materials used for bonding, steps in bonding technique, direct and indirect bonding. recent advances in binding materials

1. B Y :
D R . A N J A L I R A J E S H K U M A R J A I S W A L
2 N D Y E A R P O S T G R A D U A T E S T U D E N T
BONDING IN
ORTHODONTICS

2. CONTENTS
• Introduction and history
• Advantages
• Disadvantages
• Bonding materials
– Adhesives
– Etchants
– Primers
– Composite resins
• Chemically cured bonding system
• Light cured bonding system
• Dual cured bonding system
• Thermo cured system
– Curing lights
• Bonding procedure
• Bonding to artificial tooth surfaces
• Indirect bonding
• References

3. INTRODUCTION and HISTORY
• Around 1970 several articles appeared on
bonding attachment with different adhesives.
• “Miura et al” described an acrylic resin
(orthomite), using modified trialkayl borane
catalyst that proved to be particularly
successful in bonding plastic brackets and for
enhanced adhesion in the presence of
moisture.

4. • Also diacrylate resins, as both sealants and
adhesives, were introduced in orthodontics.
• The most commonly used resin is Bowen’s
resin or Bis GMA (Bis phenol-A glycidyl
dimethacrylate, was designed to improve
bond strengths and increase dimensional
stability by cross linking.

5. • Thus in the early 1970s, a considerable number
of preliminary reports were published on
different commercially available direct or indirect
bonding system.
• It was not until 1977, however that first detailed
post treatment evaluation of direct bonding over
a full period orthodontic treatment in a large
sample of patients was published .
• Today most orthodontist directly or indirectly
bond attachments to the teeth.

6. ADVANTAGES
1. Aesthetically superior to banding.
2. Faster and simpler, easy to manipulate
3. Less discomfort to patient since it does not
require separation of teeth for seating of
bands
4. Reduced caries risk under loose band.
5. Arch length is not encroached since no band
material needs to be inserted on Interproximal
surfaces.

7. 6. Consequently no band spaces are present at
debanding
7. Proximal stripping is possible if required during
treatment.
8. Interproximal areas are accessible for composite
buildup.
9. Brackets can be attached on partially erupted or
fractured teeth.
10. Relatively less oral hygiene problems due to
miniature size of brackets.
11. Use of ceramic and lingual brackets became
reality due to feasibility of bonding.

8. DISADVANTAGES
1. Weaker attachment than cemented band.
2. Technique sensitive procedure
3. Enamel demineralization and white spots
around bonded attachments
4. Smaller size of brackets and better access to
tooth cleaning surfaces does not guarantee
better gingival health.

9. 5. Loss of enamel with etching and during
debonding although recovery is a possibility
with re-mineralization
6. Bracket bond failures do occur and
subsequent bonds are not equally strong.

10. DENTIN BONDING AGENTS
• In 1995 Michael Buonocore was the first to
describe the acid etch technique for enamel
bonding. He reported that the adhesion of
acrylic resins to enamel could be improved by
conditioning the enamel with a solution of
85% phosphoric acid.

11. • The 1st dental adhesive bonded resins to
enamel only with little or no dentin adhesion
or sealing of dentin margins.
• Subsequent generations of dental adhesives
have dramatically improved the bond strength
to dentin and the sealing of dentin margins
while retaining a strong bond to enamel.

12. First generation adhesives
• Early dentin bonding agents were based on
the successful model of silane coupling
agents.
• Silane coupling agents are used to bond the
inorganic filler to the matrix resin in
composites, to bond porcelain laminate
veneers through resins cements to acid-
etched enamel, and to repair fractured
porcelain with composites.

13. • This could chelate with calcium on the tooth
surface to generate water-resistance chemical
bonds of resins to dentinal calcium.
• But it showed poor clinical results.

14. Second generation adhesives
• Second-generation bonding agents include
NPG-GMA (the adduct of N-phenyl glycine and
glycidyl methacrylate), and phenyl-p, 2-
methacryloxy phenyl phosphoric acid.
• Its mechanism of action was based on the
polar interaction between negatively charged
phosphate groups in resin and positively
charged Ca++ in the smear layer.

