Resins in
orthodontics
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INDIAN DENTAL ACADEMY
Leader in continuing dental education
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Polymerization can be activated by
chemical,light or dual cure
Bis-GMA molecule:
2 reactive C=C grps
cross linking strengt...
Introduction
Dynamically growing science
Discovery of new techniques,materials
Improvement over older ones
Synthetic resin...
By def,non metallic compounds synthetically
produced that can be molded into various forms,used
for various purposes.
Chem...
History
Goodyear(1840) :1st org polymers
rubber & vulcanite
Other polymers
J.W.Hyatt(1869) :cellulose
L. Baekland(1907) :b...
Polymers truly adequate for dental
purpose(1930s)
O.rohn(1936):
Polymethyl methacrylate(plexiglass)
1946:- 98% of denture ...
mid 1950s-direct bonding with epoxy resins
1955- Buonocore demonstrated acid etch
1958-Salder attempt to direct bond witho...
Newman(1965):1st to bond orthodontic attachments
to the teeth by means of epoxy resin,used low mol.
Wt epoxy resin liq wit...
Reynolds(1975):maximum tensile bond strength of
5.9 to 7.9 Mpa adequate,in vitro tensile strength level
of 4.9Mpa clinical...
Other polymers-
Polyurethane,polystyrene,vinyl acrylic
Recently-lass fibers,carbon fibre
graphite,polyaramide fibers added...
Classification of resins
1) natural resins:complex of C,H,O
in paints,perfumes,medicine
dentistry-separating media,cavity ...
Synthetic resins are formed by a chemical
process ,polymerization
in which simple molecules with identical
structure link ...
Synthetic resins
A)thermoplastic:
Softens when heated above the glass transition temp
Tg,at which the molecular motion beg...
B)thermosetting resins:
Undergo chemical change & become permanently
hard when heated above the temp at which they
began t...
Ideal requirements
1. Should be tasteless, odorless, non-
toxic and non-irritant to the oral tissues.
2. Aesthetically sat...
 .
5. Be insoluble and impermeable to oral
fluids.
6. Have a low specific gravity (light in
weight)
7. Tolerate temperatu...
Uses of resins
1. Preparation of dentures
2. Artificial teeth
3. Tooth restoration
4. Cementation of crowns and bridges
5....
Temporary crowns and bridges
Dies
Implants
Endodontic and core filling materials
Athletic mouth protectors
Impression tray...
Terms
Polymer:molecule made of many parts
composed of non metallic elements
bonded by covalent bonds
large molecular size,...
Monomer:
Molecules from which the polymer is
constructed;homopolymer or copolymer
Molecular weight:
Molecular weight of th...
Chain length vs. mol wgt:
Longer the polymer chain—more the no. of
entanglements,more difficult to distort the
polymer
Inc...
Degree of polymerization:
Def as the total no. of mers in the polymer
The higher the mol wt of the polymer made from a
sin...
Polymerization
The process of forming a poly mer from
identifiable subunits,monomers is
polymerization
2 main types:
conde...
Condensation polymerization
Polymerzation acomplished by repeated
elimination of small molecules;byproducts-
water,halogen...
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Addition polymerization
Most of the resins employed in dentistry
Starts from a active centre adding one
monomer mol at a t...
Inorder to be polymerized the monomer must
have a unsaturated grp its structural
formula.on activation of the monomer mol....
copolymerization
Two or more chemically different
monomers,each with some desirable property
can be combined to yeild a po...
Copolymer strc.
Three types:
1.random copolymer:no sequential order btw
two or more mer units
2.block copolymer:mer units ...
Random copolymer:
ABBABABAAABAAABABBBBABAAABABB
BLOCK COPOLYMER
AAAAAABBBBBBBAAAAAABBBBBAAAAA
GRAFT OR BRANCHED COPOLYMER
...
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Polymers strc
1.linear:structural units are connected to one another in
linear sequence
2.nonlinear or branched polymers:
...
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Stages of polymerization
1.induction:
- two processes control induction:
activation & initiation
-for Add. Poly. to begin ...
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Prerequisite for add.Poly.-
presence of unsaturated group(double bond).
when a free radical & its unpaired electron approa...
Benzoyl peroxide is the common initiator mol. Used.
At 50-100c it forms 2 free radicals
Chemical activation:2 reactants mi...
Initiation period is greatly influencved by the
purityof the monomer.impurities react with the
activated groups—increase i...
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Propagation:
less energy needed,5000-8000cal/mol
free radical-monomer complex acts
as a new free radical centre when it
ap...
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Chain transfer:
Active sites is transferred from an
activated radical to an inactive molecule
and a new nucleus for furthe...
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Termination:
Takes place either by direct coupling or
exchange of hydrogen atom from one
growing chain to another
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inhibitors
Inhibition of polymerization:
Impurity that can react with the free
radical will inb. the polymerization
Eg:hyd...
Acrylic resins
Derivatives of ethylene & contain a vinyl
group in their structural formula
2 acrylic resin series :
derive...
Plasticizers
Added to resins to reduce their softening or fusion
temp.
Increase the solubility of the polymer in the monom...
Esters of polyacids are of greater interest in
dentistry
Polymethyl methacrylate is the hardest resin
of the series with t...
Methyl methacrylate:
monomer in liquid form
Clear transparent liquid at room temp
Physical prop:melt. Pt:-48c
Boiling pt-1...
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Degree of polymerization varies with the
conditons:temperature
method of activation
type of initiator conc;
purity of chem...
 Polymethyl methacrylate:
Linear polymer in powder form
Transparent resin,colored or tinted
Transmit light into the uv ra...
Stable resin which will not discolor in uv light and
exhibit remarkable ageing prop
Chemically stable to heat,softens at 1...
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COPOLYMERIZATION
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Composition of acrylic resin(heat cure)
Monomer:pure methyl methacrylate
hydroquinone(.006%)-inhibitor
Polymer:polymethyl ...
Principal Ingredients of Acrylic Resins:
Powder and Liquid
Powder
Liquid
Poly (methyl methacrylate) and other co-
polymers...
Monomer (methyl methacrylate)
Inhibitor (hydroquinone)
Accelerator
Plasticizer (dibutyl phthalate)
Cross-linking agent (gl...
Storage:tumble the powder in the container to restore uniform
distribution of the different particle sizes.
liquid kept in...
Monomer-polymer reaction
4 stages:
Stage1:wet sandy stage:polymer settles down
into monomer & incoherent mass formed
Stage...
Stage3:dough or gel stage
as polymer becomes saturated with the
monomer it gives dough like
consistency,doesn’t stick to j...
Dough forming time:
The time required to reach stage3
Depends on the solubility of the polymer pearls in
monomer
Factors a...
Curing procedure:
Packing:in dough stage acrylic introduced
30-60mt of bench curing- to allow equilibriation of
pressure
P...
INJECTION MOLDING TECHNIQUE
It requires special equipment. The mold space is filled by
injecting the resin under pressure....
Other sources of heat
(1) Steam
(2) Dry air oven
(3) Dry heat (electrical)
(4) Infrared heating
(5) Induction or dielectri...
Chemically cured acrylics
Self curing or auto polymerizing or cold curing
Instead of using heat to activate BPO, a
tertiar...
Heat cure vs cold cure
Degree of polymerization is less than heat
cured,inferior properties
Color stability poorer bcz of ...
Mixing techniques for self cure resins
(a) Salt and pepper method
(b) Knead – on method
(c) Compression molding technique
...
Salt and pepper method (sprinkle on
technique)
After application of separating media the
polymer is uniformly sprinkled ov...
Knead - on Method
The powder and the liquid are mixed and
when dough stage is reached the mix is
molded on to the surface ...
Fluid resin technique (pour-type acrylic
resins)
The chemical composition of this type of resins is
the same as that of po...
The advantages:
better tissue fit
fewer open bites
less fracture of porcelain teeth during deflasking
reduced material cos...
Some acrylic resins instead of the amine
peroxide system utilize the sulfonate or
sulfinic acid system for polymerization....
LIGHT ACTIVATED DENTURE BASE RESINS
Douglas etal
. The first light activated system utilized u.v. light to
initiate free r...
The amine accelerator used is DEAEMA (Diethyl-
amino-ethyl methacrylate) at a concentration
of about 0.15% or less.
It is ...
PHYSICAL PROPERTIES OF ACRYLIC
(a) Strength
The strength of the acrylic resin denture base
materials may fluctuate conside...
The stress properties of the resin are generally
measured by means of a transverse test described by the ADA
sp no. 12 Tra...
The modulus of elasticity, the proportional
limit and tensile strength of heat cure acrylic
resin is about 2350 Mpa, 27 Mp...
The bulkier portion of the denture
may show greater strength than the
thinner portion because of more degree
of polymeriza...
(b) Impact strength
It is a measure of the energy absorbed by a
material when it is broken by sudden blow.
The plasticizin...
(c) Hardness
The knoop hardness no
- for self cure resin is approximately 16-18
-for a resin cured under heat may be as hi...
(e) Abrasion Resistance
This has been evaluated by abrading
specimens against 600 grit silicon carbide
paper for 1 hour un...
(g) Polymerization shrinkage
When methyl methacrylate monomer is polymerized
the density changes from 0.94 gm/cm2 to 1.19
...
The processing shrinkage has been measured
as 0.53% for heat cured acrylic resin as
compared with only 0.26% for a self cu...
(h) Porosity
There are a number of causes of porosity
that can occur during the processing of the
acrylic resin.
If the po...
Internal porosity of the resin occurs as a
result of the vaporization of the monomer or of the
low molecular weight polyme...
Second type of porosity (external porosity)
is due a lack of homogeneity in the dough at
the time of the polymerization.
I...
It is avoided by using
(a) Proper P:L ratio
(b) Favorable mixing procedures
(c) Pack during the dough stage
External poros...
(i) Water absorption
Poly methyl methacrylate absorbs water
slowly over a period of time.
The absorption is undoubtedly du...
The diffusion presumably occurs
between the macro molecules which are
forced slightly apart.
For each 1% increase in the w...
The water sorption of acrylic can be
measured by -an increase in the weight of the
resin per unit of surface area exposed ...
(j) Solubility
The acrylic resins are soluble in many
solvents but they are virtually insoluble in
most fluids with which ...
(k) Creep:
Acrylic resins are viscoelastic when they are
subjected to a constant load so that strain can
be observed as a ...
(l) Colour stability
The colour stability is usually tested by
exposure to u.v. light.
The colour stability of heat cure a...
(m) Dimensional stability and accuracy
The dimensional stability of the resin during
processing and in service is importan...
(n) Processing stresses
Whenever a natural dimensional change is
inhibited the structure involved will be
stressed with th...
(o) Crazing
after processing, relaxation of surface stresses may
result in the formation of cracks or crazing.
Crazing of ...
The modern concept is that crazing is an
actual mechanical separation of the polymer
chains or groups of chains under tens...
Stability to heat
Polymethyl methacrylate is chemically
stable to heat.
It softens at 125ºC. However above this
temperatur...
(q) Thermal conductivity
Acrylic resins are poor thermal and electrical
conductors.
The coefficient of thermal conductivit...
(r) Coefficient of thermal expansion
They have high co-efficient of thermal
expansion of the range of 81x10-6 when
compare...
(s) Toxicology
There is no indication that these dental resins could
produce any systemic effects upon the patient.
The qu...
(t)Tissue compatibility and allergic
reactions
Possible allergic reactions to poly methyl
methacrylate have been postulate...
The residual monomer content of0.5%
is the component singled out as an irritant. But
it is found that the free monomer of ...
A true allergy to acrylic resin can be carried
out by a patch test.
The residual monomer can be reduced by
processing heat...
Inhalation of the monomer vapor can produce
toxic reaction. So use of the monomer should
be restricted to well ventilated ...
Growth of Candida albicans on the surfaces
of acrylic resin is a concern for patients. This
can be avoided by treating wit...
BARDAY S.C and FORSYTH. A
published a case report on BDJ 1999
October in which they have seen that
the colouring agents ad...
Infection control
Care should be taken to prevent cross
contamination between patients and dental
personnel.
They should b...
SHENEE and JAVID conducted a study to
find out the effect of disinfectants on acrylic
resins and they concluded that
Gluta...
In an another study conducted by
Watkinson A.C which appeared on
J. PROST DENT 1992 July he found
that transverse strength...
Acrylic Resin Cleansers
The most common cleansers used are the
immersion type which includes, alkaline
compounds, detergen...
Property Poly(methyl
methacrylates)
Density (g/cc)
Polymerization shrinkage
(% by volume)
Dimensional stability
Water sorp...
USES IN ORTHODONTICS
Chemically activated acrylic resins are mainly used in
orthodontics. The accuracy of fit and convenie...
Acrylics for bonding
Acrylic resins were the first material to be
used as orthodontic adhesive. The acrylic
resins used fo...
The Acrylic resins are (e.g., Orthomite, Genie) are
based on self curing acrylics and consists of methyl
methacrylate mono...
Most diacrylate resins are based on the
acrylic modified BISGMA or Bowen’s resin.
A fundamental difference is that the res...
The diacrylate resins have the best physical
properties and are the strongest adhesives for metal
brackets.
Buzzitta et al...
Diacrylate resins do not bond with plastic
brackets. Either an acrylic monomer as a
primer to enhance bonding between the
...
Other alternatives to chemically
autopolymerizing paste-paste systems.:
No-mix adhesives: These materials set (e.g.,
Rely ...
Visible light polymerized adhesives
These materials (e.g., Transbond) may be
cured by transmitting light through tooth
str...
