Download Practical Techniques for Achieving Improved Accuracy in Bracket

Practical Techniques for Achieving
Improved Accuracy in Bracket Positioning
by Richard P. McLaughlin, D.D.S., John C. Bennett, D.D.S., and Hugo Trevisi, D.D.S.
Orthodontic Perspectives, Vol. VI, No. 1, 1999.
Dr. Richard McLaughlin, San Diego, California
Dr. Richard McLaughlin completed his orthodontic training at the University of Southern California in 1976. Since then he has been in the full
time practice of orthodontics in San Diego, California. Dr. McLaughlin has lectured extensively on the pre-adjusted appliance in the United
States, Europe, South America, Asia and Australia with orthodontic colleagues from London, England, Dr. John Bennett, and from São Paulo,
Brazil, Dr. Hugo Trevisi. He is a member of the Pacific Coast Society of Orthodontists, the American Association of Orthodontists, a Diplomate
of the American Board of Orthodontics and a full member of the Edward H. Angle Society. In addition, Dr. McLaughlin is an associate clinical
professor at the University of Southern California, Department of Orthodontics.
Dr. John Bennett, London, England
Dr. John Bennett completed his orthodontic training at the Eastman Dental Institute in London, England in 1972. Since that time he has been in
the full time practice of orthodontics in London, England. For the past 20 years he has worked exclusively with the pre-adjusted appliance
system, and with Dr. McLaughlin has held a particular interest in evaluating and refining effective treatment mechanics utilizing light forces.
These concepts have developed and have included the more recent contribution from Dr. Trevisi. Their well tried and effective treatment
approach has seen widespread acceptance. Dr. Bennett has lectured internationally on the pre-adjusted appliance for a number of years.
Together with Dr. McLaughlin he has published numerous articles and has co-authored two orthodontic textbooks, both of which have been
well received. He is currently a part-time clinical instructor at the post-graduate orthodontic program at Bristol University in England.
Dr. Hugo Trevisi, São Paulo, Brazil
Dr. Hugo Trevisi received his dental degree in 1974 at Lins College of Dentistry in the state of São Paulo, Brazil. He received his orthodontic
training from 1979 to 1983 at that same college. Since that time he has been involved in the full time practice of orthodontics in Presidente
Prudente, Brazil. He is a Faculty Member at the University of Odontology and Dentistry in Presidente Prudente. He has lectured extensively in
South America and Portugal and has developed his own orthodontic teaching facility in Presidente Prudente. Dr. Trevisi has 20 years of
experience with the pre-adjusted appliance. He is a member of the Brazilian Society of Orthodontics and the Brazilian College of Orthodontics.
Accuracy of bracket positioning is essential, so that the builtin features of the bracket system can be fully and efficiently
expressed. This helps treatment mechanics and improves
the consistency of the results. The authors use the following
techniques, and recommend them.
incisor teeth from the side, or from above or below. This will
require the patient to turn the head, and the orthodontist to
change seating position from time to time (Fig. 1).
Bonding and Banding Technique
The use of light-cured systems for bonding brackets and cementing
bands is helpful. Light-cured systems avoid time pressure on the
orthodontist when setting up cases. The bonding materials should
be carefully used exactly to the maker’s recommendations, with
plenty of good quality light. This will reduce breakages. Errors
can be introduced when replacing loose brackets. The bonding
agent should be thick enough to prevent floating of the brackets
during positioning.
Bracketing and banding should always be performed by the
orthodontist. Setting up of the case is the most important aspect
of the treatment, after correct diagnosis and treatment planning.
Banding and bonding should therefore not be delegated. When
bonding brackets, if possible it is helpful to avoid viewing the
Figure 1:
When placing brackets it is important to view the teeth from the
correct aspect.
The Use of Gauges
Vertical accuracy can be greatly improved by the use of gauges
and a bracket positioning chart (Fig. 2a,b). This will deal
with difficulties such as tooth length discrepancies, labially
and lingually displaced roots, partly erupted teeth, and gingival
hyperplasia. The technique has previously been reported (ref. 1, 2).
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Figure 4b:
Parallel placement on UL Cuspid.
Figure 2a:
Recommended bracket positioning chart.
Figure 4c:
Lower bicuspid placement.
Figure 5a:
In the molar region the gauge is placed parallel with the occlusal
surface of each individual molar.
Figure 2b:
Bracket positioning gauges.
The bracket placement gauges are used in slightly different ways
in different areas of the mouth. In the incisor regions the gauge
is placed at 90° to the labial surface (Fig. 3). In the canine and
premolar regions the gauge is placed parallel with the occlusal
plane (Fig. 4a, 4b, 4c). In the molar region the gauge is placed
parallel with the occlusal surface of each individual molar (Fig.
5a, 5b, 5c).
Figure 5b:
Molar attachment positioned parallel to occlusal surface.
Figure 3:
In the incisor region, the gauge is placed at 90° to the labial surface.
Figure 5c:
Parallel gauge placement to molar’s occlusal surface.
Figure 4a:
In the canine and premolar regions the gauge is placed parallel with
the occlusal plane.
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Modified Bracket Placement Charts
If the treatment plan involves extraction of four first or second
premolars, a modified bracket positioning chart may be used
(Fig. 6). This will ensure good vertical relationships between the
marginal ridges of canines and second premolars.
For example, if a central incisor has a 0.5mm chip at the start
of treatment, the bracket may be placed 0.5mm more gingivally
than shown on the bracket positioning chart. Enamel shaping can
then be carried out later in the treatment, leaving good coordination of incisal edges (Fig. 8).