15. Third generation adhesives
• The third generation of dentin adhesives was also
based on the continued use of an acid group to react
with Ca++ ions and a methacrylate group to
copolymerize with unfilled resin that was applied
before placement of the composite restorative
material.
• The third generation of adhesive procedures for
conditioning dentin involved two approaches:
1) Modification of the smear layer to improve its
properties or
2) Removal of the smear layer without disturbing the plugs
that occluded the dentinal tubules

16. • Adhesive is unfilled or partially filled resin that
may contain some component of primer (eg
HEMA) in an attempt to promote increased
bond strength.

17. Fourth generation adhesives
• When primer and bonding resin are applied to
etched dentin, they penetrate the intertubular
dentin forming a resin dentin interdiffusion
zone or hybrid layer.
• They have ability to bond as strongly to dentin
as to enamel (total etch)

18. Fifth generation adhesives
• Unique feature is the combination of the priming
and bond resin application steps, resulting in a
one component formula.
• Most commonly used and probably the most
successful system.
• These bonding systems create a mechanical
interlocking with etched dentin by means of resin
tags, adhesive lateral branches and hybrid layer
formation..

19. Sixth generation adhesives
• They are self etching adhesives ( Etch & prime
simultaneously).
• The bonding agent is either applied after the
self etching primer or mixed together before
single application.
• Dissolve the smear layer when applied and do
not require rinsing.

20. • Minimize post operative sensitivity as they do
not expose dentinal tubules.
• Bond strength to enamel and superficial
dentin are typically greater than deep dentin.

21. Type I Type II
Self etching primer and adhesive Self etching adhesives
Have components
Liquid1-acidic primer
Liquid2- adhesives that applied separately
to the tooth
Two bottles or unit dose containing acidic
primer and adhesive, first mixed and then
applied
Generally compatible with self-cured
composite
Not compatible with self cured composite

22. Seventh generation adhesives
• Self etching adhesives
• Requiring no mixing
• Not compatible with self-cured composite
cores or resin cements
• Single bottle containing acidic adhesive
• Bond strengths and marginal sealing to be
equal to 6th generation system.

24. Classification based on number of
steps
Generation Steps Description
1st 3 Etch enamel, apply primer and adhesive
2nd 3 Etch enamel, apply primer and adhesive
3rd 3 Etch enamel, apply primer and adhesive
4th 2 Total etch, apply primer and adhesive
5th 2 Total etch, apply adhesive
6th 1 or 2 Apply self etch adhesive
7th 1 Apply self etch adhesive

25. ETCHANTS
• In restorative dentistry the highest bond strength to
tooth structure is desirable.
• In contrast, the orthodontic bond strength must be
sufficient to retain the brackets but low enough to
allow easy clean-up of adhesive when the case is
completed and the brackets are removed.
Maleic Phosphoric Nitric acid
10% 37% 2.5%

26. • Most orthodontic adhesives are sold with a 37%
concentration of phosphoric acid with the minimum
etching time.
• Permanent teeth require 30 seconds and deciduous
teeth 60-90 seconds. There is no evidence that
indicates any significant increase in bond strength
between 15 and 90 seconds.
• If etched for more than 90 seconds, an insoluble
calcium phosphate salt crystal forms on the enamel
that is impervious to resin, resulting in reduced bond
strength.
• In general, either a liquid etch or a gel etch may be
used. A gel etch is indicated when the etching is in an
isolated area or where control of the etching
material is imperative.

27. Patterns of etching
• The morphological changes produced on the
enamel surface by etching have been studied
under scanning Electron Microscopy
(Gwinnett, Silverstone and Others, Retief and
Austin).

28. Type 1 etching pattern
• Prism core material is preferentially removed
• Leaving the prism peripheries relatively intact
• Resulting in a “honeycomb” appearance.

