Enamel preparation & bonding materials /certified fixed orthodontic courses by Indian dental academy

MATERIALS USED
FOR DIRECT
BONDING AND
ENAMEL
PREPARATION

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INDIAN DENTAL ACADEMY
Leader in continuing dental education


CONTENTS
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INTRODUCTION
HISTORY
TERMINOLOGY
STRUCTURE OF ENAMEL
DIRECT BONDING MATERIAL
COMPOSITES
GLASS IONOMERS
BONDING PROCEDURES
ENAMEL PREPARATIONS
ACID ETCHING
CRYSTAL GROWTH
AIR MICROABRASION
LASER ETCH
SAND BLASTING
REVIEW OF LITERATURE
CONCLUSION.

INTRODUCTION
 Introduction of the acid-etch bonding technique

has led to dramatic changes in the practice of
orthodontics.
 Buonocore ‘ 1955 : demonstrated increased
adhesion by acid pretreatment using 85% H 3
PO4.


Newman : began to apply these findings to
direct bonding of orthodontic attachments.

 PremmiadAbdul WahabGRABER VANS1.jp


INTRODUCTION
 Retief

‘ 1975 : also described an epoxy
resin system designed to with stand
orthodontic forces
 Smith’1968 : introduced Zinc polyacrylate
(Carboxylate) cement, and bracket
bonding and this cement was reported by
Migrahi and Smith in ‘ 1969 .


Miura

etal ‘ 71 : 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
also diacrylate resins , as both sealant
( eg. Nuvaseal) and adhesives were
introduced into orthodontics.


The

most widely used resin, commonly
referred to as “Bowens resin ” or bis
GMA(bispenol a glycicly dimethacrylate), was
designed to improve bond strength and
dimethacrylate was designed to improve bond
strength and increased dimensional stability
by cross linking.


HISTORY OF ADHESIVE
BONDING SYSTEMS
 In

1955 Michael Buonocore was the
first to describe the acid etch technique for
enamel bonding. He reported that the
adhesion of acrylic resins to enamel could
be improved by conditioning the enamel
with a solution of 85% phosphoric acid.


In

1956 R.L. Bowen did the initial work on
bis-GMA resin systems (Known as Bowen’s
formula).
 In 1969 Masuhara introduced
an
orthodontic adhesive called direct bonding
system for enamel. It was one of the first
dental adhesive commercially introduced after
Buonocore proposed the concept of acidetching enamel.

In

1975, Silverstone demonstrated the
variation in the pattern of acid etching of
human dental enamel examined by scanning
electron
microscopy.
The demonstrated
three patterns.
 In 1979 Maijer R. and Smith D.C .
introduced an alternative to acid etching.
They described a new method of bonding that
involves crystal growth on the enamel
surface.

DEVELOPMENT OF AN
ADHESIVE BONDING SYSTEM
Rafael

L.Bowen and W.A. marjenhoff
have reviewed the development of an
adhesion system for bonding dental
composites to dentin and enamel.


 Dr. Michael Buonocore is one of the best

know pioneers in adhesive bonding of
resins to teeth. He found that lightly
etching enamel created a microporous
surface into which direct filling liquid resin
could flow. Polymerise and create a
micromechanical attachment (1955).


Dr.

George Newman , one of Dr.
Buonocore’s
contemporaries
developed
similar methods to bond orthodontic brackets
directly to the enamel of teeth (Newman.
Snyder and Wilson, 1968).


Composites

-

have
some
troublesome
properties even with a maximum proportion
of inorganic filler particles.
They exhibit some polymerization shrinkage.
A stiffness lower than that of the tooth.

 A coefficient of thermal expansion higher

than that of the tooth crown




Most situations involving dental adhesion
really involves adhesive joints. The adhesive
joint is the result of interactions of a layer of
intermediate material, i.e., the adhesive, with
two surfaces (adherends), producing two
adhesive interfaces.


Terminology
 Adhesion

:
is attraction between atoms and
molecules at the surfaces of different
materials when these surfaces are
brought
into contact.
Forces of
adhesion vary in magnitude and are
physical or chemical.




Physical Forces of Adhesion:
are that, account for most adhesive behavior
are essentially electrostatic, involving the attraction
between positive and negative charges. They are
commonly known as Van der Wall’s forces and are
mediated through interaction between dipoles (Keesom
forces), induced dipoles (Debye forces), and nonpolar
dispersion forces related to the polarizability of
molecules (London force).






.

 Chemical

forces of Adhesion : are
the strongest forces of molecular attraction
and are represented largely by ionic and
covalent bonds between atoms. Chemical
bonds produced is strong attachment and
are usually more resistant to disruption by
water than physical bonds.

