5. INTRODUCTION
Esthetics has been an important consideration for
the field of Orthodontics.
However, only in recent years, has the esthetics of
the appliance itself been the focus of interest.
Especially with more and more adults seeking
orthodontic treatment, the need for optimum
cosmetic appearance of orthodontic appliances
has been reinforced.
Recurring efforts have been made to make fixed
appliance more aesthetic by eliminating their
metallic appearance.
6. Ceramics are a broad class of materials that
include precious stones, glasses, clays, mixtures of
ceramic compounds, and metallic oxides.
In essence, a ceramic is neither metallic nor
polymeric.
All currently available ceramic brackets are
composed of aluminium oxide.
However, because of their distinct differences
during fabrication, there are two types of ceramic
brackets, namely, polycrystalline alumina and the
monocrystalline alumina.
The manufacturing process plays a very important
role in the clinical performance of the ceramic
brackets.
7. EARLY HISTORY
Ceramics are thought to be the first
materials ever made by man. Early
fabrication of ceramic articles dates back
to 23,000 BC. Historically, three basic
types of ceramic materials were
developed; Earthenware, Stoneware, &
White ware. Ceramics are also considered
to be the earliest group of inorganic
materials to be structurally modified by
man. The first ceramics fabricated by man
were earthenware pots.
HISTORY
8. Chinese Porcelain :- stoneware had been
produced in China by 100 B.C,
and by the 10th century A.D, ceramic
technology in China had advanced to a
highly sophisticated stage.
In 1375, porcelain was copied in Florence,
and rapidly became popular throughout
Europe.
As trade with the far east grew, this
infinitely superior material came from
Europe from China, during the 17th century
9. History of porcelain use in dentistry
The history of porcelain used as a dental
material goes back nearly 200 years.
The use of porcelain in dentistry was first
mentioned by Pierre Fauchard.
The superior surface and coloring qualities
were used by fusing the material to gold or
silver.
This involved the use of low fusing glazes,
which had been known for some hundreds
of years and had reached artistic
eminence in the work of Cellini.
10. CERAMIC BRACKETS
Translucent polycrystalline alumina
(TPA) was developed by NASA (National
Aeronautics and Space Administration)
and Ceradyne, a leader in advanced
ceramics for aerospace, defense,
electronics, and industrial use.
In 1986, a dental equipment and supply
company contacted Ceradyne for an
esthetic material to be used in
orthodontics.
Ceradyne recommended TPA. Shortly,
after this contact, namely in 1987,
ceramic brackets were introduced.
11. CERAMIC BRACKETS-TYPES
Ceramic brackets are composed of
aluminum oxide .
Polycrystalline alumina &
monocrystalline alumina are the two
most common varieties.
Another category that is being
developed is the Zirconium brackets
13. POLYCRYSTALLINE BRACKETS –
MANUFACTURING PROCESS
Nowadays, the majority of
polycrystalline (multiple crystals)
brackets are produced by ceramic
injection molding (CIM).
An outline of CIM is as follows:
the aluminum oxide (Al2O3) particles are mixed
with a binder.
This mixture is rendered flowable through heat
and pressure application and injected into a
bracket mold.
The binder is removed, i.e., burned out.
Subsequently, sintering—the production of a
coherent mass by heating without melting—is
14. The advantage of CIM is that this
technology can manufacture complex
and precise items with smooth
surfaces in large quantities at fast
rates.
15. MONOCRYSTALLINE BRACKETS –
MANUFACTURING PROCESS
. The production process for monocrystalline
(single crystal) ceramic brackets, also
referred to as sapphire brackets, is
completely different.
Here, the Al2O3 particles are melted.
The resultant mass is slowly cooled to permit
a controlled crystallization, leading to the
production of a large, single crystal.
16. This large, single crystal in rod or bar
form is then milled into brackets with
ultrasonic cutting techniques and/or
diamond cutting tools.
After milling, the monocrystalline
brackets are heat-treated to eliminate
surface imperfections and to relieve the
stress caused by the milling procedure.
The production of these brackets is more
expensive when compared to the
production of polycrystalline brackets.
This increased expense is mainly due to
the difficulty of milling, i.e., the cutting
process.
17. Comparison of properties-2
Types
Production of polycrystalline brackets is
less complicated, these brackets are
more readily available at present.
Single crystal brackets are noticeably
clearer than polycrystalline brackets,
which tend to be translucent.
Both resist staining and discoloration.
Come in a variety of edgewise structures
including true Siamese, semi-Siamese,
solid, and Lewis/Lang designs.
18. Zirconia brackets
Zirconia is a mineral extracted from beach
sands of Australia.
The PSZ (Partially stabilized Zirconium)
developed by the Commonwealth
Scientific and Industrial Research
Organization (CSIRO) as a reliable highly
stress-resistant material.
A remarkable quality of zirconia -based
advanced ceramics is that wear actually
makes the material stronger .
19. Zirconia brackets
Theoretically , the low frictional coefficients
achievable with yttria-stabilized zirconia should
make it a suitable alternative to alumina for
bracket construction.
However, zirconia brackets have problems
related to color and opacity, which detract from
the esthetics, and can inhibit composite
photopolymerization.
A study by Kusy et. al. concluded that zirconia
brackets offer no significant improvement over
alumina brackets with regard to their frictional
characteristics.( Kusy, AJO 1994)
21. Ceramic brackets- hardness
Ceramic brackets are known for their
hardness.
