Recent research findings in orthodontic bonding /certified fixed orthodontic courses by Indian dental academy

Recent Research findings in
Orthodontic Bonding Materials
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Direct bonding of orthodontic attachments to
teeth with the use of epoxy resins was
introduced in 1950s and the use of BIS GMA in
the mid 1960s.
Acid-etching technique in the 1950s to bond
dental restorations to tooth structure was the
breakthrough point in the history of orthodontic
bonding.
The basis for the adhesion of brackets to
enamel has been enamel etching with
phosphoric acid, as first proposed by Buonocore
in 1955.

In the past few years, there has been a
major research drive to increase bond
strength between dental materials and
dental hard tissues, although most of the
adhesive systems have provided clinically
acceptable bond strengths.
Achieving a low bond failure rate should
be a high priority objective – replacing
loose brackets is time consuming, costly.

Continuous search is on for higher bond
strengths, better adhesives and materials
that will bond in presence of saliva.
There is a need to improve the bonding
procedure to maintain clinically useful
bond strengths while minimizing the
amount of enamel loss and to simplify the
technique reducing the number of steps


In the past decade, one has witnessed
unprecedented progress in bonding to
enamel with various materials techniques
and auxiliaries involving glass ionomer
bonding, self-etching primers, and new,
powerful light-curing sources, along with
self-ligating brackets and a different
treatment concept, the Invisalign
technique.

This distinctive pattern of progress can be attributed
to the fact that the specialty’s armamentarium largely
depends on the advancement of technology in various
materials science fields and in other dental specialties
for the development and application of new materials.
For example, the emergence of nanotechnology and its
growing application in industry has influenced the
manufacture of composite resin by introducing nanofilled
composites


Enamel preparation: acid etching, Crystal
growth,
laser, or air abrasion?
Duration of etching – Studies and clinical
experience indicate that 15-30 sec is probably
adequate for etching most young permanent
teeth.( Brannstrom 1978,1982, Newmann 1982,
Wang 1991)
There is no evidence that indicates any
significant increase in bond strength between 15
and 90 sec of permanent tooth etching.
(Barkmeier et al 1987, Osorio et al 1999)

If tooth is etched for more than 90 sec – an insoluble
calcium phosphate salt crystals forms on the enamel that
is impervious to rinsing, resulting in reduced bond
strength.
Type of etchant – Etching with 10% or 37% phosphoric
acid produces the highest bond strengths (28Mpa) –
Brantley & Eliades 2001.
Gardner & Hobson (2001) documented that enamel
etching with orthophosphoric acid provides similar bond
strength with much lower acid concentrations than the
original 37%.

Wang and colleagues ( Angle 1994) evaluated several
phosphoric acid concentrations from 2% to 80% and
found that best bond strength was achieved with 30%40% concentrations.
Among the other techniques and materials tried, the most
prominent was the Crystal growth system.
This method, originally developed by Maijer and Smith at
the University of Toronto, attempted to reduce the depth
penetration of treatment into enamel. (Maijer & Smith,
AJO1982)


It involves use of polyacrylic acid solution
containing sulfate ions, which causes growth of
calcium sulfate dihydrate crystals on the enamel
surface.
These crystals in turn retain the adhesive.
Bond strength was found to be 60-80% less than
with conventional acid etching. (Artun &
Bergland AJO 1984, Farquhar AJO 1986 , Read
EJO 1986)

Use of 10% maleic acid for etching resulted in a
lower bond strength.( Powers & Kim, Semin
Orthod 1997)
Another technique – micro etching with small
intraoral sandblasters. Takes about 3 seconds.
They use 50µm white or 90µm tan Aluminium
oxide powder connected to a compressed air
source in the operatory. Operates at about
7kg/cm2 optimum pressure.
If patient is allergic to Aluminium oxide – Silicon
carbide can be used.

Composite to metal adhesion can be improved
by atleast 300% with intraoral sandblasting.
Highly effective in bonding to gold and other
metals, as well as porcelain.
Other clinical applications – Removal of
composite from loose brackets before
rebonding.
Increasing the retentiveness of stainless steel
bands.

Sandblasting without acid etching produces
lower bond strength than conventional acid
etching and consistently results in bond failures
at enamel adhesive interface.( Olsen M, Bishara
SE AJO 1997, Reisner AJO 1997).
Reisner (1997) also reported that sandblasting
followed by acid etching produces bond
strengths comparable to or higher than acid
etched enamel.

D.N Kapoor, V.P. Sharma, Pradeep Tandon, Kamlesh
Pandey: Comparative evaluation of Tannic acid, Citric
acid and phosphoric acid as etching agents for direct
bonding (JIOS 2002)
Concluded that: 1) Application of 37% phosphoric acid for
15 seconds produced comparable etching topography
when 50% tannic acid was applied for 90 seconds.
2) Assessment of penetration depth revealed that 37%
phosphoric acid dissolves more enamel than tannic acid
or citric acid


3) 1 min application of 50% citric acid did not
result in attainment of adequate bond strength.
4) 50% Tannic acid when applied on enamel for
90 sec provided the tensile bond strength closer
to 37% phosphoric acid.
So 50% Tannic acid could be an alternative to
phosphoric acid for etching as it dissolves lesser
amount of enamel and at the same time
provides similar tensile bond strength.


Laser etching – Application of laser
energy to an enamel surface causes
localized melting and ablation.
Removal of enamel (etching) results
primarily from the micro-explosion of
entrapped water in the enamel.
In addition, there may be some melting of
hydroxyapatite crystals.


