Finite element analysis of cervical intervertebral discs after removing different ranges of uncinate processes / 解剖学报

Objective To study the stress change characteristics of the cervical disc after removing different ranges of the uncinate process by establishing a three⁃dimensional finite element model of the C

Effect of miniscrew placement height on the distribution of biological forces produced by clear aligner for mandibular molar distalization / 口腔疾病防治

Objective@#To explore the effect of different miniscrew placement heights on the distribution of biological forces produced by clear aligner combined with intramaxillary traction for mandibular molar distalization, to identify the miniscrew location that is conducive to the protection of lower anterior tooth anchorage and to provide a reference that can be used when designing clinical treatments.@*Methods@#Mimics, GeomagicStudio 2017, SolidWorks 2016, and Ansys workbench were used to establish finite element analysis models and perform mechanical analysis under the following six working conditions: working condition 1 was the control group without miniscrews; working conditions 2 to 5 had miniscrew in the buccal bone cortex between the first and second molars of the lower jaw 10 mm, 7 mm, 4 mm, and 1 mm from the top of the alveolar crest, respectively; working condition 6 had the miniscrew in the center of the buccal tongue at the anterior edge of the ascending branch of the lower jaw 5 mm above the occlusal plane.@*Results@#On the sagittal axis, miniscrew anchorage caused distal displacement of all teeth. Compared to the control group, in the miniscrew group, the displacement of the anterior molars exceeded that of the second molars. On the vertical axis, the result in the control group was similar to backward bending; the results in the miniscrew groups resembled the effect of a lever, lowering the lateral incisors and canines and raising the central incisors and first premolars. On the coronal axis, the second premolars and the first molars showed lingual displacement in the control group, and only the premolars and first molars showed lingual displacementin the miniscrew groups. The canines were the teeth that were most strongly affected by the change in miniscrew placement height.@*Conclusion@#The higher the miniscrew position is, the stronger the protective effect on the anterior anchorage. According to the miniscrew placement height, the mandibular arch should be properly narrowed, the central incisors and first premolars should be lowered, and the lateral incisors and canines should be raised when designing clinical treatments.

Research progress of finite element method in the biomechanics of the orbit / 国际眼科杂志(Guoji Yanke Zazhi)

The finite element method(FEM)is a widely employed mathematical technique in mechanical research that divides an object into discrete and interacting finite elements. Medically, finite element analysis(FEA)enables the simulation of biomechanical experiments that are challenging to conduct. Orbital surgery poses significant challenges to ophthalmologists due to its inherent difficulty and steep learning curve. FEM enables the simulation and analysis of the mechanical properties of orbital tissue, offering a novel approach for diagnosing and treating orbital-related diseases. With technological advancements, FEM has significantly matured in the diagnosis and treatment of orbital diseases, becoming a popular area of research in orbital biomechanics. This paper reviewed the latest advancements in orbital FEM, encompassing the development of orbital FEA models, simulation of orbital structure, and its application in orbital-related diseases. Additionally, the limitations of FEM and future research directions are also discussed. As a digital tool for auxiliary diagnosis and treatment, orbital FEA will progressively unlock its potential for diagnosing and treating orbital diseases alongside technological advancements.

Finite element analysis of the stability of Mason type Ⅲ radial head fracture fixed with three cross-bridge headless compression screw and locking plate / 中国骨伤

OBJECTIVE@#To compare the biomechanical stability of three cross-bridge headless compression screws and locking plates in the fixation of Mason type Ⅲ radial head fractures by finite element method.@*METHODS@#Using reverse modeling technology, the radial CT data and internal fixation data of a healthy 25-year-old male were imported into the relevant software. Three-dimensional finite element model of 3 cross-bridge headless compression screws and locking plates for MasonⅢ radial head fractures were established, and the radial head was loaded with 100 N axial loading. The maximum displacement, maximum Von Mises stress and stress distribution of the two groups were compared.@*RESULTS@#The maximum displacements of the three cross-bridge screws group and locking plate group were 0.069 mm and 0.087 mm respectively, and the Von Mises stress peaks were 18.59 MPa and 31.85 MPa respectively. The stress distribution of the three screws group was more uniform.@*CONCLUSION@#Both internal fixation methods can provide good fixation effect. CoMPared with the locking plate fixation method, the 3 cross-bridge headless compression screws fixation is more stable and the stress distribution is more uniform.

Stress distribution in peri-implant bone, implants, and prostheses: 3D-FEA of marginal bone loss and prosthetic design / Distribuição de estresse no osso peri-implantar, implantes e próteses: análise 3D-FEA de perda óssea marginal e design protético

Objective: In response to the demand for dental implants, extensive research has been conducted on methods for transferring load to the surrounding bone. This study aimed to evaluate the stresses on the peripheral bone, implants, and prostheses under scenarios involving of the following variables: prosthesis designs, vertical bone heights, load angles, and restorative materials. Material and Methods: Three implants were inserted in the premolar and molar regions (5-6-7) of the two mandibular models. Model 1 represented 0 mm marginal bone loss and Model 2 simulated 3 mm bone loss. CAD/CAM-supported materials, hybrid ceramic (HC), resin-nano ceramic (RNC), lithium disilicate (LiSi), zirconia (Zr), and two prosthesis designs (splinted and non-splinted) were used for the implant-supported crowns. Forces were applied vertically (90°) to the central fossa and buccal cusps and obliquely (30°) to the buccal cusps only. The stresses were evaluated using a three-dimensional Finite Element Analysis. Results: Oblique loading resulted in the highest stress values. Of the four materials, RNC showed the low stress in the restoration, particularly in the marginal area. The use of different restorative materials did not affect stress distribution in the surrounding bone. The splinted prostheses generated lower stress magnitude on the bone, and while more stress on the implants were observed. Conclusion: In terms of the stress distribution on the peri-implant bone and implants, the use of different restorative materials is not important. Oblique loading resulted in higher stress values, and the splinted prosthesis design resulted in lower stress (AU)

