Debonding techniques and enamel fracture patterns /certified fixed orthodontic courses by Indian dental academy

DEBONDING TECHNIQUES

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

 Introduction
 Mechanical

debonding of Steel Brackets
 Problems associated with debonding ceramic
brackets
 Mechanical debonding of ceramic brackets
 Electrothermal debonding of brackets
 Laser Debonding of Ceramic Brackets
 Chemical solvents for debonding ceramic brackets
 Finishing procedures during debonding.
 Effects of Debonding on Enamel
 Management of teeth with white spot lesions after
debonding
 References.

Introduction
 The

objectives of debonding are to remove
the attachment and all the adhesive resin
from the tooth and restore the surface as
closely as possible to its pretreatment
condition without inducing iatrogenic
damage.
 To obtain these a correct technique is of
fundamental importance, else it may be
unnecessarily time consuming and
damaging to enamel.

I .Mechanical Bracket removal :
A. Steel brackets
 Several

techniques have been described for
debonding brackets, and various designs of
orthodontic pliers have been designed for the
purpose.
 Ligature cutters: Some authors recommend using
ligature cutters to debond brackets: these work
perfectly well but can damage the beaks, which
can detract from the original purpose. Others have
expressed concern that enamel damage may be
caused by the beaks of ligature cutters used in this
way (Oliver, 1988).







Weingart pliers: A method for
removing brackets is to
squeeze together the wings
using Weingart pliers.
This transmits a shear force to
the composite adhesive and
breaks the bond.
Disadvantage : bracket wings
often become distorted,
altering the slot dimension,
making the bracket useless for
recycling


.
 Use

of Debonding pliers:
Recommended technique
in which the chisel
shaped beaks are placed
as close to the base of the
bracket as possible and a
peeling type force is
applied.
 Because metal brackets
are ductile, this force is
transmitted to the
adhesive bond, breaking
it.

 Lift-off

Debonding
Instrument: This a design
of pliers in which a tensile
force is placed on the
adhesive bond through a
wire loop hooked over the
bracket tie wings, pulling
the wings of the bracket
directly away from the
tooth surface.
 This method distorts the
brackets the least and is
preferred if recycling is a
consideration.

 Oliver








and Pal (AJODO July 1989) compared three

methods of debonding:
Method A— The mesial and distal wings of an edgewise
twin bracket are squeezed together with pliers. Solid
brackets are removed by placing the pliers occlusally and
gingivally.
Method B— A shear force is applied with the blades of the
debonding pliers or ligature cutters positioned at the
enamel/composite or composite/bracket interface.
Method C— Use of LODI. This may be used in two ways:
either the arch wire may be left in situ or the slot keeper (a
length of 0.018 ´ 0.022-inch wire embedded in a plastic
handle) may be placed in the bracket after arch wire
removal. In either case, the presence of a wire in the
bracket should help to maintain the slot dimensions.
The brackets tested were Rocky Mountain Bioprogressive
and Unitek Light Square.

 Results

: Method B produced the most
distortion, the majority of which occurred on
the base. All parts of the bracket were almost
equally affected with method A, whereas
method C produced wing distortion only.
 In general RM brackets distorted more often
than Unitek Light Square brackets and
premolar brackets distorted more often than
incisor or canine brackets.
 Most of the debonded brackets had increased
slot dimensions compared with control
brackets, the greatest being an increase of
0.032 mm.

 The

clinical significance of an increase in
slot dimension of this order (6.5%) will be
loss of effective torque from an arch wire.
 The authors concluded that if recycling of
brackets is considered, then use of Unitek
light square brackets and the lift off
debracketing instrument for bracket
removal is most advantageous.


 Coley-Smith

and Rock (BJO 1999)
compared two methods of debonding
(bracket removing pliers or a lift off
debonding instrument) in 507 metallic
brackets, with and without the archwire in
place during debonding.


 After

debond brackets were tested for slot
closure by the fit of rectangular test wires
from 0·016X 0·022 to 0·021X 0·025 inch in
size.
 The LODI produced few slot closures
sufficient to affect the fit of all but the
largest test wire.
 Bracket removing pliers used after removal
of the archwire produced significantly
greater numbers of slot closures and
distorted brackets.

 Ten

per cent of the
brackets debonded using
bracket removing pliers
had distorted bases, no
base damage was
produced by the LODI.
 When bracket removing
pliers are used, the
archwire should be left in
place at the time of debond
since this reduces the
number of distortions.