 Cohesion

: Cohesion is the molecular
attraction due to the same physical forces
involved in adhesion, except that these
forces exist between like molecules
instead of different molecules and are
responsible for holding a material
together


 Adhesive

: In the broadest sense, an
adhesive is a material that unites, joins, or
attaches to itself or other substances by
adhesion.


 Adherend:

The adherend is the surface
to which an adhesive is bonded generally
to a solid surface


 Bonding

agent : In dentistry, the
bonding agent is a thin film of adhesive
applied over a surface. A bonding agent
is best used as a low viscosity material
that easily and readily fills in the
microscopic irregularities in a surface.
 It joins one substance to the other
substance.

 Wetting

: Wetting is a manifestation of
the molecular attractive forces between
materials. When the attractive forces are
strong, an adhesive is more likely to fill in
the microscopic irregularities in an
adherend than if the forces were weak,
other things beings equal.


.

Maximal wetting may be described
as a state in which all of the
interfacial
contacts
possible
between adhesive and adherend
surface have been established. A
rough or porous surface can provide
significantly increased bonding areas
when properly wetted. The contact angle
is considered an observable manifestation
of wetting.

 .CONTACT

ANGLE A zero contact
angle indicates that the molecules of an
adhesive are attracted or pulled toward
the surface of the adherend with equal or
greater force than they are attracted to
themselves.


 Viscosity

: Viscosity is a property of a
fluid material, which essentially defines its
consistency and can influence the contact
angle, wetting and spreading phenomena.


 Mechanical

Retention : Is considered
a form of attachment not dependent on
molecular attraction but rather predicated
on the presence of structural retentive
mechanisms. Structural retention may be
of the gross variety, such as by undercuts,
screws and bolts, or may involve more
subtle mechanisms

 Bonding

: Bonding is a general term that
is used to describe the joining, uniting, or
attaching of adhesives to an adherend. It
is due to the physical or chemical forces of
adhesion, and mechanical retention in
undercuts, pores capillaries, and crevices.


NATURE OF ENAMEL
 It is the hardest

tissue in the human

body.
 It is the only clinically visible mineralized
tissue.
 It does not have the regenerative
capacity that bone and dentin possess.


 Enamel consists of microscopic units

called enamel prisms.
 They represent as key hole shaped or
fish like appearance
 They consist of a head and a tail portion


 PremmiadAbdul Wahabrods.jpg


 Each

prism contains small units called
hydroxyapetite crystals
 The crystals run parallel to the long axis
of the prism in the head region and
gradually become perpendicular as they
approach the tail .


 PremmiadAbdul Wahabenamelcrystals.jpg


 The crystals dissolves

faster if they are
oriented in a perpendicular relationship to
the tooth surface that will be etched (head
region of the prism)


DIRECT BONDING MATERIALS


Composites :
 A Composite material may be defined as a

compound of two or more distinctly
different materials with properties that are
superior or intermediate to those at
individual constituents.


 PremmiadAbdul Wahabcompenents of com


Chemistry of synthetic
resins :
Synthetic resins are often called plastics.
Therefore It is these synthetic resins which impart property of a plastic workability
to the composites.
Now, These synthetic resins are composed of very large molecules. The particular
form and morphology will determine whether the plastic is a fiber, hard rigid
resin, or a rubber like product depending on this structure (we will get the final
rigidity of the composite.


polymerization
 process

in which there occur a series of
chemical reactions by which a polymer is
formed from the monomer is known as
polymerization.


 curing

time would also affect the degree of
polymerization, which is important.
Clinically because the higher the mol. wt.
the greater the stiffness. This stiffness is
an
important.
Clinical
requirement.
(according to PROFFIT.)


Polymerization
.Condensation polymerization.
.Addition polymerization.

 Condensation

polymerization:
Condensation reactions result in
polymerization plus the production of low
molecular weight by products.


Addition polymerization :
 there

is no change in composition during
additionpolymerization.These
macromolecules are formed from smaller.
Units, or monomers, without change in
composition, because the monomer and
the polymer have the same empirical
formulas. The structure of the monomer is
repeated many times in the polymer.

STAGES IN ADDITION
POLYMERIZATION
 Induction

:
To start addition polymerization process,
free radicals must be present. Free
radicals can be generated by activation of
monomer molecules with U.V. Light,
visible light, heat or energy transfer from
another compound that acts a free radical


 This free radical is known as the initiator. Most

commonly employed initiator is benzyl peroxide
which decomposes into 2 free radicals.
 Another term is activator. This activator
activates the initiator of in turn this initiator
initiates the polymerization.


 Thus, the process of polymerization can

be activated in 3 ways.
 - Heat which activates this initiator.
 Chemical – most commonly used is
tertiary amines (self-cure)
 2 are separated, when mixed then
polymerization begins.
 light activated - here photons (of
energy) activate the initiator.

