Orthodontic resins

ORTHODONTIC
RESINS
www.indiandentalacademy.com

• CONTENTS
• INTRODUCTION
• TYPES OF ADHESIVES
• 1st
-5th
GENERATION
• DUAL CURE RESIN
• THERMOCURED RESIN
• REVIEW OF ARTICLES
• RECENT ADVANCES
• SEP
• CYANOACRYLATE
• FLUORIDE RELEASING ADHESIVE
• ADHESION BOOSTER
• HYDROPHILIC PRIMERS
• APC
• GLASS IONOMER CEMENT
• DYRACT
• ADHESIVES THAT BOND TO CROWNS AND RESTORATIONS
• DEGRADATION OF POLYMER
• LEACHING
• CYTOTOXICITY
• CONCLUSION www.indiandentalacademy.com

• The major current category of orthodontic adhesive systems is
based upon resin composites. They consist of three main
components
1. An organic matrix
2. Filler powdered ceramic such as barium aluminoborate silica
glass and
3.Coupling agent.
• Organic Matrix Monomer Components
• The organic matrix is formed by polymerization of an aromatic
or urethane dimethacrylate. It is the chemically active
component. Initially a fluid monomer but is converted into a
rigid polymer by a radical addition reaction.
Bis-GMA is commonly used monomer. It is derived from the
reaction of Bisphenol –A & glycidyl methacrylate.
Its molecular weight is higher than methyl methacrylate, which
helps in reducing polymerization shrinkage. Bis – GMA
monomer is highly viscous fluid, the addition of even a small
amount of filler would produce stiffness that is excessive for
clinical use. www.indiandentalacademy.com

• Properties:
• Large molecular size and
• Large chemical structure,
• Advantage :
• It is superior to many monomers of lower molecular mass by
virtue of
• -Lower volatility,
• -Lower polymerization shrinkage ------ more rapid hardening, and
production of a stronger and stiffer resin.
• Since Bis-GMA is highly viscous, viscosity is reduced by adding
monomers, like diethylene glycol dimethacrylate (DEGMA) and
Triethylene glycol dimethacrylate (TEGDMA) . A typical
formulation is 75% Bis-GMA and 25 % TEGDMA
• Another approach is the synthesis of Bis-EMA, a Bis-GMA
analogue that does not have the hydroxyl group in the structure.
• Less sensitive to water than Bis – GMA.

• Polymerization Activation -
• Four types of activation of free radicals are used in
the polymerization of the unsatu-rated methacrylate
groups of the resin composites. Activation of free
radicals is by:
• Self cure (SC)
– Two phase
– One phase ( no mix )
• Light cure (CC)
• Dual cure
• Heat cure

• Extent of Reaction: Degree of Conversion (DC)
• The DC of resin composite materials is the extent to
which carbon double bonds (C = C) of the monomer are
converted into carbon single bonds (C-C) to form
polymers during the polymerization reaction.
C = C  C-C
• DC affects the physical properties of composites.
• Inspite of extensive cross-linking on polymerization,
there is considerable residual unsaturation in the final
product ( 25% to 45 % )
• This ranges from 25 % to 45 %, or equivalently the degree
of conversion (DC) ranging from 55% to 75%. .

Unpolymerized resin has deleterious effects on:
• 1. The mechanical properties ----- acts as plasticizer
• 2. Dimensional stability of the restoration.
• 3. Biocompatibility.----- monomer leach in oral environment
What happens to uncured resin?
• 1. The unconverted methacrylate group resides in the polymer
network, either residual monomer or (a majority) as pendant
side chains (PSC).
• 2. A further possibility is a cyclization reaction.
The residual monomer molecules function as plasticizing
agents that can reduce the properties of polymer network and
monomers leach from the composite into the oral
environment.
Hence it is desirable to increase DC in order to produce
stiffer and more durable resins although, for a given
composite shrinkage increases with DC.

Polymerization Shrinkage
• Polymerization shrinkage is
partially explained by a
volumetric decrease arising
from the con-version of van
der Waals bonds into covalent
bonds.
• There is an intrinsic shrinkage
associated with resin
composites and that the time
dependence of this shrinkage
reflects the progress of the
polymerization.

• Dispersed Phase Components
• The filler or reinforcing ceramic phase in the early materials was
a ceramic oxide, such as silica or alumina, or a glass. A high
proportion of ceramic may also reduce polymerization
shrinkage.
Filler selection:
• 1. To reduce the thermal dimensional change of the resin
composite to a value matching that of tooth structure,e.g. fillers
such as lithium aluminum silicate.
• 2. The need for a good refractive index match with the organic
monomer to secure adequate translucence for aesthetic appear-
ance. Radiopaque glasses containing elements such as barium,
strontium, and zinc can be used.
• 3. Large volume of hard filler particles has been incorporated
based on the concept of attainment of high compressive strength
and stiffness and on evidence that abrasion resis-tance improves
as filler content increases and that fine fillers wear more than
coarse particles.

Type of adhesives:
They are classified as
A. Based on the basic bonding system type
1. Acrylic base systems- Poly (methyl methacrylate) systems
2. Diacrylate systems- Bis-GMA systems
3. Glass ionomer systems- 1. Chemical cured
2. Light cured
3. Dual cured
B. Based on fluoride content
1. Fluoride releasing systems
2. Non-fluoride releasing systems
C. Based on the filler content
Lowly filled bonding systems
Highly filled bonding systems.
D. Based on the curing systems
1. Self curing system
2. Light curing system
3. Dual curing system
4. Heat curing system

First Generation Bonding Adhesives
This generation included unfilled acrylic resins and epoxy resins.
The first bonding adhesives used in orthodontics was essential
unfilled poly (methyl methacrylate) anterior dental
restoratives.
The unfilled acrylic resins exist as powder - liquid or paste/paste.
Powder Contains
1. Poly (Methyl methacrylate).
Poly (methyl methacrylate) is a transparent resin of remarkable
clarity it transmits light in the ultraviolet range to a
wavelength of 250 nm
2. Initiator:
Benzoyl peroxide (0.3 to 3%) To start an addition
polymerization process, free radicals must be present. Free
radicals can be generated by activation of monomer molecules
with UV light, visible light, heat or energy transfer.
Initiation period is the time during which molecules of the
initiator become activated forming free radicals that interact
with the monomer molecules.

Liquid :
• Methyl methacrylate monomer
The liquid monomer methyl methacrylate is mixed with
the polymer. Methyl methacrylate is a clear, transparent
liquid at room temperature.
• Cross-linking agent -- Ethylene dimethacrylate (5% or
more)
• Inhibitor: (Monomethyl ether of hydroquinone: (0.006%)
To minimize or prevent spontaneous polymerization of
monomers, inhibitors are added to the resin systems.
These inhibitors have a strong reactivity potential with
free radicals. If a free radical is formed, the inhibitor
reacts with it and controls the reaction.

Unfilled bonding adhesives cause less enamel damage and are
indicated for bonding of acrylic orthodontic appliances to
enamel.
Disadvantages of Unfilled Acrylic Resins :
Low hardness and strength
High co-efficient of thermal expansion
Lack of adhesion to tooth structure
High polymerization shrinkage.
E.g. of Unfilled Resins: Bracket Bond, Genie

Epoxy Resins
The resins, which include a catalyst, are used in dental
composites, pit & fissure sealants and orthodontic bonding
resins. With so many different application, a large number of
dental products that use epoxy resins were developed,
especially Bis-GMA
Bis-GMA is an aromatic ester of a dimethacrylate,
synthesized from an epoxy resin (Ethylene glycol of Bis-
phenol A) and methyl methacrylate.
Disadvantages:
Lack of color stability
Water sorption
Patient sensitivity
Report by Athas and associates suggest that Endur M produced
carcinogenic effects. Endur M is now currently replaced with
Endur, which shows no carcinogenic effects on ingestion.