They are notably harder than enamel.
Thus, contact between enamel and
ceramic brackets has to be avoided by all
means.
22. This type of contact can lead to severe
enamel damage.
Particular care has to be exercised
with deep bite and/or class II canine
relationship patients.
If required, bite opening applications
must be performed to prevent enamel
damage.
23. Ceramic brackets- tensile strength
The ultimate tensile strength, often
shortened as tensile strength, is defined as
the maximum stress that a material can
withstand while being stretched or pulled
before failing or breaking.
When stress is placed on a ceramic
material, its unyielding atomic structure
makes the redistribution and the relief of
stress close to impossible.
Ductile materials, such as metals and
polymers, experience plastic deformation
before failure.
24. Ceramic brackets- tensile strength
In other words, the elongation of
ceramics at failure (brittle fracture) is
less than 1%, yet the elongation of
stainless steel at failure (ductile
fracture) is approximately 20%.
Hence, ceramic brackets do not flex.
This implies that ceramic brackets are
much more likely to fracture than metal
brackets under identical conditions.
25. Ceramic brackets- fracture toughness
Fracture toughness is a property which describes
the ability of a material containing a crack to resist
fracture.
This is an important material property since the
presence of imperfections, such as microscopic
scratches, cracks, voids, and pores are not
completely avoidable during the fabrication of
materials.
These microscopic imperfections may or may not
be harmful to the material, depending on a number
of factors such as the fracture toughness of the
material examined, the stress on the material,
26. The higher the fracture toughness, the more
difficult it is to propagate a crack in that
material.
The fracture toughness of polycrystalline
alumina brackets is higher than the fracture
toughness of monocrystalline alumina
brackets.
This implies that crack propagation is
relatively easier in single-crystal alumina
brackets when compared with polycrystalline
alumina brackets.
Polycrystalline brackets have a higher
resistance to crack propagation due to crack
interaction with grain boundaries (GBs).
A GB is the interface between two “grains”
(crystals) in a polycrystalline (multiple
crystals) material.
Cracks are impeded at these GBs.
28. Clinical applications that may scratch
the surfaces of ceramic brackets may
greatly reduce the fracture toughness,
thereby predisposing ceramic brackets
to eventual fracture.
Thus, utmost care has to be taken not
to scratch ceramic bracket surfaces
with instruments and stainless steel
ligature wires during treatment.
Also, the clinician should not
overstress when ligating with steel
ligature wires.
29. Careful ligation is mandatory, and
elastomeric modules (ligatures) or
coated ligatures are advised to
prevent ceramic bracket fractures,
particularly tie-wing fractures.
Arch wire sequencing also has to be
performed carefully.
The use of resilient full-size arch wires
before the placement of full-size
stainless steel arch wires is
recommended.
30. Tie-wing fracture
Distogingival tie-wing fracture (the red
elastic ligature was used to accentuate
this fracture).
Most likely this tie-wing was damaged
with pliers during arch wire insertion into
the molar tube.
31. The semitwin tie-
wing complex.
The tie-wing complex of polycrystalline ceramic
brackets can be manufactured as either semitwin
or true twin.
Semitwin differs from true twin by having an
isthmus of ceramic joining the mesial and distal
tie-wings, i.e., the mesial and distal tie-wings are
not four independent projections from the bracket
base as with the true twin configuration.
This semitwin configuration has been stated to
possess a better tie-wing fracture strength.
It has been proposed that such a ceramic
connector produces a cross-stabilizing effect .
32. Bond strength
Chemical bonding : glass is added to the
aluminum oxide base and is treated with a
silane coupling agent. Silane bonds with glass
and leaves a free end of its molecules that react
with any of the acrylic bonding materials.
Shiny surfaces of ceramic brackets bonded
chemically allow greater distribution of stress
over the whole adhesive interface without the
presence of any localized stress areas.
Significantly greater shear bond is needed to
cause debonding and pure adhesive failure
33. Bond strength
Mechanical bonding : brackets have
retentive grooves in which edge angles are
90°. There are also crosscuts to prevent the
brackets from sliding along the undercut
grooves that have sharp edge angles, thus
leading to high localized stress
concentrations around the sharp edges
and resulting in brittle failure of the
adhesive. On application of shear
debonding force, part of the adhesive is left
on the tooth and part on the grooved
bracket.
34. Mean shear bond strength of the polycrystalline
ceramic brackets is significantly greater than
that obtained when stainless steel brackets are
used.
Single crystal ceramic brackets produce the
lowest mean shear bond strength values.
Gwinnett( AJO1988) reported that the mean
values for the different bracket types are not
statistically significant, but this conflicts with the
results of many other studies.
35. Bond strengths are greater with chemical
bonding than with mechanical retention which
shows bond strengths comparable to metal
brackets (Wang AJO1997).
Decreasing etching time, (with 37% phosphoric
acid) from 30 seconds to 10 seconds maintains a
clinically useful-bond strength. (Olsen & Bishara
AJO 1996).
Light-cured GICs provide sufficient strength for
bonding ceramic brackets, but in terms of bond
failure site and bracket fracture, they provide no
advantage over composite adhesives. (Jost-
Brinkmann, J Adhesiv Dent 1999)
38. Bond strength of ceramic brackets
Weinberger, Angle 1997, evaluated 3
different methods of curing for poly- and
mono-crystalline brackets.