Objetivo: Em resposta à demanda por implantes dentários, extensa pesquisa foi realizada sobre métodos para transferir carga ao osso circundante. Este estudo buscou avaliar os estresses no osso periférico, implantes e próteses em cenários que envolvem as seguintes variáveis: designs de próteses, alturas ósseas verticais, ângulos de carga e materiais restauradores. Material e Métodos: Três implantes foram inseridos nas regiões dos pré-molares e molares (5-6-7) de dois modelos de mandíbula. O Modelo 1 representou perda óssea marginal de 0 mm e o Modelo 2 simulou perda óssea de 3 mm. Materiais suportados por CAD/CAM, cerâmica híbrida (HC), cerâmica nano-resina (RNC), dissilicato de lítio (LiSi), zircônia (Zr) e dois designs de próteses (sintetizadas e não-sintetizadas) foram utilizados para as coroas suportadas por implantes. Forças foram aplicadas verticalmente (90°) à fossa central e cúspides bucais e obliquamente (30°) apenas às cúspides bucais. Os estresses foram avaliados usando Análise de Elementos Finitos tridimensional. Resultados: Cargas oblíquas resultaram nos valores mais altos de estresse. Entre os quatro materiais, RNC mostrou baixo estresse na restauração, especialmente na área marginal. O uso de diferentes materiais restauradores não afetou a distribuição de estresse no osso circundante. Próteses sintetizadas geraram menor magnitude de estresse no osso, enquanto mais estresse nos implantes foi observado. Conclusão: Em termos de distribuição de estresse no osso peri-implantar e implantes, o uso de diferentes materiais restauradores não é crucial. Cargas oblíquas resultaram em valores mais altos de estresse, e o design de prótese sintetizada resultou em menor estresse. (AU)

Biomechanical behavior of three maxillary expanders in cleft lip and palate: a finite element study

Abstract: This study evaluated the stress distribution in the dentoalveolar and palatal bone structures during maxillary expansion in a 17-year-old male patient with bilateral cleft lip and palate (BCLP) using expanders with dental (HYRAX) and skeletal anchorage (MARPE). For the generation of the specific finite element models, cone-beam computed tomography was used, and the DICOM files were exported to Mimics 3-Matic (Materialise) and Patran (MSC Software) software. Three specific three-dimensional models were generated: A) HYRAX: conventional four-banded hyrax screw (9 mm); B) MARPE-DS: 3 miniscrews (1.8 mm diameter - 5.4 mm length) and four-banded dental anchorage; and C) MARPE-NoDS: 3 miniscrews without dental anchorage. Maxillary expansion was simulated by activating the expanders transversely 1 mm on the "X" axis. HYRAX resulted in higher levels of deformation predominantly in the dentoalveolar region. MARPE-DS showed stress in the dentoalveolar region and mainly in the center of the palatal region, at approximately 4,000 με. MARPE-NoDS exhibited evident stress only in the palatal region. High stress levels in the root anchoring teeth were observed for HYRAX and MARPE-DS. In contrast, MARPE-NoDS cause stress on the tooth structure. The stress distribution from the expanders used in the BLCP showed asymmetric expansive behavior. During the initial activation phase of expansion, the HYRAX and MARPE-DS models produced similarly high strain at the dentoalveolar structures and upper posterior teeth displacement. The MARPE-NoDS model showed restricted strain on the palate.

Sobrevivência em fadiga de coroas bioinspiradas bilaminadas: estudo in vitro / Fatigue survival rate of bioinspired bilaminar crowns: in vitro study

O objetivo deste estudo foi avaliar o comportamento biomecânico através da resistência à fadiga e análise por elementos finitos de coroas bioinspiradas bilaminadas com infraestruturas modificadas na superfície vestibular (Estudo A) e utilizando diferentes materiais cerâmicos com módulos elásticos distintos (Estudo B). Para isso, foram confeccionados 90 preparos para coroa total em resina epóxi G10, sobre os quais foram preparadas coroas bioinspiradas de acordo com os seguintes grupos: Estudo A - IC (infraestrutura convencional), IME (infraestrutura modificada estratificada) e IMC (infraestrutura modificada cimentada), todas confeccionadas em dissilicato de lítio (infraestrutura) + porcelana (recobrimento); Estudo B ­ DL+LEU (dissilicato de lítio + leucita), LEU+DL (leucita + dissilicato de lítio), CH+DL (cerâmica híbrida + dissilicato de lítio) e CH+LEU (cerâmica híbrida + leucita). Para o Estudo A, todas as infraestruturas foram usinadas; os recobrimentos dos grupos IC e IME foram confeccionados através da estratificação, e os recobrimentos do grupo IMC foram usinados. Já para o Estudo B, todas as peças foram usinadas, de acordo com o material cerâmico de cada grupo. Em seguida, foi realizada a cimentação adesiva dos recobrimentos sobre as infraestruturas (a depender do grupo) e das coroas sobre os preparos utilizando cimento resinoso fotopolimerizável (Variolink Esthetic LC). Após a cimentação, os espécimes foram submetidos ao teste de fadiga cíclica (10.000 ciclos, 20Hz), e como desfecho foram considerados dois eventos, em que o primeiro foi a ocorrência de trinca e/ou lascamento (evento 1) e o segundo foi a falha catastrófica do conjunto (evento 2). Os valores de carga e número de ciclos para falha em que foram observados os eventos 1 e 2 foram utilizados para realizar a análise de sobrevivência de acordo com Kaplan-Meier e Log-Rank (Mantel-Cox; 95%). As marcas de fratura e o modo de falha das coroas foram avaliados e classificados por estereomicroscópio óptico e microscópio eletrônico de varredura. Por fim, foi realizada análise por elementos finitos (FEA) para ambos os estudos, a fim de avaliar a distribuição de tensões sobre as coroas e interface adesiva. Para o Estudo A, os resultados do teste de fadiga mostraram que, considerando o evento 1 (trinca/lascamento), os grupos IC e IMC apresentaram médias de carga fadiga estatisticamente significantes entre si (733,33 N e 913,33 N, respectivamente), enquanto o grupo IME apresentou média superior (1.020 N). O mesmo foi observado para o número de ciclos em fadiga para todos os grupos. Ao considerar o evento 2 (falha catastrófica), os três grupos apresentaram médias estatisticamente semelhantes entre si (~1.028 N). Os resultados de FEA mostraram que o grupo IC concentrou maior tensão de tração do que os grupos IME e IMC. Para o Estudo B, no teste de fadiga, o grupo DL+LEU apresentou a maior média de resistência à fadiga (evento 1: 913,33 N e evento 2: 1033,33 N), enquanto todas as outras combinações de materiais cerâmicos analisadas foram estatisticamente semelhantes entre si, considerando carga e número de ciclos. Com relação ao FEA, os grupos com cerâmica híbrida (CH+DL e CH+LEU) apresentaram menores picos de concentração de tensão na infraestrutura do que os grupos com cerâmicas vítreas (DL+LEU e LEU+DL), porém, em contrapartida, concentraram maior tensão na interface adesiva. Com isso, conclui-se que a utilização da infraestrutura modificada é uma alternativa viável e promissora para tratamentos reabilitadores, apresentando sobrevivência em fadiga e distribuição de tensões satisfatórias. Além disso, a combinação entre uma infraestrutura de dissilicato de lítio e recobrimento de cerâmica a base de leucita corresponde a melhor abordagem considerando a infraestrutura modificada.(AU)

