Lower molar uprighting with miniscrew anchorage: direct and indirect anchorage

Article (PDF Available)inInternational journal of orthodontics (Milwaukee, Wis.) 24(3):9-14 · December 2013with 907 Reads
Source: PubMed
Abstract
Lower molar uprighting has been increasingly indicated in clinical orthodontics, mainly because of adult patients with rehabilitation needs. The aim of this study was to determine the success rate of miniscrew use for lower molar uprighting and to compare the use of direct and indirect anchorage. One hundred and eighty-one miniscrews were inserted in 102 rehabilitation patients, with a mean age of 42.24 years. In 71 patients, indirect anchorage was used (116 miniscrews); in the other 31 patients, direct anchorage was employed (65 miniscrews). The choice of direct or indirect anchorage was determined by the orthodontist according to the force system that would be used for the movement and the bone availability. The overall success rate for miniscrews was 90. 05%; 18 miniscrews failed, including 15 that were used as indirect anchorage and 3 that were used as direct anchorage. Considering the results of this study, it can be concluded that both direct and indirect anchorage can be successfully used for molar uprighting.
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IJO VOL. 24 NO. 3 FALL 2013
Lower Molar Uprighting with Miniscrew Anchorage: Direct
and Indirect Anchorage
By Ana Cláudia Moreira Melo, PhD; Ricarda Duarte da Silva, MDS; Roberto Hideo Shimizu, PhD; Dolores
Campos, DDS; Augusto Ricardo Andrighetto, PhD
Abstract: Lower molar uprighting has been increasingly indicated in orthodontics clinics, mainly because of adult patients with
rehabilitation needs. The aim of this study was to determine the success rate of miniscrew use for lower molar uprighting and to compare the
use of direct and indirect anchorage. One hundred and eighty-one miniscrews were inserted in 102 rehabilitation patients, mean age 42.24
years. In 71 patients, indirect anchorage was used (116 miniscrews); in the other 31 patients, direct anchorage was employed (65 miniscrews).
The choice of direct or indirect anchorage was determined by the orthodontist according to the force system that would be used for the
movement and the bone availability. The overall success rate for miniscrews was 90.05%; 18 miniscrews failed, including 15 that were used
as indirect anchorage and 3 that were used as direct anchorage. Considering the results of this study, it can be concluded that both direct and
indirect anchorage can be successfully used for molar uprighting.
Keywords: Orthodontics, anchorage; miniscrew.
F E A T U R E This article has been peer reviewed
ntroduction
Various problems including bone defects on the
mesial face of the molars, lack of a suitable site for
implant positioning, distal movement of premolars,
upper molar extrusion, occlusal interferences in lateral and
protrusive movements, and problems with prosthesis adaptation,
can be associated to the need of mesial tipping of lower molars.1
These teeth can present variable degrees of inclination,2 directly
influencing the type of movement required to correcting their
position in all three planes of space, including the need of
opening or closing spaces.3-6
Whatever mechanic is used, an important point to be
considered is the stabilization of the reactive unit (anterior
segment) as an anchorage unit. The Orthodontic clinic presents
many possibilities for anchorage control. In particular the skeletal
anchorage technique has the potential to minimize the risks of
adverse movements at the anchorage unit.7
Numerous studies have reported the success rates of miniscrews
used as orthodontic anchorage. Luzi et al.,8 in 2007, found
9.3% failure and 6.4% partial failure in 140 immediately loaded
miniscrews. In the same year, Kuroda et al.9 reported success
rates of 88.6% for the use of miniscrews and 86.8% for the use of
miniplates. In this study the miniscrews were loaded up to 12 weeks
after implantation. Very similar results were observed by Moon et
al.,10 in 2008, in a study that registered a success rate of 83.8% for
miniscrews inserted in 209 patients and by Viwattanatipa et al.,11
in 2009, who reported 85% success after 6 months of observation.
However the latter authors observed an increase in the failure rate
to 57% one year after miniscrew insertion. In a retrospective
evaluation of 378 miniscrews inserted from 2001 to 2003, Lim
et al.12 (2009) reported an overall success rate of 83.6%. Another
study reporting retrospective data on the use of miniscrews over a
five-year experience with miniscrews13 indicated a very high overall
success rate of 93.43%.
