5. 169 5
• Removal of adhesive residue
• Operator safety
• Prevention and reversal of decalcification
• Conclusion
• References
6. Contemporary Orthodontics 6th ed – William R. Proffit
IINTRODUCTION
“Bonding is mechanical locking of an adhesive to
irregularities in the enamel surface of the tooth and to mechanical
locks formed in the baseof orthodontic attachment.”
Successful bonding depends on three components
•Tooth surface & itspreparation
•Design of attachmentbase
•Bonding Material
169 6
7. Both physical and chemical forces play arole in the
process; however, the mechanicalinterlockingof the low
viscosity polymer bonding agent and the enamel surface isthe
principal mechanism of attachment between the enamel and
resin-bonding systems.
Textbook of Orthodontics – Samir EBishara
169 7
8. •In 1995 BUNOCORE introduced acid etching technique. He
demonstrated increased adhesion produced by acid pretreatment
of enamel. This led to dramatic changes in practice of orthodontics .
• 1965-with the advent of epoxy resin bonding NEWMAN began
to apply these findingsto direct bonding of orthodontic
attachments.
• In early 1970s considerable number of preliminary reports were
published on different commercially available direct & indirect
bonding system.
169 8
9. •A survey conducted by LEONARD GOERLICK in 1979 JCO
revealed almost 93% of orthodontists started bonding
brackets (at least in anteriors )instead ofbanding.
169 9
10. Dentofacial Orthop 2015;147:S56-63)
• In the mid-1960s, Dr George Newman, an
Professor Fujio Miura, chair of
orthodontist in Orange, New Jersey, and
the
Department of Orthodontics at Tokyo Medical
and Dental University in Japan, pioneered the
bonding of orthodontic brackets toenamel.
Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
EVOLUTIONOFBONDING
169 10
11. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod DentofacialOrthop
2015;147:S56-63)
• In the early 1970s, Miura developed a technique for
bonding polycarbonate plastic brackets to phosphoric acid
etched enamel using a restorative filling material
developed by Masuhura etal
• The adhesive, Orthomite (Rocky Mountain Orthodontics,
Denver, Colo), consisted of methyl methacrylate and
polymethyl methacrylate with tri-n-butylborane as the
catalyst
• Miura found that the bond strength decreased with time
asaresult of exposure to oralfluids.
169 11
12. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod DentofacialOrthop
2015;147:S56-63)
• Newman continued his work with epoxy resins, while
Retief et al from South Africa developed an adhesive to
bond metal brackets, based on research conducted by
Bowen on epoxyresins.
• Epoxyresins
did not experience significant polymerization shrinkage
when setting,
had the samecoefficient of thermal expansion asenamel,
and were cross-linked to minimize waterabsorption.
169 12
13. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod DentofacialOrthop
2015;147:S56-63)
• Retief et al partnered with 3M Unitek (Monrovia, Calif)
to develop a mesh grid welded onto flattened stainless
steel band material with ametal bracket welded to it
• Theprimary drawback -the weld spots on the mesh
baseprevented the adhesive from flowing between the
mesh and the foil pad properly- resulting in reduced
mechanical retention
169 13
14. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod DentofacialOrthop
2015;147:S56-63)
• In the early 1970s,3M Unitek's Concise andAdaptic from
Johnson&Johnson (NewBrunswick, NJ) were popular
composite restorative filling materials, formulated from the
research conducted previously byBowen.
• Both systems used a 2-paste bisphenol
methacrylate (BisGMa) resin with quartz as
A glycidyl
a filler and
amineperoxide as the catalyst. These systems were cross-
linked adhesives that experienced minimal polymerization
shrinkage.
169 14
15. • At this time, metal brackets were
welded to aperforatedbase
• The only complaint with
perforated base brackets was that
the adhesive covering the base
through the perforations was
affected by the oral environment
so that it often became stained
and discolored during routine
orthodontic treatment.
Fig1. Perforated metal bracketbase.
169 15
16. • In 1974, Dentsply/Caulk (Milford, Del) introduced the first
single-paste ultraviolet (UV) light curable bracket adhesive,
Nuva Tach; this system used a UV unfilled bonding resin
(Nuva Seal) on the enamel and a single UV curable paste
(Nuva Tach).
• Polymerized with light-emittingenergy in the 280-nm range
• The use of these UV light cured systems was cut short when it
was discovered that they were harmful to exposed skin and
eyes, sometimes even resulting in burned softtissues.
Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod Dentofacial Orthop
2015;147:S56-63)
169 16
17. • In the early 1980s, McNamara and Howe introduced
a version of the Herbst appliance, the acrylic splint
design, that was made from 3-mm-thick splint Biocryl
(Great LakesOrthodontic Products, Tonawanda,NY)
• Soon thereafter, the acrylic splint expander was
developed as a mixed-dentition appliance for the
treatment of maxillary constriction and Class III
malocclusion.
169 17
18. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
• Both appliances necessitated the bonding of splint Biocryl to the
maxilla, a procedure that required a strong, thin paste that
adhered well to plastic and resisted washout from under the
appliance. Excel was developed in 1983 by Reliance Orthodontic
Products(Itasca, Ill) specifically for bonding large acrylic
appliances.
• Excel allowed appliances to be bonded and removed successfully
without decalcification occurring duringtreatment.
169 18
19. •In 1979, Ormco (Orange, Calif)
developed and patented a
technique to braze mesh to a metal
foil pad, eliminating strength-
reducing weld spots
•This design allowed the adhesive to
penetrate between
the mesh and the foil
increasing mechanical
retention
pad, thus
Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
169 19
20. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
• In the early 1980s, visible light–cured restorative
materials were introduced in all areasofdentistry
• The catalyst for these adhesives was
camphorquinone, which cured in the visible light
range (440-480 nm) with a quartz-tungsten-
halogen light, making them safe for exposed eyes
and skin.
169 20
21. • In 1985, Suhproduced Enhance for Reliance
Orthodontic Products, which made bonding to
fluorosed and atypical surfaces possible with any
chemical or light-curingsystem.
• Enhancewas applied on the etched enamel before
the unfilled resin. In addition, the monomer in
Enhance (biphenyl dimethacrylate) bonded
chemically tocomposite and metal.
Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod Dentofacial Orthop
2015;147:S56-63)
169 21
22. • Crypsis, a color-change adhesive, was introduced in
1986.
• This 2-paste dual-cure bracket adhesive was
developed and marketed by Orec (Beaverton, Ore)
• The 2-paste material was yellow after it was mixed
but it turned tooth colorwhen itpolymerized.
• This color characteristic allowed the operator to see
the composite flash around the bracket base and
remove it before itpolymerized.169 22
23. • In 1995, Silverman et al developed a technique for
bonding metal brackets to wet enamel with no acid
etching using Fuji Ortho LC (GC America, Alsip, Ill), a
dual-cure glassionomer cement.
• This 2-part system comprises a powder
(fluoroaluminosilicate glass) and a liquid (polyacrylic
acid, water, hydroxyethyl methacrylate[HEMA], and
camphorquinone-light activator).
169 23
24. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
• In 1996, 3M Unitek introduced a metal bracket
system with a light-cured adhesive preapplied to
the base. The operator simply etched the enamel
surface, applied an unfilled resin to the enamel,
and placed the bracket.
• The prepasting by the bracket manufacturer
eliminated the need for an assistant to place the
composite on the bracketbase.
169 24
25. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
• In 1998,
introduced.
several hydrophilic primers were
• Ortho Solo (Ormco), Assure (Reliance
Orthodontic Products), and MIP (3MUnitek) were
hydrophilic bonding resins that bonded well to
wet or dry enamel,making the bonding procedure
more forgiving.
169 25
26. • Microetching (sandblasting) became the mechanical
preparation of choice in the dental restorative field in the
early 1990s.
• Aluminum oxide, the preferred abrasive powder for intraoral
microetching, created fine surface roughness and significantly
increased the mechanical retention toartificial surfaces
169 26
27. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
• In 2000, self-etching primers became effective in
conditioning dentin andenamel.
• Self-etching primers such as Transbond Plus (3M
Unitek) and SEP (Reliance Orthodontic Products)
now are part of the orthodontic armamentarium
because of their lack of rinsing and drying steps,
steps that are necessary with traditional
phosphoric acid etching.
169 27
28. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
• In 2003, Pro Seal (Reliance Orthodontic
into theProducts) was introduced
marketplace as
releasing filled sealant that would
a light-cured, fluoride-
remain
intact on the exposedenamel for 2 to 3 years
even under toothbrushing conditions
169 28
29. Theevolution of bonding in orthodontics ,PaulGange- Am JOrthod
Dentofacial Orthop 2015;147:S56-63)
• In 2005, LED Pro Seal (Reliance Orthodontic
Products) was introduced to accommodate
the clinician using the new, cordless light-
emitting diode lights that emitted a photon
between 440 and 480nm.
169 29
30. BONDINGOVERBANDING
1. Esthetically superior.
2. Faster & Simpler.
3. Lessdiscomfort for the patient
4. Arch length is not increased bandmaterial.
5. Allows more precise bracket placement even in tooth
with aberrantshape.
6. Improved gingival health.
7. Better accessfor cleaning.
169 30
31. 8.Mesiodistal enamel reduction possible during treatment.