Why are ceramic brackets difficult to
debond?
 The

inert composition of the aluminum oxide
ceramic brackets makes chemical cohesion
between the ceramic base and the adhesive resin
impossible.
 Therefore, a silane coupling agent is used as a
chemical mediator between the adhesive resin and
the bracket base.
 The silane molecule is a bifunctional molecule;
one end is a reactive silanol group that can bind
tenaciously to glass, while the other end of the
molecule reacts with other acrylic resins and
polymerizes, producing a cohesive bond with the
resin material. www.indiandentalacademy.com

 The

base of each bracket is coated with silica glass
to promote bonding with the silanol functional
group of the silane molecule.
 The adhesion between the resin and the ceramic
bracket bases has increased to a point where the
most common site of bond failure during
debonding has shifted from the bracket baseadhesive interface to the enamel adhesive
interface, a less desirable site.
 This has led to an increase in the incidence of
bond failures within the enamel surface.


 Also,

though the tensile strength of the new
ceramics is greater than that of stainless steel, they
have lower fracture toughness, compared with
conventional stainless steel brackets.
 During loading, stainless steel will elongate
approximately 20% of its original length before
failing, while sapphire will elongate less than 1%
before failing.
 Thus, ceramics are more likely to fracture than
metals under the same conditions during
debonding.
 Clinically, this is seen most often at the tie wing
area.



A.Example of fracture of the Starfire bracket. B,
Example of fracture of the Allure bracket. C,
Example of fracture of the Transcend bracket.

 Condition

of the surface of the ceramic: A shallow
scratch on the surface or a microscopic crack will
drastically reduce the load required for fracture of
ceramic brackets.
 Stresses introduced during ligation and arch wire
activation, forces of mastication and occlusion,
and forces applied during bracket removal with
pliers or debracketing instruments are all capable
of creating cracks in ceramic brackets that may
lead to failure.


B.Mechanical debonding of ceramic
brackets.
 In

order to address the
problem of enamel
fracture during
debonding, various
manufacturers have
given their own
recommendations on
debonding.
 GAC recommends the
use of the ETM 346
plier for removal of
the Allure brackets .


ETM 346 plier

 The

Allure brackets are beveled on the
incisal and gingival edges for easy insertion
of the plier which is slowly squeezed to
remove the bracket.
 A-Company has produced a similar plier
with an additional shield to catch any
splinters which may fly off during
debonding.
 Unitek do not recommend the use of
conventional debonding tools with their
Transcend Series 2000 brackets.
 These brackets are mechanically retained,
and though strong in shear, are significantly
weaker in the tensile mode.

 Accordingly

Unitek have introduced a new
debonding tool, which applies a tensile force.
 This has been shown to produce less enamel
damage.
 Generally, cutting brackets off with gradual
pressure from tips of twin beaked pliers close to
the bracket adhesive surface is not recommended
as it could introduce horizontal enamel cracks.
 The use of mechanical debonding of ceramic
brackets carries the risk of bracket fracture and the
additional risk of injury to doctor or patient from
flying fragments.
 The remaining bracket may also have to be
removed with a diamond bur, which is time
consuming and injurious to pulp, if coolant is not
used.

 Recently,

2 new ceramic bracket designs were
introduced to the market in an attempt to minimize
the problems that are encountered by the
clinician.
 The Clarity bracket (3M Unitek) has a metal lined
arch wire slot which minimizes friction, and is
also suggested to help strengthen the bracket to
withstand routine orthodontic torque forces.
 It also incorporates a vertical slot, which is
designed to help create a consistent bracket failure
mode during debonding.


Facial (A), and lingual (B), views of the Clarity ceramic bracket.

 The

MXi (TP Orthodontics, Inc), on the other
hand,is an injection-molded polycrystalline
bracket that incorporates a polymeric base made
of a high strength epoxy resin that adheres to most
orthodontic adhesives.
 The polymeric base has a mesh architecture to
enhance bond strength. The base is sufficiently
flexible to allow plastic deformation at levels
similar to that of metal brackets.
 The ceramic/polymer interface is reinforced with
an amorphous glass layer, which is formed
integrally on the smooth ceramic surface through a
high-temperature sintering process.

Facial (A) and lingual (B) views
of the MXi ceramic bracket.

 Bishara

et al (AJODO 1999) compared the
debonding characteristics of the two brackets,
using their appropriate pliers.

The most efficient
method of debonding
the Clarity bracket is to
use the Weingart pliers
and apply pressure to
the tiewings.
Weingart pliers for debonding
Clarity brackets


ETM plier used to debond

The most efficient
method to debond
the MXi ceramic
bracket is to place
the blades of the
ETM 346 plier
between the bracket
base and the enamel
surface.

