Download Efficiency of a skeletonized distal jet appliance supported by

CLINICIAN’S CORNER
Efficiency of a skeletonized distal jet appliance
supported by miniscrew anchorage for
noncompliance maxillary molar distalization
Gero S. M. Kinzinger,a Norbert Gülden,b Faruk Yildizhan,c and Peter R. Diedrichd
Homburg/Saar and Aachen, Germany
Introduction: Conventional anchorage appliances rely exclusively on intraoral anchorage for noncompliance
molar distalization. The partial coverage of the palate, in particular, often results in compromised oral hygiene.
An innovative alternative combines a skeletonized distal jet appliance with 2 paramedian miniscrews for additional anchorage. The objectives of this study were to investigate the suitability of the skeletonized distal
jet for translatory molar distalization and to check the quality of the supporting anchorage setup. Methods:
Two paramedian miniscrews (length, 8-9 mm; diameter, 1.6 mm) were placed into the anterior area of the palate in 10 patients. Skeletonized distal jet appliances fitted with composite to the first premolars and the collars
of the miniscrews were used for bilateral molar distalization, and the coil springs were activated with a distalization force of 200 cN on each side. Results: The study confirmed the suitability of the appliance for translatory molar distalization (3.92 6 0.53 mm) with slight mesial inward rotation (on average, 8.35 6 7.66 and
7.88 6 5.50 ). The forces acting reciprocally on the anchorage setup were largely absorbed by the anchorage
unit involving 2 anchorage teeth and 2 miniscrews. Significant anchorage loss, in the form of first premolar mesialization of 0.72 6 0.78 mm, was found. Conclusions: The skeletonized distal jet appliance supported by
additional miniscrew anchorage allows translatory molar distalization. Although the anchorage design combining 2 miniscrews at a paramedian location and the periodontium of 2 anchorage teeth does not offer the
quality of stationary anchorage, it achieves greater molar distalization in total sagittal movement than conventional anchorage designs with an acrylic button. (Am J Orthod Dentofacial Orthop 2009;136:578-86)
A
s alternatives to the compliance-dependent headgear for maxillary molar distalization, appliances
have been described that are worn only intraorally, are placed to remain fixed temporarily, and make
treatment success independent of patient compliance. A
major advantage for the patient, when comparing them
with the extraorally anchored headgear, is the lack of esthetic impairment. One of these appliances is the distal jet
(American Orthodontics, Sheboygan, Wis).1-3 The distal
jet has, as its active components, 2 coil-spring systems
that must be placed palatally. Loading the compression
coil springs generates forces that preformed bands abduct
a
Professor, Department of Orthodontics, University of Saarland, Homburg/Saar,
Germany.
b
Orthodontist, Department of Orthodontics, University of Saarland, Homburg/
Saar, Germany.
c
Orthodontist, Department of Orthodontics, RWTH Aachen, Aachen, Germany.
d
Professor and head, Department of Orthodontics, RWTH Aachen, Aachen,
Germany.
The authors report no commercial, proprietary, or financial interest in the
products or companies described in this article.
Reprint requests to: Gero Kinzinger, Department of Orthodontics, University
of Saarland, Kirrberger Strabe 1, D-66421 Homburg/Saar, Germany; e-mail,
[email protected].
Submitted, June 2007; revised and accepted, October 2007.
0889-5406/$36.00
Copyright Ó 2009 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2007.10.049
578
onto the permanent first molars and act distally. When it
is accurately manufactured in the dental laboratory and
anatomic relationships are favorable, the resultant lines
of force are close to the centers of resistance of the molars. Therefore, as opposed to cervical headgear, which
can achieve fractionated molar distalization only with
combined coronal tipping and subsequent root uprighting, the biomechanics of the appliance should in theory
enable it to perform almost translatory molar distalization.4 The reciprocally acting forces are therapeutically
undesired and must be absorbed by intraoral anchorage.
