Download Leveling effects of conventional and self

Case Report
Leveling effects of conventional and self-ligating brackets
－cases report
CHIA-TZE KAO
Institute of Oral Material Science and Orthodontic Department, College of Oral Medicine, Chung Shan Medical
University, Taichung, Taiwan, ROC.
Many kinds of self-ligating brackets (SLBs) have been introduced to the market. Manufacturers
claim that SLBs have many benefits, such as being fast, convenient, and frictionless. The aim of this
report was to compare the teeth leveling effects of a conventional bracket (CB) and various SLBs
combined with a copper-nickel-titanium wire. Each malocclusion case was bonded with 1 of the
following 4 types of bracket: an Ormco Damon III bracket, a Tomy Clippy bracket, a 3K composite
bracket, and a Unitek Clarity ceramic bracket. A 0.36mm (0.014-in) copper-nickel-titanium wire was
initially used in all cases. The observation period was 4 months, and photographs were taken at each visit
for treatment. At the end point of the observation time, the teeth of all patients which were initially
crowded, malaligned, or malpositioned teeth were well aligned, and similar treatment outcomes were
seen. We concluded that appliances with either the conventional or self-ligating brackets coupled with
copper-nickel-titanium wire can achieve good alignment and leveling of crowded, malaligned, and
malpositioned teeth in a relatively short interval of 12 weeks. （J Dent Sci, 2(2)：110-126, 2007）
Key words: self ligating bracket, leveling stage, conventional bracket.
In recent years as orthodontic materials have
improved, many hot appliances have been introduced
for clinical use. Hot appliances such as application of
thermal nickel-titanium (NiTi) or copper NiTi (with a
low load / deflection rate) and self-ligating brackets
(with low friction) are frequently used in routine
orthodontic therapy. All of these products emphasize
reductions in chair time and creation of high efficiency.
Therefore, orthodontists may be interested in whether
wires or brackets play important roles in orthodontic
treatment.
Self-ligating brackets were introduced in the
mid-1930s in the form of the Russell attachment,
which was intended to reduce ligation time and
improve operator efficiency1,2. Two types of selfligating brackets have been developed: an active form
Received: February 12, 2007
Accepted: April 20, 2007
Reprint requests to: Dr. Chia-Tze Kao, Orthodontic Department, College
of Oral Medicine, Chung Shan Medical University,
No. 110, Chien-Kuo North Road, Taichung, Taiwan
40201, ROC.
110
in which a wire is compressed in a bracket slot and a
passive form in which the wire is not compressed in
a bracket slot. There are many advantages with
self-ligating brackets. From the patient’s perspective,
self-ligating brackets are generally smoother, more
comfortable, and easier to clean because of the
absence of wire ligatures3. Several studies have
demonstrated a significant decrease in friction with
self-ligating brackets compared with conventional
bracket designs4-8. Reduced chair time is another
significant advantage9. However, one defect of
self-ligating brackets is the high cost. In addition, by
using these appliances, manufacturers claim that
orthodontists can increase patient appointment intervals and increase patient loads.
Stainless steel and cobalt-chromium alloys were
available in the 1940s and were extensively used in
orthodontics for many years. The introduction of NiTi
and multistranded stainless steel wires in the 1970s, of
titanium-molybdenum and superelastic NiTi in the
1980s, and of temperature-activated superelastic wires
in the 1990s has provided a wider range of choices.
The newest materials enable clinicians to use light
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continuous forces to move the teeth with less
discomfort to patients and less stress on the supporting
tissues.
Friction acts at the surface between 2 bodies
when 1 body slides or tends to slide in contact with
another body11,12. Friction in fixed orthodontic
appliance systems is recognized by most clinicians to
be very harmful to tooth movement13,14. Various factors
such as the archwire and bracket materials, their
sizes and shapes, the slot dimensions, the surface
composition, roughness, and cleanliness affect the
friction resistance process of orthodontic bracket-wire
combinations. Previous studies have shown that
bracket friction resistance levels from high to low
are in the order of conventional ceramic brackets,
conventional metal brackets, metal brackets, and
self-ligating brackets15. Wire friction resistance levels
from high to low are in the order of TMA wire, NiTi
wire, and stainless steel wire16,17.