Second Generation
These are UV light activated resins. The second-generation
materials provided greater bond strengths than had existed
previously. The major disadvantage were UV light itself. which
even with the best control was a moderate hazard and an indirect
technique with a tray carrier was needed to position the brackets.
This interfered with access of the UV light to the resin beneath
the brackets and made cleaning difficult.
It used Bowen's Hybrid molecule, similar to Epoxy resin, but
functional reactive groups are acrylic. It consists of
• Bisphenol glycidyl methacrylate
• Esters of alkyl benzoin were incorporated to facilitate UV
activation.
Advantages as compared to 1st
generation :
• Higher bond strengths when compared to first generation.
• Low polymerization shrinkage
• Greater hardness
• Low water absorption.
Disadvantages are radiation hazards and limited depth of curewww.indiandentalacademy.com

• Third Generation (Two paste system)
• Representative product Concise (3M)
• First to be tried by orthodontists in the early
days of bonding. Their application involves
mixing of the paste and liquid components.
• Compared with unfilled resins, the filled
resins have greatly improved thermal
expansion qualities.
• Silane was used to coat filler particles that
could bond chemically to the resin.

The major constituents are
• Resin Matrix - Bis-GMA or
Urethane Dimethacrylate (UEDMA)/or
Triethylene glycol Dimethacrylate (TEGDMA).
• Filler Particles - are produced by grinding or milling quartz or
glasses to produce particles ranging in size from 0.1 to 100 /
microns. Silica particle (0.04 /lm) are obtained by pyrolytic
process. Depending on size of particle they are classified as:
Macro filled (10 to 30 microns) e.g. Concise.
Micro filled (0.2 to 0.3 microns) e.g. Endure, dynabond.
• Coupling agents: The bond between the two phases of
composite is provided by the coupling agent i.e., between resin
matrix and filler particles.
Titanates and Zirconates and organosilanes such as gamma
-methacryloxypropyltrimethoxy silane is most commonly
used.

Activator-Initiator system
Third generation is two paste systems and activated by
autopolvmerization.
• One paste contains benzoyl peroxide initiator
• Other tertiary amine activator - (N, N-dimethyl-P-toluidine).
1- 2 % BP (benzoyl peroxide) in the monomer portion as a
free radical initiator.
The activator in the other paste for these materials has usual-
ly been a tertiary amine.
Most commonly di-hydroxyethyl-p-toluidine (DHEPT), which
gives better color stability than the traditional dimethyl-P-
toluidine (DMPT).
• The activator acts as an accelerator so that, on mixing, the
benzoyl peroxide fragments into free radicals at room
temperature, thus initiating polymerization.
Inhibitor
• To prevent spontaneous polymerization of monomers.
Inhibitor reacts with free radicals until they are depleted.
E.g. -7 butylated hydroxytoluene (0.01 wt %).www.indiandentalacademy.com

Disadvantages: Clinical handling
1. The manipulative process is problematic, relatively time-
consuming, and cumbersome.
2. Mixing of the two components introduces potentially critical
defects such as surface porosity and air voids in the bulk
material, owing to the prolonged exposure to air and the
inevitable entrapment of air bubbles.
3.High amount of monomer leaching.
Studies have shown that photo cured composites, intentionally
mixed as if they were chemically cured materials, also
demonstrated severely porous surfaces and voids in the bulk
materials.
Low degree of cure (DC-55%) and disproportionately high
amount of monomer leaching is attributed to the mixing
process and to the detrimental effect of air entrapment on the
carbon double- bond conversion in the vicinity of voids.

1 to 1 bonding system
It is one of the most popular and dependable 2-paste selfcure
adhesive systems available for direct or indirect bonding of
metal, Ceramaflex ceramic or plastic attachment.
Extra small quartz particles allow a smooth mix without
sticking to spatula.
Simple one to one mixing ratio of both the sealant resins and
bonding pastes make 1 to 1 easy to use. It eliminates bracket
drift and reduces decalcification due to the "feather edge" on
the tooth surface.
It is particularly recommended when close adaptation
between tooth surfaces and bonding pads is not possible as is
often the case with lingual bonding of brackets and retainers.
Working Time = 1 /2 minutes
It can be increased by cooling the paste and/or cooling the
slab.

FOURTH GENERATION
No-mix adhesives
They were intended to minimize the mixing induced defects and
to reduce the steps
With these "no-mix" materials, the composite can be placed on the
tooth surface in unpolymerized form, while the polymerization
catalyst is placed on the back of the brackets. Contact between the
bracket and tooth with the intervening adhesive permits inter
diffusion of agents such as benzoyl peroxide (initiator) and amine
( activator) from the respective components.
Inhomogeneous polymerization pattern due to sandwich technique
involved in diffusion of liquid component into paste during
application. Enamel and bracket sides of adhesive are more
polymerized relative to middle zones
When the tray carrying the brackets is placed against the tooth
surface, the resin immediately beneath the bracket is activated and
polymerizes, but excess can be scaled away around the margins of
the brackets.

Disadvantages
1. Artun and Zachrisson states that, some components of the fluid
reagents of no-mix systems, and of unreacted monomer have
recently been suspected of having a mutagenic potential.
2. The 'no-mix' adhesive according to them does not save time as
the archwire cannot be engaged with minimum of delay.
E.g.Monolok Unite.
'Right-on' No mix Adhesive
Right-on no mix adhesive is the most advanced selfcure
bonding system available. It provides superior bond strength
drift-proof bracket placement and 2-year shelf life without
refrigeration. The adhesive paste is conveniently preloaded in
syringes or disposable syringes to simplify bonding produces.
Archwires can be placed after 7 minutes after the last bond.’
Right-on' bonds metal, Ceramaflex ceramic or plastic brackets
to either etched enamel or acrylic crowns.
It may be used for indirect bonding

FIFTH GENERATION
Compared with UV light, visible light has deeper curing capabilities, more
effective through enamel and does not diminish with time or with intensity
of the light source.
The light cured resin is a single paste system that consists of a ketone and
an amine as initiators. The ketone, camphoroquinone is sensitive to blue
light at 470 nm wavelength which catalyses the polymerization reaction.
VLC resin usually employs free radical initiators such as camphoroquinone
(CQ) and an amine reducing agent such as N, N-di-methyl-amino-ethyl
methacrylate (DMAEMA).
The radicalized ketone (CQ) alone may initiate the photo polymerization.
A reducing agent is generally added to light-cured composites for the
following reason. The amine radical is responsible for initiating the
polymerization and is more efficient than the radical formed from the
ketone. These intensified radicals can thus significantly improve the degree
of cure. The concentration of CQ photo sensitizer is in the range 0.17-1.03
mass% of the resin phase and that of DMAEMA reducing agent is 0.86
-1.39 mass%.
The combined photosensitizer/reducing agent complex has an extended
absorption band within the visible light (VL) spectrum.

• Tavas and Watts showed that sufficient light may be
transilluminated by the teeth to effect adequate photo
polymerization of the material. In the case of translucent
ceramic brackets, light-curing is straightforward.
• Tawas and Watts developed the transillumination technique to
bond metal brackets onto teeth in vitro with visible light-cured
composite
• Results from laboratory investigations have suggested that
visible light-cured composite have similar physical properties
to chemically cured resins.
• Read stated that the entire adhesive under the bracket is
polymerized after initial exposure to visible light and that a
force can be immediately placed on the bracket after curing.
• The disadvantages of light-cured resin are associated with
incomplete polymerization beneath the surface and a limited
depth of cure. Doubling the exposure time and exposure
through tooth substance increased the cured depth.

