A Novel Biomechanical Model Assessing Orthodontic, Continuous Archwire Activation in Incognito Lingual Braces

The purpose of this research is to develop a virtual, orthodontic, continuous archwire model for assessing a lingual bracket system. A digital model of a maxilla, periodontal ligament, and dentition was constructed from human computed tomography data. Virtual lingual and facial brackets were placed on the maxillary left central incisor through first premolar. An intrusive tooth movement was utilized to test the model and compare labial and lingual biomechanics. The ANSYS 13.0 birth-death function simulated force interaction between the wire and brackets. The goal of placing labial and lingual bracket-wire systems on accurate anatomy including multiple teeth was achieved. Material property definitions had an effect on a finite element model. The birth-death computer technique simulated the clinical effects of placing an archwire in brackets and allowing forces to be transferred from the bracket-wire system to the surrounding dental structures. The lingual appliance has different biomechanical effects than the labial appliance

Evaluation of torque expression of four commercially available self-ligating brackets: A finite element study

This FEM study was carried out to investigate the torque expression of different self-ligating brackets and arch wire combinations on the tooth and its supporting structures. Two Active (Innovation-R and Time) and Passive (Smart Clip 3 and Damon3MX) self-ligating bracket systems were selected and one conventional (Ovation) bracket system served as control. Upper Right Central Incisor Stainless Steel Roth Prescription bracket with slot dimension of 0.022 x 0.028 inches was used in all the groups. The brackets were tested against three S.S. archwire dimensions (0.017 x 0.025, 0.019 x 0.025 and 0.021 x 0.025 inches). A 3-dimensional model of the right maxillary central incisor and its supporting structures was generated from a Computed Tomography scan of a dry human skull by a CAD/CAE program. The brackets were scanned and 3-dimensional models were designed with Comet 5 White Light Scanner. The close geometric diagram for the bracket, tooth and its supporting structures was prepared using Ansys Workbench Version 11. The bracket of the maxillary central right incisor was rotated from the neutral position by a total of 20 degrees. The angle of engagement and the resultant forces (stress concentration) were evaluated at 0mm, 4mm, 8mm and 12mm from the apex for different archwire-bracket combinations were recorded using the same software. This FEM study was carried out to investigate the torque expression of different self-ligating brackets and arch wire combinations on the tooth and its supporting structures. Two Active (Innovation-R and Time) and Passive (Smart Clip 3 and Damon3MX) self-ligating bracket systems were selected and one conventional (Ovation) bracket system served as control. Upper Right Central Incisor Stainless Steel Roth Prescription bracket with slot dimension of 0.022 x 0.028 inches was used in all the groups. The brackets were tested against three S.S. archwire dimensions (0.017 x 0.025, 0.019 x 0.025 and 0.021 x 0.025 inches). A 3-dimensional model of the right maxillary central incisor and its supporting structures was generated from a Computed Tomography scan of a dry human skull by a CAD/CAE program. The brackets were scanned and 3-dimensional models were designed with Comet 5 White Light Scanner. The close geometric diagram for the bracket, tooth and its supporting structures was prepared using Ansys Workbench Version 11. The bracket of the maxillary central right incisor was rotated from the neutral position by a total of 20 degrees. The angle of engagement and the resultant forces (stress concentration) were evaluated at 0mm, 4mm, 8mm and 12mm from the apex for different archwire-bracket combinations were recorded using the same software

3D FEM comparison of lingual and labial orthodontics in en masse retraction

BACKGROUND: The aim of this study was to compare displacements and stress after en masse retraction of mandibular dentition with lingual and labial orthodontics using three-dimensional (3D) finite element models (FEM).METHODS: A 3D FEM of each lower tooth was constructed and located as appropriate to Roth's prescription. The 0.018-in. GAC Roth Ovation labial and Ormco 7th Generation lingual brackets were virtually bonded to the lower teeth and threaded with 0.018 × 0.025- and 0.016 × 0.022-in. SS labial (Tru-Arch form, small size) and lingual (mushroom) archwires. En masse retraction was simulated by applying 300 g of distal force from the canine to the second premolar on the 0.016 × 0.022-in. SS labial and lingual archwires. The type of finite element used in the analysis was an eight-noded brick element. The Algor program (Algor Inc., Pittsburgh, PA, USA) was used to calculate the strains and displacements at each nodal point.RESULTS: Lingual tipping and extrusion of the anterior dentition occurred with both archwires. At the premolars and first molars, intrusion, lingual movements, and lingual tipping were seen with the labial archwire, while intrusion was accompanied by labial movements, mesial tipping, and buccal rotation with lingual mechanics.CONCLUSIONS: Lingual vs. labial bracket placement influences the pattern of tooth movement, but the stress that occurs around the teeth can be accurately mapped using a 3D FEM model