An ideal archwire should be able to move teeth
with a light, continuous force. This force should be
designed to minimize patient discomfort, tissue
hyalinization, and root resorption. When a force is
applied, the archwire should maintain its elasticity
over a period of weeks to months. A light force
delivered at a constant level provides the optimal
condition for tooth movement. This can best be
achieved with wires that exhibit large elastic
deformations before breakage and thus have a large
working range.
An important consideration in selecting an
archwire for initial leveling in orthodontic treatment is
its stiffness, i.e., the force delivered per unit of
deactivation. Low-stiffness wires can be produced
using conventional NiTi because the modulus of
elasticity of NiTi is approximately 20% that of
stainless steel18. The orthodontic force must overcome
the frictional resistance (and the resistance of the
biologic milieu), and minimizing friction will result in
reduced levels of the required clinically applied force
to move the teeth.
The relationship between the bracket and wire is
intimate, and a force system is the outcome.
Determining how to create the best force system is a
critical aspect of the entire orthodontic process. To
achieve a high efficiency of orthodontic treatment, it
should be determined whether it is necessary to
change traditional brackets to new self-ligating
brackets in all orthodontic cases. The following
malocclusion cases were treated using different
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bracket types with wires which generate similar light
forces. The treatment results showed similar effects of
the leveling or alignment of malpositioned teeth.
CASE PRESENTATION
Case 1. A non-extraction case with a selfligating bracket
A 13-year-old male patient had a class III
malocclusion. The maxillary dentition showed a
blocking-in of the lateral incisors, canine supraversion,
and midline deviation, and the mandibular dentition
revealed minor incisor crowding. No tooth extraction
was performed in this case. The appliance used
consisted of a 0.022×0.028 inch slot Clippy metal
self-ligating bracket (Tomy, Tokyo, Japan) and 0.014inch Sentalloy wire (NiTi superelastic wire, Tomy)
(Figure 1A).
Progressive photographs of the frontal and buccal
views were taken during each visit at 4-week intervals.
The leveling of the teeth was complete by the third
visit (Figure 1B). Progressive photographs of the
occlusal view were also taken during each visit. On
the third visit, decrowding of the teeth had been
achieved (Figure 1C).
Case 2. An extraction case with a self-ligating
bracket
This 22-year-old female patient had a class I
malocclusion and an anterior openbite of 3 mm. The
maxillary dentition exhibited minor crowding of the
anterior teeth and a deep curve of Spee, and the
mandibular dentition demonstrated minor crowding of
the anterior teeth. The treatment plan for this case
included extraction of the 4 first premolars. The
appliance used consisted of a 0.022×0.028 inch slot
Clippy metal self-ligating bracket and a 0.014 inch
Sentalloy wire (Figure 2A).
Progressive photographs of the frontal and buccal
views were taken at each visit at 4-week intervals. On
the third visit, the alignment of teeth was complete,
and the amount of openbite had decreased (Figure 2B).
Progressive photographs of the occlusal view were
also taken during each visit. On the third visit, the
arch form had changed from square to rounded ovoid
(Figure 2C).
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C.T. Kao
Case 3. A non-extraction case with a selfligating bracket
Case 5. A non-extraction case with a composite
metal slot bracket treatment
This 23-year-old female patient had a class III
malocclusion. The occlusion of the dentition showed
blocking-in of the right upper lateral incisor, a midline
shift to the right, an anterior crossbite, and minor
crowding of the lower teeth. No tooth extraction was
performed in this case. The appliance used consisted
of a 0.022 × 0.028 inch slot Damon III metal
self-ligating bracket (Ormco, Glandora, CA, USA)
and a 0.014 inch copper NiTi wire (Ormco) (Figure
3A).
Progressive photographs of the frontal and
buccal views were taken during each visit at 4-week
intervals. The right upper lateral incisor did not bond
with the bracket until the third visit. At that stage, the
anterior crossbite was corrected, and the midline
showed a little shift (Figure 3B).