The objective of this study was to evaluate the biomechanical behavior through fatigue resistance and finite element analysis of bilaminar bioinspired crowns with modified infrastructures on the buccal surface (Study A) and using different ceramic materials with different elastic moduli (Study B). For this, 90 preparations were made for a full crown in G10 epoxy resin, on which bioinspired crowns were prepared according to the following groups: Study A - CI (conventional infrastructure), SMI (stratified modified infrastructure) and CMI (cemented modified infrastructure ), all made of lithium disilicate (infrastructure) + porcelain (veneer); Study B ­ LD+LEU (lithium disilicate + leucite), LEU+LD (leucite + lithium disilicate), HC+LD (hybrid ceramic + lithium disilicate) and HC+LEU (hybrid ceramic + leucite). For Study A, all infrastructures were machined; the coverings of the CI and SMI groups were made through stratification technique, and the veneers of the SMI group were machined. For Study B, all pieces were machined, according to the ceramic material of each group. Then, the veneers were cemented into their infrastructures (depending on the group) and crowns were cemented into preparations using light-cured resin cement (Variolink Esthetic LC). After cementing, the specimens were subjected to the cyclic fatigue test (10,000 cycles, 20Hz), and as an outcome two events were considered: the occurrence of cracking and/or chipping (event 1) and catastrophic failure (event 2). The load (N) and number of cycles to failure in which events 1 and 2 were observed were used to perform the survival analysis according to Kaplan-Meier and Log-Rank (Mantel- Cox; 95%). The fracture marks and failure mode of the crowns were evaluated and classified by optical stereomicroscope and scanning electron microscope. Finally, finite element analysis (FEA) was performed for both studies in order to evaluate the stress distribution over the crowns and adhesive interface. For Study A, the results of the fatigue test showed that, considering event 1 (cracking/chipping), the CI and CMI groups presented average to failure that were statistically significant compared to each other (733.33 N and 913.33 N, respectively), while the SMI group showed higher averages (1,020 N). Same pattern was observed for the number of cycles under fatigue for both groups. When considering event 2 (catastrophic failure), the three groups presented statistically similar means (~1,028 N). The FEA results showed that the CI group concentrated greater tensile stress than the CMI and SMI groups. For Study B, in the fatigue test, the LC+LEU group presented the highest average fatigue resistance (event 1: 913.33 N and event 2: 1033.33 N), while all other combinations of ceramic materials analyzed were statistically similar to each other, considering load and number of cycles. Regarding FEA, the groups with hybrid ceramics (HC+LC and HC+LEU) showed lower stress concentration peaks in the infrastructure than the groups with glass ceramics (LC+LEU and LEU+LC), however, on the other hand, concentrated greater tension at the adhesive interface. With this, it is concluded that the use of modified infrastructure is a viable and promising alternative for oral rehabilitation treatments, presenting satisfactory fatigue survival and adequate stress distribution. Furthermore, the combination of a lithium disilicate infrastructure and a leucite-based ceramic coating corresponds to the best approach considering the modified infrastructure.(AU)

Biomechanical impact of labiolingual diameter on endodontically treated anterior teeth with crown restoration under occlusal loading