Factors associated with miniscrew failure have been identified
as reduced diameter of screws (1.0 mm or less),14 inflammation,11,14
high mandibular plane angle,14 sex15 and the presence of
nonkeratinized mucosa.11,16 Some authors consider the posterior
mandible to be an area of risk for miniscrew failure.10,16
Considering the potential higher risk of failure when used on
the posterior area of the mandible (between first and second molars
or in the retromolar area), we carried out a comparative study of
the use of miniscrews as anchorage for molar uprighting inserted
in more anterior areas, either as a direct or an indirect system.
Materials and Methods
One hundred and eighty-one miniscrews were inserted in
102 patients, mean age of 42.24 years. The sample consisted of
rehabilitation patients who needed minor orthodontic movements
for implant and/or prosthesis insertion. All the patients were
treated at the Latin American Institute of Dental Research and
Education (Curitiba, Brazil). The study was approved by the Ethical
Committee of Pontifícia Universidade Católica (PUC-PR).
The used mechanics consisted of:
Direct anchorage:
In direct anchorage the force was applied directly from the
miniscrew to the molar to be uprighted. Two options of orthodontic
mechanics were proposed according to the type of movement
indicated: uprighting with or without intrusion.
When intrusion was indicated, two miniscrews were vertically
positioned on the alveolar crest area (Figure 1A) and a bracket
26 IJO VOL. 24 NO. 3 FALL 2013
was bonded on a resin uniting the two miniscrews (Figure 1B). A
segment of .017 x .025” TMA wire from this bracket to the molar
tube was activated in order to result in uprighting spring (Figure
1C) or a .017 x .025” stainless steel segment of wire with an
uprighting spring (Figure 2). The reason for using two miniscrews
is to increase stability avoiding that the counterside effect of the
force applied results in miniscrew failure.
Another option of direct anchorage included the use of a
cantilever direct activated on the miniscrew. The cantilever consists
in a piece of wire with one end inserted into the tube of the molar
and the other end is tied to the miniscrew. The system of force
consists in an extrusion force and a moment of force in the molar
and an intrusion force in the anterior area (Figures 3 and 4). The
cantilever was confectioned in TMA .017 x .025”.
Indirect anchorage:
For indirect anchorage, a segment of .019 x .025” stainless
steel wire was positioned on the miniscrew neck and inserted into
brackets bonded at the cuspid and the premolars (Figure 5). The
miniscrew and the wire were considered the anchorage unit (reactive
unit).
The uprighting force was obtained using a cantilever (TMA
.017 x .025”). Consisting of a piece of wire with one end inserted
into the tube of the molar; the other end of the wire was applied
to the reactive unit at a single point of contact (Figure 6 and 7).
In situations in which both intrusion and uprighting of the molar
were necessary, a two-cantilever mechanic was applied. In this case
there was a second cantilever inserted on a criss-cross tube inserted
between the first and second premolars and tied to the molar tube
activated to exert an intrusion force (Figures 8 and 9).
The planning of the implantation site and type of anchorage
was determined by the orthodontist according to bone availability
and the force system that would be used for the movement. The
miniscrews were conical in shape with 7, 9 or 11 mm in length,
1.3 or 1.6 mm in diameter (Neodent®, Curitiba, Brazil). They were
inserted either by surgeons or by orthodontists and in the great
majority of the cases immediate loading was employed.
In cases in which one molar was uprighted, a moment of force
of 800g.mm was used; for two-molar uprighting, the force used
was 1200g.mm3.
Figure 2: Clinical example of two miniscrew mechanics for direct anchorage. A. Lateral initial view showing inclined
molar. B. Occlusal initial view. C. Two miniscrews and an uprighting spring. D. Occlusal view after opening space. E.
Lateral view after rehabilitation with dental implants.
Figure 1: Direct anchorage. A. Two miniscrews inserted on the alveolar crest. B. Bracket bonded. C. .017 x .025” TMA
spring activated.