Laser etching of enamel by Nd: YAG laser
typically produces lower bond strengths
than does acid etching. ( MacDonald et al
JDR 1994)
Carbon dioxide laser etching of enamel
have shown that bond strengths of 10
MPa can be obtained reliably. (Ma T &
Flint W AJO 1997).


Self etch adhesive systems
New bonding systems were developed to
combine conditioning and priming agents
into a single acidic primer for
simultaneous use on enamel, eliminating
steps of separate etching, rinsing, and
drying.
The use of a self-etching primer (SEP)
would have the advantage of a faster and
simplified application technique, allowing
adequate etching and priming of enamel
in only one step.

In addition to saving time, fewer steps in
the bonding process might translate into
fewer procedural errors, minimizing
technique sensitivity.
Ex- First Step (Reliance Orthodontics, IL)
Transbond Plus ( 3M Unitek, CA),
Ideal 1 ( GAC Orthodontic products, NY)
Prompt L-Pop (3M ESPE, Seefeld,
Germany)

The Active ingredient of the self-etching primers
(SEPs) is a methacrylated phosphoric acid ester
that dissolves calcium from hydroxyapatite.
Rather than being rinsed away , the removed
calcium forms a complex and is incorporated
into a network when the primer polymerizes.
Etching and monomer penetration to the
exposed enamel rods are simultaneous, and the
depth of etch and primer penetration are
identical.


Acidic primer solutions also demineralize the
dentin and encapsulate the collagen fibers and
hydroxyapatite crystals.
This simultaneous conditioning and priming
allows penetration of the monomer into the
dentin. The adhesive resin component will
then diffuse into the primed dentin, which
produces a “hybrid layer.”

The etching process is stopped by 3
mechanisms:
1.The acid groups attached to the monomer are
neutralized by forming a complex with calcium
from hydroxyapatite.
2.As the solvent is driven from the primer
during the airburst step, the viscosity rises,
slowing the transport of acid groups to the
enamel interface.
3. As the primer is light cured and the primer
monomers are polymerized, transport of acid
groups to the interface is stopped.

Clinical use of Self etching Primers:
1.Dry the tooth surface.
2. Apply Self etching primer.
It consists of three compartments.
a) contains methacrylated phosphoric acid esters,
photosensitizers, and stabilizers.
b) water and soluble fluoride.
c) Applicator microbrush


Squeezing and folding the first compartment
over to the second activates the system.
The mixed component then is ejected to
the third to wet the applicator tip.
3) Bond the bracket with composite and
cure with light.


Bishara et al (AJODO 2001) evaluated the
effectiveness of using Prompt L-pop (ESPE,
Seefeld, Germany) to bond orthodontic brackets
with composite resin.
According to the results, this SEP provided
significantly lower (but clinically acceptable)
shear bond strength (mean, 7.1 ± 4.4 MPa) when
compared with a conventional etch/priming
technique before bonding brackets with
Transbond XT adhesive paste (3M Unitek,
Monrovia, Calif).

Arnold et al (AJODO 2002) compared the
shear bond strengths of metal brackets
bonded with Transbond Self Etch Primer
and conventional acid etch technique.
They found no significant difference in the
bond strength obtained with the two
techniques.


Cal-Neto and Miguel (Angle Orthod 2006) did a
Scanning Electron Microscopy evaluation of the
bonding mechanism of Transbond Self-Etching
Primer on enamel.
Compared with phosphoric acid, Transbond Plus
SEP produced a uniform and more conservative
etch pattern, with regular adhesive penetration
and a less aggressive enamel demineralization.
The resin tags were shorter than those observed
in control group.

Enamel etching patterns with phosphoric acid and
Transbond SEP


A new product Adper Prompt L-pop (3M ESPE,
St Paul, Minn), was introduced to improve
enamel and dentin bond strengths.
Adper Prompt contains different percentages of
the same components as the original Prompt Lpop.
The manufacturer claims that maximizing bond
strength has been achieved, in part, by
optimizing the relative amounts of nonacid
functional methacrylates with acidic
methacrylated phosphoric esters.

Adper Prompt also introduces better
activation control and other chemical
modifications enhancing a uniform
adhesive film, improving the quality of
hybridization between the adhesive and
the enamel surface.


Cal-Neto et al (Angle Orthod 2006) found no
difference in bond strength whether a
conventional etching and primer or Adper
Prompt L-pop was used. (16.24 and 13.56 Mpa
respectively)
The amount of adhesive on the enamel after
debonding was significantly less when using
Adper Prompt than when using phosphoric acid.
Their results indicated that Adper Prompt is
potentially adequate for orthodontic bonding
needs.

However in study by Zafer C Cehrell (AJODO 2005)
where 4 self etch primer system { Prompt L Pop, Clearfil
SE Bond, FL Bond, One Up Bond } ,
a non rinse conditioner and acetone based adhesive
system ( Prime & Bond NT ) and conventional adhesive
Transbond XT were assessed for shear bond strength.
Shear bond strength of all 5 experimental groups were
all significantly lower than that of Transbond XT, but not
different from one another. ( Range of 1.72 ± 0.13 to
1.77 ± 0.14 MPa).
Transbond XT – 10.5 ± 0.86 MPa.


Difference from other studies –
a) Bonding done on intact enamel instead of
ground enamel surfaces.
b) Lack of thermal agitation which effects bond
strength.
C) Biodegradation of the adhesive & composite
as a result of immersion in water or exposure to
oral fluids leading to decreased bond strength
values over time. In present study specimens
were stored in water for 6 weeks and the water
was changed every week.

