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1.
Int J Oral Maxillofac Implants ; 36(1): 75-85, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33600526

RESUMEN

PURPOSE: This study evaluated the mechanical behavior of different configurations of the All-on-4 treatment concept designed with straight short (6-mm-length), straight standard (11-mm-length), or tilted standard (30-degree angled; 11-mm-length) posterior implants. MATERIALS AND METHODS: The All-on-4 configurations were performed in atrophic mandible models and consisted of anterior straight standard and posterior tilted standard implants (H1 model), anterior straight standard and posterior straight short implants (H2 model), and anterior and posterior straight standard implants (H3 model). Three oblique forces of 100 N were simulated in the posterior region of the prosthetic bar. The values of stress were obtained for the ductile materials using the von Mises equivalent stress (σvm) criteria. The stress peaks in the peri-implant bone crest were measured by the maximum (σmax) and minimum (σmin) principal stresses. The two-way analysis of variance (two-way ANOVA) and Tukey post hoc tests determined significant differences (P < .01) of stress values among the ductile materials (implant and prosthetic components). RESULTS: The use of tilted standard posterior implants (H1 model) showed the lowest values of σmax and σmin in the posterior region of the peri-implant bone area. On the other hand, the use of straight short (H2 model) or straight standard (H3 model) posterior implants significantly reduced the von Mises mean stresses in the bar screws, abutments, and abutment screws (P < .01). CONCLUSION: The higher odds of technical failures (screw fracture/loosening) may be expected when the All-on-4 configuration is performed with tilted standard posterior implants. Also, peri-implant bone overload may occur when the All-on-4 design is performed with straight short or straight standard posterior implants in atrophic mandibles.


Asunto(s)
Implantes Dentales , Diseño de Prótesis Dental , Prótesis Dental de Soporte Implantado , Análisis del Estrés Dental , Análisis de Elementos Finitos , Mandíbula/cirugía , Estrés Mecánico
2.
Stomatologiia (Mosk) ; 100(1): 7-10, 2021.
Artículo en Ruso | MEDLINE | ID: mdl-33528948

RESUMEN

OBJECTIVE: The aim of the study was to analyze a three-dimensional finite element model of a post-resection defect of the lower jaw, design and producing of an individual reconstructive plate, compare the stress-strain of this plate using standard reconstructive «CONMET¼ plate for stabilizing the lower jaw segments through a simulation of the chewing load. MATERIAL AND METHODS: The study was carried out on two identical finite elementary models with bone defects in the body of the lower jaw by fixing with a standard reconstructive «CONMET¼ plate and designed reconstructive plate. In order to simulate the biomechanical loads on the plates when chewing, an impact of force during the occlusal contact of the incisor was applied. The magnitude of the vertical load was equal to 150 N. The condylar processes were fixed in all three directions to prevent reaction forces in the temporomandibular joint. RESULTS: Comparative analysis of two fixation methods showed higher value of equivalent Von Mises stress in individual reconstructive plate than in standard plate. CONCLUSION: Individual reconstructive plate has better strength characteristics compared to the standard reconstructive «CONMET¼ plate.


Asunto(s)
Placas Óseas , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Estándares de Referencia , Estrés Mecánico
5.
Zhonghua Kou Qiang Yi Xue Za Zhi ; 56(2): 190-195, 2021 Feb 09.
Artículo en Chino | MEDLINE | ID: mdl-33557504

RESUMEN

Objective: To evaluate the biomechanical behaviors of different framework materials in implant-supported fixed mandibular prosthesis using three-dimensional finite element analysis. Methods: A model of implant-supported fixed mandibular prosthesis was established. The simulations were divided into six groups according to the framework materials: pure titanium, cobalt-chromium alloy, gold alloy, zirconia, polyether ether ketone (PEEK) and carbon fiber-reinforced PEEK. An oblique load of 300 N with a 75° angle to the occlusal plane was applied from the lingual side on the buccal cusps of the two premolars and the first molar teeth. The stresses on implants, surrounding bones and frameworks were analyzed and compared among the framework materials both quantitatively and qualitatively. Results: In implant-supported fixed mandibular prosthesis model, the highest stresses were located around the neck of the implants and cortical bone during oblique loading among six designs. In addition, the stresses were concentrated on the buccal and distal cortical bone around the implants of the posterior region. Stress values of implants and cortical bones from low to high were as follows: zirconia, cobalt-chromium alloy, pure titanium, gold alloy, carbon fiber-reinforced PEEK, PEEK. The von Mises stress values of implant and cortical bone in the first molar site of PEEK framework material were 44.96 and 29.13 MPa, while the von Mises stress values of implant and cortical bone in the first molar site of zirconia framework material were 21.29 and 17.79 MPa. The zirconia and medal framework materials were more advantageous in stress distribution around implants than PEEK framework material. Conclusions: In implant-supported fixed mandibular prostheses, biomechanical analysis showed that the zirconia and medal framework materials were more advantageous in stress distribution around implants than PEEK framework materials.