Stress Distribution Pattern in Roots of Incisors with Various Root Resorptions: A Finite Element Study

Objectives Root resorption is a dangerous side effect in orthodontics, and maxillary incisors are at the highest risk for root resorption. It is important to understand optimal force considerations for patients with altered root lengths.The purpose of this study was to investigate the effects of root length on stress distribution on roots by means of three-dimensional finite element method (FEM).Methods Three dimensional FEM models of maxillary central and lateral incisors were made. Then, root length of the incisors was changed in the increments of 1 mm from 0-4 mm. Applying 50 g (0.5 N) of force perpendicular to the tooth crown simulated uncontrolled tipping. Stresses and strains for each model were calculated and Pearson correlation coefficient was used to analysis the data.Results There were significant correlations between root length of incisors and maximum stress in PDL. In the centrals with various root lengths, maximum stress was between 0.010884 and 0.056520 MPa, and in the laterals, it was between 0.027297 and 0.221040 MPa. By reducing root length of incisors, the maximum stress in buccal apical (r= 0.933,p<0.001 and 0.995, p<0.001 prospectively) and lingual crestal areas (r= 0.974 p=0.005 and 0.992, p=0.001  respectively) were reduced.Conclusion Although in lateral incisors, stress at the lingual crestal area was more than buccal apical area, in central incisors with more than 2 mm resorption, the stress distribution of buccal apical was higher. Therefore, in maxillary central incisors with more root resorption, force control might be even more critical

Computational design and engineering of polymeric orthodontic aligners

Transparent and removable aligners represent an effective solution to correct various orthodontic malocclusions through minimally invasive procedures. An aligner-based treatment requires patients to sequentially wear dentition-mating shells obtained by thermoforming polymeric disks on reference dental models. An aligner is shaped introducing a geometrical mismatch with respect to the actual tooth positions to induce a loading system, which moves the target teeth toward the correct positions. The common practice is based on selecting the aligner features (material, thickness, and auxiliary elements) by only considering clinician's subjective assessments. In this article, a computational design and engineering methodology has been developed to reconstruct anatomical tissues, to model parametric aligner shapes, to simulate orthodontic movements, and to enhance the aligner design. The proposed approach integrates computer-aided technologies, from tomographic imaging to optical scanning, from parametric modeling to finite element analyses, within a 3-dimensional digital framework. The anatomical modeling provides anatomies, including teeth (roots and crowns), jaw bones, and periodontal ligaments, which are the references for the down streaming parametric aligner shaping. The biomechanical interactions between anatomical models and aligner geometries are virtually reproduced using a finite element analysis software. The methodology allows numerical simulations of patient-specific conditions and the comparative analyses of different aligner configurations. In this article, the digital framework has been used to study the influence of various auxiliary elements on the loading system delivered to a maxillary and a mandibular central incisor during an orthodontic tipping movement. Numerical simulations have shown a high dependency of the orthodontic tooth movement on the auxiliary element configuration, which should then be accurately selected to maximize the aligner's effectiveness

Investigation of frictional resistance on orthodontic brackets when subjected to variable moments

Friction and binding occur in orthodontics during sliding mechanics. This paper evaluated the influence of a variable moment, simulating mastication, placed at the bracket-archwire interface to determine its effects on friction. Friction of self-ligating brackets were also compared to stainless steel and ceramic brackets. Six archwires were combined with four brackets. Friction (static, kinetic and dynamic) and load (dynamic and apparent stiffness) were measured. Dynamic friction was the frictional force that occurred when the applied force was variable (dynamic load). The results showed that static and kinetic friction were similar while dynamic friction was statistically greater. The Minitwin and Transcend 6000 brackets produced greater friction than the In-Ovation and Damon 2 brackets for all archwires, except with the 19 x 25TMA archwire. The Damon 2 bracket yielded the least friction. Dynamic friction was momentarily reduced below kinetic friction; thus, releasing the binding and enabling tooth movement