Download direct bond1ng indirect bonding

Anaap Sandhi, DDS, MS'
Aim: To develop a cohesive and complete system for fabricating bonding trays and an effective indirect bonding procedure.Material and Methods: A new resin designedspecificallyfor
indirect bonding has been developed. Previous problems with indirect bonding systems,
which were partly related to the fact that resins designed for direct bonding had to be used,
have been addressed.Conclusion: A cohesiveand complete system for fabricating bonding
trays and for the indirect bonding procedure is presented. World J Orthod 2001;2:106-114.
DIRECT BOND1NG
T he transition from removable to fixed appliances
made greater precision in tooth movement possible. However, the initial fixed appliances attached
brackets and tubes to the patient's teeth with bands,
and there were significant limitations in the degree
of accuracy possible with these cemented bands.
During the 1970s, two parallel developments had a
profound impact on orthodontic treatment with fixed
appliances. The development of pretorqued and preangulated brackets permitted a more sophisticated
degree of detail in finishing the occlusion. Further,
the development of direct bonding made greater precision in the placement of these preadjusted brackets an achievable goal. It remains possible to move
teeth, and to achieve a good orthodontic result, without preadjusted appliances. However, a substantial
improvement in both the efficiency and the effectiveness of fixed appliance mechanics can now be
achieved with the accurate placement of preadjusted
brackets. It has always been important that the finished orthodontic result be esthetically and functionally the achievable optimum, and our enhanced
understanding of occlusion and occlusal function
has been coupled with the efficient application of
biomechanics in the design of increasingly advanced
preadjusted edgewise appliances.
The transition from banded attachments to direct
bonded attachments has significantly
improved
orthodontists' ability to attain accurate bracket positions. However, with chemically cured bonding
resins, working time is fairly limited, and this presents an additional challenge in trying to bond posterior teeth. The introduction of light-cured resins like
Transbond (3M Unitek, Monrovia, CA, USA) allows
increased working time, thereby permitting significant latitude in positioning the brackets before the
resin is cured. Despite this increased flexibility,
achieving accurate and consistent bracket positions
on posterior teeth continues to present a problem,
due to poor access. Since rebonding brackets and
tubes on posterior teeth is no easier than bonding
them the first time, bracket repositioning is best
kept to a minimum. Most clinicians direct bond
brackets on anterior teeth and premolars but avoid
direct bonding on molars. Indeed, some clinicians
prefer to band not only the molars, but also the second premolars.
INDIRECT BONDING
The concept of indirect bonding was first mentioned in
the literature during the mid- to late 1970s, and various modifications
of the process have been
reported.1-6 In the initial efforts at indirect bonding,
taffy candy was used to position brackets on the teeth,
and filled chemically cured resins were employed to
1PrivatePracticeof Orthodontics,Indianapolis,Indiana, USA.
REPRINT REQUESTS/CORRESPONDENCE
Dr Anoop Sandhi, 9333 North Meridian, Suite 301, Indianapolis,
IN 46260, USA. E-mail: [email protected]
106
Advantages of indirect bonding
bond the brackets to the teeth. Although this method
was effective, it generated a significant amount of
flash, and cleaning up the resin presented a definite
problem. The technique also was awkward and
Iinvolved a significant amount of clinical and laboratory
There are significant
1.
2.
3.
4.
5.
6.
time. Alternative adhesives have been tried over the
years, but all have proved only moderately successful.
The next major improvement in methodology
occurred during the 1980s, when heat-cured resins
entered the market. However, there were reports of
clinicians experiencing problems with bracket float
during the heating required to cure the resin. Casts
had to be heated to 250°F to 300°F for approximately 15 to 20 minutes to cure the resin (Thermacure, Reliance Orthodontic Products, Itasca, IL, USA).
Some nonceramic esthetic brackets could not be
exposed to such heat, and had to be placed separately, after the metal brackets had been heat
cured-a cumbersome procedure.