 Thus systems developed with visible light

activated materials having a wave length of
470mm.
 In this system the initiation are camphorquinone
and dimethylaminoethylmethacrylate (DMAEM)
 In this light intensity (therefore check machine)
and distance for light source are important
(therefore keep gun as possible with out
touching)are important.

Propagation.
 Ideally, chains reactions should continue until all

of the monomer has been converted to a
polymer. However, the polymerization reaction
is never complete.


Termination :


Can take place in 2 ways.



Direct couping
Exchange of hydrogen atoms


Inhibition of polymerization.
 Impurities in the monomer, as stated, inhibit

polymerization this impurity can react with the
activated initiator or a growing chain, causing
the inhibition.
 Eg. Hydroquinone is often added as an
inhibitor in the monomer, to prevent
polymerization during storage.
 More importantly the presence of oxygen also
retards the polymerization reaction because
oxygen reacts with the free radicals.
 Therefore we say that air thinning of bonding
resins should be avoided to optimise curing.

Copolymerization :


To custom design the physical properties of a polymer
,two or more chemically different monomers, each with
some desirable property can be combined. The polymer
thus formed is called a copolymer . And its process
formation known as copolymerization , thus the
polymer that would be formed would have properties
intermediate to those of the individual monomers,
depending on each components concentration.


TYPES OF RESINS :
 Acrylic

resins :
These imbibe water, this water tends to
separate the chains and to cause general
softening and loss of strength.
- Methyl methacrylate.
-Supplied as a liquid monomer and a powder
these are mixed to form a dough and then cured
like in fabrication of dentures in prosthodontics.
-However, a volume shrinkage of 21% accurs
during the polymerization of the pure methyl
methacrylate monomer. This is too high.

 Polymethyl

methacrylate .
It is hard resin with a high tensile strength.
It does not discolor, but has a tendency to
absorb water by imbibition.


 Multifunctional

methacrylate

systems.
-These include the bis GMA, TEGDMA and
UEDMA which are used in composites
and will be discussed later.


composition
 Consists

of following components.
 Resin matrix
 Inorganic filler
 Coupling agent.
 Activator - initiator system.
 Inhibitor
 Other additives
 Those to improve color stability
 Pigments

Resin matrix.
 Bis GMA
 UEDMA (Urethane dimethacrylate)
 TEGDMA (Triethylene glycol

dimethacrylate)


 The bis GMA have a high mol. Wt., but are

very viscous at room temperature, the use
of diluent monomers is essential to attain
high filler levels and to use pastes of
clinically usable consistencies. Diluents
are usually TEGDMA However, the
addition Of TEGDMA increases
polymerization shrinkage, a factor that
limits the amount of TEGDMA that can be
used in a composite. Also TEGDMA
increases crosslinking, which makes in
material more resistant to degradation.

Filler Particles




Filler particles commonly used silicon particles of
colloidal size ranging from 0.1 to 100 um. Composites
are often classified on the average size of the major filler
component.
In addition to filler volume, level, the size, the
size distribution index of retraction, radiopacity and
hardness are important in determining the properties and
clinical application of resultant composites to incorporate
maximum amount of filler. It is obvious that if a single
particle, since is used, even with close packing, a space
will exsists between particles consider filling a box with
marbles.

 But on important Aspect of composites used in

orthodontics it its fluidity . It should be fluid
enough. So as to provide adequate micro
mechanical inter locking the fluidity of the
composite depends upon the fluidity of the resin
and amount of filler. As the filler surface area
increase this fluidity decreases. If there is a
large amount of small particle filler then the
surface area of the filler particle increases
therefore we use composites with slightly large
filler particle size.

 In order to ensure acceptable esthetics of a

composite resin, the translucency of the filler
must be similar to that of tooth structure
becoming increasingly important in orthodontics
with the advent of transparent bracket systems.
 The radiopacity it provided by a number of
glasses such as barium, strontium and
zirconium( Barium may leach out in saliva ?)


Coupling agent:






It is important that the filler particles are
bonded to the resin matrix, these allow the
more flexible resin matrix to transfer stresses to
the stiffer filler particles.this bond is provided
by the coupling agent.
The coupling agent, therefore, improves
physical and mechanical properties and
provides hydrolytic stability by presenting water
from penetrating along the filler resin interface.
Organosilanes such as r– methocryloxypropyl
trimethoxy slane.
(MOPTM ) 1s used most commonly. zirconates
may also be used.

Activator initiator system. :
 This would depend on the type of

composite used,
-Chemically or self cured.
-Light cured.