MXi ceramic brackets.

 Their

findings indicated that the mean shear
bond strength of the Clarity bracket (10.4
MPa)was greater than that of the MXi ceramic
bracket (7.6 MPa).
 These are more than the minimal force levels
suggested by Reynolds (5.9 to 7.8 MPa) as
being clinically acceptable for orthodontics.
 The Clarity brackets had a greater incidence
rate of partial bracket failure with the Weingart
pliers, as compared the to the MXi brackets in
which no failures were seen.

 ARI

scores indicated that, when debonding
these brackets with the appropriate pliers,
there was a greater tendency for most of the
adhesive to remain on the enamel.
 This has the advantage of protecting the
enamel surface and the disadvantage of
having more residual adhesive material
present that needs to be mechanically
removed by the clinician.

 The

Inspire monocrystalline bracket
manufactured by Ormco has also undergone
modification by reducing the area of
retentive beads on the bracket base by 20%
on the gingival side.
 Diaz and Swartz (JCO 2004) did lab and
clinical studies on the modified bracket and
reported a significant reduction in the force
required to remove the bracket in one piece
with the debonding plier.

II.Electrothermal debonding of brackets
 (Sheridan

et al., AJO 1986) developed an
alternative to conventional metal bracket removal,
known as electrothermal debonding.
 It is the technique of removing bonded brackets
from enamel surfaces with a cordless battery
device that generates heat.
 This heat (in the range of 232ºC) is transferred to
the bracket by a blade that is placed in the bracket
slot.
 The heat deforms the bracket/adhesive interface
and the bracket may then be removed without
distortion or excessive forces being applied to the
underlying enamel

Diagrammatic view of ETD blade engaging
bracket slot. A, Lock-on arm engaging incisal
wings of bracket; B, Lip shield; C, Heat element;
D, blade positioned in bracket slot.

, Battery-powered heat source. Index
finger is on "heat on demand" button.
Thumb is on "lock-on" extension

 Sheridan

et al (1986) reported that the mean
increase in pulpal temperature, when debonding
metal brackets with this method was 2.4 ºC; when
cooling water spray was used immediately after
debracketing, the mean increase was only 0.12ºC.
 These values are well within the biological limits
specified by Zach and Cohen (1965).
 Kearns et al (BJO 1997) compared the mechanical
and electrothermal debonding techniques for 3
varieties of ceramic brackets: Starfire
(monocrystalline, chemically bonded), Transcend
6000 (polycrystalline, micromechanically bonded)
and Fascination (polycrystalline, chemically
bonded).

reported that the shear forces recorded in
the mechanically debonded cohort did not
differ significantly between different bracket
types.(Mean 12.4 Mpa)
 There was a significant difference between
the shear forces recorded when the different
brackets were debonded electrothermally,
with the Fascination® group showing
significantly lower shear force levels (1.8
Mpa) than the other brackets.
 The shear force levels recorded for the
electrothermally debonded brackets (Mean
4.6 Mpa) were significantly lower than those
recorded for mechanically debonded groups
 They

 This

study showed a mean increase in
temperature higher than those found by other
workers using similar recording methods
 These values were similar to the 5·5°C limit
commonly accepted as being the level above
which some pulpal damage occurs.
 Jost-Brinkmann

et al (EJO 1997) did an in vivo study
in which 12 human premolars scheduled for
extraction were bonded with ceramic brackets which
were subsequently debonded using ETD. After 4
weeks, the teeth were extracted and histologically
examined. No signs of pulpal inflammation were
seen.

 Takla

and Shivapuja(AJODO 1995) performed an
in vivo study in which a total of 30 teeth
scheduled for orthodontic extractions were used.
 15 teeth were extracted 24 hours after ETD, 7
were extracted 28 to 32 days after ETD, and 8
were the control teeth and debonded by a
conventional method, with pliers.
 The pulp was normal in most cases in the control
group.
 There was significant hyperemia seen 24 hours
after debonding in teeth debonded by ETD.
 Teeth extracted 30 days after ETD showed varied
responses, ranging from complete recovery in
some cases to persistence of inflammation and
pulpal fibrosis. www.indiandentalacademy.com

30 days postdebond
case. Presence of
inflammatory cells
(Iymphocytes), and
vascular engorgement.

Photomicrograph 24
hours after debonding.
Vascular engorgement
and extravasation of
RBCs.

30 days post debond.
Normal pulp tissue with
minimal evidence of

inflammation.