The mean shear bond strengths of the
single crystal alumina brackets with
silanated bases were significantly higher
than those of the poly-crystal alumina
brackets with non-silanated bases, and no
enamel fractures were found on debonding
the chemically cured brackets while the
light and argon laser groups exhibited a
10% rate of enamel fracture on debonding.
39. ( Sadowsky, AJO 2004).
Mean bond strengths of Clarity brackets
(polycrystalline) and Inspire brackets
( monocrystalline) found to be
comparable.
No enamel damage was evident in any
specimen when the brackets were
removed with the appropriate pliers
recommended by the manufacturers.
40. Frictional Resistance
When polycrystalline ceramics were compared
with monocrystalline ceramics, it was concluded
that polycrystalline ceramics have a higher
coefficient of friction.
In fact, more than a decade ago, it was pointed
out that monocrystalline brackets have frictional
characteristics close to metal brackets .
To overcome the problem of frictional resistance of
polycrystalline brackets, manufacturers carried out
numerous modifications.
41. Polycrystalline ceramic brackets with metal
inserts in the arch wire slot (metal slots) were
developed.
Nevertheless, it was reported that the sharp
edges of the metal insert may “dig into” the
softer arch wire material, thus increasing
resistance to sliding and thereby reducing the
efficiency of tooth movement.
Another modification was the addition of
bumps along the floor of the polycrystalline
ceramic bracket slot.
Nevertheless, these bumps were not effective
in reducing frictional resistance.
42. A recent study, including ceramic and
metal brackets that were manufactured
by different production methods,
including CIM and metal injection
molding (MIM), concluded that the
manufacturing technologies do not
present a critical difference regarding
friction.
It was reiterated that the complex
phenomenon of friction depends on a
multitude of factors, such as the
bracket/ligature/arch wire combinations,
the surface quality of the arch
wire/bracket slot, the bracket design, and
the force exerted by the ligature on the
43. Frictional Resistance
Mono-crystalline alumina brackets are smoother
than polycrystalline samples, but their frictional
characteristics are comparable.( Kusy
AJO1994)
To reduce frictional resistance, development of
ceramic brackets with smoother slot surfaces,
rounding of slot base or consisting of metallic
slot surfaces has been accomplished.
Metal-lined ceramic brackets can function
comparably to conventional stainless steel
brackets and 18-kt gold inserts appear superior
to stainless steel inserts. (Kusy & Whitley,
44. Frictional Resistance
Ligation: Usefulness of
Teflon-coated ligatures
compared to elastomeric
ligatures in minimizing
the high friction of
ceramic brackets when
an esthetic appliance is
imperative (DeFranco,
Angle 1995).
Manufacturers have also
introduced self ligating
ceramic brackets.
47. Optics
• The optical properties of ceramic brackets
provide an attractive option for a great
number of patients.
• As previously mentioned, polycrystalline
ceramic brackets possess a microstructure of
crystal GBs.
• This microstructure reflects light, resulting in
some degree of opacity.
• In contrast, single-crystal brackets lack GBs,
thus permitting the passage of light, making
these brackets basically clear.
48. • monocrystalline brackets have more
optical clarity than polycrystalline
brackets
Intraoral image of monocrystalline (A)
and polycrystalline (B) ceramic brackets
49. COLOR STABILITY
• The color stability of ceramic brackets throughout
orthodontic treatment is an important
characteristic.
• It has been stated that ceramic brackets, both
monocrystalline and polycrystalline, undergo a
color change when subjected to coffee, black tea,
coke, and red wine
.
• It has to be pointed out that these are in vitro
findings.
• In vivo studies concerning the color stability of
ceramic brackets are lacking.
50. Plaque accumulation
Limited information is available about
which bracket material (ceramic
versus metal brackets) is less prone to
the adhesion of bacteria and plaque
accumulation.
51. A clinical study performed by Lindel et
al. concluded that ceramic brackets
exhibit less long-term biofilm
accumulation than metal brackets.
Also pointed out that the results
obtained from this type of future
research might have a strong effect
when choosing bracket material in
patients with insufficient oral hygiene
habits.
52. Biocompatibility
Biocompatibility is the ability of a
material to provide successful service
in a host while causing minimal
response.
It has been stated that conventional
ceramic brackets are chemically
stable (inert) in the oral environment
and that they exhibit excellent
biocompatibility with oral tissues.
53. In 2012, Retamoso et al. carried out
an in vitro cytotoxicity study evaluating
various orthodontic brackets.
These researchers reported that
monocrystalline ceramic brackets had
good biocompatibility.
On the other hand, polycrystalline
ceramic brackets with metal slots
demonstrated some toxic effects.
54. MAGNETIC RESONANCE IMAGING
(MRI) COMPATIBILITY
Orthodontists are often asked to
remove fixed orthodontic appliances
prior to an MRI scan—a diagnostic
tool that does not expose the patient
to radiation—particularly when looking
for pathology in the head and neck
region or when information regarding
the articular disc is required.
55. Beau et al. provided a detailed flowchart
concerning the indications for the removal of
fixed orthodontic appliances prior to MRI
scans of the head and neck region.
According to this flowchart, ceramic brackets
do not have to be removed prior to an MRI
scan.