When the bracket bases are constructed with
heat-cured resin, bonding placement is generally
accomplished with chemically cured sealants or
bonding resins. However, if a transparent tray is
used, a light-cured resin with cure-on-demand benefits is an alternative.7
advantages to indirect bonding:1-7
Bracket placement is accurate
Use of the orthodontist's time is optimized.
Band fitting on posterior teeth is avoided.
Need for separators is eliminated.
Ability to bond posterior teeth is improved.
Patient comfort and hygiene are improved.
Disadvantagesof indirect bonding
1. Indirect bonding is technique sensitive.
2. Additional set of impressions is needed.
3. Posterior attachments are more likely to fail if the
patient abuses the appliance by chewing ice, etc.
ACCURACYIN
BRACKET PLACEMENT
Orthodontic appliances are now engineered with
increasingly sophisticated computerized design and
a vast array of tips, torques, labiolingual offsets, and
rotations are available to the clinician. However,
some of this precision is lost when brackets are
applied to the teeth in an indiscriminate manner.
A number of bracket placement systems have
been proposed over the years. To realize the full
potential of a preadjusted edgewise appliance, the
system for bracket placement must be reliable and
consistent. The orthodontist must be prepared to
incorporate variations in bracket placement dictated
by the malocclusion. The positioning of brackets
clearly would be different in treatment of patients
with open bites versus patients with deep anterior
overbites. Kalange has proposed, for example, that
the incisal edges of anterior teeth be recontoured
prior to bracket placement.8 It is precisely this sort
of variation that maximizes the efficiency of bracket
placement with indirect bonding.
Previous resins used in
indirect bonding
With the increasing popularity of indirect bonding over
the past two decades, different methods of bonding
the brackets to the teeth have been developed. Initially, brackets were positioned on the casts and the
bonding was accomplished with a filled resin. The
indirect transfer trays were usually formed with silicone tray materials. The bond strength achieved with
filled resins was adequate, but the technique, particularly the clean-up, was difficult. It became apparent
that one of the deficiencies in the available systems
arose from the fact that all the resins and procedures
had been designed for direct bonding and had subsequently been adapted for indirect bonding.
A generous window of working time is an important property in a resin designed for direct bonding.
This property has no advantage in indirect bonding,
since there is no need for an extended cure time
once the tray has been placed in the mouth. Therefore, a resin designed specifically for indirect bonding was needed. After innovation, laboratory testing,
and clinical trials, an efficient and effective indirect
bonding procedure was created. One benefit of this
procedure is that it does not require heating the
casts, since a custom base of the bracket is developed with light-cured resin.
DEVELOPING A CUSTOMIZED
RESIN BASE
In an effortto determine the best method for preparing a custom resin base, a number of clinical trials
were completed. It was the author's finding that
light-cured resin is a quick and efficient material for
placing brackets on models and for forming a custom resin base. Using adhesive precoated (APC)
brackets. contamination is eliminated and laboratory
107
Fig 1 (a) Anterior view of the working cast. (b) Occlusal view of the working cast. Note the detail of dental and
soft tissue structures, and an absence of any bubbles or voids. (c) Separating medium being applied to the maxillary
working cast.
LABORATORVPROCEDURE
time is cut to a minimum, since individual brackets
do not need to be sorted or have resin applied to the
base before placing on the model. If APC brackets
are not used, the author recommenps Transbond XT
for preparation of the resin bases. Other resins, with
lighter viscosities, have proven to be ineffective due
to bracket float.
For the indirect bonding procedure, this clinician
now uses the new indirect resin, with APC brackets
(or Transbond XT adhesive applied in the lab), for the
custom base. This article provides a step-by-step
explanation of the indirect bonding procedure.
Preparation of the bonding trays
by the technician
1. Working casts in orthodontic stone, prepared
from accurate alginate impressions, are necessary. Careshould be taken to ensure that there is
no distortion of the impressions. The working
casts should be prepared with careful trimming,
removal of bubbles, and filling of small voids. If
there are large bubbles or voids, it will affect the
fit of the bondingtray (Figs1a and 1b).