Abstract Objective To evaluate the effect of the labiolingual diameter and construction of an endodontically treated (ET) anterior tooth with crown restoration on stress distribution and biomechanical safety under occlusal loading. Methodology Three-dimensional finite element models were generated for maxillary central incisors with all-ceramic crown restorations. The labiolingual diameters of the tooth, defined as the horizontal distance between the protrusion of the labial and lingual surfaces, were changed as follows: (D1) 6.85 mm, (D2) 6.35 mm, and (D3) 5.85 mm. The model was constructed as follows: (S0) vital pulp tooth; (S1) ET tooth; (S2) ET tooth with a 2 mm ferrule, restored with a fiber post and composite resin core; (S3) ET tooth without a ferrule, restored with a fiber post and composite resin core. A total of 12 models were developed. In total, two force loads (100 N) were applied to the crown's incisal edge and palatal surface at a 45° oblique angle to the longitudinal axis of the teeth. The Von Mises stress distribution and maximum stress of the models were analyzed. Results Regardless of the loading location, stress concentration and maximum stress (34.07~66.78MPa) in all models occurred in the labial cervical 1/3 of each root. Both labiolingual diameter and construction influenced the maximum stress of the residual tooth tissue, with the impact of the labiolingual diameter being greater. A reduction in labiolingual diameter led to increased maximum stress throughout the tooth. The ferrule reduced the maximum stress of the core of S2 models (7.15~10.69 MPa), which is lower compared with that of S3 models (19.45~43.67 MPa). Conclusion The labiolingual diameter exerts a greater impact on the biomechanical characteristics of ET anterior teeth with crown restoration, surpassing the influence of the construction. The ferrule can reduce the maximum stress of the core and maintain the uniformity of stress distribution.

Effect of different palatal expanders with miniscrews in surgically assisted rapid palatal expansion: A non-linear finite element analysis

ABSTRACT Introduction: Surgically assisted rapid palatal expansion (SARPE) has been the treatment of choice in subjects presenting skeletally mature sutures. Objective: The purpose of this study was to analyze stress distribution and displacement of the craniofacial and dentoalveolar structures resulting from three types of palatal expanders with surgical assistance using a non-linear finite element analysis. Material and Methods: Three different palatal expanders were designed: Model-I (tooth-bone-borne type containing four miniscrews), Model-II (tooth-bone-borne type containing two miniscrews), and Model-III (bone-borne type containing four miniscrews). A Le Fort I osteotomy was performed, and a total of 5.0 mm palatal expansion was simulated. Nonlinear analysis (three theory) method (geometric nonlinear theory, nonlinear contact theory, and nonlinear material methods) was used to evaluate stress and displacement of several craniofacial and dentoalveolar structures. Results: Regardless of the maxillary expander device type, surgically assisted rapid palatal expansion produces greater anterior maxillary expansion than posterior (ANS ranged from 2.675 mm to 3.444 mm, and PNS ranged from 0.522 mm to 1.721 mm); Model-I showed more parallel midpalatal suture opening pattern - PNS/ANS equal to 54%. In regards to ANS, Model-II (1.159 mm) and Model-III (1.000 mm) presented larger downward displacement than Model-I (0.343 mm). PNS displaced anteriorly more than ANS for all devices; Model-III presented the largest amount of forward displacement for PNS (1.147 mm) and ANS (1.064 mm). All three type of expanders showed similar dental displacement, and minimal craniofacial sutures separation. As expected, different maxillary expander designs produce different primary areas and levels of stresses (the bone-borne expander presented minimal stress at the teeth and the tooth-bone-borne expander with two miniscrews presented the highest). Conclusions: Based on this finite element method/finite element analysis, the results showed that different maxillary expander designs produce different primary areas and levels of stresses, minimal displacement of the craniofacial sutures, and different skeletal V-shape expansion.

RESUMO Introdução: A expansão rápida da maxila assistida cirurgicamente (ERMAC) tem sido o tratamento de escolha em indivíduos que apresentam suturas esqueleticamente maduras. Objetivo: O objetivo deste estudo foi avaliar, utilizando uma análise não linear com elementos finitos, a distribuição de tensões e os deslocamentos das estruturas craniofaciais e dentoalveolares gerados por três tipos de expansores palatinos usados na ERMAC. Material e Métodos: Três tipos de expansores palatinos foram projetados: Modelo I (dento-osseossuportado com quatro mini-implantes), Modelo II (dento-osseossuportado com dois mini-implantes) e Modelo III (osseossuportado com quatro mini-implantes). Uma osteotomia Le Fort I foi realizada e foi simulada uma expansão palatina total de 5,0 mm. Um método de análise não linear (três teorias - teoria da não-linearidade geométrica, teoria do contato não linear e métodos para materiais não lineares) foi utilizado para avaliar a tensão e o deslocamento de diversas estruturas craniofaciais e dentoalveolares. Resultados: Independentemente do tipo de aparelho expansor palatino, a ERMAC produziu maior expansão anterior da maxila do que posterior (ENA variou de 2,675 mm a 3,444 mm e ENP variou de 0,522 mm a 1,721 mm); o Modelo I apresentou padrão de abertura mais paralela da sutura palatina mediana, com ENP/ENA igual a 54%. Com relação à ENA, o Modelo II (1,159 mm) e o Modelo III (1,000 mm) apresentaram maior deslocamento para baixo do que o Modelo I (0,343 mm). A ENP deslocou-se mais para anterior do que a ENA com todos os aparelhos; o Modelo III apresentou o maior deslocamento para anterior da ENP (1,147 mm) e da ENA (1,064 mm). Os três tipos de expansores apresentaram deslocamento dentário semelhante e separação mínima das suturas craniofaciais. Como esperado, diferentes designs de expansores palatinos produzem diferentes áreas primárias e níveis de tensões (o expansor osseossuportado apresentou tensão mínima nos dentes, e o expansor dento-osseossuportado com dois mini-implantes apresentou o maior). Conclusões: Com base nesse estudo de elementos finitos, os resultados mostraram que diferentes designs de expansores palatinos produzem diferentes áreas primárias e níveis de tensão, com deslocamento mínimo das suturas craniofaciais e diferentes expansões esqueléticas em forma de V.