 Teeth

subjected to the conventional debonding
were normal histologically.
 The authors proposed that patients with
compromised teeth that have large restorations or
a questionable pulpal status could behave more
adversely to this significant amount of heat
applied.
 In compromised cases and on older patients,
performing pulp vitality tests before ETD may
inform the operator about the status of the pulp
and thereby prevent the potential for pulpal
damage.

 Knight

et al, AJO-DO 1997 studied the safety of
electrothermal debonding of ceramic brackets
from teeth with ceramic veneers, as compared
with metal brackets.
 Results of this study suggest that metal brackets
cannot be predictably debonded without producing
either veneer damage, if debonded mechanically
or electrothermally, or potential pulp damage, if
debonded electrothermally.
 Ceramic brackets may be removed without
causing either veneer or pulpal damage, if
debonded electrothermally.
 The current recommendation for bonding to a
ceramic veneer is to place a ceramic bracket that
may be subsequently electrothermally debonded.

 Luthra

S et al (1998)
investigated the pulpal
damage associated with
electrothermal debonding.
 A total of 50 teeth from 14
patients, nine of whom were
females and five were males,
Dentaurum Electrothermal debonding
who had to undergo
unit used in the study.
extractions for orthodontic
purposes were used to
provide the histologic
material.
 All 50 teeth were bonded
with Fascination ceramic
brackets.

 30

teeth were debonded
using the Dentaurum
Electrothermal debonding
unit.
 Ten teeth were extracted 24
hours after ETD, ten were
extracted 28-32 hours after
ETD, and ten were
extracted 56 days after
ETD.
 20 teeth served as controls
and were debonded by
conventional methods.

Debonding procedure with the
electrothermal debonding unit.








The 24 hour group and the
28-32 day group debonded
by ETD, on histologic
examination, showed
dilatation of the pulpal
vessels and engorgement
with RBC’s.
The 56-day sample in
general showed a normal
pulpal architecture.
It was concluded that the
pulp is predominantly
unaffected by
electrothermal debonding
of brackets, with most
changes being of a
reversible nature.

III. Ultrasonic debonding of ceramic
brackets






Krell, Courey, and Bishara AJODO 1993 described the use of 2
Ultrasonic tips for debonding of
brackets.
Bracket removal was initiated at
the incisal portion of the bracket,
with the KJS tip, the straight
chisel bevel directed toward the
bracket itself.
After placing the tip at either the
gingival or incisal edge, the
ultrasonic unit was activated while
moving the tip in a mesial to distal
direction.





This rapidly created a
groove in the composite.
On gaining approximately
a 0.5 to 1 mm "purchase
point," a rocking motion
was then incorporated
until bond failure
occurred.
Alternating the use of the
KJS with the KJC tip
facilitated bracket
removal.


 Bishara

and TruloveAJO-DO 1990 Sep (263 273) reported that although the incidence of bond
failure at the enamel-adhesive interface is high
when the ultrasonic technique is used, the
likelihood of enamel damage with this technique
is relatively minimal.
 This is because the force levels required to achieve
bond failure are significantly reduced with the
ultrasonic tips compared with the force needed for
the conventional removal methods.
 A disadvantage of ultrasonic method is the
increased amount of time required for debonding.

Laser Debonding of Ceramic
Brackets
 The

discovery of optic laser technology began
with the invention of ruby lasers in the early
1960s.
 During the 1980s and early 1990s, introduction of
lasers into dentistry was approved by the USFDA.
 Since the early 1990s, lasers have been used
experimentally for debonding ceramic brackets.


Mechanism of Laser debonding:
According to Tocchio et al (AJODO 1993),
laser energy can degrade the adhesive resin
by 3 methods
 Thermal softening
 Thermal ablation
 Photoablation.


 Thermal

softening occurs when the laser heats the
bonding agent until it softens.
 Clinically this results in the bracket succumbing to
gravity and sliding off the tooth surface.
 It is a relatively slow process, which means it can lead to
a large rise in both tooth and bracket temperature.
 Thermal ablation occurs when heating is fast enough to
raise the temperature of the resin to its vaporization
range before debonding by thermal softening occurs.
 This results in the bracket being blown off the tooth
surface.
 Photoablation also results in the bracket being blown off
the surface of the tooth.