29. Type 2 etching pattern
• The peripheral regions of the prisms are
dissolved preferentially
• Leaving the prism cores relatively intact
• Resulting in a “cobblestone” appearance.

30. Type 3 etching pattern
• Surface loss occurs without exposing
the underlying enamel prisms.
• Gwinnett (1971) demonstrated that
this etching pattern is usually
observed at the cervical aspects of
teeth where the enamel prisms do
not extend to the surface.
• Denys and Retief (1982) showed
however, that the type 3 etching
pattern is not confined to the
cervical regions but is also found on
other aspects of an etched enamel
surface.

31. Iatrogenic effects of etching
• Fracture and cracking of enamel upon debonding
• Increased surface porosity – possible staining
• Loss of acquired fluoride in outer 10 m of enamel
surface
• Loss of enamel during etching
• Resin tags retained in enamel – possible
discoloration of resin
• Rougher surface if over-etched.

32. Alternatives to acid etching
• Crystal growth
• Sand blasting / Air abrasion
• Laser etching

33. Crystal-growing solutions
• A proposed alternative to etching enamel for
retention of an adhesive is to grow crystals on the
enamel surface. This technique is called crystal
bonding.
• Potential advantages of crystal bonding include
easier debonding, less residual adhesive left on the
tooth and less damage to enamel

34. • Crystal bonding involves application to enamel
of a poly acrylic acid solution containing
sulfate ions, which causes growth of calcium
sulfate dihydrate crystals on the enamel
surface.
• These crystal in turn retain the adhesive.
• Crystal bonding produces bond strengths of
60-80% of the bond strength obtained with
acid etching, it is not yet considered a
practical technique.

35.  Crystal growth – Procedure
1. One drop of viscous liquid placed on tooth
surface
2. Left undisturbed for 30 sec
3. No mechanical agitation
4. Rinsed for 20 sec
5. Forceful water spray to be avoided as it will
break crystals
6. Dull whitish deposit
7. Bracket bonded in usual way.

36. Advantages of Crystal growth
• Debonding quicker and easier
• No damage to enamel
• Minimal effect on outer fluoride containing enamel
• No resin tags left behind
• Possibility of incorporating fluoride in crystal interface –
anticariogenic action.

37. Sand blasting / Air abrasion
• Makes use of high speed stream
of aluminium oxide particles (
50-90 um) propelled by air
pressure
• Produces rough surface
• Used for cavity preparation
• Remove old composite resin
• Improve the retentive surface of
loose bracket

38. Acid etching Crystal growth Sand blasting
Enamel loss Remineralized Less Controlled by
operator
Bond strength Optimum Lower than AE Lower than AE

39. Laser etching
• Causes thermally induced changes within the
enamel to a depth of 10 to 20 m, depending
on the type of laser and the energy applied to
the enamel surface.
• Etching takes place through a process of
continuous vaporization of water trapped
within the hydroxyapetite matrix.

40. • The surface produced by laser etching is also
claimed to be acid resistant as a result of the
modified calcium-to-phosphorus ratio, a
reduced carbonate-to-phosphate ratio, and
the formation of more stable and less acid-
soluble compounds, thus reducing
susceptibility to acid attack and caries.
• eg. Er:YAG laser

41. PRIMERS
• Primers are hydrophilic monomers usually carried via
solvent and promote bonding to substrate by:
enhancing wettability and adaptation of resin to the
conditioned enamel.
• Acidic primer containing carboxylic acid groups are
used in self etching bonding agents. The solvent used
in primers are acetone or ethanol-water.

42. Eg of non acidic primers;
1)HEMA: 2hydroxy ethyl methacrylate
2)NPG-GMA: N-phenyl glycine and glycidl
methacrylate
3)BPDM: biphenyl dimethacrylate

43. Self Etch Primer
• Saves time (8mins for full mouth bonding)
• Combines the conditioning and priming
agents into a single acidic primer solution for
simultaneous use on both enamel and dentin.
• The active ingredient dissolves calcium from
hydroxyapetite, forms a complex and is
incorporated into the network when primer
polymerizes.