Reliance Quick Cure Orthodontic Paste
Light curing of a metal bracket in only 6 seconds with a conventional
curing light is possible. Unique chemistry provides a broader area of
sensitivity to blue light for a faster and more complete cure.
Ideal viscosity, no bracket floatation, easy cleaning, no stringing.
Quick cure paste can be used with light bond, assure or any light
cured sealant.
Transbond XT light cure adhesive
Transbond XT is currently distributed with instructions to cure both
the mesial and distal or incisal and gingival surfaces of metal
orthodontic brackets for 10 seconds each, for a total of 20 seconds
per bracket followed by immediate archwire insertion.
Advantages
Extended working time allows precise bracket placement.
Immediate bond strength, allowing archwire to be placed immediately
following cure.
It saves time for rebonds.
Efficient bonding of ceramic and metal brackets.
Excellent handling properties like -No bracket drift &easy flash clean
up.

• The disadvantage of UV-light like 1 minute of curing per
millimeter of thickness led to development of visible Light cured
adhesives. The longer curing time (40 seconds) of these lead to the
introduction of Argon Lasers. They cure filled resins in 10
seconds and unfilled resins in 5 seconds, at a wavelength of 488
nanometer. More recently Xenon arc light units have been
introduced for rapid light curing.
• Visible Light cure emit light at 480 nm, but the energy is emitted
over a much broader range. Light from the Argon laser is
collimated, which results in more consistent power density over
distance. The power density of light Cure decreases dramatically
with distance due to divergence of light from the source. Visible
Light curing units uses bulbs, reflectors and filter which can
degrade and decrease curing efficiency.
• Nazir Lalani et al (Angle2000) found that 5 seconds was adequate
for bonding metal brackets. Increasing the time did not increase
bond strength significantly.

Dual cure Resins
These resins are both light activated and chemically cured. Thus
they can be cured completely by using a light source or by the
catalyst and base reaction of the material. These resins originally
were applied to composite buildups and to cementing of laminate
veneers where depth of cure is essential.
Initiation is achieved through exposure to light. Reaction
proceeds following a chemically-cured pattern
Combines disadvantages of handling of both light-cured and
chemically cured materials. The most time consuming
applications
Increased degree of cure and bond strength, but questionable
clinical significance for their differences with light-cured
materials.
Introduced Into the profession from prosthetic dentistry
applications. Ideal candidates for bonding molar tubes.

Smith and Shivapuja examined the dual cements
• Vivadent "thick"
• Vivadent "thin"
• Reliance "fluoride releasing".
"Thin" showed higher bond strength, because of reduced viscosity
and increased wetting. But handling properties are diminished
because of bracket drift. The "thick" cement has increased filler
particles, which reduced bracket drift.
The "fluoride releasing" has reduced bonding strength. It was
extremely viscous and all failures occurred at the tooth adhesive
interface.
Advantages of Dual cure resins
• Reduced curing time and good depth of cure.
• Its main advantage was reduced bonding time. In the visible LC,
time required to cure entire maxillary and mandibular arch is 13.5
minutes.
40 sec x 20 brackets = 13.5 minutes (VLC)
The curing time of Dual Cured resins is approximately 6.5
minutes.
10 sec x 20 brackets + 3 minutes for SC = 6.5 minutes (DC)

Disadvantages
It centered on the chemically cured properties of the dual
cements.
1. Mixing may introduce bulk defects , increasing the porosity.
2. Placement of a bracket with half-hardened cement or
removing the flash from such a bracket would drastically
affect the bonding strength.
In orthodontic bonding, the clinician can control the setting
time by
1. Allowing the resin to set by chemical cure
2. Curing with visible light source for 30 seconds
3 Curing with a visible light source for 10 seconds and then
allowing the resin to completely polymerize with its
chemically cured properties. This gives more time for proper
placement of brackets. Furthermore, the clinician can be
assured of complete polymerization with the chemical
properties of Dual Cured cements.

• Thermocured Introduced in orthodontics for indirect
bonding .
• It is claimed that these adhesives present increased
polymerization rates and hence superior properties.
• Not intended for direct bonding.
• Nanda & Sinha et al (1995 jco feb) They used a thermal
cured Fluoride releasing resin to secure brackets on the
model. For bonding on cast, they used Thermocure and
Maxicure sealant A & B was used in clinical setting.
• They reported a failure rate of 5 %
Drawback
• Bracket float
• Ceramic bracket cannot be exposed to heat

REVIEW OF ARTICLES
A. Self cure
Advantages of Concise (two phase) over 'no-mix' Adhesive
(A.J. O. 1982 April)
According to Artun and Zachrisson
1. Bond strength of concise exceeds no mix adhesive.
2. More homogenous and predictable mix is obtained.
3. No reports of allergic reactions to Concise
4. Shorter "snap" time, it is possible to ligate archwires
sooner with Concise.
They recommended a four-handed approach to Bonding to
help mix the two paste system and enhance bonding
results.

Whitlock et al (ajo1994) compared 3 different adhesive
systems, when used alone and with a porcelain-priming
agent, to bond ceramic brackets to porcelain surfaces. The
'no-mix' adhesive liquid had the lowest shear bond strength
without the priming agent and the highest bond strength with
the priming agent. This is because 'no-mix' adhesive liquid is
not polymerized before the bracket is applied.
Ching et al. (EJO2000) found that static loads such as tying in
of archwires can be placed on Brackets 15 minutes after
cementation, without a clinically significant reduction in
bond strength of a No-mix adhesive (Unite). Ireland and
Sheriff found that it was safe to tie to archwires on the same
visit, 1 hour after cementation of the No-mix adhesive (Right
on).

B. VLC vs SC
• Greenlaw and Colleagues (1989 AJO ) found that the bond
strength of visible light cured adhesives was insufficient after
initial curing and suggested that the slow strength was due to
incomplete polymerization. They recommended delaying
archwire for 24 hrs. The Greenlaw study compared a visible
light cure adhesive (Heliosit Orthodontic) with a one-paste
chemically cured orthodontic adhesive (Unite). The Heliosit
was used for 20 seconds from incisal and 20 seconds from
gingival. The bond strength for the light-cured adhesive at one
hour was only 26% of that found at 30 hours, but was still only
one-half that of the chemically cured adhesive at 30 hrs.
• Larry and Colleague’s study indicate that there are advantages
to increasing the setting time of light cured adhesives.
Extending the setting time to 5 minutes produced more than
20% increase in bond strength, than 2 minutes. At the 2-
minute setting time, bonds cured for 40 seconds were 30%
stronger than those cured for 20 seconds.
He suggests therefore 40 seconds curing time, 20 on mesial
and 20 on distal for maximum shear strength.www.indiandentalacademy.com

• Wang and Meng (AJO l992) found that visible light is
powerful in curing the visible light-activated composite
resin under solid metal brackets. The bond strength of
light cured resin of Transbond, except in cases of light
exposure of 20 seconds, is stronger than that of the self-
cured resin of Concise. Transbond cured for 40 sec is
therefore recommended.
• Rashid Ahmed Chamda (AJO 1996) compared the bond
strength achieved with L.C. Bonding system and a
chemically cured system over a 24 hr period. There was
no significant difference between bond strengths
achieved by chemically cured & Light Cured systems at
10 minute, 60 minute and 24 hr interval.