AC
B
D E
B CA
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IJO VOL. 24 NO. 3 FALL 2013
The criterion for success was the absence of clinical mobility until the movement
was finished (sufficient space for implants and/or prosthesis rehabilitation). Treatment
time varied from 3 to 10 months.
Results
The demographic distribution of direct and indirect anchorage and specific
mechanics are described in tables I, II and III.
In the present study the overall success rate of miniscrews was 90.05% (18
miniscrews failed); 87.06% of the miniscrews used as indirect anchorage and
95.38% of them used as direct anchorage succeeded. One miniscrew that was to be
used as direct anchorage fractured during insertion and another one was re-installed
immediately (Table IV).
Direct anchorage (Table III) was obtained using cantilevers (15 miniscrews) or by an
uprighting spring stabilized on two miniscrews (50 miniscrews). Indirect anchorage
(Table II) was chosen, either single-cantilever (27 miniscrews) or two-cantilever
system (89 miniscrews).
Direct anchorage resulted were 90.47% success in miniscrews placed
perpendicular to the buccal face of the alveolar bone (with a cantilever). The highest
success value, 97.72%, was observed when two screws were vertically positioned on
the alveolar crest (with an uprighting spring) (Table IV). Only one miniscrew failed
when used on the alveolar crest because it was fractured during insertion.
Figure 3: Direct anchorage - cantilever.
A. Activation. B. Uprighting mechanics.
B
A
Figure 4: Clinical example of molar
uprighting with direct anchorage
associated to a cantilever. A. Initial
view. B. Cantilever tied directly to the
miniscrew. C. Occlusal view showing the
molar uprighted and sufcient space for
rehabilitation. D. Final view after dental
implant rehabilitation.
B
A
D
C
Figure 5: Indirect anchorage – Reactive unit.
Figure 6: Indirect anchorage – Cantilever. A. Activation. B. Uprighting
mechanics.
B
A
28 IJO VOL. 24 NO. 3 FALL 2013
B
A
D
C
E
Figure 7: Clinical example of molar uprighting
with indirect anchorage associated to a
cantilever. A. Cast model showing molar
inclined and no space for rehabilitation. B.
Initial panoramic X-ray. C. Indirect anchorage
with a miniscrew and single cantilever for molar
uprighting. D. Implant supported rehabilitation
of the edentulous space. E. Final panoramic
X-ray.
Figure 9: Clinical example of molar uprighting with indirect
anchorage associated to a two-cantilever mechanics. A. Cast
model showing molar inclined and extruded. B. Two-cantilever
mechanics. C. Periapical X-ray showing dental implant inserted in
the edentulous space. D. Final view after rehabilitation.
Figure 8: Indirect anchorage – Two-Cantilever. A. Activation. B.
Uprighting mechanics.
BA
B
A
DC
Indirect anchorage, with the use of single or double cantilevers presented
87.06% success (Table IV). In this case all miniscrews were positioned
perpendicular to the buccal face of the alveolar bone.
When considering gender, direct anchorage in males resulted in 95.23%
of success and in females 95.45% while indirect anchorage showed 87.17%
of success in males and 87.01 in females.
Discussion
Many authors8-14,16 have measured the success rates of miniscrews used as
orthodontic anchorage varying from 57% to 93%. When evaluating the failure
risk of miniscrews, factors such as inflammation, soft tissue thickness and the
presence of keratinized or non-keratinized tissue were considered.10,11,14,16
The retromolar area is frequently considered for miniscrew placement
when molar uprighting is indicated, however, considering soft tissue thickness
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IJO VOL. 24 NO. 3 FALL 2013
Table I: Sample characteristics.
Type of anchorage Patients Miniscrews % (miniscrews)
Direct 31 65 35.91
Indirect 71 116 64.08
Total 102 181 100
Table II: Indirect anchorage data.
Indirect anchorage Patients Miniscrews % (miniscrews)
Single Cantilever 23 27 23.27
Two-cantilever 48 89 76.72
Total 71 116 100
Table III: Direct anchorage data.
Direct anchorage Patients Miniscrews % (miniscrews)
Single Cantilever 10 21 32.30
Spring 21 44 67.69
Total 31 65 100
Table IV: Success rates of the installed miniscrews.