K.House & A.J. Ireland ( J.O. 2006)
assessed the in vivo bond failure of the
single component self etching primer
system Ideal 1 ( GAC Orthodontic
Products) & compared it with the
conventional acid etching using a 37%
phosphoric acid.
Total of 339 teeth were bonded with Ideal
1 and failure recorded at 1,6 & 12 months.

The study found that enamel pretreatment
with Ideal self etching primer system
results in an unacceptably high bond
failure rate ( 72.4% at 12 months)
compared to conventional acid etching
(14.8% at 12 months).


Self-etching Primers: Is Prophylactic Pumicing
Necessary? A Randomized Clinical Trial
Antonia M. Burgessa; Martin Sherriffb;
Anthony J. Ireland ( Angle 2006)
The purpose of this clinical trial was to determine
whether pumice prophylaxis is required before
the use of a self-etching primer (SEP).
Data on bond failure were collected at 6 and 12
months after appliance placement.
Very high bond failure rates of 55.5% for the nopumice group and 33.2% for the pumice group,
were recorded.

This randomized, cross-mouth clinical trial suggests
that the omission of pumice prophylaxis before orthodontic
bonding with a SEP has a significant effect,
leading to an increased bond failure rate.
However, with the First Step SEP used in this clinical
trial, the observed clinical bond failure rates were still
unacceptably high at 33.2%, such that this material
cannot be recommended for clinical use.


Moisture insensitive primers
Ex – Transbond MIP ( 3M Unitek, CA) ,
Assure ( Reliance Orthodontics, IL),
Ortho Solo Universal Bond Enhancer (Ormco/”A”
Company, CA).
The main reactive component of this product is a
methacrylate-functionalized polyalkenoic acid
copolymer originally used in dentin bonding systems.
Excess interfacial water ionizes the carboxylic acid
groups forming hydrogen bonded dimers.

In addition, a reversible breaking and reforming of
calcium polyalkenoic acid complexes with enamel is
established, providing some stress relaxation
capacity.
Thus, a dynamic equilibrium occurs at the
interface, incorporating water in the the bonding
mechanism.
This minimizes the detrimental plasticizing effect
of water that occurs with moisture contamination
of conventional bonding agents.

Schaneveldt and Foley (AJODO 2002) evaluated the
effectiveness of 2 moisture-insensitive primers,
Transbond MIP (3M Unitek, Monrovia, Calif) and Assure
(Reliance Orthodontic Products, Itasca, Ill) and
compared them with a control hydrophobic primer,
Transbond XT (3M Unitek).
Both bonding systems provided adequate bond
strengths whether saliva contamination occured before
or after the application of the hydrophilic primers.
Therefore, additional mechanical preparation and reetching of the enamel surface after saliva contamination
would not be required


The hydrophilic resin sealants or primers
polymerize in the presence of a slight amount of
water, but they will not compensate routinely for
saliva contamination.
When bonding to enamel, one must place the
resin sealant or resin primer onto the prepared
enamel before the pellicle (biofilm) from the
saliva, This is crucial for a successful bond.

Ashima Valiathan, Ashil A.M. Kerala Dental
Journal 2006 (In press) studied the efficacy of
Transbond Moisture insensitive primer in vitro, in
the dry state and in the presence of saliva and
compared it with conventional Transbond XT.
It was found that in the presence of salivary
contamination,
brackets
bonded
using
Transbond MIP gave significantly higher bond
strength (14.53 Mpa) as compared to brackets
bonded with conventional primer (9.36 Mpa)


Moisture active adhesives
In contrast to MIP’s, these require rather than
tolerate the presence of moisture for proper
polymerization.
These materials are available as pastes and
possess a completely different composition and
polymerization mode, requiring no bonding
agent.
A recent product based on a cyanoacrylate
formulation (Smart-bond, Gestenco Intl AB,
Sweden) has demonstrated superior properties,
excellent in vitro performance and easy clinical
application without the need for etching and
liquid resin coating.

Setting reaction:
1. Isocyanate group + Water
carbamic acid component

Unstable

CO2 + Amine
2. Amine + residual isocyanate groups
Crosslinking of adhesive through substituted urea
groups.

Bishara et al (AJODO 2003) reported that
Smartbond cyanoacrylate adhesive has
adequate bond strength 24 hours after
initial bonding, but its strength decreases
by 80% after thermocycling between 5°C
and 55°C


Srivastava A; Gorantla S; Valiathan A. (TIBAO
2002) compared the bond strength of two
indigenously developed cyanoacrylates (N-Butyl
cyanoacrylate and Isoamyl-2-cyanoacrylate) with
a conventional self-cured composite (Right On).
The results showed that although the initial bond
strength of N-Butyl cyanoacrylate was higher
than the control composite, it deteriorated when
stored in physiologic saline for 48 hours.


Isoamyl-2-cyanoacrylate had significantly
lower bond strength when compared to
the other samples in all the three groups
under study.
This study showed the need for further
work to be done with cyanoacrylates to
decrease their bio-degradability, so that
they can be clinically useful in
orthodontics.

James Sunny P, Valiathan A (TIBAO 2003)
performed an in vitro study to compare shear
bond strengths of brackets bonded with Smart
Bond and with a conventional composite (RightOn) respectively.
Measurements were performed at 1 hour (dry),
24 hrs and 48 hrs (in artificial saliva).
Composite showed higher bond strength than
cyanoacrylate at all time intervals.
Smartbond achieved a maximum bond strength
of 5.07 Mpa at 24 hours, which declined at 48
hours.
The authors concluded that Smartbond might
not be a better option for bonding compared to
conventional composite.