On the sixth visit, the blocked-in right upper
lateral incisor had been pulled out and was aligned
in the correct position (Figure 3C). Progressive
photographs of the occlusal view were also taken at
each visit. On the third visit, the lower arch alignment
was complete, but the right upper lateral incisor was
still in a blocked-in position (Figure 3D). The lower
arch alignment was the same as that of the third visit,
but the right upper lateral incisor had been pulled out
at the sixth visit (Figure 3E).
This 21-year-old female patient had a class I
malocclusion. The maxillary incisors were rotated and
mandibular incisors were crowded. No tooth
extraction was performed in this case. The appliance
used consisted of a 0.022×0.028 inch slot composite
metal slot bracket (3K Dentsply, New York, NY, USA)
and a 0.014 inch Sentalloy wire (Figure 5A).
Progressive photographs of the frontal and buccal
views were taken at each visit at 4-week intervals. In
the frontal view, the crowding of the lower incisors
had been relieved by the third visit, and the gingival
recession had been auto-corrected (Figure 5B).
Progressive photographs of the occlusal view
were also taken at each visit. On the third visit, both
the maxillary and mandible arch alignments were
good (Figure 5C).
Case 4. An extraction case with a self-ligating
bracket
This 21-year-old female patient had a class I
malocclusion. The right and left maxillary lateral
incisors were blocked-in. Both maxillary and mandibular arches showed tooth crowding with a deep
curve of Spee. Four first premolars were extracted.
The appliance used consisted of a 0.022×0.028 inch
slot Damon III metal self-ligating bracket and 0.014
inch copper NiTi wire. On the third visit, the
blocked-in lateral incisors had been pulled out, and the
tooth alignment was complete (Figure 4A).
Progressive photographs of the occlusal view
were taken at each visit. On the third visit, the
maxillary arch form had changed from a V shape to a
rounded ovoid one, and the transverse width of the
premolar area had increased. By the third visit, the
tooth crowding was relieved (Figure 4B).
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Case 6. An extraction case with composite
metal slot bracket treatment
This 25-year-old female patient had a class III
malocclusion. The maxillary dentition showed an
anterior crossbite with blocking-in of the lateral
incisors and a midline deviation. The left maxillary
first premolar and the right and left mandibular
first premolars were extracted. The appliance used
consisted of a 0.022 × 0.028 inch slot composite
metal slot bracket and a 0.014-inch Sentalloy wire
(Figure 6A).
Progressive photographs of the frontal and buccal
views were taken at each visit at 4-week intervals. In
the frontal view, the blocked-in upper lateral incisors
had been pulled out. In the buccal view, the
canine had been pulled down to the occlusal plane.
The anterior teeth had achieved an edge-to-edge
relationship(Figure 6B). Progressive photographs of
the occlusal view were also taken at each visit. On the
third visit, the maxillary arch form exhibited good
alignment, and the extraction space had been reduced
(Figure 6C).
Case 7. A non-extraction case with ceramic
metal slot bracket treatment
This 23-year-old female patient had a class I
malocclusion. The right maxillary central and lateral
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incisors exhibited a crossbite with minor crowding.
The patient asked for alignment and leveling of the
maxillary teeth only. No tooth was extracted. The
appliance used consisted of a 0.022×0.028 inch slot
ceramic metal slot bracket (Clarity, 3M Unitek,
Monrovia, CA, USA) and a 0.014-inch Sentalloy wire
(Figure 7A).
Progressive photographs of the frontal and buccal
views were taken at each visit at 4-week intervals. On
the first visit, the right maxillary central and lateral
incisors were well aligned. The teeth alignment
was improving through the third visit (Figure 7B).
Progressive photographs of the occlusal view were
also taken at each visit. By the third visit, the arch
form had changed to a more-rounded ovoid shape
(Figure 7C).
Case 8. An extraction case with ceramic metal
slot bracket treatment
This 25-year-old female patient had class I
malocclusion. The maxillary lateral incisors were
blocked-out, and the central incisors showed a
lingual tip. No tooth extraction was done in this case.
