A comparison of three-dimensional stress distribution and displacement of naso-maxillary complex on application of forces using quad-helix and nickel titanium palatal expander 2 (NPE2): a FEM study

Biomechanical performance of ATOZ expander: Finite-element analysis

INTRODUCTION

Microimplant-assisted rapid palatal expansion appliances have been used for the treatment of orthodontic patients with maxillary deficiency. A new design named ATOZ (applicable from A to Z) was recently introduced to expand the scope of treatment in early permanent dentition. The objective of this study was to analyze the biomechanical performance of the ATOZ expander with various microimplants configurations using finite-element method.

METHODS

Nine ATOZ models were designed based on the number of microimplants configurations on the palate. For skeletal maturation, stage B midpalatal suture (MPS) maturation classification was chosen. A displacement along the sagittal axis, parallel to the MPS, of 0.15 mm was applied on each side of the device to simulate a 1 jackscrew turn of 0.3 mm.

RESULTS

Configurations 1, 2, 6, and 7 achieved a quasi-parallel skeletal movement with a uniform distribution of displacement in the maxilla. The highest posterior nasal spine to anterior nasal spine ratio of 95.95% was found with configuration 6, indicating an optimum quasi-parallel expansion. For configuration 2, microimplants 1 and 2 exhibited stresses of 619.18 MPa and 656.49 MPa, respectively, whereas microimplants 7 and 8 showed stresses of 609.64 MPa and 658.30 MPa, respectively. Maximum stress in zygomatic bone was 0.69 MPa. Higher stresses were more distributed in the zygomaticofrontal suture than in zygomaticotemporal and zygomaticomaxillary sutures.

CONCLUSIONS

In terms of posterior nasal spine to anterior nasal spine ratio, skeletal-to-dental ratio, and MPS deformation, ATOZ with configurations 1, 2, and 6 outperform other configurations, and thus, they can be recommended for correction of maxillary deficiency in patients with skeletal maturation of stage B or earlier.

Finite element analysis of maxillary orthodontic therapies with variable alveolar bone grafts under occlusal forces in patient with unilateral cleft lip and palate

Objective

To investigate the biomechanical effects of maxillary orthodontic treatment on different alveolar bone grafting positions loaded with occlusal forces in an unilateral cleft lip and palate (UCLP) patient.

Methods

Finite element analysis was employed to simulate clinical scenarios more accurately by loading with occlusal forces on 8 bone-grafted models during maxillary orthodontic treatment. Displacement and von Mises stress pattern during maxillary protraction, expansion, and combined protraction and expansion were analyzed.

Results

The seven bone-grafted models exhibited significantly smaller horizontal displacements at the non-cleft side landmarks during maxillary protraction and expansion compared to non-bone grafted models. Additionally, alveolar cleft bone grafted in the upper 1/3 and middle 1/3 exhibited greater asymmetry displacement and stress under maxillary protraction and expansion.

Conclusion

The study highlights the necessity of considering occlusal forces in finite element study on orthodontic therapies for UCLP patients. The upper 1/3 and middle 1/3 bone graft conditions may require secondary bone graft supplementation to ensure the effectiveness of maxillary orthodontic treatment.

Effects of novel microimplant-assisted rapid palatal expanders manufactured by 3-dimensional printing technology: A finite element study

INTRODUCTION

The expansion effects of several new microimplant-assisted rapid palatal expanders (MARPEs) manufactured by 3-dimensional printing technology were evaluated by finite element analysis (FEA). The aim was to identify a novel MARPE suitable for treating maxillary transverse deficiency.

METHODS

The finite element model was established using MIMICS software (version 19.0; Materialise, Leuven, Belgium). First, the appropriate microimplant insertion characteristics were identified via FEA, and several MARPEs with the above insertion patterns were manufactured by 3-dimensional printing technology. Then, the stress distribution and displacement prediction of the 4 MARPEs and hyrax expander (model E) were evaluated via FEA: bone-borne (model A), bone-tooth-borne (model B), bone-mucous-borne (model C), bone-tooth-mucous-borne (model D).

RESULTS

Monocortical microimplants perpendicular to the cortical bone on the coronal plane resulted in better expansion effects. Compared with a conventional hyrax expander, the orthopedic expansion of each of the 4 MARPEs was far larger, the parallelism was greater, and the posterior teeth tipping rate was lower. Among them, the expansion effects of models C and D were the best; the von Mises peak values on the surfaces of the microimplants were smaller than those of models A and B.