Asunto(s)
Implantes Dentales , Prótesis Mandibular , Diseño de Prótesis Dental , Prótesis Dental de Soporte Implantado , Análisis del Estrés Dental , Análisis de Elementos Finitos , Estrés Mecánico
6.
J Prosthet Dent ; 125(1): 138.e1-138.e8, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33393474

RESUMEN

STATEMENT OF PROBLEM: Mini implants (<3 mm in diameter) are being used as an alternative to standard implants for implant-retained mandibular overdentures; however, they may exhibit higher stresses at the crestal level. PURPOSE: The purpose of this finite element analysis study was to evaluate the biomechanical behavior (stress distribution pattern) in the mandibular overdenture, mucosa, bone, and implants when retained with 2 standard implants or 2 mini implants under unilateral or bilateral loading conditions. MATERIAL AND METHODS: A patient with edentulous mandible and his denture was scanned with cone beam computed tomography (CBCT), and a 3D mandibular model was created in the Mimics software program by using the CBCT digital imaging and communications in medicine (DICOM) images. The model was transferred to the 3Matics software program to form a 2-mm-thick mucosal layer and to assemble the denture DICOM file. A 12-mm-long standard implant (Ø3.5 mm) and a mini dental implant (Ø2.5 mm) along with the LOCATOR male attachments (height 4 mm) were designed by using the SOLIDWORKS software program. Two standard or 2 mini implants in the canine region were embedded separately in the 3D assembled model. The base of the mandible was fixed, and vertical compressive loads of 100 N were applied unilaterally and bilaterally in the first molar region. The material properties for acrylic resin (denture), titanium (implants), mucosa (tissue), and bone (mandible) were allocated. Maximum von Mises stress and strain values were obtained and analyzed. RESULTS: Maximum stresses of 9.78 MPa (bilaterally) and 11.98 MPa (unilaterally) were observed in 2 mini implants as compared with 3.12 MPa (bilaterally) and 3.81 MPa (unilaterally) in 2 standard implants. The stress values in the mandible were observed to be almost double the mini implants as compared with the standard implants. The stresses in the denture were in the range of 3.21 MPa and 3.83 MPa and in the mucosa of 0.68 MPa and 0.7 MPa for 2 implants under unilateral and bilateral loading conditions. The strain values shown similar trends with both implant types under bilateral and unilateral loading. CONCLUSIONS: Two mini implants generated an average of 68.15% more stress than standard implants. The 2 standard implant-retained overdenture showed less stress concentration in and around implants than mini implant-retained overdentures.


Asunto(s)
Implantes Dentales , Prótesis de Recubrimiento , Prótesis Dental de Soporte Implantado , Análisis del Estrés Dental , Retención de Dentadura , Análisis de Elementos Finitos , Humanos , Mandíbula/diagnóstico por imagen , Estándares de Referencia , Estrés Mecánico
7.
J Endod ; 47(3): 500-508, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-33359529

RESUMEN

INTRODUCTION: Although the maxillary first molar (MFM) has been frequently subjected to stress analysis in endodontic investigations, the available data about the effect of its oblique ridge are quite sparse. The aim of this study includes evaluating the effect of the residual oblique ridge on the stress distribution after preparing conservative access cavities. METHODS: Based on the cone-beam computed tomographic data, the model of an intact MFM and 5 cavity designs were prepared for endodontic treatment, which were consequently filled with gutta-percha and dental resin composite (6 total models). All models were subjected to 4 types of occlusal loading; finite element analysis via ABAQUS CAE software (Dassault Systemes, Vélizy-Villacoublay, France) was accomplished, whereas other software programs such as (Mimics Research Materialise, Leuven, Belgium) and 3-Matic Research (Materialise) were also incorporated in different stages for detecting stress distribution. RESULTS: The stress distribution on the MFM is not only dependent on the remaining width of the oblique ridge but also on the type of loading. The most stress on the cervical region was concentrated on the palatal root in some type of loading, whereas the least stress on the occlusal surface was recorded when the whole oblique ridge was replaced by the composite resin. CONCLUSIONS: When the occlusal contacts are occurring only on the palatal cusp, the stress distribution on the oblique ridge is noticeably affected by the cavity design.


