Bonding materials

MATERIALS USED FOR DIRECT
BONDING AND ENAMEL
PREPARATION
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CONTENTS
• 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% H3 PO4.
• Newman : began to apply these findings to direct
bonding of orthodontic attachments.

• PremmiadAbdul WahabGRABER VANS1.jpg

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 acid-etching 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 compo

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-P-toulidine)

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 intensity

• 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 - Type II
• Ketac bond - Type III
• Vitra bond - Light cure

AVAILABLE AS
• Power/liquid in bottles
• Pre-proportioned power/quid in capsules
• Light cure system
• Powder/distilled water (water settable type)

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 40 KHN is comparable to that
of conventional GIC.

• 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
ENAMEL:
• 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 ACID 2

• 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 rete

– 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 by coupling agents
• Adhesion 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.
• Better 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 rebanding 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
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