Download A Creative Spring Design to Force Erupt Labially

Iran J Ortho. 2014 December; 9(3):e3936.
DOI: 10.17795/ijo-3936
Case Report
Published online 2014 December 30.
A Creative Spring Design to Force Erupt Labially Impacted Maxillary Canine
Using Single Mini Implant
1
2,*
1
Nasrin Farhadian, Amirfarhang Miresmaeili, and Vahid Mollabashi
1Department of Orthodontic, Faculty of Dentistry, Hamadan University of Medical Sciences, Hamadan, IR Iran
2Department of Orthodontic, Hamadan Dental Research Center, Hamadan University of Medical Sciences, Hamadan, IR Iran
*Corresponding author: Amirfarhang Miresmaeili, Department of Orthodontic, Hamadan Dental Research Center, Hamadan University of Medical Sciences, Hamadan, IR Iran.
Tel: +98-8138381084, Fax: 98-8138381085, E-mail: [email protected]
Received: August 29, 2014; Accepted: August 29, 2014
Introduction: Complications to force eruption of impacted teeth may arise from several reasons including ankylosis, dilaceration, and/
or some barriers in the eruption pathway. Treatment time prolongation without obvious clinical progress gradually decreases the patient
compliance. In this paper we present a non-conventional method to forced eruption of an impacted maxillary canine.
Case Presentation: A 21-year-old girl presented with missing of teeth No 17, 12, 22, 27, 38, 37, 47, 48 and labially impaction of both maxillary
canine was prepared for treatment through apically position flap for exposure of the both canines. Using standard edgewise 0.18 appliance
and conventional elastic traction the right maxillary canine erupted to its normal position after about 18 months but the other tooth had
not responded favorably to this technique. There was no signs of ankylosis, a titanium bone screw was placed in the labial cortical bone
and mesial of the malposed canine. A spring is made of 0.017” × 0.025” SS wire with two helixes that delivered about 100 g force and 400
gr.mm activation moment to labial bracket on malposed canine crown. The force exerted on mini implant will be balanced with a force
and moment on malposed tooth very similar to type IV Burston classification. After about 5 months the tooth had reached to its final
occlusal position.
Conclusions: The appliance used for this patient brought the impacted canine into the arch without any more force on the neighbor
teeth. Two point contact of the spring arm by bending the wire over the head of the mini implant made it possible to apply buccolingual
crown torque.
Keywords: Tooth Impacpion; Canine; CBCT; Orthodontic Tooth Movement
1. Introduction
Resistance of impacted tooth to forced eruption may
arise from several reasons including ankylosis, dilaceration, complex path of eruption and/or some barriers in
the eruption pathway. Ankylosis of the canine and detrimental effects on incisor roots is predictable if orthodontic treatment don’t be initiated at early age (1). Apart from
ankylosis that usually has no other choice except extraction, other conditions may produce resistance to forced
eruption and could produces some important side effects
like prolonged treatment time, hazard to neighbor teeth,
caries and bone loss of other teeth (2-4). Treatment time
prolongation without obvious clinical progress gradually decreases the patient compliance. The main question
would be “Is it possible to continue treatment without
conventional fixed appliance and with a minimum compliance method?”
1.1. Spring Design and Mechanics
Skeletal anchorage, which provides a nearly stationary
base, has become a routine treatment adjunct for many
kinds of tooth movement (5, 6).
To erupt labialy impacted maxillary canine, a spring
is made of 0.017” × 0.025” SS wire with two helixes that
deliver about 100 g force and 400 gr.mm activation
moment to labial bracket on malposed canine crown
(Figure 1). The upper horizontal arm of the spring is inserted in the mini implant hole. When the other arm
inserted in the bracket slot it produces a vertical force
and a moment for mesial root movement. The force
exerted on mini implant will be balanced with a force
and moment on malposed tooth very similar to type IV
Burston classification (7). To increase the moment the
spring arm at bracket level could be bended in such a
way that when it is placed into the bracket slot produce
an additional pre-activation moment which produces a
condition comparable to Type V Burston classification
(Figure 2 A). This bend has little opposite moment on
mini screw which could screw it in to the bone if had
any effect at all (Figure 2 B). Such a bend could not work
Copyright © 2014, Iranian Journal of Orthodontics. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial
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Farhadian N et al.
on the same situation on right maxillary canine because it can cause loosening of the mini implant. This
spring design provides a force system with M/F > 4 for
extrusion and mesial root movement instead of extrusion with uncontrolled and unpredictable root movement.
