Coordinating bracket torque and incisor inclination

Abstract

To determine the reproducibility and statistical measures of the torque coordination angle (TCA). Atotal of 107 final cephalograms and corresponding casts were included, all reflecting treatment outcomes that met high qualitative standards, one of them being aPeer Assessment Rating (PAR) score of ≤3. Based on these records, the TCA was measured as aparameter 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 atooth. All measurements were performed on upper and lower central incisors (U1 and L1). 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 ahigh 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). The TCA is asuitable cephalometric parameter to identify differences related to tooth morphology and bracket placement. Given its high interindividual variability, the fixed torque value of aspecific bracket system should not be expected to produce the same incisor inclinations across patients.