CONCLUSIONS

This study may demonstrate that the 4 MARPEs obtained more advantageous orthopedic expansion effects than a hyrax expander. Models C and D obtained better biomechanical effects and had better primary stability. Overall, model D is the recommended expander for treating maxillary transverse deficiency because its structure acts like an implant guide and is beneficial for the accurate insertion of the microimplant.

Biomechanical evaluation of the unilateral crossbite on the asymmetrical development of the craniofacial complex. A mechano-morphological approach

BACKGROUND AND OBJECTIVE

The occlusion effect on the craniofacial development is a controversial topic that has attracted the interest of many researchers but that remains unclear, mainly due to the difficulties on measure its mechanical response experimentally. This mechano-morphological relationship of the craniofacial growth is often explained by the periosteal and capsular matrices of the functional matrix hypothesis (FMH); however, its outcomes have not been analytically demonstrated yet. This computational study aims, therefore, to analytically demonstrate the mechano-morphological relationship in the craniofacial development of children with unilateral crossbite (UXB) using the finite element (FE) method.

METHODS

The craniofacial complex asymmetry of ten children, five of whom exhibit UXB, was 3D-analysed and compared with the biomechanical response computed from a FE analysis of each patient's occlusion. Due to the complexity of the geometry and the multitude of contacts involved, the inherent limitations of the model were evaluated by comparing computed occlusal patterns with those recorded by an occlusal analysis on 3D printed copies.

RESULTS

Comparison's outcomes proved the reliability of our models with just a deviation error below 6% between both approaches. Out of validation process, computational results showed that the significant elongation of mandibular branch in the contralateral side could be related to the mandibular shift and increase of thickness on the crossed side, and particularly of the posterior region. These morphological changes could be associated with periodontal overpressure (>4.7 kPa) and mandibular over deformation (0.002 ε) in that side, in agreement with the periosteal matrix's principles. Furthermore, the maxilla's transversal narrowing and the elevation of the maxillary and zygomatic regions on the crossed side were statistically demonstrated and seem to be related with their respective micro displacements at occlusion, as accounted by their specific capsule matrices. Our results were consistent with those reported clinically and demonstrated analytically the mechano-morphological relationship of children's craniofacial development based on the FMH's functional matrices.

CONCLUSIONS

This study is a first step in the understanding of the occlusion's effect on the craniofacial development by computational methods. Our approach could help future engineers, researchers and clinicians to understand better the aetiology of some dental malocclusions and functional disorders improve the diagnosis or even predict the craniofacial development.

Torque Comparison Between Two Passive Self-Ligating Brackets with Respect to Interbracket Wire Dimensions and Types: A Finite Element Analysis

Objective:

This study aimed to analyze the expression of torque between 2 passive self-ligating brackets by simulating different clinical situations using finite element analysis.

Material and Methods:

Two passive self-ligating brackets, that is, Damon Q (Ormco, Glendora, California) and Smart Clip (3M Unitek, Monrovia, California), were 3D modeled using micro-computed tomography. ANSYS V14.5 software was used for analysis. Archwire and bracket interactions were simulated to measure torque expression by changing wire alloys (stainless steel [SS] and titanium molybdenum [TMA]) and interbracket dimensions.

Results:

Damon Q brackets generated higher torque values compared to Smart Clip brackets with both SS and TMA wires. Damon Q brackets generated the highest torquing moment of 25.72 Nmm and 7.45 Nmm, while Smart Clip brackets generated 22.25 Nmm and 7.31 Nmm with 0.019 × 0.025″ SS and TMA wires, respectively, at an interbracket distance of 12 mm. Torquing moments decreased for Damon Q and Smart Clip brackets when wire length increased from 12 mm to 16 mm.

Conclusion:

Damon Q with 0.019 × 0.025″wires exhibited superior torquing characteristics as compared to Smart Clip brackets with similar archwires.

Finite element analysis of human skull bone adaptation to mechanical loading

Bones self-optimize their mechanical behavior in response to mechanical stimulus. The objective of this research was to develop an integrated bone remodeling and stress binning algorithms into a finite element environment to elucidate the evolution of the bone properties as a function of loading. The bone remodeling algorithm was used to calculate the change in the density and elastic modulus based on the strain energy stimulus. The stress-binning procedure seeks to assign the properties to each element based on the levels of stress from the previous cycle, eliminating pseudo-lazy-zoning and stress dilation effects. The developed algorithms were used to analyze the response skull to loading associated with orthodontic devices. Specifically, a load was applied between the roots of the canine teeth and the first premolars while constraining the foramen magnum. Full-field contours of the displacement, strain, and strain energy were extracted after each remodeling cycle at nine commonly cephalometric landmarks. The results indicate that the overall mechanical response and the associated properties reached a steady-state behavior after nearly 50 cycles of applying the algorithm, where different zones within the skull exhibited unique evolution based on the locations from the loading and boundary sites. When approaching this steady-state condition, it was found that the upper incisor displacement is reduced by 72%, and the density is reduced by almost 7.5%. The finite element approach can be used in defining the treatment process by dynamically changing the loads. Future research will focus on integrating the time-dependent behavior of the bone.

