Investigation of effective intrusion and extrusion force for maxillary canine using finite element analysis

Abstract

Orthodontic tooth movement is mainly regulated by the biomechanical responses of loaded periodontal ligament (PDL). We investigated the effective intervals of orthodontic force in pure maxillary canine intrusion and extrusion referring to PDL hydrostatic stress and logarithmic strain. Finite element analysis (FEA) models, including a maxillary canine, PDL and alveolar bone, were constructed based on computed tomography (CT) images of a patient. The material properties of alveolar bone were non-uniformly defined using HU values of CT images; PDL was assumed to be a hyperelastic–viscoelastic material. The compressive stress and tensile stress ranging from 0.47 to 12.8 kPa and 18.8 to 51.2 kPa, respectively, were identified as effective for tooth movement; a strain 0.24% was identified as the lower limit of effective strain. The stress/strain distributions within PDL were acquired in canine intrusion and extrusion using FEA; root apex was the main force-bearing area in intrusion–extrusion movements and was more prone to resorption. Owing to the distinction of PDL biomechanical responses to compression and tension, the effective interval of orthodontic force was substantially lower in canine intrusion (80–90 g) than in canine extrusion (230–260 g). A larger magnitude of force remained applicable in canine extrusion. This study revised and complemented orthodontic biomechanical behaviours of tooth movement with intrusive–extrusive force and could further help optimize orthodontic treatment.

Keywords:

• Orthodontics
• intrusion– extrusion movements
• biomechanical responses
• finite element analysis

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the High-level Talent Science Foundation of Ningbo Polytechnic under Grant number RC201806; the National Natural Science Foundation of China under Grant number 51775506; the Zhejiang Provincial Natural Science Foundation of China under Grant number LY18E050022; the Public Welfare Technology Application Research Project of Zhejiang Province, China, under Grant numbers LGG19E050022 and 2017C33115 and the open foundation of Zhejiang Provincial Top Key Discipline of Mechanical Engineering of Hangzhou Dianzi University.