 It

occurs when very high energy laser light interacts
with the adhesive material and the energy level of the
bonds between the adhesive resin atoms rapidly rises
above their dissociation energy levels, resulting in
decomposition of the material.
 Tocchio et al suggested that in monocrystalline
brackets debonding takes place by ablation,while for
polycrystalline brackets it is due to thermal softening.
 Strobl et al ( AJODO 1992) showed that with the aid
of lasers, debonding force is significantly reduced,
when using a Bis GMA adhesive resin.
 There was a difference in debonding characteristics
for mono and poly crystalline brackets.





Using CO2 lasers, at a
total energy of 15 Joules,
there was a 5.2 fold
reduction in debonding
force for monocrystalline
brackets but only a 1.3
fold reduction for
polycrystalline brackets.
A fixed laser energy
power level of 14.1 watts
applied for 2 seconds was
selected as most optimal.

Why do poly and monocrystalline
brackets debond differently?
 The

different behaviors observed are, in part, due to
differences in the design (shape and dimensions) of
the two brackets, as well as in their different
microscopic structure.
 The polycrystalline material consists of an
agglomerate of small microcrystals with random
orientation, size distribution, and shape that result in a
much higher energy diffusion (heat and light) than the
basically homogeneous monocrystalline brackets.
 Heat transmits through the body of the
monocrystalline bracket with much less lateral
spreading, which results in a significantly hotter spot
at the bracket-adhesive interface.

 Since

the adhesive must be heated to
approximately 150° to 200° C before significant
softening of the composite occurs, a more
localized hot spot is more effectively obtained
with the monocrystalline brackets.
 This is supported by the observation that at higher
laser energy levels, the monocrystalline brackets
have a tendency, during the debonding process, to
show plasma or plume formation, occasionally
associated with the cracking of the bracket along
the wire slot.
 The polycrystalline brackets showed no such
behavior at the same energy levels.

 In

comparison to the lased group, the non lased
group showed a slightly higher incidence of
bracket failure.
 Strobl et al compared the use of YAG laser with
that of CO2 laser and found that with the YAG
laser, only 15% to 26% of the incident light was
absorbed by the adhesive material and changed to
heat, while the rest reached the enamel surface,
potentially damaging the pulp.
 Other authors such as Ma et al (AJODO 1997),
Tocchio et al (AJODO 1993), also showed that
CO2 laser is effective for debonding ceramic
brackets.

Iatrogenic effects of laser
 When

laser radiation is applied to a ceramic
bracket, energy is absorbed and converted into
heat
 There is a potential for this heat to propagate to
the tooth structure and eventually lead to pulp
damage.
 Zach and Cohen (1965) have shown in monkeys,
that up to 1.8 ºC increase in intra pulpal
temperature results in no pulpal damage, while
with increase of 5.5 ºC , there was pulpal necrosis
in 15 % of teeth.

 Ma

et al ( AJODO 1997) showed that there is a
linear relationship between lasing time and
increase in intra pulpal temperature.
 They found that application of an 18W CO2 laser
for 2 seconds allowed debonding with a 1.48 MPa
tensile load, with a mean intrapulpal temperature
increase of 1.1ºC.
 Obata et al (1995) found no histological
differences in the tooth pulps of lased and non
lased teeth.
 Use of Super pulse lasers in surgery has been
reported by Ben Baruch et al ( 1988) and Ho et al
(1995). The super CO2 laser has short laser pulses
of microseconds which allow for some time for
tissues to cool, limiting damage to the pulp.

 Obata

et al (EJO 1999) showed that super pulse
CO2 laser was able to create debonding at 2 watts
within a period of less than 4 seconds. During this
period it caused increase in intra pulpal
temperature of 1.4º C, which was within
acceptable physiologic limits.
 Super CO2 lasers may also induce vibration in the
adhesion material , thus decreasing power output,
and minimizing temperature increase.
 In comparison, normal pulse CO2 lasers are more
likely to cause thermal necrosis and charring .


Time lag between lasing and debonding:
 Abdul Kader and Ibrahim (1999) reported that
irrespective of lasing time, there was a significant
increase in required debonding force, 1 minute
after lasing, compared to immediately after lasing.
 Therefore, debonding ceramic brackets one by one
after lasing, before the adhesive resin material
resolidifies, requires less debonding force.
Effect of Laser on different bonding adhesives:
 The popularly used adhesive materials for ceramic
brackets are Concise, a Bis GMA resin with filler,
and Super Bond : an MMA resin with 4META
and no filler.

 Lasers

are very effective in debonding ceramic
brackets with either of the two, resulting in no
enamel fractures.
 Mimura et al (AJODO 1995) found however, that
using laser it is easier to debond brackets bonded
with Super-Bond.
 In addition,laser tends to remove the Bis GMA
resin along with the bracket, while with MMA
resin, the adhesive remained on the tooth.
 They thus concluded that with laser aided
debonding of ceramic brackets, use of MMA is
safer than Bis GMA.