44. • An irregular but smooth hybrid layer, 3 to 4
microns thick, and irregular tag formation with
no apparent indentations of enamel prism or
core material are found.
• Majority of bond may be of a chemical bond
with the calcium in the enamel.

45. Self Etch Primer
Composition:
• Methacrylate phosphoric acid ester
• Phosphine oxide
• Parabenes
• A fluoride complex
• Water

46. Procedure For Self Etch
• Teeth are pumiced
• Self etch primer gently swirled on to each enamel surface for
2 to 5 secs
• As pH rises , etchant is converted to primer
• Primer is thinned with burst of air
• No rinsing with water
• Bracket then bonded in usual way.

47. Procedure for self etch primer

48. • 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 the network when the primer
polymerizes.
• Etching and monomer penetration to the
exposed enamel rods are simultaneous and
the depth of etch and primer penetrations are
identical.

49. Moisture insensitive primers
• Hydrophilic primers that can bond in wet fields have
been introduced.
• Suitable in difficult moisture-control situations.
• For optimal results, they should be used with their
respective adhesive resins.
• They polymerize in presence of slight amount of
water, but will not overcome routine saliva
contamination.

50. ADHESIVES
• Unfilled resins have traditionally been utilized as
bonding agents in resin composite bonding system.
• Two basic types of dental resins are currently in use
for orthodontic bracket bonding. Both are polymers
and classified as acrylic or diacrylate resins.
• The acrylic resins are based on self curing acrylics
and consist of methyl methacrylate monomer and
ultra fine powder. Most of diacrylate resins are based
on the acrylic modified epoxy resin: bisGMA or
Bowens resin .

51. • Both types of adhesives exist in either filled or
unfilled forms. The filled diacrylate resins of bis GMA
type have the best physical properties and are the
strongest adhesives for metal brackets. Acrylic or
combination resins have most successful with plastic
brackets.
• The clinical implications that adhesives with large
particle fillers are recommended for extra bond
strength, but care full removal of excess important
because such adhesives accumulate plaque more
easily than do others.

52. Compositions of composite resins
1) Resin matrix / binder
2) Filler
3) Coupling agent
• They also contains:
• Hydroquinone (inhibitors)
• UV absorbers (improve color stability)
• Opacifiers (titanium dioxide, aluminium oxide)
• Color pigment (to match tooth color)

53. Classifications of orthodontic adhesive system
Based on polymerization initiation mechanisms,
orthodontic adhesives may be classified into;
• Chemically activated (chemically cured, auto cured,
self cured)
– Two paste system
– One paste system
• Light cured (photo cured)
• Dual cured
• Thermocured

54. Chemically activated
• The chemically activated orthodontic adhesives
employ Benzoyl peroxide an initiator which is
activated by a tertiary aromatic amine such as
dimethyl –p-toludine. Initiation occurs from mixing of
the paste and liquid components of these systems,
and free redicles are formed by multi step process.

55. Two phase (two paste) adhesive system;
• The two phase products were used in the early days
of bonding . The application involves mixing of the
paste and liquid components. The manipulation
process is problematic , time consuming .
• Mixing of the two component produces surface
porosity and voids in the bulk material.

56. One phase (one paste) adhesive system:
• The principle of inhomogeneous polymerization was
introduced in orthodontics with the development of
the no mix bonding resins, which were intended to
minimize the mixing induced defects and to reduce
the steps required for placement of the material.

57. Light cured bonding system
• Two types;
1) U.V light activated system
2) visible – light activated systems
• The first light activated bonding systems used U.V
light for initiating the polymerization process .
• The limitations were;
– Limited depth of penetration and thus limited bond
strength.
– The visible light activated systems were developed later
and have totally replaced the U.V light system.

58. • Light curable composite resins are supplied as single paste
which contains;
1)photo initiator : comphoro quinone 0.25 wf%
2)amine accelerator : diethy-amine ethylmethacrylate.