They are MRI-safe.
However, ceramic brackets with any metal
components, such as stainless steel slots,
have to be removed if the region under
examination is adjacent to these brackets.
56. Base surface characteristics
Formed with undercuts or grooves that provide a
mechanical interlock to the adhesive. These
brackets may have a flat base, covered with a
silane layer with recesses for mechanical
anchoring.
Bracket base has a smooth surface and relies on
a chemical coating to enhance bond strength. A
silane coupling agent is used as a chemical
mediator between the adhesive resin and the
bracket base because of the inert composition of
the aluminium oxide ceramic brackets. The
manufacturers of such brackets have reported
that they achieve higher bond strength when
57. Base surface characteristics
Polycrystalline alumina with a rough base comprised of
either randomly oriented sharp crystals or spherical glass
particles to provide micromechanical interlocking with
the orthodontic adhesive.
To overcome the potential damage of enamel during
debonding, a ceramic bracket with a thin polycarbonate
laminate on the base has been manufactured
(CeramaFlex, TP Orthodontics). The bond to the
enamel is by the thin polycarbonate laminate. It is
suggested that these brackets are as easy to remove as
metallic brackets.
Ceramaflex brackets have a significantly lower bond
strength than traditional ceramic brackets. On the other
hand, the bond failure location of the Ceramaflex bracket
is consistently more favorable, i.e., occurring at the
ceramic bracket-polycarbonate base.( Olsen & Bishara
59. photomicrograph of a Lumina bracket base.
uniformly distributed and embedded spherical particles
60. SEM photomicrographs of a Transcend 2000 bracket base
randomly oriented crystals of various shapes that form an irregular
substrate capable of micromechanical anchoring
61. Bracket Placement
Certain ceramic brackets have color coded
long axis indicators which enable easy
identification and eliminate bonding errors.
The long axis indicator is removed with a
pull motion after the bonding procedure.
62. Removable
color coded
indicators
provide positive
bracket
identification
and allow easier
placement.
Millimeter marks
aid in obtaining
proper occlusal-
gingival height
and eliminate
the need for
special
3mm
4mm
5mm
63. Debonding of ceramic brackets
Debonding usually refers to the removal of
orthodontic brackets and the residual adhesives from
the tooth enamel at the end of fixed appliance
treatment.
Ceramic brackets lack flexibility. In other words, the
rigid ceramic and the rigid enamel have little ability to
dissipate stress when exposed to debracketing forces
at the end of treatment.
Thus, bracket fracture and/or enamel damage may
occur during debracketing .
Several approaches aiming to minimize the side
effects associated with the debracketing of ceramic
brackets exist.
These are the conventional (mechanical), ultrasonic,
64. Mechanical Debonding techniques
1.Lift-off debracketing method:
The first technique uses a lift-off debracketing
instrument (LODI).
This pistol-grip plier is placed over the bracket,
and a debracketing force is applied to the tie-
wings of the bracket.
It has been pointed out that the LODI cannot be
used with ceramic brackets due to their
brittleness.
65. Mechanical Debonding techniques
Delaminating method:
The delamination technique was the first
technique introduced and is still reported to be
the most widely accepted ceramic bracket
removal technique.
This technique involves the application of a slow
squeezing force with the sharp blades of the
debracketing pliers placed on the enamel surface
and within the adhesive, thereby producing a
wedging effect.
Sinha & Nanda (AJO1997) found this technique
to be safe for debonding mono- and poly-
crystalline ceramic brackets.
67. Wrenching method: The wrenching
technique uses a special tool that
produces a wrenching or torsional
force at the base of the bracket.
This approach, providing a rotational
shear force, can be likened to the
turning of a door knob.
68. ENAMEL FRACTURE & MECHANICAL DEBONDING
The degree of force required to achieve
mechanical bond failure and the sudden nature of
bracket failure could cause enamel fracture or
cracks and raise the risk of aspiration of bracket
fragments by the patient.
This debonding method imposes the risk of
bracket fracture. In case of bracket fracture, the
removal of the remaining fragments of the ceramic
brackets from the enamel surface has to be
carried out with a diamond bur in a high-speed
69. This procedure is time-consuming, produces
large fragments of the bracket during
grinding, and results in large amounts of
ceramic dust that has been associated with
itchy skin on hands and eye irritation.
Grinding ceramic material from the tooth
surface may generate heat, which could
damage the dental pulp, if low-speed
grinding without coolant is used.
72. Enamel fracture & debonding
Debonding with sharp-edged pliers that apply a
bilateral force at the bracket base-adhesive
interface was found to be the most effective
method for debonding polycrystalline alumina
orthodontic brackets.
Forces applied at the interface rather than the
bracket itself may prevent breakages on
debonding.
Further, it was reported that brackets bonded by
indirect techniques that create a resin interlayer
facilitates debonding at the interface formed
between this interlayer and the filled resin.( Sinha,
Nanda AJO1995 )
73. ADJUNCTIVE METHODS PROPOSED FOR
MECHANICAL DEBRACKETING
Larmour and Chadwick evaluated the ability
of a commercial debonding agent,
postdebonding agent (P-de-A) (Oradent
Ltd., Eton, Berks, UK).
This green gel, containing a derivative of
peppermint oil, was claimed to facilitate
ceramic bracket debracketing and
adhesive residue removal.