9.Interproximal areasare accessible for compositebuildup.
10.Cariesrisk under loose bands is eliminated. Interproximal caries
canbe deducted & treated.
11. No band spacesto close at end oftreatment.
12. Brackets can be recycled further reducing thecost.
13.Invisible lingual brackets can be used when esthetic is
important.
14. Attachments canbe bonded to fixedbridgeworks.
169 31
32. MECHANISM OF
BONDING
1. Chemical - based on primary forces
– covalent, ionic, metallic bonds.
2. Mechanical -based on penetration of one
material into another at microscopic
level (when surfaces are rough)-
formation of resin tags.
169 32
34. PRE-TREATMENT
Pre-treatment is necessary asmouth is complicated
by saliva ,acquired pellicle , different organic and
inorganic components of enamel anddentin.
• Cleansing
– Improves wetting
• Acid etching
– Improves adhesion micromechanical retention.
169 34
35. CLEANING
169 35
• An ideal bonding surface should be free of any debris, and cleaning
of the teeth with pumice will remove plaque and the organic pellicle
that normally covers all teeth.
• The need for conventional pumice polishing before acid etching has
been questioned, since neither bond strength nor enamel surface
etch pattern is altered by pumicing clean enamel.
• However, pumice prophylaxis does not appear to affect the bonding
procedure adversely, and cleaning the tooth may be advisable to
removing plaque and debris that otherwise might remain trapped at
the enamel–resin interface, particularly when bonding posterior
teeth that are sometimes out of reach of efficient brushing activity.
37. ENAMEL CONDITIONING
169 37
Moisture control: Salivary control and maintenance of a dry
working field are essential after rinsing and drying. Many
devices on the market accomplish this:
• Lip expanders and cheek retractors
• Saliva ejectors
• Tongue guards with bite blocks
• Salivary duct obstructors
• Gadgets that combine several of these devices
• Cotton or gauze rolls.
Present research indicates that antisialagogue agents do not
present a statistically significant effect on the observed bond
failure rates and generally are not needed for most patients.
39. 169 39
ENAMEL PRE-TREATMENT
Conventional Acid Etching:
• Isolation of the operative field is followed by etching of the
enamel surface. An untouched enamel surface is
hydrophobic, and wetting is limited, which makes bonding
to an intimate enamel surface a challenging procedure.
• An enamel pretreatment or surface conditioning is
necessary to make successful bonds. This pretreatment is
usually accomplished by etching the surface using various
acids.
• The most commonly used etchant is 37% orthophosphoric
acid for 15 to 30 seconds.
40. 169 40
• At the end of the etching phase, the etchant is rinsed off the
teeth with abundant water spray.
• A high-speed evacuator is strongly recommended for
increased efficiency in collecting the etchant-water rinse and
to reduce moisture contamination on the teeth (Patterson
Dental, St. Paul, MN).
• Salivary contamination of the etched surface should best be
avoided. (If contamination occurs, then rinsing with the water
spray or re-etching for a few seconds is recommended; the
patient must not rinse.)
• Since blood contamination has been shown to decrease the
shear bond strength (SBS), teeth that are contaminated with
blood should be re rinsed and dried.
41. 169 41
• Next, the teeth are thoroughly dried with a moisture and oil
free air source to obtain the well-known dull, frosty
appearance.
• Teeth that do not appear dull and frosty white should be re-
etched.
• Although considerable discussion of several aspects of
enamel pretreatment remains, most of the debate
concerning acid etching appears to be of limited clinical
significance, because, apparently, good bond strength
significantly depends more on both avoiding moisture
contamination and achieving undisturbed setting of the
bonding adhesive than on variations in the etching
procedures.
44. MORPHOLOGY OF
ENAMEL
Longitudinal section under microscope
• Enamel prisms (rods) – 5-12 million
• Diameter:4-5 µm
• Thickness : 1000 to 2000 µm (except asittapers
toward the cervical margin)[Diedrich,1981]
• Extend from DEJto outersurface
• Wider – Prism head
• Narrower – Prism tail 44
169 44
45. •Enamelis made up of aseriesof closely packed hexagonal'prisms' ofhydroxyapatite.
•Thecircular or hexagonal features on the surface of enamel shown here represent
the ends of these hydroxyapatite crystals. ('keyhole' or 'fishscale' appearance ).
45
169 45
46. PATTERNS OF ETCHING:
TYPE1- INTRAPRISMATIC –
REMOVAL OF PRISM CORES
HONEYCOMB
Type 1 –Most common.
Preferential removal of enamel prism cores &periphery
intact.
46
169 46
47. TYPE2 – INTERPRISMATIC– REMOVAL OF
PRISM PERIPHERIES
COBBLESTONE
Type 2 - Reverseof type 1.
Periphery removed and coresintact.169 47
48. TYPE3 – BOTHTYPE1 &2
Type 3 –Etching pattern lessdistinct.
Both types 1 & 2present.169 48
49. WHAT ISTHE OPTIMALETCHINGTIME?
• No differences in bond strength are detected between 15 second
and 60 second etching with 37%phosphoric acid; however, shorter
etching times causeless enamel damage on debonding.
• Acording to William A. Brantley decreasing etching time between 30
and10 seconds does not affect bond strength, whereas etching for
0 or 5seconds reduces bond strength ( less than 3 MPa)
significantly.
• Scanning electron microscopy shows that etching with 37%
phosphoric acid
for at least 30 seconds produces more optical etching patterns than
etching for 15seconds.169 49
50. Concentration of Acid ?
• Etching with 10% or 37% phosphoric acid produces the highest bond
strengths (28 MPa ) to enamel. No differences in bond strengths are
observed when enamel is etched with phosphoric acid ranging in
concentration from 2% to 37%. One study reported that 2%
phosphoric acid etchant was adequate for bonding, whereas another
recommended 10 – 37% phosphoric acid. (William A. Brantley )
• Wolfgang Carstensen (AJO 1995). Compared three acid
concentration (37%, 2% and 5%) was used for 30 seconds to bond
the brackets. The results showed that 37% phosphoric acid had a
higher bond strength.
The amount of adhesive left on the teeth after debonding was
smaller for 2% acid than 37% and 5%, and it was concluded that 2%
phosphoric acid solution is appropriate for bonding of brackets and
the reduced etching could be favorable in preventing enamel
damage during the treatment and at the time of debonding.169 50
51. • Wasundhara(AJO) made an invitro study to detect the etch pattern
and compare the shear bond strength by using 37% and 5%
phosphoric acid and it was observed that there was no significant
difference in shear bond strength, but 5% phosphoric acid produced
a minimal enamel loss.
What is preferred procedure for deciduous teeth?
• Acording to Zachrisson recommended procedure for conditioning
deciduous teeth is to sand blast with 50 μm aluminum oxide for 3
seconds to remove some outermost aprismatic enamel and then
etch for 30 seconds with Ultra-Etch 35% phosphoric acid gel.
169 51
52. • Is prolonged etching necessary when teeth are pretreated with
fluoride?
M. Brannstrom et al(1982 AJO) suggested that extra
etching time is not necessary when teeth have been pretreated
with fluoride. When in doubt, check that the enamel looks
uniformly dull and frosty white after etch. If it does, surface
retention is adequate for bonding.
• Will incorporation of fluorides in the etching solution will
decreasethe bond strength?
Fluoridated phosphoric acid solutions and gels provide an
etchingeffect similar to nonflouridated ones and give
adequate bond strength in direct bondingprocedures.169
52
53. • F.Garcia et al (AJO 1991) compared the enamel morphology
and shear bond strength of orthodontic bonded to enamel
etched with fluoridated or a non fluoridated phosphoric acid
gel. The result showed that overall morphologic etching effect
wassimilar in both groups.
• J .B Thornton et al found that addition of fluoride to the
phosphoric acid solution reduce the decalcification adjacent to
bonded brackets.
169 53
54. • How much enamel is removed by etching and how deep are the
histologicalalterations?
• A routine etching removes 3 to 10 μm ofsurface enamel. Another 25
microns reveal subtle histologic alterations, creating the necessary
mechanical interlocks.
• Deeper localized dissolutions generally cause penetration to a depth
of approximately 100 microns or more.
• Although laboratory studies indicate that the enamel alterations are
largely (although not completely) reversible,the overall effect of
applying an etchant to healthy enamel is not detrimental.
• This point is augmented by the fact that normal enamel is from 1000
to 2000 microns thick, except where it tapers toward the cervical
margin.
• Abrasive wear of facial enamel is normal and proceeds at a rate of up
to 2 mm per year, and facial surfaces are self-cleaning and not prone
to caries.
169 54
55. 169 55
Can recently bleached teeth be safely bonded?
• Today, bleaching is an increasing trend, and current
information is conflicting, with some research indicating no
adverse effect, whereas other studies indicate that
bleaching with 35% hydrogen peroxide significantly
reduces bracket adhesion when bonded 24 hours after
bleaching.
• However, no significant adverse effect of bleaching seems
to occur after 7 days.
• Therefore postponing the bonding procedure
approximately 1 to 4 weeks for recently bleached teeth
may be a good practice.
56. 169 56
Should the etching cover the entire facial enamel
or only
a small portion outside the bracket pad?
