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ANNALES ACADEMIAE MEDICAE STETINENSIS
ROCZNIKI POMORSKIEJ AKADEMII MEDYCZNEJ W SZCZECINIE
2013, 59, 2, 90–93
Joanna Janiszewska-Olszowska, Alina Socha1, Paulina Bińczak
The use of cortical screw anchorage for closing a space
resulting from the loss of a lower molar – a case report
Zastosowanie zakotwienia kortykalnego do zamknięcia
przestrzeni powstałej po utracie pierwszego dolnego
trzonowca – opis przypadku
Katedra i Zakład Stomatologii Ogólnej Pomorskiego Uniwersytetu Medycznego w Szczecinie
al. Powstańców Wlkp. 72, 70-111 Szczecin
Kierownik: dr hab. n. med. Katarzyna Grocholewicz
1
Studium Doktoranckie przy Katedrze i Zakładzie Propedeutyki i Fizykodiagnostyki Stomatologicznej
Pomorskiego Uniwersytetu Medycznego w Szczecinie
al. Powstańców Wlkp. 72, 70-111 Szczecin
Kierownik: prof. dr hab. n. med. Krystyna Lisiecka-Opalko
Streszczenie
incisor retraction, as well as for the protraction of posterior segments in order to close spaces without retracting
anterior teeth. A patient, aged 16 was reported in whom
a miniscrew of 9.5 mm length and 2 mm dimension was
inserted distal to the lower left second premolar 2 months
after extracting the first molar with periapical bone lesion
after failed endodontic treatment. The lower third molar
was mesialised using direct anchorage and a power arm
to minimize mesial tipping. The space closed within 20
months, followed by a spontaneous eruption of the adjacent third molar. This treatment method constitutes a good
alternative to third molar autotransplantation, allowing the
avoidance of the risk of surgical procedure.
Mikrośruby ortodontyczne są tymczasowymi implantami zapewniającymi zakotwienie szkieletowe, które
może być wykorzystywane do cofania siekaczy, jak również do mezjalizacji zębów bocznych w celu zamknięcia
przestrzeni bez cofania zębów przednich. W pracy opisano 16­‍‑letnią pacjentkę, która wskutek powikłań zapalenia tkanek okołowierzchołkowych i niepowodzenia leczenia kanałowego utraciła pierwszy dolny lewy trzonowiec.
Dwa miesiące później, za drugim dolnym przedtrzonowcem lewym wprowadzono miniśrubę o długości 9,5 mm
i średnicy 2 mm. Drugi dolny trzonowiec został przesunięty
doprzednio z wykorzystaniem zakotwienia bezpośredniego
i dźwigni do zmniejszenia nachylenia mezjalnego. Przestrzeń K e y w o r d s: minimplant – miniscrew – skeletal anchorzostała zamknięta w przeciągu 20 miesięcy, po czym nastąage.
piło wyrznięcie trzeciego trzonowca. Ta metoda leczenia
stanowi dobrą alternatywę dla autotransplantacji trzeciego
trzonowca, pozwalając uniknąć interwencji chirurgicznej.
Introduction
H a s ł a: miniimplant – miniśruba – zakotwienie szkieleOrthodontic anchorage microscrews are temporary
towe.
implants providing skeletal anchorage, without the need
for patient compliance. Possible insertion sites include, in
the maxilla: the area below the nasal spine, the palate, the
Summary
alveolar process, the infrazygomatic crest, and the retromolar area. In the mandible, microscrews can be inserted
Orthodontic microscrews are temporary implants pro- into the alveolar process, the retromolar area, and the manviding skeletal anchorage, which may be used for en­‍‑masse dibular symphysis [1, 2, 3].
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The use of cortical screw anchorage
a)
b)
c)
d)
Fig. 1. Plaster models before treatment initiation: a) anterior occlusion; b) occlusion of the right side; c) occlusion of the left side; d) dental arches
They can be used for en­‍‑masse incisor retraction, as well
as for protraction of posterior segments in order to close
spaces without retracting anterior teeth [4]. In patients with
periodontally compromised dentition they offer anchorage
potential for tooth movement, sometimes constituting the
only possibility of orthodontic treatment [1].
Orthodontic miniscrews can be used as direct or indirect
anchorage. Some systems require pilot drilling, although
self­‍‑drilling systems, thanks to an extremely fine and sharp
screw apex, have the advantage of perforating the cortical
bone, thus taking less chair time [4]. Some screws are available with different neck lengths for various implant sites [1].