Conventionally, the anchorage setup of a distal jet appliance includes periodontal anchorage combined with further intraoral anchorage support: several teeth of the
maxillary dentition are laced to an acrylic palatal button,
by using bands or occlusal wire rests, to form an anterior
anchorage unit. Because of the temporary partial coverage of the palate, in particular, which restricts hygiene
capacity, this anchorage design has been the subject of
critical discussion.5 Furthermore, certain dentition stages
do not allow sufficient periodontal anchorage.6
As an alternative, a skeletonzed distal jet appliance
supported by additional miniscrew anchorage could be
used.5,7 It allows noncompliance molar distalization in
the maxilla even with limited dental anchorage quality
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 136, Number 4
Kinzinger et al
579
and, by dispensing with an acrylic button, also achieves
better hygiene of the palatal mucosa.
In an in-vitro study, Kinzinger and Diedrich4 demonstrated that the distal jet coil-spring systems allowed
almost translatory tooth movement in the sagittal plane
with uprighting effects on the dental root over a simulated distalization section of 3 mm based on a constant
distalization force of 200 cN, combined with a mesial
tipping moment. In the transverse plane, a force constantly directed toward the buccal aspect and a mesially
rotating moment resulted in combined buccal movement and therapeutically undesired mesial and inward
rotation of the permanent first molar.
The aims of this in-vivo study were to investigate
clinically the efficiency of the skeletonized distal jet
supported by additional miniscrew anchorage and to
compare the outcomes with the in-vitro series of measurements. A review of the literature resulted in a discussion of the share of anchorage loss in the total
movement in the sagittal plane, hence of the quality of
the miniscrew-supported periodontal anchorage setup,
when comparing it with other conventional intraorally
anchored, noncompliance distalization appliances.
MATERIAL AND METHODS
A skeletonized distal jet appliance was placed for bilateral molar distalization in the maxilla in 10 patients
(8 girls, 2 boys; average age, 12 years 1 month) with
dentoalveolar Class II malocclusion and dental archlength discrepancies. The mean treatment duration
was 6.7 months. Of the total of 20 second molars, 11
were germinating, and 5 were erupting. Only 4 had
already reached the occlusal plane.
For the distal jet used in this study, the palatal acrylic
button was removed as a means of anchorage. Instead, the
modified appliance was anchored skeletally to 2 miniscrews placed into the palate at a paramedian location
and, additionally, dentally to 2 occlusal rests. In terms
of laboratory technique, this meant that prefabricated telescope spring assemblies, whose wings were bent distally
to form occlusal rests, were connected to each other by using a soldered or laser-welded transverse wire (Fig 1).
Every patient’s bone supply in the anterior area of the
palate was analyzed on lateral cephalographs to determine the length of the screw shaft. After a preoperative
mouth rinse with 0.1% chlorhexidine gluconate solution
and local terminal anesthesia with an adrenalin-free
anesthetic, 2 miniscrews with neck and collar (length,
8-9 mm, diameter, 1.6 mm; Forestadent, Pforzheim,
Germany; or System Dual Top, Jeil Medical Corporation,
Seoul, South Korea) were placed at a paramedian location in the anterior area of the palate (at the line of the first
Fig 1. Skeletonized distal jet appliance supported by
additional miniscrew anchorage: treatment of a girl
aged 11 years 1 month; duration of distal jet treatment,
5 months. A, Occlusal view immediately after skeletonized distal jet placement: in terms of laboratory technique, prefabricated coil-telescope systems, the wings
of which are bent distally to form occlusal rests, are connected to each other with a wire soldered to them. This
transverse connecting wire is fitted dorsally to the miniscrew necks. B, Occlusal view after molar distalization:
clinical assessment shows bodily molar distalization
and spontaneous second premolar dental drifting.
premolars) with a manual screwdriver and adequate
sodium chloride cooling. No predrilling was performed.
All miniscrews were tested for primary stability by using
a probe; they were loaded a week after placement.