• Although laboratory research indicates increased
susceptibility for WSLs by surplus orthodontic etching
exceeding the bracket base area , clinical experience over
more than 25 years indicates that etching the entire facial
enamel with solution is harmless—at least when a fluoride
mouth rinse is regularly used.
57. ALTERNATIVE TO ACID
ETCHING
• Crystal Growth.
• Laser.
• Air Abrasion / SandBlasting.
• Other acids like polyacrylic acid and
maleic acid.
169 57
58. • Also called asCrystal bonding.
• Polyacrylic acid containing sulfate ions
applied.
• Reactswith the calcium in the enamel
forming CaSO4 Dihydrate
–chemical bond with
surface
(Gypsum)
enamel.
• Crystal enucleation site for mechanical bond with adhesives.
Needle-shaped crystals
CRYSTAL GROWTH TECHNIQUE (SMITH &
CARTZ,1973)
169 58
59. Advantages :
• Easier debonding, lessadhesive left on tooth and lessdamage
to enamel.
• Minimal effect on theouter, fluoride-containing enamel
surface.
• Less residual adhesive left behind in theenamel surface.
Disadvantages :
• Bond strength 60-80%of strength obtained withacid etching.
• 64.4%bond failure compared to 3.4%ofconventional.
(Mac phee etal 1985).
169 59
61. 169 61
• Some manufacturers of commercial units have suggested
that air abrasion could eliminate acid etching.
• However, bond strengths to air abraded enamel are only
about 50% of those to acid etched enamel.
• Air abrasion or micro-etching of metal brackets or bands is
an effective technique for improving bond strength to these
air abraded substrates.
• Air abrasion could be an alternative to pumicing the teeth
before etching.
62. 169 62
LASER ETCHING
• Laser treatment of dental enamel causes thermally induced
changes within the enamel to a depth of 10 to 20 μm,
depending on the type of laser and the energy applied to the
enamel surface.
• In effect, etching takes place through a process of
continuous vaporization and microexplosions due to
vaporization of water trapped within the hydroxyapatite
matrix.
• The degree of surface roughening is dependent on the
system used and the wavelength of the laser
63. • commonlyusedLasers:
o Neodymium-yttrium-
aluminum garnet (Nd:YAG)
o CO2
o Er:YAGlasers.
169 63
The surface produced by laser etching is also claimed to be
acid resistant as a result of the modified calcium-to
phosphorus (Ca/P) 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.
64. 169 64
• Laser etching of enamel by a ND:YAG laser typically
produces lower bond strength than does the acid etching.
• Satisfactory in vitro bond strength were obtained in one
study only when ND:YAG laser was used for 12 seconds at
maximum power (3W).
• Studies of CO2 laser etching of enamel have shown that
the bond strengths of 10 Mpa can be obtained reliably.
65. 169 65
• The use of polyacrylic acid with residual sulfate is reported to
provide retention areas in enamel similar to those after
phosphoric acid etching with less risk of enamel damage at
debonding. However, other researchers have found much
weaker bonds.
• Research shows that 10% maleic acid, which is believed to
decrease mineral loss alone, may produce similar bond
strengths to 37% phosphoric acid.
• However, the use of these milder acids has never been
popularized.
OTHER ACIDS
66. SEALINGANDPRIMING
169 66
• Much confusion and uncertainty surround the use of
sealants and primers in orthodontic bonding.
• Recent findings demonstrate that bonding with or without a
primer (unfilled resin) before bracket placement is equally
clinically successful as far as bracket failure rate is
concerned.
Why, then, should a sealant be of any value in bracket
bonding?
• If nothing else, a sealant permits a relaxation of moisture
control because controlling moisture is no longer critical
after resin coating.
• Sealants also provide cover for enamel in areas of
adhesive voids, which is probably especially valuable with
indirect bonding.
67. 169
67
• After the teeth are completely dry and frosty white, a thin layer
of bonding agent (sealant, primer) may be painted over the
etched enamel surface.
• The coating may be thinned by a gentle air burst for 1 to 2
seconds.
• A thick layer may cause drifting before curing is initiated and
may interfere with the precise adaptation of the bracket base.
Bracket placement should be immediately started after all of the
etched surfaces are coated.
• Separate curing of the bonding agent is not necessary when
light cured products are used.
• Reapplication of the sealed layer is not required when saliva
contamination occurs, but the area should be air dried before
bracket placement.
68. USEOF SEALANT LED TO MANY DIVERGENT
CONCLUSIONS.
1. They might be necessary to achieve proper bond
strength.
2. Its necessary to improve resistance to microleakage.
3. After sealant coating moisture control may not be
extremely important.
4. It provides enamel cover in areasofadhesive voids.
169 68
69. 5.Sealant might permit easier bracket removal &
protect against enamel tear outs during debonding. (
Zachrisson BUet al 1995 JCO)
6.Study by Leonardo Foresti et al Angle 1994 showed
sealant actually increases no., & length of resin tags.
Also more fluid resin coupled with previously applied
sealant penetrates deeper into enamel & forms longer
tags.
169 69
72. • A self etching self adhering flowable composite
technology eliminates the need for separate bonding
application step with composites for direct
restorative procedures.
• Stable nanofiller that will not settle out of dispersion.
• Highly functionlised SiO2
• Nano Particle - <20nm
• Bond Strength – 30Mpa
• Curing time – 35 sec
• Vertise flow (Kerr), Single Bond, Optic Bond Solo
Plus,Adper Single Bond 2 adhesive, Futurabond DC,
Voco,Germany 3M
169 72
VIII - GENERATION
73. MOISTURE INSENSITIVE PRIMERS (MIP)
169 73
• In an attempt to reduce the bond failure rates under moisture
contamination, hydrophilic primers that can bond in wet
fields have been introduced as a potential solution.
• Commercially available as: Transbond MIP, 3M Unitek,
Monrovia, CA; Assure or Assure Plus, Reliance
OrthodonticProducts.
• Laboratory studies have demonstrated that water and saliva
contamination of enamel during the bonding procedure
lowers bond strength values of composite resins.
• When bonding to enamel, the resin sealant or resin primer
must be placed onto the prepared enamel before the pellicle
(biofilm) formation from the saliva, which is not particularly
difficult but is crucial to a successful enamel bond.
74. 169 74
• The main reactive component of the this
product is a Methacrylate-functionalized
polyalkeonic acid copolymer.
• Excessive interfacial water ionizes carboxylic
groups, forming hydrogen bonded dimers.
Moreover, a reversible breaking and reforming
of calcium-polyalkeonic acid complexes with
enamel is established, providing some stress
relaxation capacity.
• In this manner, a dynamic equilibrium occurs at
the interface, incorporating water in the
bonding mechanism, thus minimizing the
detrimental plasticizing effect of water that
occurs with moisture contamination of
conventional bonding agents.
75. 169 75
Self-Etching Primers.
• Despite being demonstrated to provide only modest time saving
(8 minutes for full mouth bonding),the use of self-etch primers has
steadily increased because of their great simplicity.
• The unique characteristic of these bonding systems is that they
combine the conditioning and priming agents into a single acidic
primer solution for simultaneous use on both enamel and dentin;
therefore separate acid etching of the enamel and subsequent
rinsing with water and air spray is not required.
• The active ingredient of the SEPs is a methacrylate 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 penetration is
identical.
76. 169 76
Three mechanisms act to stop the etching process.
• First, the acid groups attached to the monomer are neutralized
by forming a complex with calcium from hydroxyapatite.
• Second, as the solvent is driven from the primer during the
airburst step, the viscosity rises, slowing the transport of acid
groups to the enamel interface.
• Finally, as the primer is light cured and the primer monomers
are polymerized, transport of the acid groups to the interface is
stopped.
• Scanning electron microscopy (SEM) examination of the
impression of SEP-treated enamel shows different surface
characteristics from acid-etched enamel.
• Instead of the well-known distinct honeycombed structure with
microtag and macrotag formation , 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.
77. 169 77
• Clinical bond strengths using SEPs may appear to be lower
than those with conventional etching and priming.(Ireland AJ,
Knight H, Sheriff M. AJODO 2003).
• Another recent systematic review and meta analysis
concludes that only weak insignificant evidence suggests
higher odds of failure with an SEP than an acid etch over 12
months in orthodontic patients.(Fleming PS, Johal A, Pandis
N. AJODO 2012)
• Previous studies show that the SEP provides no resistance to
enamel demineralization and results in twice as many white
spot lesions (WSLs), especially in patients with poor oral
hygiene.(Tanna N, Kao E, Gladwin M, et al AJODO 2009)
• Recent studies, however, show that the enamel samples that
are conditioned with the fluoride-releasing SEP (Transbond
Plus, 3M Unitek, Monrovia, CA) display better
remineralization.(Visel D, Jäcker T, Jost-Brinkmann PG, et al.
J Orofac Orthop. 2014)
82. Twophase/ Mixed adhesives- (Concise 3m)
Onepaste initiator & activator on theother
• Polymerization initiation
– by mixing of pastes
Start of mix Start of gel Initial set Final set
Working time Gelperiod
Working time- brackets are placed and positioned
Gel period- brackets must not be placed or positioned
Final set- archwires may be placed
CHEMICALCUREADHESIVES
169 82
83. • Polymerization initiation
– Bonding agent on the etched enameland
bracket backing.