• Hugo R. Amass (Ajo98) compared L.C. achieve material
(sequence) and C.C. adhesive (System 1+) and found no
statistically significant failure rates between the two.
• Millet et al. (Angle98) found that failure rates of brackets
bonded with light cured resin (Transbond) to pre-molars were
almost twice that of brackets bonded to canines or incisors.
The large failure may be due to
1. Difficulty with moisture control.
2. Larger amounts of prismatic enamel.
• Hugo et al. (1998 AJO ) compared the failure rates of a
chemically cured resin (system 1+) and visible light cured
bonding material (sequence). There were no statistically
significant failure rates between the two.

C. SC ( both two phase & no mix ) vs LC vs DC
Eliades et al., (EJO2000 AUG) compared the degree of cure
of
• A light cured (Transbond XL)
• Two pastes chemically cured (Concise)
• One phase (No-mix, chemically cure) – Unite
• Dual-cured (Two paste) - Duocement
Metal brackets and ceramic bracket were bonded.
1. The dual-cured product demonstrated the highest degree
of cure followed by
Light cured combined with ceramic bracket
No mix
Two paste chemically cured system.
• The combination of metallic bracket with the light cured
produced similar cure as that of the chemically cured
material.

RECENT ADVANCES
The Prompt L-Pop System
• The Prompt L-Pop system is a unit-
dose system, with etchant, primer,
adhesive, and microbrush sealed in a
triple-lollipop-shape aluminum foil
package. Acid etching, rinsing,
priming and application of adhesive
are thus combined into one step.
Prompt L-Pop (ESPE Dental AG,
Seefeld, Germany) is an all-in-1
adhesive for composites and
compomers. Prompt L-Pop contains
methacrylated phosphoric acid esters
that combine an acidic component for
etching the enamel and the primer.

Procedure
• 1. The enamel surface is pumiced or micro abraded.
• 2. The top bubble is folded, forcing the liquid into the
second chamber.
• 3. The second chamber is popped and folded forcing the
adhesive mixture into the third chamber, which contains
the microbrush. The brush is stirred around in the 3rd
chamber to saturate it with resin.
• 4. The adhesive is rubbed into the enamel surface for 15
seconds and air dried lightly to evaporate the water
carrier, leaving a smooth glossy surface rather than the
frosted appearance of phosphoric aid.

• Prompt is a low ph - self-etching adhesive that procedures
a well defined etch pattern similar to that of phosphoric
acid.
• As with 4th and 5th generation adhesives, it forms a micro
retentive bond with the treated surface. Unlike these
systems, it allows the etchant and monomer to penetrate at
the same time, avoiding potential technique errors and
nanoleakage. Prompt shows outstanding bond strength to
both dentin and enamel.
• Light curing can be done with visible Light Curing unit or
more intense Argon lasers and Plasma-arc curing systems
by aiming at the adhesive bracket interface from the
occlusal surface.

• Cyanoacrylate ( Moisture active adhesives )
• It requires rather than tolerate the presence of moisture for
proper polymerization. It does not require bonding agent. The
bonding surface must be intentionally wetted prior to
application. Bonding is just one step procedure. The presence of
saliva however adversely affects their long term clinical
performance
• A number of studies have found no adverse effects from long-
term use of cyanoacrylates inside the human body.
• Smart Bond (Gestenco) is not the same as the glue that can be
bought in a hardware store; its viscosity has been altered with
silica gel. It is also important that the surfaces to be bonded are
as close together as possible.
• Because polymerization starts only in the presence of moisture
and pressure, the clinical procedure for bonding with Smart
Bond differs from that of conventional adhesives.

Disadvantage
1. Cyanoacrylate does not work well on polycarbonate brackets
with enlarged retention surfaces unless they are treated with
water.
2. The excess material will be instantly polymerized and turned
into white acrylic powder around the bracket, called "blooming".
3. The material cannot fill spaces or gaps, which is why a bracket
base with deep mesh or undercuts will have lower bond strength.
Advantages
1. Vapor from the unpolymerized material is immediately
polymerized when it comes in contact with water, which also
eliminates any taste.
2. No residual monomer can react later in the process, and thus
the material absorbs no water. This prevents the adhesive from
discoloring during treatment. High bond strengths are reported for
Smart Bond.
3. Smart Bond presents no particular danger of fracturing the
enamel during debonding.

Fluoride-Releasing Orthodontic Adhesives
The presence of enamel demineralization or so-called
'white spots' is a significant problem. Incorporation of
fluoride into enamel structure as fluoroapatite can
result in remineralization of small decalcified or caries
lesions and also reduces the formation of new lesions.
Inorganic fluorides have high polar nature and dental
resins have low polarity, which causes loss of
mechanical integrity .
Organic fluoride incorporation has a plasticizing effect
that also yields poor properties.

Rawls and Zimmerman (Ajo1989) introduced an experimental
fluoride releasing resin that has anti-cariogenic properties.
FR 2.5 Ortho adhesive is unique.
Fluoride release occurs when fluoride ions are exchanged for
other anions in the oral environment. Rather than supplying
fluoride to the oral environment by material dissolution, the
fluoride is given up in exchange for other anions and the
structure integrity of the resin is maintained.
• Underwood, Rawls and Zimmerman found that the use of this
adhesive resulted in 93% reduction of occurrence of dark
zones, indicating a reduction of early demineralization.
• Sansing, Rawls and Shage found that the bond strength of this
experimental resin compares favorably to existing commercial
adhesive.

Adhesion Boosters or Adhesion Promoters
Adhesion booster, a tooth surface primer advocated by Bowen
et al., to increase the bond strength of composite resin to
tooth surface.
Two recently introduced boosters include
Enhance LC and All Bond 2
According to the manufacturer Enhance LC can increase
adhesion of composite to any enamel (including fluorosed,
hypocalcified, or deciduous enamel), metal or composite
surface.
With the adhesion Booster Megabond applied on the new
bracket base Newman et al., found that the bond strength
was lower than new brackets without Megabond, whereas
the bond strength of sandblasted new brackets with
Megabond was greater than brackets sandblasted without
megabond.

Ching et al; compared Enhance LC and All Bond 2 to bond
debonded brackets.
They found that when new brackets are used neither All-
Bond 2, nor Enhance LC improves bond strength
significantly.
When rebonding debonded brackets, they found that without
the use of any boosters, sandblasted rebonded brackets yield
less bond strength than new brackets.
Enhance LC fails to increase bond strength of sandblasted
rebounded brackets.
All-Bond 2 significantly increased bond strength of
sandblasted rebonded brackets.
All-Bond 2 when used with sandblasted debonded brackets
provides comparable results (17 MPa) to new brackets.

Hydrophilic Bonding Systems (Ajo200l)
Failure of orthodontic bonded attachments and
brackets is mostly due to contamination.
Materials that over come the moisture and
contaminants in the oral environment have been
developed. It contains hydrophilic primer
(HEMA) dissolved in acetone. HEMA is a water
soluble hydrophilic monomer .
Webster and Nanda compared 2 hydrophilic
bonding systems, MIP and Assure. Similar
bonding procedures were used; the difference
was in the application of primer.

The results showed that the no contaminated surfaces had the
highest bond strengths for both the hydrophilic and
hydrophobic materials.
Transbond XT with primer -- 26.9 MPa
Transbond XT MIP -- 28.1 MPa
Assure with prime -- 20.4 MPa
When using hydrophobic primer, if the etched surface is
contaminated with saliva before primer application, it may
be necessary to reetch before proceeding with bonding.
If contamination occurs after primer placement and curing,
then a simple drying and reapplication of primer is all that is
necessary.
The hydrophilic primers also showed improved bond strengths
with reapplication of primer after saliva contamination.