Direct Anchorage Indirect Anchorage
Miniscrews
(Success)
Success
rate
Miniscrews
(Success)
Success
rate
Sex Male 20/21 95.23 34/39 87.17
Female 42/44 95.45 67/77 87.01
Area Buccal 19/21 90.47 101/116 87.06
Alveolar
ridge 43/44 97.72 ---------- ----------
and difficulties with respect to patient hygiene,
alternative sites should be considered. The aim
of the present study was to determine the success
rate of miniscrews used specifically for lower
molar uprighting using alternative mechanics
to avoid the positioning of miniscrews in areas
considered more prone to failure.
Our results showed that, the use of direct
anchorage produced excellent results, both
when the miniscrews were placed perpendicular
to the buccal face of the alveolar bone (90.47%
success) and when they were vertically positioned
on the alveolar crest (97.72% success). Only one
miniscrew failed when used on the alveolar crest,
in that instance, because it was fractured during
insertion. The reason for the maintenance of
stability of the vertically inserted miniscrews
is probably related to the fact of that the
two implants were united, so there were no
micromovements that would interfere with the
stability of the fixations.
We also tested the use of cantilevers as direct
anchorage, with 90.47% success, and as indirect
anchorage, with 87.06% success. Cantilevers
are excellent devices for molar uprighting
because they are statically determinate systems,
meaning that the force system they produce
presents a high degree of constancy during
deactivation.17
According to Romeo and Burstone 3
(1977), the magnitude of the moment required
to upright a molar has been suggested to be
800g.mm, while the adequate extrusion force
generated at the system should not be over
than 30 gf, to maintain a constant relationship
between the alveolar bone crest and the
enamel-cement junction.4 In cases in which the
extrusion of the molar was counter-indicated,
we decided on the use of a two-cantilever
system that can only be achieved with indirect
anchorage.
The choice of mechanics to be used in molar
uprighting depends on many parameters,
including the anatomical characteristics of the
area and the facial pattern of the patient. In cases
in which there is sufficient bone availability, the
use of two united miniscrews is a very stable
option. However, it should be observed that in
such cases, the miniscrews should be positioned
with the aid of a surgical counter, and the heads
of the miniscrews must be close to one another.
Cantilevers also proved to be adequate options,
and can be used as direct or indirect anchorage,
depending on the need for molar intrusion.
Conclusion
Considering the results of this study, it
can be concluded that both direct and indirect
anchorage can be successfully used for molar uprighting. However, a study with a
greater sample size is indicated.
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  • Anchorage control is important for efficient orthodontic treatment with fixed appliances. Successful osseointegration encouraged many orthodontists to use dental implants as stationary anchorage units for force application. However, their use has some drawbacks, which led to the development of miniscrew implants (MIs). Our aim was to investigate factors significantly contributing to the success rates of MIs in various orthodontic treatment procedures in white patients. In total, 350 self-tapping (187 Abso Anchor [Dentos, Daegu, South Korea] and 163 Ortho Easy Pin [Forestadent, Pforzheim, Germany]) MIs used to reinforce orthodontic anchorage and placed in 130 consecutively chosen patients were assessed retrospectively. Clinical variables possibly influencing the success rates of MIs were categorized into patient-related, implant-related, location-related, and orthodontic-related. Statistical evaluation included descriptive statistics and survival analysis. The survival curves of the MIs with respect to the various factors were estimated and plotted by using the Kaplan-Meier product-limit estimate. The MI survival distributions for each factor were compared with the log rank test for simple comparisons or the Cox regression for multiple variables. The overall success rates of MIs that remained stable during a mean treatment time of 19.2 +/- 2.3 months was 93.43%; this was considerably higher than in previous reports. Only a few factors were found to be associated with statistically significant higher success rates of MIs, including deep bites, placement in the attached gingiva of the maxilla, and en-masse distalization of teeth. The success rates of MIs in white patients were greater than the corresponding rates reported for Asian patients. Our results confirm the effectiveness of orthodontic MIs as temporary anchorage reinforcement devices and suggest various clinical factors as potential causes of failure.