2. A thin layer of diluted AI-Cote(Dentsply International, York, PA, USA)separating medium (1 to 4
with water) should be applied to the model and
allowedto dry for approximately1 hour (Fig 1c).
3. If APCbracketsare used,the preorientedbrackets
may be removed directly from the sealed blister
pack and positioned on the individual teeth. The
excessadhesiveshould be removed,and the position of the bracket should be carefully checked
with a bracket gauge. If noncoated brackets are
used,TransbondXTLight CureAdhesiveshould be
placed on the mesh pad of individual brackets
beforethey are positionedon the cast (Fig2).
4. Onceall brackets have been placed, a final check
of the bracket positions can be completed and
the excess resin removed. The casts should be
placed in the black plastic box provided with the
resin, and left for final approval and positioning
by the doctor (Figs3 and 4).
5. When all the bracket positions have been
checked, the maxillary and mandibular casts
should be placed in the TRIAD (TRIAD 2000,
Dentsply International) curing unit and cured for
10 minutes. Although the resin will cure more
quickly, extra time is allowed to ensure complete
A NEW INDIRECT BONDING RESIN
A resin designed specifically for indirect bonding was
developed with the help of 3M Unitek (Sondhi RapidSet Indirect Bonding Resin, 3M Unitek). This material
was designed with several objectives in mind. An
unfilled resin lacks any significant viscosity, and is
not capable of filling the small imperfections in the
custom base formed with light-cured resin or any
imperfections in the fit of the custom base against
the enamel. The viscosity of this resin has been
increased with the use of a fine-particle fumed silica
filler (approximately 5%), so that it is capable of filling in such voids without compromising
bond
strength. The resin was developed with a quick set
time of 30 seconds, thereby significantly decreasing
the time needed to hold the bonding tray in place.
The resin is completely cured in 2 minutes, allowing
relatively rapid removal of the bonding tray. This
resin has been specifically designed for indirect
bonding and would not be useful for direct bonding.
The complete indirect bo'nding procedure, from
the laboratory process to clinical delivery of the
appliance, is described and illustrated below.
108
Fig 2 APC brackets being placed
on the teeth. If APC brackets are
not used, then Transbond XT
should be applied to the bracket
bases.
Fig 3
Final bracket placement.
checked by the orthodontist.
Indirect bonding permits viewing the
brackets
and casts in all three
dimensions for optimal rotation and
angulation.
Fig 4 Detail of the bonding setup, which demonstrates the ability
to control axial inclinations of second molars with the initial archwire.
Fig 5 (Left) Indirect bonding casts placed
in the TRIAD 2000 light-curing chamber. The
rotating tray table permits light exposure to
bracket bases from all directions.
Fig 6 (Below) Brackets are sprayed with a
light cooking spray prior to forming the indirect bonding tray. This permits easier tray
removal following bonding of the brackets.
curing because the access to light between the
plaster cast and the bracket base is limited. The
amount of time for light curing is substantially
reduced with clear esthetic brackets, and 1
minute of exposure to the light should be adequate (Fig 5). Curing can be done with a chairside
light-curing unit if a light chamber is not available.
6. Before forming the indirect bonding trays, a light
separating spray should be used to facilitate
easy removal of the tray from the brackets. A silicone spray or a light cooking spray, such as Pam
(International Home Foods, Parsippany, NJ, USA),
may be used. The brackets should be sprayed
lightly and for less than 1 second (Fig 6).