– Onepaste under light pressure
• Clinical handling
– Efficient application
– Limited time requirements.
Activator sealant
Adhesive paste
•Enamel and bracket sides of adhesive
are more polymerized relative tomiddle
zones.
ONEPHASE/ NOMIX
[Rely - a– Bond( reliance),Unite (3M)]
169 83
84. LIGHTCUREADHESIVES
• Polymerization initiation by exposure
to light curingsource
• Extended working time (command
setting).
• Useful in situations where quick set
is required- Eg.attachment on
canine
with
after surgical
the risk for
impacted
uncoverig
bleeding.
• Bond strength hasbeen studied extensively and supportstheir
use. (Theodore)169 84
85. 169 85
• For a monomer system in which light cure is used to initiate
polymerization depends on several factors:
a) The exposure time.
b) The photoinitiator concentration.
c) The light intensity emitted by the curing unit at the
peak absorbance wavelength of photoinitiator.
d) The filler volume fraction.
• Light scattering at the surface of filled composite can
reduce the intensity of incident light reaching the bulk
material, resulting in decreased conversion in thick
specimens.
86. 169 86
• Under clinical conditions, increased irradiation time and light
intensity lead to higher strength for photocured composite,
since a structure with higher density of cross links is formed.
• With light curing from edges of brackets, the directions of
free-radical gradient and polymerization shrinkage are
modified from those of chemically cured no-mix materials.
87. 169 87
APPLIED RESEARCH ON LIGHT CURED
ADHESIVES
• A number of studies published during the 1990s have
investigated the bond strength and degree of cure of light-
cured adhesives bonded to transparent ceramic brackets and
metallic brackets.
• The majority of these studies concluded that the bond
strength provided by the light cured material was not different
from that of chemically cured adhesive.
• In a study by Eliades et al the Dc value for a light-cured
adhesive bonded to a metallic bracket and irradiated from
incisal and cervical edges was comparable to DC values for a
chemically cured adhesive and its light cured counter-part
bonded to transparent ceramic brackets.
88. 169 88
• Research has shown that dc of light cured Transbond
XL(3M Unitek) adhesive bonded to polycrystalline alumina
brackets was not significantly different from that of
chemically cured Concise (3M Unitek) adhesive bonded
to same brackets.
• This result is attributed to the thin film nature of adhesive
layer, which has a very high surface-to-volume ratio.
• The dominance of surface properties over the bulk
properties is considered to favor the use of light cured
adhesive resins, because these systems are expected to
possess superior surface curing characteristics.
89. • Polymerization initiation
– Activation of polymerization is induced through
Surface exposure of the material to a source of visible light
and polymerization in the bulk material occurs by chemical
curing process.
• Clinicalhandling
– Combines advantages of both light & chemical cure resins.
– Prolonged clinical application process asboth mixingand
photocuring arerequired.
– Mixing may induce air incorporation leading to porosity inthe
set material.
• Ideal candidates for bonding molartubes.
DUALCUREADHESIVES
169 89
90. • Polymerization initiation
– Through exposure to heat
• Usedfor indirect orthodontic bonding andrestorations.
• Properties
– Superior properties : increased polymerizationrates.
– Useis limited asincreased temperature is required to initiate
polymerization and the necessity for adapting an indirect
bonding set up.
THERMOCURE
169 90
91. 169 91
GLASS IONOMER CEMENTS
• Glass ionomer cements were introduced in 1972, primarily as
luting agents and as a direct restorative material, with unique
properties for chemically bonding to enamel, dentin, and
stainless steel and being able to release fluoride ions for
caries protection.
• The second-generation water-hardening cements contain the
same acids in freeze-dried form or in an alternative powdered
copolymer of acrylic and maleic acids.
• Glass ionomer cements were modified to produce dual-cure
or hybrid Cements. e.g., GC Fuji Ortho LC, GC America,
Alsip, IL).
92. 169 92
• Glass ionomer and light-cured glass ionomer cements are the
material of choice for cementing bands; they are stronger than
zinc phosphate and polycarboxylate cements, with improved
adhesion to enamel and metal and less demineralization at the
end of treatment.
• Glass ionomers are used by only 7% of the clinicians for direct
bonding of brackets.
• The pretreatment with polyacrylic acid facilitates a chemical bond
between the glass ionomer and the enamel and thus should be
performed before bracket bonding with the glass ionomer.
• When bond strength is the primary criterion for selecting an
adhesive, composite resins are recommended.
• Limiting the use of the glass ionomer with at-risk orthodontic
patients is advisable to provide preventive actions and potentially
remineralize early (subclinical) enamel demineralization.
93. 169 93
• Trials with modified glass ionomers for bonding showed that
even when some composite resin was included in the
bonding material, the bond strength still was not adequate.
• Justus and coworkers have advocated a way to improve the
bond strength of a modified glass ionomer to the point that it
should be adequate for bonding.
• The key to bonding with a largely glass ionomer material has
turned out to be deproteinization of the enamel surface with
5% NaOCl (sodium hypochlorite, widely sold as Clorox), and
then a 15- to 20-second etch time—slightly shorter than the
usual 25 to 30 seconds—with 35% H3PO4.
• This increases the percentage of etch patterns 1 and 2 in the
enamel surface and significantly increases the bond
strength of the resin-modified glass ionomer (Fuji Ortho LC).
Contemporary Orthodontics 6th ed – William R. Proffit
95. 169 95
Does this use of resin-modified glass ionomer
cement really reduce the incidence of
demineralization and white spots?
• The ideal evidence would be outcomes from a randomized
clinical trial, which has not been done, but the clinical data
presented by Justus are impressive.
• It appears that the improved fluoride release from the
resin-modified glass ionomer can provide useful protection
against demineralization, and the glass ionomer
component allows the ability to “recharge” the fluoride
content of the resin by in-office fluoride treatment.
97. 169 97
CONVENTIONAL AND FAST HALOGEN LIGHTS
• In light-initiated bonding resins, the curing process begins
when a photoinitiator is activated.
• Most photoinitiator systems use camphoroquinone as the
absorber, with the absorption maximum in the blue region of
the visible light spectrum at a wavelength of 470 nm.
• Until recently, the most common method of delivering blue
light has been halogen-based light-curing units (e.g.,
Ortholux XT, 3M/Unitek).
• The halogen lights can cure orthodontic composite resins in
20 seconds and light-cured resin-modified glass ionomers in
40 seconds per bracket.
98. 169 98
• Various attempts have been made to enhance the speed of
the light-curing process.
• Fast halogens (e.g., Optilux 501 or Demetron, Kerr, Orange,
CA) have significantly higher intensity output than other
current halogen lights, and this is accomplished by using
higher-output lamps or using turbo tips that focus the light
and concentrate it into a smaller area.
• By this means, curing times can be reduced to half of the
time needed with conventional halogen lights.
99. 169 99
Argon lasers
• Argon lasers produce a highly concentrated beam of light
centered around the 480-nm wavelength. In addition, the light
is collimated, which results in more consistent power density
over distance.
• One interesting potential of the argon laser is its ability to
protect the lased enamel surface against decalcification.
• Recent studies have shown that argon laser irradiation
significantly reduces enamel demineralization around
orthodontic brackets.(Anderson AM, Kao E, Gladwin M, et al.
The effects of argon laser irradiation on enamel
decalcification: an in vivo study. Am J Orthod Dentofac
Orthop).
• Although the curing times could be reduced to 5 seconds for
unfilled and 10 seconds for filled resins with argon laser, their
use in orthodontics at present is not extensive, probably
because of their high cost and poor portability.
100. 169 100
PLASMA ARC LIGHTS
• In the mid-1990s, the xenon plasma arc lamp was introduced
for high-intensity curing of composite materials in restorative
dentistry.
• This lamp has a tungsten anode and a cathode in a quartz
tube filled with xenon gas.
• When an electric current is passed through xenon, the gas
becomes ionized and forms a plasma made up of negatively
and positively charged particles and generates an intense
white light.
• Plasma arc lights are contained in base units rather than in
guns because of the high voltage used and heat generated.
The light guide is stiff because of the gel inside.
• The white light is filtered to blue wavelengths, with a narrow
spectrum between 430 and 490 nm.
101. 169 101
• Whereas the conventional halogen lamps emit light with an
energy level of 300 mW, the plasma arc lamp has a much
higher peak energy level of 900 mW.
• The advantage of the high-intensity light is that the amount of
light energy needed for polymerization of the composite resin
can be delivered in a much shorter time.
• Recent clinical studies indicate that exposure times of 3 to 5
seconds for metal brackets and even shorter times for
ceramic brackets yield similar bond failure rates as for
brackets cured with a conventional halogen light for 20
seconds.
102. 169 102
• The heat generated by the highintensity lights and the
possibility of harming the pulp tissue have been addressed
in several publications.
• The increase in pulpal temperature in orthodontic bonding
was significantly higher with conventional halogen than with
LED or plasma arc lights.
• However, orthodontic bonding with light-curing units did not
exceed the critical 5.5°C value for pulpal health.