Resin modified glass ionomer cements
Ex - Fuji Ortho LC ( GC America, IL).
Research has however demonstrated poor bond
strength with GICs, about 2.4 to 5.5 MPa, by using
either phosphoric or polyacrylic acid.
GICs also have a greater bracket detachment rate than
composite resin systems. with the addition of a small
amount of light-activated resin, many of the poor
early physical and mechanical properties of GIC
could be improved.


These improvements were incorporated in the
material known as resin-modified glass
ionomer (RMGIC) cement.
Wide variations of bond strengths of RMGIs
to enamel have been reported in the
orthodontic literature— from 5.4 to 18.9 MPa.


A study comparing the bond strength between an
RMGI and a composite resin reported bracket failure
rates of 5% for RMGI and 8.3% for composite.
(Fricker, AJODO 1998).
In a Randomized controlled clinical trial by Gorton
& Featherstone ( AJODO 2003) the quatitative
microhardness tests of teeth bonded with Fuji Ortho
LC showed significantly less mineral loss compared
with teeth bonded with light cured composite resin
( Transbond XT).


Pretreatment with polyacrylic acid
facilitates a chemical bond between the
Glass ionomer and the enamel and thus
should be performed before bonding with
Glass ionomer.
RMGIC are also material of choice when
bonding in situations of extreme wetness
like in second molar region.

Sarin Koyal and Valiathan A ( JPFA 2003)
compared the bond failure rates of Fuji Ortho LC
and Transbond XT clinically using a split mouth
technique, over a period of 6 months.
The study revealed that Transbond XT and Fuji
Ortho LC had a comparable bond failure rate .
There were no significant differences in the
plaque and gingival index in the two groups.
They concluded that Fuji Ortho LC is a suitable
alternative for orthodontic bonding.

Poly acid modified resins (Compomers)
Polyacid-modified composite resins, also known as
compomers, were developed to bring the features of caries
inhibition and carboxyl chelation to resins.
Compomers are single-component systems consisting of
aluminosilicate glass in the presence of carboxyl modified
resin monomers and light-activated conventional resin
monomers.
After light-activation of the compomer, it is postulated that
water sorbs into the compomer, allowing a delayed acid-base
reaction that may release fluoride and other remineralizing
ions from the aluminosilicate glass.

Compomer bonding studies have failed to confirm the
chelation of carboxyl groups to enamel or dentin.
The fluoride release from compomers is lower than
that from GICs but higher than that from resins.
Fluoride recharging and caries inhibition of
compomers have been reported.
Their early setting strengths are superior to those of
the RMGICs but inferior to those of the resin
adhesives.
Example: Dyract AP.


Giomers
A new category of fluoride-containing esthetic
restorative material has recently been
introduced to the dental profession.
The giomer uses prereacted glass ionomer
technology to form a stable glass ionomer
phase in the material.
This differs from compomers in which the
fluoroaluminosilicate glass particles do not
react until water is taken up into the
restoration.

Both giomers and compomers require a resin
bonding system after acid etching.

Manufacturers of giomers claim fluoride
release, biocompatibility, and smooth surface
finish.


Chitnis et al (AJODO March 2006) compared the shear
bond strength of orthodontic brackets bonded to tooth
enamel with 4 adhesives: a commercially available
giomer material, a polyacid modified composite resin, a
resin-modified glass ionomer and a standard resin-based
composite adhesive.
The conventional Resin cement and the RMGI cement
provided significantly higher orthodontic bond strengths than
the Poly Acid modified composite resin and the giomer
materials when attaching metal brackets to tooth enamel.
The authors concluded that current RMGI orthodontic cements
might provide acceptable bond strengths.


Ormocer
Ormocer is an acronym for organically modified
ceramic technology.
Ormocer materials contain inorganic-organic
copolymers in addition to the inorganic silanated
filler particles.
It is synthesized through a solution and gelation
processes (sol-gel process) from multifunctional
urethane and thioether(meth)acrylate
alkoxysilanes.
Ormocers are described as 3-dimensionally
cross-linked copolymers.

Ajlouni, Bishara et al (Angle Orthod 2004)
compared the shear bond strength (SBS) of an
Ormocer (Admira)with Transbond XT (3M
Unitek, Monrovia, Calif).
The mean SBS for Admira was 5.1 MPa and that
for Transbond XT was 4.6 MPa.
It was concluded that the new material,
Ormocer, which is an organically modified
ceramic restorative material can potentially have
orthodontic applications if available in a more
flowable paste.

Advantages of Ormocer :

1. No residual monomer content
2. Coefficient of thermal expansion similar

to natural tooth strucure

3. Significantly lower wear rate
4. Protection against caries

Recent innovations also include the
development of light activated color change
adhesives which help identify excess adhesive
for removal during the bonding procedure.
A new fluorescing adhesive paste ( Pad Lock,
Reliance Orthodontics, IL) discloses not only the
flash produced at bracket placement, but the
adhesive remnants left after debonding &
cleanup.

Pro-Seal (Reliance Orthodontics, IL) is a fluoride
filled , light cured sealent with a propietary
catalyst that sets the resin without an oxygen
inhibited layer.
Its complete polymerization prevents oral fluid
absorption & reduces toothbrush abrasion.
It can inhibit long term decalcification ,even in
patients with poor oral hygiene.

