Download Long-term stability of maxillary group distalization with interradicular

CASE REPORT
Long-term stability of maxillary group
distalization with interradicular miniscrews in a
patient with a Class II Division 2 malocclusion
Shingo Kuroda,a Natsuko Hichijo,b Minami Sato,b Akiko Mino,b Nagato Tamamura,c Mitsuhiro Iwata,d
and Eiji Tanakae
Tokushima, Amagasaki, and Okayama, Japan, and Jeddah, Saudi Arabia
We successfully treated a Class II Division 2 patient with maxillary group distalization using interradicular miniscrews. A woman, aged 28 years 11 months, had a convex profile and an excessive overjet caused by a skeletal
Class II jaw-base relationship. After leveling and alignment, titanium miniscrews were obliquely implanted between the maxillary second premolar and first molar. To distalize the maxillary dentition, nickel-titanium closing
coil springs with a 2-N load were placed between the screws and the hooks on the archwire. After 28 months of
active orthodontic treatment, a proper facial profile and an acceptable occlusion were achieved with a 4-mm distalization of the maxillary dentition. The resultant occlusion was stable throughout a 5-year retention period.
Interradicular miniscrews were useful to distalize the maxillary dentition for correcting a Class II malocclusion.
This new strategy, group distalization with miniscrews, can make the treatment simpler with greater predictability. (Am J Orthod Dentofacial Orthop 2016;149:912-22)
I
n the treatment of a Class II malocclusion, tooth
extraction or nonextraction is a subject of much
debate.1-3 In growing patients, growth modification
is often tried to improve their anteroposterior jaw
discrepancies without extractions.2 If a nongrowing patient has excessive overjet or a severe arch length discrepancy, orthodontists are likely to choose extraction
treatment.3 However, most patients desire nonextraction
treatment, if possible, and some do not accept extractions.
In such patients, orthodontists must seek other treatment options. Molar distalization can be an alternative
a
Associate professor, Department of Orthodontics and Dentofacial Orthopedics,
Institute of Biomedical Sciences, Graduate School, Tokushima University, Tokushima, Japan.
b
Postgraduate student, Department of Orthodontics and Dentofacial Orthopedics, Graduate School of Oral Sciences, Tokushima University, Tokushima, Japan.
c
Private practice, Amagasaki, Japan.
d
Private practice, Okayama, Japan.
e
Professor and chair, Department of Orthodontics and Dentofacial Orthopedics,
Institute of Biomedical Sciences, Graduate School, Tokushima University, Tokushima, Japan; distinguished adjunct professor, King Abdulaziz University, Jeddah, Saudi Arabia.
All authors have completed and submitted the ICMJE Form for Disclosure of
Potential Conflicts of Interest, and none were reported.
Address correspondence to: Eiji Tanaka, Department of Orthodontics and Dentofacial Orthopedics, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-Cho, Tokushima 770-8504, Japan; e-mail,
[email protected].
Submitted, January 2015; revised and accepted, July 2015.
0889-5406/$36.00
Copyright Ó 2016 by the American Association of Orthodontists.
http://dx.doi.org/10.1016/j.ajodo.2015.07.045
912
to correct a Class II malocclusion. However, it is not
easy to distalize the maxillary dentition completely
with traditional orthodontic mechanics.2 Various types
of molar distalizers have been developed and clinically
used, but they cannot prevent counteractions: eg, flaring of the maxillary incisors.4-7 In addition, a group
distalization of the maxillary dentition was almost
impossible in most patients.
Recently, implant-anchored orthodontics has been
shown to be effective in treating a wide variety of malocclusions.8-13 In particular, miniscrews have gained
acceptance because they can provide stable anchorage
for various types of tooth movement despite their
small diameter and short length.12 Miniscrew anchorage
can provide maxillary molar distalization without patient compliance and undesirable counteractions; therefore, now they are well regarded as a new treatment
strategy for Class II correction.14-17 However, their
long-term stability is still unknown.
In this case report, we demonstrate the 5-year retention of a group distalization of the maxillary dentition
with interradicular miniscrews in an adult patient with
a Class II Division 2 malocclusion.