Azzeh and Feldon (AJODO 2003) comprehensively
reviewed the literature relating to laser debonding of
ceramic brackets, and made the following
conclusions:
 Time and force spent to debond ceramic brackets is
significantly less with the use of lasers, as also is the
risk of enamel damage and bracket fracture.
 CO2 super pulse laser is superior to normal pulse CO2
lasers and YAG lasers.
 MMA resins are recommended over Bis GMA resins.
 Use of monocrystalline brackets is suggested over
polycrystalline brackets.
 Ceramic brackets should be irradiated and debonded
one by one immediately after laser exposure.

Risk of pulpal damage is significantly
reduced if the following are used
 Super pulse CO2 laser at 2W for less than 4
seconds.
 CO2 laser (10.6 microns) at 3 W for 3
seconds
 CO2 laser (normal pulse) at 18W for 2
seconds


A

IV. Chemical solvents for debonding
ceramic brackets

peppermint oil material has been marketed previously
as a debonding agent.
 Larmour , McCabe Gordon (BJO 1998) assessed ex
vivo the effects of peppermint oil application on the
debond behaviour of ceramic brackets compared with
ethanol and acetone which are recognized softening
agents.
 One hour placement in peppermint oil produced the
lowest mean and maximal debond forces (77 and 114 N,
respectively).
 Placement in peppermint oil produced the lowest levels
of retained resin.
 There was no evidence of enamel fracture with any of the
groups, but bracketwww.indiandentalacademy.com a problem.
fracture remained

Finishing procedures during debonding.






Retief and Denys (Angle O 1979) described
the removal of direct bonded attachments and
the finishing of underlying enamel as an acute
clinical problem.
Using the scanning electron microscope they
concluded that debonding pliers, scalers, and
diamond finishing burs should not be used to
remove the remaining resin after debonding
because they cause deep gouges in the enamel.
They recommended using a 12-bladed
tungsten carbide bur at high speed with
adequate air cooling to remove the bulk resin.
finishing the residual resin and underlying
enamel with graded polishing discs or
ceramiste wheels with light pressure and
adequate air cooling. www.indiandentalacademy.com

 Final

finishing may be done with a water slurry of
pumice applied with a rubber cup.
 Other authors such as Zachrisson and Artun (AJO
1979) found that tungsten carbide bur at low speed
produced the finest scratch pattern and the least
enamel loss.
 Rouleau et al (AJO 1982) on the other hand concluded
that the instrument leaving the smoothest enamel
surface was the tungsten carbide ultra-fine bur
operated at high speed with water spray.
 Hosein et al (AJODO 2004) compared enamel loss
during debonding of brackets bonded with
conventional and self-etch primers and reported that
for both groups, most enamel loss occurred with high
speed TC bur or ultrasonic scaler, while least occurred
with slow speed TC bur.

Effects of Debonding on Enamel
Features of Normal enamel:
 Normal enamel varies
considerably in appearance
between young, adolescent and
adult teeth.
 Young teeth that have just erupted
into the oral cavity are
characterised clinically by
perikymata, that run around the
tooth in its entirety.
 Under scanning electron
microscope open enamel prisms
are seen as small holes.

 In

adult teeth, the perikymata
are worn away and replaced by
a scratched pattern.Cracks are
frequently visible, electron
microscopy shows no evidence
of prism ends or perikymata.
 Teeth in adolescents reflect an
intermediate stage.
 Mannerberg (1960) reported
that normal wear of enamel is
between 0-2 microns per year.
On the other hand, a sand paper
Scratched pattern of adult enamel
disk that touches a tooth for
only a fraction of a second
leaves scratch marks up to 5
microns deep.

Influence of different debonding instruments on
enamel:
 Zachrisson and Artun (AJO 1979) showed that diamond
instruments produced coarse scratches and gave a
deeply marred apppearance to enamel.
 Medium sandpaper disks and a green rubber wheel
produced similar scratches that could not be polished
away.
 Fine sandpaper disks produced several considerable and
some even deeper scratches.
 Plain cut and spiral fluted tungsten carbide burs
operated at about 25000 rpm were the only instruments
that provided a satisfactory surface appearance.
 However none of the instruments left the virgin tooth
surface with its perikymata intact.