Stereolithography
This technology uses a laser to cross link
specific areas as a pool of acrylic is being
filled.
Polymeri...
Newer advances in acrylic Resin
(1) High impact strength materials
These materials are butadiene-styrene rubber
– reinforc...
Indicated for patients who drop their
dentures repeatedly, e.g. senility,
parkinsonism
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(2) Vacuum adapted plates
A quick and easy method of making a usable
base plate is to vaccum mold a sheet of
thermoplastic...
(3) Rapid heat polymerized Resin
These are hybrid acrylics that are
polymerized in boiling water immediately after
being p...
(4) Carbon Fiber and polyaramid reinforcement of
acrylic resins
Early experiments with glass fiber have resulted in
failur...
Polyaramid or Kevlar fibres (poly p Phenylene
terephthalmide) have stiffness of 90 GPa
straw coloured and greatly enhance ...
ACRYLIC RESIN introduced into Dentistry about
70 years back. After its introduction into dentistry
it has revolutionized t...
Bonding adhesive
Ideal requirement
1.nontoxic
2.polymerize at or near body temperature with
minimal shrinkage
3.minimal ex...
5.strong-resist masticatory forces and
forces applied during orthodontic
treatment
6.Strain resistant
7.easy to use ,less ...
9.no additional equipment
10.option of bonding directly or indirectly
11.easy correction of shy spot
12.easy replacement o...
Types/classification
A.based on the bonding system type:
acrylic base system-
poly methyl methacrylate
diacrylate system-
...
Based on flouride content:
Flouride realising system
Non flouride releasing systems
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Based on curing system:
Self curing system
Light curing system
Dual curing system
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Based on the filler content:
Lowly filled bonding systems
Highly filled bonding systems
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Composites
Mixture of 2 or more components
Hard inorganic filler particle
+
Soft organic dimethacrylate polymer
Bone a nat...
Dr.Raphel Bowen:1960
Have the following major components:
organic resin matrix
inorganic filler
coupling agent
initiator-a...
Composition & strct
Resin matrix
Composed of mainly monomers & comonomer
Monomers of mol wt 100-1000g/mol
bis-GMA & UDEMA ...
Polymerization activated by
chemical,light,dual cure
Bis-GMA molecule:
2 reactive C=C grps
crosslinking strength
-OH grps ...
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Properties of bis-GMA:
Higher mol wtg than MMA
polymerization shrinkage
High mol wtg viscosity
TEGDMA,EDMA,MMA viscosity
w...
TEGDMA= DILUENTS
Viscosity
Polymerization shrinkage
So delicate balance maintained
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Clinical significance:
High conc of acrylate/MA grps remain
unreacted after setting as:
1.large size
2.rapid increase in v...
Benificial properties contributed by the resin:
1.molded at ambient temperature
2.sets by polymerization in short time
Dra...
Disadvantages of resins without filler:
Low MOE Flexibility marginal
breakdown
Low compressive strength & hardness
poor du...
Biological properties
Residual monomer MMA-irritant to pulp
Temperature rise –exothermic setting
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Filler:
Inorganic content(ceramic)
Advantages:
Polymerization shrinkage
COTE closer to that of tooth
Water absorption
Abra...
Uses:
Quartz filler:natural,inert(chemically
stable),strong,hardness
difficult polish
abrasion of opposite tooth
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Glass –fine sized particles
-barium,lithium aluminium silicate
-borosilicate glasses,strontium,zinc
glasses
Colloidal sili...
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Physical properties of the composite depend
on the filler quantity.maximum amt of filler
incorporated by:
1.selecting fill...
Type
Concentration
Particle size
Particle size distribution
-of the filler decide the properties
of composite
Trend of fil...
Coupling agent:
To improve properties filler(inorg. Phase)
should be bonded to resin matrix(organic
phase)
This bond achie...
Functions of coupling agent:
1. To physical,mechanical prop.
2. To retention of filler particles
abrasion resistance
3. St...
Mode of action of the coupling agent:
Silane molecule has reactive grps at
both ends
Reacts with the resin matrix at one e...
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SCOTHBOND
Coupling agent that is not a silane
Composed of halophosphorus ester of bis-
GMA,TEGDMA,benzoyl peroxide and an ...
Initiator & activator:
1.chemical cure-amine+BPO R*
BPO-initiator
tertiary amine-activator
2.visible light cure:
photoinit...
Pigments----for shades
Uv light absorber---to minimize color
change by oxidation
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Classification of
composites
Based on ADA specification no.27
Based on filler
Based on the method of polymerization
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1.As per the ADA specification no.27
classified into 2 types and 3 classes:
type 1-polymer based materials
suitable for re...
3 classes:
class1 - self cure materials
class 2 – light cure material
class 3 – dual cure material
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Classifacation based on fillers:
Macrofilled composite
Microfilled composite
Small particle composite
Hybrid composite
www...
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A.Macrofilled( traditional) composites:
first type of dental composite(1960)
quartz /glass filler(10-50um)
60-80% by weigh...
Disadvantages:
1. Polishability
2. Poor surface finish(dull appearance)
3. Rough finish-plaque retention
4. Staining
Preca...
Uses:
1. Some orthodontists still prefer,as
rough feel allows easy detection after
debonding
2. Class lll,lV
3. Class v
4....
Microfilled resins(late 1970s):
Enhanced polishability & esthetics over
traditional composites
Submicron particles(colloid...
Limitation:
Small particle size high surface
area(100-300m²/g) so not possible to
incorporate very high filler loading
det...
Advantage:
Smooth,lustrous surface finish
Disadvantage:
High resin content COTE
High resin content strength
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Uses of microfilled composites:
1. Where esthetics is dominant concern
2. Class lV
3. Veneers,to add translucency to core
...
SMALL PARTICLE COPMOSITES:
1980s
Filler size:avg-1-5um(range;0.5-10um)
80-85 wt%
60-77 vol%
Advantage:
Best physical prope...
Hybrid or blend composites(late1980s):
Esthetics + durability
Blend of conventional glass & quartz
particles(75%)(1-50u)
+...
Method of activation
A.Chemical cure
Tertiary amine(0.5%)+BPO(1%)
Early self cures –2pastes
Short working time:inhibitor d...
Disadvantage:
air entrapment during mixing
Limited working time
Setting characteristics:
Begins immedeately after mixing
G...
Material should not be disrupted once
the initial setting period start /working
time is over
disrupts polymerization
Desir...
Light cured composites
visible light cure
uv light (blue light cure)
Supplied as a sinlge paste
Contain monomer,comonomers...
Uv light cure:
360-400nm wavelength
Initiator-benzoyl methyl ether
Advantage:
Unlimited working time
Set on comand
Disadva...
Visible light cure:
400-500nm;greatest intensity arnd 480nm
Initiator system=diketone+amine
(campharoquinone)
Advantage:
1...
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Setting characteristics:
75% of polymerization takes place in 1st 10mt
,though curing continues for >24hr
Longer working t...
Depth of cure-2-3mm(VLC)
1.5-2mm(UVLC)
Factors affecting depth of cure:
1. Type of composite:
with darker shade penetratio...
2.Quanlity of light source:
480 nm
check quality at regular intervals
3.Method used:
Distance:light intensity on unit surf...
Avoid curing to >2mm fundamental
rule
Cure for atleast 40sec
Compatibility of light source:
Polymerization reaction of com...
1.heat of polymerization in VLC is liberated over a
small period of time
2.heating effect of the light activation unit.
To...
Light safety & protection:
1. avoid unnecessary exposure
2. Avoid direct exposure,don’t look direct
3. Use protective eye ...
Light curing units:
2 types presently:
Quartz-tungsten-halogen light
Plasma arc lights
Quartz tungsten halogen light:
Peak...
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Most units have light source & intraroal tip
together & are held by a gun type device with
a trigger.separate power source...
Plasma arc lights:
High intensity curing units 380-
500nm,480nm(peak)
Light obtained from the electrically conducive
gas f...
Disadvantage:
Requires special equipment
Precaution:
Storage of material away from sunlight
Lid replaced immediately
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Superiority of VLC over UVLC
Faster cure
Greater depth of cure
Cures through tooth structure and into
undercuts
No warm up...
Difference b/t CC & LC
Light cured
Polymerization is
always at the
surface close to the
light source
Less wastage of
mater...
Finish always better
Strength is higher
Command sets
Working time is more
No mixing required
More color stable
More resist...
New composites
Flowable composites:
1. For cervical lesions,pediatric use
2. <45% filler by vol
3. Low viscosity
4. Easily...
CONDENSABLE COMPOSITE:
Filler % similar to hybrid composite
Heavy consistency produced by using
modified fillers/altering ...
Properties
Physical properties
1.polymerization shrinkage:
is a direct function of the amt of resin present in
the composi...
Greater the diluent monomer, greater
the ploymerization shrinkage
Greater the unpolymerized
monomer,greater is the shrinka...
Water absorption:
Reasons:
Glass may be partially dissolved
Hydrolytic breakdown of the bond b/t filler and
resin
Incomple...
Effects of water absorption:
1. Detrimental on color stability
2. Discoloration by oral fluid absorption
3. Poor wear resi...
3.solubility:
0.01-0.0mg/cm²
Increased if incomplete polymerization
Manifested clinically as color instability
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4.coefficient of thermal expansion:
Has to be as close to tooth as possible
Filler has low COTE
Resin has HIGH COTE
Mismat...
Mechanical properties
1.Compressive strength:
Higher than tensile strength
Indicates brittleness
VLC=260Mpa
CC=210Mpa
CC s...
Microfilled composite have comp. St
similar to conventional, but
Lower yield stg(point of irretrievable
breakdown)
Low MOE...
Porosity –incorporated in 2 stages:
During incorporation of filler particles
into resin
During mixing two components
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Tensile strength
Composites tend to fail under tension
But measurement of t.s of brittle materails
difficult.
As the britt...
Modulus of elasticity
Measure of stiffness
Microfine composites have E ¼-½ of
highly filled fine composite,so tend to
flex...
4.Hardness:
Good indicator of wear resistance
hardness with filler content
+
degree of polymerization
VHN :unfilled resins...
5.Wear:
Loss of material by interfacial forces when 2
surfaces rub against eash other
Types:
Abrasive wear
Fatigue wear
Co...
Factors affecting:
filler content
Small particle wear
polymerization
Coupling agent
Porosity
Finish with diamond burs
Post...
6.Radio opacity:
by adding Barium,strontium
Color stability:
Oxidation of tertiary amine
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Biocompatibility
The ability of a material to elicit an
appropriate biological response in a given
application in the body...
2 key factors relevant when discussing
biological effect of a material:
1.Whether material releases any of its
components
...
In practice polymerization is not complete and small
amt of starting products are released.
There is no doubt that the cur...
Dental resin releases bis-GMA,
TEG-DMA and others
Controversy regarding the estrogenicity of dental resin
started froma si...
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Relevance:
Release of components a necessary factor,but
not sufficient event to cause adverse effect
Biological effect dep...
First generation bonding adhesives
Unfilled acrylic resins & epoxy resins
1st bonding adhesives used in
orthodontics unfil...
2 types of induction mechanism:
A)benzoyl-peroxide—tertiary amine
B)sulfinate system:
p-toulene sulfinic acid(accelerator ...
DISADVANTAGE OF UNFILLED RESINS:
Low hardness & strength
High co-efficient of thermal expansion
Lack of adhesion to tooth ...
EPOXY RESINS
Large no. of dental products that were epoxy
resins were developed esp
bis-GMA,an aromatic ester of a
dimetha...
b)second generation:
Uv light activated resins
Provided greater bond strength
Used bowen’s hybrid molecule-the back
bone s...
Advantages:
Higher bond strength then 1st gen
Low polymerization shrinkage
Greater hardness
Low water absorption
Disadvant...
Third generation(filled resins)
Late (1970s)
Filled resins with high % of inert filler,2 paste
system
Improved thermal exp...
COMPOSITION :
David Russel Barn etal combination of six-
stranded wire & concise will provide optimum
performance in bonde...
1 to 1 bonding:
2 paste self cure adhesive system
Extra small quartz particles-smooth mix,no
stick to spatula
Simple 1:1 m...
Eliminates bracket drift
Reduces decalcification due to feather edge
on the tooth surface
Recommended when close adaptatio...
EXTEND-a-BOND:
Highly filled ,self polymerizing 2 pase system
Low viscosity psate,small particle fillers
Longer working ti...
4th generation:
No –mix adhesives(1980s)
Composite placed on the tooth surface in
unpolymerized form
Polymerization cataly...
―Right-on‖ No mix adhesives:
Most advanced self curing bonding system
available
Superior bond strength
Drift proof bracket...
5th generation:
Visible light cure orthodontic adhesive
Douglas etal
Single paste system:ketone+amine
470nm λof light
TRAN...
Hugo.R.Armas Galindo etal:
Failure rates with VLC=11.3%
CC=12%
Trans Bond XT:
Leading light cured orthodontic adhesive
Ins...
Greenlaw etal:
1hr bond strength of VLC system 26% of 30hr
bond strg
Enamel loss with debonding & cleanup ½ of
with CC hea...
Rashid Ahmed Chamda-compared bond
strength achieved with LC bonding system &
CC over 24hr at 10mt,60mt,24hr found no
sign ...
Adhesion
boosters/hydrophilic
bonding systems
Failure of orthodontic bonded
attachments & brackets is mainly due to
contam...
Primers
Hydrophilic monomers carried in a
solvent,acetone,ethanol water or water
Solvents displace the water in the dentin...
www.indiandentalacademy.com
Coupling agents make the dentin
surface more hydrophobic
wetting by momomer
No shrinkage of resin tags away from
the denti...