Skeletonized distal jet appliances were attached to the
premolars by using occlusal wire rests and to the necks of
the miniscrews with transverse wires fitted dorsally and
secured with composite. The occlusal rests also resulted
in transverse reinforcement of the appliances. Accordingly, the anchorage setup consisted of a periodontal
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Kinzinger et al
American Journal of Orthodontics and Dentofacial Orthopedics
October 2009
A
UR2
UL2
N
S
Ar
mb
cf UL6
db
UR6
ANS-PNS´
ANS
A
PNS
Go-Me´
MPR
Fig 2. Cast analysis (changes in the horizontal plane):
angular and linear measurements to determine changes
in the transverse width of the dental arch and rotation of
the first molars.
footing with the added support of miniscrews. The wings
of the arc sections, which represent a bayonet bend, were
fitted into the palatal sheaths of the molar bands. Then the
loaded coil systems, with superelastic compression
springs, were activated by fitting attachment screws dorsally with a distalization force of 200 cN for each system
and reactivated every 4 weeks.
To verify molar movement in the horizontal plane,
plaster dental casts were taken at the start of treatment
(T1) and after distal jet appliance removal (T2). The
changes near the molars were assessed by measuring
corresponding casts with a digital sliding caliper. Objects of analysis were changes in length of the supporting
zone, increase or decrease of the transverse width of the
dental arch at the line of the first molars, and extent and
kind of tooth rotation. For every cast, the distance from
the distal point of contact of the lateral incisor to the mesial point of contact of the first molar and, bilaterally, the
distance from the lowest point of the central fossa to the
mesiobuccal and the distobuccal cusps of the first molar
were registered. In addition, the angles between a line
running through the mesiobuccal and distobuccal cusps
and the midpalatal raphe were measured (Fig 2).
The cephalographs taken at T1 and T2 were analyzed
to determine changes in the following parameters (Fig 3).
1.
2.
3.
SNA: the angle between the anterior cranial base
and the deepest point of the ventral concavity of
the maxilla.
SNB: the angle between the anterior cranial base
and the deepest point of the ventral concavity of
the mandible.
S-N/ANS-PNS: the angle between the anterior
cranial base and the palatal plane.
Go
B
Me
B
N
S
P
Pt
PNS
Or
ANS
Fig 3. Cephalometric analysis (changes in the sagittal
plane): angles and distances registered on the lateral
cephalograph before and after molar distalization: A,
skeletal angular and linear values; B, dental angular
and linear values.
4.
5.
ANS-PNS/Go-Me: the angle between the palatal
plane and the mandibular plane.
Björk’s summation angle: the sum of the saddle
angle (NSAr), the articular angle (SArGo), and
the gonial angle (ArGoMe).
Kinzinger et al
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 136, Number 4
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
S-Go:N-Me: the facial height ratio (posterior face
height to anterior face height).
U1-CEJ/PTV: the distance from the maxillary
central incisor to the pterygoid vertical.
U4-CEJ/PTV: the distance from the maxillary first
premolar to the pterygoid vertical.
U5-CEJ/PTV, the distance from the maxillary second premolar to the pterygoid vertical.
U6-CEJ/PTV: the distance from the maxillary first
molar to the pterygoid vertical.
U1/ANS-PNS: the angle between the maxillary
central incisor and the palatal plane.
U1/SN: the angle between the maxillary central
incisor and the anterior cranial base.
U4/ANS-PNS: the angle between the maxillary
first premolar and the palatal plane.
U4/SN: the angle between the maxillary first premolar and the anterior cranial base.
U5/ANS-PNS: the angle between the maxillary
second premolar and the palatal plane.
U5/SN: the angle between the maxillary second
premolar and the anterior cranial base.
U6/ANS-PNS: the angle between the maxillary
first molar and the palatal plane.
U6/SN: the angle between the maxillary first
molar and the anterior cranial base.
U1-CEJ/ANS-PNS: the distance from the maxillary central incisor to the palatal plane.
U4-CEJ/ANS-PNS, the distance from the maxillary first premolar to the palatal plane.
U5-CEJ/ANS-PNS: the distance from the maxillary second premolar to the palatal plane.