59. Dual-cured system
• The dual cure approach combines the advantages of
rapid initiation for photopolymerisation resins and
high conversion rates for chemically cured resins in
the bulk material.
• In these systems, activations of polymerisation is
induced through surface exposure of the material to
a visible light, and polymerization in the bulk
material occurs by chemical curing process.
• It has improved surface and bulk material properties.

60. • The dual cured adhesive was found to provide
significantly higher bond strength compared to
chemically cured and light cured materials 24 hours
following activation.
• Disadvantages:
– Time consuming process
– Mixing may introduce bulk defects thus increases
porosity.

61. Heat activated (thermocured)systems
• Systems of this type have been introduced for
indirect orthodontic bonding and restorations.
• These adhesives have increased polymerization rates
and superior properties.
• However their use is currently limited because of the
increased temperature is required to initiate
polymerization.

62. LIGHT POLYMERIZATION UNITS
• Modern light sources are hand held devices
that contain the light source and are equipped
with a relatively short - rigid light guide made
up of light fibers.
• The light source is usually a tungsten halogen
light bulb. White light generated by the bulb
passes through a filter that removes the infra-
red and visible light spectrum greater than
500 nm.

63. • 4 types of lamps:
In order of lowest to highest intensity
– LED lamps
– QTH lamps
– PAC lamps
– Argon laser lamps

64. Quartz-Tungsten-Halogen
• Most widely used dental curing light.
• Consists of a quartz bulb with a tungsten filament
in a halogen environment.
• Electric current passes through an extremely thin
tungsten filament which produces Electro
Magnetic radiation in the form of visible light.
• Selective filters – blue light ( 400-500 micron)
– 40 seconds per bracket
– 15 minutes – both arches

65. light pipe
shield to prevent operator from directly
viewing light tip path
light bulb and reflector
light socket
cooling fan ( behind socket), trigger, circu
board, and
wired connection to power supply

66. • Advantages:
– Economical.
– Filters used to dissipate heat to the oral structures
& provide restriction of visible light to narrower
spectrum of initiators.
• Disadvantages:
– Diminished light intensity over a period of time
causes degradation of halogen bulb & degradation
of reflector.
– Shorter life about 100 hrs.
– High temperature production.
– Bond strength decreases with increase in distance.

67. Plasma-Arc (PAC)
Two tungsten electrodes
– small gap
Pressurized chamber
– xenon gas
High-voltage spark
– ionizes gas
– plasma
High voltage is generated between two tungsten
electrodes creating a spark that ionizes Xenon
creating a conductive gas known as Plasma.

68. Advantages:
– High irradiance up to 2400 mW/cm2
– claim 1-3 sec cure.
– Power density of 600-2050 mW/cm2
Disadvantages:
– Expensive.
– High temperature development.
– Heavy so not portable.
– Requires an in built filter to produce narrow
continuous spectrum.

69. Argon Laser
Laser photons travel in phase (coherent) & are collimeated
such that they travel in same direction.
High energy
– coherent, non-divergent
– non-continuous
Highest intensity
Emits single wavelength of 490nm.
Very expensive
Curing time
– 3 secs – per bracket
– 1 min – both arches

70. Advantages:
– Produces narrow focused non divergent monochromatic
light of 490nm.
– Less power utilized.
– Thoroughness and depth of cure is greater.
– Laser curing bond strength did not decrease with
increasing distance.
Disadvantages:
– Risk of other tissues being irradiated.
– Ophthalmic damage of operator and patient.
– Large in size and heavy.
– expensive

71. Light-Emitting Diodes (LED)
Combination of two semiconductors - n doped & p
doped.
• n doped have excess of e- & p doped have holes.
• When both types are combined & voltage is applied
e- & holes connect resulting in emission of light of
characteristic wavelength.