Figure 8:
If a central incisor has a 0.5mm chip at the start of treatment, the
bracket may be placed 0.5mm more gingivally than shown on the
bracket positioning chart.
If upper canines are very pointed, and it is planned to re-shape
the teeth later by 1mm, it is correct to anticipate this, and position
the brackets 1mm more gingivally than shown on the bracket
positioning chart (Fig. 9).
Figure 6
Figure 9:
If upper canines are very pointed it is often helpful to position the brackets 1mm more gingivally than shown on the bracket positioning chart.
If the treatment plan involves extraction of four first molars,
a modified bracket positioning chart may be used as shown in
figure 7. This will help to achieve good vertical relationships
between the marginal ridges of second premolars and second
molars. Second molar bands and tubes are used for the second
molars, even though they will occupy the first molar positions.
Rotations
Slight roto bonding is helpful when bracketing rotated incisors.
On a rotated tooth the bracket can be bonded slightly more mesially or distally, sometimes with a very small amount of excess
composite under the mesial or distal of the bracket base (Fig.
10, 11a, 11b). In this way full correction of the rotation can be
achieved with no special measures. Also, viewing canines, premolars, molars, and rotated incisors occlusally or incisally with
a mouth mirror helps bracket positioning relative to the vertical
long axis of the crown.
Figure 10:
On a rotated tooth the bracket can be bonded slightly more mesially or distally, and in this way full correction of the rotation can be
achieved.
Figure 7
If the patient demonstrates a deep anterior overbite, the brackets
on the upper and lower centrals, laterals and cuspids can be placed
0.5mm more occlusal to assist in bite opening. Conversely, if the
patient demonstrates an anterior open bite, these brackets can be
placed 0.5mm more gingival to assist in bite closure.
Chipped or Worn Teeth
It is advisable to make adjustments for chipped or worn teeth, or
those with unusual anatomy, at the time of bonding and banding.
The use of gauges and a bracket positioning chart will not deal
with chipped or worn teeth, or teeth of abnormal anatomy, such
as pointed canines.
Figure 11a:
A clinical example of roto bonding. Full correction of rotations can
be achieved during the early stages of treatment, without any other
special measures. Also see Figure 11b.
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Figure 14:
A lower second molar band and tube can be used on the first molar if
the bite is close.
If the treatment plan involves extraction of upper premolars only,
the upper first molar band should be seated a little more gingivally on the mesial. This will help tooth fit with a class II molar
relationship (Fig. 15).
Figure 11b
Special Care With Molars
Special attention is needed in the relationship between the lower
first molar and the lower second premolar. This is the most difficult relationship in orthodontics. Special attention is needed to
carefully place the lower second bicuspid bracket, because it is
well back, and prone to contamination with saliva. A common
mistake is to seat the mesial of the molar band too low, and this
should be avoided (Fig. 12a, 12b).
Normal band position
Adjusted band position
Figure 15:
If the treatment plan involves extraction of upper premolars only,
the upper first molar band should be seated a little more gingivally
on the mesial.
Re-positioning
Any positioning errors should be corrected before moving into
wires heavier than .014 steel or .019 x .025 Nitinol Heat-Activated
Wire. Re-aligning can then be done, before going into heavier wires.
Figure 12a:
The mesial of the lower first molar band should not be seated too
low. This is a common error.
When working with small clinical crowns, either due to partial
eruption, or gingival hyperplasia, stepping of .014 round wires is
helpful. The tooth can be bracketed with the bracket too incisal.
At the .014 round steel stage the crown length can be increased
by stepping the wires. At the next visit the tooth can be bracketed
correctly and a larger wire inserted. In this way, treatment time
can be reduced (Fig. 16).
Figure 12b:
Parallel seating of the band’s occlusal surface.
Figure 16:
Stepping of .014 round wires can be helpful when working with small
clinical crowns, either due to partial eruption or gingival hyperplasia.
Care is needed to avoid positioning the lower first molar band
with the bracket too mesially. It should straddle the buccal
groove (Fig. 13).
There is also an opportunity to replace any wrongly positioned
brackets when banding or bracketing newly erupted teeth,
because normally it will be necessary to go back to light aligning wires. Also, if a patient comes in with a loose bracket which
needs rebonding, it is worth checking the position of all other
brackets. This is an opportunity to correct errors elsewhere.
The authors take time and care to try to achieve accurate bracket
positioning at the set-up appointment. During treatment bracket
positions are monitored and reviewed at adjustment visits. Using
the techniques described and recommended in this article it is
possible, in most cases, to avoid the need to change bracket positions in the later stages of treatment. This improves the efficiency
of the treatment and the quality of the results. n
Figure 13:
The lower molar tube should straddle the buccal groove, mesio-distally.
If there is a close bite on the lower first molars, the molar bracket
should be at the correct height, as recommended in the bracket
placement chart. It should not be positioned more gingivally. A
lower second molar band and tube can be used in this situation, as
part of the versatility of the MBT™ Appliance System (Fig. 14).
Also, temporary bonding material on the occlusal of the molars,
or an acrylic bite plate can be used to avoid bracket interferences.
ReferenceS
1 J. Bennett, R. P. McLaughlin: “Bracketplazierung und Straightwire-Apparatur”
Informationen aus Orthodontie & Kieferorthopädie 4 Quartal 1995 : 447-462.
2J. Bennett, R. P. McLaughlin: “Orthodontic Management of the Dentition with the
Preadjusted Appliance,” ISBN 1 899066 Isis Medical Media 1997.
Reprinted from Orthodontic Perspectives Vol. VI No. 1.
© 1999, 3M. All rights reserved.
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