Abstract
Objective
Can we correct dental midline discrepancies by systematic torque bends on all canines and premolars without extraction and mesiodistal tooth movement?
Patients and methods
Eight orthodontic patients (4 males, 4 females, mean age 31 years) presented a dental midline discrepancy of 2–4 mm, moderate deviation of the chin, no skeletal asymmetry, and a horizontal orientation of the occlusal plane in the frontal aspect. On the side where the mandible was shifted medially, asymmetric torque bends moved the antagonist canine and both premolar crowns buccally, while palatal crown torque was used on the maxillary canine and premolars on the other side. Lingual crown torque corrected the medially shifted canine and premolars in the mandibular dental arch, and buccal crown torque the laterally shifted lower canine and premolars.
Results
On average, torque effects altered the canine guidance by 6.5 ± 4.7°, the first premolar guidance by 7 ± 4.1°, and the second premolar guidance by 6.3 ± 3.7°. Correction of the dental midline shift averaged 1.6 ± 0.8 mm after the torque, and eliminated the midline discrepancy completely (n = 2) or partly (n = 6).
Conclusion
In this pilot study, asymmetric reciprocal torque represented a treatment option for midline corrections of approximately 2–4 mm and improvement in the chin position without mesiodistal tooth movement or extraction.
Zusammenfassung
Fragestellung
Sind dentale Mittellinienverschiebungen mittels systematischer Torquebiegungen an allen Eckzähnen und Prämolaren beherrschbar, nämlich ohne Extraktion und mesiodistale Zahnbewegung?
Patienten und Methodik
Acht Patienten (4 männliche, 4 weibliche, Durchschnittsalter 31 Jahre) mit Mittellinienverschiebungen von 2–4 mm, geringer Kinnabweichung ohne sonstige skelettale Asymmetrie, aber einer en face horizontalen Okklusionsebene, erhielten während ihrer festsitzenden Multibrackettherapie asymmetrische, progressive Torquebiegungen. Im Oberkiefer wurden die Eckzahn- und Prämolarenkronen einseitig mittels positivem Torque nach bukkal ausgerichtet, nämlich an jener Seite, auf der die antagonistischen Unterkieferfrontzähne medial verlagert waren. Kontralateral lenkte negativer Torque die Oberkiefereckzahn- und Prämolarenkronen nach palatinal. Im Unterkiefer bewegte negativer Torque die Eckzahn- und Prämolarenkronen auf der medial verlagerten Seite nach lingual, wohingegen positiver Torque auf der Gegenseite die unteren Eckzahn- und Prämolarenkronen weiter bukkal positionierte.
Ergebnisse
Die Torque-Effekte veränderten die Eckzahnführung durchschnittlich um 6,5° ± 4,7°, die funktionelle Höckerkontur der ersten Prämolaren um 7° ± 4,1° und die der zweiten Prämolaren um 6,3° ± 3,7°. Die Mittellinie verbesserte sich durchschnittlich um 1,6 ± 0,8 mm, wodurch sich die Mittellinieninkongruenz völlig (n = 2) oder partiell (n = 6) korrigieren ließ.
Schlussfolgerung
Im Pilotversuch stellte asymmetrischer reziproker Torque eine Behandlungsvariante ohne mesiodistale Zahnbewegungen und ohne Extraktion dar, um Mittellinienverschiebungen von 2–4 mm zu korrigieren und die Kinnposition zu verbessern.
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Onodera, K., Čelar, A. Midline correction by asymmetric reciprocal torque: a pilot study. J Orofac Orthop 73, 317–325 (2012). https://doi.org/10.1007/s00056-012-0089-9
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DOI: https://doi.org/10.1007/s00056-012-0089-9