 Amount

of enamel lost in debonding:
 The amount of enamel lost during debonding is related
to several factors such as instruments used for
prophylaxis, debonding, and the type of adhesive resin
used.
 Initial prophylaxis with a bristle brush for 10 –15
seconds per tooth may abrade away up to 10 microns of
enamel, compared to rubber cups which may abrade
upto 5 microns of enamel.
 Cleanup of unfilled adhesive resin may be accomplished
with hand instrumentation only, and is associated with
loss of 5-8 microns of enamel.
 Adequate removal of filled resin generally needs rotary
instrumentation and may involve 10-25 microns of
enamel loss.

 In

vitro studies using an optical system of a
profile projector and steel reference markers
show that total enamel loss for filled reins
ranged from 30-60 microns depending upon
the instrumentation. (Pus and Way, AJO
1980; Thompson and Way, AJO 1981).
 On the other hand,Van Waes et al (AJODO
1997) using computerized 3 D scanning
over the tooth surface found a more limited
enamel loss ( 7.4 microns) if tungsten
carbide burs were used carefully.

Enamel tearouts:
 Localized enamel tearouts have been reported to
occur during debonding of metal and ceramic
brackets.
 These are partly related to the type of filler
material in the adhesive resin and to the location
of bond breakage.
 Smaller filler particles may penetrate deeper into
the etched enamel than macrofillers.On
debonding the small fillers reinforce the adhesive
tags. Macrofillers, on the other hand create a
more natural break point in the enamel adhesivesurface.

Ceramic brackets using chemical retention
cause enamel damage more often,
probably because the point of bond
breakage is at the enamel-adhesive rather
than adhesive-bracket surface.
 Clinical implications:
1. Use brackets that have mechanical
retention and debonding techniques that
leave all or majority of composite on the
tooth.
2. Avoid scraping away adhesive remnants
with hand instruments.



Enamel cracks
 Cracks,

occurring as split
lines in the enamel are often
overlooked at the clinical
examination, and they do
not show up on routine
intra-oral photographs.
 Finger shadowing in good
light or preferably fiberoptic
transillumination is needed
for proper visualization.







1.

There is a distinct possibility that the sharp sound
sometimes heard on removal of bonded
orthodontic brackets with pliers is associated
with the creation of enamel cracks.
Zachrisson et al (AJO 1980) studied normal as
well as debonded teeth and reported that the
occurrence of vertical cracks is quite common,
especially in maxillary central incisors and
canines.
Clinical implications;
The orthodontist should review his debonding
technique if he notices;
Several distinct enamel cracks on the patient’s
teeth after debonding, especially on teeth other
than maxillary canines and central incisors

 2.

If cracks are detected in a predominantly
horizontal direction.
 With ceramic brackets, the potential for creating
cracks is far higher because of their lack of
ductility, which may generate excessive stress at
the adhesive –enamel interface.
 Note: It is important for the orthodontist to notify
the patient about any cracks present prior to
treatment, in order to avoid being blamed for it
post-treatment.

Enamel loss associated with adhesive
removal from teeth with white spot lesions
 Development

of white spot lesions during
orthodontic treatment is almost inevitable in
patients with poor oral hygiene.
 These can occur within only 2-3 weeks of plaque
accumulation in gingival areas of teeth.
 Studies have shown loss of upto 10% of inorganic
content in these lesions, which has led to concern
about further enamel loss during debonding.
 Tufekci et al (AJO DO 2004) performed a study to
assess the effect of debonding on teeth with
WSL’s.

 They

found that in teeth with white spot
lesions, the use of abrasive (Sof-Lex) disks
was associated with more enamel loss than
slow speed TC burs.
 Based on this, use of slow speed TC bur
was recommended for adhesive removal in
affected teeth.


Management of teeth with white spot
lesions after debonding:
 Artun

and Thylstrup ( 1986) found that removal of
cariogenic challenge after debonding results in the
arrest of further demineralization, and gradual
regression of lesion clinically takes place because
of surface abrasion as well as some deposition of
minerals.
 Visible white spots that develop during
orthodontic therapy should not be treated with
concentrated fluoride agents immediately after
debonding, because this procedure will arrest the
lesion and prevent complete repair.

 At

present, 2-3 months of good oral hygiene
without fluoride supplementation should be
recommended post debonding.
 More fluoride may tend to precipitate
calcium phosphate onto the surface and
limit remineralization of the superficial part
of the lesion, and the optical appearance of
the white spot is not reduced.