Adhesive Pre-coated Brackets
In an attempt to save chair side time during bonding,
orthodontists are using ceramic and metal brackets that have
been pre-coated with adhesive material.
The ingredients in the adhesive applied to bracket and that of
ordinary Transbond XT is the same. The difference is
limited to percentage of the different ingredients
incorporated.
Transbond XT contains
14% Bis GMA
9% Bis EMA
77% fillers (Silicate quartz and submicron silica).
The corresponding values for pre coated brackets is
12% Bis GMA
8% Bis EMA
80% fillers.

• The composition changes are for increasing its viscosity,
causing the bracket to adhere more readily to the tooth during
initial stages of bracket positioning.
• Bishara et al compared the shear bond strength of ceramic and
metal brackets, which are not coated and pre-coated. They
found that
• 1. Pre-coated ceramic brackets have similar bond strength as
that of uncoated brackets bonded with adhesive.
• 2. Pre-coated metal brackets have lower bond strength than
uncoated brackets because of high viscosity causing less flow
into the mesh of the brackets.
• 3. All three provided clinically acceptable bond strength.

REVIEW OF ARTICLE
SEP vs MULTI STEP CONVENTIONAL BONDING
1 (Bishara et al., AJO 2001). Brackets bonded with the SEP were
found to have a significantly lower mean shear bond strength
compared with those bonded with a conventional two-stage
adhesive system. The study, however, did not compare bonding
time for each adhesive system.

•
Use of SEP to bond orthodontic brackets to the enamel surface resulted
in a significantly lower, but clinically acceptable, shear bond force as
compared with the control group
The comparison of the adhesive remnant index scores indicated that
there was significantly more residual adhesive remaining on the teeth
that were treated with the new self-etch primer than on those teeth that
were bonded with the use of the conventional adhesive system.

Effect of self-etching primers on bond strength--are they
reliable? Angle 2003 Feb.
Karaman et al studied to determine the effects of using
three self-etching primers on the shear bond strength
(SBS) of orthodontic brackets and on the
bracket/adhesive failure mode.
• In the control group, teeth were etched with 37%
phosphoric acid. In the experimental groups, the enamel
was conditioned with three different self-etching primers,
Clearfil SE Bond (CSE), Etch & Prime 3.0 (EP3), or
Transbond Plus (TBP), as suggested by the manufacturer.
• The brackets were then bonded with Transbond XT in all
groups

• TBP group produced significantly higher SBS ( 16.0 +/- 4.5
MPa) than that found in SE, EP3, and the control (acid-etched
[AE]) groups.
• CSE produced SBS ( 11.5 +/- 3.3 MPa) comparable to those
Acid etching ( 13.1 +/- 3.1 MPa).
• EP3 resulted in the lowest mean SBS value (mean 9.9 +/- 4.0
MPa).
• A comparison of the adhesive remnant index scores indicated
that there was more residual adhesive remaining on the teeth
that were treated with conventional acid etching than in the
CSE and EP3 groups. In the TBP group, the failure sites were
similar to those of the AE group but different from those of the
CSE group. www.indiandentalacademy.com

• Shear bond strength of orthodontic brackets bonded with a modified
1-step etchant-and-primer technique. Ajo 2003 oct Dorminey et al.
The purpose of this study was to compare the shear bond strength
of orthodontic brackets bonded to enamel with a conventional,
multistep adhesive system and a self-etching primer adhesive
system. In addition, a third group was included in which the air
dispersion step in the self-etching primer system was omitted.
SBS (SD) MPa
• group 1: conventional multistep adhesive 11.3 (2.2) MPa
• group 2: self-etching primer system 11.9 (3.2 MPa
• group 3: SEP system without air dispersion 8.2 (2.8) MPa
• The mean shear bond strength of the self-etching primer group in
which the air dispersion step was omitted was significantly less than
in the other 2 groups. There was no difference in mean shear bond
strength between the conventional, multistep adhesive system and
the self-etching primer system when the primer was dispersed
correctly www.indiandentalacademy.com

• SEP & SALIVA CONTAMINATION
• Efficacy of using self-etching primer with a 4-META/MMA-
TBB resin cement in bonding orthodontic brackets to human
enamel and effect of saliva contamination on shear bond
strength. Angle 2004 apr
Hayakawa et al
The objective of this study was (1) to evaluate the effectiveness
of Megabond when used with Superbond C&B, a 4- META/
MMA – TBB resin to bond orthodontic metal brackets to
human enamel and (2) to examine the influence of saliva
contamination on shear bond strength.
• 4- META/ MMA – TBB resin -----( 4-methacryloloxyethyl
trimellitate anhydride (4-META)/methyl methacrylate (MMA)-
tri-n-butyl borane (TBB) resin),

There were no significant differences in shear bond strength
between phosphoric acid etching and self-etch priming for no
contamination, saliva contamination, and repeat treatment
(etching or priming) after saliva contamination.
• With phosphoric acid etching, saliva contamination
significantly decreased the shear bond strength.
• With self-etching primer treatment, however, saliva
contamination did not cause any decrease of bond strength.
• Phosphoric acid etching produced more enamel fracture than
self-etching primer treatment. Field-emission scanning
microscopy revealed less dissolution of enamel surface
resulted from self-etching primer compared with phosphoric
acid.
• These results suggest that Megabond when used with
Superbond C&B resin cement may be a good candidate for
bonding orthodontic brackets to human enamel.

• SEP (INCLUDING F RELEASING )VS CONVENTIONAL
• Bishara et al ( Angle 2002 June
• In group 1 (control), teeth were etched with 37% phosphoric
acid; after the sealant was applied, the brackets were bonded
with Transbond XT and light cured for 20 seconds.
• In group 2, a self-etch acidic primer was applied as
suggested by the manufacturer, and the brackets were then
bonded with Transbond XT as in the first group.
• In group 3, an experimental self-etch primer EXL #547 was
applied to the teeth as suggested by the manufacturer, and
the brackets were then bonded as in groups 1 and 2.
• In group 4, a fluoride-releasing self-etch primer, One-Up
Bond F was applied as suggested by the manufacturer, and
the brackets were then bonded as in the other groups.

One-Up Bond F (mean +/- SD strength, 5.1+/-2.5
MPa) and Prompt L-Pop (strength, 7.1+/-4.4 MPa)
had significantly lower shear bond strengths than
both the EXL #547 self-etch primer (strength, 9.7+/-
3.7 MPa) or the phosphoric acid etch and the
conventional adhesive system (strength, 10.4+/-2.8
MPa).