Self cured .
 Here the initiator is

benzyl peroxide .
 While the activator is a
teritiaryamine(N-N dimethyl-Ptoulidine)


Light activated:
 Initially the light activated systems used UV

light .
 however, exposure to light at the correct
wavelength (approx. 468nm) produces an
excited state of the photo initiator and an
interaction with the amine to form free radicals
that initiate addition polymerization.
 The commonly use photo initiator is
comphorginone (C-0 has an absorption range
b/w 400-500 mm that is in the blue region of the
visible light spectrum.

Inhibitors
 To minimize or prevent spontaneous

polymerization of monomers, inhibitors are
added to resin systems. A typical inhibitor
is butylated hydroxytoluene.


Optical modifiers:
 To match the appearance of teeth dental

composites must have visual coloration
(shading) and translucency that can
simulate tooth structure.This is of
importance when using transparent
bracket systems. Shading is achieved by
adding different pigments. These
pigments often consist of metal oxides that
are added in minute amount.

 All Optical modifiers affect the light

transmission ability of a composite, darker
shades and opacifiers should be placed in
thinner layers to optimize polymerization.
It is not of much clinical significance in
orthodontics because we use a very thin
layer of composite. However, it must be
remembered this property may affect the
cure of a bonding agent covered with a
composite layer.

Curing :








The first composites were cured by a chemically
activated polymerization process, called cold curing .
Cold curing is initiated by mixing two pastes.
This had 2 disadvantages ;
The operator had no control of the working time.
During the mixing process, it is almost impossible to
avoid incorporating air bubbles into the mix. Oxygen
present hampers the polymerization.
However, to over come these problems,materials that
required no mixing were developed the light cure
composites, where light is used for the activation of the
initiator system.









Advantages :
Insertion and proper placement of bracket can be
completed before starting curing.
Takes only 40 seconds for curing while self-cure may
take longer.
Also, these are no so sensitive to oxygen inhibition
during polymerization.
Drawbacks :
Tendency to shrink to towards the light source, resulting
in a pull back in areas away for light source.
Complicating factors associated with a light source.





Modern light sources are hand-held devices that contain
the light source. The light source is usually a tungsten
halogen bulb. White light generated by the bulb
passes through a fitter that removes the infrared and
visible spectrum for wavelengths greater than 500nm.
There can be a significant difference in the output for
various manufactured lights. For example, if the light
intensity manufactured by a factor of four then 80-40
seconds may be required for a low intensity light to
achieve the same results as that produced by 20 to 60
second exposure with a high intensity light.
When attempting to polymerize resin through a ceramic
bracket, the exposure time should be 2-3 times longer, to
compensate for the reduction in light intensity.

 PremmiadAbdul Wahabvarying light intensi


 Light sources also generate different light

intensities over time, depending on the
quality of age of the lamp presence of
contamination such as composite material
residue on the light tip, and the composite.
Consequently, the light source should be
checked regularly and the operator should
always place the light tip as close as
possible to the restorative material.

 Composites are now available that combine cold

curing and visible light curing components in the
same material. These are available as two
pastes, one contains benzyl peroxide and the
other a tertiary amine. When the Clinician mixes
the two pastes, and exposes them to light, both
cold curing and light curing are achieved with
the same material. These materials are called
dual – cure materials.

 Polymerization stress initially is relieved by

composite until it reaches the co-called “gel
point” before this point the resin-based
composite is flexible and accommodates to
relieve stress. After this gel point is reached, the
composite changes to an un-yielding state in
which shrinkage stress is transmitted to the tooth
structure. It has been observed that the longer
the pre-gel point time, the less the stress in the
past-gel phase.

 Now a days, high intensity energy out put light

sources such as plasm arc curing lights or
laser curing lights allow a reduction in
polymerization rate. This results in a decrease
of the pre-gel point time and may increase the
shrinkage stress. Another concern is that some
of these light sources presents narrow band of
light emission may not correspond to the
absorption band of the photo initiators, resulting
in an incompletely cured resin. The operator
should be cautious other using these alternate
sources of light to polymerize resin-based
composites.

CLASSIFICATION OF
COMPOSITE
based on the size of the filler particles.
On this basis we have
 Traditional
- 8-12 um
 Small particle
-1-5 um
 Microfilled
-0.04-04um
 Hybrid
- 0.6-1.0um


PROPERTIES OF DIRECT
BONDING RESINS.
 In light cured resins, the working time is that

chosen by the operator Setting and working
times.

The setting times for chemically activated
composite resin ranges from 3-5 minutes. Now
composites are available with setting times of 60
seconds. This short setting time has been
accomplished by control of the concentration of
the initiator and accelerator., and the materials
harden rapidly once they are exposed to curing
light.

.