Manal M. Soliman Samir E. Bishara ( Angle
2006)
measured the rate and amount of fluoride ions
released from the sealant over a period of 17
weeks and determined whether the fluoridereleasing sealant has a recharging ability when
fluoride ions are reintroduced into the
environment.
Disc-shaped specimens were prepared from two
types of sealants: (1) 10 discs were made using
a fluoride-releasing sealant (Pro-Seal)
and (2) 10 discs were made of a nonfluoride
adhesive primer (control).

The results indicated that the fluoride-containing
sealant released fluoride ions into the solution in
sustained but significantly decreasing rates from
a at the end of the 17th week.
Furthermore, the Pro Seal discs had the ability to
be recharged with fluoride ions introduced from
a foaming solution of acidulated phosphate
fluoride.

Newer self-adhesive cements have the potential
to further simplify the bonding process, that is,
by reducing the process of bonding orthodontic
brackets to a one-step procedure.
RelyX Unicem (3M ESPE, Seefeld,
Germany), a self-adhesive universal cement, has
proven to have many desirable properties, which
have made it the adhesive material of choice in
many dental procedures

Bishara et al (2006, Angle Orthod) did a study on
whether a self-adhesive universal cement,
RelyX Unicem (3M ESPE, Seefeld, Germany),
can be used successfully to bond orthodontic
brackets to enamel.
Materials and Methods: Forty human molars
were cleaned, mounted, and randomly divided
into two groups: 20 orthodontic brackets were
bonded to teeth using RelyX Unicem, and 20
brackets were bonded using the Transbond XT
(3M Unitex, Monrovia, Calif) adhesive system.

Results: The mean bond strength of the brackets
bonded using the RelyX Unicem was 3.7± 6 2.1
MPa and was significantly lower than the
brackets bonded with the
Transbond system ( 5.97 ± 4.2 MPa).

Conclusions: The Shear bond strength of the
self-adhesive universal cement needs to be
increased for it to be successfully used for
bonding orthodontic brackets.


Bioactive adhesive systems with antibacterial
effects or intensive remineralizing ability are
considered beneficial and capable of superior
clinical performance as a direct strategy to
eliminate the cause of caries.
Clearfil Protect Bond ( Kuraray, Osaka, Japan) is
a new fluoride releasing antibacterial bonding
agent , combines the physical advantages of
dental adhesive technology and antibacterial
effect.

Clearfil Protect Bond contains
12methacryloyloxydodecyl-pyridinium bromide
(MDPB) which is an antibacterial monomer. It
copolymerizes with other monomers after curing
and is covalently bonded to the polymer
network.
Does not leach from surface but acts as a
contact inhibitor against the bacteria that attach
to the surface.

Arhun N et al ( AJODO 2006) compared
Clearfil Protect bond with Adper Prompt L
Pop and Transbond Plus SEP to assess
the bond strength.
Adper Prompt L Pop – 9.6 ± 4.00 MPa
Clearfil Protect bond – 13.8 ± 4.32MPa
Transbond Plus SEP – 6.3 ± 2.86MPa


Similarly incorporation of 2.5%
Cetylpyridinium chloride (antiplaque
agent) in adhesives have been found to
impart antimicrobial activity without
altering diametral tensile strength.
( Tahani A. Al-Musallam et al AJODO
2006).


Effect of bleaching
The recent popularity of tooth whitening or bleaching has
had a significant impact on the practice of dentistry .
In 1989, the first at-home “night-guard” bleaching system
using carbamide peroxide was introduced by Haywood
and Heymann.
Since then, bleaching has became more accessible to
dentists, patients, and the population at large, with
bleaching materials and paraphernalia available in overthe-counter kits and special and regular toothpastes. Athome bleaching products, with a few exceptions, contain
carbamide peroxide in varying concentrations, from 5%
to 30%.

Bishara et al ( AJODO 2005) determined the effect of
enamel bleaching on the shear bond strength of
orthodontic brackets bonded with a composite adhesive.
In the at-home bleaching group (n = 30), Opalescence
bleaching agent (Ultradent, South Jordan, Utah), which
contains 10% carbamide peroxide, was brushed onto the
teeth daily for 14 days and left for 6 hours each day.
Teeth in the in-office group (n = 30) were treated with
Zoom! (Discus Dental, Culver City, Calif), which contains
25% hydrogen peroxide gel and then exposed to a light
source for 20 minutes; these teeth were treated twice.


After bleaching, the specimens were randomly divided
into equal subgroups and stored in artificial saliva at
37°C for 7 or 14 days before bonding. Shear bond
strength testing was performed on all teeth..
Results: The mean shear bond strength for the control
group was 5.6 ± 1.8 MPa. Means for the at-home groups
were 5.2 ± 3.6 MPa and 7.2 ± 3.2 MPa for the 7- and 14day waiting periods, respectively. Means for the in-office
groups were 5.1 ± 5.3 MPa and 6.6 ± 2.6 MPa for the 7and 14-day waiting periods, respectively.
Conclusions: The results showed that in-office and athome bleaching did not affect the shear bond strength of
orthodontic brackets to enamel.

Bulut et al ( EJO 2006) in their study
concluded that brackets bonded
immediately after bleaching revealed
significantly lower tensile bond strengths.
However antioxidant treatment
immediately after bleaching was effective
in reversing the tensile bond strength of
brackets.


