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Table 1 The torque angle values at the 0.5-mm increments and at the inflection point of the incisor in Figs. 1 and 2 are shown in this table. As the palatal CEJ of this incisor is located at the x coordinate point 7.70, the most cervical 0.5-mm increment is [P1 + 7.50]. Incremental subtractions were calculated for the successive 0.5-mm increments in the incisor part incisal to the inflection point and in the incisor part cervical to the inflection point. An incisor part containing an X number of 0.5-mm increments contains a number equal to X − 1 of incremental subtractions. Note the progressive decrease in torque angle values of the increments from P1 to inflection point and the opposite progressive increase in the torque angle values of the increments from inflection point to the most cervical calculated increment. An incremental subtraction had a negative value in the incisor part incisal to inflection point and a positive value in the incisor part cervical to it. The inflection point had the most negative torque angle value on PSC

From: The inflection point: a torque reference for lingual bracket positioning on the palatal surface curvature of the maxillary central incisor

  0.5 mm increment Torque angle value Incremental subtraction Number of incremental subtractions
Incisor part incisal to inflection point [P1] 3.26   6
[P1 + 0.50] − 0.10 − 3.36
[P1 + 1.00] − 4.61 −  4.51
[P1 + 1.50] − 10.85 − 6.24
[P1 + 2.00] − 19.53 − 8.68
[P1 + 2.50] − 30.86 − 11.33
[P1 + 3.00] − 42.21 − 11.35
  Inflection point [P1 + 3.46] − 46.67   
Incisor part cervical to inflection point [P1 + 3.50] − 46.63   8
[P1 + 4.00] −  41.54 5.09
[P1 + 4.50] − 32.68 8.86
[P1 + 5.00] − 24.37 8.31
[P1 + 5.50] − 17.71 6.66
[P1 + 6.00] − 9.24 8.47
[P1 + 6.50] 4.02 13.26
[P1 + 7.00] 21.41 17.39
[P1 + 7.50] 40.84 19.43