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Coordinating bracket torque and incisor inclination

Part 2: Reproducibility and statistical measures of the torque coordination angle (TCA)

Koordination von Brackettorque und Schneidezahninklination

Teil 2: Reproduzierbarkeit und statistische Kennwerte des TCA („torque coordination angle“)

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Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie Aims and scope Submit manuscript

Abstract

Purpose

To determine the reproducibility and statistical measures of the torque coordination angle (TCA).

Methods

A total of 107 final cephalograms and corresponding casts were included, all reflecting treatment outcomes that met high qualitative standards, one of them being a Peer Assessment Rating (PAR) score of ≤3. Based on these records, the TCA was measured as a parameter to identify differences related to tooth morphology and bracket position between the torque-relevant reference plane at the bracket base and the long axis of a tooth. All measurements were performed on upper and lower central incisors (U1 and L1).

Results

Several reproducibility assessments for the TCA measurements yielded good results, including objectivity at 1.26 ± 0.81° (U1) or 1.41 ± 1.18° (L1), examiner reliability at 1.30 ± 0.97° (U1) or 1.25 ± 0.82° (L1), and method reliability at 1.80 ± 1.13° (U1) or 1.53 ± 1.07° (L1). The statistical measures revealed a high degree of interindividual variability. With bracket placement 4.5 mm (U1) or 4.0 mm (L1) above the incisal edge, the differences between the maximum and minimum TCA values were similarly large in both jaws (21.0° for U1 or 20.0° for L1), given mean TCA values of 24.6 ± 3.6° (U1) or 22.9 ± 4.3° (L1). Moving the bracket placement from 3.5 to 5.5 mm (U1) or from 3.0 to 5.0 mm (L1) changed the mean TCA values by 4.5° (U1) or 3.2° (L1).

Conclusions

The TCA is a suitable cephalometric parameter to identify differences related to tooth morphology and bracket placement. Given its high interindividual variability, the fixed torque value of a specific bracket system should not be expected to produce the same incisor inclinations across patients.

Zusammenfassung

Zielsetzung

Gegenstand der Untersuchung war die Ermittlung der Reproduzierbarkeit (Objektivität, Reliabilität) des TCA („torque coordination angle“) und seiner statistischen Kennwerte.

Methoden

Integriert in die Studie wurden insgesamt 107 FRS(Fernröntgenseiten)-Abschlussaufnahmen und die dazu gehörigen Abschlussmodelle von Patienten, deren Behandlungsergebnisse einen hohen qualitativen Standard aufwiesen (PAR[Peer Assessment Rating]-Index ≤3, u. a.). An diesem Material wurde der TCA bestimmt. Dieser Winkel ist ein Parameter, mit dem sich morphologische und klebepunktbedingte Unterschiede zwischen einer torquerelevanten Bezugsebene (Bracketbasis) und den Zahnlängsachsen oberer (U1) und unterer (L1) mittlerer Incisivi bestimmen lassen.

Ergebnisse

Die Verlässlichkeit des TCA wurde durch verschiedene Analysen bestätigt. Objektivität: MW 1,26 ± 0,81° (U1), MW 1,41 ± 1,18° (L1); Untersucherreliabilität: MW 1,30 ± 0,97° (U1), MW 1,25 ± 0,82° (L1); Verfahrensreliabilität: MW 1,80 ± 1,13° (U1), MW 1,53 ± 1,07° (L1). Die statistischen Kennwerte zeigten eine hohe Variabilität im interindividuellen Vergleich von ∆max 21° (U1), ∆max 20° (L1). Die Mittelwerte für die Klebepositionen 4,5 mm (U1) bzw. 4 mm (L1) betrugen 24,6 ± 3,6° bzw. 22,9 ± 4,3°. Veränderungen der Höhe des Klebepunktes zwischen 3,5 und 5,5 mm (U1) bzw. zwischen 3 und 5 mm (L1) resultierten in mittleren Veränderungen des TCA von 4,5° (U1) bzw. von 3,2° (L1).

Schlussfolgerungen

Der TCA ist ein Parameter, mit dessen Hilfe sich die morphologischen und klebepunktbedingten Unterschiede von oberen und unteren mittleren Incisivi im FRS-Bild erfassen lassen. Aufgrund seiner großen Variabilität im interindividuellen Vergleich kann angenommen werden, dass der fixe Torquewert eines einzelnen Bracketsystems nicht geeignet ist, patientenübergreifend eine identische Schneidezahninklination zu erreichen.

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Authors and Affiliations

  1. Orthodontic Practice, Teichstr. 24, 34130, Kassel, Germany

    H. Sino, B. Zimmer, I. Schelper, S. Schenk-Kazan & F. Streibelt

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  1. H. Sino
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  2. B. Zimmer
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Correspondence to B. Zimmer.

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H. Sino, B. Zimmer, I. Schelper, S. Schenk-Kazan and F. Streibelt declare that they have no competing interests.

Ethical standards

All studies on humans described in the present manuscript were carried out with the approval of the responsible ethical standards and in accordance with national law and the Helsinki Declaration of 1975 (in its current, revised form). Informed consent was obtained from all patients included in studies.

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Sino, H., Zimmer, B., Schelper, I. et al. Coordinating bracket torque and incisor inclination. J Orofac Orthop 79, 235–243 (2018). https://doi.org/10.1007/s00056-018-0130-8

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