Avaliação da fixação dos avanços maxilares pela técnica de osteotomia Le Fort I / Evaluación de la fijación de avances maxilar mediante la técnica de osteotomía Le Fort I / Evaluation of the fixation of maxillary advancements by the Le Fort I osteotomy technique

Introdução: A osteotomia Le Fort I possibilita a correção de deformidades dentofaciais que envolvem o terço médio da face. Para sua fixação, convencionou-se o emprego de quatro mini-placas nos pilares zigomático-maxilar e nasomaxilar. Propôs-se então, a dispensa da fixação do segmento posterior, surgindo questionamentos relacionados à capacidade biomecânica do sistema. Objetivos: Comparar o estresse biomecânico gerado em três meios distintos de fixação da osteotomia Le Fort I frente ao movimento de avanço sagital linear maxilar de 7mm. Metodologia: Trata-se de uma pesquisa experimental laboratorial, utilizando-se da análise de elementos finitos como ferramenta analítica, a fim de constatar qual das técnicas sofrerá maior estresse biomecânico. Resultados: Constatou-se que o estresse biomecânico gerado é maior quando aplicado em 4 pontos do que quando aplicado em apenas 2 pontos. Conclusão: Os resultados obtidos fornecem informações aos cirurgiões sobre a real necessidade do uso de fixação adicional de acordo com o método de fixação planejado. No entanto, deve ser interpretado de forma cautelosa, considerando-se as limitações deste estudo. Sendo assim, uma análise incipiente, que tem como intuito o fornecimento de evidência científica de grande significância.

Introducción: La osteotomía Le Fort I permite la corrección de deformidades dentofaciales que involucran el tercio medio de la cara. Para su fijación se acordó utilizar cuatro miniplacas en los pilares cigomaticomaxilar y nasomaxilar. Entonces se propuso prescindir de la fijación del segmento posterior, planteando interrogantes relacionados con la capacidad biomecánica del sistema. Objetivos: Comparar el estrés biomecánico generado en tres medios diferentes de fijación de la osteotomía Le Fort I frente a un movimiento de avance sagital lineal maxilar de 7mm. Metodología: Se trata de una investigación experimental de laboratorio, utilizando como herramienta analítica el análisis de elementos finitos, con el fin de comprobar cuál de las técnicas sufrirá un mayor estrés biomecánico. Resultados: Se encontró que el estrés biomecánico generado es mayor cuando se aplica en 4 puntos que cuando se aplica solo en 2 puntos. Conclusión: Los resultados obtenidos brindan información a los cirujanos sobre la necesidad real de utilizar fijación adicional de acuerdo al método de fijación planificado. Sin embargo, debe interpretarse con cautela, considerando las limitaciones de este estudio. Por tanto, un análisis incipiente, que pretende aportar evidencias científicas de gran trascendencia.

Introduction: The Le Fort I osteotomy allows the correction of dentofacial deformities involving the middle third of the face. For its fixation, it was agreed to use four mini plates on the zygomaticomaxillary and nasomaxillary pillars. It was then proposed to dispense with the fixation of the posterior segment, raising questions related to the biomechanical capacity of the system. Objectives: To compare the biomechanical stress generated in three different means of fixation of the Le Fort I osteotomy against a 7mm maxillary linear sagittal advancement movement. Methodology: This is an experimental laboratory research, using finite element analysis as an analytical tool, in order to verify which of the techniques will suffer greater biomechanical stress. Results: It was found that the biomechanical stress generated is greater when applied to 4 points than when applied to only 2 points. Conclusion: The results obtained provide information to surgeons about the real need to use additional fixation according to the planned fixation method. However, it should be interpreted with caution, considering the limitations of this study. Therefore, an incipient analysis, which aims to provide scientific evidence of great significance.

Comportamiento Mecánico de un Premolar Humano Sano Sometido a Fuerzas Funcionales y Disfuncionales en un MEF / Mechanical Behavior of a Healthy Human Premolar Subjected to Functional and Dysfunctional Forces in a FEM

El propósito de este estudio fue analizar el comportamiento mecánico de la estructura dental sana de un primer premolar inferior humano sometido a fuerzas funcionales y disfuncionales en diferentes direcciones. Se buscó comprender, bajo las variables contempladas, las zonas de concentración de esfuerzos que conllevan al daño estructural de sus constituyentes y tejidos adyacentes. Se realizó el modelo 3D de la reconstrucción de un archivo TAC de un primer premolar inferior, que incluyó esmalte, dentina, ligamento periodontal y hueso alveolar considerando tres variables: dirección, magnitud y área de la fuerza aplicada. La dirección fue dirigida en tres vectores (vertical, tangencial y horizontal) bajo cuatro magnitudes, una funcional de 35 N y tres disfuncionales de 170, 310 y 445 N, aplicadas sobre un área de la cara oclusal y/o vestibular del premolar que involucró tres contactos estabilizadores (A, B y C) y dos paradores de cierre. Los resultados obtenidos explican el fenómeno de combinar tres vectores, cuatro magnitudes y un área de aplicación de la fuerza, donde los valores de esfuerzo efectivo equivalente Von Mises muestran valores máximos a partir de los 60 MPa. Los valores de tensión máximos se localizan, bajo la carga horizontal a 170 N y en el proceso masticatorio en la zona cervical, cuando la fuerza pasa del 60 %. Sobre la base de los hallazgos de este estudio, se puede concluir que la reacción de los tejidos a fuerzas funcionales y disfuncionales varía de acuerdo con la magnitud, dirección y área de aplicación de la fuerza. Los valores de tensión resultan ser más altos bajo la aplicación de fuerzas disfuncionales tanto en magnitud como en dirección, produciendo esfuerzos tensiles significativos para la estructura dental y periodontal cervical, mientras que, bajo las cargas funcionales aplicadas en cualquier dirección, no se generan esfuerzos lesivos. Esto supone el reconocimiento del poder de detrimento estructural del diente y periodonto frente al bruxismo céntrico y excéntrico.