Effect of water and saliva contamination on shear bond strength of
brackets bonded with conventional, hydrophilic, and self-etching
primers. Sfondrini et al AJO 2003 jun
• This study assessed the effect of water and saliva contamination on the
shear bond strength and bond failure site of 3 different orthodontic
primers
• Transbond XT,
• Transbond Moisture Insensitive Primer,
• Transbond Plus Self Etching Primer; used with a light-cured composite
resin (Transbond XT).
• Each primer-adhesive combination was tested under 7 different enamel
surface conditions: (1) dry,
• (2) water application before priming, (3) water application after priming,
(4) water application before and after priming,
• (5) saliva application before priming, (6) saliva application after priming,
and (7) saliva application before and after priming

• SEP, MIP & CONVENTIONAL MULTISTEP
• Effect of water and saliva contamination on shear bond strength of brackets
bonded with conventional, hydrophilic, and self-etching primers.
• Sfondrini et al (AJO 2003 June) assessed the effect of of water and saliva
contamination on the shear bond strength and bond failure site of 3 different
orthodontic primers
• Transbond XT,
• Transbond Moisture Insensitive Primer,
• Transbond Plus Self Etching Primer; used with a light-cured composite resin
(Transbond XT).
• Each primer-adhesive combination was tested under 7 different enamel surface
conditions: (1) dry,
• (2) water application before priming, (3) water application after priming, (4)
water application before and after priming,
• (5) saliva application before priming, (6) saliva application after priming, and
(7) saliva application before and after priming

• 1.Non contaminated enamel surfaces had the
highest bond strengths for conventional,
hydrophilic, and self-etching primers, which
produced the same strength values.
• 2.In most contaminated conditions, the self-etching
primer had higher strength values than either the
hydrophilic or conventional primers.
• 3.The self-etching primer was the least influenced
by water and saliva contamination, except when
moistening occurred after the recommended 3-
second air burst.

Effect of saliva on shear bond strength of an orthodontic
adhesive used with moisture-insensitive and self-etching
primer
Chung et al. Ajo 2003 oct
Materials were :
• Transbond Moisture-Insensitive Primer (MIP)
• Transbond Plus Self-Etching Primer (SEP)
• Hydrophobic Transbond XT primer (XT) was used as a
control.
Conditions:
• (1) control: etch/dry/XT,
• (2) etch/dry/MIP, (3) etch/dry/MIP/wet (saliva)/MIP,
• (4) etch/wet/MIP, (5) etch/wet/MIP/wet/MIP,
• (6) dry/SEP, (7) dry/SEP/wet/SEP,
• (8) wet/SEP, and (9) wet/SEP/wet/SEP.

• (1) Transbond XT adhesive with Transbond XT
primer and MIP in a dry field yields similar bond
strengths, which are greater than all other
groups,
• (2) saliva contamination significantly lowers the
bond strength of Transbond MIP,
• (3) saliva has no effect on the bond strength of
Transbond SEP,
• (4) Transbond XT adhesive with Transbond MIP
and SEP might have clinically acceptable bond
strengths in either dry or wet fields.

Effect of blood contamination on shear bond strength of brackets
bonded with conventional and self-etching primers. AJO 2004 march
• Sfondrini et al assessed the effect of blood
contamination on the shear bond strength and bond
failure site of 2 different orthodontic primers
(Transbond XT and Transbond Plus Self-Etching
Primer) used with adhesive-precoated brackets.
• Four different enamel surface conditions were
tested: (1) dry, (2) blood contamination before
priming, (3) blood contamination after priming, and
(4) blood contamination before and after priming.
•

• SEP & conventional in blood contamination
• Effect of blood contamination on shear bond strength of
brackets bonded with conventional and self-etching primers.
AJO 2004
• Sfondrini et al assessed the effect of blood contamination on
the shear bond strength and bond failure site of 2 different
orthodontic primers (Transbond XT and Transbond Plus Self-
Etching Primer) used with adhesive-precoated brackets.
• Four different enamel surface conditions were tested: (1) dry,
(2) blood contamination before priming, (3) blood
contamination after priming, and (4) blood contamination
before and after priming.

• Noncontaminated enamel surfaces had the highest bond
strengths for both conventional and self-etching primers,
which produced almost the same strength values.
• Under blood-contaminated conditions, both primers
showed significantly reduced shear bond strengths.
• For the conventional primer, no significant differences
were reported among the blood-contaminated groups,
whereas when the self-etching primer was used, condition
4 reduced significantly the bond strength values

• SEP: Transbond Plus & Ideal 1
• Comparison of the shear bond strength of 2 self-etch
primer/adhesive systems. Bishara & Laffoon. (AJO 2004) march
In group I, a self-etch acidic primer/adhesive system, Transbond
Plus (3M ), was applied on the enamel surface as suggested by the
manufacturer; it has 2 components that must be mixed before use.
The brackets were then bonded with Transbond XT and light-cured
for 20 seconds.
• In group II, a no-mix self-etch bracket adhesive system, Ideal 1
(GAC), was applied to the teeth. The self-etch primer has 1
component that does not need to be mixed before use. The brackets
were then bonded with the adhesive and light-cured for 20
seconds.
• The in vitro findings indicated that the shear bond strength
comparisons of the 2 adhesive systems were not significantly
different . The mean shear bond strength of the 2-component acid
etch primer was 5.9 +/- 2.7 MPa, and the mean for the 1-
component system was 6.6 +/- 3.2 MPa.

SEP VS CONVENTIONAL & FUJI ORTHO LC
H21 Effect of using self-etching primer for bonding orthodontic
brackets. Angle 2002 dec
Yamada. et al determined the shear bond strengths of orthodontic
brackets bonded with one of four protocols:
• (1) a composite resin adhesive used with 40% phosphoric acid,
• (2) the same composite resin used with Megabond self-etching
primer,
• (3) a resin-modified glass ionomer cement adhesive used with
10% polyacrylic acid enamel conditioner, and
• (4) the same resin-modified glass ionomer cement used with
Megabond self-etching primer.

• Megabond self-etching primer gave the same shear bond
strength as acid-etching when used with a resin-modified
glass ionomer cement.
• Megabond gave a significantly lower shear bond strength
when used with a composite resin adhesive.
• Megabond self-etching primer treatment produced less
enamel dissolution than did etching with phosphoric acid
and polyacrylic acids.
• The present findings provide evidence that Megabond self-
etching primer is a candidate for bonding orthodontic
brackets using the resin-modified glass ionomer cement,
with the advantage of minimizing the amount of enamel loss.

• SEP - CONVENTIONAL & FLUORIDE
VARNISH
• F 3 Effect of fluoride varnish on the in vitro bond strength
of orthodontic brackets using a self-etching primer system.
Kimura et al AJO 2004
• The results showed no difference in bond strength among the
conventional or self-etching primer system.. Adhesive remnant
index scores were not statistically different. The application of
fluoride varnish does not affect the bond strength of orthodontic
brackets to enamel with conventional or self-etching primer
systems.

CYANOACRYLATE & CONVENTIONAL
2001 Dec angle Bishara & Laffoon
•Cyanoacrylate did not show any significantly different shear bond
force (5.8 +/- 2.4 MPa) as compared to the control group (5.2 +/-
2.9 MPa).
•The comparison of the Adhesive Remnant Index scores indicated
that there was significantly less residual adhesive remaining on the
tooth with the cyanoacrylate than on the tooth with the conventional
adhesive system. In conclusion, the new adhesive has the potential
to be used to bond orthodontic brackets while reducing the total
bonding time.

• Wilner and Oliver (Bjo2000sept) found that
cyanoacrylates are unsuitable for use as a
bonding agent in routine orthodontic
practice. The bond strength deteriorated
after few works. It can be used to adhere to
wet surface and where less force is required
for a short time, as in impacted canines

• Effect of time on the shear bond strength of cyanoacrylate
and composite orthodontic adhesives. Ajo 2002 march
Bishara & Laffoon.
The bond strength of the cyanoacrylate adhesive was not
significantly different from that of the composite adhesive. Their
findings indicated that the cyanoacrylate and the composite
adhesives tested have clinically adequate shear bond strengths at
half an hour and at 24 hours after initial bonding. The clinician
needs to consider the properties of each adhesive: e.g., the need
to use a curing light and the ability to have more working time
with the composite adhesive versus no light but only a 5-second
working time before the cyanoacrylate adhesive starts to set.

