Effect of Archwires on Simultaneous Intrusion and Retraction in Orthodontic Tooth Movement in Maxilla and Mandible During Extraction Space Closure with Miniscrew Sliding Mechanics by Finite Element Method

Abstract

Introduction: Finite element method (FEM) can anticipate visualization of tissue responses through observation of areas of stress created from applied orthodontic mechanics. The present study with the help of FEM elucidated how and why the archwire size affects long-term tooth movement in miniscrew sliding mechanics.

Materials and Method: Digitalized maxillary and mandibular model with first premolar extraction spaces bilaterally with all other permanent teeth present were included. Retraction forces of 150 g and intrusion forces of 60 g were applied on maxillary and mandibular anterior teeth; using nickel-titanium (NiTi) closed coil springs by means of mini-implants and retraction hook. Geometry of 3D finite element model of maxilla and mandible was constructed from a CBCT scan image of the skull and GEOMAGIC modelling software was used to convert geometric models into finite element models. The study included three simulation models for both maxilla and mandible using three different archwire dimensions: (a) 0.021 x 0.025” SS (b) 0.019 x 0.025” SS (c) 0.016 x 0.022” SS.

Results: On force application, model 1, 2 and 3 of maxilla showed tipping and torque of 1.3° & 0.19°, 1.6° & 0.22° and 2.7° & 0.37° respectively. The model 1, 2 and 3 of mandible showed tipping and torque of 0.42° & 0.077°, 0.53° & 0.082° and 0.96° & 0.110°. The intrusion & extrusion shown by model 1, 2 and 3 of maxilla was 4.96 E-03mm & 4.44 E-03mm, 5.38 E-03mm & 5.53 E-03mm and 7.51 E-03mm & 9.72 E-03mm respectively. The intrusion & extrusion shown by model 1, 2 and 3 of mandible was 1.46E-03mm & 42.61E-03mm, 1.57E-03mm & 4.17E-03mm and 1.92E-03mm & 5.46E-03mm respectively.

Conclusion: The decrease in arch wire size result in increase in tipping angle, torque angle, intrusion and retraction.Conclusion:

Fetal spleen growth follows a predictable and significant pattern with increasing gestational age. These normative morphometric values provide a critical anatomical reference for fetal development assessments and may assist in prenatal diagnostics, anatomical research, and forensic evaluations.