SUMMARY: The purpose of this study was to analyze the mechanical behavior of the healthy dental structure of a human mandibular first premolar subjected to functional and dysfunctional forces in different directions. It was sought to understand, under the contemplated variables, the areas of stress concentration that lead to structural damage of its constituents and adjacent tissues. The 3D model of the reconstruction of a CT file of a lower first premolar was made, which included enamel, dentin, periodontal ligament and alveolar bone considering three variables: direction, magnitude and area of the applied force. The direction was directed in three vectors (vertical, tangential and horizontal) under four magnitudes, one functional of 35 N and three dysfunctional of 170, 310 and 445 N, applied to an area of the occlusal and/or buccal face of the premolar that involved three stabilizing contacts (A, B and C) and two closing stops. The results obtained explain the phenomenon of combining three vectors, four magnitudes and an area of force application, where the values of effective equivalent Von Mises stress show maximum values from 60 MPa. The maximum tension values are located under the horizontal load at 170 N and in the masticatory process in the cervical area, when the force exceeds 60%. Based on the findings of this study, it can be concluded that the reaction of tissues to functional and dysfunctional forces varies according to the magnitude, direction, and area of application of the force. The stress values turn out to be higher under the application of dysfunctional forces both in magnitude and in direction, producing significant tensile stresses for the dental and cervical periodontal structure, while under functional loads applied in any direction, no damaging stresses are generated. This supposes the recognition of the power of structural detriment of the tooth and periodontium against centric and eccentric bruxism.

Rendimiento Biomecánico de las Placas de Tibia Proximal Utilizadas en Fracturas de Platillos Tibiales evaluado a través de Modelos de Elementos Finitos: Protocolo de Revisión Sistemática / A systematic Review Protocol Examining the Biomechanical Performance of Proximal Tibial Plates used in Tibial Plate Fractures assessed by Finite Element Analysis

Objetivo. Analizar el rendimiento biomecánico de las placas de tibia proximal utilizadas en fracturas de platillos tibiales evaluado a través de modelos de elementos finitos. Métodos. Se realizará una búsqueda exhaustiva en PubMed/Medline, Embase, Lilacs, Web of Science y Google Scholar. No se utilizará ninguna restricción de idioma o estado de publicación. Dos revisores examinarán de forma independiente los posibles artículos elegibles, de acuerdo con los criterios de selección predefinidos. Se incluirán los estudios que evalúen el rendimiento de los platillos tibiales proximales utilizados en las fracturas del platillo tibial evaluadas mediante el análisis de elementos finitos. La extracción de datos sobre las características del estudio, los métodos, los resultados y la evaluación del riesgo de sesgo se realizará mediante un formulario estandarizado. Considerando el diseño de estudio no se requiere evaluación por comité de ética. Los resultados de esta revisión se difundirán a través de la publicación en revistas revisadas por pares, redes sociales y congresos de la especialidad. Se espera que los resultados de esta revisión permitan optimizar los resultados del manejo quirúrgico de las fracturas de platillos tibiales. Número de registro PROSPERO: CRD42023396015.

Objetive. To analyze the biomechanical performance of proximal tibial plates used in tibial plate fractures evaluated through finite element modeling. Methods. A comprehensive search will be conducted in PubMed/Medline, Embase, Lilacs, Web of Science, and Google Scholar. No language or publication status restrictions will be used. Two reviewers will independently review potential eligible articles according to predefined selection criteria. Studies evaluating the performance of proximal tibial splints used in tibial splint fractures assessed by finite element analysis will be included. Data extraction on study characteristics, methods, results, and risk of bias assessment will be performed using a standardized form. Considering the study design, evaluation by an ethics committee is not required. The results of this review will be disseminated through publication in peer-reviewed journals, social networks and specialty congresses. It is expected that the results of this review will allow optimizing the results of the surgical management of tibial plate fractures. PROSPERO registration number: CRD42023396015.

Biomechanical Behavior Evaluation of a Mandibular Full-Arch Implant-Supported Prosthesis on ZrO2 and TiO2 Monotype Dental Implants / Evaluación del Comportamiento Biomecánico de una Prótesis Implante Soportada de Arcada Completa Mandibular sobre Implantes Dentales Monotipos de ZrO 2 y TiO

This in silico study aimed to evaluate the biomechanical behavior of a full-arch implant-supported prosthesis on titanium and zirconia monotype implants. A 3D mandible containing 1.0 mm thick cortical and cancellous bone was modeled. Four dental implants (3.3 x 10 mm) were inserted into the jaw model in each model. The implants consisted of Titanium (Ti-S group) and Zirconia Monotype/one-piece (Zr-S group). Fixed full-arch implant-supported prostheses were cemented onto the implant. The models were exported to the analysis software and divided into meshes composed of nodes and tetrahedral elements. All materials were considered isotropic, elastic, and homogeneous. Therefore, all contacts were considered bonded, the mandible model was fixed in all directions, applying a static structural axial load of 300 N on the bottom of the fossa of the left mola r teeth. Microstrain and von-Mises stress (MPa) were adopted as failure criteria. Comparable stress and strain values were shown in the peri-implant bone for both groups. However, the Ti-S group presented a lower stress value (1,155.8 MPa) than the Zr-S group (1,334.2 MPa). Regarding bone tissues, the Ti-S group presented 612 µε and the Zr-S group presented 254 µε. The highest strain peak was observed in bone tissues around the implant closer to the load for both groups. Evaluating monotype zirconia and titanium implants, it is suggested that the greater the rigidity of the implant, the greater the concentration of internal stre sses and the less dissipation to the surrounding tissues. Therefore, monotype ceramic implants composed of yttrium-stabilized tetragonal polycrystalline zirconia may be a viable alternative to titanium implants for full-arch prostheses.