Bishara et al ( Angle 2005) did a study to
determine whether the use of an iodine
compound for disinfecting the waterlines in
dental units has an effect on the shear bond
strength of orthodontic brackets bonded to
enamel.
Forty molar teeth were divided randomly into two
groups—
group 1 control: twenty teeth were etched for 15
seconds with 35% phosphoric acid, washed with
a distilled water spray for 10 seconds, stored in
distilled water for 5 minutes, dried to a chalky
white appearance, and the sealant applied to the
etched surface;

group 2 experimental: twenty teeth were
etched for 15 seconds with 35%
phosphoric acid and washed for 10
seconds with water containing iodine.
The teeth were stored for five minutes in
the iodinated water, dried to a chalky white
appearance, and the sealant applied to
the etched surface as in the control group.


All teeth were debonded within 30 minutes from
the initial time of bonding.
Results indicated that there were no significant
differences in the shear bond strengths of the
teeth that were washed and immersed in the
iodine solution and the control group in which
distilled water was used.
The mean shear bond strengths for the two
groups were 6.5 ± 3.5 MPa and 4.7 ± 3.1 MPa
respectively.

Dental flowable Composite
Among the composite resins that could be used
in orthodontics as bonding agents today,
flowable composite merits great attention
because of its clinical handling characteristics.
Flowable composites show two desirable
clinical handling characteristics that have not
existed for composites until very recently:
(1) nonstickiness, so that materials could be
packed or condensed, and
(2) fluid injectability.

Flowable composites were created by
retaining the same small particle sizes of
traditional hybrid composites but by
reducing the filler content and allowing the
increased resin to reduce the viscosity of
the mixture. Ex - Denfil Flow (Vericom
Laboratories Ltd, Anyang, Korea), Dyract
Flow (DeTrey Dentsply, Konstanz,
Germany) .

Simona Tecco et al ( Angle Orthod 2005)
reported that the bond strength of Denfil Flow
(34.8 MPa) showed no significant difference with
the other control groups and was clinically
acceptable. Denfil Flow and Dyract Flow tended
to display cohesive failure within the adhesive.
Denfil Flow can be used without liquid resin to
reduce the bonding procedure time while
maintaining acceptable bond strength

Light Curing Units
In light-initiated bonding resins the curing process begins
when a photoinitiator is activated. Most commonly
camphoroquinone as the absorber, with the absorption
maximum in the blue region of the visible light spectrum
(480nm) .
Until recently, the most common method of delivering
blue light has been halogen-based light-curing units
(e.g., Ortholux XT, 3M/Unitek) The halogen lights can
cure orthodontic composite resins in 20 seconds and
light-cured resin-modified glass ionomers in 40 seconds
per bracket. This prolonged curing time is inconvenient
for the clinician and the patient.


So Fast halogens (e.g., Optilux 501 or
Demetron , California) have higher-output
lamps or even using turbo tips that focus
the light and concentrate it into a smaller
area can reduce the curing time to half of
the time needed with conventional
halogen lights.


Light emitting diode (LED), argon laser, and
plasma arc light-curing units have become
commercially available in recent years.
Although plasma and argon laser substantially
decrease the time required to reach comparable
bond strength with conventional halogen, these
lamps are costly, but the expense can be
partially cancelled by their longer lives.

Argon Laser:
They produce a highly concentrated beam of
light that is collimated. One interesting potential
of the argon laser is its ability to protect the
lased enamel surface against decalcification.
Recent studies have shown that argon laser
irradiation significantly reduces enamel
demineralization around orthodontic brackets.
(Noel 2003, Anderson 2002) .


Argon laser is an excellent light source
producing a peak wavelength of 488nm.
Offers rapid curing, improved physical
properties like hardness, tensile strength,
shear bond strength, degree of
polymerization.
Ex- AccuCure 3000 argon laser (Laser
Med, Utah)

Although the curing times could be
reduced to 5 seconds for unfilled and 10
seconds, their use in orthodontics is not
extensive, because of their high cost and
poor portability.


Plasma arc light: This light was introduced in
mid 1990s The lamp has a tungsten anode and
a cathode in a quartz tube filled with xenon gas.
When an electric current is passed through
xenon, the gas becomes ionized and forms
plasma made up of negatively and positively
charged particles and generates an intense
white light. This white light is filtered to blue
wavelengths, with a narrow spectrum between
430 - 490nm.

The conventional halogen lamps emit light
with an energy level of 300mW, the
plasma arc lamp has a much higher peak
energy level of 900 mW.
The advantage of the high-intensity light
is that the amount of light energy needed
for polymerization of the composite resin
can be delivered in a much shorter time.

About 3 to 5 seconds for metal brackets
( Sfondrini ME, Cacciafesta AJODO 2004)
, less than 3 seconds for ceramic
brackets (Klocke et al AJODO 2003)
This yields similar bond failure rates as for
brackets cured with a conventional
halogen light for 20 sec.


Light Emitting Diodes:
In 1995 Mills et al proposed solid-state LED technology
for polymerization of light-initiated resins to overcome
the shortcomings of conventional halogen lights.
LED curing of 20 and 40 seconds yielded statistically
similar results to curing of 40 seconds by conventional
halogen light sources.
New-generation LEDs with higher-intensity diodes may
shorten the curing times further e.g., the new Ortholux
LED by 3M/Unitek has recommended curing times of 10
sec for metal and 5 sec for ceramic brackets.