103. 169 103
LIGHT-EMITTING DIODES
• A solid-state LED technology for the polymerization of light-
activated dental materials was proposed by Mills and
colleagues.
• 50 LEDs use junctions of doped semiconductors to generate
light instead of the hot filaments used in halogen bulbs.
• They have a lifetime of over 20,000 hours and undergo little
degradation of output over this time.
• LEDs do not require filters to produce blue light, are resistant
to shock and vibration, and take little power to operate.
• Earlier LED designs provided unsatisfactory results with
metal brackets, possibly attributable to their low power
output.
• Current LEDs, however, manage to combine high power
output (from 1000 to 3200 mW/cm2) with a very narrow
wavelength range around 465 nm, which very nicely matches
the absorption peak of camphoroquinone
105. DIRECT BONDING
169 105
• At present, the majority of clinicians routinely bond brackets
with the direct rather than the indirect technique.
• According to a 2014 survey in the United States,
approximately 90% of orthodontists routinely use direct
bonding.
• Many different adhesives exist for direct bonding, and new
ones continually appear.
• However, the basic bonding technique is only slightly
modified for varying materials, according to each
manufacturer’s instructions.
• The easiest method of bonding is to add a slight excess of
adhesive to the backing of the attachment and then place
the attachment on the tooth surface in its correct position.
106. 169 106
The recommended bracket bonding procedure (with any
adhesive) consists of the following steps10:
1. Transfer
2. Positioning
3. Fitting
4. Removal of excess
5. Curing
Transfer: The clinician grips the bracket with reverse action
tweezers and then applies the mixed adhesive to the back of
the bonding base. The clinician immediately places the
bracket on the tooth, close to its correct position.
107. 169 107
Positioning: The mandibular molar and premolar bracket
wings must be kept out of occlusion, or the brackets may easily
come loose. Therefore before positioning the brackets, the
operator should do the following:
1. The patient is asked to bite with his or her teeth together; the
operator should then evaluate the tooth area available for
bonding.
2. The mandibular posterior brackets are bonded out-of-
occlusion, which may necessitate adjusting bends in the
archwires.
• Later, the clinician uses a placement scaler to position the
brackets mesiodistally and incisogingivally and to angulate
them accurately, relative to the long axis of the teeth.
• Proper vertical positioning may be enhanced by different
measuring devices or height guides.
• A mouth mirror will aid in horizontal positioning, particularly
on rotated premolars.
108. 169 108
• Fitting: Next, the clinician turns the scaler and, with one-
point contact with the bracket, firmly pushes toward the tooth
surface.
• The tight fit results in good bond strength, little material to
remove on debonding, optimal adhesive penetration into
bracket backing, and reduced slide when excess material
peripherally extrudes.
• The clinician should remove the scaler after the bracket is in
the correct position and should make no attempts to hold the
bracket in place with the instrument.
• Even slight movement may disturb the setting of the
adhesive. A totally undisturbed setting is essential for
achieving adequate bond strength.
109. 169 109
Removal of excess: A slight bit of excess adhesive is
essential to minimize the possibility of voids and to ensure that
the adhesive will be buttered into the bracket backing when the
bracket is being fitted.
• Excess adhesive will not be worn away by tooth brushing
and other mechanical forces; it must be removed (especially
along the gingival margin) with the scaler before the
adhesive has set or with burs after setting
110. 169 110
• The removal of excess adhesive reduces periodontal damage
and the possibility of decalcification.
• Removal of excess adhesive can improve aesthetics, not only
by providing a neat and clean appearance but also by
eliminating exposed adhesive that might become discolored
in the oral environment.
• Some manufacturers add a coloring agent to assist in the
visualization of the excess adhesive (APC II/Plus, 3M Unitek,
Monrovia, CA).
• Another recent advance in this aspect is the introduction of a
flashfree product (APC Flash-Free, 3M Unitek, Monrovia,
CA).
111. 169 111
Curing: Once the bracket is secured in the desired position, the
adhesive layer is cured with the light source. The correct setting
should be preset before the curing.
• The light is best initiated after being placed at the correct position
and angulation as close to the bracket base as possible.
• Divergent photon release will be avoided and curing efficiency
increased if the light guide is brought into contact with the bracket
after an initial cure of 1 to 2 seconds.
• Many manufacturers advise curing metal brackets from mesial
and distal, direct bond molar tubes from mesial and distal or
occlusal, and ceramic brackets through the bracket.
• Most current light sources can cure adhesives in approximately
10 or 5 seconds per metallic and ceramic brackets, respectively.
• A new plasma-emulating LED (VALO Ortho, Ultradent Products,
Inc., South Jordon, UT) was demonstrated to cure resin under
brackets in as few as 3 seconds, which is also confirmed by the
clinical experience.
112. INDIRECT BONDING
• First described by Silverman & Cohen in1972.
• Placing brackets in amodel
• Usetemplate or tray totransfer
• Common agent – “No-mix” chemically activatedmaterials
• More useful in LingualOrthodontics
• Types
– ClearTray
– PVSTransferTray
– Memosil Tray
– SingleUnit TransferTray
169 112
113. 169 113
• Most current indirect bonding techniques are based on a
modification introduced by Thomas,which attaches the
brackets with composite resin to form a custom base.
• A transfer tray of silicone putty or thermoplastic material is
used, and the custom bracket bases are then bonded to the
teeth with a chemically cured sealant.
• Different types of custom base composites may be light
cured, chemically cured, or thermally cured.
• One system (from Reliance Orthodontic Products, Itasca, IL)
recommends the use of a thermally cured base composite
(Therma-Cure), Enhance adhesion booster, and a
chemically cured sealant (Custom I.Q.).
• Another system (from 3M Unitek, Monrovia, CA)
recommends the use of light-cured base composite
(Transbond XT) and chemically cured sealant (Sondhi
Rapid-Set) in the clinic.
114. 169 114
The following procedure may be useful:
1. Take an impression, and pour a stone (not plaster) 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 lightcured
or thermally cured composite resin, or use adhesive precoated
brackets.
5. Check all measurements and alignments. Reposition if
needed.
6. Make a transfer tray for the 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.
115. 169 115
8. Apply acetone to the bases to dissolve the remaining separating
medium.
9. Prepare the patient’s teeth for a direct application.
10. Apply Sondhi Rapid-Set (3M Unitek, Monrovia, CA) resin A to the
tooth surfaces and resin B to the bracket bases.
• If Custom I.Q. (Reliance Orthodontic Products, Itasca, IL) is used,
then apply resin B to the teeth and resin A to the bases.
• Alternatively, apply a thin coat of the mixture of part A and part B
adhesive to each custom resin base in the indirect bonding tray
and to the tooth surface if using Transbond IDB Pre-Mix Chemical
Cure Adhesive (3M Unitek, Monrovia, CA).
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 of resin from the gingival and contact
areas of the teeth with a scaler or contra-angle handpiece
and tungsten carbide bur.
118. CLEAR TRANSFER TRAYSAND
ADHESIVES
• Clear vinyl trays made on apressure-forming
machine suchasthe Biostar from Great Lakes
Orthodontics havelargely replaced the original
silicone tray materials.
• Advantage
– Provide aclear field of vision
– Canbe easily sectioned to facilitate clinicaldelivery
– Makes possible the useof light cured materialswith
light cureadhesive.169 118
119. • Clinical
– Improved patient comfort
– No separators or bandspcaes
– Better environment for placing ceramic bracketson
mandibular teeth
– Placement of brackets in the posterior , with level slots
and apassive archwire.
– Easierto build inovercorrections
– Better in/out control
– Improved vertical control
169 119
ADVANTAGES OF INDIRECT
BONDING.
120. – Optimal useof time and better staffutilization
– Fewer appliance placement appointments and
simplified and shortened debonding
– Healthier ergonomically
169 120
121. Disadvantages
• Technique sensitive
• Improper seating of indirect tray mayrequire complete redoing of
theprocedure.
• The risk for adhesive deficiencies under the brackets is
greater
• The risk for adhesive leakage to interproximal gingival areas
can disturb oral hygiene procedures.
• Amount of composite flash involves extra chair time toremove.
• Posterior attachments likely tofail
• Additional set of impressionsrequired
• Excessivelaboratory time isrequiredfor construction of the
indirectsetup
• Labcosts.
169 121
124. BONDING TO PORCELAIN
169 124
• A more common and successful alternative to create an
optimal retentive surface is the concept of etching the
porcelain surface.
• The most commonly used porcelain etchant is 9.6%
hydrofluoric acid in gel form.
• Although etching times vary anywhere from 1 to 2 minutes,
this porcelain etchant has been reported to yield
satisfactory results, and the gold standard seems to be 2
minutes, followed by silane application.
• The addition of silane after hydrofluoric acid treatment did
not significantly influence the bond strengths (failure rates
of 8.2% versus 8.6%).
125. 169 125
• Hydrofluoric acid is strong and requires separately bonding
to other teeth, careful isolation of the working area, cautious
removal of the gel with a cotton roll, rinsing with high-volume
suction, and immediate drying and bonding.
• The etchant creates micro porosities on the porcelain
surface that achieve a mechanical interlock with the
composite resin.
• The etched porcelain will have a frosted appearance similar
to that of etched enamel.