DIAGNOSIS AND ETIOLOGY
A woman, aged 28 years 11 months, had a chief
complaint of esthetic problems of her maxillary incisors. Her facial profile was convex, and the frontal
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Fig 1. Pretreatment facial and intraoral photographs.
TREATMENT OBJECTIVES
view was almost symmetric
Fig( 1). The molar relationships were Angle Class II on both sides
Fig 2).
( Overjet
The patient was diagnosed as having an Angle Class II
and overbite were 5.0 and 0.0 mm, respectively. TheDivision 2 malocclusion with a skeletal Class II jaw-base
maxillary and mandibular dental midline almost coin-relationship. An excessive overjet and a reduced overbite
cided with the facial midline. In the panoramic radio-were also shown. The treatment objectives were to
graph, the maxillary left central and right lateral achieve (1) an acceptable occlusion with a good funcincisors and the mandibular
first molars were nonvital tional Class I occlusion and (2) an attractive smile and
(Fig 3). Periapical lesions were observed in the mandib-balanced facial pro
file.
ular first molars. The maxillary third molars had already To achieve a functional Class I occlusion, distalization
been extracted, but the mandibular third molars were
of the maxillary dentition was necessary. Then, placeimpacted.
ment ofi nterradicular miniscrews was planned in the
The cephalometric analysis, when compared with the
posterior maxilla. The mandibular
first molars would be
Japanese norm, showed a skeletal Class II jaw-base rela-extracted, and mesialization of the second and third motionship (ANB, 9.0) (Table).18 The mandibular plane lars was proposed to reduce the spaces for restorations.
). The maxillary
was steep (mandibular plane-SN, 44.0
), but the
incisors were lingually inclined (U1-SN, 90.0
mandibular incisors showed an average inclinationTREATMENT ALTERNATIVES
Several procedures were explored to achieve an
). As the result, the interin(L1-mandibular plane, 93.5
cisal angle was increased (134.0
).
acceptable occlusion. Extraction of the maxillary
first
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Fig 2. Pretreatment dental casts.
Fig 3. Pretreatment lateral cephalogram, cephalometric tracing, and panoramic radiograph.
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915
Table. Cephalometric summary
Variable
ANB ( )
SNA ( )
SNB ( )
Mandibular plane-SN ( )
U1-SN ( )
L1-mandibular plane ( )
Interincisal angle ( )
Overjet (mm)
Overbite (mm)
Japanese
norm*
2.8
80.8
77.9
37.1
105.9
93.4
123.6
3.1
3.3
SD
2.4
3.6
4.5
4.6
8.8
6.8
10.6
1.1
1.9
Pretreatment
9.0
85.0
76.0
44.0
90.0
93.5
134.0
5.0
0.0
Posttreatment
8.0
84.0
76.0
44.0
88.5
90.0
137.0
3.0
3.0
Postretention
8.0
84.0
76.0
44.0
88.5
90.0
137.0
3.0
3.0
*Wada et al,18 1981.
Fig 4. Treatment progress: A, 3 months after the start of treatment; after leveling and alignment, miniscrews were implanted at the mesial alveolus of the maxillary first premolar, and molar distalization was
started with 200-g nickel-titanium closed-coil springs; in the mandible, the second molar mesialization
was started. B, 12 months later, the mandibular second molars were completely mesialized, and uprighting of the right third molar was started. C, 18 months later, the mandibular third molars were
completely uprighted.
premolars was considered to reduce the excessive overjet. However, the maxillary third molars had already
been extracted, and 2 maxillary incisors were nonvital.
Therefore, premolar extractions should be avoided to
retain as many intact teeth as possible.