Bonding agents
1st generation
Late 1956-Buonocore-GPDM containing
resin(glycerophosphoric acid-dimethacrylate)
1965-Bowen-...
Bonding mechanism:
chelation to Ca++ in the hydroxyapatite
Ignored the smear layer
Bond strength- 1-3Mpa
Drawbacks:
Debond...
2nd generation
Late 1970,early 80’s
1978 1st product-Clearfil bond system
Bonding mechanism:
surface wetting phenomenon
Io...
Content :
Polymerizable phosphates added to
bis-GMA resins(phosphate bonding systems)
3 types:
Phosphate ester based
Poly ...
3rd generation(late1980)
Smear layer either modified/partially
removed
2 imp changes:
Use of dentin conditioning
Use of hy...
Clinical steps:
Selective etching of enamel conditioner
10%H3PO4
Dentine conditioning 2% NITRIC
EDTA,maleic
Intermediate p...
4th generation:early1980
Transformed dentistry
total smear layer removal
Total etch concept-
Takao fusayama(1979)
(40% H3P...
HYBRIDIZATION-replacement of HA & H2O
in the surface dentine by resin)
Resin +remaining dentine=hybrid layer
Bond strength...
4-META product:
ORTHOMITE SUPERBOND
4META/MMA-TBB System:
10-3 Etch-10%citric acid
3% Fe3Cl
META-MMA:
methacryloyloxyethyl...
Bond strength:17-25Mpa
Eg:All bond2(Bisco)
Scotch Bond Multipurpose(3M)
Prime & bond
www.indiandentalacademy.com
5th generation
TOTAL SMEAR LAYER REMOVAL
TOTAL ETCH CONCEPT
2 STEP system:
etching
priming+bonding
www.indiandentalacademy...
As primer + bonding adhesive together in 1
bottle=ONE BOTTLE ADHESIVES
2STEP ETCH & RINSE ADHESIVES
Rely on hybridization ...
Contents=PHOSHORIC ACID+PENTA
EG:One step,Single Bond(3M)
www.indiandentalacademy.com
PENTA
Multifunctional phosphate based molecule
Dipentaerythrytol pente acrylate phosphoric
acid ester
Weakly acidic
Per mo...
Prime & bond NT
Etchant-34% or 36%H3PO4
Primer adhesive:PENTA,UDMA
elastomeric resins
T-resis(cross linkin)
D resins(hydro...
6th generation
One step bonding
No etch , no rinse,no cure
Self etching primer+bonding adhesive
2 types-mix(etchant & prim...
2 clinical steps clubbed--- etching + priming
By the use of acidic primer(self etching
primer)these are not rinsed off
Les...
Eg:
Promt-L-Pop(ESPE,Germany)
Unit dose system in blister pack
Etchant,primer,adhesive,microbrush
sealed in a triple lolli...
Red blister-initiator,stabilizer,MA phosphate
esters
Yellow blister-stabilizer,H2O,Flouride complex
Green blister –microbr...
7th generation
ALL IN ONE ADHESIVE
Etchant+primer+adhesive in one solution
Also called:All in one self priming
adhesive/Si...
Resin modified
glass ionomer
www.indiandentalacademy.com
Hybrid materials have been developed to over
come some shortcomings in GICs:
Short working time
Long setting time,not comm...
www.indiandentalacademy.com
Resin modified GIC
light activated chemical cure
Advantages:
Bond to E & D
Flouride release
Prolonged working time
Command...
Composition:
Ceramic powder:ion leachable powder
70-75% by weight
organic matrix-forming molecules
Most imp changes :
Repl...
Powder:fluoro aluminium silicate glass
Liquid-copolymer of acrylic acid &
nueclic acid
HEMA
Water
Campharoquinone
P/L:3:1
...
Amount of demineralization adjacent to
the bracket is reduced
Reduction in strep.mutans & lactobacilli
around the brackets...
Compomer
Composite +ionomer
Anhydrous single paste
Contents:
Powder:aluminium fluorosilicate glass,
sodium flouride
chemic...
Liquid:polymerizable methacrylate
carboxylic acid monomer
diacrylate monomer
No water,ensures that initial setting accurs ...
Advantages:
Excellent esthetics
Low solubility
High bond strength
High fracture toughness
Drawbacks:
Require bonding agent...
Reliance quick cure
orthodontic paste
Light curing of metal bracket in 6 sec
Unique chemistry provides a broader area of
s...
Flouride releasing
adhesives
Flouride reservoir that does not depend on
the patient co-operation
Light cure/chemical cure
...
Flouride release:
Most of it in 1st few days /wk
with ph
Recharging
Mark.L.Underwood etal:FR2.5 ortho
adhesive:
Flouride i...
DUAL CURE RESINS
1980S
LIGHT CURE+CHEMICAL CURE
Eg:Vivadent Thick,Viva Dent Thin
Advantage:
Reduced bonding time
20 bracke...
Allow set by CHEMICAL CURE
Visble light cure 30s
10s VLC chemical cure:allows
proper placement of bracket
www.indiandental...
Cyanoacrylate
Smart Bond
1991-ethyl cyanoacrylate tested for
orthodontic bracket adhesive
High tensile strength
Polymeriza...
Imp that surfaces to be bonded are close to
each other ,as material can’t flow,fill gaps
Wilner & Oliver-unsuitable for ro...
www.indiandentalacademy.com
Thank you
For more details please visit
www.indiandentalacademy.com
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Resins in orthodon 2 /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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Resins in orthodon 2 /certified fixed orthodontic courses by Indian dental academy

  1. 1. Resins in orthodontics www.indiandentalacademy.com INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
  2. 2. Polymerization can be activated by chemical,light or dual cure Bis-GMA molecule: 2 reactive C=C grps cross linking strength -OH grp cross linking www.indiandentalacademy.com
  3. 3. Introduction Dynamically growing science Discovery of new techniques,materials Improvement over older ones Synthetic resins-single class of substances that has influenced modern living www.indiandentalacademy.com
  4. 4. By def,non metallic compounds synthetically produced that can be molded into various forms,used for various purposes. Chemical similarities-all are composed of polymers Resin currently widely used-based on acrylic resins called methyl methacrylic acid Wide application-denture bases removable appliances impression trays obturators www.indiandentalacademy.com
  5. 5. History Goodyear(1840) :1st org polymers rubber & vulcanite Other polymers J.W.Hyatt(1869) :cellulose L. Baekland(1907) :bakelite W.l. Semon :polyvinyl chloride W.S. Carothers(1925) :synth. rubbers www.indiandentalacademy.com
  6. 6. Polymers truly adequate for dental purpose(1930s) O.rohn(1936): Polymethyl methacrylate(plexiglass) 1946:- 98% of denture bases were of acrylic 1945:-Self cured resins 1st used in germany 1970:- fluid resin introduced www.indiandentalacademy.com
  7. 7. mid 1950s-direct bonding with epoxy resins 1955- Buonocore demonstrated acid etch 1958-Salder attempt to direct bond without etch Early 1960-epoxy acrylates 1962-bowen-bis-GMA,monomer consists of a reaction product 4-4’isophylidine phenol and glycidyl methacrylate Mid 1960- use of bis-GMA resin composites www.indiandentalacademy.com
  8. 8. Newman(1965):1st to bond orthodontic attachments to the teeth by means of epoxy resin,used low mol. Wt epoxy resin liq with high mol. Wt solid epoxy & polyamide curing agent,fast cure,reduced irritation potential Cueto(1966):used liq monomer methyl methacrylate & silicate filler,working time-1mt setting time-2 to 4mt Mitchel(1966):failures with epoxy resin Buonocore etal(1968):acid conditioning-prism tags Retiel etal(1970):thich adhesive interface—more imperfections,greater polymerization shrinkage Miura etal(1971):modified tri alkyl borane catalyst,useful for bonding plastic brackets,enhanced adhesion in presence of moisture. www.indiandentalacademy.com
  9. 9. Reynolds(1975):maximum tensile bond strength of 5.9 to 7.9 Mpa adequate,in vitro tensile strength level of 4.9Mpa clinically acceptable. Keizer etal(1976):large standard deviation for bond strength—speculation on reliability. Zachrisson(1978):remnants of adhesive material remained on the enamel surface after debonding & all modalities of debonding abraded enamel to varying degrees,thus none left a perfect surface. Tavas etal(1979)light activated composites,significant increase in bond st. of all materials after 24hr as compared to values 5mts after bonding www.indiandentalacademy.com
  10. 10. Other polymers- Polyurethane,polystyrene,vinyl acrylic Recently-lass fibers,carbon fibre graphite,polyaramide fibers added to acrylis to improve mech. Properties Rubber & butadine reinforced acrylics www.indiandentalacademy.com
  11. 11. Classification of resins 1) natural resins:complex of C,H,O in paints,perfumes,medicine dentistry-separating media,cavity liner synthetic resins:non metallic compounds,synthetically produced from org. compounds,which can be molded into various forms,hardened for commercial use,commonly called plastics,bcz of their plastic beh. under heat & pressure. www.indiandentalacademy.com
  12. 12. Synthetic resins are formed by a chemical process ,polymerization in which simple molecules with identical structure link upto form a large molecule of high molecular weight. Poly=many Mer=units Compounds having Mol wt>5000-macromol. www.indiandentalacademy.com
  13. 13. Synthetic resins A)thermoplastic: Softens when heated above the glass transition temp Tg,at which the molecular motion begins to force the chains apart.resins shaped,molded,hardened on cooling. They are fusible I.e; they melt They are soluble in organic solvents Eg: poly methyl methacrylates,polyvinyl acrylics,polystyrenes www.indiandentalacademy.com
  14. 14. B)thermosetting resins: Undergo chemical change & become permanently hard when heated above the temp at which they began to polymerize Don’t soften again on reheating Infusible,insoluble Superior abrasion resistance,dimensional stability Eg: cross linked poly methyl methacrylate,silicones www.indiandentalacademy.com
  15. 15. Ideal requirements 1. Should be tasteless, odorless, non- toxic and non-irritant to the oral tissues. 2. Aesthetically satisfactory, i.e. should be transparent or translucent and easily pigmented. The color should be permanent. 3. Should be dimensionally stable. It should not expand, contract or warp during processing and subsequent use by the patient. 4. Have enough strength, resilience and abrasion resistance. www.indiandentalacademy.com
  16. 16.  . 5. Be insoluble and impermeable to oral fluids. 6. Have a low specific gravity (light in weight) 7. Tolerate temperatures well above the temperature of any hot foods or liquids taken in the mouth without undue softening or distortion. 8. Be easy to fabricate and repair. 9. Have good thermal conductivity. 10. Should be radio opaque 11. Thermal coefficient of exp should match tooth www.indiandentalacademy.com
  17. 17. Uses of resins 1. Preparation of dentures 2. Artificial teeth 3. Tooth restoration 4. Cementation of crowns and bridges 5. Orthodontic and pedodontic appliances 6. Crown and bridge facings 7. Maxillofacial prostheses 8. Inlay and post core patterns www.indiandentalacademy.com
  18. 18. Temporary crowns and bridges Dies Implants Endodontic and core filling materials Athletic mouth protectors Impression trays Splints and stents Models www.indiandentalacademy.com
  19. 19. Terms Polymer:molecule made of many parts composed of non metallic elements bonded by covalent bonds large molecular size,weight Eg:polymerization of methyl methacrylate monomer(100g/mol) into poly methyl methacrylate polymer(30,000g/mol) Named accrd to mers Eg:polymethyl methacrylate OR by prefixing poly to the kind of monmer chemical links eg:polyamide,polyester commercial names:nylon,dacron,plexiglass,teflon www.indiandentalacademy.com
  20. 20. Monomer: Molecules from which the polymer is constructed;homopolymer or copolymer Molecular weight: Molecular weight of the various mers multiplied by the no. of mers Thousands to millions Affects the physical property of resin www.indiandentalacademy.com
  21. 21. Chain length vs. mol wgt: Longer the polymer chain—more the no. of entanglements,more difficult to distort the polymer Increased rigidity,strength,melting temp Mol wt of commercial dental resins 8,000- 39,000 www.indiandentalacademy.com
  22. 22. Degree of polymerization: Def as the total no. of mers in the polymer The higher the mol wt of the polymer made from a single monomer higher is the degree of polymerization Strength of resins increase with the degree of polymerization Avg degree of polymerization= total no. of str units/total no. of molecules Narrow mol wt distribution gives useful polymers Higher the mol wt, high softening tmp,melting pt,increased rigidity www.indiandentalacademy.com
  23. 23. Polymerization The process of forming a poly mer from identifiable subunits,monomers is polymerization 2 main types: condensation or step growth addition polymerization www.indiandentalacademy.com
  24. 24. Condensation polymerization Polymerzation acomplished by repeated elimination of small molecules;byproducts- water,halogen acids,ammonia So there is a change in composition Components are difunctional monomers All cure or become reactive simultaneously Reaction very slow Stop before they form v high mol wt polymer www.indiandentalacademy.com
  25. 25. www.indiandentalacademy.com
  26. 26. www.indiandentalacademy.com
  27. 27. www.indiandentalacademy.com
  28. 28. www.indiandentalacademy.com
  29. 29. Addition polymerization Most of the resins employed in dentistry Starts from a active centre adding one monomer mol at a time to rapidly form a chain.theoritically this chain can grow indefinitely Monomers are activated one at a time ,add together in sequence to form a growing chain Process simple but control difficult No change in composition www.indiandentalacademy.com
  30. 30. Inorder to be polymerized the monomer must have a unsaturated grp its structural formula.on activation of the monomer mol. The bonds open up and collide with another molecule,which inturn become activated and covalent bonding takes place Reaction exothermic www.indiandentalacademy.com
  31. 31. copolymerization Two or more chemically different monomers,each with some desirable property can be combined to yeild a polymer with specific property Eg:ethyl acrylate copolymerized with methyl methacrylate to alter the flexibility & fracture resistance of a denture www.indiandentalacademy.com
  32. 32. Copolymer strc. Three types: 1.random copolymer:no sequential order btw two or more mer units 2.block copolymer:mer units occur in relatively long sequences 3.graft/branched copolymer: Sequence of one type of mer unit are attached onto a backbone of second type of mer unit www.indiandentalacademy.com