Advantages of using this spring design with single mini
implant could be summarized as:
1. No more need to fixed appliance in eruption phase,
2. Prevention of side effects on neighbor teeth,
3. Concomitant use of force and moment to erupt the
tooth between neighbor teeth,
4. Continuous force system instead of interrupted force
by elastic traction.
poration, Seoul, Korea) was placed in the labial cortical
bone and mesial of the malposed canine at an angle
of about 60 degree to the bone surface. After about 5
months the tooth had reached to its final occlusal position. The mechanic was effective in bringing the tooth
to normal occlusion by extrusion with mesial root
movement (Figure 6). Figure 7 demonstrated the final
result.
2. Case Presentation
The patient was a 21-year-old girl presented with missing of teeth No 17, 12, 22, 27, 38, 37, 47, 48 and labially
impaction of both maxillary canine (Figure 3). Apically
position flap was used for exposure of the both canines.
Using standard edgewise 0.18 appliance and forced
eruption with conventional elastic traction the right
maxillary canine erupted to its normal position after
about 18 months but the other tooth had not responded
favorably to this technique. Position and morphology
of left impacted canine was determined by CBCT (Figure 4). Since oral surgeon found no ankylosis and the
patient lost her compliance and adjacent teeth showed
moderate resorption we had decided to continue the
eruption using mini implant with our special designed
spring (Figure 5). Accordingly a titanium bone screw
with a hole in head (2 mm × 10 mm, Jail medical cor-
Figure 1. Schematic Diagram of Creative Spring Design: Forced Eruption
and Concomitant Mesial Root Movement of Malposed Tooth Using Single
Mini Screw
Figure 2. A, preactivation bend; B, after putting the wire at bracket level. Mild bending at arrow could produce more momentum for root movement with
mild effect on mini implant which is in the same direction of screwing it in to the bone.
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Iran J Ortho. 2014;9(3):e3936
Farhadian N et al.
Figure 3. 21 Years Old Female Patient With Multiple Missing Teeth and Two Impacted Maxillary Canine Before Treatment
Figure 4. CBCT of the Left Maxillary Canine
Figure 5. Periapical Radiograph to Control the Position of Mini Implant
A, apical dilacerations was placed in the lateral wall of the nasal cavity. B,
The highlighted area shows the relation between nasal floor and root of
the canine tooth like the ring around the Saturn. Mesial root movement
need to remodel this dense cortical plate.
Yellow circle shows the dilacerations.
Iran J Ortho. 2014;9(3):e3936
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Farhadian N et al.
Figure 6. 3D Superimposition
A, before and after movement. B, determination of center of rotation to show the effectiveness of applied moment.
Figure 7. Patient 23 Months After Treatment
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Iran J Ortho. 2014;9(3):e3936
Farhadian N et al.
Figure 8. Use of the Same Mini Implant for Bucolingual Tooth Movement
A, preactivation: buccal force and buccal crown torque were both placed on spring. B, one month after activation.
3. Discussion
The major cause of being non-responsive to routine
forced eruption in left maxillary canine were blocking of
its crown by incisor root, close vicinity of its mid-root to
premolar root and apical curvature toward the mesial,
the same direction of required root movement. Moreover,
not only the root of the impacted canine was placed in the
lateral wall of the nasal cavity, it also passed through the
nasal floor so these dense cortical plates resisted against
translation of canine root through them (Figures 4 and 6).
The single force as used for the right canine by elastic
traction provides eruption and uncontrolled tipping
with movement of crown and the root in opposite direction. Dilaceration made tooth eruption parallel to the alveolar socket wall impossible and mesial root movement
was restricted by surrounding dense cortical plates, so
the easiest possible movement was pushing the canine
toward the premolar root.
The major advantage of this appliance was application
of moment concomitant with vertical force and it was
possible due to bracket placement in its normal position
immediately after exposure of the canine crown. This
provided controlled mesial root movement and eruption to normal position simultaneously. If there were no
dilacerations and we need lighter force, TMA wires could
be substituted for SS wire. They would have no need for
reactivation and reducing the frequency of patient visits
(8). The system can be applied at the start of treatment
which could reduce treatment time.
The appliance used for this patient brought the impacted canine into the arch without any more force
on the neighbor teeth. Removal of fixed appliance also
made the first premolar free to move away from the
path of eruption. Two point contact of the spring arm
by bending the wire over the head of the mini implant
made it possible to apply bucolingual crown torque
and movement by this spring (Figures 5 and 8).
Despite methods that used implant in palate for force erupIran J Ortho. 2014;9(3):e3936
tion of impacted teeth, labial implant was not faced with
masticatory forces from food on the edentulous ridge (9).
Disadvantage of this spring design include: mucosal
irritation on buccal side when there is no enough attached gingival (and poor oral hygiene), high failure rate
in adolescent and limited space for mini implant placement between canine crown and incisor root.
Authors’ Contributions
Nasrin Farhadian treated the case and designed the
mechanotherapy. Amirfarhang Miresmaeili treated the
case and designed the mechanotherapy, and also, he is
the corresponding author. Vahid Mollabashi prepared
the manuscript and figures.
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