Asunto(s)
Diente no Vital , Bélgica , Análisis del Estrés Dental , Análisis de Elementos Finitos , Francia , Humanos , Diente Molar/diagnóstico por imagen
8.
Microvasc Res ; 133: 104102, 2021 01.
Artículo en Inglés | MEDLINE | ID: mdl-33166578

RESUMEN

This study describes a computational algorithm to determine vascular permeability constants from time-lapse imaging data without concurrent knowledge of the arterial input function. The algorithm is based on "blind" deconvolution of imaging data, which were generated with analytical and finite-element models of bidirectional solute transport between a capillary and its surrounding tissue. Compared to the commonly used Patlak analysis, the blind algorithm is substantially more accurate in the presence of solute delay and dispersion. We also compared the performance of the blind algorithm with that of a simpler one that assumed unidirectional transport from capillary to tissue [as described in Truslow et al., Microvasc. Res. 90, 117-120 (2013)]. The algorithm based on bidirectional transport was more accurate than the one based on unidirectional transport for more permeable vessels and smaller extravascular distribution volumes, and less accurate for less permeable vessels and larger extravascular distribution volumes. Our results indicate that blind deconvolution is superior to Patlak analysis for permeability mapping under clinically relevant conditions, and can thus potentially improve the detection of tissue regions with a compromised vascular barrier.


Asunto(s)
Algoritmos , Permeabilidad Capilar , Procesamiento de Imagen Asistido por Computador , Microcirculación , Modelos Cardiovasculares , Imagen de Lapso de Tiempo , Animales , Velocidad del Flujo Sanguíneo , Análisis de Elementos Finitos , Humanos , Análisis Numérico Asistido por Computador , Factores de Tiempo
9.
PLoS One ; 15(12): e0242918, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33320845

RESUMEN

Various items of roll molds are popularly used to fabricate different kinds of optical films for optoelectronic information and other new and high-tech fields, while the fabrication and evaluation of optical microstructures on a cylindrical roller surface is more difficult than ecumenically manufactured products. In this study, the machinability of microstructures on the roll based on a fast tool servo (FTS) system is investigated. First, the flexible hinge holder for a FTS is designed and its structural parameters are optimized with finite-element analysis and fatigue reliability theory. The tool radius compensation algorithm for complicated microstructures is then deduced based on the surface fitting and bilinear interpolation algorithm of discrete data. Meanwhile, the evaluation index and method are proposed by the medium section method. Finally, a machining test of aspheric arrays on a cylindrical aluminum surface is carried out, and the high quality of the microstructure indicates that the proposed method is able to be used to fabricate optical microstructures.


Asunto(s)
Diseño de Equipo , Algoritmos , Análisis de Elementos Finitos , Propiedades de Superficie
10.
Angle Orthod ; 90(6): 811-822, 2020 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-33378522

RESUMEN

OBJECTIVES: To determine the different impact of moment-to-force ratio (M:F) variation for each tooth and spatial plane and to develop a mathematical model to predict the orthodontic movement for every tooth. MATERIALS AND METHODS: Two full sets of teeth were obtained combining cone-beam computed tomography (CBCT) and optical scans for two patients. Subsequently, a finite element analysis was performed for 510 different force systems for each tooth to evaluate the centers of rotation. RESULTS: The center of CROT locations were analyzed, showing that the M:F effect was related to the spatial plane on which the moment was applied, to the force direction, and to the tooth morphology. The tooth dimensions on each plane were mathematically used to derive their influence on the tooth movement. CONCLUSION: This study established the basis for an orthodontist to determine how the teeth move and their axes of resistance, depending on their morphology alone. The movement is controlled by a parameter (k), which depends on tooth dimensions and force system features. The k for a tooth can be calculated using a CBCT and a specific set of covariates.


