment will focus on the protection of the
oral tissues & the preparation of the of the tooth.
The Walking Bleach Technique
Discolouration of the pulp
Dentin discolouration Defective enamel formation
Discolouration not amenable
to extra coronal bleaching
Severe dentin loss
Presence of caries
It uses a paste of sodium perborate & distilled water or hydrogen
peroxide in a 100 to 130 volume solution.
Paste is placed in the pulp chamber & covered with cotton pellet
& sealed with a leak –proof dressing such as Cavit or IRM.
Seal the access cavity to a thickness of 3 mm using an adhesive
material. This ensues a tight seal around the margins & prevents
the leaching of bleaching materials
The paste is left in place for -
3-6 days if the sodium perborate is mixed with H2O2.
Twenty days if it is mixed with distilled water.
Commercially available preparations such as Superoxol (30%
aqueous H2O2 solution) or carbamide peroxide may be used, but
gels tend to spread & to weaken the seal formed by the
The combination of sodium perborate & H2O2 achieves rapid &
excellent results, but the technique is contraindicated as it may
cause external cervical resorption.
The mixture of sodium perborate & distilled water is safe & risk-
free, but less rapid, & results are generally satisfactory, although
the bleaching procedure often needs to be prepared 2 to 3 times
before an acceptable shade is achieved.
The final restoration phase is important when composite materials
are involved, as the quality of the bonding will greatly determine
the longevity of the result.
When products with high concentration of H2O2 are used, the
residual oxygen that remains after the procedure is finished
momentarily inhibits the polymerisation of the composite resin.
The final restoration should therefore be placed 1 week after the
full completion of the bleaching treatment.
It is “Chair-side” or Power” bleaching, uses an activators such as heat,
light or more recently, a laser beam.
-Cotton pellets saturated
with 100 or 130 volume
H2O2 & placed in the
pulp chamber, where
the oxidation reaction is
then activated by heat.
- The tip of the heat-
producing instrument is
placed directly onto the
saturated cotton pellet,
resulting in immediate
shouldn’t touch the
-It applies ultraviolet
light to the labial surface
of the tooth to be
-A 30 to 35% hydrogen
peroxide solution is
placed in the pulp
chamber on a cotton
pellet following by a 2
minute exposure to uv
-Supposedly, this causes
oxygen release, like the
-It can activate high
(35%) extremely quick &
thus help to achieve a
satisfactory lightening of
pulp less teeth with
pathological or acquired
stains in just 1 or 2 30
-The erbium: YAG laser
are used for this type of
treatment as its beams
are rapidly absorbed by
dentinal walls, as this
may cause infractions &
-The procedure is
repeated 5-6 times every
-While heat activation
the speed & efficiency of
reaction, it also
increases the risk of
renders this technique
bleaching technique. -Diode lasers that have a
depth are also used,
although less frequently
because of the high
increases in temperature
A 35% H2O2 gel is placed inside the pulp chamber & on the labial &
lingual surfaces of the prepared tooth that is perfectly isolated.
The tooth is then covered with a clear film (e.g. Whitestrip) fastened
to gingival barrier (light cured protection) so that the gel remains
slightly compressed during breakdown & stays in place at each new
irradiation (frequency 30Hz, energy 60MJ, distance I to 1.5 mm,
duration 3 seconds, exposure is repeated 4 to 5 times, with 30
Air jet cools the spot where the beam is focused. The gel should be
renewed 2-3 times during the procedure.
At the end of the session, the gel & gingival barrier are removed.
Catalase or CaOH should be placed inside the pulp chamber & left
there over 8-15 days prior to the placement of the final composite
restorations so as to neutralise the effects of the H2O2.
Complications of Non-vital Tooth Bleaching :
External root resorption.
Chemical burn due to Superoxol.
Inhibition of Resin polymerisation.
A discoloured tooth is always a point of discomfort for the
patient and related with psychological and social concerns.
Bleaching might be a very easy solution to the patient’s
needs but it itself causes a plethora if adverse effects like
root resorption, enamel damage, tooth sensitivity and
chemical burns occurs. Sadly, often the patient is under too
much of social pressure to pay due to attention to these
adverse effects results. It then becomes the duty of the
dentist to inform the patient of these problems and get an
informed consent before proceeding with the treatment.
We may conclude by mentioning that though bleaching has
its drawbacks, one cannot completely overlook it as an
option for restoring tooth aesthetics. A newer bleaching
agent that is less deleterious to tooth and surrounding oral
tissues might be the answer we are looking for.
Discoloured Under Bleaching Bleached
Grossman’s Endodontic Practice
Text Book of Endodontics- By Amit Garg & Nisha
An Article of Liverpool University
Guided By: Dr. Anuradha Mukherjee
Dr. Soumen Chakraborty