Application of bioengineering devices for stress evaluation in dentistry: the last 10 years FEM parametric analysis of outcomes and current trends

INTRODUCTION

Dentistry, therefore implantology, prosthetics, implant prosthetics or orthodontics in all their variants, are medical and rehabilitative branches that have benefited greatly from these methods of investigation to improve the predictability of rehabilitations. We will examine the Finite Element Method and Finite Element Analysis in detail. This method involves the simulation of mechanical forces from an environment with infinite elements, the real one, to a simulation with finite elements.

EVIDENCE ACQUISITION

The study searched MEDLINE databases from 2008 to 2018. Human use of FEM in vitro studies reported a contribution on oral rehabilitation through the use of FEM analysis. The initial search obtained 296 citations. After a first screening, the present revision considered the English-language works referred to human application of the FEM published in the last 10 years. Finally, 34 full texts were available after screening.

EVIDENCE SYNTHESIS

The ultimate aim of this review is to point out all the progress made in the field of bioengineering and therefore, thanks to this, in the field of medicine. Instrumental investigations such as FEM are an excellent tool that allows the evaluation of anatomical structures and any facilities for rehabilitation before moving on to experimentation on animals, so as to have mechanical characteristics and satisfactory load cycle testing.

CONCLUSIONS

FEM analysis contributes substantially to the development of new technologies and new materials in the biomedical field, being able to perform a large number of simulations without the need for patients or to perform human tests. Thanks to the 3D technology and to the reconstructions of both the anatomical structures and eventually the alloplastic structures used in the rehabilitations it is possible to consider all the mechanical characteristics, so that they can be analyzed in detail and improved where necessary. It is possible thanks to these methods to know what are the ideal characteristics of a material to promote an oral rehabilitation, so we know the characteristics, it remains only to take a step in the field of the industry for the construction of materials close to these characteristics.

A Comparative Three-Dimensional Finite Element Study of Two Space Regainers in the Mixed Dentition Stage

Objectives  This study aims to compare the stress distribution and displacement that resulted from the use of a Gerber space regainer and sagittal distalizer using three-dimensional finite element analysis.

Materials and Methods  Three-dimensional simulated models of the appliances were developed using a software. The forces applied by the two appliances were 3N (tipping) and 15N (bodily), respectively. Displacement and von Mises stress on the compact and cancellous bone, periodontal ligament (PDL), crowns of the mandibular first, second permanent molars, and deciduous canines were calculated. Stress distribution and displacement values were measured via linear static analysis.

Results  Gerber space regainer showed greater displacement than that produced by the sagittal distalizer at the first permanent molar. However, such displacement was less at the other tested points when compared with that delivered by sagittal distalizer. The stresses created by Gerber appliance were higher in the crown and PDL of the deciduous canine than the crown of the first permanent molar crown.

Conclusions  Gerber appliance generates more distal force and less stress concentration on the crown of the mandibular first permanent molar than that created by the sagittal distalizer. On the other hand, stress concentrations produced by Gerber space regainer are found to be more on the crown and PDL of the deciduous canine. Therefore, it can be concluded that the use of Gerber appliance needs more anchorage.

Simulation of orthodontic force of archwire applied to full dentition using virtual bracket displacement method

OBJECTIVE

Orthodontic force simulation of tooth provides important guidance for clinical orthodontic treatment. However, previous studies did not involve the simulation of orthodontic force of archwire applied to full dentition. This study aimed to develop a method to simulate orthodontic force of tooth produced by loading a continuous archwire to full dentition using finite element method.

METHOD

A three-dimensional tooth-periodontal ligament-bone complex model of mandible was reconstructed from computed tomography images, and models of brackets and archwire were built. The simulation was completed through two steps. First, node displacements of archwire before and after loading were estimated through moving virtual brackets to drive archwire deformation. Second, the obtained node displacements were loaded to implement the loading of archwire, and orthodontic force was calculated. An orthodontic force tester (OFT) was used to measure orthodontic force in vitro for the validation.