• HYDROPHILIC & HYDROPHOBIC PRIMER
• 1. Littlewood et al (BJO2000june) found that
the bonds strength obtained with the use of
hydrophilic primer (6.43 MPa) was significantly
lower than the conventional primer (8.71 MPa).

Bond strength comparison of moisture-insensitive primers.
Foleyet al. AJO 2002 sept
The objective of this in vitro bonding study was to evaluate the
effectiveness of 2 moisture-insensitive primers, Assure and MIP
compared with a control hydrophobic primer, Transbond XT .
Protocols:
• (1) Transbond XT primer and adhesive applied to a non
contaminated surface;
• (2) Assure primer applied after saliva contamination;
• (3) MIP primer applied after saliva contamination;
• (4) Assure primer reapplied after saliva contamination;
• (5) MIP reapplied after saliva contamination; and
• (6) Assure adhesive applied after saliva contamination of the
primer.

• 1. Both bonding systems provide adequate bond strengths whether saliva
contamination occurs before or after the application of the hydrophilic
primers; therefore, additional mechanical preparation and reetching of the enamel
surface after saliva contamination might not be required.
• 2. Comparing saliva contamination after application of primer(4 &5), both MIP and
Assure had significantly greater shear-peel bond strengths than when contamination
occurred before the application of each primer.
• 3. Transbond XT and MIP group 5 (contamination between 2 layers of primer)
showed significantly greater shear-peel bond strengths compared with the other
groups.
• 4. The groups with saliva contamination before application of the primer showed
more frequent failures at the enamel/adhesive interface, suggesting that complete
penetration of primer was prevented (nanoleakage) , whereas the groups with saliva
contamination after the first application of primer showed more frequent failures at
the adhesive/bracket interface.
• 5. The greatest frequencies for EF on debonding occurred in the groups with the
highest bond strengths.

• angle 2003 aug
Klocke evaluated bond strength for a custom base
indirect bonding technique using a hydrophilic primer
on moisture-contaminated tooth surfaces.
• 1. Bond strength for the custom base indirect bonding
technique with the hydrophilic primer was not
significantly different in groups without contamination
and with water or saliva contamination before
application of the primer.
• 2. Moisture contamination after application of the
hydrophilic primer resulted in significantly lower bond
strength measurements compared with bond strength for
uncontaminated enamel.

MIP UNDER MOIST & BLOOD CONTAMINATION
G19 The effect of moisture and blood contamination on bond
strength of a new orthodontic bonding material. AJO 2001 july
Hobson et al evaluated the bond strength of Transbond MIP
under dry, moist, and blood-contaminated conditions. Dry
bonding resulted in significantly higher bond strength (15.69
MPa) than moist (12.89 MPa) or blood-contaminated (11.16
MPa) bonds.
• However, all bond strengths were in excess of previous reports of
required clinical bond strength, and it was concluded that
Transbond MIP is a suitable adhesive for bonding in conditions
of poor moisture control or blood contamination
• Transbond MIP is therefore an ideal bonding agent for bonding
during the surgical exposure of teeth.

• From the review of the above articles it can be
concluded that :
• 1.Non contaminated enamel surfaces had the
highest SBS for both the hydrophilic and
hydrophobic materials.
• 2.When the contamination occurred after the
primer was cured a simple drying and reapplication
of primer was enough to get adequate bond
strength.
• 3.Hydrophilic bonding systems showed improved
bond strength after reapplication of primer after
saliva contamination.

• FLUORIDE RELEASING ADHESIVES
• .William A Wittshire and Sophia (AJO 95 SEPT) compared
two non-fluoride visible light-cured orthodontic adhesives
(Heliosit Orthodontic and Transbond) with 2 fluoride-
containing visible L.C orthodontic adhesives (FluorEver
OBA and Light Bond). The 2 non-fluoride adhesives, both
released small amounts of Fluoride, despite bring non-
fluoridated. The Fluoride release could be due to small
amounts of fluoride such as barium fluoride present in the
inorganic phase.
• Light-bond had an immediate burst of F release during the
1st day followed by sharp decrease such that F could not be
detected for 2 weeks longer than non-fluoride adhesives.
• FluorEver continued to release F up to 85 weeks.

• Fluoride release from
FluorEver OBA up to
85 weeks.

• .The study conducted by Oggard et al (Ajo 97Feb), with the
fluoride releasing adhesive orthodontic cement VP 862 found
that the anti cariogenic effect is due to release of fluoride in to
the local environment than elevation of fluoride level in
saliva. Orthodontic cement VP 862 is a halogen light curing
adhesive.
• Chung and Piatti (JCO2000 July) compared the clinical bond
strength of fluoride releasing phase II with non-fluoride
releasing Phase II. Phase II and the non-fluoride releasing
Phase II, both had failure rates of less than 2% at 3 months
and less than 5% at 6 months.
• They concluded that fluoride releasing Phase II is clinically
strong enough for use as an orthodontic bonding adhesive.
(Fluoride may leach out of the material by ion exchange with
other anions in the oral environment, as proposed by Rawls
and Zimmerman.According to them, this type of fluoride-
exchanging resin should maintain its physical properties,
since the fluoride is given up in exchange for other anions.)

• RESIN MODIFIED GIC , HYBRID GIC &
CONVENTIONAL COMPOSITE
• Foley & Mamandras (AJO 2001 Jan) The objective
of this study was to compare 3 orthodontic adhesives in
the areas of shear-peel bond strength, location of
adhesive failure, and extent of enamel cracking before
bonding and after debonding of orthodontic brackets.
• The adhesives included a composite resin control
(Transbond XT)
• A resin-modified glass ionomer cement (Fuji Ortho
LC)
• A polyacid-modified composite resin( GIC HYBRID)
under dry and saliva-contaminated conditions (Assure).

1.Transbond XT displayed significantly greater shear peel bond strength than Fuji
Ortho LC and Assure, although the bond strengths for all 3 adhesives were clinically
acceptable.
2. There was no significant difference in mean shear-peel bond strengths between
Assure-wet (saliva-contaminated) and Assure-dry (non-contaminated) protocols.
3. Fuji Ortho LC and Assure-wet tended to display adhesive failure at the
enamel/adhesive interface while Assure-dry and Transbond XT tended to display
cohesive failure within the adhesive.
4. The greatest frequencies for enamel fracture upon debonding occurred in the groups
showing the highest bond strengths (Transbond XT and Fuji
Ortho LC). www.indiandentalacademy.com

• Adhesives that Bond Chemically to Metal
• During the 1980's, primers such as Fusion and
adhesives such as Enamelite 500 and Goldlink
were introduced for bonding to gold and dental
metal alloys, they were not very effective.
• Attachments are then bonded with highly filled
adhesives (e.g. Concise) to the metal.
• 2 different types of adhesives, 4-META resins
and 10-MDP Bis- GMA resins have recently
been developed to improve adhesion to metals.

Intermediate Resins to Enhance Bond Strengths
All-Bond 2 and Scotch bond MP (Multipurpose) are the most
popular and complete intermediate resins available today.
All-Bond 2
A third generation dentin-bonding agent contains a 10%
phosphoric acid gel for dentin conditioning. One drops
each of Primer A and Primer B are mixed and applied to
the enamel until the acetone solution evaporates. The site is
then air dried for 5 to 10 seconds. All-Bond 2 can be used
to increase the strength of any adhesive by this method.
Primer B is claimed to be an effective metal primer when
repairing a porcelain-metal crown or bonding a metal-based
restoration.