7. The indirect bonding trays can now be placed
over the brackets. The author uses a Biostar
(Great Lakes Orthodontics, Tonawanda, NY, USA)
unit to vacuform a 1.5-mm-thick layer of Bioplast
(Great Lakes Orthodontics) overlaid with a 0.75mm-thick layer of Biocryl (Great Lakes Orthodon-
tics). The Bioplast layer is vacuformed onto the
cast first, and the excess material is trimmed off
(Figs 7a and 7b). The Bioplast surface should be
sprayed with a silicone spray or a light cooking
spray before the Biocryl is adapted, which will
permit easier separation of the two layers. The
hard outer shell should be trimmed away from all
heights of contour for patient comfort and closer
fit, since its purpose is only to permit firm seating
of the soft tray. The outer layer provides rigidity to
the bonding tray, and the inner layer permits easier removal of the tray (Figs 7c and 7d).
8. When a bonding tray made with a silicone transfer
material is used, the Biostar unit is not necessary
(Fig 8). A bonding tray can be made with a suitable silicone transfer material. Once the putty has
been mixed with the activating agent, a small button of the silicone material can be placed around
individual brackets, followed by the placement of
the remaining material, which is rolled into the
109
I Sandhi
WORLD JOURNAL OF ORTHODONTICS
Fig 7 (8) Cast with first layer of Bioplast. (b) The excess material around the base of the
cast being trimmed. (c,d) Occlusal and lateral views of the indirect bonding tray. The hard
outer shell of Biocryl provides rigidity to the tray.
Fig 8 (a) Superior view of an indirect bonding tray formed with Express silicone impression
material. A putty tray of this kind can be used if a vacuformed tray is not desired or a Biostar
is not available. (b) Posterior view of a silicone transfer tray, demonstrating bracket positions
and tray trimming around the hooks.
shape of a cylinder. The occlusal and lingual surfaces of the teeth should also be covered with the
tray material, as has been described by Kalange.8
9. The casts are soaked for approximately 1 hour to
permit the separating medium to dissolve. This
allows easier separation of the bonding trays. The
bonding trays are now removed from the casts and
should be sectioned off with a bur (Fig 9a). It may
be necessary to tease the tray off with a scaler.
Any excess material should be trimmed with crown
and bridge scissors or a scalpel. Once the bonding
trays have been trimmed, they should be placed in
the TRIAD unit for an additional minute to ensure
that any uncured resin is cured (Fig 9b).
10. The trays should now be cleaned with a dishwashing detergent (eg, Dawn, Proctor & Gamble,
Cincinnati, OH, USA) in an ultrasonic cleaner for
10 minutes. The trays are then run through the
ultrasonic cleaner, in water only, for an additional
5 minutes. They are then rinsed and dried thoroughly (Fig 10 shows external and internal views
of the maxillary bonding tray).
11n
Fig 9 (a) Vacuformed indirect bonding tray is removed from the cast. (b) Trimmed indirect
bonding trays in the TRIAD chamber for additional curing. One minute of additional curing is
recommended to ensure complete curing of the resin base.
Fig 10
External and internal views of a maxillary bonding tray.
CLINICAL PROCEDURE
5. If there are bands to fit. this should be done
after the indirect bonding procedure has been
completed. The resin used in this indirect bonding system has a fast set time, and the band fitting can be started immediately.
Preparing the patient
1. Seatthe patientand placea napkin aroundhis
neck. The author recommends the use of an
anti-sialagogue,such as Sal-Tropine(Hope Pharmaceuticals, Scottsdale, AZ, USA). Patients
should be instructed to remove contact lenses
when they take the anti-sialagogue tablet. In
addition, the orthodontist should be familiar with
all contraindications prior to recommending an
anti-sialagogue.
2. Pumice all teeth. Explainto the patient that this
is one of several procedures in preparation for
bonding.