The manufacturer of P-de-A advised an
application time of 1–2 min to soften the
resin. Nevertheless, the P-de-A research
results did not support these claims.
74. In 1997, Arici et al. proposed the use of a crushable
porous ceramic lamella as a means of facilitating
debracketing.
These porous lamellae were attached to the
bracket base with adhesive resin.
Subsequently, these bracket/lamella assemblies
were bonded to the enamel of the experimental
teeth (bovine incisor teeth).
The authors of this in vitro study reported the safe
removal of these ceramic bracket/lamella
assemblies, i.e., no fractures of the ceramic
bracket or any evidence of enamel damage was
observed.
75. In 1998, Larmour et al. evaluated the
possibility of reducing the complications of
ceramic bracket debracketing by
introducing a notch in the composite bond
layer.
A section of Mylar® matrix strip (0.01 mm
thick and 0.75 mm wide) was placed within
the bonding agent in this ex vivo
investigation.
After the bonding agent had set, the matrix
strip was removed creating a “notched”
bond layer.
Larmour et al. concluded that notching the
76. In 2003, Carter suggested that a hot-water bath
might facilitate ceramic bracket debracketing.
Patients were given a cup of hot water, supplied
from a coffeemaker, and were asked to hold this
water in their mouths for 1 min without swallowing.
Subsequently, debracketing with suitable pliers was
performed.
Carter emphasized that since 1986 no enamel
fracture or any other iatrogenic damage occurred
with this application in his clinic.
Unfortunately, the exact temperature of this “hot-
water bath” was not stated.
77. Electrothermal debonding
It involves heating the bracket with a
rechargeable heating gun while applying a
tensile force to the bracket. The bracket
separates from the tooth once sufficient heat
has penetrated the bracket/adhesive
interface.
The potential for pulp damage exists,
because a significant rise in pulp temperature
may result in tooth necrosis.
78. Electrothermal debonding
The safety threshold of a 5.5° C increase
in intra-pulpal temperature described by
Zach and Cohen should not be violated.
Other disadvantages include the bulky
nature of the handpiece that may make its
intraoral use difficult, especially in the
premolar region, and the risk of dropping a
hot bracket in the patient's mouth.
Bishara and Trulove(AJO 1990) found the
electrothermal technique to be quick,
effective, and devoid of either bracket or
enamel fracture.
80. ULTRASONIC
DEBRACKETING
It was reported that the ultrasonic debracketing
technique presents a decreased probability of
enamel damage as well as a decreased probability
of bracket fracture.
Also, the residual adhesive remaining after
debracketing can be removed with the same
ultrasonic tip.
Nevertheless, the debracketing time is the longest
when compared with the mechanical or
electrothermal debracketing techniques.
It was reported that the debracketing time of the
ultrasonic debonding technique is 38–50 s per
bracket, when compared with 1 s per bracket with
the mechanical debracketing technique.
81. Furthermore, the contact between the
“hard” ceramic bracket and the
ultrasonic tip has been reported to
cause wear of this expensive tip.
During the ultrasonic debracketing
procedure, water spray is mandatory
to prevent pulp damage.
This method requires further testing
and is not yet recommended for
clinical use.
82. LASER DEBONDING
Lasers : Debonded by
irradiating the labial
surfaces of the brackets
with laser light.
Reduces the residual
debonding force, the
risk of enamel damage,
and the incidence of
failure.
less traumatic and
painful for the patient
and less risky for
enamel damage.
83. Laser debonding - Mechanism
Types of lasers : Nd YAG,, super-pulse carbon
dioxide lasers ,carbon di-oxide lasers
Laser-initiated degradation can occur by:
Thermal softening: which occurs at relatively low
rates of laser energy deposition, heats the
bonding agent up until it softens,
Thermal ablation occurs when the rate of energy
deposition is fast enough to raise the temperature
of the resin through its fusion range and into its
vaporization range before debonding by thermal
softening occurs. The rapid buildup of gas
pressure along the bonding interface will
explosively "blow" the bracket off the tooth,
independent of any externally applied debonding
84. Laser debonding - Mechanism
Photoablation occurs when very high
energy laser light interacts with a material.
During the process, the energy level of
the bonds between the bonding resin
atoms rapidly rises above their bond
disassociation energy levels, and the
material decomposes. High gas pressure
would rapidly develop within the interface,
and the bracket would be explosively
blown off the tooth after a single light
pulse.
85. Enamel abrasion and wear
Can occur during contacts
of ceramic brackets with
occluding teeth.
The highest abrasion
scores have been reported
with mono-crystalline
ceramic brackets.
Contact of the opposing
teeth with the ceramic
brackets must be avoided .
86. Bracket Fracture
The breakage of ceramic brackets is a problem
related to the low fracture toughness of the
aluminium oxide, and the ability to resist it depends
on the type and shape and the bulk of the material
present.
Bracket breakage might occur either in function or
in the debonding process. The internal defects and
machining interference are primary causes of
fracture.
Bracket-wing fracture is a frequent problem.
Increased chair time and potential health risk due
to the possibility of swallowing or aspirating a
bracket fragment, which would be difficult to locate
because of the radiolucent nature of alumina.