  33. 33. Random copolymer: ABBABABAAABAAABABBBBABAAABABB BLOCK COPOLYMER AAAAAABBBBBBBAAAAAABBBBBAAAAA GRAFT OR BRANCHED COPOLYMER AAAAAAAAAAAAAA B B B B www.indiandentalacademy.com
  34. 34. www.indiandentalacademy.com
  35. 35. Polymers strc 1.linear:structural units are connected to one another in linear sequence 2.nonlinear or branched polymers: (Temporary connections) 3.cross linked polymers: Form chemical bondage btw adjacent chain of linear polymers giving rise to three dimensional network-imp physical properties like,high strength,low solubility and water sorption permanent connections btw chains www.indiandentalacademy.com
  36. 36. www.indiandentalacademy.com
  37. 37. www.indiandentalacademy.com
  38. 38. www.indiandentalacademy.com
  39. 39. Stages of polymerization 1.induction: - two processes control induction: activation & initiation -for Add. Poly. to begin a source of free radical R* is required. Free radicals can be genrated by activation of the radical producing molecule using:chemical Heat Visible light Uv light Energy transfer from another compound www.indiandentalacademy.com
  40. 40. www.indiandentalacademy.com
  41. 41. Prerequisite for add.Poly.- presence of unsaturated group(double bond). when a free radical & its unpaired electron approach a monomer with its high electron density double bond,an electron is extracted & it pairs with R* electron to form a bond b/t the radical & monomer mol., leaving the other electron of the double bond unpaired.thus the original free radical bonds to one side of the monomer mol. & forms a new free radical site at the other end.the reaction is now initiated. www.indiandentalacademy.com
  42. 42. Benzoyl peroxide is the common initiator mol. Used. At 50-100c it forms 2 free radicals Chemical activation:2 reactants mixed,tertiary amine (activator)+BPO(initiator) Heat Uv light: adverse effect on retina & unpigmented oral tissue,limited pentration,loss of intensity of the light source over time VLC: Campharoquinone & an org amine(dimethylaminoethylmethacrylate) 470nm wavelenght of light One part system,stored unexposed to light www.indiandentalacademy.com
  43. 43. Initiation period is greatly influencved by the purityof the monomer.impurities react with the activated groups—increase in the induction period. Induction energy for activation of each monomer mol-16,000-29,000cal/mol www.indiandentalacademy.com
  44. 44. www.indiandentalacademy.com
  45. 45. Propagation: less energy needed,5000-8000cal/mol free radical-monomer complex acts as a new free radical centre when it approaches another monomer to form a dimer,which also becomes a free radical www.indiandentalacademy.com
  46. 46. www.indiandentalacademy.com
  47. 47. Chain transfer: Active sites is transferred from an activated radical to an inactive molecule and a new nucleus for further growth is created www.indiandentalacademy.com
  48. 48. www.indiandentalacademy.com
  49. 49. www.indiandentalacademy.com
  50. 50. Termination: Takes place either by direct coupling or exchange of hydrogen atom from one growing chain to another www.indiandentalacademy.com
  51. 51. www.indiandentalacademy.com
  52. 52. inhibitors Inhibition of polymerization: Impurity that can react with the free radical will inb. the polymerization Eg:hydroquinone(0.006% or less) Oxygen inhibition www.indiandentalacademy.com
  53. 53. Acrylic resins Derivatives of ethylene & contain a vinyl group in their structural formula 2 acrylic resin series : derived from acrylic acid derived from methacrylic acid both polyacids are hard & transperent but their polarity rel to carboxly grp causes imbibation of water.water tends to separate the chains—softening & loss of strength. H2C=CHR www.indiandentalacademy.com
  54. 54. Plasticizers Added to resins to reduce their softening or fusion temp. Increase the solubility of the polymer in the monomer & decrease the brittleness of the polymer Action: partial neutralization of the secondary bonds or inter molecular forces-leading to-slipping of resin molecules past one another under stress. External:not part of polymer,penetrates b/t macromol increasing the inter molecular spacing Internal:by copolymerizationof suitable plasticizer eg:butyi methacrylate add to methyl methacrylate www.indiandentalacademy.com
  55. 55. Esters of polyacids are of greater interest in dentistry Polymethyl methacrylate is the hardest resin of the series with the highest softening temperatures. www.indiandentalacademy.com
  56. 56. Methyl methacrylate: monomer in liquid form Clear transparent liquid at room temp Physical prop:melt. Pt:-48c Boiling pt-100.8c density-0.945g/ml at20c heat of polymerizatin-12.9kcals/mol Exhibit high vapour pressure and is an excellent organic solvent Although heat,uv,vlc possible, chemical initiator common www.indiandentalacademy.com
  57. 57. www.indiandentalacademy.com
  58. 58. Degree of polymerization varies with the conditons:temperature method of activation type of initiator conc; purity of chemicals Vol. Shrinkage of 21% occurs during the polymerization of pure monomer www.indiandentalacademy.com
  59. 59.  Polymethyl methacrylate: Linear polymer in powder form Transparent resin,colored or tinted Transmit light into the uv range to wavelenght of 0.25mcm Hard resin-18-20khn Tensile strength 8,500psi or 60Mpa Modulous of elasticity:3,50,000psi or 2.4Gpa Sp.gravity 1.19g/cm www.indiandentalacademy.com
  60. 60. Stable resin which will not discolor in uv light and exhibit remarkable ageing prop Chemically stable to heat,softens at 125c can be molded as a thermoplastic material Depolimerizes above 125-200c,at 450c 90% depolymerization Exhibit tendency to imbibe water.its non crystalline structure posses a high internal energy.thus molecular diffusion can occur in the resin bcz less actvn energy reqd. Greater the ml wt less the sorption Sorption high in the 1st week,is reversible Soluble in org solvents;chloroform,acetone Adv:eas in processing,polymerizes readily under conditions of use www.indiandentalacademy.com
  61. 61. www.indiandentalacademy.com
  62. 62. www.indiandentalacademy.com
  63. 63. www.indiandentalacademy.com
  64. 64. www.indiandentalacademy.com
  65. 65. COPOLYMERIZATION www.indiandentalacademy.com
  66. 66. Composition of acrylic resin(heat cure) Monomer:pure methyl methacrylate hydroquinone(.006%)-inhibitor Polymer:polymethyl methacrylate Ethylacrylate(co polymer)-increases the solubility of the polymer in monomer dibutyl phthalate-8-10%-plasticizer initiator-BPO pigments cross linking agent-glycol dimethacrylate www.indiandentalacademy.com
  67. 67. Principal Ingredients of Acrylic Resins: Powder and Liquid Powder Liquid Poly (methyl methacrylate) and other co- polymers (5%) Initiator (benzoyl peroxide) Pigments Dyes Opacifiers (Zn/Ti oxide) Plasticizer (dibutyl phthalate) Dyed organic fibers Inorganic particles (glass fibres or beads) www.indiandentalacademy.com
  68. 68. Monomer (methyl methacrylate) Inhibitor (hydroquinone) Accelerator Plasticizer (dibutyl phthalate) Cross-linking agent (glycol dimethacrylate) www.indiandentalacademy.com
  69. 69. Storage:tumble the powder in the container to restore uniform distribution of the different particle sizes. liquid kept in tightly sealed container to guard against evaporation of the most volatile ingredient Seperating media:tin foil,cellulose lacquer,sol of alginate compounds,sodium silicate,starches water sol alginates most popular-forming insoluble calcium alginate film on gypsum Polymer:monomer::3:1 by volume;2:1 by weight www.indiandentalacademy.com
  70. 70. Monomer-polymer reaction 4 stages: Stage1:wet sandy stage:polymer settles down into monomer & incoherent mass formed Stage2:sticky stage:monomer attacks the polymer stringiness if touched www.indiandentalacademy.com
  71. 71. Stage3:dough or gel stage as polymer becomes saturated with the monomer it gives dough like consistency,doesn’t stick to jar walls Stage4:rubbery stage monomer disappears by more penetration into the polymer,the mass more cohesive,rubber like,cant be molded www.indiandentalacademy.com
  72. 72. Dough forming time: The time required to reach stage3 Depends on the solubility of the polymer pearls in monomer Factors affecting: Increase temp but not above 55c Size of the polymer particles;smaller the particles ,faster the reaction,short DFT ADA no.12 <40mt,but most reach with in 10mt Working time: Time elapsed b/t stage 2 & beginning of stage4. Time during which material is in dough form ADA no.12 dough should be moldable for 5mt min Decreased temp longer working time www.indiandentalacademy.com
  73. 73. Curing procedure: Packing:in dough stage acrylic introduced 30-60mt of bench curing- to allow equilibriation of pressure Polymerisation:the BPO in acrylic when heated above 60c decomposes to give free radicals. Curing cycle:denture flask placed immedeately in water at 65c allowed to remain for 90mt to polymerize thick areas without porosity,then boiled for 60mts to cure the thin palate areas. OR 74c for 9hrs Bench cooling :30mts,then cold tap water 15mts ideally overnight to reduce warpage Deflask carefully www.indiandentalacademy.com
  74. 74. INJECTION MOLDING TECHNIQUE It requires special equipment. The mold space is filled by injecting the resin under pressure. A sprue hole and a vent hole are formed in the gypsum mold. The soft resin is contained in the injector and is forced into the mold space as needed. It is kept under pressure until it has hardened. No trial closure is required with this technique. There is no difference in accuracy or physical properties as compared to compression molding technique. Advantages of this technique are good dimensional accuracy, low free monomer content good impact strength. Disadvantages are high cost of the equipment, difficult mold design problems, less craze resistance, less creep resistance and requirement of special flask. www.indiandentalacademy.com
  75. 75. Other sources of heat (1) Steam (2) Dry air oven (3) Dry heat (electrical) (4) Infrared heating (5) Induction or dielectric heating (6) Microwave radiation Microwave energy can be used for the polymerization of acrylic resin. Microwaves are used to generate heat inside the resin by a generator called magnetron. Advantage: Faster than heat cure technique Less prone to porosity Initiator used is benzoyl peroxide www.indiandentalacademy.com
  76. 76. Chemically cured acrylics Self curing or auto polymerizing or cold curing Instead of using heat to activate BPO, a tertiary amine(chemical activation),NN- dimethyl para toludine added to monomer before mixing Toludine conc-0.75%,BPO 2% Smaller the particle size more rapid is the polymerization www.indiandentalacademy.com
  77. 77. Heat cure vs cold cure Degree of polymerization is less than heat cured,inferior properties Color stability poorer bcz of tertiary amine oxidation,minimized by adding stabilizing agent For repair cold cure used as heat cure warps Better initial fit,as curing at room temp www.indiandentalacademy.com
  78. 78. Mixing techniques for self cure resins (a) Salt and pepper method (b) Knead – on method (c) Compression molding technique (d) Injection molding technique (e) Fluid resin technique www.indiandentalacademy.com
  79. 79. Salt and pepper method (sprinkle on technique) After application of separating media the polymer is uniformly sprinkled over the cast. Then the monomer is introduced form a dropper so that no excess monomer is splashed over the powder. This process is continued until the entire powder reacts with the liquid to form the acrylic resin with the metallic components incorporated in the resin mass for retention. Soon after acrylization the acrylic resin is immersed in a bowl of water to prevent monomer evaporation and thus preventing granular porosity. www.indiandentalacademy.com
  80. 80. Knead - on Method The powder and the liquid are mixed and when dough stage is reached the mix is molded on to the surface of the cast and shaped accordingly.  Disadvantages: (1) Fit of the base to the cast is not as good as that obtained with salt and pepper method. (2) The finger of the operator should be protected as it comes into more contact with the monomer. www.indiandentalacademy.com
  81. 81. Fluid resin technique (pour-type acrylic resins) The chemical composition of this type of resins is the same as that of polymethyl methacrylate resins. The principal difference is that the pour-type of denture resins have high molecular weight powder particles that are much smaller and when they are mixed with monomer, the resulting mix is very fluid. They are used with significantly lower powder-liquid ratio, i.e. it ranges from 2:1 to 2.5:1. Agar hydrocolloid is used for the mold preparation in place of usual gypsum. The fluid mix is quickly poured into the mold and allowed to polymerize under pressure at 0.14 M Pa. www.indiandentalacademy.com
  82. 82. The advantages: better tissue fit fewer open bites less fracture of porcelain teeth during deflasking reduced material cost and simple laboratory procedure. The disadvantages: air inclusion (bubbles) shifting of teeth during processing, closed bites (infraocclusion) occlusal imbalance due to shifting of teeth, incomplete flow of the material over neck of anteriorwww.indiandentalacademy.com
  83. 83. Some acrylic resins instead of the amine peroxide system utilize the sulfonate or sulfinic acid system for polymerization. The colour stability has improved over the amine peroxide system. The sulfinic acid and its salts are unstable in the presence of moisture. www.indiandentalacademy.com
  84. 84. LIGHT ACTIVATED DENTURE BASE RESINS Douglas etal . The first light activated system utilized u.v. light to initiate free radicals. Subsequently visible light activating systems were developed with a greatly improved ability to polymerize thicker increments. They have totally displaced the u.v. light systems. It consists of a urethane dimethacrylate matrix acrylic copolymer, microfine silica fillers, and a camphoroquinone- amine photo-initiator system. www.indiandentalacademy.com
  85. 85. The amine accelerator used is DEAEMA (Diethyl- amino-ethyl methacrylate) at a concentration of about 0.15% or less. It is supplied in premixed sheets having clay like consistency. It is provided in opaque light tight packages to avoid premature polymerization. with blue light of 400 – 500 nm from high intensity quartz halogen bulbs. www.indiandentalacademy.com