Asunto(s)
Técnicas de Movimiento Dental , Diente , Tomografía Computarizada de Haz Cónico , Análisis de Elementos Finitos , Humanos , Fenómenos Mecánicos , Diente/diagnóstico por imagen , Raíz del Diente/diagnóstico por imagen
11.
Nan Fang Yi Ke Da Xue Xue Bao ; 40(12): 1826-1830, 2020 Dec 30.
Artículo en Chino | MEDLINE | ID: mdl-33380395

RESUMEN

OBJECTIVE: To construct a three-dimensional (3D) finite element mechanical model of total hip arthroplasty for comparison of biomechanical differences of the hip joint following capsule repair and postoperative rehabilitation. METHODS: Six frozen specimens of hip joint posterior capsule ligament complex were collected in a bone-capsule-bone manner, and the load-strain curve and other mechanical properties of the specimens were tested using a universal material testing machine. Thin-section CT data of the pelvis and lower limbs obtained from a volunteer were imported into Mimics software to construct a 3D model of the hip joint. Digital models of the cup, femoral prosthesis and joint capsule were created in CATIA software and imported into Mimics to simulate total hip arthroplasty; the assembled data were imported into ABAQUS software. The properties of the capsule were set according to results of the mechanical test, anatomical studies, and constitutive equations, and the biomechanics of the anatomically repaired and conventionally repaired capsules were compared during hip flexion. RESULTS: The results of testing on the 6 capsule specimens showed a mean ultimate tensile strain of (39.21±5.23)% and a mean of ultimate tensile strength of 1.65±0.38 MPa. The stress-strain curve of the finite element model was consistent with the results of mechanical test on the specimens and the biochemical characteristics of the capsule. The stress was distributed evenly in the anatomically repaired capsule during hip flexion but not in the capsule repaired through the conventional approach; the tensile stress in the lower part of the conventionally repaired capsule reached the ultimate tensile stress measured on the capsule specimens at a 90° flexion. CONCLUSIONS: The finite element model allows dynamic, quantitative and visual assessment of stress distribution in the hip joint capsule, and compared with the conventional approach, anatomical repair can achieve better biomechanical properties of the capsule.


Asunto(s)
Artroplastia de Reemplazo de Cadera , Articulación de la Cadera , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Articulación de la Cadera/diagnóstico por imagen , Articulación de la Cadera/cirugía , Humanos , Pronóstico , Estrés Mecánico
12.
Hua Xi Kou Qiang Yi Xue Za Zhi ; 38(6): 642-646, 2020 Dec 01.
Artículo en Chino | MEDLINE | ID: mdl-33377340

RESUMEN

OBJECTIVE: To study the comprehensive impact of scar and maxillary expansion combined with protraction on the development of maxilla with cleft lip and palate after repair operation. METHODS: In the original finite element model of the maxilla with cleft palate, a finite element model of the maxilla with cleft lip and palate was established by using Boolean operation in ANSYS. Scar force after cleft lip and palate repair and maxillary expansion force combined with protraction were added simultaneously to process the stress analysis. RESULTS: Maxillary deformation occurred in the three-dimensional direction. The comparison of displacements was as follows: X-axis>Z-axis>Y-axis. CONCLUSIONS: Maxillary growth is significantly inhibited in the three-dimensional direction under the comprehensive impact of scar and maxillary expansion combined with protraction after repair operation, especially transverse and sagittal growth.


Asunto(s)
Labio Leporino , Fisura del Paladar , Cicatriz/patología , Labio Leporino/cirugía , Fisura del Paladar/patología , Fisura del Paladar/cirugía , Análisis de Elementos Finitos , Humanos , Maxilar/patología , Maxilar/cirugía , Técnica de Expansión Palatina
13.
J Vis Exp ; (166)2020 12 04.
Artículo en Inglés | MEDLINE | ID: mdl-33346198

