LAUSR

Abstract Objective Approximately 50% patients with a deep bite possess anatomically extruded mandibular canines. The objective of this study was to specify the required toe ( θ ) of the vertical segment of a cantilever from the distal aspect to achieve pure intrusion of a mandibular canine with a segmented arch in lingual orthodontics. Additionally, the optimum magnitude of the required intrusive force by a cantilever was determined assuming non-linear, hyper-elastic behaviour of periodontal ligament (PDL). Methods The geometrical model of a mandibular canine tooth was developed and the mathematical equation was devised to evaluate θ (positive value: toe-in, negative value: toe-out) based on certain input parameters. To verify this numerical study by finite element analysis (FEA), total eight different positions of point of force application ( P f ) on bracket top (occlusal) surface were considered based on different values of input parameters. Results The results were displayed in terms of nature of tooth movement and Von-Mises (equivalent) stresses generated in the PDL. Additionally, the optimum magnitude of the required intrusive force within the biological limit of a mandibular canine was determined from FEA considering the strength of PDL and factor of safety. Conclusions The numerical study was developed to compute the value of required toe angle ( θ ) of the vertical segment of a cantilever for different morphologies of a mandibular canine as well as different positions of P f . From FEA, the optimum range of an intrusive force within the biological limit of a mandibular canine was found to be 20–30 g.