87. Bracket Fracture
Third-order wire activations are more likely to cause
ceramic bracket failure, but the fracture resistance
of the ceramic brackets during arch wire torsion
appears to be adequate for clinical use. (Aknin,
Nanda AJO 1996)
Careful ligation is necessary and elastomeric rings,
if feasible, or coated ligatures are recommended to
prevent tie-wing fracture.
88. Bracket Fracture
Second-order wire activations do not cause ceramic
bracket failure, unless the bracket has been
previously weakened by a direct trauma or by
surface defects during treatment.( Lindauer et al
AJO1994).
Extra care should be undertaken during treatment
to avoid scratching of the bracket surfaces with the
89. REBONDING/ RECYCLING
CERAMIC BRACKETS
Gaffey et al (Angle 1995) evaluated
different methods of recycling:
silane coupling agent, heat plus silane
coupling agent, hydrofluoric acid plus
silane coupling agent, and heat plus
hydrofluoric acid plus silane coupling agent.
Treatment of electrothermally debonded
ceramic brackets with silane or heat plus
silane resulted in bond strength greater
than 9 MPa, which was clinically
acceptable. The use of hydrofluoric acid
significantly reduced the bond strength
90. Heat: Lew and Djeng.(JCO 1990) - Brackets
heated until cherry red to burn off residual
composite resin. Bracket base then rinsed
with 100% alcohol and left to dry.
Lew et al( EJO 1991) found that the bond
strength of these recycled brackets was
about 30% less than new chemically
retentive ceramic brackets, yet it might
maintain an acceptable bond strength and
lead to fewer enamel fractures on
debonding.
91. An in vitro study, carried out in 2016, investigated
the “recycling” of polycrystalline ceramic brackets
with a microcrystalline base via the following three
methods:
first is the erbium-doped yttrium aluminum garnet
(Er:YAG) laser, and
the other two are traditional methods,
i.e., flaming and sandblasting.
Sandblasting (50 μm Al2O3 particles) damaged the
delicate bracket base structure and demonstrated
significantly less bond strength than new brackets.
The flaming procedure yielded a bond strength that
was similar to that of new ceramic brackets.
92. However, flaming affected the esthetics of
these brackets, i.e., these brackets ended
up faded and dark.
Er:YAG lasers completely removed the
adhesive remnants from the ceramic
bracket bases without damaging the base
structure.
Furthermore, the shear bond strength of
Er:YAG laser “recycled” brackets was
similar to that of new brackets.
It was pointed out that the laser method
may be preferred over other “recycling”
methods.
Yassaei et al. also concluded that the
94. 1.Enamel fracture and flaking or fracture
lines in enamel during debonding.
Is related to the high bond strength of ceramic brackets.
Solution A: Avoid sudden impact loading or stress
concentration within the enamel by using proper
debonding techniques.
The best available guidelines are those suggested by the
manufacturer.
Solution B: Do not bond ceramic brackets on structurally
damaged teeth.
Crack lines, heavy caries, large restorations, hypoplasia
and hypocalcification should be contraindications to
bonding with ceramic brackets.
Crowns – whether they are made of resin or porcelain –
may break when ceramic brackets are debonded. Patients
must be informed of this possible.
95. Solution C: Reduce bond strength:
Add mechanical retention
Increased mechanical retention might reduce the side
effects of debonding by favoring failure within the adhesive
itself.
Reduce chemical adhesion
Add a metal mesh at the base of the bracket
A metal mesh at the base of the bracket would reduce
bond strength to the levels observed with metal brackets.
Adding the mesh, however, would mean an increase in
production cost that is probably not acceptable at this time.
It may also present an esthetic disadvantage.
Reduce the base area of the bracket
Reducing the bracket base area may decrease the bond
strength but it does not eliminate high stress at the bond
site.
96. Joseph and Rossouw (AJO 1990)
reported a higher incidence of failure at the
resin/bracket interface when original
Transcend brackets (chemical retention)
were bonded with light-activated, microfilled,
more brittle composite resin and increased
failure within the enamel when the bracket
was bonded with a chemically-cured,
macrofilled, more elastic resin.
Modify the etching time and/or
concentration of etching acid (H3PO4)
97. Use weaker resins: Iwamoto(1987)
suggested that the composition of the resin
influences the (tensile) strength of the bond.
He reported that low-filled and highly-filled
Bis-GMA resins used for bonding silane
coated ceramic brackets led to higher
percentages of bracket failure at the
base/resin interface (80% and 90%
respectively) or within the adhesive (20%
and 10% respectively), than a 4
META/MMA-TBB unfilled resin.
Solution D: Debond with ultrasonic,
98. 2.Removal of ceramic brackets by
grinding
When a proper debonding technique fails, and/or
risks subjecting the tooth to increased forces and
fracture, grinding the ceramic bracket becomes the
option of choice.
Grinding is usually conducted with high-speed
diamond burs or low-speed green stones.
The procedure is time-consuming and the heat
which can be generated by grinding may affect the
dental pulp and, subsequently, the vitality of the
tooth.
99. Solution: Reduce the size of ceramic to be
ground by fracturing the tie wings with
ligature cutting pliers, and avoid the build
up of heat during grinding.
Air or water coolant must be used while
grinding the bracket to avoid a rise in pulp
chamber temperature.
100. 3.Attrition of teeth occluding against
ceramic brackets.
Solution: Select the teeth to be bonded
with ceramic brackets.
