ThE uSE of CoRTICAl SCREw AnChoRAGE foR CloSInG A SPACE RESulTInG fRoM ThE loSS of A lowER MolAR – A CASE REPoRT

W dokumencie Annales Academiae Medicae Stetinensis = Roczniki Pomorskiej Akademii Medycznej w Szczecinie. 2013, 59, 2 (Stron 92-96)

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

Mikrośruby ortodontyczne są tymczasowymi implan-tami zapewniającymi zakotwienie szkieletowe, które może być wykorzystywane do cofania siekaczy, jak rów-nież do mezjalizacji zębów bocznych w celu zamknięcia przestrzeni bez cofania zębów przednich. W pracy opi-sano 16 -letnią pacjentkę, która wskutek powikłań zapale-nia tkanek okołowierzchołkowych i niepowodzezapale-nia lecze-nia kanałowego utraciła pierwszy dolny lewy trzonowiec.

Dwa miesiące później, za drugim dolnym przedtrzonow-cem 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 została zamknięta w przeciągu 20 miesięcy, po czym nastą-piło wyrznięcie trzeciego trzonowca. Ta metoda leczenia stanowi dobrą alternatywę dla autotransplantacji trzeciego trzonowca, pozwalając uniknąć interwencji chirurgicznej.

H a s ł a: miniimplant – miniśruba – zakotwienie szkiele-towe.

Summary

Orthodontic microscrews are temporary implants pro-viding skeletal anchorage, which may be used for en -masse

incisor retraction, as well as for the protraction of poste-rior 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 adja-cent third molar. This treatment method constitutes a good alternative to third molar autotransplantation, allowing the avoidance of the risk of surgical procedure.

K e y w o r d s: minimplant – miniscrew – skeletal anchor-age.

Introduction

Orthodontic anchorage microscrews are temporary 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 alveolar process, the infrazygomatic crest, and the retro-molar area. In the mandible, microscrews can be inserted into the alveolar process, the retromolar area, and the man-dibular symphysis [1, 2, 3].

THE USE OF CORTICAL SCREW ANCHORAGE 91

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

a) b) c) d)

Fig. 2. Panoramic radiograph

Fig. 3. Lateral head cephalogram

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 avail-able 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 pat-ent 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 -implant caused by improper site selection, contact with a tooth root [6], lack of primary stability, gingival inflam-mation, or screw breakage on removal [7].

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 appar-ent 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

distal to the lower left second premolar 2 months after extracting the first molar. The surgery was proceeded trans-mucosally, after pilot predrilling with an Aarhus Anchor-age drill. Brackets (Discovery, Dentaurum, Germany) with

92 JOANNA JANISZEWSKA-OLSZOWSKA, ALINA SOCHA, PAULINA BIńCZAK

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 finish-ing 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).

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)

a)

a)

d)

b)

b)

b)

e)

c)

c)

c)

Fig. 5. Occlusion on the day of debonding: a) anterior view; b) occlusion of the right side; c) occlusion of the left side

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

THE USE OF CORTICAL SCREW ANCHORAGE 93

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 trans-plantation 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 liga-ment may be an important obstacle. Since the most signifi-cant success determinant factor in terms of transplant sur-vival 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 lig-ament. In cases where the periodontal ligament is trau-matized 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 mesiodis-tal 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 man-dibular third molars were transplanted, e.g. 11 of the 16 trans-planted 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 elas-tics. 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 pre-drilling, 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 can-cellous 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 inser-tion 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 treat-ment could not be continued.

Conclusions

It can be concluded that using cortical screw anchor-age for molar mesialisation constitutes a safe and efficient way of closing extraction spaces without retracting anterior teeth, allowing the avoidance of excessive surgery or pros-thetic restoration. It may also allow for unimpeded erup-tion of a retained third molar, and thus constitutes a good treatment alternative for patients with compromised third molars and impacted wisdom teeth.

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A N N A L E S A C A D E M I A E M E D I C A E S T E T I N E N S I S

R O C Z N I K I P O M O R S K I E J A K A D E M I I M E D Y C Z N E J W S Z C Z E C I N I E 2013, 59, 2, 94–98

IWONA WRONKA1, IWONA TEUL2, JuSTynA MARChEwkA1, 3

ThE InfluEnCE of AGE AT MEnARChE on ThE PREvAlEnCE

of dISoRdERS of ThE MEnSTRuAl CyClE AMonG hEAlThy

W dokumencie Annales Academiae Medicae Stetinensis = Roczniki Pomorskiej Akademii Medycznej w Szczecinie. 2013, 59, 2 (Stron 92-96)