• Bonding to Amalgam
• Amalgabond (Super-Bond D Liner) is a 4-META
resin that bonds to amalgam, as do Super Bond C
& B. This cures in 60 seconds.
• All Bond 2 and Amalgabond can be used during
initial placement. Scothbond MP - Should be used
only on hardened, Sandblasted amalgam .
• Another 4-META intermediate resin that will
enhance bond strength to artificial tooth surfaces
and has a short polymerization time (30 seconds) is
Reliance Metal Primer.
• Therefore Amalgabond plus or Reliance Metal
Primer can be used as an intermediate application
before bonding with composite resin to amalgam

• Bonding to glazed porcelain with the assistance of a
coupling agent (Silane) as an interface between the porcelain
and the bonding agent. Silanes are recognized as coupling
agents for bonding glass fillers intc polymers. Studies have
shown that silane coupling agent will increase the adhesion of
resins to dental porcelain.
• Silane also helps in bonding brackets to composite prosthetic
restorative material (Isosit), a heat cured composite resin.
• The silane solution is prepared according to the protocol
presented in the work of Chen and Brauer. It contains.
• 5% Vol of silane (gamma - methacryloxypropyl
methoxysilane)
• 2% wt% of n-propylamine, in acetone
• eg : Ormco Porcelain primer, Scotch prime ,Clearfill
porcelain bond
• The bond strength produced by this method is apparently
inadequate for orthodontic purposes.

• High-Q-Bond (HQB)
• HQB is a dentin-bonding agent that belongs to the
fourth generation of dental adhesives.
• It is composed of acrylic monomers
methylmethacrylate (MMA) crosslinked with a
multifunctional agent, an adhesion promoter a co-
monomer-aliphatic polyester and initiators for
selfcuring process (dimethyl-P-toluidine and Benzoyl
peroxide). It also includes poly MMA, inorganic
fillers and coupling agent.
• HQB provides high tensile bond strength and can be
used for bonding to various substrates such as
enamel, noble and base metal alloys, amalgam,
composite and porcelain.

• Degradation of Polymeric Systems
Degradation of high polymers can be character-ized into two
broad areas:
Random,
Where chain rupture is induced by one or more factors" such
as exposure to ozone, oxygen. ultraviolet radiation, and
foreign agents. This type of degradation occurs at random
sites in the polymer structure, resulting in the release of large
structural fragments.
Chain depolymerization, where release of monomer occurs
in a more organized man-ner (depropagation).
Depropagation is virtually the reverse of polymerization
where bond breakage is initiated at a chain defect site and a
hydrogen atom is released from the polymer structure. The
polymer chain then splits, and both a free radical and an
inactive species are created.

Carbon double bond unsaturation (C = C )
Water sorption
Composite resin solubility
Micro cracks
Diffusion channels
Degradation process.
Bacteria
& enzymes

• Munksgaard and Freud demonstrated the occurrence of
enzyme-induced degradation of di-methacrylate polymers
and the hydrolytic nature of the process.
• Their work was preceded by experiments in several polymer
systems that consistently showed enzymatic activity-
induced degradation of the materials.
• Initially, the applicability of these laboratory results to the
clinical situation was questioned: Investigators claimed that,
under clinical conditions; the' composite resin is covered by
a proteinaceous film (pellicle) that masks the surface layer
presumably decreasing its reactivity with the environment
and any subsequent attraction and adsorption of molecular'
complexes. Such adsorbed substances might affect' the
'enzymatic activity of adjoining resin molecules in an
unpredictable manner.

• However, Matasa has demonstrated that
aerobic and anaerobic microbial activity
'may weaken the resin, leading to
compromised bond strength. These effects
were attributed to the ability of some
microbes to metabolize adhesive
constituents. A suggestion was made to
incorporate substances in the adhesive with
bactericidal activity similar to the approach
of including gentamycin in bone cements
(PMMA-based) intended for use in total hip
replacement arthroplasties.

• Leaching of Orthodontic Adhesives
• Water immersion has been reported to cause release of 50% of
the leachable species while ethanol-water immersion accelerated
the release rate to 75 % from dental resins during the first three
hours.
• Ferracane and Gordon were unable to detect further elution from
composite resins after 24 hours of immersion.
• In contrast, other investigators found prolonged elution from
composite resins and orthodontic adhesives Which continued for
115 days and two years, respectively.
• Ethanol-water baths tend to accelerate the degradation of
composite resins when compared, to water immersion, and also
promote elution of leachable species.
• The quan-tity and composition of the eluted substances are key
factors for the toxic potential of a resin adhesive. In general the
maximum accepted weight loss of restorative material has been
stipulated at 5microgram /mm3. Filler components (mainly
silicon) have been estimated to account for approxi-mately 180
micro mol/g weight loss.

• Eluted substances include fillers, enzymatic
hydrolysis-induced methacrylic acid, benzoic acid
resulting from degradation of the benzoyl
peroxide initiator, and materials probably
originating from the polymerization accelerators
and catalysts.
• A serious concern arises from the formation of
formaldehyde (H2C= 0) as an oxidation reaction
product of oxygen with the carbon-carbon double
bonds , Oxygen is capable of detaching the
pendant group from the polymer network, leading
to structural degradation.

• AJO1995 Sep Eliades and Brantley in their study of residual
monomer leaching from three adhesives showed that
• 1. No statistically significant differences in the amount of
released monomers were found among the ceramic bracket
groups bonded to the visible light-cured adhesive and photo
polymerized under direct or indirect irradiation.
• 2. The polycarbonate base ceramic bracket demonstrated
significantly higher amount of released monomers compared
with ceramic brackets. Evidence of degradation of the
polycarbonate base was detected.
• 3. The highest amount of residual monomers was eluted from
the chemically cured adhesive group. The visible light-cured
adhesive bonded to the stainless steel brackets under indirect
irradiation showed values comparable to ceramic brackets,
while direct irradiation resulted in high amount of eluted
monomers.

• CYTOTOXICITY
• – Davidson et al ( 1983 AJO)
• Orthodontic bonding materials were tested for in vitro cytotoxicity
by an agar-diffusion cell culture technique. Vero cells were grown
in a monolayer, covered with an agar/medium overlay, and exposed
to equal amounts of orthodontic adhesives immediately after
polymerization and at various time periods up to 30 days after
mixing. The diameter of the area of unstained, nonviable cells (zone
of inhibition) provided a quantitative measure of toxicity.
• All materials were found to show cytotoxicity immediately after
preparation, with the activator components of two "no-mix"
materials exhibiting significantly higher toxicity than other
materials tested. Polymerized adhesives generally showed decreased
toxicity following soaking in saline solutions which simulated the
bathing of materials by intraoral fluids. The sealant materials
showed statistically significant greater toxicity than paste resins,
both initially after mixing and after 30 days.
• The significant finding in this study was that these materials not
only were toxic immediately after mixing but remained toxic for
extended periods of time. Excess material should be removed from
teeth by thorough scaling and flushing with water and high-speed
evacuation, particularly in areas adjacent to the gingiva.

1. Cytotoxicity of direct-bonding adhesives –
Davidson (AJO 1988 May )in their study
showed that different direct bonding adhesives
were toxic to varying degrees in vitro and that
toxicity decreased more rapidly for some
adhesives than others. Although these results do
not necessarily translate to any direct toxic
effects on patients, they do indicate that this
technique can detect a potential long-term toxic
effect in orthodontic adhesives, which should
warrant further prudent in vivo animal model
testing.

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