U6-CEJ/ANS-PNS: the distance from the maxillary first molar to the palatal plane.
SNA, SNB, S-N/ANS-PNS, ANS-PNS/Go-Me,
Björk’s summation angle, and the facial height ratio
were measured or computed to verify any skeletal
changes.
In the sagittal plane, the relative incisor and first premolar mesial movement, hence the anchorage loss, and
the relative second premolar and first molar distal movement in relation to the pterygoid vertical (U1-CEJ/PTV,
U4-CEJ/PTV, U5-CEJ/PTV, and U6-CEJ/PTV) were
determined. The respective points of reference for the
measurements were the cementoenamel junction
(CEJ) on the longitudinal axis of the teeth. Growthinduced changes (increase of 1 mm per year) were taken
into account.
The amounts of labial tipping of the incisors and
first premolars and distal tipping of the second premolars and first molars were determined based on the
angles between the longitudinal tooth axis and, respec-
581
tively, the palatal plane or the anterior cranial base (U1/
ANS-PNS, U1/SN; U4/ANS-PNS, U4/SN; U5/ANSPNS, U5/SN; U6/ANS-PNS, U6/SN).
Potential tooth intrusions and extrusions were verified in the palatal plane (U1-CEJ/ANS-PNS, U4-CEJ/
ANS-PNS, U5-CEJ/ANS-PNS, and U6-CEJ/ANSPNS).
Statistical analysis
Statistical computations were performed with SPSS
software (version 14, SPSS, Chicago, Ill). Casts and lateral cephalographs were traced twice at a 4-week interval. If values deviated, the means of both measurements
were fed into the statistical analysis. Then the arithmetic
mean and the standard deviation were computed for every variable used in the in-vivo measurements, and the
changes of each variable from T1 to T2 were statistically analyzed with a 1-sample t test. Thereby, we determined which effective changes were therapeutically
induced by the treatment as evidence against the null
hypothesis. Differences with a probability of error less
than 5% (P \0.05) were considered statistically significant.
RESULTS
Metrical assessment of the maxilla casts before and
after molar distalization with a skeletonized distal jet
appliance showed the following dental position changes
of the permanent first molars (Table I).
The supporting zones increased by 4.01 6 0.63 mm
in the first quadrant and 3.64 6 0.69 mm in the second
quadrant. The transverse widths of the dental arch increased by means of 1.79 6 1.08 mm between the mesiobuccal cusps, 2.58 6 0.69 mm between the central
fossae, and 3.03 6 0.68 mm between the distobuccal
cusps; this indicates both expansion and mesial inward
rotation of the permanent first molars. When we looked
more closely, the permanent first molars of the first
quadrant had rotated mesiopalatally and distobuccally
by a mean 8.35 6 7.66 and those of the second quadrant, by 7.88 6 5.50 . All position changes of the
permanent first molars were significant.
Skeletal assessments showed that the cranial base
remained constant, with changes of the SNA angle of
only a mean 0.19 6 0.80 and the SNB angle of only
a mean 0.13 6 0.82 . The positional relationships of
the palatal plane to the anterior cranial base and to the
mandibular plane were virtually unchanged. Björk’s
summation angle changed by only 0.73 6 1.26 during
molar distalization, and the facial height ratio changed
by 0.58% 6 1.51%. All registered skeletal changes
during treatment were not significant (Table II).
582
Kinzinger et al
Table I.