As mentioned earlier the depth of the cure is
limited and is dependent on several variables
such as material, color, location of light source
and the quality of the light source. The resin
paste should not be dispensed until it is to be
used. Exposure to operatory lights for any
appreciable time can initiate polymerization of
the material, because these lights emit radiation
in the 400-500nm range. About 75% of the
polymerization takes place during first 10
minutes. The curing reaction occurs till about 24
hrs, until when optimum physical properties are
not achieved.

Polymerization shrinkage
 Polymerization shrinkage occurs due to higher

density of the polymer formed.

Due to this polymerization shrinkage creates
tensile stresses at the interface between the
resin and the tooth. These stresses severely
strain the bond create with a low-viscosity
unfilled resin bonding agents against acid
etched enamel at cavity margins and can lead to
marginal leakage and early failure

.

It has been shown that this stress can
exceed the tensile resistance of the
enamel and result in stress resistance of
the enamel and result in stress cracking
and enamel fractures along the bonded
interfaces. This potential for
polymerization shrinkage is even greater
for microfilled resins.

Thermal properties


Coefficient of thermal expansion which
gives us the amount of expansion per unit
increase in the temperature.


 Thermal diffusivity: how fast the heat

spreads within the resin.


WATER SORPTION
 Water sorption is greatly reduced in

composites as compared to acrylic resins
due to the bis-GMA and lower amount of
resin.


SOLUBILITY
 Water

solubility of composites
depends on the resinous matrix
more than the filler. The acrylic
resins had higher solubility than the
current composites. This was
because the amount of residual
monomer remaining


MECHANICAL PROPERTIES
 Plaque

accumulation
 In conventional composites for example,
which the resinous matrix wears out, the
large particles project above the surface.
This causes a roughening and results in
increased plaque accumulation.

The smaller the particle size, the lesser
would he the plaque accumulation.

 Colour

stability
 This has gained importance due to the
advent of transparent bracket systems.
As mentioned color stability would not be
as good due to incomplete polymerization,
due to water sorption and solubility.
Otherwise, resins have observable
change only over a 3 year period, which is
more than sufficient for orthodontic
treatment.

PRESENTATIONS
 These are available as

light cured
self cured composites.


MATERIAL SELECTION.
 According

to Proffit.
 The requirements of a bonding material
are.
 Dimensional stability.
 Adequate fluidity
 Strength
 Easy to use clinically.
 Less plaque accumulation.

GLASS IONOMER
CEMENTS
 Glass lonomer cements are adhesive

tooth colored restorative materials which
were orignially used for restorations of
eroded areas. Now, it has been modified
to allow its use in other areas.


 The name of the cement

is glass ionomer
because, the powder is glass and the
setting reaction and adhesive bonding to
tooth structure is due to ionic bond.


synonyms
 Poly (alkenoate )cement
 GLC (galss lonomer cement)
 ASPA ( alumino silicate polyacrylic acid).


APPLICATION
 Anterior esthetic restorative materials for

class III cavities
 For eroded areas and class V restorations
 As a luting agent
 As liners and bases
 For core build up.
 To a limited extent as pit and fissure
sealant.

CLASSIFICATION
 Type I – For luting
 Type II –

For restorations
 Type III – Liners bases.

(Some authors include Type IV-fissure
sealant, Type V- ortho-dontic cemtns and
Type VI-core build up as part of the
classification).

COMMERCIAL NAMES
 Aquacem, Fugi I – Type I

Chem Fil
 Ketac bond
 Vitra bond


- Type II
- Type III
- Light cure


AVAILABLE AS
 Power/liquid in bottles
 Pre-proportioned power/quid in capsules
 Light cure system
 Powder/distilled

type)

water (water settable


composition
 POWDER

silica
alumina
Al flouride
Ca flouride
Na flouride
Al PO4

 LIQUID:

poly acrylic acid
tartaric acid
water


Setting reaction : :





When the powder & liquid are mixed together,
the acid liquid attacks the glass particles. Thus
calcium, aluminium, sodium and flouride ions
are leached into the aqueous medium , probably
in the form of complexes.
Calcium polysalts form first and later aluminium
polysalts cross link the polynion chains.
The salts hydrate to form a gel matrix, and the
unreacted glass partcles are covered by a silica
gel which arises from removal of cations from
the surface of the particles.


 Adhesion

:

GICs bonds chemically to tooth
structure. The bonding is due to the
reaction between the carboxyl groups of
the polyacids and the calcium in the
enamel.


 Anticariogenic

properties :

Glass ionomer releases flourides and
continue to do so over an extended period
of time.
 In addition due to its adhesive effect they
have the potential for reducing infiltration
of oral fluids at the cement – tooth
interface, thereby preventing secondary
caries.

Resin modified glass ionomer:
 These are relatively new materials having

various names like compomer, resin –
inomers, RMGI, light cured GIC, dual cure
GIC and tricure GIC.