• Because of the caustic effects of hydrofluoric acid, several
alternatives, including acidulated phosphate fluoride gel, or
irradiation of ceramic surface with carbon dioxide or Er:YAG
lasers were proposed all with similar or better results,
compared with hydrofluoric acid.
126. 169 126
1. Adequately isolate the working field, and bond the actual
crown separately from the other teeth.
2. Use a barrier gel such as Kool-Dam (Pulpdent Corporation,
Watertown, MA) on mandibular teeth and whenever a risk
exists that the hydrofluoric acid etching gel may flow into
contact with the gingiva or soft tissues.
3. Deglaze an area slightly larger than the bracket base by
sandblasting with 50 microns of aluminum oxide for 3 seconds.
4. Etch the porcelain with 9.6% hydrofluoric acid gel for 2
minutes.
5. Carefully remove the gel with a cotton roll, and then rinse
using high-volume suction.
6. Immediately dry with air, and bond the bracket. Using a
silane is optional.
128. BONDING TO AMALGAM
169 128
Improved techniques for bonding to amalgam restorations may
involve
(1)modification of the metal surface (sandblasting, diamond
bur roughening)
(2) the use of intermediate resins that improve bond strengths
(e.g., ALLBOND 2 [Bisco, Inc., Schaumburg, IL], Enhance and
Metal Primer [Reliance Orthodontic Products, Itasca, IL]).
(3) new adhesive resins that chemically bond to nonprecious
and precious metals (e.g., 4-methacryloxyethyl trimellitate
anhydride [4-META] resins and 10-methacryloyloxi-decyl-
dihydrogen- phosphate [10-MDP] bisGMA resins).
129. 169 129
The following procedures are recommended for bonding to
amalgam.
Small amalgam filling with surrounding sound enamel.
1. Sandblast the amalgam alloy with 50 microns of aluminum oxide
for 3 seconds.
2. Condition the surrounding enamel with 37% phosphoric acid for
15 seconds.
3. Apply sealant, and bond with composite resin. Ensure the bonded
attachment is not in occlusion with antagonists.
Large amalgam restoration or amalgam only.
1. Sandblast the amalgam filling with 50 microns of aluminum oxide
for 3 seconds).
2. Apply a uniform coat of Reliance Metal Primer (Reliance
Orthodontic Products, Itasca, IL), and wait for 30 seconds (or use
another comparable primer according to the manufacturer’s
instruction).
3. Apply sealant, and bond with composite resin. Ensure the bonded
attachment is not in occlusion with antagonists.
131. 169 131
• In the first amalgam study the mean tensile bond strength to
sandblasted amalgam tabs ranged from 3.4 to 6.4
megapascal (MPa), in contrast to control bonds to human
enamel of 13.2 MPa.
• The strongest bonds to amalgam were obtained with a 4-
META adhesive (Superbond C&B, Sun Medical Co., Ltd.,
Kyoto, Japan), but an intermediate resin (All-BOND 2,
Bisco, Inc., Schaumburg, IL) and the Concise Enamel Bond
(3M Dental Products, St. Paul, MN) were comparable with
those of Superbond C&B.
132. 169 132
BONDING TO GOLD
• Different new technologies, including sandblasting,
electrolytic tin-plating, or plating with gallium-tin solution
(Adlloy), the use of several different types of intermediate
primers, and new adhesives that chemically bond to
precious metals have been reported to improve bonding to
gold in laboratory settings.
• However, the high in vitro bond strengths to gold alloys have
not been confirmed by satisfactory clinical results when
bonding to gold crowns.
• In the clinical experience, even a combination of intraoral
sandblasting, coupled with the use of All-BOND 2 (Bisco,
Inc., Schaumburg, IL) or 4-META primers and followed by
bracket bonding with composite resin or special metal-
bonding adhesives, may not optimally withstand the occlusal
forces in clinical practice.
133. 169 133
• Distinct difference between natural enamel or ceramic
restorations and metal restorations is that curing light cannot
travel through alloy or metal, and the amount of free radicals
produced and the degree of conversion
• seem to be significantly less when bonding on the metal
surface than on the enamel surface.
• Recently, it was demonstrated that primer precuring at the
bracket base is required for secure bracket bonding on gold
alloy surfaces using LED-curing units.
• Further evaluation of this phenomenon is required for
bonding to various gold alloys and large amalgam
restorations.
134. 169 134
Bonding to Composite Restoratives
• 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 after thorough air drying appear
to be clinically successful in most instances.
• The use of an intermediate primer is probably advantageous
as well.
135. 169 135
REBONDING
• The loose metal bracket removed from the archwire should
first be inspected for any possible deformation of the slot that
may have occurred during breakage.
• A bracket that seems to be deformed should be replaced with
a new one. Any adhesive remaining on the tooth surface is
removed with a tungsten carbide bur.
• The adhesive remaining on the loose bracket is best treated
by sandblasting until all visible bonding material is removed
from the base.
• The tooth is then etched with phosphoric acid gel for 15
seconds.
• On inspection, the enamel surface may not be uniformly
frosty because some areas may still retain resin.
136. 169 136
• The phosphoric acid will re-etch any exposed enamel and
remove the pellicle on any exposed resin.
• After priming, the bracket is rebonded.
• The neighboring brackets are first religated, and then the
rebonded bracket is ligated.
• The bond strength for sandblasted rebonded brackets is
comparable to the success rate for new brackets, but it
should be noted that the brackets’ SBS decreased as the
size of the aluminum oxide particle used for sandblasting
increased and as recycling was repeated.
137. 169 137
DEBONDING
• The objectives of debonding are to remove the attachment
and all the adhesive resin from the tooth and to restore the
surface as closely as possible to its pretreatment condition
without inducing iatrogenic damage.
• To obtain these objectives, a correct technique is
fundamentally important.
• Debonding may be unnecessarily time consuming and
damaging to the enamel if carelessly performed or
performed with an improper technique.
138. 169 138
Enamel Tearouts and Cracks (Fracture Lines)
• Localized enamel tearouts have been reported to occur
associated with bonding and debonding metal and ceramic
brackets.
• Ceramic brackets using chemical retention cause enamel
damage more often than those using mechanical retention.
• A recent study demonstrated enamel tearouts in 26% of
debonded polycrystalline brackets and in less than 1% of
monocrystalline brackets with an average volume loss of 144
and 36 cubic micrometers (mm3), respectively.
• This damage probably occurs because the location of the
bond breakage is at the enamel–adhesive interface rather
than at the adhesive–bracket interface.
139. 169 139
• The sharp sound sometimes heard on the removal of
bonded orthodontic brackets with pliers is possibly
associated with the creation of enamel cracks.
• With ceramic brackets, the risk for creating enamel cracks is
greater than for metal brackets.
• The lack of ductility may generate stress in the adhesive–
enamel interface that may produce enamel cracks at
debonding.
140. 169 140
The clinical implications are
(1) to use brackets that have mechanical retention and
debonding instruments and techniques that primarily leave all
or the majority of composite on the tooth.
(2) to avoid scraping away adhesive remnants with hand
instruments.
• Another important clinical implication may be the need for a
pretreatment examination of cracks, notifying the patient
and the parents if pronounced cracks are present
141. 169 141
Removal of Residual Adhesive
• Debonding of brackets usually leaves a residual adhesive
volume of 0.6 to 2.48 mm3 on the enamel surface.
• Complete removal of all remaining adhesive is not easily
achieved because of the color similarity between present
adhesives and enamel.
• The preferred method for the removal of excess adhesive is
to use a suitable dome-tapered tungsten carbide bur (No.
1171 or No. 1172) in a contra-angle handpiece.
• Clinical experience and laboratory studies indicate that
approximately 30,000 rpm is the optimum for rapid adhesive
removal without enamel damage.
142. 169 142
• Zachrisson and Årtun compared different instruments
commonly used in debonding procedures and ranked their
degrees of surface marring on young permanent teeth.
• According to the results of this study, plain cut and spiral
fluted tungsten carbide burs operated at approximately
25,000 rpm were the only instruments that provided the
satisfactory surface appearance ; however, none of the
instruments tested left the virgin tooth surface with its
perikymata intact.
• Recent research shows, however, that the use of carbide
burs alone removes a substantial layer of enamel and
roughens its surface and thus should be followed by
multistep Sof-Lex disks and pumice slurry, which is
reported as a reliable method of polishing.
143. 169 143
• Some patients complain about color change of their teeth
during and after orthodontic treatment.
• A recent study confirms this and states that both the
orthodontic adhesive systems and the burs used to remove
their residuals on tooth surfaces are responsible for this
effect.
• The authors suggest using STAINBUSTER burs (Pearson
Dental Supply Co., Sylmar, CA) to remove the adhesive
remnants close to the enamel surface.
144. 169 144
A Novel Etchant System for Orthodontic
Bracket Bonding
A. I. Ibrahim V. P. Thompson & S. Deb. July 2019
• Current bonding systems that can maintain shear bond
strengths (SBS) suitable for clinical performance are unable
to limit enamel demineralisation, adhesive remnants and
damage caused on removal of brackets after treatment.