  86. 86. PHYSICAL PROPERTIES OF ACRYLIC (a) Strength The strength of the acrylic resin denture base materials may fluctuate considerably depending on: the composition of the resin. the technique of processing. the subsequent environment of the denture. The lower the degree of polymerization of a given solid polymer the lower will be its strength. www.indiandentalacademy.com
  87. 87. The stress properties of the resin are generally measured by means of a transverse test described by the ADA sp no. 12 Transverse strength is a combination of tensile strength and compressive strength. strength varies from 78 to 92 MPa. Owing to the lower degree of polymerization, the maximal strength and stiffness of the self cure resins are lower than that of the heat cured type. The mean flexural modulus for heat cured resin is 2500 MPa and that for self cured resin is about 2200 MPa. www.indiandentalacademy.com
  88. 88. The modulus of elasticity, the proportional limit and tensile strength of heat cure acrylic resin is about 2350 Mpa, 27 Mpa, 52 Mpa, respectively. The properties of the resin are reduced by the heat generated from polishing with abrasive and polishing agents. The excess heat generated may cause partial depolymerization with resulting decrease in strength and rigidity. . www.indiandentalacademy.com
  89. 89. The bulkier portion of the denture may show greater strength than the thinner portion because of more degree of polymerization. www.indiandentalacademy.com
  90. 90. (b) Impact strength It is a measure of the energy absorbed by a material when it is broken by sudden blow. The plasticizing ingredients may increase the impact strength of acrylic resin but they decrease the hardness, proportional limit, elastic modulus and compressive strength. The charpy impact strength of heat cured acrylic resin is 0.98-1.27 joules and that of self cured resin is 0.78 joules. The Hounsfield impact strength of heat cured acrylic is 455 Nmx10-4 www.indiandentalacademy.com
  91. 91. (c) Hardness The knoop hardness no - for self cure resin is approximately 16-18 -for a resin cured under heat may be as high as 20. -The low hardness no. of acrylic resin indicates that these materials may be scratched easily and abraded. (d)Modulus of elasticity They have sufficient stiffness (2400 MPa) for use in complete and partial dentures. Self cured acrylic resins have slightly lower values. www.indiandentalacademy.com
  92. 92. (e) Abrasion Resistance This has been evaluated by abrading specimens against 600 grit silicon carbide paper for 1 hour under a stress of 0.76 MPa in water at 37 c and measuring loss of material. For Heat cure it is 530 mmx10-3 and self cure it is 611mmx 10-3. (f) Density: The acrylic resin has densities ranging from 1.16 to 1.36g/cc. www.indiandentalacademy.com
  93. 93. (g) Polymerization shrinkage When methyl methacrylate monomer is polymerized the density changes from 0.94 gm/cm2 to 1.19 gm/cm3. This change in density results in a volumetric shrinkage of 21% usually called polymerization shrinkage. But this shrinkage is distributed uniformly throughout the surfaces so that the fit of the denture to the tissues is not seriously affected. Another shrinkage called linear shrinkage varies from 0.2% to 0.69% for acrylic resins heat cure. www.indiandentalacademy.com
  94. 94. The processing shrinkage has been measured as 0.53% for heat cured acrylic resin as compared with only 0.26% for a self cured resin. The fit of the acrylic resin produced from heat cure resin is lower than that of self cure resin. www.indiandentalacademy.com
  95. 95. (h) Porosity There are a number of causes of porosity that can occur during the processing of the acrylic resin. If the porosity appears on the surface of the resin cleansing will be difficult. If the porosity is internal the cured resin will be weakened. More over such area of internal pore or bleb is an area of stress concentration; the resin may warp as the stresses relax. www.indiandentalacademy.com
  96. 96. Internal porosity of the resin occurs as a result of the vaporization of the monomer or of the low molecular weight polymers when the temperature of the resin increases above the boiling point of the monomer (100.8º C). It is confined to the thick portions of the denture base and it may not occur uniformly. It can be avoided by curing dentures with excessive thickness using long , low temperature curing cycle. www.indiandentalacademy.com
  97. 97. Second type of porosity (external porosity) is due a lack of homogeneity in the dough at the time of the polymerization. It is seen that some regions will contain more monomer than other and these regions will shrink more during polymerization than the adjacent regions & such a localised shrinkage will lead to void formtn. www.indiandentalacademy.com
  98. 98. It is avoided by using (a) Proper P:L ratio (b) Favorable mixing procedures (c) Pack during the dough stage External porosity can also occur due to lack of adequate pressure during polymerization by a definite lack of dough or gel at the time of final closure. It is avoided by using the required amount of dough. www.indiandentalacademy.com
  99. 99. (i) Water absorption Poly methyl methacrylate absorbs water slowly over a period of time. The absorption is undoubtedly due to the polar properties of the resin molecules. The diffusion coefficient of a heat cured denture acrylic resin is 1.08 to 10-12 m2/sec at 35 C ,when the temperature drops to 23 c it is reduced by one half. For self curing resin D is 2.34 x 10-12 m2/sec. www.indiandentalacademy.com
  100. 100. The diffusion presumably occurs between the macro molecules which are forced slightly apart. For each 1% increase in the weight due to the water absorbed the acrylic resin expands linearly 0.23%. www.indiandentalacademy.com
  101. 101. The water sorption of acrylic can be measured by -an increase in the weight of the resin per unit of surface area exposed to the water. According to ADA sp. No. 12 a disc of material with specified dimensions is prepared,the disk is first dried to constant weight and then it is stored in water for seven days. According to the specification the gain in weight by the resin during this treatment must not be greater than 0.8mg/cm2. www.indiandentalacademy.com
  102. 102. (j) Solubility The acrylic resins are soluble in many solvents but they are virtually insoluble in most fluids with which they will come in contact in the oral cavity. They are soluble in ketones, esters, and aromatic and chlorinated hydrocarbons eg:chloroform and acetone. Alcohol cause crazing in some resins. www.indiandentalacademy.com
  103. 103. (k) Creep: Acrylic resins are viscoelastic when they are subjected to a constant load so that strain can be observed as a function of time they show primary and secondary creep. Creep rate increases with increase in temperature, stress, residual monomer, plasticizers and cross linking agents. The creep rate for self cure resins is more than heat cure resins. www.indiandentalacademy.com
  104. 104. (l) Colour stability The colour stability is usually tested by exposure to u.v. light. The colour stability of heat cure acrylic resin is more when compared to self cure acrylic resin. According ADA sp. No. 12 when a specimen is exposed for 24 hours to an u.v. light source shall not show more than a slight change in colour when compared with an original specimen. www.indiandentalacademy.com
  105. 105. (m) Dimensional stability and accuracy The dimensional stability of the resin during processing and in service is important in the fit of the denture and the satisfaction of the patient. If the denture is properly processed the original fit and dimensional stability of the various denture base plastics is good. However excess heat generated during finishing can easily distort a denture base by releasing residual stresses. www.indiandentalacademy.com
  106. 106. (n) Processing stresses Whenever a natural dimensional change is inhibited the structure involved will be stressed with the result that a distortion or warpage may occur if such stresses are relaxed. During polymerization shrinkage tensile stresses are actually induced in acrylic resin. The total dimensional change that occurs in a typical resin denture during processing and in service is in the range of only 0.1 to 0.2 mm. www.indiandentalacademy.com
  107. 107. (o) Crazing after processing, relaxation of surface stresses may result in the formation of cracks or crazing. Crazing of the resin actually consists of small cracks that may vary in size from microscopic dimensions to a size that is readily visible. Crazing may occur under mechanical stress or as a result of an attack by a solvent. Crazing occurs only when a tensile stress is present. The cracks appear at right angles to the direction of the tensile stress. . www.indiandentalacademy.com
  108. 108. The modern concept is that crazing is an actual mechanical separation of the polymer chains or groups of chains under tensile stress. Crazing can be avoided by using cross linked acrylics, tin foil separating medium and metal molds. www.indiandentalacademy.com
  109. 109. Stability to heat Polymethyl methacrylate is chemically stable to heat. It softens at 125ºC. However above this temperature it begins to depolymerize. At 450º C, 90 % of the polymer will depolymerize to monomer. www.indiandentalacademy.com
  110. 110. (q) Thermal conductivity Acrylic resins are poor thermal and electrical conductors. The coefficient of thermal conductivity for acrylic resin is 5.7x10-4 compared to 1.3x10-3 for dentin. Low thermal conductivity results in plastic resin bases serving as an insulator between the oral tissues and hot or cold materials placed in the mouth. www.indiandentalacademy.com
  111. 111. (r) Coefficient of thermal expansion They have high co-efficient of thermal expansion of the range of 81x10-6 when compared to tooth having only 11.4 x 10-6 . Thermal expansion is important for the fit of the acrylic bases– an acrylic base that fits a cast accurately at room temperature will not fit the same at mouth temperature. www.indiandentalacademy.com
  112. 112. (s) Toxicology There is no indication that these dental resins could produce any systemic effects upon the patient. The quantity of methyl methacrylate monomer that might enter the circulation by passing through the oral mucosa would be extremely low. The half life of methyl methacrylate in blood at 37 c is said to range between 20-40 minutes. Clearance being by hydrolysis to methacryclic acid. www.indiandentalacademy.com
  113. 113. (t)Tissue compatibility and allergic reactions Possible allergic reactions to poly methyl methacrylate have been postulated. Chemical irritation can occur either from the polymer, the residual monomer, the benzoyl peroxide, the Hydroquinone, the pigment or some reaction product. One such product is formaldehyde. Self cure resins release more formaldehyde than heat cure acrylics. Increasing polymer monomer ratio will reduce formaldehyde release. www.indiandentalacademy.com
  114. 114. The residual monomer content of0.5% is the component singled out as an irritant. But it is found that the free monomer of the surface of the denture is leached out within 17 hours. The remainder of the monomer is not readily extracted even if so it washes away very rapidly. So if residual monomer were the cause its effect is expected to appear rapidly. But most of the cases reported occur after months or years. Careful clinical evaluation revealed that either unhygienic conditions under the denture or ill fitting denture that is traumatizing the tissue are the causative factors. www.indiandentalacademy.com
  115. 115. A true allergy to acrylic resin can be carried out by a patch test. The residual monomer can be reduced by processing heat cured acrylic for 7 hours at 70 c followed by boiling for 1 hour. Direct contact of the monomer over a continuing period can cause dermatitis. So dentist or dental technicians should refrain from handling the acrylic resin dough with the hands. www.indiandentalacademy.com
  116. 116. Inhalation of the monomer vapor can produce toxic reaction. So use of the monomer should be restricted to well ventilated areas. The plasticizer phthalates can produce dermatitis www.indiandentalacademy.com
  117. 117. Growth of Candida albicans on the surfaces of acrylic resin is a concern for patients. This can be avoided by treating with nystatin or chlorhexidine gluconate. In addition to Candida other microorganisms such as streptococcus oralis, Bacteriodes gingivalis, Bacteriodes intermedius and streptococcus sanguis also adhere to acrylic resin bases especially on rough surfaces www.indiandentalacademy.com
  118. 118. BARDAY S.C and FORSYTH. A published a case report on BDJ 1999 October in which they have seen that the colouring agents added to acrylic resin can cause hypersensitivity reactions. www.indiandentalacademy.com
  119. 119. Infection control Care should be taken to prevent cross contamination between patients and dental personnel. They should be disinfected after constructed,after adjustments and before leaving the clinic. Appliances can be sprayed before they leave the operatory. Ethylene oxide gas is a suitable method for sterilization. Other materials such as glutaraldehyde 2% and 5% phenol can also be used. As these materials absorb liquids their use is not widely recommended. www.indiandentalacademy.com
  120. 120. SHENEE and JAVID conducted a study to find out the effect of disinfectants on acrylic resins and they concluded that Glutaraldehyde does not affect the flexural strength and surface morphology of acrylic resins. But if acrylic resins were immersed in phenolic compounds for more than 12 hours pitting on the surface of acrylic resin may occur. www.indiandentalacademy.com
  121. 121. In an another study conducted by Watkinson A.C which appeared on J. PROST DENT 1992 July he found that transverse strength of acrylic resin is affected by alcohol based disinfectants. www.indiandentalacademy.com