RESUMEN

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized in vitro stretching methods. Various available systems use 2D substrate-based stretchers, while the accessibility of 3D techniques to strain soft hydrogels, is more restricted. Here, we describe a method that allows external stretching of soft hydrogels from their circumference, using an elastic silicone strip as the sample carrier. The stretching system utilized in this protocol is constructed from 3D-printed parts and low-cost electronics, making it simple and easy to replicate in other labs. The experimental process begins with polymerizing thick (>100 µm) soft fibrin hydrogels (Elastic Modulus of ~100 Pa) in a cut-out at the center of a silicone strip. Silicone-gel constructs are then attached to the printed-stretching device and placed on the confocal microscope stage. Under live microscopy the stretching device is activated, and the gels are imaged at various stretch magnitudes. Image processing is then used to quantify the resulting gel deformations, demonstrating relatively homogenous strains and fiber alignment throughout the gel's 3D thickness (Z-axis). Advantages of this method include the ability to strain extremely soft hydrogels in 3D while executing in situ microscopy, and the freedom to manipulate the geometry and size of the sample according to the user's needs. Additionally, with proper adaptation, this method can be used to stretch other types of hydrogels (e.g., collagen, polyacrylamide or polyethylene glycol) and can allow for analysis of cells and tissue response to external forces under more biomimetic 3D conditions.


Asunto(s)
Hidrogeles/química , Imagenología Tridimensional , Microscopía , Módulo de Elasticidad , Fibrina/química , Fibrinógeno/química , Análisis de Elementos Finitos , Polimerizacion , Siliconas/química , Programas Informáticos , Trombina/química , Interfaz Usuario-Computador
14.
Angle Orthod ; 90(6): 801-810, 2020 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-33378514

RESUMEN

OBJECTIVES: To assess the mechanical environment for three fixed appliances designed to retract the lower anterior segment. MATERIALS AND METHODS: A cone-beam computed tomography scan provided three-dimensional morphology to construct finite element models for three common methods of lower anterior retraction into first premolar extraction spaces: (1) canine retraction with a T-loop, (2) en-masse space closure with the power-arm on the canine bracket (PAB), and (3) power-arm directly attached to the archwire mesial to the canine (PAW). Half of the symmetric mandibular arch was modeled as a linear, isotropic composite material containing five teeth: central incisors (L1), lateral incisor (L2), canine (L3), second premolar (L4), and first molar (L5). Bonded brackets had 0.022-in slots. Archwire and power-arm components were 0.016 × 0.022 in. An initial retraction force of 125 cN was used for all three appliances. Displacements were calculated. Periodontal ligament (PDL) stresses and distributions were calculated for four invariants: maximum principal, minimum principal, von Mises, and dilatational stresses. RESULTS: The PDL stress distributions for the four invariants corresponded to the displacement patterns for each appliance. T-loop tipped the canine(s) and incisors distally. PAB rotated L3 distal in, intruded L2, and extruded L1. PAW distorted the archwire resulting in L3 extrusion as well as lingual tipping of L1 and L2. Maximum stress levels in the PDL were up to 5× greater for the PAW than the T-loop and PAB methods. CONCLUSIONS: T-loop of this type is more predictable because power-arms can have rotational and archwire distortion effects that result in undesirable paths of tooth movement.


Asunto(s)
Incisivo , Técnicas de Movimiento Dental , Diente Premolar , Fenómenos Biomecánicos , Diente Canino/diagnóstico por imagen , Análisis de Elementos Finitos , Alambres para Ortodoncia , Estrés Mecánico
15.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 37(6): 974-982, 2020 Dec 25.
Artículo en Chino | MEDLINE | ID: mdl-33369336

RESUMEN

Numerical simulation of stent deployment is very important to the surgical planning and risk assess of the interventional treatment for the cardio-cerebrovascular diseases. Our group developed a framework to deploy the braided stent and the stent graft virtually by finite element simulation. By using the framework, the whole process of the deployment of the flow diverter to treat a cerebral aneurysm was simulated, and the deformation of the parent artery and the distributions of the stress in the parent artery wall were investigated. The results provided some information to improve the intervention of cerebral aneurysm and optimize the design of the flow diverter. Furthermore, the whole process of the deployment of the stent graft to treat an aortic dissection was simulated, and the distributions of the stress in the aortic wall were investigated when the different oversize ratio of the stent graft was selected. The simulation results proved that the maximum stress located at the position where the bare metal ring touched the artery wall. The results also can be applied to improve the intervention of the aortic dissection and the design of the stent graft.