LED use junctions of doped
semiconductors to generate the light.
Wavelength of light emitted is about
470nm.
Ex- Bluephase LED ( Ivoclar Vivadent Inc,
NY),
Ortholux LED ( 3M/Unitek ,CA),
L.E. Demetron (Ormco/”A” company, CA),
Tu Tu ( American Orthodontics, WI)

Compared to LED halogen units work at
approximately 1% efficiency and are only 10%
efficient in converting electrical current into light.
LEDs have longer life spans of more than
10,000 hrs compared to 50 hrs for a halogen
bulb.
More consistent light output than Quartz halogen
lights.

Advantages: Light-emitting diodes are
small in size, are cordless, are quiet,
generate minimal heat, and perform
favorably compared with conventional and
fast halogen sources.


Side effect – Harmful effect on retina.
Blue light can form intracellular reactive oxygen
species, thereby affecting cell functions.
Wataha et al ( Dent Mater 2004) hypothesized
that, if the biologic effects of blue light are redox
mediated, antioxidants might be used to reduce
the undesirable effects on tissues during clinical
use,


Bikram S Thind & David R Stirrups ( EJO 2006)
compared tungsten quartz halogen, plasma arc
and LED light sources for polymerization of an
orthodontic adhesive and concluded that
polymerization as effective as conventional bulb
light sources was obtained with short exposure
times recommended for plasma arc or LED.
Similar results have been got for Argon laser
(Bryan S, Angle Orthod 2006) where it is
concluded that exposure time beyond 5 sec and
power setting beyond 150mW has no cumulative
effect on the shear bond strength of stainless
steel orthodontic brackets.

For effect of distance of light tip source on bond
strength ,Kimberly Gronberg ( Angle 2006) found
no effect in bond strength with the varying
distance of light tip from 1-10mm for source to
specimen distance for LED curing unit.
Hinoura et al (1993) had earlier confirmed the
same for lasers when distance increased to
1.5mm.

Bonding to Non conventional
surfaces – Adhesion Boosters
Bonding is more complicated in adult patients
than in adolescents. Many adults have crownand-bridge restorations made of porcelain or
precious metals, in addition to amalgam
restorations of molars.
Effective bonding of orthodontic brackets,
buccal tubes, and retainer wires to artificial
surfaces is now feasible, thanks to the
introduction of a wide variety of new techniques
and materials

Sandblaster
Tin plating – Improves bonding to noble metals.
Most commonly, the tin is electrolytically
deposited with a unit such as the MicroTin ( 3M
Unitek) or Kura Ace Mini (Morita USA Inc).
An alternative method is to rub on a solution of
gallium and tin (Adlloy) with a pure tin bar
(Nippon-Bashi Tokuriki, Japan).
Metal Surface is first sanblasted with 50µm
aluminium oxide.
Some organic tin compounds may be toxic

Adhesives that Bond Chemically to Metal –
Two different types of adhesives, 4-META resins
and 10-MDP bisGMA resins, have recently been
developed to improve adhesion to metals.
Super-Bond C&B ( Sun Medical Co. Ltd, Kyoto
Japan) also marketed as C&B Metabond is
activated by combining 4 META
(4-methacryloxyethyl trimellitate anhydrid) and
tributylborane monomers and then adding the
polymer powder to the activated liquid .

The polarity of the 4-META molecule is believed
to be the key to its bonding mechanism. The
molecule orients toward the oxygen or hydroxyl
groups in the metal layer and forms a hydrogen
bond.
Bond strengths of Super-Bond C&B to
sandblasted and tin-plated gold and to
sandblasted chromium-cobalt alloys are
reportedly more than 30 MPa, exceeding those
of conventional composites to acid-etched
enamel.

A clinical drawback of Super-Bond C&B is its
curing time of 10 minutes or more.
Panavia EX ( J. Morita USA Inc, CA) a filled
bisGMA resin, differs from other such adhesives
in that the monomer contains a phosphate ester
group (10-MDP, or 10-methacryloyloxydecyl
dihydrogen phosphate).
The bonding mechanism is not entirely
understood, but it apparently involves both
mechanical and chemical retention. MDP bonds
chemically to oxides of nickel, chromium, and
cobalt and to oxides of tin formed by tin plating.

Because Panavia requires an anaerobic
environment for complete setting, the bond
margins should be covered with a gel such as
Oxyguard after removal of excess adhesive.
In vitro studies show shear and tensile bond
strengths in excess of 30 MPa when bonding to
abrasive-sprayed base-metal alloys or tin-plated
noble alloys (Imbery 1993, Omura 1984)

Intermediate Resins to Enhance Bond Strengths
The most popular and complete intermediate
resins available today are All-Bond 2 (Bisco
Dental Products, IL) and Scotchbond MP (MultiPurpose) from 3M Unitek.
All-Bond 2, a third-generation dentin bonding
agent, contains a 10% phosphoric acid gel for
dentin conditioning. One drop each of Primer A
(NTG-GMA) and Primer B (BPDM) are mixed
and applied to the enamel and dentin until the
acetone solution evaporates

Deciduous teeth and fluorosced or hypocalcified
enamel surfaces produce inconsistent results
when conditioned in the conventional manner.
New hydrophilic universal resins like Assure
Universal bonding resin, Enhance Adhesion
Booster ( Reliance Ortho) , Orthosolo Universal
Bond Enhancer (Ormco, Calif) have been
successful in achieving acceptable bond
strengths with these atypical enamel surfaces.

After etching, multiple coats of the resin is
applied and the last coat is lightly dried.
Attachments can then be bonded with any
chemical or light cured system.