Microabrasion
 Done

when remineralizing capacity of oral fluids is
exhausted and white spots established.
 Microabrasion: A gel prepared from 18% HCl,
pumice and glycerine is applied professionally with a
modified toothbrush tip for 3-5 mins; followed by
rinsing.
 This is effective for removing white spots and brownyellow enamel discolorations.
 In case of more extensive mineral loss, grinding with
diamond burs or composite restorations may be
required..

White spot lesions

After micro-abrasion


References
 Hosein

I, Sherriff M, Ireland AJ. Enamel loss during
bonding, debonding, and cleanup with use of a selfetching primer.Am J Orthod Dentofacial Orthop.
2004 Dec;126(6):717-24.
 Diaz C, Swartz M. Debonding a new ceramic bracket:
a clinical study. J Clin Orthod. 2004 Aug;38(8):442-5
 Tufekci E, Merrill TE, Pintado MR, Beyer JP,
Brantley WA. Enamel loss associated with
orthodontic adhesive removal on teeth with white
spot lesions: an in vitro study. Am J Orthod
Dentofacial Orthop. 2004 Jun;125(6):733-9.
 Azzeh E, Feldon PJ. Laser debonding of ceramic
brackets: a comprehensive review. Am J Orthod
Dentofacial Orthop. 2003 Jan;123(1):79-83.

 Coley-Smith

A, Rock WP. Distortion of metallic
orthodontic brackets after clinical use and debond
by two methods. Br J Orthod. 1999 Jun;26(2):1359.
 Bishara SE, Olsen ME, VonWald L, Jakobsen JR.
Comparison of the debonding characteristics of
two innovative ceramic bracket designs.Am J
Orthod Dentofacial Orthop. 1999 Jul;116(1):8692.
 Obata A, Tsumura T, Niwa K, Ashizawa Y,
Deguchi T, Ito M. Super pulse CO2 laser for
bracket bonding and debonding. Eur J Orthod.
1999 Apr;21(2):193-8
 Turner PJ. Trouble-free debonding in
orthodontics: 2. Dent Update. 1996
Dec;23(10):426-9.

 Jost-Brinkmann

PG, Radlanski RJ, Artun J, Loidl H.
Risk of pulp damage due to temperature increase
during thermodebonding of ceramic brackets. Eur J
Orthod. 1997 Dec;19(6):623-8.
 Bishara SE, Olsen ME, Von Wald L. Evaluation of
debonding characteristics of a new collapsible ceramic
bracket. Am J Orthod Dentofacial Orthop. 1997
Nov;112(5):552-9.
 Kearns HP, Sandham JA, Bryan Jones W, Lagerstrom
L. Electrothermal debonding of ceramic brackets: an
ex vivo study.Br J Orthod. 1997 Aug;24(3):237-42.
 Lee-Knight CT, Wylie SG, Major PW, Glover KE,
Grace M. Mechanical and electrothermal debonding:
effect on ceramic veneers and dental pulp.Am J
Orthod Dentofacial Orthop. 1997 Sep;112(3):263-70.

 Sinha

PK, Nanda RS. The effect of different bonding
and debonding techniques on debonding ceramic
orthodontic brackets. Am J Orthod Dentofacial Orthop.
1997 Aug;112(2):132-7
 Ma T, Marangoni RD, Flint W. In vitro comparison of
debonding force and intrapulpal temperature changes
during ceramic orthodontic bracket removal using a
carbon dioxide laser. Am J Orthod Dentofacial Orthop.
1997 Feb;111(2):203-10.
 Takla PM, Shivapuja PK. Pulpal response in
electrothermal debonding. Am J Orthod Dentofacial
Orthop. 1995 Dec;108(6):623-9.
 Seema Luthra, K Vighnesh, Nirmala Rao, Valiathan
Ashima. Ceramic brackets and their electrothermal
debonding-an in vivo evaluation. TIBAO 1998 Vol 12,
No.2. 47-49.









Tocchio RM, Williams PT, Mayer FJ, Standing
KG. Laser debonding of ceramic orthodontic
brackets.Am J Orthod Dentofacial Orthop. 1993
Feb;103(2):155-62
Bishara SE, Trulove TS. Comparisons of
different debonding techniques for ceramic
brackets: an in vitro study. Part I. Background
and methods. Am J Orthod Dentofacial Orthop.
1990 Aug;98(2):145-53.
Graber, Vanarsdall. Orthodontics: Current
Principles and Technique. 4th Edition (Mosby)
2005.
Krell KV, Courey JM, Bishara SE. Orthodontic
bracket removal using conventional and
ultrasonic debonding techniques, enamel loss,
and time requirements Am J Orthod Dentofacial
Orthop. 1993 Mar;103(3):258-66.

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