El objetivo de este estudio in silico fue evaluar el comportamiento biomecánico de una prótesis implanto soportada de arcada completa sobre implantes monotipo de titanio y zirconia. Se modeló una mandíbula en 3D que contenía tejido óseo cortical y esponjoso de 1,0 mm de espesor. En cada modelo, se insertaron cuatro implantes dentales (3,3 x 10 mm) en el modelo de mandíbula. Los implantes consistieron en Monotipo de Titanio y Zirconia. Sobre el implante se cementaron prótesis implanto soportadas de arcada completa fija. Los modelos se exportaron al software de análisis y se dividieron en mallas compuestas por nodos y elementos tetraédricos. Todos los materiales se consideraron isotrópicos, elásticos y homogéneos. Por lo tanto, todos los contactos se consideraron cementados, el modelo mandibular se fijó en todas las direcciones, aplicando una carga vertical estructural estática de 300 N en el fondo de la fosa de los dientes molares izquierdos. Se seleccionaron la microesfuerzo y la tensión de Von-Mises (MPa) como criterios de falla. Se mostraron valores de tensión y deformación comparables en el hueso periimplantario para ambos grupos. Sin embargo, el grupo Ti-S presentó un valor de estrés menor (1.155,8 MPa) que el grupo Zr-S (1.334,2 MPa). En cuanto a los tejidos óseos, el grupo Ti-S presentó 612 µε y el grupo Zr-S presentó 254 µε. La mayor concentración de deformación en el tejido óseo se observó en los tejidos alrededor del implante más cerca de la carga para ambos grupos. Al evaluar los implantes monotípicos de zirconia y titanio, se sugiere que cuanto mayor sea la rigidez del implante, mayor será la concentración de tensiones internas y menor la disipación a los tejidos circundantes. Por lo tanto, los implantes cerámicos monotipo compuestos de zirconia policristalina tetragonal estabilizada con itrio pueden ser una alternativa viable a los implantes de titanio para prótesis de arcada completa.

Effect of Pin Holes Location of Unicompartmental Knee Arthroplasty on Postoperative Tibial Plateau Mechanical Properties / 中国医疗器械杂志

OBJECTIVE@#The purpose of this study is to explore the biomechanical characteristics of the tibia after unicompartmental knee arthroplasty with different distributions of two-pin holes, and to optimize the two-pin holes scheme to reduce the risk of tibial fractures after unicompartmental knee arthroplasty.@*METHODS@#Lower limbs model is segmented and reconstructed from computed tomography images. Four combinations of two pin holes created for tibial cutting guide placement are simulated with finite element analysis.@*RESULTS@#In the third mode, the positioning hole at the proximal medial edge of the tibial plateau has the highest stress value, and the position of the positioning hole near the medial edge of the proximal tibial plateau appears stress concentration.@*CONCLUSIONS@#The present study revealed that placing tibial cutting guide holding pins centrally would lower the risks of periprosthetic fracture of the medial tibial plateau.

3D finite element analysis of the influence of upper lip pressure on the maxilla for patients with unilateral alveolar cleft / 口腔疾病防治

Objective @#To investigate the biomechanical effects of upper lip pressure on the maxilla in patients with a unilateral alveolar cleft and provide evidence for clinical diagnosis and treatment. @*Methods @#A 3D finite element maxillary model was generated based on cone beam CT (CBCT) data from an 11-year-old female patient with a unilateral alveolar cleft. Two different kinds of upper lip pressure, postsurgery pressure and normal pressure, were applied to the model. The displacement and stress of each reference node were compared and analyzed. @*Results @# By loading upper lip pressure, the maxillary alveolar crest rotated toward the defect and was displaced downward and backward. The displacement of the noncleft side was greater than that of the cleft side and it decreased gradually from the anterior to the posterior. The stress was concentrated on the anterior portion of the alveolar crest. The stress on the noncleft side was greater than that on the cleft side and it decreased gradually from the anterior to the posterior. The maximum stress was concentrated on the palate around the defect. The displacement and stress in the postsurgery group were greater than those of the normal group (P<0.05). @*Conclusion @#By loading upper lip pressure, the maxilla demonstrated asymmetry three-dimensionally. The adverse effects on the maxilla could be mitigated by reducing the upper lip pressure.

Numerical Study on the Process of Human Brain Cooling Treated by Hemoperfusion Mild Hypothermia / 中国医疗器械杂志

Mild hypothermia, as a common means of intraoperative nerve protection, has been used in clinical practice. Compared with the traditional methods such as freezing helmet and nasopharyngeal cooling, hypothermic blood perfusion is considered to be a promising treatment for mild hypothermia, but it lacks experimental and theoretical verification of its cooling effect. In this study, the commercial finite element simulation software COMSOL combined the Pennes equation with the cerebrovascular network model to construct a new simplified human brain model, which was further used to simulate the cooling process of cerebral hypothermic blood perfusion. When the hypothermic blood perfusion was 33 ℃, the human brain could enter the mild hypothermic state within 4 minutes. By comparing with helmet cooling, the feasibility and efficiency of the blood perfusion scheme were verified. By comparing with the calculation results based on Pennes equation, the rationality of the model constructed in this study were verified. This model can non-intrusively predict the changes of brain temperature during surgery, and provide a reference for the setting of treatment parameters such as blood temperature, so as to provide personalized realization of safer and more effective mild hypothermia neuro protection.

A Review on Finite Element Modelling and Simulation for Upper Limb of Human Bone and Implant

@#Medical implants are normally used in clinical practice to treat most orthopaedics situations involving bone fractures, deformities, dislocation, and lengthening. It should be noted that specific measures regarding biomechanical and biomaterial characteristics are required for a successful post-surgery procedure. Biomechanical evaluations on the medical implants could be performed by utilising computer and engineering technology. One of them is in silico studies using finite element method that could be simulated in high-performance computer. However, various assumptions are required in computer simulation, such as the constraints on data input and computer resources. This review paper discusses current approaches of constructing a finite element model of human bone with specific material properties for upper limb such as the shoulder joint, humerus, elbow joint, radius and wrist joint. Previous related literatures were reviewed from selected keywords and search engines. To narrow the literature search in this study, inclusion and exclusion criteria of the literature searching were applied. We looked at the current level of knowledge in this field and offered recommendations for future study. In conclusion, studies from previous literature have demonstrated several ways for developing mathematical models and simulating medical implants.