  122. 122. Acrylic Resin Cleansers The most common cleansers used are the immersion type which includes, alkaline compounds, detergents flavouring agents, and sodium per borate. Sodium hypochlorite can effectively remove certain type of stains. But they are not preferred to use with metals. Tooth brush has very little effect on the surface of the resin. Salt, soap, soda and most common dentifrices can also be used. But their prolonged use may affect the fit and makes the surface rough which is difficult to maintain clean. www.indiandentalacademy.com
  123. 123. Property Poly(methyl methacrylates) Density (g/cc) Polymerization shrinkage (% by volume) Dimensional stability Water sorption (mg/cm2; ADA Test) Water solubility (mg/cm2) Resistance to weak acids Resistance to weak bases Effect of organic solvents Processing ease Adhesion to metal and porcelain Adhesion to acrylics Colorability Color stability Taste or odor Tissue compatibility Shelf life 1.16-1.18 6 Good 0.69 0.02 Good Good Soluble in ketones, esters, and aromatic and chlorinated hydrocarbons Good Poor Good Good Yellows very slightly None Good Powder and liquid, good; gel, fair www.indiandentalacademy.com
  124. 124. USES IN ORTHODONTICS Chemically activated acrylic resins are mainly used in orthodontics. The accuracy of fit and convenience of molding without the necessity of flasking make this material is useful to the specialty of orthodontics. For the construction of removable and functional appliances. For making impression trays. For the fabrication of occlusal splints temporary space maintainers For the fabrication of extraoral chin caps. Bonding materials In Stereolithography www.indiandentalacademy.com
  125. 125. Acrylics for bonding Acrylic resins were the first material to be used as orthodontic adhesive. The acrylic resins used for bonding can be classified as: (a) Acrylic based systems – PMMA systems (b) Diacrylate systems – BISGMA systems www.indiandentalacademy.com
  126. 126. The Acrylic resins are (e.g., Orthomite, Genie) are based on self curing acrylics and consists of methyl methacrylate monomer and ultra fine powder. This was introduced into orthodontics by Miura et al in 1970 when he described an acrylic resin orthomite using a modified trialkyl borane catalyst that proved to be particularly successful for bonding plastic brackets and for enhanced adhesion in the presence of moisture. Acrylic resins possess good flow and wettability but lack sufficient bond strength. High degree of polymerization shrinkage and great difference in linear coefficient of thermal expansion between tooth and resin further affect bond strength. www.indiandentalacademy.com
  127. 127. Most diacrylate resins are based on the acrylic modified BISGMA or Bowen’s resin. A fundamental difference is that the resins of the acrylic system form linear polymers only those of the diacrylate system can be polymerized by cross linking into a 3-D network. www.indiandentalacademy.com
  128. 128. The diacrylate resins have the best physical properties and are the strongest adhesives for metal brackets. Buzzitta et al found that a highly filled diacrylate resins with large filler particles gave the highest values of in vitro bond strength for metal brackets. The clinical implication is that adhesives with large particle fillers are recommended for extra bond strength but careful removal of the excess is mandatory because such adhesives accumulate plaque more easily. www.indiandentalacademy.com
  129. 129. Diacrylate resins do not bond with plastic brackets. Either an acrylic monomer as a primer to enhance bonding between the diacrylate resin and the polycarbonate bracket is necessary or an acrylic resin adhesive must be used. Acrylic or combination resins have been most successful with plastic brackets. www.indiandentalacademy.com
  130. 130. Other alternatives to chemically autopolymerizing paste-paste systems.: No-mix adhesives: These materials set (e.g., Rely a bond) when paste under light pressure is brought together with a primer fluid on the etched enamel or bracket backing or when another paste on the tooth is to be bonded. Curing occurs within 30 - 60 seconds. www.indiandentalacademy.com
  131. 131. Visible light polymerized adhesives These materials (e.g., Transbond) may be cured by transmitting light through tooth structure and ceramic brackets. Light activated resins are now preferred in some cases because of the ease of processing and elimination of methyl methacrylate monomers. www.indiandentalacademy.com
  132. 132. Stereolithography This technology uses a laser to cross link specific areas as a pool of acrylic is being filled. Polymerization occurs only in the areas the laser activates. This technology has been used to produce copies of dental models and models of craniofacial complex to visualize and plan difficult surgeries. www.indiandentalacademy.com
  133. 133. Newer advances in acrylic Resin (1) High impact strength materials These materials are butadiene-styrene rubber – reinforced poly methyl methacrylate. The rubber particles are grafted to methyl methacrylate so that they will bond to the heat polymerized acrylic matrix. These materials are supplied in a powder – liquid form and are processed in the same way as other heat- accelerated methyl methacrylate materials. www.indiandentalacademy.com
  134. 134. Indicated for patients who drop their dentures repeatedly, e.g. senility, parkinsonism www.indiandentalacademy.com
  135. 135. (2) Vacuum adapted plates A quick and easy method of making a usable base plate is to vaccum mold a sheet of thermoplastic resin (eg: acrylic, polycarbonate, polyvinyl acetate thickness control and good adaption to the cast particularly when using thinner sheets. More intimate adaptation is obtained compared to manual adaptation. www.indiandentalacademy.com
  136. 136. (3) Rapid heat polymerized Resin These are hybrid acrylics that are polymerized in boiling water immediately after being packed into the flask. After being placed in boiling water, the water is brought back to full boil for 20 min. (reverse cure). After the usual bench cooling to room temperature the denture is deflasked. The initiation is formulated from both chemical and heat activated initiators to allow rapid polymerization without porosity. www.indiandentalacademy.com
  137. 137. (4) Carbon Fiber and polyaramid reinforcement of acrylic resins Early experiments with glass fiber have resulted in failure because of the irritant nature of the fibers .Carbon fibers have no such irritancy and greatly increased impact strength and flexural stiffness of the denture base. But the black colour of carbon fiber and the potential toxicity at coupling agents silane 174 prevent their use for reinforcement of acrylic resins. Their use is restricted only to lingual aspects of denture. Eg: Polyethylene, Graphite www.indiandentalacademy.com
  138. 138. Polyaramid or Kevlar fibres (poly p Phenylene terephthalmide) have stiffness of 90 GPa straw coloured and greatly enhance the mechanical properties of the denture. They do not require treatment with coupling agent. Their soft yellow colour is masked by the pink resin. www.indiandentalacademy.com
  139. 139. ACRYLIC RESIN introduced into Dentistry about 70 years back. After its introduction into dentistry it has revolutionized the way we are practicing Dentistry. Many new materials were introduced into Dental profession after that like epoxy resin, poly styrene and poly urethane etc. to name a few . It has some disadvantages in the form of water absorption, low abrasion resistance low colour stability etc. But it still remains as one of the main stay materials used in dentistry for making bases, removable appliances, obturators crown and bridge material etc. www.indiandentalacademy.com
  140. 140. Bonding adhesive Ideal requirement 1.nontoxic 2.polymerize at or near body temperature with minimal shrinkage 3.minimal expansion & water sorption 4.produce lasting bond www.indiandentalacademy.com
  141. 141. 5.strong-resist masticatory forces and forces applied during orthodontic treatment 6.Strain resistant 7.easy to use ,less time consuming 8.sufficient working time www.indiandentalacademy.com
  142. 142. 9.no additional equipment 10.option of bonding directly or indirectly 11.easy correction of shy spot 12.easy replacement of base bond www.indiandentalacademy.com
  143. 143. Types/classification A.based on the bonding system type: acrylic base system- poly methyl methacrylate diacrylate system- bis-gma system glass inomer systems-chemical cure light cure dual cure www.indiandentalacademy.com
  144. 144. Based on flouride content: Flouride realising system Non flouride releasing systems www.indiandentalacademy.com
  145. 145. Based on curing system: Self curing system Light curing system Dual curing system www.indiandentalacademy.com
  146. 146. Based on the filler content: Lowly filled bonding systems Highly filled bonding systems www.indiandentalacademy.com
  147. 147. Composites Mixture of 2 or more components Hard inorganic filler particle + Soft organic dimethacrylate polymer Bone a natural composite www.indiandentalacademy.com
  148. 148. Dr.Raphel Bowen:1960 Have the following major components: organic resin matrix inorganic filler coupling agent initiator-accelerator system pigments www.indiandentalacademy.com
  149. 149. Composition & strct Resin matrix Composed of mainly monomers & comonomer Monomers of mol wt 100-1000g/mol bis-GMA & UDEMA common monomers TEGDMA- comonomer,diluent to control viscosity C=C functional grp(difunctional monomer) www.indiandentalacademy.com
  150. 150. Polymerization activated by chemical,light,dual cure Bis-GMA molecule: 2 reactive C=C grps crosslinking strength -OH grps cross linking www.indiandentalacademy.com
  151. 151. www.indiandentalacademy.com
  152. 152. Properties of bis-GMA: Higher mol wtg than MMA polymerization shrinkage High mol wtg viscosity TEGDMA,EDMA,MMA viscosity www.indiandentalacademy.com
  153. 153. TEGDMA= DILUENTS Viscosity Polymerization shrinkage So delicate balance maintained www.indiandentalacademy.com
  154. 154. Clinical significance: High conc of acrylate/MA grps remain unreacted after setting as: 1.large size 2.rapid increase in viscosity during setting www.indiandentalacademy.com
  155. 155. Benificial properties contributed by the resin: 1.molded at ambient temperature 2.sets by polymerization in short time Drawbacks of matrix: Weakest phase Least wear resistant Water sorption Stain,discolor www.indiandentalacademy.com
  156. 156. Disadvantages of resins without filler: Low MOE Flexibility marginal breakdown Low compressive strength & hardness poor durability Setting contarction 6% by vol wear resistance High COTE marginal breakdown www.indiandentalacademy.com
  157. 157. Biological properties Residual monomer MMA-irritant to pulp Temperature rise –exothermic setting www.indiandentalacademy.com
  158. 158. Filler: Inorganic content(ceramic) Advantages: Polymerization shrinkage COTE closer to that of tooth Water absorption Abrasion resistance Mech. Prop.-tensile st.compressive st,MOE,rigidity,hardness www.indiandentalacademy.com
  159. 159. Uses: Quartz filler:natural,inert(chemically stable),strong,hardness difficult polish abrasion of opposite tooth www.indiandentalacademy.com
  160. 160. Glass –fine sized particles -barium,lithium aluminium silicate -borosilicate glasses,strontium,zinc glasses Colloidal silica particles: in microfine composites www.indiandentalacademy.com
  161. 161. www.indiandentalacademy.com
  162. 162. Physical properties of the composite depend on the filler quantity.maximum amt of filler incorporated by: 1.selecting filler particles of different sizes 2.irregular shaped particles(less dislodge) 3.filler with large surface area eg:colloidal silica But viscosity so small amt added 4.limit to the filler added,all filler should be wetted by monomer,else voids stress conc. www.indiandentalacademy.com
  163. 163. Type Concentration Particle size Particle size distribution -of the filler decide the properties of composite Trend of filler particle selection from strongest to softer www.indiandentalacademy.com
  164. 164. Coupling agent: To improve properties filler(inorg. Phase) should be bonded to resin matrix(organic phase) This bond achieved by a silane coupling agent-methacryloxypropyl trimethoxysilane www.indiandentalacademy.com
  165. 165. Functions of coupling agent: 1. To physical,mechanical prop. 2. To retention of filler particles abrasion resistance 3. Stress distribution under function 4. Prevents water penetration b/t resin matrix & filler www.indiandentalacademy.com
  166. 166. Mode of action of the coupling agent: Silane molecule has reactive grps at both ends Reacts with the resin matrix at one end ceramic filler at the other end www.indiandentalacademy.com
  167. 167. www.indiandentalacademy.com
  168. 168. www.indiandentalacademy.com
  169. 169. SCOTHBOND Coupling agent that is not a silane Composed of halophosphorus ester of bis- GMA,TEGDMA,benzoyl peroxide and an aryl sulfinate salt Long chain of molecules- one end bond to tooth ,other to resin Shear bond strength of etched enamel by 86% www.indiandentalacademy.com
  170. 170. Initiator & activator: 1.chemical cure-amine+BPO R* BPO-initiator tertiary amine-activator 2.visible light cure: photoinitiator+activator campharoquinone+amine (0.2-1%) 3.inhibitors:hydroquinone(0.1%) www.indiandentalacademy.com
  171. 171. Pigments----for shades Uv light absorber---to minimize color change by oxidation www.indiandentalacademy.com
  172. 172. Classification of composites Based on ADA specification no.27 Based on filler Based on the method of polymerization www.indiandentalacademy.com
  173. 173. 1.As per the ADA specification no.27 classified into 2 types and 3 classes: type 1-polymer based materials suitable for restoration involving occlusal surface type 2-other polymer based materials www.indiandentalacademy.com
  174. 174. 3 classes: class1 - self cure materials class 2 – light cure material class 3 – dual cure material www.indiandentalacademy.com