Asunto(s)
Implantación de Prótesis Vascular , Stents , Arterias , Enfermedades Cardiovasculares , Simulación por Computador , Análisis de Elementos Finitos , Humanos , Diseño de Prótesis
16.
Braz Dent J ; 31(5): 540-547, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33146339

RESUMEN

The aim of this study was to analyze the influence of orthodontic bracket type (metallic or ceramic) and mouthguard on biomechanical response during impact. Two-dimensional plane-strain models of a patient with increased positive overjet of the maxillary central incisor was created based on a CT scan, simulating the periodontal ligament, bone support, gingival tissue, orthodontic brackets (metallic or ceramic) and mouthguard. A nonlinear dynamic impact finite element analysis was performed in which a steel object hit the model at 1 m/s. Stress distributions (Von Mises and Modified Von Mises) and strain were evaluated. Stress distributions were affected by the bracket presence and type. Models with metallic and ceramic bracket had higher stresses over a larger buccal enamel impact area. Models with ceramic brackets generated higher stresses than the metallic brackets. Mouthguards reduced the stress and strain values regardless of bracket type. Mouthguard shock absorption were 88.37% and 89.27% for the metallic and ceramic bracket, respectively. Orthodontic bracket presence and type influenced the stress and strain generated during an impact. Ceramic brackets generated higher stresses than metallic brackets. Mouthguards substantially reduced impact stress and strain peaks, regardless of bracket type.


Asunto(s)
Protectores Bucales , Soportes Ortodóncicos , Cerámica , Análisis del Estrés Dental , Análisis de Elementos Finitos , Humanos , Incisivo , Ensayo de Materiales , Diseño de Aparato Ortodóncico , Estrés Mecánico
17.
Georgian Med News ; (306): 156-161, 2020 Sep.
Artículo en Ruso | MEDLINE | ID: mdl-33130665

RESUMEN

OBJECTIVE: To substantiate the optimal variant of the reinforcement of resin-bonded bridges (RBB) for replacing small included defects of the dentition in the lateral area by studying the stress-strain states (SSS) of their various designs. To study the stress-strain state, the RBB structures were simulated in the ANSYS 12.1 computer environment. In simulation model I, two fiberglass tapes were used to reinforce the RBB, in model II - two fiberglass beams, and in model III - a fiberglass tape and a beam. Maximum displacements, distribution of von Mises equivalent stresses and safety factors in RBB constituent elements were evaluated. The largest values ​​of the maximum displacement were established under the influence of angular load in photocomposite of artificial tooth in all models. Von Mises equivalent stresses formed concentrations in frameworks of models I and II places that could destroy RBB, in model III they were evenly distributed over tape and beam. The safety factor for photocomposite was 1.6 to 3.8, for tapes and beams - from 8.0 to 11.4 and from 38.5 to 87.4, respectively. The stress-strain states of RBB models differ significantly depending on their reinforcement, place and direction of load application. Reinforcement of RBB with tape and beam seems to be the best option, since in such RBB loads are more evenly distributed.


Asunto(s)
Dentadura Parcial Fija con Resina Consolidada , Simulación por Computador , Análisis de Elementos Finitos , Estrés Mecánico
18.
Am J Orthod Dentofacial Orthop ; 158(6): e161-e172, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-33250107

RESUMEN

INTRODUCTION: The aims and objectives of this study were to evaluate the von Mises stress and principal stress distribution and displacement of anterior teeth in a lingual orthodontics system along the periodontal ligament and alveolar bone by various combinations of mini-implants and lever arm during en-masse retraction. Four 3-dimensional finite element (FE) models of the bilateral maxillary first premolar extraction cases were constructed. METHODS: Lingual brackets were (0.018-in slots) positioned over the center of the clinical crown. In all 4 models, 150 g of retraction force was applied with the help of a nickel-titanium closed coil spring with different combinations of mini-implants and lever arm on each side. FE analysis was then performed to evaluate stress distribution, principal stress, von Mises stress, and displacement of the anterior teeth using ANSYS software (version 12.1; Ansys, Canonsburg, Pa). The FE study was enough to validate the analysis results obtained by software tools with FE simulation instead of experimental readings. Thus, statistical analysis was not required. RESULTS: In this study, maximum tensile stresses were observed in the periodontal ligament at the mesial cervical region of the canine with values of 1.84 MPa, 2.02 MPa, 1.88 MPa, and 2.08 MPa for models 1-4, respectively. Maximum von Mises stress in alveolar bone was 8.05 MPa, 8.23 MPa, 8.19 MPa, and 8.37 MPa for models 1-4, respectively, which was within the optimum limit (135 MPa). Variable amounts of displacements like lingual crown tipping, lingual root tipping, and extrusion were observed in all the models. The 15-mm long lever arm models (models 2 and 4) showed a more controlled crown (0.015 mm) and root movement (0.004 mm) compared with 12-mm long lever arm models (models 1 and 3). CONCLUSIONS: In lingual orthodontics, controlled root movement increased as we increased the length of the lever arm. It was also concluded that the amount of increased controlled tipping found with the placement of the mini-implant was toward the palatal slope.