The clinician must avoid bracket contact
with opposing teeth. In a case with a deep
anterior overbite, avoid bonding the
mandibular teeth with ceramic brackets; in
a case where the maxillary canine is
retracted past the mandibular tooth, avoid
bonding the mandibular canine.
101. 4.INCREASED FRICTION WITH CERAMIC
BRACKETS
Solution A: Develop brackets with smoother
slot surfaces
Brackets with smoother slot surfaces,
incorporated metal slots or brackets
composed of ceramic and plastic may allow
the archwire to slide smoothly.
Solution B: Avoid loss of anchorage and
increase in overbite.
Strengthen the anchorage requirements and
carefully select the teeth to be bonded.
Solution C : Avoid sliding mechanics
102. 5.Breakage of ceramic brackets
Problem is due to the low fracture toughness of the
aluminum oxide, affects bracket wings and occurs
accidentally when cutting ligature wires or
engaging a heavy archwire in the bracket. The
slightest torque of such wire in the bracket interfac
leads to fracture.
Solution: Avoid direct contact of the brackets whe
cutting ligature wires and forceful engagement of
increasingly heavy archwires used for leveling.
Successive archwires should be fully engaged in
the brackets. Also, it may be safer to avoid using
ceramic brackets in people prone to trauma
because of professional or numerous sports
activities, such as football, martial arts or other
103. 6.Increased pain or discomfort while
debonding ceramic brackets
This is related to the higher bond strength.
Solution: Have patient bite with pressure on
cotton roll and/or gauze during debonding.
Reactions vary from patient to patient and in
an individual, may even vary from tooth to
tooth and with the timing of debonding.
Pain may increase if the teeth being
debonded have just undergone active
movement or traumatic pressure from
occlusion, elastics or other orthodontic
forces
104. 7.Limited rotation of teeth with ceramic
brackets
Mainly affects brackets designed for mandibular
incisors because they are necessarily the
smallest. Incorporating four wings tends to
weaken the brackets. Ceramic brackets also tend
to be bulkier than metal brackets as this is
required for sufficient resistance to fracture.
Solution: Further research and development
Some companies already manufacture smaller
brackets with four wings but additional research
is needed to develop less bulky ceramic or
ceramic-like materials which can provide the
properties of metal brackets with the esthetic
advantages of ceramics.
105. 8.Esthetic results are not absolute.
Ceramic brackets hold a definite advantage over plastic
attachments, but some polycrystalline brackets do stain.
This is due to individual diets – prolonged use of
caffeine (coffee, tea, colas) for example, – or hygiene
practices (certain mouthwashes), or lipstick, but may
also be associated with the type of bonding resins used.
Solution: Avoid excessive use of staining substances
and, perhaps, select least-discoloring resins.
Ceramic brackets may look discolored when the
brackets themselves stain (direct discoloration) or when
stains on the teeth or bonding resin show through the
bracket (indirect discoloration). It tends to occur with
polycrystalline brackets. Using two-base resins, which
tend to discolor less than no-mix one-step bonding
resins, has been advocated.
106. 9.Operational risks
The primary operational risk for the patient is the accidental
ingestion or aspiration of a bracket during bonding or
debonding, or of bracket particles if the bracket fractures
during debonding.
Ceramic brackets may not be detected on radiographs if
aspired. During debonding, fractured fragments may
subject the patient to oral soft tissue damage, and the
patient, clinician and assistant to eye injury.
Solution: Use caution and protective equipment during
bonding and debonding.
Instructing the patient to bite on a cotton roll during
debonding helps reduce the risk of dislodging brackets
and/or fragments into the oral cavity and throat. The
clinician and assistant should wear protective glasses and
a mask. The patient should wear protective glasses as well,
108. Esthetics has become today an
important and integral part of the
orthodontic treatment.
With the invention of revolutionary
aesthetic brackets, the need for
aesthetic wires became very strong.
109. Esthetic archwires available are
composite, optiflex and coated
archwires.
In orthodontics, composite prototypes
of archwires, ligatures and brackets
have been made from S-2 glass fibers
(a ceramic) and acrylic resins
(Polymer).
110. Malik, dubey et al;review of
orthodontic archwires;JOFR
2015
Optiflex
◦ Optiflex is a most aesthetic orthodontic
arch wire designed by Dr. Talass and
manufactured by ORMCO.
◦ It has highly aesthetic appearance as it is
made of clear optical fiber, which
comprises of 3 layers.
◦ Inner core is silicon dioxide core, middle
layer is made with silicon resin and the
outer layer is nylon layer.
111. Core provides the force for moving
tooth, middle layer protects the core
from moisture and also provides
strength and the outer layer prevents
damage to the wire and also further
increases the strength.
Optiflex is very flexible and is effective
in moving teeth using light continuous
force.
112. Teflon coated stainless steel
arch wires
Teflon is coated on stainless steel wire by an
atomic process that forms a layer of about 20-25ìm
thickness on the wire that imparts to the wire a hue
which is similar to that of natural teeth.
Teflon coating protects the underlying wire from
the corrosion process.
However, corrosion of the underlying wire is likely
to take place if it is used for longer period in the
oral cavity since this coating is subject to flaws that
may occur during clinical use.
113. Titanium-Niobium Archwire
Recently a new ‘finishing wire’ made from a nickel
free titanium-niobium alloy was introduced.