3. Rinsethe mouth and suction well with water.
4. Show the bonding trays to the patient and
explain the procedure-from taking the impressions to placing the brackets in proper position
and forming the tray. It is important to stress the
time the orthodontist takes to position the brackets and supervise the entire process. There is
significant value in emphasizingthe importance
Placement of bonding trays
1. Whether the indirect bonding procedure can be
completed with a single tray for the entire arch,
or whether the tray needs to be sectioned into
two segments, is a decision based primarily on
the degree of isolation that is feasible. If there is
significant crowding and imbrication of the teeth,
it may be easier to section the tray. Since the
working time with the indirect bonding resin is
virtually unlimited, as the adhesive does not
need to be mixed, the degree of isolation and
ease of tray placement are the determining factors. On rare occasions, it may be advisable to
section the tray into thirds, in which case the
trays may be sectioned as follows:
. Teeth 13 to 23 or 33 to 43 (anterior segment)
. Teeth 14 to 17 or 24 to 27; 34 to 37 or 44 to
of proper bracket placement,and the doctor's
47 (posterior segment)
input on appliance design,to the patient.
111
2. Carefully examine the trays for any remaining
separator or tray material that may be covering
the adhesive custom base on the bracket. Use a
microetching unit to lightly sandblast the adhesive custom bases. A fine aluminum oxide particle (50 ~m) is recommended. Be careful not to
abrade the resin base.
3. If there is any contamination of the adhesive
custom bases, especially if you touch them with
your fingertips, the trays should be cleaned with
a detergent, rinsed, and dried. The application of
acetone to adhesive bases is not recommended,
since recent research has indicated that this
may have a degrading effect on the resin.
4. Isolate the teeth that are to be bonded, using the
Nola (Nola Specialties, Hilton Head, SC, USA)
dry-field system. If necessary, plastic cheek
retractors,
Tongue Away (TP Orthodontics,
laPorte, IN, USA), cotton rolls, and Dri-Angles
(Young Dental, Earth City, MO, USA) may be
used.
5. Dry teeth thoroughly with an air syringe.
6. Dab (do not rub) etching solution onto teeth and
set stopwatch for 15 seconds. The etching solution should be applied with extreme care; do not
allow it to contact skin or gingiva. The etch
should be applied in the general area that is to
be covered by the bracket. Do not allow the etch
to flow into the interproximal contacts. The cleanup will go more smoothly if this is kept in mind
ance is not apparent, repeat the etching process
for 15 seconds.
10. Small amounts of the Resin A and Resin B liquids should be poured into the wells (Figs 12a
and 12b). Take care to keep liquids separate.
Resin A can be painted onto the tooth surface
with a brush, and Resin B can be painted on the
resin pads in the indirect bonding tray (Figs 12c
and 12d).
11. If too much resin has been placed on the
enamel, gently remove the excess with a brush.
The overall method of painting the resin on the
enamel and the custom bases is similar to painting fingernails.
12. Position the tray over the teeth and seat the tray
with a hinge motion. With the fingers, apply equal
pressure to the occlusal, labial, and buccal surfaces. Hold for a minimum of 30 seconds (Fig
13a). Figure 13b shows the maxillary and mandibular bonding trays in place. Allow 2 more minutes of curing time before removing the trays. Due
to the rapid set time of this adhesive, removal of
the first tray can begin once the opposing tray is
placed (Fig 14). Figure 15 shows the completed
appliance placement.
13. Remove the tray by using a scaler to peel the
tray from the lingual to buccal. Use extreme
care when removing the tray from around
bracket wings. Scale the excess resin around
the brackets and from the interproximal contacts. Use dental floss to check that all contacts
are open.
14. Repeat steps 4 to 13 for the remaining trays.
15. The initial archwire can now be inserted (Fig 16).
(Fig 11a).
7. Wait 15 seconds and then rinse with a steady
stream of water for 15 seconds. Rinse with a
steady spray of water and air for another 30 seconds. Suction excess water and do not allow
saliva to come into contact with the etched
enamel (Fig 11b and 11c).
8. Replace cotton rolls and Dri-Angles; again, making sure that saliva does not contact the etched
enamel.
9. If the clinician chooses to use a moisture insensitive primer, such as Transbond MIP, on the
enamel surface for the indirect bonding procedure, then the air syringe should be used to
remove excess moisture. Complete desiccation
of the teeth is optional. A liberal coat of Transbond MIP should be painted onto the enamel
surface. Air dry for approximately 2 seconds.