72. Advantages:
– Long service life of more than 10,000hrs.
– Low temperature development.
– No filter system.
– Low power consumption.
– Wavelength of 400-490nm.
Disadvantages:
– Photoinitiator is only CQ.
– Requires longer exposure time to adequately
polymerize microfills & hybrid resin.

73. Alternative polymerization technique:
Dual cure method:
In this method , both the light cure & self cure resins
are used .
The self curing rate is slow and is designed to cure
only those areas of the preparation not adequately
light cured.
Soft start:
Curing begins with the low intensity which allows for
a slow initial rate of polymerization and a high initial
level of stress relaxation during early stages and ends
with a maximum intensity.

74. Precautions for using Curing Lamps
Do not look directly at light
Protection recommended
– glasses
– shields

75. BONDING
• Bonding is a term conventionally used to
describe the attachment of the bracket using
bonding resins to the enamel surfaces.
• The adhesion of orthodontic attachments to
enamel can be classified into direct and
indirect techniques based on the method of
placement.

76. • The steps of direct or indirect bracket bonding
on facial or lingual surfaces of teeth are as
follows:
1. Cleaning
2. Enamel conditioning
3. Sealing and priming
4. Bonding

77. 1. Cleaning :
–Teeth are cleaned with slurry pumice, which
will remove plaque and the organic pellicle
that normally covers all teeth.
–This requires rotary instruments, either a
rubber cup or a polishing brush.
–A bristle brush cleans more effectively, but
care must be taken to avoid traumatizing
the gingival margin.

78. 2. Enamel Conditioning:
–Moisture control
–Enamel pretreatment
• Conventional acid etching
• Sand blasting
• Laser etching

79. • Moisture control:
– Lip expanders and cheek retractors
– Saliva ejectors
– Tongue guards with bite block
– Salivary duct obstructors
– Cotton or gauze rolls

80. • Enamel pretreatment:
– Necessary to make successful bonds.
– Most commonly used etchant is 37%
orthophosphoric acid for 15-30 seconds.
– After etching, the etchant is rinsed off the teeth
with abundant water spray.
– The teeth are thoroughly dried with a moisture
and oil free air source to obtain a well known dull,
frosty white appearance.

81. Commonly asked
• Should the etch cover the entire facial enamel or only a small portion
outside the bracket pad ?
• Are gels preferable to solutions ?
• What is the optimal etching time ? is it different for young and old teeth ?
• Is sandblasting as effective as acid etching ?
• What is the preferred procedure for deciduous teeth ?
• Is prolonged etching necessary when teeth are pretreated with fluoride?
• Will incorporation of fluorides in the etching solution increase the
resistance of enamel to caries attack ?
• How much enamel is removed by etching and how deep are the histologic
alterations ? Are they reversible ? Is etching harmful ?
• Should other means than acid etching (e.g : crystal growth) be preferred?

82. 3. Sealing and Priming:
– A thin layer of bonding agent may be painted over
the etched enamel surface.
– Thinned by a gentle air burst for 1-2 seconds
– The layer may be precured in hard-to-reach areas
where moisture contamination is likely.

83. 4. Bonding:
The recommended bracket bonding procedure
consists of the following steps:
i. Transfer
ii. Positioning
iii. Fitting
iv. Removal of excess
v. Curing

84. i. Transfer:
– Grip the bracket with reverse action tweezers
and then apply the adhesive to the back of the
bonding base.
– Place the bracket close to its correct position.

85. ii. Positioning:
– Use a placement scaler to position the brackets
mesiodistally and incisogingivally and to
angulate them acurately, relative to the long axis
of the tooth.
– Bite should be raised when necessary.

87. iii. Fitting:
– Turn the scaler, with one point contact with the
bracket, firmly push towards the tooth surface.
• Good bond strength
• Little material to remove on debonding
• Optimal adhesive penetration into bracket backing
• Reduced slide

88. iv. Removal of excess:
– Must be removed with scaler before setting, or
burs after setting.