Classification :
 Depending

on which is the
predominant component. These
materials may be classified as ( Mc
Clean et al).
 Resin - modified glass ionomers
cement (RMGI), e.g. Fuji II LC,
Vitremer, Photac fil.
 Poly acid – modified composites
(PMC), e.g. Dyract, Variglass VLC.

Composition :
 The

powder contains.
 Ion leachable glasses (silica,
abumina)
 Photointiators or chemical intiators
or both
 Polymerizable resin.


The liquid contains
 Polyacrylic acid.
 Water.
 Methacrylate monomer
 Hydroxyethyl methacrylate
monomers.


Properties :
 Strength

:
The compressive strength is slightly
lower 105 Mpa when compared to
conventional GIC. The diametral
tensile strength is however, greater
20 Mpa because of the plastic
nature of the resin component.


 Hardness:

The hardness
comparable to
GIC.

40 KHN is
that of conventional


 Adhesion

:
The bonding mechanism to tooth structure
is similar to that of conventional GIC.
Micromechanical retention also plays a
role in the bonding process.


 Anticariogenecity

:
These materials have a significant
anticariogenic effect because of the
fluoride release.


 Esthetics

: They are less
translucent because of the
significant differences in the
refractive index between the resin
matrix and powder particles.


 GIC :- variety

of compositions and
changes in the evolution of glass
ionomers materials.


1) Traditional GIC (lines, bases, cements)
Modified by adding comonomers to
polyacrylic acid small powder particle
size.
2) Metal modified glass ionomer
Miracle mixtures (with Ag alloy admixed
with cement)
Cement particle reinforced.

3) LC GIC (linen, bases)
HEMA added to liquid
component;monomers in liquid modified
with acrylic functional groups.
Other powder particles mixed with
alumino-silicate glass


4) Hybrid (resin modified ) GIC
-Silicate glass of composite substituted for
some of powder component.
-Polymer and other phones added to
powder component .
-HEMA and other monomers added to
liquid component.
-Pre cured GI blended into composites

6) Polyacid – modified resin
composite (component)
cements, restorative filing materials,
cores
-methacrylate monomers which multiply
carboxylic groups; addition of ion
leachable glass (as in a conventional
glass ionomer).

Acid – Etching :
 Objectives

:
1. To remove all debris and pellicle to
increase adaptation of resin.
2.Dissolution of exposed ends of enamel
rods.
3.Create surface irregularities that increase
surface area for increased
bond
strength.

Mechanism :
1.Acid solution affects prismatic structure by
preferential removal of either prism core /
periphery .
 2.Adsorption of highly polar phosphate groups
oil the enamel surface, e the result strong polar
bonding to the acrylic may result.
 3.Removal of old, fully reacted and inert
enamel surface exposing a fresh, reactive
surface more favorable for adhesion.
 Tremendous increase in surface area /
wettability.

EFFECTS OF ACID ETCHING
ON SURFACE ENAME :
 Type

1 Etching pattern :
Prism core material is preferentially
removed, leaving the prism peripheries
relatively intact, resulting in a
“honeycomb” appearance.


 Type

2 Etching Pattern
The peripheral regions of the prisms are
dissolved preferentially, leaving the prism
cores relatively intact resulting in a
“cobblestone” appearance


 PremmiadAbdul WahabGRABER VANS AC


 Type

3 Etching Pattern :
Surface loss occurs without exposing the
underlying enamel prisms. Gwinnett (1971)
demonstrated that this etching pattern is usually
observed at the cervical aspects of teeth where
the enamel prisms do not extend to the surface.
-Denys and Retief (1982) showed however,
that the type 3 etching pattern is not confined o
the cervical regions but is also found on other
aspects of an etched enamel surface.

 PremmiadAbdul WahabACID3.jpg


 . Silverstone

(1974) showed that
etching enamel surfaces with phosphoric
acid resulted in ;
 A superficial etched zone
 Under lying qualitative and quantitative
porous zones.


 PremmiadAbdul Wahabmicromechanical re


The depth of the etched zone or the amount

of the surface enamel removed during the
etching procedure depends on ;
The acid concentration
The duration of etching
The chemical composition of the
surface enamel.


 The surface area of the enamel will increase

upto 2000 times that of its original unetched
surface area.
 4. It creates valleys and depressions and makes
the enamel surface irregular at an average
depth of 25 microns.
 5. Acid etching will expose proteinaceous
organic matrix substance of enamel, which can
add to the restorations retention if it becomes
adequately embedded within the restorative
material.

 . It has been verified that enamel treatment with

phosphoric acid will add to the enamel surface a
highly polar phosphate group, which will
increase the adhesive ability of the enamel
surface.
 Several acidic agents have been evaluated by
various investigators like lactic acid, citric acid,
pyruvic acid Alpha-keto acarboxylic acid other
than the phosphoric acid.

