Morphometric analysis of dental arch form changes in class II patients treated with clear aligners

Morphometrische Analyse von Veränderungen der Zahnbogenform bei mit transparenten Alignern behandelten Klasse-II-Patienten



The purpose of this study was to evaluate the arch form changes in class II Caucasian patients treated with Invisalign® (Align Technology, San José, CA, USA).


A total of 27 class II patients, for whom a maximum of 4 mm arch expansion was planned, were selected. Both maxillary and mandibular digital casts were compared at three different times: pretreatment (T0), accepted set-up (T1), and retention phase (T2). Each digital model was imported into GOM Inspect© software (GOM GmbH, Braunschweig, Germany) to identify teeth crown facial axis (FA) and cusp points to create a coordinate system. In each model the origin of the coordinates was located at the contact point of central incisors and a system of Cartesian axes was constructed. Using the FA points, an average arch form was obtained for each clinical step and then the following comparisons were performed for each class group: T0–T1, T0–T2, and T1–T2.


T1 showed wider maxillary and mandibular dental arches compared to T0 with maximum movements observed in the premolar regions (maximum movement 1.94 mm for tooth 15; P < 0.0001). In the T1–T2 comparison, a more buccal position of tooth 22, tooth 23, and tooth 24 (maximum movement 0.56 mm; P < 0.05) and a more lingual position of tooth 37 (maximum movement 0.81 mm; P < 0.01), tooth 36, and tooth 47 were observed at T1 with respect to T2.


Although Invisalign® treatment resulted in a significant increase in arch width according to the prescription, some of the outcomes were different than those planned especially in relation to the final position of the lower molars.



Ziel dieser Studie war es, die Veränderungen der Bogenform bei kaukasischen Klasse-II-Patienten, die mit Invisalign® (Align Technology, San José/CA, USA) behandelt wurden, zu untersuchen.


Insgesamt wurden 27 Klasse-II-Patienten ausgewählt, für die maximal 4 mm Zahnbogenerweiterung geplant waren. Sowohl der Ober- als auch der Unterkiefer-Digitalabdruck wurden zu 3 verschiedenen Zeitpunkten verglichen: Vor Behandlung (T0), akzeptiertes Set-up (T1) und Retentionsphase (T2). Jedes digitale Modell wurde in die Software GOM Inspect© (GOM GmbH, Braunschweig, Deutschland) importiert, um die faziale Achse (FA) der Zahnkrone sowie die Höckerpunkte zu identifizieren und ein Koordinatensystem zu erstellen. In jedem Modell wurde der Ursprung der Koordinaten am Kontaktpunkt der zentralen Schneidezähne lokalisiert und ein System von kartesianischen Achsen wurde erstellt. Unter Verwendung der FA-Punkte wurde für jeden klinischen Schritt eine durchschnittliche Bogenform erhalten und dann die folgenden Vergleiche für jede Klassengruppe durchgeführt: T0–T1, T0–T2 und T1–T2.


T1 zeigte im Vergleich zu T0 breitere Ober- und Unterkiefer-Zahnbögen mit maximalen Bewegungen im Bereich der Prämolaren (maximale Bewegung 1,94 mm für Zahn 15; p < 0,0001). Im T1–T2-Vergleich wurden bei T1 eine weiter bukkale Position von Zahn 22, Zahn 23 und Zahn 24 (maximale Bewegung 0,56 mm; p < 0,05) und eine mehr linguale Position von Zahn 37 (maximale Bewegung 0,81 mm; p < 0,01), Zahn 36 und Zahn 47 in Bezug auf T2 beobachtet.


Obwohl die Invisalign®-Behandlung zu einer signifikanten Erhöhung der Bogenbreite gemäß der Prescription führte, waren einige der Ergebnisse anders als geplant, insbesondere in Bezug auf die Endposition der unteren Molaren.

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Corresponding author

Correspondence to Dr. Simone Parrini DDS.

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Conflict of interest

A. Deregibus, L. Tallone, G. Rossini, S. Parrini, M. Piancino and T. Castroflorio declare that they have no competing interests.

Ethical standards

The research protocol was approved by the local ethics board (No. 3732015, CIR Dental School, Turin University). All subjects (or their parents) gave written informed consent.

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Deregibus, A., Tallone, L., Rossini, G. et al. Morphometric analysis of dental arch form changes in class II patients treated with clear aligners . J Orofac Orthop 81, 229–238 (2020).

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  • Orthodontic treatment
  • Malocclusion, Angle class 2
  • Orthodontic appliances, removable
  • Invisalign
  • Virtual casts


  • Kieferorthopädische Behandlung
  • Angle-Klasse-II-Malokklusion
  • Herausnehmbare kieferorthopädische Apparaturen
  • Invisalign
  • Virtuelle Abdrücke