American Journal of Orthodontics and Dentofacial Orthopedics
October 2009
Changes in permanent first molar position induced by distal jet therapy in the horizontal plane
Cast analysis
n
T1 mean
T1 SD
T2 mean
T2 SD
DT1-T2 mean
DT1-T2 SD
Significance
UR2 distal-UR6 mesial (mm)
UL2 distal-UL6 mesial (mm)
Mesiobuccal cusp tips UR6-UL6 (mm)
Central fossa UR6-UL6 (mm)
Distobuccal cusp tips UR6-UL6 (mm)
Tooth UR6 rotation ( )
Tooth UL6 rotation ( )
10
10
10
10
10
10
10
20.80
21.17
50.80
45.80
53.06
12.86
13.43
2.04
1.90
2.16
2.36
1.70
6.15
4.29
24.81
24.81
52.59
48.39
56.09
21.21
18.93
2.34
2.08
1.28
2.04
1.49
6.28
5.94
–4.01
–3.64
–1.79
–2.58
–3.03
–8.35
–7.88
0.63
0.69
1.08
0.69
0.68
7.66
5.50
‡
‡
†
‡
‡
*
*
Determination of type of molar rotation: angle between midpalatal raphe and a line running through the mesiobuccal and distobuccal cusps of the
molars; for DT1-T2 (value before distalization) – (value after distalization): positive value 5 mesiobuccal and distopalatal rotation, negative value 5
mesiopalatal or distobuccal rotation.
*P \0.05; †P \0.01; ‡P \0.001.
Table II.
Skeletal angular and linear measurements
Cephalometric analysis
Skeletal-angular
SNA ( )
SNB ( )
S-N/ANS-PNS ( )
ANS-PNS/Go-Me ( )
Björk’s summation angle ( )
Skeletal-linear
S-Go:N-Me (%)
n
T1 mean
T1 SD
T2 mean
T2 SD
D T1-T2 mean
D T1-T2 SD
Significance
10
10
10
10
10
83.55
79.83
5.56
24.20
389.61
2.63
3.42
1.92
4.31
3.29
83.36
79.70
5.18
25.08
390.34
2.78
3.27
1.53
4.14
3.49
0.19
0.13
0.38
–0.88
–0.73
0.80
0.83
1.18
1.09
1.26
NS
NS
NS
NS
NS
10
67.49
2.79
66.91
2.60
0.58
1.51
NS
NS, Not significant.
In the area of the CEJ, the permanent first molars
were distalized by a mean of 3.92 6 0.53 mm and intruded by a mean of 0.16 6 0.26 mm. At the same
time, they experienced distal tipping of 2.79 6 2.51
in relation to the palatal plane and 3.00 6 2.31 in relation to the anterior cranial base. The second premolars,
which were not part of the anchorage setup, drifted distally after the molars by 1.87 6 0.74 mm, elongating by
0.42 6 0.41 mm and tipping, in relation to the respective
reference planes, by 3.00 6 2.69 and 3.21 6 2.86 .
The first premolars, included in the anchorage setup,
mesialized by 0.72 6 0.78 mm, extruded by 0.14 6 0.14
mm, and, at the same time, tipped by 1.15 6 2.98 in
relation to the palatal plane and by 0.79 6 2.23 in relation to the anterior cranial base. The central incisors
were protruded by 0.36 6 0.32 mm and extruded by
0.14 6 0.29 mm, and showed slight labial tipping
of 0.57 6 0.79 in relation to the palatal plane and
0.64 6 0.75 to the anterior cranial base.
All linear dental movements in relation to the pterygoid vertical, the extrusion of the premolars, and the
angular dental position changes of the second premolars
and first molars were significant (Table III).
The total movement in the sagittal plane was 4.28 6
0.51 mm (cumulating molar distalization and central incisor protrusion) or 4.64 6 1.06 mm (cumulating molar
distalization and first premolar mesialization). Based on
the values obtained for the permanent first molars—
distalization length of a mean 3.92 6 0.53 mm—molar
distalization represents 91.71% 6 7.32% and 86.56%
6 13.21%, respectively, of the total sagittal movement
(Table IV).
DISCUSSION
The outcomes confirm the efficiency of the distal jet
in clinical applications. Cast registrations showed that
the supporting zone had increased, and that a therapeutically desired widening of the dental arch, as well as mesial inward and distal outward rotations of the molars,
had occurred. The biomechanical explanation of this effect is that force is applied palatally from the center of
resistance of the molars. In theory, a toe-in bend would
be appropriate to compensate for this effect, but it results in friction in the guide tubes of the appliance.