Light curing of this primer is not necessary for
indirect bonding. If Transbond MIP moisture
insensitive primer is not used, and the bonding
is accomplished with the indirect bonding resin,
then all visible moisture should be removed. The
etched teeth should have a frosty appearance,
and be completely desiccated. If a frosty appear-~
RESULTS
This system has been used by thousands of clinicians internationally, and several thousand patients
have been treated. Communication with orthodontists who have used this system indicates that the
bonding is relatively consistent and efficient. Occasional bond failures do occur, of course, and are
usually related to contamination or improper technique. In those cases, it is a simple matter to section
the bonding tray, reapply the adhesive, and reseat
the brackets.
Bond strength tests have also proved the efficacy
of the resin. Bond strength compares favorably with
indirect bonding using Concise Enamel Bond (3M
Unitek) and Custom IQ (Reliance). Figure 17 (shown
on the web edition of the Journal at http://www.
quintpub.com) provides important bond strength
data. The indirect resin shows substantially greater
112
VOLUME 2, NUMBER 2, 2001
Sandhi I
Fig 11 (a) Enamel surfaces are etched with a gel etching material in preparation for bonding. (b,c) Enamel is rinsed
after removal of the etching gel. Note that the entire arch can be etched and dried to permit bonding of the complete dental arch.
Fig 12 (a,b) Dispensing wells are supplied with the indirect resin. Resin A is app)ied to the
tooth surface and should be placed in the well identified with the tooth icon. Resin B is
applied to the bracket base and should be placed in the well with the bracket icon. (c) Resin A
is applied to the etched tooth surface. (d) Resin B being applied to the bracket base.
Fig 13 (a) Placement of the bonding tray. (b) Maxillary and mandibular
bonding trays in place.
Fig 14 Removal of the outer shell
of the mandibular bonding tray. The
Biocryl layer will lift off easily if the
two layers were separated during
laboratory
preparation.
The soft
Bioplast layer is then remo,!ed.
113
.
Fig 15 (a) Lateral view of right buccal segments of the indirect bonded
appliance. (b) Anterior view of complete indirect bonded appliance. (c) Lateral view of the left buccal segments of the indirect bonded appliance. (d)
Maxillary occlusal view of the indirect bonded appliance. (e) Mandibular
occlusal view of the indirect bonded appliance.
Fig 16 Initial archwires engaged.
Note the control over second molar
positioning with the initial leveling
archwire.
ACKNOWLEDGMENT
bond strength immediately after curing than the
other resins, which is of critical importance during
tray removal and initial archwire insertion. Although
the final bond strength is not significantly different,
the clinical efficiency of this resin is enhanced by its
higher bond strength at the 5-minute level, since
that is when the indirect bonding tray would be
removed and the archwire inserted.
The step-by-step procedure outlined in this article originally
appeared in the April 1999 issue of the American Journal of
Orthodontics and Dentofacial Orthopedics.
REFERENCES
1.
CONCLUSION
2.
A new method for effective and efficient indirect bonding of orthodontic brackets has been presented. The
custom adhesive bases are easily formed with Transbond XT or APC brackets, and the indirect bonding is
accomplished using a resin developed specifically for
this purpose. Bond strength has proven to be excellent,
and this system for the indirect bonding of complete
dental arches, from second molar to second molar, has
been used in pediatric, adult, and orthognathic cases.
Bond strength tests have also proved the efficacy
of this resin.9 Although the eventual bond strength is
comparable to that of other resins, the clinical efficiency of this resin is greatly enhanced by the higher
bond strength developed within the first 2 minutes.
Tray removal is therefore possible within 2 minutes,
and archwire insertion can be immediate.
3.
4.
5.
6.
7.
8.
9.
114
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Scholz R. Indirect bonding revisited. J Clin Orthod 1983;17:
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Kasrovi P, Timmins S, Shen A. A new approach to indirect
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Kalange J. Ideal appliance placement with APC brackets and
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