The head of the mini­‍‑implant can be designed for one­‍‑point
contact with a hole through the neck, a hook, a button or
a bracket. The first screws of the Aarhus Anchorage System
were characterized by a bracket slot on the implant head,
which allowed use as direct or indirect anchorage. The patent for this design was granted to the Aarhus Mini­‍‑Implant
in 1997. The alloy used for the Aarhus Mini­‍‑Implant is
Ti6AL­‍‑4V ELI acc ASTM F 136­‍‑02a. The diameter of the
threaded portion of miniscrews was 1–2 mm [5].
Possible complications can be a failure of the mini­
‍‑implant caused by improper site selection, contact with
a tooth root [6], lack of primary stability, gingival inflammation, or screw breakage on removal [7].
Fig. 2. Panoramic radiograph
Case report
A female patient, aged 16, was seeking treatment due
to the failure of root canal treatment of her lower left first
molar. Intraoral examination revealed good occlusion with
minor crowding of the lower front teeth (Fig. 1 a–d). On the
panoramic radiograph a periapical bone lesion was apparent around the roots of the lower left first molar (Fig. 2).
The maxillary and mandibular third molars were present,
with a visible lack of space and slightly oblique inclination.
Cephalometric analysis by Segner and Hasund revealed
a neutral sagittal and vertical configuration with ANB = 2.4°,
ML­‍‑NL = 24.3° and Index = 81.9% (Fig. 3).
The treatment plan was to extract the affected lower
first molar, and to move the second molar mesially. In order
to avoid retracting the lower incisors, a cortical screw, Aarhus
Anchorage System (Medicon, Tuttlingen, Germany), with
a length of 9.5 mm and dimension of 2 mm was inserted
Fig. 3. Lateral head cephalogram
distal to the lower left second premolar 2 months after
extracting the first molar. The surgery was proceeded transmucosally, after pilot predrilling with an Aarhus Anchorage drill. Brackets (Discovery, Dentaurum, Germany) with
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Joanna Janiszewska-Olszowska, Alina Socha, Paulina Bińczak
a)
b)
c)
Fig. 4. Occlusion during treatment; visible Class III tendency: a) anterior occlusion; b) occlusion of the right side; c) occlusion of the left side
a)
b)
c)
Fig. 5. Occlusion on the day of debonding: a) anterior view; b) occlusion of the right side; c) occlusion of the left side
a)
b)
d)
c)
e)
Fig. 6. Occlusion 2 years after treatment cessation: a) anterior view; b) occlusion of the right side; c) occlusion of the left side;
d) upper dental arch; e) lower dental arch
a 0.022 slot were bonded. A molar tube was bonded to the
lower right first molar, and the left second molar was banded.
The first archwire was 0.016 nickel­‍‑titanium (Rematitan,
Dentaurum, Germany), used to level the dental arches. The
space was closed using direct anchorage and a power arm
to minimize mesial tipping. After a month the screw became
slightly mobile, and was screwed in and became stable
again. However, the following month it had to be replaced by
a new one. After 7 months of treatment a Class III tendency
became apparent. Therefore, for a month an elastic chain
was attached to the canine (Fig. 4 a–c). After 18 months the
screw was removed and the remaining space was closed by
the use of the elastic chain. After 7 months of the finishing phase, the patient missed a visit and did not come for
5 months. When she came back the fixed appliance was
removed, followed by bonding of a fixed retainer (Fig. 5 a–c).
Two years after treatment cessation the lower left third
molar had completely erupted, and the extraction space
opened by 1 mm. However, on the other side, the third molar
had partially erupted, whereas both upper third molars had
reached occlusion. The lower midline had shifted 2 mm
to the left (Fig. 6 a–e).
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The use of cortical screw anchorage
Discussion
An alternative treatment plan for the described patient
could be a transplantation of the lower third molar into the
extraction site after removing the first molar. Tooth transplantation is a surgical procedure including the removal of
the impacted third molar with resulting swelling, oedema,
and haematoma formation [8]. Deviant root anatomy and
difficult extraction causing damage to the periodontal ligament may be an important obstacle. Since the most significant success determinant factor in terms of transplant survival is the continued vitality of the periodontal membrane,
this procedure is technique­‍‑sensitive: it requires atraumatic
extraction of the donor tooth and its immediate transfer
to the recipient site without injury to the periodontal ligament. In cases where the periodontal ligament is traumatized during transplantation, external root resorption
and ankylosis is often noted. Another important limitation
may constitute inadequate alveolar width at the donor site,
thus occlusal and periapical radiographs of the donor tooth
should be used to determine its labiolingual and mesiodistal dimensions.
The highest success rates have been reported when
premolars were transplanted to the maxillary incisor
region [9]. Kvint et al. report a 69% success rate when mandibular third molars were transplanted, e.g. 11 of the 16 transplanted teeth, three had to be removed and one survived [9].