• This study reports a novel “safe enamel etch” clinically
viable procedure that was accomplished via application of
novel etchant pastes developed with β-tricalcium phosphate
and monocalcium phosphate monohydrate powders mixed
with citric acid (5 M) or phosphoric acid (37% PA) to yield
BCA and BPA etchants respectively.
145. 169 145
• Although enamel etched with clinically used PA gel yielded
higher SBS than the BCA/BPA etchants, it exhibited greater
adhesive remnants with evidence of enamel damage.
• In contrast, the experimental etchants resulted in
unblemished enamel surfaces with zero or minimal adhesive
residue and clinically acceptable SBS.
• Furthermore, the BPA etchant caused lower enamel
decalcification with extensive calcium-phosphate
precipitation.
• The study conclusively showed that BPA facilitated in vitro
enamel adhesion without detrimental effects of the
aggressive PA gel with potential for remineralisation and
saving time at the post-debonding step.
146. 169 146
Operator Safety during Debonding
• Another important but often ignored issue is the inhalation of
aerosols produced during the removal of fixed orthodontic
appliances.
• Recent research showed that aerosol particulates produced
during enamel cleanup might be inhaled, irrespective of
handpiece speed or the presence or absence of a water
coolant.
• This aerosol may contain calcium, phosphorus, silica,
aluminum, iron and lanthanum.
• Blood, hepatitis B surface antigen (HBsAg), and hepatitis B
virus–DNA were also detected in excess fluid samples of the
two hepatitis B carriers.
147. 169 147
• Although the particles are most likely to be deposited in the
conducting airways and terminal bronchi, some might be
deposited in the terminal alveoli of the lungs and cleared
only after weeks or months.
• Results of these reported studies indicate that orthodontists
are exposed to high levels of aerosol generation and
contamination during the debonding procedure, and
preprocedural chlorhexidine gluconate mouth rinse appears
to be ineffective in decreasing the exposure to infectious
agents.
• Barrier equipment should be used to prevent aerosol
contamination.
148. 169 148
PREVENTION AND REVERSAL OF
DECALCIFICATION
• White spots or areas of demineralization are carious lesions of
varying extent.
• One prospective study found that 50% of individuals undergoing
fixed appliance treatment had nondevelopmental white spot
lesions (WSLs), compared with 25% of a control group of
patients. (Hadler-Olsen S, Sandvik K, El-Agroudi MA, et al. The
incidence of caries and white spot lesions in orthodontically
treated adolescents with a comprehensive caries prophylactic
regimen—a prospective study. Eur J Orthod. 2012;34:633–639).
• Another study173 found that, even 5 years after treatment,
orthodontic patients had a significantly higher incidence of WSLs
than a control group of patients who had not had orthodontic
treatment. (Karabekiroglu S, İleri Z, Kahraman FB, et al. The
effects of fixed orthodontic treatment period on white spot lesion
prevalence and DMFT index. J Istanbul Univ Faculty Dent.
2014;48:27–35).
149. 169 149
• Daily rinsing with dilute (0.05%) sodium fluoride solution
throughout the periods of treatment and retention, plus
regular use of a fluoride dentifrice, is recommended as a
routine procedure for all orthodontic patients.
• Professional means of fluoride application have included
fluoride-releasing bonding agents, fluoridated elastomeric
ligature ties, fluoride varnish, and 10% casein
phosphopeptide- amorphous calcium phosphate.
• The professional application of 1% chlorhexidine collagen
gel is also suggested to control Streptococcus mutans
levels in an orthodontic patient with a high risk of caries.
150. 169 150
MICROABRASION
• When the remineralizing capacity of the oral fluids is
exhausted and WSLs are established), microabrasion is the
optimal way to remove superficial enamel opacities.
• By the use of this technique, enamel stains can be
eliminated with minimal enamel loss.
151. 169 151
Clinical procedure: A custom-made abrasive gel is prepared with
18% hydrochloric acid, fine powdered pumice, and glycerin. The
active mixture is applied as follows:
1. The gingiva is isolated using blockout resin or rubber dam.
Dental floss may be useful to prevent soft tissue contact and
injury from the acid.
2. The abrasive gel is applied using an electric toothbrush for 3 to
5 minutes. The original toothbrush tip is modified by cutting the
peripheral bristles to create a smaller brush tip to fit better on
tooth surfaces.
3. Rinse for 1 minute.
• To prevent enamel pitting, the acid should not be left on the
tooth for an extended time. For best results and depending on
the severity of the lesions, the procedure can be repeated
monthly two to three times, which gradually makes the stains
disappear.
152. 169 152
RESIN INFILTRATION
• More recently, a minimally invasive treatment approach was
introduced, during which the WSL is infiltrated using a low-
viscosity resin (ICON resin infiltrant, DMG, Hamburg,
Germany).
• In this technique, the outer surface is transformed into a
more permeable layer with the help of hydrochloric acid
etching, and the porous structure beneath is infiltrated using
a TEGDMA-based resin.
• It is noteworthy that this resin has a light refraction index
similar to sound enamel, which improves the appearance of
the lesion and reinforces the weakened enamel prism
structure.
153. 169 153
Clinical procedure :
1. Prophy teeth; rinse and dry.
2. Etch WSL with an Icon-Etch syringe (DMG America,
Englewood, NJ), extending approximately 2 mm around the
edges of the lesion for 2 minutes.
3. Rinse for 30 seconds, and completely dry with oil-free air.
4. Apply Icon-Dry (99% ethanol) (DMG America, Englewood,
NJ) to the dried surface, and leave undisturbed for 30
seconds. Dry completely with air.
154. 169 154
5. Apply ICON resin infiltrant (DMG, Hamburg, Germany) with
a vestibular tip, and remove the direct overhead light source
to avoid premature curing of the infiltrant. Leave undisturbed
for 3 minutes. Maintain a moist surface by continuing to add
infiltrant periodically during this time to ensure an adequate
supply of resin to the lesion.
6. Remove any excess material, and light cure for 40
seconds.
7. Repeat the infiltration process with a new vestibular tip.
Leave undisturbed for 1 minute, remove excess again, and
light cure an additional 40 seconds.
8. Polish the teeth.
155. 169 155
How and why of orthodontic bond failures: An in
vivo study
R. K. Vijayakumar, Raju Jagadeep, Fayyaz Ahamed, Aprose Kanna, K. Suresh
• The aim of this study is to highlight the use of a simple,
inexpensive and ease of manipulation of a single
thermo-plastic transfer tray and the use the of a single light
cure adhesive to evaluate the bond failure rates in clinical
situations.
• Total of 30 patients were included in this study (18 females,
12 males, mean age 21.73 years, range: 15-28 years).
• A total of 518 brackets, were bonded, of which 256 were
placed using direct bonding technique and 262 were placed
using indirect bonding technique.
156. 169 156
RESULTS
• A total of 50 brackets were debonded from both groups
(9.6% failure rate) over observation period of 6 months.
• Of the brackets placed with direct bonding technique, 27
brackets debonded (10.5% failure rate), whereas 23
brackets debonded (8.8% failure rate) when using indirect
bonding technique.
Bond failure rate for anteriors and posterior brackets for
both procedures:
In the anterior teeth, 19 brackets failed (10.8% failure rate)
with direct bonding technique and 11 brackets failed (6.2%
failure rate) with indirect bonding technique. In the posterior
teeth, 8 brackets failed (9.8% failure rate) with direct bonding
technique and 12 brackets failed (14.4% failure rate) with
indirect bonding technique.
157. 169 157
Failure rate for individual tooth:
• Individual tooth failure rate showed, in-direct bonding
technique mandibular centrals had highest failure rate of
20% followed by maxillary canine of 16.6%, whereas in
indirect bonding technique, mandibular 2nd premolars had
highest failure rate of 18.8% followed by mandibular 1st
premolar and maxillary 2nd premolar of 16.6% respectively.
CONCLUSION:
This study concluded, that bond survival rate in both the
methods, using the transparent thermo-plastic transfer tray of
2 mm thickness, had no significant differences between them.
158. 169 158
A 15-month evaluation of bond failures of
orthodontic brackets bonded with direct versus
indirect bonding technique: a clinical trial
Anna Menini et al , 2014
• The purpose of this clinical longitudinal study was to
investigate the effectiveness of indirect bonding technique
evaluating the number of bond failures which occurred
during treatment.
Results: No statistically significant differences were found in
the total bond failure rate between direct (3.54%) and indirect
techniques(5.70%), also when comparing the upper and lower
arches.
• The only significant difference was found comparing the
posterior segment of the lower arches, in which a higher
percentage of detachments were recorded in group
B(17.54%), bonded with the indirect technique.
159. 169 159
An audit of bonding failure among orthodontic
patients in a tertiary hospital in South-South Nigeria.
WOLTERS KLUWER,International Journal of Orthodontic Rehabilitation /volume 8 /
Issue 3 / July-September 2017
• The objective the study was to assess the prevalence of
bonding failure among orthodontic patients at the University
of Port Harcourt Teaching Hospital,Rivers State, Nigeria.
• In all, there were 42 patients comprising 26 (61.9%) females
and 16 (38.1%) males with an age range of 7–35 years and
mean age of 14.7 ± 7.8 years.
