Optimum pure intrusion of a mandibular canine with the segmented arch in lingual orthodontics.

TLDR: An optimum toe (Θ) of the vertical segment of a cantilever from the distal aspect is specified to achieve pure intrusion of a mandibular canine with the segmented arch in lingual orthodontics (LiO).

Abstract: Background Approximately 50% patients with a deep bite possess anatomically extruded mandibular canines Objective The objective of this study was to specify an optimum toe (Θ) of the vertical segment of a cantilever from the distal aspect to achieve pure intrusion of a mandibular canine with the segmented arch in lingual orthodontics (LiO) Methods The geometrical model of a mandibular canine was developed to compute the required values of Θ (positive values - toe-in, negative values - toe-out) Different positions of the cantilever attachment on the lingual bracket top (occlusal) surface were considered according to different heights (h) from the cusp of a canine ie 2, 3, 4 and 5 mm in each case of horizontal distance (x) from canine surface ie 2 and 3 mm In x=2mm case, the required values of Θ at h=2,3,4 and 5mm were -5°, 0°, +6° and +11° respectively While, in x=3mm case, the required values of Θ at h=2,3,4 and 5mm were 0°, +5°, +12° and +17° respectively Results In finite element analysis (FEA), the computed values of Θ were verified by displaying the results of a mandibular canine movement in the form of vectors of nodal displacements along with undeformed and deformed models Conclusions In the cases of x=2mm and 3mm, no toe angles were required at heights h=3mm and 2mm respectively Hence, these can be considered as better positions of the cantilever attachment than others