As for the mandibular first molars, prosthetic restorations without orthodontic treatment might shorten the
total treatment period. However, this requires pulpectomy of the proximal teeth when bridge restorations
are chosen. Moreover, dental implants are expensive
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Fig 5. A and C, Distal movement of the maxillary molars: miniscrews are shown at the mesial alveolus of
the first molars before distalization, but in B and D, the miniscrews are observed beside the second premolar after distalization, which meant a 4-mm distalization of the maxillary dentition. A and C, 2 months
after the start of treatment; B and D, 24 months later; A and B, right side; C and D, left side.
and cause considerable surgical invasion, and their
longevity is still unclear. Therefore, molar mesialization
was planned to reduce the spaces for prosthetic restorations and to reconstruct the whole mandibular dentition
with vital teeth.
TREATMENT PROGRESS
The mandibular first molars were extracted, and
0.022-in slot preadjusted edgewise appliances were
placed on both arches. After leveling and alignment
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with nickel-titanium archwires, the mesialization of the
mandibular second molars was started with closingloop mechanics and a stainless steel archwire (Fig 4, A).
Two months after the start of treatment, miniscrews
(diameter, 1.3 mm; length, 7 mm; Absoanchor; Dentos,
Daegu, South Korea) were implanted at the distal alveolus of the maxillary second premolars (Fig 5, A and
C). They were inserted obliquely in the surface of the
cortical bone with the self-tapping method. After the
1-month latency period, distal movement of the
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Fig 6. Posttreatment facial and intraoral photographs.
maxillary dentition was started with a 2-N load of theTREATMENT RESULTS
nickel-titanium closed-coil springs (Sentalloy; Tomy, On the posttreatment facial photographs, a balanced
Tokyo, Japan)Fig
( 4, A).
facial profile was achievedFig
( 6). The occlusion was
At 12 months of treatment, a molar tube was much more stable, and an acceptable intercuspation of
bonded on the erupting mandibular right third molarthe teeth was achieved with Class I canine and molar re(Fig 4, B). After leveling with the nickel-titanium wires, lationshipsFig
( 7). The mandibular second molars were
uprighting of the mandibular right third molar wascompletely mesialized to the position offirst
themolars.
initiated Fig
( 4, C).
In the panoramic radiograph, proper root parallelism
After removal of the edgewise appliances, a wrap-is shown, and the impacted mandibular third molars
around type of retainer was placed on the maxillarywere uprighted and mesialized
Fig (8). The posttreatarch, and a lingual bonded retainer was set on thement cephalometric evaluation still showed a Class II
mandibular anterior teeth. The total active orthodonticjaw-base relationship (SNA, 84.0
; ANB, 8.0 ). The
treatment time was 28 months. During the retentionmaxillary molars were bilaterally distalized for 5.0 mm,
period, tooth whitening was performed on both denti-but the mandibular plane angle was stable (mandibular
tions, and the maxillary incisors were restored with zirco-plane-SN, 44.0) (Table). Both the maxillary and
nia crowns.
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Fig 7. Posttreatment dental casts.
Fig 8. Posttreatment lateral cephalogram, cephalometric tracing, and panoramic radiograph.
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Fig 9. Five-year postretention facial and intraoral photographs.
mandibular incisors were lingually inclined (U1-SN, For group distalization of the maxillary dentition, it
), but the acceptable might be believed that temporary anchorage devices
88.5; L1-mandibular plane, 90.0
interincisal relationship was maintained. No symptomsshould be placed out of the dentition
̶ie, the screws
of temporomandibular disorder were observedat midpalate or miniplates at the zygomatic prothroughout active orthodontic treatment.
cess.14,15,19,20 However, miniplates requireflap
At the 5-year postretention checkup, the occlusionsurgery at both placement and removal, and these
was stable, and the good facial file
prowas also retained procedures cause considerable pain and discomfort
21
Palatal screws need some kind of bulky
(Fig 9). The panoramic radiograph and cephalometricfor patients.
appliance to connect the screw and the archwire, and
analysis showed little change
Figs( 10 and 11
; Table).
these palatal devices are also unpleasant for patients.
In contrast, interradicular screws are relatively
DISCUSSION
comfortable. Nevertheless, most orthodontists still
In this patient, distal movement of the maxillary in- believe that they are not suitable for group distalization of the dentition because the screws would come
cisors was required to treat the excessive overjet. Premoin contact with the surrounding root during tooth
lar extractions were avoided because 2 maxillary incisors
movement. Actually, interradicular miniscrews may
were nonvital, and there was enough bone at the postenot interfere with tooth movement when they are
rior maxilla for molar distalization.