This effect was verified with the casts used and by an
in-vitro registration. The resultant adhesive effect expressing this friction reduced the distalization force substantially and, accordingly, would be an obstacle for
distalization of the molars. Therefore, a toe-in bend
should not be used, although it would be therapeutically
desirable.4 After the distal jet treatment, the molars
Table III.
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Kinzinger et al
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 136, Number 4
Dental angular and linear measurements
Cephalometric analysis
Dental-angular
U1/AN-PNS ( )
U1/SN ( )
U4/AN-PNS ( )
U4/SN ( )
U5/ANS-PNS ( )
U5/SN ( )
U6/ANS-PNS ( )
U6/SN ( )
Dental-linear
U1-CEJ/PTV (mm)
U4-CEJ/PTV (mm)
U5-CEJ/PTV (mm)
U6-CEJ/PTV (mm)
U1-CEJ/ANS-PNS (mm)
U4-CEJ/ANS-PNS (mm)
U5-CEJ/ANS-PNS (mm)
U6-CEJ/ANS-PNS (mm)
n
T1 mean
T1 SD
T2 M
T2 SD
D T1-T2 M
D T1-T2 SD
Significance
10
10
10
10
10
10
10
10
107.93
101.86
91.86
85.86
82.29
76.50
75.36
69.71
4.80
5.28
6.01
7.61
4.71
5.37
3.82
4.79
108.50
102.50
90.71
85.07
79.29
73.29
72.57
66.71
4.94
5.45
6.11
7.37
5.62
5.26
4.04
4.35
–0.57
–0.64
1.15
0.79
3.00
3.21
2.79
3.00
0.79
0.75
2.98
2.23
2.69
2.86
2.51
2.31
NS
NS
NS
NS
*
*
*
*
10
10
10
10
10
10
10
10
52.54
38.47
31.21
22.59
17.96
15.79
14.59
13.16
2.94
3.37
3.11
3.31
2.62
1.53
2.06
1.78
52.90
39.19
29.34
18.67
18.10
15.93
15.01
13.00
2.98
3.78
3.00
3.11
2.44
1.55
1.97
1.65
–0.36
–0.72
1.87
3.92
–0.14
–0.14
–0.42
0.16
0.32
0.78
0.74
0.53
0.29
0.14
0.41
0.26
*
*
†
‡
NS
*
*
NS
*P \0.05; †P \0.01; ‡P \0.001; NS, not significant.
Proportion of maxillary molar distalization in
total movement in the sagittal plane
Table IV.
Cephalometric analysis
Dental-linear (mm)
U1-CEJ/PTV (mm)
U4-CEJ/PTV (mm)
U6-CEJ/PTV (mm)
Total sagittal movement 1-6*
Total sagittal movement 4-6†
Calculation of ratio (%)
Proportion of molar
distalization in total
sagittal movement 1-6‡
Proportion of molar
distalization in total
sagittal movement 4-6§
n
D T1-T2 mean
D T1-T2 SD
10
10
10
10
10
–0.36
–0.72
3.92
4.28
4.64
0.32
0.78
0.53
0.51
1.06
10
91.71
7.32
10
86.56
13.21
*Total movement in the sagittal plane 1-6 5 [U1-CEJ/PTV] 1 [U6CEJ/PTV]; †Total movement in the sagittal plane 4-6 5 [U4-CEJ/
PTV] 1 [U6-CEJ/PTV]; ‡Calculation: proportion of molar distalization in total sagittal movement 1-6 5 100 3 (U6-CEJ/PTV)/([U1CEJ/PTV] 1 [U6-CEJ/PTV]); §Calculation: proportion of molar distalization in total sagittal movement 4-6 5 100 3 (U6-CEJ/PTV)/
([U4-CEJ/PTV] 1 [U6-CEJ/PTV]).
should be derotated with an appropriate appliance, such
as a transpalatal bar or a bi-helix.