• Thirty-five (83.3%) patients had maxillary and mandibular
fixed orthodontic appliances, two (4.8%) had maxillary fixed
appliances only, while five (11.9%) had partially fixed
appliances consisting of two bands and four brackets on the
maxillary and/or mandibular incisors.
160. 169 160
RESULTS:
• Out of a total of 905 brackets bonded, 154 debonded over
24 visits of the patients. A bond failure rate of 17.0% was
observed.
• Second premolars had a higher loss of 72 (46.8%).
• The mandibular left second premolars had the greatest loss
of 24 (15.6%). The maxillary anterior teeth had the least
bracket loss of 20 (13%).
• Bracket loss was higher in the mandible than the maxilla:
102 (66.2%) and 52 (33.8%), respectively, and on the left
side 79 (51.3%) than the right side 75 (48.7%) of the jaws.
• Brackets placed on mandibular premolars had the highest
failure rate. Therefore it is recommend that special attention
be paid when bonding brackets to premolar teeth.
161. 169 161
Comparing orthodontic bond failures of light-cured
composite resin with chemical-cured composite
resin: A 12-month clinical trial.
Rufaida E. Mohammed. et al, AJODO August 2016.
• The aim of this study is to evaluate and compare bond
failure rates of light-cured composite resin vs chemical-
cured composite resin for 12 months.
• There were 22 patients in this study, providing a total of
356 teeth.
• Their minimum age was 13 years, and their maximum age
was 32 years. The mean age was 20.24+5.57 years.
• The overall failure rate was 2.8%. There were no
significant differences in bond failures between chemical-
cured composite and light-cured composite bonded teeth.
162. 169 162
• The right side of both the maxillary and mandibular arches
had a higher failure rate (3.4%) than the left side (2.3%).
• The highest failure rate was observed for the second
premolars (7.7%).
• The failure rate was lower in the maxillary teeth (2.3%) than
in the mandibular teeth (3.3%) and was higher in the
posterior teeth (6.7%) than in the anterior teeth (1.2%).
• The mean survival times were 528 months for brackets
bonded with light-cured composite and 349 months for the
chemical-cured composite.
CONCLUSIONS
• Based on this investigation, the following conclusions can
be drawn.
1. The overall failure rate of the brackets was 2.8%, which is
within the acceptable range for clinical use.
2. Type of bonding agent did not influence the bracket
survival rate significantly.
163. 169 163
BEATING THE BOND FAILURE
• Variability of bond-failure rates using SEP is due to the lack
of surface preparation and using noncompatible adhesives.
Therefore it is recommend that SEP only be used with an
adhesive with which it has been shown to be compatible.
• Using precoated brackets reduces bond failures. Variability
exists when “buttering” brackets, so the additional expense
of precoating is offset by a reduction in bond failure. This
creates a no-mix, unit-dosed system that, when properly
executed, reduces the number of steps and lessens the
opportunity for failure.
• Bright, well-maintained lights are essential to properly cure
adhesives used in orthodontic bonding. LED lights are the
latest in convenience because of their size, portability, and
brightness; however, they do require testing and
maintenance.
164. 169 164
• Large bases that are well-adapted to the facial surface of the
teeth should be used on all posterior teeth, especially molars.
• Offset bases should be used on all premolars to increase the
surface area and maximize bond strength.
• Perhaps the most important step after initial bracket
placement is to use temporary bite-opening mechanics to
provide clearance during closure.
• The final step requires a change that many team members
resist at first, and that is the use of a dry field system. In a
two-handed technique, there is often lag time between
bracket placement and final positioning. This is an
opportunity for contamination from saliva to weaken bond
strength. The dry field system reduces this variable. This
technique does take time to acquire the skill of placement,
and some patients do not tolerate it well, but it is well worth
mastering.
165. 169 165
CONCLUSION
• Today, adhesive resins, direct bonding, and light curing
units are a very important part of the modern orthodontist’s
armamentarium.
• Our distinguished profession would not have been
popularized without the application of direct bonding and
advances in the material science.
• Similar to any other material, composite resins and bonding
have their particular benefits and drawbacks.
• Beyond a doubt, modern orthodontists need to have a
thorough knowledge and comprehension of the materials
available so that they can choose the best product available
for their particular needs and to make the best use of them.
166. • In the past, the best clinical results were achieved by
orthodontists who had the best wirebending skills.
• However, the best results in the future will be achieved by
those orthodontists who are best at accurate bracket
positioning.
• Most of the problems associated with bonding techniques
have faded away.
169 166
167. REFERENCES
• Orthodontics current principles and techniques: sixth
edition Graber, Vanarsdal, Vig, Huang
• Contemporary Orthodontic Appliance 6th ed –William R.
Proffit.
• Orthodontic materials. Scientific and clinical aspects.
William A. Brantley, Theodore Eliades.
• A Colour Atlas of Acid Etch Technique – J.J. Muray,T.G.
Bennet.
• The evolution of bonding in orthodontics ,Paul Gange -
Am J Orthod Dentofacial Orthop 2015;147:S56-63).
• Crystal growth on outer enamel surface - AJO- DO 1986;
89:183 - 193 , Maijer and Smith.
169 167
168. 169 168
• Variation in the Pattern of Acid Etching of Human Dental
Enamel Examined by Scanning Electron Microscopy L. M.
SiLVERsroNE, C. A. Saxton, I. L. Dogon and O. Fejerskov.
• Novel Etchant System for Orthodontic Bracket Bonding A. I.
Ibrahim, V. P. Thompson & S. Deb.
• How and why of orthodontic bond failures: An in vivo study. R.
K. Vijayakumar, Raju Jagadeep, Fayyaz Ahamed, Aprose
Kanna, K. Suresh.
• A 15-month evaluation of bond failures of orthodontic brackets
bonded with direct versus indirect bonding technique: a clinical
trial. Anna Menini et al.
• An audit of bonding failure among orthodontic patients in a
tertiary hospital in South-South Nigeria. Wolters Kluwer,
International Journal of Orthodontic Rehabilitation.
• Comparing orthodontic bond failures of light-cured composite
resin with chemical-cured composite resin: A 12-month clinical
trial. Rufaida E. Mohammed, et al AJO-DO august 2016.
CTE of enamel is around 11.4×10-6ºC-1 and dentin around 8.0×10-6ºC-1, while the CTE for restorative materials is different, such as resin composite materials with a CTE of 17-50×10-6 C-1
Brazing: lower mp of filler than base metal and no melting of base metal
Welding higher mp, melting of base metal
W e a k acids
2. 5 % nitric acid
1 7% maleic acid for 30-60 seconds
Organic acid
Maleic acid , E DTA ,citric acid, tartaric acid.
Anti sialogogues: atropine, scopalamine, glycopyrollate
Full arch access to completely eliminate saliva
Inorganic acid
phosphoric acid, nitric acid.
Polymeric acid
poly acrylic acid
The bleaching produces oxygen, which inhibits free radical polymerization of resin composites.
ERBIUM
ABLATION- REMOVAL
Increased exposure of components induces oxygen inhibition.
Mixing introduces in the form of air entrapment and formation of voids.
The degree of cure does not exceed 55%.
Inhomogenous polymerization pattern due to sandwich technique involved in the diffusion of liquid component into the paste during application.
Similar degree of cure.
camphorquinone
More bond strength than light cured and chemical curedm24 hours following activation.
Dc value was highest amongt the adhesives used
With this approach debonding rate is said about 5%.
In this product, a new transparent APC adhesive formulation is contained within a form-fitting fiber mat on the base of the bracket.
The manufacturer claims that when the flash-free adhesive coated bracket is placed on the tooth, the adhesive spreads out and conforms to the tooth surface, making
uniform and consistent contact with no flash to clean.
Hydrofluoric acid will not be effective for bonding to high-alumina porcelains and glass ceramics, and new technique improvements are needed for successful orthodontic bonding to such teeth. A newly introduced alternative technique to the use of hydrofluoric acid gel may be silica coating,127–129 but further clinical trials are needed to obtain experience with the
silica- coating technique.
The burs are made up of the fiber sections with abrasive power, which cover the entire working surface and split up into small fragments as they act on a hard surface.
a minimum range of 6–10 MPa has been suggested as suitable for bracket bonding
however, the mean SBS obtained from BPA paste subgroups ranged between 18.2–25.4 MPa, which were well above the lower limit for acceptable clinical performance.
MI Paste Plus (GC America Inc, Alsip, IL, USA) is a water-based, sugar-free crème containing Recaldent casein phosphopeptide–amorphous calcium phosphate (CPPACPF) and fluoride.
Lesions that occur from demineralization are the only suitable candidates for this procedure. Lesions from fluorosis, hypocalcification, hypoplasia, erosion, developmental
anomalies, or trauma leading to enamel defects are not appropriate for caries infiltration.
Split‑mouth design
Group A: Consisted of fifteen patients with maxillary right and mandibular left quadrants bonded using direct bonding technique, whereas contra‑lateral sides were bonded using
indirect bonding technique.
A bond failure rate below 10% is clinically acceptable as suggested by Cal‑Neto et al.
In the literature, bonding failure rate varies from 1.57% to 55.6%.[
This high bond failure rate in the second premolars may be related to the difficulty with moisture control at bonding or higher masticatory forces and greater amounts of prismatic enamel that may affect the quality of the micromechanical bond