The appliance used consisted of a 0.022×0.028 inch
slot ceramic metal slot bracket and a 0.014 inch
Sentalloy wire (Figure 8A).
Progressive photographs of the frontal, buccal,
and occlusal views were taken at each visit at 4-week
intervals. On the third visit, the maxillary incisors
were well aligned, but the buccal occlusion was a little
disoriented. On the occlusal view, the arch form had
changed to a more-rounded shape (Figure 8B).
DISCUSSION
Many factors can influence orthodontic frictional
resistance, including the relative resistance between
the bracket and wire, the archwire size, the archwire
section, the torque at the bracket wire interface, the
surface condition of the archwire and bracket slot, and
the type and force of the liagtion19-21. Friction force is
known to be an important factor that might affect the
treatment efficiency.
It is more common to use the self-ligating
bracket in the clinic because many manufacturers
offer different types of self-ligating brackets.
According to the manufacturer’s description of the
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self-ligating bracket, elimination of the ligatures
reduces friction and allows for better sliding
mechanics22. These reports support a view of clinically
significant improvements in treatment efficiency when
using passive self-ligating brackets22. In Eberting’s
study22, it is not clear as to what kinds of technique
were used or which variables were controlled.
However, in the present reported 8 cases, one can
observe that the treatment time did not decrease in the
initial stage of treatment when using the self-ligating
brackets. Appliances with either conventional or
self-ligating brackets can achieve good alignment of
the teeth after 4 months of treatment. On the contrary,
different wires might have different efficiencies for
teeth movement.
Miles’s study showed that the Smart Clip bracket
was not more effective at reducing irregularities
during the initial stage of treatment than a conventional bracket ligated with elastomeric modules or
stainless steel ligatures23. This result is comparable
with the results from the present case reports. The
efficiencies of self-ligating brackets need to be
surveyed or studied in an evidence-based clinical
study.
One may question whether the high efficiency of
tooth movement that is time-saving and exists with
self-ligating brackets occurs in the space closure stage.
Unfortunately, there is a lack of clinical data to
demonstrate this. However, different extraction rates
may simply reflect different approaches to treatment.
Eberting showed that the treatment time was not
reduced when using a Damon self-ligating bracket22.
This supports the concept that the reduction in
treatment time may be due to a change to moreefficient treatment systems rather than solely to the
choice of a bracket. The orthodontist’s concepts still
play a most important role in tooth movement.
Although this is not a clinical study, the treatment
outcomes of our 8 cases showed that all crowded,
malaligned, and malpositioned teeth could be well
aligned or leveled in a relatively short interval of 12
weeks. Although the frictional resistance of the
self-ligating bracket is lower than that of the
traditional bracket, no significant difference in the
clinical outcomes was found when using either type of
bracket. The teeth movement efficiency was also
similar. It is also believed that the wire creating a light
force should be used when performing tooth
movement.
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C.T. Kao
Figure 1. Case 1, a non-extraction case with a self-ligating bracket.
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Fig. 1C.
Figure 1.（continued）
Figure 2. Case 2, an extraction case with a self-ligating bracket.
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C.T. Kao
Fig. 2C.
Figure 2. （continued）
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Fig. 3A.
Figure 3. Case 3, a non-extraction case with a self-ligating bracket.
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C.T. Kao
Fig. 3D.
Figure 3. （continued）
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Fig. 3E.
Figure 3. （continued）
Figure 4. Case 4, an extraction case with a self-ligating bracket.
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C.T. Kao
Figure 4. （continued）
Figure 5.
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Case 5, a non-extraction case with composite metal slot bracket treatment.
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Figure 5. （continued）
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C.T. Kao
Fig. 6A.
Figure 6. Case 6, an extraction case with composite metal slot bracket treatment.
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Fig. 6C.
Figure 6. （continued）
Figure 7. Case 7, a non-extraction case with ceramic metal slot bracket treatment.
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C.T. Kao
Figure 7. （continued）
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Figure 8.
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Case 8, an extraction case with ceramic metal slot bracket treatment.
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C.T. Kao
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