Asunto(s)
Implantes Dentales , Técnicas de Movimiento Dental , Brazo , Análisis del Estrés Dental , Análisis de Elementos Finitos , Incisivo , Estrés Mecánico
19.
Zhongguo Gu Shang ; 33(10): 948-53, 2020 Oct 25.
Artículo en Chino | MEDLINE | ID: mdl-33107259

RESUMEN

OBJECTIVE: To establish a new mechanical model of distal humerus in children with epiphysial cartilage, stimulate supracondylar humerus fracture and perform three dimensional finite elements, and study effect of pins numbers, pin tract, outlet height and pin configurations on stability of fixation. METHODS: Three dimensional computed tomography (CT) data of 6-year-old boy with distal humerus was downloaded from picture archiving and communications systems software (PACS), the data of picture was imported into Simpleware and SolidWorks 2016 software to establish distal humerus fracture in children contained ossific nucleus of the capitellum (ONC) and distal cartilage. Normal extense supracondylar humerus fracture model was established to stimulate configurations of crossed and lateral pinning fixation, 30 N was added on the direction of flexion extension and varus valgus, while 50 N was added on the direction of internal and external turning. Stability was analyzed by displacement degree of distal fracture. RESULTS: Among 2-pin configurations, 2-crossed pins were more stable against rotation forces which could resist rotation stress over 2 585 Nmm/ °, while low position through ONC of 2-divergent lateral pins were more stable, which could resist stress of 45 N /mm and 190 N /mm during the test of resistant strains and varus-valgus stress. The third pins was added into the more stable lateral 2-pins, the stability in all directions were increased obviously, and 3 crossed pins is the most stable, stress of flexion-extension, varus-valgus and internal-external turning were 198 N /mm, 395 N /mm and 6 251 Nmm/ °. CONCLUSION: Two-divergent lateral pins could provide enough stability for supracondylar humerus fracture in children. In two-crossed pins, the upper border of MDJ could provide the best stability. Three-crossed pins could offer the best stability against both translation and rotation forces.


Asunto(s)
Hilos Ortopédicos , Fijación Interna de Fracturas , Fenómenos Biomecánicos , Niño , Análisis de Elementos Finitos , Humanos , Húmero , Masculino
20.
Shanghai Kou Qiang Yi Xue ; 29(4): 355-358, 2020 Aug.
Artículo en Chino | MEDLINE | ID: mdl-33089281

RESUMEN

PURPOSE: To compare the stress distribution of dental implants with different body shapes after maxillary sinus augmentation. MRTHODS: Three different implant models varying in implant shape were investigated in D3-type maxilla. All materials were assumed to be linear elastic, homogenous and isotropic. An oblique force of 150 N was applied to the implant. Maximal equivalent von-Mises of supporting bone around implants were measured. All of the models were measured by Ansys Workbench 14.5. Statistical analysis was performed using SPSS 17.0 software package. RESULTS: Highest stress of supporting bone emerged on the crestal cortical site around the implant neck. There was no significant difference in the maximum EQV of supporting cortical bone between different groups; the maximum EQV of supporting trabecular bone in the tapered implant group was much higher than other groups; application of grafts reduced the maximum EQV of both cortical and trabecular bone in all groups. CONCLUSIONS: Tampered implant can induce elevated stress distribution of the upper trabecular bone, which may promote marginal bone loss. Application of grafts after maxillary sinus augmentation could favors in reducing the stress loading of dental implants.


Asunto(s)
Implantes Dentales , Maxilar , Diseño de Prótesis Dental , Análisis de Elementos Finitos , Maxilar/cirugía , Seno Maxilar/diagnóstico por imagen , Seno Maxilar/cirugía , Estrés Mecánico
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