 Brauer

and Termini (1972) reported
that lactic acid, a Monohydroxycarboxyic
acid was an effective adhesion promoter.
 Cadwell and Johannessen (1971)
investigated the possible use of citric acid
as an etching agent. Citric acid solutions
are now being used to condition tooth
surfaces

 Pyruvic acid and a Alpha –

Ketocarboxyolic lead to good bond
strengths when used for etching the
enamel surface.
 Rate of etching of enamel by pyruvic acid
was significantly lower than that with 50%
H3PO4.

The concern about the stability of
pyruvic acid solutions has limited the use
of pyruvic acid as an enamel etchant.

Classification of Adhesion:




Physical bonding
Chemical bonding
Mechanical bonding


REQUIREMENTS FOR
ADHESION


There must be good wetting in order to
produce a good bonding.



the surfaces being joined should to produce
and maintain. Clean surfaces are at a high
energy state and rapidly absorb contaminants
such as the moisture or dust. If the
contaminants are not excluded, the adhesive
interface will be weak.

CLINICAL FACTORS
AFFECTING ADHESION







Salivary and/or blood contamination.
Moisture contamination from handpieces
or air-water syringes.
Oil contamination from handpieces or
air-water syringe.
Surface roughness of tooth surface
Fluoride content of teeth.
Presence of plaque, calculus, extrinsic
stain or debris

FACTORS AFFECTING
ADHESION TO MINERALIZED
TISSUE

 as given by Gwinnet

(1990).
 Physical and chemical properties of the
adhesive and the adherent.
 Lack of homogeneity between them.
 Manner of transmission of the applied
loads through the bonded joint.
 Thickness of the interface.
 Form of surface pretreatment or primer
chosen for the substrate









Furthermore, the factors related to the
oral environmental
Moisture
Physical stresses
Changes in temperature
Changes in pH
Dietary components
Chewing habits.

Chemistry of Adhesive agent
Chemical
 Adhesion
 Adhesion


adhesion
by coupling agents
by grafting reaction


CRYSTAL GROWTH ON THE
ENAMEL SURFACE
 An alternative to the conventional

phosphoric and etch technique has been
developed by R. Maijer and D.C.
Smith.
 This system consists of a polyacrylic
acid treatment, liquid containing a
sulfate component that reacts with the
calcium in the enamel surface to form a
dense growth of small, needle – shaped
crystals.

 These crystals grow in so called

spherulitic habit
 The crystal buildup on the enamel serves
as an additional retentive mechanism for
the resin that bonds to the tooth surface.
In this procedure the bond does not rely
on extensive penetration into the enamel.
This brings about “micromechanical
interlocking” at the enamel surface.

MICRO AIR ABRASION
 An

alternative to acid etch
 In 1943 Dr. ROBERT BLACK began
his studies using micro abrassive.
 In 1951 an air abrassive instrument
was introduced( Airdent )


 This technique used high speed stream of

purified aluminium oxide (alpha
alumina) particles propelled by air
pressure.


BONDING PROCEDURES


bonding of orthodontic attachment offers
several advantages when compared to
conventional banding.

It is esthetically superior
 Faster and simple.
 Less discomfort for patient (no. bond
seating and separation



Arch length not increased by band
material
 Allows more precise bracket placement
aberrant tooth shape does not result in
difficult bonding and poor attachment
position )
 Improve gingival condition is possible
and there is better access for cleaning.








Partially erupted tooth or and fractured tooth
can be controlled.
Mesiodistal enamel reduction is possible
during
Interproximal areas are accessible for
composite buildups.
Caries risk under loose bonds is eliminated.
interproximal caries can be detected and
treated. Dental invaginations on incisors can
be controlled.

No band spaces at the end of Rx to
close
 No large supply of bands is needed.










Attachments may be bonded to fixed
bridge work, particularly when the facial
surfaces of the abutment teeth are not in
metal.
More hygienic.
Improved appearance
Discomfort to patient is decreased.
Ease of application for clinician.

Disadvantages :





Bonded bracket has a weaker attachment than
a cemented band. Thus there is more chance
that a bracket will come off rather than a band
become loosened.
Some bonding adhesives are not sufficiently
strong.
Butter access for cleaning does not
necessarily guarantee better oral hygiene and
improved gingival condition, especially if
excess adhesive extends beyond the bracket
base.






Protect against interproximal caries of well
contoured cemented bands is absent.
Bonding is generally not indicates on teeth
where lingual auxiliaries are required or where
headgears are attached.
Rebonding a loose bracket requires more
preparation than rebonding or loose band.




Debonding is more time consuming than
debanding therefore removal of adhesive
is more difficult than removal of cement.