  175. 175. Classifacation based on fillers: Macrofilled composite Microfilled composite Small particle composite Hybrid composite www.indiandentalacademy.com
  176. 176. www.indiandentalacademy.com
  177. 177. A.Macrofilled( traditional) composites: first type of dental composite(1960) quartz /glass filler(10-50um) 60-80% by weight Since fillers are denser than the resin phase,the vol % is 10-15% lower than weight% www.indiandentalacademy.com
  178. 178. Disadvantages: 1. Polishability 2. Poor surface finish(dull appearance) 3. Rough finish-plaque retention 4. Staining Precaution-mix of chemical cure-no metal spatula www.indiandentalacademy.com
  179. 179. Uses: 1. Some orthodontists still prefer,as rough feel allows easy detection after debonding 2. Class lll,lV 3. Class v 4. Limited in class l & ll (wear) www.indiandentalacademy.com
  180. 180. Microfilled resins(late 1970s): Enhanced polishability & esthetics over traditional composites Submicron particles(colloidal silica)- 0.03-0.5um 20-50 wt% 35-60 vol% www.indiandentalacademy.com
  181. 181. Limitation: Small particle size high surface area(100-300m²/g) so not possible to incorporate very high filler loading detrimental effect on strength & stiffness www.indiandentalacademy.com
  182. 182. Advantage: Smooth,lustrous surface finish Disadvantage: High resin content COTE High resin content strength www.indiandentalacademy.com
  183. 183. Uses of microfilled composites: 1. Where esthetics is dominant concern 2. Class lV 3. Veneers,to add translucency to core buildup 4. Class V www.indiandentalacademy.com
  184. 184. SMALL PARTICLE COPMOSITES: 1980s Filler size:avg-1-5um(range;0.5-10um) 80-85 wt% 60-77 vol% Advantage: Best physical properties Surface is not rough as macro filled but not as smooth as microfilled Uses: Classl, class ll www.indiandentalacademy.com
  185. 185. Hybrid or blend composites(late1980s): Esthetics + durability Blend of conventional glass & quartz particles(75%)(1-50u) + submicron silica(8%)(0.04u) Advantage: Strong Polishable Use: Small- medium class l, ll Class lll,lV www.indiandentalacademy.com
  186. 186. Method of activation A.Chemical cure Tertiary amine(0.5%)+BPO(1%) Early self cures –2pastes Short working time:inhibitor destroys R* for a short period of time Other systems: Paste/paste system Powder/liquid system-powder containing filler &peroxide initiator,liq containg monomer,activator Paste/liquid system,encapsulated materials www.indiandentalacademy.com
  187. 187. Disadvantage: air entrapment during mixing Limited working time Setting characteristics: Begins immedeately after mixing Gradual in viscosity Setting time 3-5mt Rate of setting uniform through out the material thickness www.indiandentalacademy.com
  188. 188. Material should not be disrupted once the initial setting period start /working time is over disrupts polymerization Desirable to place plastic matix strips during cure to prevent o2 inhibition www.indiandentalacademy.com
  189. 189. Light cured composites visible light cure uv light (blue light cure) Supplied as a sinlge paste Contain monomer,comonomers,filler,initiator which is unstable in presence of uv/visible light of high intensity www.indiandentalacademy.com
  190. 190. Uv light cure: 360-400nm wavelength Initiator-benzoyl methyl ether Advantage: Unlimited working time Set on comand Disadvantage: Retinal damage,unpigmented oral tissue Limited depth of cure Intensity of the uv light cure system with time www.indiandentalacademy.com
  191. 191. Visible light cure: 400-500nm;greatest intensity arnd 480nm Initiator system=diketone+amine (campharoquinone) Advantage: 1. No chair side mix,so no air entrapment 2. Paste is thicker with more filler ,less matrix so stronger than CC 3. Working time under dentist control 4. Intensity of VL remains same over time 5. Safe for operator www.indiandentalacademy.com
  192. 192. www.indiandentalacademy.com
  193. 193. Setting characteristics: 75% of polymerization takes place in 1st 10mt ,though curing continues for >24hr Longer working time Very little in viscosity before exposure to light High rate of polymerization Command setting:10-40sec exposure Setting first achieved in the surface layer where light intensity greatest www.indiandentalacademy.com
  194. 194. Depth of cure-2-3mm(VLC) 1.5-2mm(UVLC) Factors affecting depth of cure: 1. Type of composite: with darker shade penetration Microfilled composites-longer exposure time(smaller & more numerous filler particles ,scatter more light than hybrid composite with larger & fewer glass particles) www.indiandentalacademy.com
  195. 195. 2.Quanlity of light source: 480 nm check quality at regular intervals 3.Method used: Distance:light intensity on unit surface area drops off with the inverse square of the distance b/t light source & resin distance kept minimum. light tip should not be contaminated with composites Exposure time(20-60s) recommended Light conducting wedges & transperent matrices(MOD) restoration www.indiandentalacademy.com
  196. 196. Avoid curing to >2mm fundamental rule Cure for atleast 40sec Compatibility of light source: Polymerization reaction of composite materials in exothermic in nature Pulpal damage Rise in temp for VLC>CC www.indiandentalacademy.com
  197. 197. 1.heat of polymerization in VLC is liberated over a small period of time 2.heating effect of the light activation unit. To reduce the effect of light cure units, filters are added which remove the hotter parts (red part of the spectrum), so the light appears blue www.indiandentalacademy.com
  198. 198. Light safety & protection: 1. avoid unnecessary exposure 2. Avoid direct exposure,don’t look direct 3. Use protective eye wear www.indiandentalacademy.com
  199. 199. Light curing units: 2 types presently: Quartz-tungsten-halogen light Plasma arc lights Quartz tungsten halogen light: Peak wavelenght-450-490nm Intensity not uniform for all area of the light tip Intensity with distance from light source Intensity with continuous use Avg life span-50-100hr www.indiandentalacademy.com
  200. 200. www.indiandentalacademy.com
  201. 201. Most units have light source & intraroal tip together & are held by a gun type device with a trigger.separate power source attached to gun by an electrical cord. large amt of heat generated from the bulb during use.for cooling a fan in mounted within the gun. when the bulb overheats, the unit will shut down & be inoperable till bulb cools. www.indiandentalacademy.com
  202. 202. Plasma arc lights: High intensity curing units 380- 500nm,480nm(peak) Light obtained from the electrically conducive gas filled b/t the tungsten electrodes. Advantages: Reduces exposure 10sec Saves time of curing Disadvantge: polymerization shrinkage expensive www.indiandentalacademy.com
  203. 203. Disadvantage: Requires special equipment Precaution: Storage of material away from sunlight Lid replaced immediately www.indiandentalacademy.com
  204. 204. Superiority of VLC over UVLC Faster cure Greater depth of cure Cures through tooth structure and into undercuts No warm up time needed Energy output reasonable constant until bulb burnout Light bulb is rel. inexpensive & simple to replace Safety appears to be less of an issue www.indiandentalacademy.com
  205. 205. Difference b/t CC & LC Light cured Polymerization is always at the surface close to the light source Less wastage of material Curing is done in increments Chemical cured Polymerization is uniform More wastage Curing in one phase www.indiandentalacademy.com
  206. 206. Finish always better Strength is higher Command sets Working time is more No mixing required More color stable More resistant to wear Finish poor Strength lower Sets within 1mt Working time is less mixing is required Less color stable Less resistant to wear www.indiandentalacademy.com
  207. 207. New composites Flowable composites: 1. For cervical lesions,pediatric use 2. <45% filler by vol 3. Low viscosity 4. Easily displaced froma very smalll gauge needle into the cavity directly Advantge: 1. Easy dispensing Disadvantage:weak, wear resistance,low MOE,high polymerization shrinkage www.indiandentalacademy.com
  208. 208. CONDENSABLE COMPOSITE: Filler % similar to hybrid composite Heavy consistency produced by using modified fillers/altering the distribution of particles so that it inb. the sliding of filler particles over one another thicke ,stiffer material Unit dose compules Advantage: Easy to place in cavity Low polymerizatiom shrinkage Radioopacity & wear rate3.5um/yr www.indiandentalacademy.com
  209. 209. Properties Physical properties 1.polymerization shrinkage: is a direct function of the amt of resin present in the composite Composite setting concn-1.5% Effects: marginal adaptation,polymerizaton stresses(10-15Mpa) strain the interfacial bond,postoperative pain www.indiandentalacademy.com
  210. 210. Greater the diluent monomer, greater the ploymerization shrinkage Greater the unpolymerized monomer,greater is the shrinkage Higher the proportion of fillers lower is the shrinkage www.indiandentalacademy.com
  211. 211. Water absorption: Reasons: Glass may be partially dissolved Hydrolytic breakdown of the bond b/t filler and resin Incomplete cure of resin Amt of water absorption depends on: Resin content of composite Quality of the bond b/t resin & composite www.indiandentalacademy.com
  212. 212. Effects of water absorption: 1. Detrimental on color stability 2. Discoloration by oral fluid absorption 3. Poor wear resistance 4. Decrease in surface hardness www.indiandentalacademy.com
  213. 213. 3.solubility: 0.01-0.0mg/cm² Increased if incomplete polymerization Manifested clinically as color instability www.indiandentalacademy.com
  214. 214. 4.coefficient of thermal expansion: Has to be as close to tooth as possible Filler has low COTE Resin has HIGH COTE Mismatch in COTE : 1. Marginal leakage 2. Bond strain 3. Material fatiguewww.indiandentalacademy.com
  215. 215. Mechanical properties 1.Compressive strength: Higher than tensile strength Indicates brittleness VLC=260Mpa CC=210Mpa CC strength is lower because air entrapment during mixing www.indiandentalacademy.com
  216. 216. Microfilled composite have comp. St similar to conventional, but Lower yield stg(point of irretrievable breakdown) Low MOE-will deform under stress www.indiandentalacademy.com
  217. 217. Porosity –incorporated in 2 stages: During incorporation of filler particles into resin During mixing two components www.indiandentalacademy.com
  218. 218. Tensile strength Composites tend to fail under tension But measurement of t.s of brittle materails difficult. As the brittle materials tend to develop internal flaws,surface cracks,t.s judged from surface finish www.indiandentalacademy.com
  219. 219. Modulus of elasticity Measure of stiffness Microfine composites have E ¼-½ of highly filled fine composite,so tend to flex under stress. www.indiandentalacademy.com
  220. 220. 4.Hardness: Good indicator of wear resistance hardness with filler content + degree of polymerization VHN :unfilled resins-18 microfill -30 hybrid -100 KHN:22-80kg/mm² www.indiandentalacademy.com
  221. 221. 5.Wear: Loss of material by interfacial forces when 2 surfaces rub against eash other Types: Abrasive wear Fatigue wear Corrosion wear: hydrolytic breakdown of the resin Breakdown of the resin filler interface Chemical wear-solvents in food,acids LC . Wear resistant ,as porosity CC2-5% porosity,polymerization inhibition www.indiandentalacademy.com
  222. 222. Factors affecting: filler content Small particle wear polymerization Coupling agent Porosity Finish with diamond burs Posterior tooth Wear reduced by: High filler load Smooth surface finish Hydrolytically stable resin, Strong bond b/t filler & resin www.indiandentalacademy.com
  223. 223. 6.Radio opacity: by adding Barium,strontium Color stability: Oxidation of tertiary amine www.indiandentalacademy.com
  224. 224. Biocompatibility The ability of a material to elicit an appropriate biological response in a given application in the body. When closely seen this def includes interaction b/t host,material and an expected function of the material. www.indiandentalacademy.com
  225. 225. 2 key factors relevant when discussing biological effect of a material: 1.Whether material releases any of its components 2.Whether the released components have any relevant biological effect www.indiandentalacademy.com
  226. 226. In practice polymerization is not complete and small amt of starting products are released. There is no doubt that the cured dental resin releases components into the body. Early test showed a short lived release(48hr) By HPLC several week to months of release was seen. There is a large reservoir of uncured monomer inside the cured bulk www.indiandentalacademy.com
  227. 227. Dental resin releases bis-GMA, TEG-DMA and others Controversy regarding the estrogenicity of dental resin started froma single article by Olea etal 1996-some dental sealants released at a signf. Conc. In saliva Bisphenol A was a plausible Xenoestrogen in the body Xenoestrogen-a chemical,not indigenous to the body that acts in the body in a manner similar to that of estrogen. www.indiandentalacademy.com
  228. 228. www.indiandentalacademy.com
  229. 229. Relevance: Release of components a necessary factor,but not sufficient event to cause adverse effect Biological effect depends on form,conc., location BPA is weakly estrogenic in a culture of sensitised cells but invivo action not clear www.indiandentalacademy.com
  230. 230. First generation bonding adhesives Unfilled acrylic resins & epoxy resins 1st bonding adhesives used in orthodontics unfilled poly(methyl methacrylate) Powder/liquid OR paste/paste www.indiandentalacademy.com
  231. 231. 2 types of induction mechanism: A)benzoyl-peroxide—tertiary amine B)sulfinate system: p-toulene sulfinic acid(accelerator or co- catalyst) as salts incorporated in powder. sulfinate salts sulfinic acid R* www.indiandentalacademy.com
  232. 232. DISADVANTAGE OF UNFILLED RESINS: Low hardness & strength High co-efficient of thermal expansion Lack of adhesion to tooth structure High polymerization shrinkage Eg:Bracket bond Genei www.indiandentalacademy.com