According to manufacturers, product information
TiNb is soft and easy to form, same working range
as SS, and stiffness is 20% lower than TMA and
70% lower than SS.
The mechanical properties of these newly
introduced titanium-niobium finishing wires were
investigated both in bending and torsional loading
mode, the stiffness, yield point, post-yield behavior,
and spring back of titanium-niobium wires were
experimentally determined and compared to those
of equally sized SS wires.
114. Timolium
Timolium (titanium vanadium) is an advanced
techno-logy titanium wire with a smooth surface
that greatly reduces friction.
The surface of Timolium is much smoother than
traditional TMA (beta titanium) wire.
Higher resistance to breakage with its smooth
surface,
Its high yield strength withstands bending without
breaking. Intricate loops and bends can be made
easily to accommodate a variety of treatment
options.
Orthodontists using Timolium agree that it is ideal
for torquing and tipping ceramic brackets, with
higher yield and compressive strength than TMA
115. Bioforce wires
BioForce is aesthetic and is part of the first
and only family of biologically correct
archwires.
“Bioforce archwires’ were introduced by
GAC.
The Ni-Ti Bioforce wires apply low, gentle
forces to the anterior teeth and increasingly
stronger forces across the posterior teeth
until plateauing at the molars.
The level of force applied is graded
throughout the arch length according to
tooth size.
117. With the increase in adult orthodontic
treatment comes the need to find a
reliable method for bonding
orthodontic brackets onto metal or
ceramic crowns and fixed partial
dentures.
Conventional acid etching is
ineffective in the preparation of
porcelain surfaces for mechanical
retention of brackets.
118. In 1968, Wood et. al. showed that
roughening the porcelain surface,
adding a porcelain primer, and using a
highly filled adhesive resin when
bonding to glazed porcelain added
progressively to bond strength..
119. There are two variable options
when bonding to porcelain
1. Bond it mechanically by etching the
porcelain with hydrofluoric acid or
2. Bond it chemically using a silane
coupling
agent.
120. The disadvantages of a hydrofluoric acid etch are
that
1. It involves using a potentially dangerous acid.
2. It creates a porous, roughened surface in the
porcelain, much like etched enamel (removes outer
glaze).
Silane coupling agents are provided in the form of
porcelain primers. It chemically unites the silicon in
porcelain to the acrylic bonding material used. They
are hybrid inorganic-organic bifunctional molecules
that create a siloxane network with the hydroxyl(OH)
groups on the HF-etched hydrophilic glass ceramic
surface and copolymerize with the hydrophilic resin
matrix of the composite.
121. For optimal bonding of orthodontic brackets and
retainer wires to porcelain surfaces, the following
technique is recommended:
1. Isolate the working field adequately, band the
actual crown separately from the other teeth.
2. Use a barrier gel such as Kool-Dam on Mandibular
teeth to prevent HF gel contact with gingival or soft
tissues.
3. Deglaze an area slightly larger than the bracket
base by sandblasting with 50 μm aluminium oxide
for 3 seconds.
122. 4. Etch the porcelain with 9.6% hydrofluoric
acid gel for 2 minutes.
5. Carefully remove the gel with cotton roll
and then rinse using high-volume suction.
6. Immediately dry with air, and bond bracket.
The use of a silane is optional.
HF will not be effective for bonding to
highalumina porcelains and glass ceramics,
and new technique improvements eg. silica
coating are needed for successful bonding.
123. Procedure
1. Thorough prophylaxis of the tooth to be bonded
should be done. Then rinse and dry the tooth
adequately.
2. Micro-etch the crown and then rinse and dry.
3. Place Barrier gel on gingival margin.
4. Place porcelain etchant on the crown. Leave for 4
minutes. Then rinse and dry.
5. Apply one thin layer of porcelain conditioner.
Leave for one minute.
6. Apply one coat of Universal bonding Resin and air
dry.
7. Proceed with the application of paste and bond the
bracket.
124. Some authors have claimed that the
compositeporcelain
bond is mostly micromechanical and that the
contribution of the silane application for a chemical
bond to most feldspathic porcelains is negligible.
The most commonly used porcelain etchant is
9.6% hydrofluoric acid in gel form applied for 2
minutes.
125. Debonding Considerations
A gentle technique is necessary to
achieve failure at bracket-adhesive
interface and avoid porcelain fracture.
The best method is to use a peel-type
force, which is applied by distorting
the bracket.
126. With a twin-type bracket, gently squeeze the
bracket wings together with a plier.
This will separate the bracket from the adhesive
underneath, leaving an adhesive layer on the
porcelain crown, which is then removed with a
tungsten carbide finishing bur, sanding discs.
Smoothing is achieved with slow-speed polishing
rubber wheels and enamel-like gloss by using
diamond polishing paste in rubber cups.
127. Conclusion
In an increasingly demanding and litigious society, it is
mandatory for the orthodontist to use carefully designed
ceramic brackets.
As a simple risk management strategy, ceramic brackets
that are not accompanied by detailed instructions for
bonding and bracket removal should definitely not be
used.
These products might not have been exposed to
appropriate, detailed testing procedures prior to their
sale. Thus, be alert and keep updated!
when we turn around and see the developments and
innovations in the material science, we stand with pride:
but the urge to make treatment still more comfortable and
less time consuming, have led us to the introduction of a
plethora of new orthodontic materials and products that
represent significant improvement over their