RESULTS

After the simulation convergence, archwire was successfully loaded to brackets, and orthodontic force of teeth was obtained. Compared with the measured orthodontic force using the OFT, the absolute difference of the simulation results ranged from 0.5 to 22.7 cN for force component and ranged from 2.2 to 80.0 cN•mm for moment component, respectively. The relative difference of the simulation results ranged from 2.5% to 11.0% for force component, and ranged from 0.6% to 14.7% for moment component, respectively.

CONCLUSIONS

The developed orthodontic force simulation method based on virtual bracket displacement can be used to simulate orthodontic force provided by the archwire applied to full dentition.

Stress Distribution Patterns within Viscero- and Neurocranium during Nasoalveolar Molding: a Finite Element Analysis

Background

The purpose of this study was to evaluate the stress distribution patterns within the viscero- and neurocranium of neonates during nasoalveolar molding.

Methods

Finite element models of 3 different healthy neonates at different times of life (date of birth, 4 weeks, and 3.5 months) were generated on the basis of computed tomography scans. A validated workflow, including segmentation, meshing, setting of boundary conditions, and implementation of a bone density-dependent material model, was carried out for each model. A small and a large unilateral alveolar and hard palatal cleft were virtually cut in each model. The stress distribution pattern in each model was then analyzed by using Ansys APDL.

Results

Convergence analysis validated the results. The virtual experiments at the date of birth showed a stress pattern above a previously defined threshold value of 30,000 Pa in the ipsilateral naso-orbital-complex, frontal sinus, and the anterior fossa of the base of the skull, with von Mises values > 35,000 Pa. Stress patterns at the age of 4 weeks and 3.5 months showed reduced von Mises values at < 15,000 Pa.

Conclusions

Nasoalveolar molding therapy is a safe presurgical treatment modality without significant influence on the viscero- and neurocranium of neonates. Treatment, considering the stress distribution at the naso-orbital-complex and anterior fossa of the base of the skull, should begin in the second week of life, and treatment initiation of preterm infants should be adapted respectively.

Establishment of a finite element model of a neonate's skull to evaluate the stress pattern distribution resulting during nasoalveolar molding therapy of cleft lip and palate patients

Nasoalveolar Molding (NAM) is associated with ambivalent acceptance regarding effectiveness and unknown long-term results. Our purpose was to analyze the stress distribution patterns within the viscero- and neurocranium of neonates during the first phase of NAM therapy. A finite element (FE) model of a healthy four-week-old neonate was generated, derived from a computed tomography scan allowing the implementation of a bone-density-dependent material model. The influence of dental germs with variable material properties, the cleft width and area of expected force application were analyzed in a worst-case scenario. The resulting stress distribution patterns for each situation were analyzed using the software Ansys APDL. The established FE model was verified with a convergence analysis. Overall, stress patterns at the age of four weeks showed von Mises stress values below 60.000 Pa in the viscero- and neurocranium. The influences of the allocation of material properties for the dental germs, the area of force application, and the cleft width were negligible. A workflow to simulate the stress distribution and deformation in neonates attributable to various areas of force application has been established. Further analyses of the skulls of younger and older neonates are needed to describe the stress distribution patterns during NAM therapy.

Extensiometric analysis of strain in craniofacial bones during implant-supported palatal expansion

Palatal expansion has several orthodontic and orthopedic applications, such as increasing maxillary transverse dimensions and correcting maxillary atresia, oral breathing, and skeletal cross-bites. Little is known about the strain to which craniofacial bones are submitted when a palatal expander is loaded. The objectives of the present work were to propose a new palatal bone-borne titanium device (expansion screw), to determine patterns of strain distribution in craniofacial bones during palatal expansion and to show the clinical results of a new palatal expander supported by implants. For in vitro testing, the palatal expander supported by two commercially pure titanium (cp Ti) implants was inserted parallel to the median palatine suture of four dry adult human skulls. Uniaxial and triaxial strain gauges were attached to craniofacial bones and connected to a signal acquisition system. An expansion screw was turned and strain data were collected during palatal expansion. The results showed that the bone strain distribution in craniofacial bones loaded by the palatal bone-borne titanium device was complex: the strain was tensile in the palatine cortical bone and compressive in pterygopalatine processes, nasal bones, and orbital floor. The maximum compressive strain occurs in the upper portion of the pterygopalatine processes and the strain changes from compressive to tensile in the zygomatic process. The experimental results suggest that the bone strain due to the palatal expander is distributed over all craniofacial bones and that the upper portions of pterygopalatine processes are the main sites of resistance to palatal expansion. The new palatal expander supported by two cp Ti implants proposed was employed on adult patient as an illustrative report, where adequate palatal expansion was achieved. The new protocol proposed was less invasive, risky, painful and costless for the correction of moderate maxillary transverse deficiency.