Displacement and force distribution of splinted and tilted mandibular anterior teeth under occlusal loads: an in silico 3D finite element analysis

Abstract

BackgroundFixed orthodontic retainers have numerous advantages, but it is not known whether they can exert pathological forces on supporting tissues around the splinted teeth. The purpose of this study was to investigate how the inclination of the lower anterior teeth can affect dental displacement and also change the direction of occlusal loads exerted to dental and its supporting tissues.MethodsFour three-dimensional finite element models of the anterior part of the mandible were designed. All the models contained the incisors and canines, their periodontal ligament layers (PDLs), the supporting bone (both spongy and cortical), and a pentaflex splinting wire placed in the lingual side of the teeth. Teeth inclination was considered to be 80° (model 1), 90° (model 2), 100° (model 3), and 110° (model 4) to the horizontal plane. The lower incisors were loaded with a 187-N vertical force. Their displacement patterns and the stress in their PDLs were evaluated.ResultsIn incisors with 80° of inclination, less than a 0.1-mm lingual displacement was seen on the incisal edge and a similar distance of displacement towards the labial was seen on their root apices. However, in models with 90°–110° of inclination, the incisal edge displaced labially between about 0.01 and 0.45 mm, while root apices displaced lingually instead. By increasing the angle of the teeth, the strain in the periodontal ligament increased from about 37 to 58 mJ. The von Mises stresses around the cervical and apical areas differed for each tooth and each model, without a similar pattern. Increasing the angle of the teeth resulted in much higher cervical stresses in the incisors, but not in the canines. In the lateral incisor, cervical stress increased until 100° of inclination but reduced to about half by increasing the angle to 110°. Apical stress increased rather consistently in the incisor and lateral incisors, by increasing the inclination. However, in the canines, apical stress reduced to about half, from the first to fourth models.ConclusionsIncreasing the labial inclination can mostly harm the central incisors, followed by the lateral incisors. This finding warns against long durations of splinting in patients with higher and/or patients with reduced labial bone thickness.

Influence of anterior teeth inclination on the strength of incisors with post and cores

“…The equivalent stresses in proclined teeth were concentrated palatally around the CEJ, and were 80% greater in dentine than in the properly positioned teeth. Similar results have been achieved by a study conducted by Gerami et al, 8 which showed that increasing the labial angle of the mandibular central incisors resulted in much higher cervical stresses in splinted and tilted teeth under occlusal loads. This situation may produce a cervical tooth fracture.…”

“…Occlusal loading of substantially proclined anterior teeth can have a traumatic effect on the surrounding tissues. 8 Higher inclination of anterior teeth results in higher stress in the tooth, Results. The lowest reduced stresses were recorded for the palatally inclined incisors (model A1).…”

Orthodontic Displacement and Stress Assessment: A Finite Element Analysis

“…In another finite element study, they had stated that there was a correlation between different inclinations of tooth to the rate of displacement and the von Mises stress generated in the PDL. 17 The reason for the maximum displacement in the premolars as compared with the lateral incisors in our models for the given clinical situation could be because root of the first premolar was comparatively short than the laterals and had only a single root instead of two roots, i.e., one buccal and one palatal. Added to that, the long axis of the first premolar and the lateral incisor to the occlusal plane differed.…”

“…This difference in the displacement may be due to the variations in the tooth size, morphology, the alveolar bone height, or even the teeth inclinations. 16,17 Tanne et al, 16 in their FEA study, had stated that root length and alveolar bone height affect the pattern of initial tooth displacements both in the center of resistance and the centers of rotation. In another finite element study, they had stated that there was a correlation between different inclinations of tooth to the rate of displacement and the von Mises stress generated in the PDL.…”

Mandible Integrity and Material Properties of the Periodontal Ligament during Orthodontic Tooth Movement: A Finite-Element Study

“…In the literature, FEM has been used for models with a single tooth [7][8][9], partial jawbone models with several teeth [10][11][12], and complete jawbone models with all teeth [13][14][15][16]. Additionally, these finite-element models have been used to explore the effects of the design and material properties of different orthodontic forces, brackets, and archwires on the biomechanical responses of the PDL during tooth movement.…”