Sumant Goel, Vishwanath Patil (JCO 2005)
assessed Enhance LC, compared it with Light
Bond (3M unitek) in vivo. Total 150 brackets ( 64
Begg, 86 MBT) were bonded.
At 90 days monitoring period out of 150
brackets 13 brackets had bond failure : 2 in
Enhance L.C. group and 11 in Light Bond only
group.
They concluded that application of Enhance LC
appeared to reduce bond failure rate when
compared to Light Bond alone.
Also the adhesion booster did not increase the
amount of adhesive remaining on enamel.

Bonding to amalgam
Sandblasting the surface of restoration followed by use
of adhesives containing 4 META, 10 MDP/Bis GMA and
intermediate resins improves bonding to dental
amalgam.
Amalgambond (Super-Bond D liner) { Chamleon dental
products, Inc, Kansas City, KS} is a 4-META resin that
bonds to amalgam, as do Super-Bond C&B and C&B
Metabond.
Another 10-MDP monomer, besides Panavia EX, is
Clearfil Porcelain Bond (J. Morita USA Inc, CA).

All-Bond 2 and Amalgambond can be
used during initial placement, but
Scotchbond MP should be used only on
hardened, sandblasted amalgam.


Effects of surface treatment on orthodontic bonding to
amalgam.
Skilton JW,
Tyas MJ,
Woods MG.
( Aust Orthod J 2006)
AIM: This study aimed to compare the shear bond
strengths of metal brackets bonded to amalgam
surfaces.
METHODS: One hundred and fifty amalgam samples
were fabricated and either polished, roughened with a
diamond bur or sandblasted with 50 µm aluminium
oxide. Following thermocycling the shear bond strengths
were tested and compared with control samples bonded
to etched enamel.

RESULTS: Concise resin composite, Metal
Primer/Concise resin composite and All-Bond
II/Concise resin composite bonded to
sandblasted amalgam gave the highest mean
shear strengths and were statistically similar to
the etched enamel/Concise resin composite
controls.
CONCLUSION: One would expect sandblasted
amalgam surfaces to be associated with higher
shear bond strengths than diamond bur
roughened or polished amalgam surfaces

Bonding to Gold
Sandblasting, Electrolytic tin plating, or
with gallium tin solution (Adloy),
Superbond C & B, Panavia Ex and
Panavia 21 have been reported to
improve bonding to gold in laboratory
settings.


Bonding to porcelain
Conventional acid etching – ineffective in the
preparation of porcelain surface.
Approaches suggested to improve bond strength
– mechanical, chemical or combination.
Mechanical : Purpose is to remove the glaze
and roughen the surface to provide sufficient
mechanical retention for the adhesive. Can be
achieved by microetching , coarse diamond
stone, sandpaper disks.

Chemical : 1) HF acid – 9.6% HF acid in
gel form applied for 2 min.
2) For areas of ceramic surface where
isolation is difficult, a 1.23% APF gel can
be used for ten min. Bond strength is not
adequate. (Barbosa et al AJODO 1995)
3) Use of Silane coupling agent like
Ormco porcelain primer, Porc Etch,
Reliance Porcelain Conditioner,
Scotchprime (3M).

‫ץ‬methacryloxy-propyltrimethoxy silane is a
coupling agent that provides reactive sites for
inorganic and organic components.
Hydrolysable group ( Silanol group) reacts with
inorganic dental porcelain forming a siloxane (SiO-Si) bond.
The methacrylate group (organofunctional
group) reacts with resin forming covalent bonds
with the polymer matrix of resin composite.

Silane are also known as adhesion promoters & function
by adsorbing and altering the surface of porcelain.
For optimal bonding of orthodontic brackets to porcelain
surfaces, we recommend the following procedure:
1. Deglaze the porcelain surface by sandblasting with
50-micron aluminum oxide for two to four seconds.
2. Etch the porcelain with 9.6% HF acid gel for two
minutes.
3. Apply two or three coats of a silane porcelain primer.
4. Bond the brackets with a highly filled bisGMA resin.

Raed Ajlouni, Samir E. Bishara ( Angle 2005)
evaluated the effect of porcelain surface
conditioning on bonding Orthodontic brackets.
They concluded that most reliable procedure for
orthodontic brackets to porcelain surfaces is
through either microetching + HF acid or with the
use of a silane coupler.


CONCLUSION
The rapid pace of advancements in the field has
altered the commercial life of materials; it is common
for materials, introduced just a few years ago, to
become obsolete, a possible derivative of the lack of
strenuous quality control, and research and design
deficiencies.
Therefore, the clinician faces a handicap
in the race with technology and the requirement to
obtain familiarity with new materials and techniques,
some of which might not have advantages over their
predecessors.

This important implication brings a new
challenge to graduate orthodontic education curricula:
to build a solid background in materials science,
facilitating informed decisions on novel materials and
techniques, as opposed to selecting those based solely
on advertisement brochures.
Thus, evidence-based approaches must extend to
orthodontic materials, with emphasis on the mechanical,
physical, and biological properties, and the potential
alterations induced by intraoral aging and their
implications in mechanotherapy.


Projected short-term future developments
in adhesives ( Eliades T AJODO 2006)
● Glass ionomer and compomer bonding will
become more frequent.
● Two-phase chemically cured systems will be
gradually abandoned.
● Fluoride-releasing adhesives with long-term
release capacity, rather than the current
nonstandardized adhesives, will be introduced.

●Adhesives with antimicrobial properties or
microbial repellent actions might be
adopted.
● Antimicrobial varnishes might be
introduced as the standard means of
prophylaxis.


References
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insensitive primer- An in vitro study. Kerala Dental
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