The anchorage alternative was to use intermaxillary
elastics. However, this approach would require bonding the
upper dental arch, increasing the cost of treatment. Patient
cooperation would be necessary and treatment time would
be longer due to the extrusive component of Class II elastics. Moreover, molar extrusion would create the risk of
bite opening.
The disadvantage of a thick screw such as the Aarhus
screw is the risk of root contact if inserted between the
roots, which results in screw loosening [10]. However, in
this case the screw was inserted in the toothless alveolar
process, so the screw loosening was probably caused by
altered bone metabolism due to healing in the extraction
site. In the study by Luzi et al. [11] the rate of the Aarhus
anchorage screw loss in the mandible was 8%. The Aarhus
Anchorage System was in this case used with a pilot predrilling, which might have compromised stability. However,
self drilling systems have an enhanced risk of breakage,
which may require surgical removal [4]. The head design
of the Bracket­‍‑head and One­‍‑point­‍‑head systems is being
technically modified in order to achieve an optimum for
the connection with orthodontic attachments. The previous
Aarhus Anchorage system has now been replaced by a new
generation of Aarhus self­‍‑drilling screws.
The screw was loaded immediately with light forces,
which is not considered a risk factor of implant failure, e.g.
loss or mobility [11]. It has been found that the decisive
parameter for mini­‍‑implant stability is the cortical thickness.
When the cortical bone is thinner, the mobility becomes
increasingly dependent on the Young’s modulus of the cancellous bone.
The strength of the screw is optimized by using a slightly
tapered conical shape and a solid head with a screwdriver
slot, since a hollow neck, although it facilitates the insertion of a ligature, weakens the neck. A bracket­‍‑like head
design offers the advantage of three­‍‑dimensional control,
and allows the screw to be consolidated with a tooth to serve
as indirect anchorage. In this case, the screw was used for
direct anchorage without a connecting wire, so the bracket
slot on the screw head was not used for wire insertion.
A slight space opening visible in a 2­‍‑year follow­‍‑up
could be due to incomplete root uprighting of the lower
second molar. However, due to poor cooperation the treatment could not be continued.
Conclusions
It can be concluded that using cortical screw anchorage for molar mesialisation constitutes a safe and efficient
way of closing extraction spaces without retracting anterior
teeth, allowing the avoidance of excessive surgery or prosthetic restoration. It may also allow for unimpeded eruption of a retained third molar, and thus constitutes a good
treatment alternative for patients with compromised third
molars and impacted wisdom teeth.
References
1. Melsen B.: Overview mini­‍‑implants: where are we? J Clin Orthod.
2005, 39 (9), 539–547.
2. Miedzik M., Syryńska M., Sporniak­‍‑Tutak K.: Implanty w ortodoncji – nowe możliwości leczenia – na podstawie piśmiennictwa. Czas
Stomatol. 2006, 59 (9), 662–669.
3. Panek B., Matthews­‍‑Brzozowska T., Kawala B.: Współczesne koncepcje
leczenia ortodontycznego pacjentów dorosłych z częściowym brakiem
zębów. Dent Med Probl. 2005, 42 (4), 647–650.
4. Baumgaertel S., Razavi M.R., Hans M.G.: Mini­‍‑implant anchorage for
the orthodontic practitioner. Am J Orthod Dentofacial Orthop. 2008,
133 (4), 621–627.
5. Dijakiewicz M., Soroka­‍‑Letkiewicz B., Szycik V., Dijakiewicz J.: Ortoimplanty i standardowe implanty śródkostne w leczeniu ortodontycznym
na podstawie piśmiennictwa. Implantoprotetyka. 2004, 5 (1), 15–20.
6. Wiechmann D., Meyer U., Büchter A.: Success rate of mini­‍‑ and micro­
‍‑implants used for orthodontic anchorage: a prospective clinical study.
Clin Oral Implants Res. 2007, 18 (2), 263–267.
7. Kravitz N.D., Kusnoto B.: Risks and complications of orthodontic miniscrews. Am J Orthod Dentofacial Orthop. 2007, 131, Suppl. 4, 43–51.
8. Kaczmarek U.: Autotransplantacja zębów. Dent Med Probl. 2006, 43
(2), 277–281.
9. Kvint S., Lindsten R., Magnusson A., Nilsson P., Bjerklin K.: Autotransplantation of teeth in 215 patients. Angle Orthod. 2010, 80 (3),
446–451.
10. Berens A., Wiechmann D., Dempf R.: Mini­‍‑ and micro­‍‑screws for temporary skeletal anchorage in orthodontic therapy. J Orofac Orthop.
2006, 67 (6), 450–458.
11. Luzi C., Verna C., Melsen B.: A prospective clinical investigation of the
failure rate of immediately loaded mini­‍‑implants used for orthodontic
anchorage. Prog Orthod. 2007, 8 (1), 192–201.