We found, during lateral cephalograph analysis, unlike the results of the in-vitro analysis, that the permanent first molars experienced slight dental crown
tipping in the sagittal plane rather than root uprighting.4
The cause of this might be that the patients’ palatal
vaults were not deep enough to enable placement of
the loaded coil systems at the level of the center of resis-
tance of the molars. Also, the location of the center of
resistance can be determined only by approximation.
Moreover, the respective development stages of the second molars might influence the extent of distal tipping
of the first molars. In most patients in this study, the second molars were germinating or erupting. In a clinical
study with pendulum appliances, Kinzinger et al8
showed that the extent of distal tipping is relatively
greater when the second molars are only germinating.
This phenomenon can be explained as follows: a germinating second molar has the same effect as a lever pivot
point on the permanent first molar to be distalized; the
first molar, when reacting to distalization, tips over the
second molar germ. As its root is developing and the
permanent second molar is erupting, the point of contact
between the 2 molars gradually moves coronally. The
tendency for the first molar to tip thereby decreases.
Conventionally, the anchorage setup of exclusively
intraorally anchored appliances for noncompliance molar distalization combines an acrylic button on the palatal mucosa with using the periodontium of anchorage
teeth. The disadvantages of this kind of anchorage include, in particular, restrictions to hygiene5 and contraindications based on certain dentition stages and local
situations.7 Moreover, it must be discussed how far
the anchorage effect of an anteriorly placed Nance
button potentially relies only on hydrodynamic interactions due to the resilient mucosa. Thereby it would be
a disqualifying design for stationary anchorage designs,
and hence must not be overestimated in terms of anchorage quality.5
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Kinzinger et al
Table V.
American Journal of Orthodontics and Dentofacial Orthopedics
October 2009
Studies using different conventionally intraorally anchored appliances for maxillary molar distalization
Author/reference
31
Distalization appliance
Angelieri et al
Hilgers pendulum with uprighting activation
Bolla et al32
Bondemark and Kurol33
Bondemark et al34
Bondemark and Kurol35
Bondemark36
Distal jet
Magnets
Magnets/supercoils
Magnets/supercoils
Magnets/NiTi coils
Brickman et al37
Bussick and McNamara38
Byloff and Darendeliler39
Byloff et al40
Chaques-Asensi and Kalra41
Chiu et al42
Fortini et al43
Fuziy et al44
Jones jig
Hilgers pendulum
Hilgers pendulum
Hilgers pendulum with
uprighting activation
Hilgers pendulum
Distal jet/Hilgers pendulum
FCA
Hilgers pendulum
Gosh and Nanda45
Gulati et al46
Haydar and Üner47
Joseph and Butchart48
Kinzinger et al50
Kinzinger et al8
Kinzinger et al50
Kinzinger et al51
Mavropoulos et al52
Ngantung et al53
Nishii et al54
Papadopoulos et al55
Hilgers pendulum
Jones jig
Jones jig
Hilgers pendulum
Pendulum K
Pendulum K
Pendulum K
Pendulum K
Jones jig
Distal jet
Distal jet
Modified jig
Treatment Soft-tissue
subjects (n) support* Dental anchorage†
22
NP
20
10/10
18/18
18/18
21/21
NP
NP
NP
NP
NP
2 B PM1
2 OW PM2
2 B PM1
2 B PM2
2 B PM2
2 B PM2
2 B PM2
72
101
13
20
NP
NP
NP
NP
2 B PM2
4 OW
4 OW
4 OW
26
32/32
17
31
NP
NP
NP
NP
41
10
10
7
50
36
30
10
66
33
15
14
NP
NP
NP
NP
NP
NP
NP
NP
NP
NP
NP
NP
2 B PM1
2 B PM2/4 OW
2 B PM2
2 B PM1
2 OW PM2
4 OW
4 B PM1 and PM2
2 B PM2
4 OW
4 OW
4 OW
4 OW
4 OW
2 B PM2
2 B PM2
2 B PM2
2 B PM2
Share of molar
distalization in total
movement (%)
35.7 PM1, 45.4 I
71.1 PM1
70 I
53.7 I/62.7 I
55 I/59 I
59.1 PM1,
57.8 I/67.6 PM1, 61.9 I
55.7 PM1
76.0 PM1
70.9 PM1
64.2 PM1
70.6 PM1; 71.8 I
51.8 PM1/81.3 PM
70.2 PM1; 76.9 I
63.5 PM1
56.9 PM1
55.0 PM1
45.0 PM1
57.9 I
72.5 I
70.2 I
76.3 PM1; 74.2 I
73.5 I
47.8 PM2; 51.3 I
44.9 PM2
63.1 PM1; 61.5 I
35 PM1, 37.8 I
NiTi, Nickel-titanium; FCA, first-class appliance.