89. v. Curing:
– Cured with light source
– Best initiated after being placed at the correct
position and angulation as close to the bracket
base as possible.
– Metal brackets: through mesial and distal
– Ceramic brackets: through the bracket

90. Bonding to artificial tooth surfaces
• MicroEtcher:
– Uses 50-micron white or 90-micron tan aluminium
oxide particles at approximately 7kg/cm2 pressure
– Advantageous for bonding to different artificial
tooth surfaces.

92. Bonding to Porcelain
• Etchant: 9.6% hydrofluoric acid in gel form
• Time: from 1-2 minutes
• Etched porcelain will have frosted appearance
similar to etched enamel
• Precautions:
– Careful isolation
– Cautious removal of gel with cotton roll
– Rinsing with high-volume suction
• Other methods: APF gel, irradiation with carbon
dioxide or Er:YAG laser

94. Bonding to Amalgam
• Techniques for bonding to amalgam involves;
1) modifications of metal surfaces (sand blasting,
diamond bur roughening)
2) the use of intermediate resins that improve bond
strength
3) new adhesives that bond chemically to non-
precious and precious metals (4 meta resins, 10
bis GMA resins)

96. Bonding to Gold
• Different new techniques, including sand
blasting, electrolytic tin plating or plating with
gallium – tin solution, use of primers and new
adhesives that bond chemically to precious
metals all have been reported to improve
bonding to gold in laboratory settings.

97. Bonding to Composite Restorations
• The bond strength obtained with the addition of
new composite to mature composite is
substantially less than the cohesive strength of
the material.
• However, brackets bonded to a fresh, roughened
surface of old composite restorations appear to
be clinically successful in most instances.
• It is probably advantageous to use an
intermediate primer as well.

98. Indirect Bonding
• Several techniques available.
• Most are based on the procedures described
by Silverman and Cohen.
• In these techniques the brackets are attached
to the teeth on patients models, transferred to
the mouth with some sort of tray into which
the brackets become incorporated, and then
bonded simultaneously.

99. • Current technique based on modification
introduced by Thomas.
• Attach brackets with composite resins to form
a custom base.
• A transfer tray of silicone putty or
thermoplastic material is used, and custom
bracket bases are then bonded to the teeth
with a chemically cures sealant.

100. • Advantages:
– Brackets can be more accurately positioned.
– Clinical chair time is reduced.
• Disadvantages:
– Technique sensitive
– Difficult excess removal
– Risk for adhesive deficiencies
– Risk for adhesive leakage

101. Procedure
1. Take an impression, and pour a stone model.
2. Select brackets for each tooth.
3. Isolate the stone model with a separating
medium.
4. Attach the brackets to the teeth on the model
with light-cured or thermally cured composite
resin, or use adhesive precoated brackets.
5. Check all measurements and alignments.
Reposition if needed.

102. 6. Make a transfer tray for brackets. The material
can be putty silicone, thermoplastics, or similar.
7. After removing the transfer trays, gently
sandblast the adhesive bases with a
microetching unit, taking care not to abrade the
resin base.
8. Apply acetone to the bases to dissolve the
remaining separating medium.
9. Prepare the patient’s teeth for a direct
application.

103. 10. Apply the adhesive on the bonding base.
11. Seat the tray on the prepared arch, and apply
equal pressure to the occlusal, labial, and buccal
surfaces with the fingers. Hold for a minimum of
30 seconds, and allow for 2 minutes or more of
curing time before removing the tray.
12. Remove excess flash from gingival and contact
areas of the teeth with a scaler or contra-angle
hand piece and tungsten carbide bur.

105. References:
• Orthodontics current principles & techniques:
Graber & Vanarsdall, 3rd , 4th and 6th Ed
• Philip’s science of dental materials 11th Ed
• Contemporary orthodontics: Proffit 5th Ed
• Orthodontic Materials Scientific & Clinical
Aspects: William A. Brantley, Theodore Eliades
• Textbook of Orthodontics: Samir E. Bishara
• Orthodontics- Diagnosis and Management of
malocclusion and dentofacial deformity:
O.P.Kharbanda