Bonding procedure :
 Cleaning
 Enamel

conditionong

 Sealing
 Bonding

SEALANT

A

CONTROVERSY


Bracket bonding procedure.
 TRANSFER
 POSITION
 FITTING
 REMOVAL

OF EXESS

 PremmiadAbdul WahabBOND PROCD.jpg


Type of adhesives :
 ACRYLIC

RESINS

 DIACRYLATE

RESINS


 ACRYLIC

RESINS
 Eg; Orthomite , Directon, Bondeze, genie.
 Based on self curing acrylics
 MMC monomer + ultrafine powder


 DIACRYLATE

RESINS
 Based on acrylic modified epoxy resin
Bowen’s resin or BisGMA may be
polymerized by cross linking in to 3-D
network..
 Filled
 Unfilled

 Buzzitha

etal 82 found that a highly
filled diacrylate resin with large filler
particles gave the highest values of in vitro
bond strength for metal brackets.


Two recent innovations


No mix adhesive
Rely a Bond,Right On,System1



Visible light-polymerized
adhesives
Fotofil, Durafil


Key to good success in bonding
 . Develop a

technique that ensure good
moisture control .
 Fit the brackets closely to the teeth
 Be sure that the setting of the adhesive is
undisturbed
 Use a strong adhesive.


G.I.C Bonding
 Introduced by

Wilson and Kent ‘’71
 IN 1986 ‘ White described a method of
bonding ortho brackets to and surfaces of
teeth with GIC.
 Cook ‘ 90 Compared in vivo bond
strength of GIC with composite and
concluded that bond strength of GIC was
not nearly as good as that of resin

 Fajen

etal ’90 evaluated bond strength
of 3 GIC against composite in vitro and
like look included that their bond strength
was significantly less.
 Compton etal ’92 :

Compared bond strengths of GIC,
stated that they must not be contaminated
by moisture during bonding procedures.
In addition they suggested

 Fricker

‘ 94 :

Worked with fuji similar LC GIC and
found same rate of success as that of
composite. He did mention however that
a dentine conditioner was utilized
for10sec, then rinsed followed by lightly
drying the tooth surface before bonding
the brackets with GIC.

 Kusy

‘ 94 :

Discussed the damage to the teeth
when debonding techniques are used for
removing composite. He advocated the
use of GIC for orthodontic bonding
procedures. Because their cements do not
need etching or cause damage during
debonding.

Advantages :
 Saves a significant amount of chair time
 Eliminates need for working in dry field.
 Eliminate need “ etching and priming

enamel surface
 Fluoride release protects teeth against
decalcification
 Repairs are quick and easy.

 Patient operator comfort.
 Reduced risk of caries.
 Have capacity to absorb Fluoride

from
fluoridated tooth paste, thus acting as a
rechargeable sow release Fluoride device
(long term Fluoride releasing agent.)


REVIEW OF LITERATURE
 Direct bonding of brackets using shorts

etching times.
 Wolf gang castensen : 1986 JCO .
 They concluded that the shorter etching
time of 15 seconds appears to be
sufficient for the bracket bonding


 Russull

Bert Forquhar – 1986

AMJO .
 -Share bond for phosphoric acid was
greater than polacrylic acid group.


.

Dual Cement resin in bonding :

Smith and Shivapuja.
 a dual cement, they can be used
where the depth of cure is
essential.


 Oslenetal

compaired the shear bond strength
and surface structure between conventional acid
etching and air – abrasion of human enamel.
And concluded Air abrasion technique for
enamel preparation has lower and clinically un
acceptable shear bond strength and this
technique for enamel preparation results in the
irriversible removal of both the inorganic and
organic component of enamel matrix and said
that air abrasion of enamel surface orthodontic
brackets is not advocated for routine clinical use
at this time. AJO – 1997 – vol 112.

 Comparison

of GIC a composite
AJO 1995 May (485-487)
 Miguel, Almeida and Chapel.
 They studied that composites showed a
statistically significant lover failure rate
compared to the GIC.


 Roberts-Harry

(1992) used a pulsed
Nd:YAG laser to etch the enamel
surfaces of teeth in vivo prior to the
bonding of orthodontic brackets with
composite resin and concluded that this
laser produced a macroscopic etch
pattern similar to that found with acid
etching

 J.A.


Vonfraunhofer et al (1993)

Arcoria .C.J., Lippas M.G. and
Vitasek B.A., (1993)


ADHESION BOOSTER
 Hypocalcifed
 Fluorsed
 Exessive

chalky
 Decidous enamel
 The do not present ideal surface for
bonding
 ENHANCE ADHESION BOOSTER

THANK YOU
Leader in continuing dental education


Enamel preparation & bonding materials /certified fixed orthodontic courses by Indian dental academy

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