* Intraoral anchorage designs: NP, Nance pad; B, premolar bands anchored to the Nance pad with connecting wires; OW, occlusal wire rests anchored
to the Nance pad; PM1, first premolars; PM2, second premolars.
†
With specific reference: PM1, first premolar; PM2, second premolar; I, central incisor.
Alternative anchorage components for molar distalization appliances include titanium miniscrews of small
diameter and orthodontic implants of short length. In
clinical application, short endosseous titanium implants
provide quality stationary anchorage.9-13 So-called miniscrews, placed at a location paramedian to the palatal
suture in the patients in this study, are less costly and,
compared with short implants, can be placeed and removed with minimal invasion.
Most clinical and experimental studies as well as
case reports on anchorage with miniscrews deal with
primary stability, rate of loss, and patient comfort of
these implants.14-27 Only a few studies provide information on position stability of these anchorage components
during orthodontic treatment. Liou et al28 and Kinzinger
et al29 examined the anchorage quality of miniscrews
subjected to orthodontic forces and concluded that,
although they allowed stable anchorage, they did not
fully maintain their positions under continuous loading.
According to Park et al,30 some mobility in orthodontic
screw implants does not necessarily mean that the outcome is compromised. Rather, even minimally mobile
miniscrews can provide sufficient anchorage quality.
Our results show that the described miniscrew-supported periodontal anchorage does not allow anchorage
of stationary quality. Nevertheless, it offers essential advantages compared with conventional anchorage designs; by limiting the number of occlusal rests to 2,
treatment is possible even with fewer teeth, with lower
anchorage quality in the supporting zone. Spontaneous
distal drifting of the second premolars, which were
not part of the anchorage setup, reduced the length of
the subsequent treatment phase. In this study, the second
premolars drifted distally after the molars almost bodily
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 136, Number 4
by 1.87 6 0.74 mm. In the subsequent active distalization of the anterior dentition, the molars can be
anchored to the miniscrews.
Various studies, in which different intraoral appliances with conventional anchorage designs (acrylic
button and 2-4 anchorage teeth) were used for molar
distalization, give the share of molar distalization in
the total movement as 35% to 81.3% (Table V).8,31-55
The miniscrew-supported periodontal anchorage of
the skeletonized distal jet used in this study, on the other
hand, allows greater molar distalization in the total
movement—91.71% and 86.56%; this is a reason that
this innovative anchorage design makes sense as a treatment alternative.
CONCLUSIONS
In the sagittal dimension, the miniscrew-supported
distal jet appliance allows almost translatory molar distalization. Because of the palatal force application from
the center of resistance of the molars, the teeth experience therapeutically undesired mesial inward and distal
outward rotation.
The incorporation into the anchorage setup of 2
miniscrews at paramedian locations has the following
advantages compared with conventional anchorage designs: by dispensing with an acrylic button that covers
the palate, hygiene of the palatal mucosa improves. Additional dental anchorage requires only 2 teeth. The second premolars, which are not part of the anchorage, can
drift distally spontaneously under the pulling effect of
the transseptal fibers.
Although a miniscrew-supported periodontal anchorage of a skeletonized distal jet appliance does not offer stationary anchorage quality, it allows a greater percentage of
molar distalization in the total movement than do conventional anchorage designs with an acrylic palatal button.
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