  233. 233. EPOXY RESINS Large no. of dental products that were epoxy resins were developed esp bis-GMA,an aromatic ester of a dimethacrylate,synthesized from an epoxy resin(ethlene glycol of bis-phenolA) & methyl methacrylate Disadvantages: Lack color stability Water absorption Patient sensitivity www.indiandentalacademy.com
  234. 234. b)second generation: Uv light activated resins Provided greater bond strength Used bowen’s hybrid molecule-the back bone similar to epoxy resin,but functional reactive grps are acrylic Esters of alkyl benzoin to facilitate UVL activation www.indiandentalacademy.com
  235. 235. Advantages: Higher bond strength then 1st gen Low polymerization shrinkage Greater hardness Low water absorption Disadvantage: Uv light In indirect technique,a tray carrier neede to position the brackets,this interfered with access to the resin beneath the brackets & made cleaning difficult www.indiandentalacademy.com
  236. 236. Third generation(filled resins) Late (1970s) Filled resins with high % of inert filler,2 paste system Improved thermal expansion property Macrofilled(10-30um)eg:Consice Microfilled(0.20.3um) eg:Endure,DynaBond www.indiandentalacademy.com
  237. 237. COMPOSITION : David Russel Barn etal combination of six- stranded wire & concise will provide optimum performance in bonded fixed retainers.1mm thickness gives optimum strength with min. bulk Advantage over NO-MIX adhesives: High bond strength More homogeneous & perdictable mix Short snap time-possible to ligate archwires sooner(4 handed approach to bonding recommended to help mix 2 paste system) www.indiandentalacademy.com
  238. 238. 1 to 1 bonding: 2 paste self cure adhesive system Extra small quartz particles-smooth mix,no stick to spatula Simple 1:1 mixing ratio of sealant paste & bonding paste Work time-1½mt, by cooling paste/slab www.indiandentalacademy.com
  239. 239. Eliminates bracket drift Reduces decalcification due to feather edge on the tooth surface Recommended when close adaptation b/t tooth surfaces & bonding pads is not possible,in lingual bonding brackets,retainer www.indiandentalacademy.com
  240. 240. EXTEND-a-BOND: Highly filled ,self polymerizing 2 pase system Low viscosity psate,small particle fillers Longer working time Use: With bondable retainers Indirect bonding www.indiandentalacademy.com
  241. 241. 4th generation: No –mix adhesives(1980s) Composite placed on the tooth surface in unpolymerized form Polymerization catalyst on back of brackets Artun & zachrison-mutagenic potential of unreacted monomer?;;arch wire cant be engaged with min of delay Eg:Monolok,Unite Ching etal-static load like tying archwire can be placed without significant In bond strg www.indiandentalacademy.com
  242. 242. ―Right-on‖ No mix adhesives: Most advanced self curing bonding system available Superior bond strength Drift proof bracket placement 2yr shelf life without refrigeration Adhesive paste preloaded in syringes Thin coat of activator/sealant liq is brushed on bracket base & prepared tooth surface.place small amt paste on bracket base,bracket pressed on tooth Arch wire 7min after last bond www.indiandentalacademy.com
  243. 243. 5th generation: Visible light cure orthodontic adhesive Douglas etal Single paste system:ketone+amine 470nm λof light TRANSBOND,HELIOSIT Wang &Meng-VLC for metal bracket(0.75- 2.1mm) suggested cure for 40-60sec, bond strength( cross linking) www.indiandentalacademy.com
  244. 244. Hugo.R.Armas Galindo etal: Failure rates with VLC=11.3% CC=12% Trans Bond XT: Leading light cured orthodontic adhesive Instruction to cure both mesial & distal of incisal or gingival surfaces of metal brackets for 10sec each,total 20s Immedeate arch wire insertion For ceramic brackets,the light guide placed approx. 2mm away from from the bracket face & shine through the ceramic bracket for 10s www.indiandentalacademy.com
  245. 245. Greenlaw etal: 1hr bond strength of VLC system 26% of 30hr bond strg Enamel loss with debonding & cleanup ½ of with CC heavy fill resin. Helvatjoglou & colleagues: Continued hardening progressive cross- linking or polymerization (10mt-12 months) Larry colleagues: By extending setting time 5mt 20% increase in bond strength,20-30 mt additional 7-8% additional,so wait for 5mt befor archwire placement.40s curing time,20 for mesial, 20 for distal for Max. shear strg. www.indiandentalacademy.com
  246. 246. Rashid Ahmed Chamda-compared bond strength achieved with LC bonding system & CC over 24hr at 10mt,60mt,24hr found no sign diff in bond strg Advantages of TransBond XT LC ADHESIVE Extended working time allows precise bracket placement Immediate bond strength,allowing immediate archwire placement Saves time for rebonds Efficient bonding of ceramic & metal brackets Excellent handling properties: No bracket drift Easy flash clean up www.indiandentalacademy.com
  247. 247. Adhesion boosters/hydrophilic bonding systems Failure of orthodontic bonded attachments & brackets is mainly due to contamination..moisture..saliva To overcome this PRIMERS/COUPLING AGENTS/DENTINE CONDITIONERS were introduced www.indiandentalacademy.com
  248. 248. Primers Hydrophilic monomers carried in a solvent,acetone,ethanol water or water Solvents displace the water in the dentinal tubules and in the process pull the resin adhesive into the dentin www.indiandentalacademy.com
  249. 249. www.indiandentalacademy.com
  250. 250. Coupling agents make the dentin surface more hydrophobic wetting by momomer No shrinkage of resin tags away from the dentin www.indiandentalacademy.com
  251. 251. Bonding agents 1st generation Late 1956-Buonocore-GPDM containing resin(glycerophosphoric acid-dimethacrylate) 1965-Bowen-NPG-GMA(N-phenyl glycine) & glycidyl methacrylate Bifunctional molecule i.e, one end bonds to dentin,other end bonds to composite resin www.indiandentalacademy.com
  252. 252. Bonding mechanism: chelation to Ca++ in the hydroxyapatite Ignored the smear layer Bond strength- 1-3Mpa Drawbacks: Debonding Postopterative sensitivity Eg:Cervident(S.S White) www.indiandentalacademy.com
  253. 253. 2nd generation Late 1970,early 80’s 1978 1st product-Clearfil bond system Bonding mechanism: surface wetting phenomenon Ion interaction of phosphate grp & ca++ Smear layer intact www.indiandentalacademy.com
  254. 254. Content : Polymerizable phosphates added to bis-GMA resins(phosphate bonding systems) 3 types: Phosphate ester based Poly urethane based Etched tubule type Bond strength 2-8Mpa Examples-scotch Bond,Clearfil,Bondlite,Creation Bond,Prisma universal bond www.indiandentalacademy.com
  255. 255. 3rd generation(late1980) Smear layer either modified/partially removed 2 imp changes: Use of dentin conditioning Use of hydrophilic monomer Multistep procedure www.indiandentalacademy.com
  256. 256. Clinical steps: Selective etching of enamel conditioner 10%H3PO4 Dentine conditioning 2% NITRIC EDTA,maleic Intermediate primer application- HEMA,4-META Bonding agent/adhesive-unfilled/partially fill- HEMA bond st=8-9Mpa Eg:Mirage Bond,Scotch Bond 2,Prima universal bond 2&4 www.indiandentalacademy.com
  257. 257. 4th generation:early1980 Transformed dentistry total smear layer removal Total etch concept- Takao fusayama(1979) (40% H3PO4 both E & D) 1991,accepted in US- KANACA-Moist Dentine bonding-10% H3PO4 www.indiandentalacademy.com
  258. 258. HYBRIDIZATION-replacement of HA & H2O in the surface dentine by resin) Resin +remaining dentine=hybrid layer Bond strength:17-25Mpa Also called- total etch multi bottle adhesives 3 step etch & rinse adhesive 3 clinical steps:etching-phosphoric acid priming-hydrophilic monomer bonding-unfilled resin www.indiandentalacademy.com
  259. 259. 4-META product: ORTHOMITE SUPERBOND 4META/MMA-TBB System: 10-3 Etch-10%citric acid 3% Fe3Cl META-MMA: methacryloyloxyethyl trimellitate anhydride Methylmethacrylate TBB:tri-n-butyl borane www.indiandentalacademy.com
  260. 260. Bond strength:17-25Mpa Eg:All bond2(Bisco) Scotch Bond Multipurpose(3M) Prime & bond www.indiandentalacademy.com
  261. 261. 5th generation TOTAL SMEAR LAYER REMOVAL TOTAL ETCH CONCEPT 2 STEP system: etching priming+bonding www.indiandentalacademy.com
  262. 262. As primer + bonding adhesive together in 1 bottle=ONE BOTTLE ADHESIVES 2STEP ETCH & RINSE ADHESIVES Rely on hybridization to achieve bond strength BOND STRENGTH:25-28Mpa Window of oppurtunity for optimal adhesiondepends on keeping the demineralized collegen intact www.indiandentalacademy.com
  263. 263. Contents=PHOSHORIC ACID+PENTA EG:One step,Single Bond(3M) www.indiandentalacademy.com
  264. 264. PENTA Multifunctional phosphate based molecule Dipentaerythrytol pente acrylate phosphoric acid ester Weakly acidic Per molecule contains: Phosphate grp-etch enamel & dentin 5 acrylate grps- reactivity,cross linking ability www.indiandentalacademy.com
  265. 265. Prime & bond NT Etchant-34% or 36%H3PO4 Primer adhesive:PENTA,UDMA elastomeric resins T-resis(cross linkin) D resins(hydrophilic) photoinitiator- 4 ethyldimethylamonibenzoate, Silane nanofiller,acetone,butylate hydroxytoulene,stabilizers www.indiandentalacademy.com
  266. 266. 6th generation One step bonding No etch , no rinse,no cure Self etching primer+bonding adhesive 2 types-mix(etchant & primer mixed) no mix www.indiandentalacademy.com
  267. 267. 2 clinical steps clubbed--- etching + priming By the use of acidic primer(self etching primer)these are not rinsed off Less technique sensitive.no problem rel to dentine wetness or dryness+depth of etching does not exceed the depth of the primer infiltration,no nanoleakage Acid treatment of dentin is self limiting & the etch by-products are incorporated into the dental-restorative interface pemanently www.indiandentalacademy.com
  268. 268. Eg: Promt-L-Pop(ESPE,Germany) Unit dose system in blister pack Etchant,primer,adhesive,microbrush sealed in a triple lollipop shaped aluminium package www.indiandentalacademy.com
  269. 269. Red blister-initiator,stabilizer,MA phosphate esters Yellow blister-stabilizer,H2O,Flouride complex Green blister –microbrush tip www.indiandentalacademy.com
  270. 270. 7th generation ALL IN ONE ADHESIVE Etchant+primer+adhesive in one solution Also called:All in one self priming adhesive/Single solution/Self etching Adhesive Xeno lll,i bond www.indiandentalacademy.com
  271. 271. Resin modified glass ionomer www.indiandentalacademy.com
  272. 272. Hybrid materials have been developed to over come some shortcomings in GICs: Short working time Long setting time,not command set Cracking on desiccation Poor resistance to acid attack Low fracture toughness Low abrasion resistance Initial sensitivity to moisture Low early mechanical strength www.indiandentalacademy.com
  273. 273. www.indiandentalacademy.com
  274. 274. Resin modified GIC light activated chemical cure Advantages: Bond to E & D Flouride release Prolonged working time Command set Improved resistance to dessication Enhanced strength eliminate dry field need www.indiandentalacademy.com
  275. 275. Composition: Ceramic powder:ion leachable powder 70-75% by weight organic matrix-forming molecules Most imp changes : Replacement of water byHEMA-water mixture Incorporation of photoinitiator/chemical initiator Set by acid-base reaction and by free radical addition polymerization which may be light or chemically activated www.indiandentalacademy.com
  276. 276. Powder:fluoro aluminium silicate glass Liquid-copolymer of acrylic acid & nueclic acid HEMA Water Campharoquinone P/L:3:1 Fuji ortho LC www.indiandentalacademy.com
  277. 277. Amount of demineralization adjacent to the bracket is reduced Reduction in strep.mutans & lactobacilli around the brackets www.indiandentalacademy.com
  278. 278. Compomer Composite +ionomer Anhydrous single paste Contents: Powder:aluminium fluorosilicate glass, sodium flouride chemical or light cure initiators www.indiandentalacademy.com
  279. 279. Liquid:polymerizable methacrylate carboxylic acid monomer diacrylate monomer No water,ensures that initial setting accurs by polymerization & this prevents premature settign in container Contain carboylic grp molecule,can undergo acid-base setting reaction Setting mainly by light www.indiandentalacademy.com
  280. 280. Advantages: Excellent esthetics Low solubility High bond strength High fracture toughness Drawbacks: Require bonding agent Flouride release less than GI www.indiandentalacademy.com
  281. 281. Reliance quick cure orthodontic paste Light curing of metal bracket in 6 sec Unique chemistry provides a broader area of sensitivity to blue light for a faster & more complete cure Ideal viscosity,no bracket floatation,easy cleaning,no stringing Flouride release protection www.indiandentalacademy.com
  282. 282. Flouride releasing adhesives Flouride reservoir that does not depend on the patient co-operation Light cure/chemical cure Steck etal - bond strength-flouride incorporated in the resin phase altered the surface tension of the liquid wetting www.indiandentalacademy.com
  283. 283. Flouride release: Most of it in 1st few days /wk with ph Recharging Mark.L.Underwood etal:FR2.5 ortho adhesive: Flouride ion –anion exchange process instead of material dissolution,structural integrity of resin maitained FLOUREVER OBA-85wk;LIGHT BOND-2wk www.indiandentalacademy.com
  284. 284. DUAL CURE RESINS 1980S LIGHT CURE+CHEMICAL CURE Eg:Vivadent Thick,Viva Dent Thin Advantage: Reduced bonding time 20 brackets-6.5mt Completely polymerized in 30s www.indiandentalacademy.com
  285. 285. Allow set by CHEMICAL CURE Visble light cure 30s 10s VLC chemical cure:allows proper placement of bracket www.indiandentalacademy.com
  286. 286. Cyanoacrylate Smart Bond 1991-ethyl cyanoacrylate tested for orthodontic bracket adhesive High tensile strength Polymerization starts only in presence of moisture & pressure www.indiandentalacademy.com
  287. 287. Imp that surfaces to be bonded are close to each other ,as material can’t flow,fill gaps Wilner & Oliver-unsuitable for routine orthodontic practise as bond strength deteriorated after few wks Used to adhere to wet surface where less force is required for short time eg:impacted canine www.indiandentalacademy.com
  288. 288. www.indiandentalacademy.com Thank you For more details please visit www.indiandentalacademy.com

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