  • Article
    Diagnosis and treatment in molar uprighting are discussed. The over-all objective in molar uprighting is ideal positioning of the molar which will eventually become an abutment tooth for a fixed prosthesis. The ideal position will provide an optimal periodontal environment for the molar(s). The specific objectives concerning protection against inflammatory periodontal diseases and occlusal traumatism, which together determine the optimal periodontal environment, are explained. Emphasis is placed on the biomechanics of molar uprighting which will achieve the desired periodontal treatment result. The specific technique recommended for the instances in which the molar is considerably angulated involves a segmental approach which utilizes a modification of the Burstone root spring. Proper application results in the dissociation of the correction of angulation and the extrusion of the molar tooth. When extrusion of the periodontally involved molar is required, then it should follow the correction of molar angulation. Other advantages of this approach involve the precision and ease of symmetrical preactivation, favorable load/deflection considerations, the low level of patient discomfort, and the reduced tendency of normal function distorting or dislodging the spring. This technique is compared by these parameters to other popular molar-uprighting techniques. It is recognized that a multidisciplinary approach to this type of dental therapy is ideal and that since treatment planning in individual cases varies greatly, each malocclusion and associated periodontal involvement should be evaluated on an individual case basis.
  • Article
    Recently, implant anchors such as titanium screws have been used for absolute anchorage during edgewise treatment. However, there have been few human studies reporting on the stability of implant anchors placed in the posterior region. The purpose of this study was to examine the success rates and to find the factors associated with the stability of titanium screws placed into the buccal alveolar bone of the posterior region. Fifty-one patients with malocclusions, 134 titanium screws of 3 types, and 17 miniplates were retrospectively examined in relation to clinical characteristics. The 1-year success rate of screws with 1.0-mm diameter was significantly less than that of other screws with 1.5-mm or 2.3-mm diameter or than that of miniplates. Flap surgery was associated with the patient's discomfort. A high mandibular plane angle and inflammation of peri-implant tissue after implantation were risk factors for mobility of screws. However, we could not detect a significant association between the success rate and the following variables: screw length, kind of placement surgery, immediate loading, location of implantation, age, gender, crowding of teeth, anteroposterior jaw base relationship, controlled periodontitis, and temporomandibular disorder symptoms. We concluded that the diameter of a screw of 1.0 mm or less, inflammation of the peri-implant tissue, and a high mandibular plane angle (ie, thin cortical bone), were associated with the mobility (ie, failure) of the titanium screw placed into the buccal alveolar bone of the posterior region for orthodontic anchorage.
  • Article
    The aim of this prospective clinical study was to assess the risk factors associated with failure of mini-implants used for orthodontic anchorage. A total of 140 mini-implants in 44 patients, including 48 miniplates and 92 freestanding miniscrews, were examined in the study. A variety of orthodontic loads were applied. The majority of implants were placed in the posterior maxilla (104/140), and the next most common location was the posterior mandible (34/140). A cumulative survival rate of 89% (125/140) was found by Kaplan-Meier analysis. There was no significant difference in the survival rate between miniplates and freestanding miniscrews, but miniplates were used in more hazardous situations. The Cox proportional-hazards regression model identified anatomic location and peri-implant soft tissue character as 2 independent prognostic indicators. The estimated relative risk of implant failure in the posterior mandible was 1.101 (95% confidence interval, 0.942 to 1.301; P = .046). The risk ratio of failure for implants surrounded by nonkeratinized mucosa was 1.117 (95% confidence interval, 0.899 to 1.405; P = .026). The results confirmed the effectiveness of orthodontic mini-implants, but in certain situations adjustment of the treatment plan or modifications in the technique of implant placement may lead to improved success rates.
  • Article
    Impaction of the lower second molar is not a common problem, but it is very challenging for both orthodontist and oral surgeon. Treatment options depend on the degree of tooth inclination, the position of the third molars, and the desired type of movement, which may be surgical and/or orthodontic in nature. A good treatment alternative is surgical uncovering with orthodontically-assisted eruption. A case of successful uprighting using a 0.017 x 0.025-inch titanium molybdenum alloy (TMA) tip-back cantilever is presented. Different aspects of uprighting impacted second molars are discussed in light of the literature. The iatrogenic character of lower second molar impaction is emphasized.