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Fig 10. Lateral cephalogram, cephalometric tracing, and panoramic radiograph at the 5-year postretention checkup.
obliquely inserted in the alveolar bone with adequate
buccolingual thickness.16
In this patient, the interradicular screws were placed
at the mesial alveolus of the maxillary first premolars but
are shown at the middle part of the second premolar after treatment (Fig 5, B and D). This means that the root
of the maxillary second premolars could pass through
the lingual side of the obliquely inserted miniscrews.
Of course, such a tooth movement is not feasible in all
patients. Analyses of the alveolar bone thickness with radiographs, and 3-dimensional computed tomography if
possible, are essential before planning the treatment.
Additionally, dental cast analysis measuring the buccolingual thickness of the alveolar basal bone is also useful
for prediction.
In distal movements of the maxillary molars, the
maxillary sinus is a major concern because tooth movement through bone-deficient areas is considered challenging and might reduce the alveolar bone height or
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the root length.22-24 Lindskog-Stokland et al23 in a
dog experiment and Wehrbein et al24 in a human biopsy
study described that root resorption and loss of osseous
supporting tissue occurred in the basal cortical bone of
the nasal sinus after translatory tooth movements.
They suggested that differentiation of osteoblasts is
required for compensatory subperiosteal bone apposition. However, the molar roots seemed to move into
the maxillary sinus without any serious root resorption,
even though the sinus seemed to be between the molar
roots in the our patient. Several clinical reports also
demonstrated the possibility of tooth movement into
the sinus.25,26 A recent study provided histologic
evidence that the sinus wall is a dynamic structure that
responds favorably to mechanical stress, such as tooth
movement.27 Therefore, the possibility of tooth movement into the sinus under suitable and safe conditions
should ultimately contribute to expanding the limits of
orthodontic treatment.
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Fig 11. Cephalometric tracings at pretreatment (black lines), posttreatment (red lines), and 5-year
postretention (green lines) superimposed on A, the sella-nasion plane at sella; B, the anterior palatal
contour; and C, the mandibular plane at menton.
Maxillary group distalization improved the horizontal open bite and provided adequate anterior guidance.
Extraction of the pathologic mandibular first molars
and succeeding molar mesialization could make the
mandibular dentition intact, avoiding any prosthetic restorations. Moreover, the maxillary left central and right
lateral incisors were restored with zirconia jacket crowns
after tooth whitening. This interdisciplinary approach, a
combination of orthodontic and restorative treatment,
significantly improved the patient's dental esthetics
and function, contributing to the increase of her quality
of life.
In this patient, the occlusion was stable, and little
relapse occurred during the 5-year retention period,
even though a large amount of molar distalization
was achieved with miniscrew anchorage. A recent longitudinal study with pendulum appliances for distalization showed that first molars were distalized for
4 mm with 10 of tipping, but almost half of the patients experienced relapse during the succeeding multibracket treatment.28 In our patient, the distalized
molars were initially tipped back but controlled well
during the finishing and detailing phase. Control of
distal tipping after molar distalization might be 1
important key for the stability of the distalized dentition. In addition, the mandibular plane angle did not
increase during active orthodontic treatment and
was also stable during the retention period. With these
simple molar distalizing mechanics with inerradicular
screws, the distalized maxillary molars can be slightly
intruded.16,17 As a result, the mandibular plane angle
can be stabilized even though the molars are
extremely distalized. The strict vertical control might
also be important to prevent relapses. However, no
authors have evaluated the long-term stability of
molar distalization with interradicular miniscrews.
Further studies are required to confirm their retention
and stability.
CONCLUSIONS
Interradicular miniscrews are useful to distalize the
maxillary dentition for correcting a Class II malocclusion.
With this new strategy, group distalization with miniscrews can make the treatment simpler with greater predictability.
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American Journal of Orthodontics and Dentofacial Orthopedics