Biomechanical comparison of spatial weaving and conventional calcaneal plate fixation for calcaneal fracture / 中华骨科杂志

Objective:To compare the biomechanical characteristics of screw only spatial weaving fixation and calcaneal plate fixation in calcaneal fractures.Methods:Sanders type III calcaneus fracture model was established by using calcaneus model specimens: the physiological model group were the normal calcaneal models; the steel plate group were conventional steel plate fixation fracture models; the metal screw group were fracture models with only metal screw weaving fixation; seven and nine absorbable screw spatial weaving groups (seven absorbable screw group, nine absorbable screw group) were used to weave and fix fracture models with seven and nine absorbable screws. Cyclic test and mechanical compression test were carried out, and load-displacement curves were recorded. The material properties of metal screw spatial weaving and calcaneal anatomical plate system were replicated, finite element fracture models were established, and the calcaneal internal fixation models of plate screw group and spatial weaving screw group were completed by reverse processing. The changes of biomechanical characteristics of calcaneal bone in human (70 kg) standing on one foot were simulated, and the distribution of structural strength was analyzed by Von Mises equivalent stress cloud diagram and displacement cloud diagram.Results:In the cyclic test of 20-200 N load, the physiological model group, the plate group, the metal screw group, the absorbable 7 screw group, the absorbable 9 screw group were 0.87±0.22, 0.82±0.08, 0.70±0.12, 1.04±0.13 and 0.83±1.76 mm, the difference in model gap was statistically significant ( F=3.16, P=0.037). Among them, the absorbable 7 screws group was larger than the metal screws group ( t=4.28, P=0.003), and the other pin-two comparisons were not statistically significant ( P>0.05). The deformation of the five groups was 0.37±0.06, 0.38±0.07, 0.38±0.06, 0.52±0.07 and 0.42±0.07 mm, and the difference was statistically significant ( F=4.39, P=0.010). The deformation of absorbable 7 screws group was greater than that of physiological model group, the plate group and metal screw group ( t=3.69, P=0.006; t=3.25, P=0.012; t=3.51, P=0.008). In static test, compression displacement was 7.14±0.79, 7.30±0.66, 6.95±0.28, 8.19±0.61 and 7.16±0.55 mm, the difference was statistically significant ( F=3.28, P=0.032). The displacement of the absorbable 7 screws group was greater than that of the metal screws group ( t=4.13, P=0.003). The stiffness changes were 570.60±122.62, 512.86±80.77, 497.40±66.50, 456.21±58.19 and 560.39±94.40 N/mm, respectively, with no statistical significance ( F=1.44, P=0.258). The results of finite element analysis showed that under 3 500 N axial pressure load, the maximum compression displacement and stiffness of the plate and screw set were 6.47 mm, 540.96 N/mm, and the Von Mises equivalent stress peaks were 450.31 and 353.15 MPa, respectively. The maximum compression displacement and stiffness of the braided screw group were 5.25 mm, 666.67 N/mm, and the peak Von Mises equivalent stress of the screw was 396.20 MPa. Conclusion:Compared with lateral plate fixation, spatial weaving fixation can provide sufficient biomechanical stability for calcaneal healing and is superior to plate fixation in terms of structural stability, which may help to improve the effectiveness of calcaneal fracture fixation.

Three fixation methods in the revision of medial defective intertrochanteric fractures with failed treatment: a finite element analysis / 中华骨科杂志

Objective:To compare the biomechanical differences of dynamic condylar screw (DCS), locking compression plate (LCP) combined with DCS and medial anatomic buttress plate (MABP) combined with DCS in the revision of medial defective intertrochanteric fractures by finite element analysis.Methods:The femoral CT imaging data provided by a healthy adult volunteer were used to reconstruct the solid three-dimensional model of femur by Mimics 21.0 and Geomagics Studio 12. Evans-Jensen II B intertrochanteric fracture was established by Ansys Workbench18.0. The three-dimensional models of proximal femoral nail antirotation (PFNA), DCS, LCP and MABP were reconstructed in Solidworks 2015. The PFNA was assembled with the fracture model, and then the PFNA was removed to establish the postoperative failure model of femoral intertrochanteric fracture and then simulated the fixation in the hip-preserving revision surgery of femoral intertrochanteric fractures: non-medial support reconstruction group (DCS); indirect medial support reconstruction group (DCS+LCP) and partial direct medial support reconstruction group (DCS+MABP). Finally, the forces on the hip joint of 70 kg normal people during standing (700 N), slow walking (1,400 N), brisk walking (1,750 N) and going up and down stairs (2,100 N) were simulated in Abaqus 6.14, the relative displacement and stress peak value of fracture end and stress distribution and stress peak value of internal fixation in different models were recorded.Results:At 700 N axial load, the relative displacement of fracture end fixed by DCS, DCS+LCP and DCS+MABP was 0.28, 0.13 and 0.09 mm; the peak stress of the fracture end was 49.01, 15.29 and 1.35 MPa; the peak stress of internal fixation was 230, 220 and 174 MPa, respectively. At 1,400 N axial load, the relative displacement of the fracture end of the three internal fixation methods was 0.56, 0.24 and 0.16 mm; the peak stress of fracture end was 108.49, 28.96 and 3.12 MPa; the peak stress of internal fixation was 469, 352 and 324 MPa, respectively. At 1,750 N axial load, the relative displacement of the fracture end of the three group was 0.70, 0.30 and 0.20 mm; the peak stress of the fracture end was 139.59, 37.57 and 4.17 MPa; the peak stress of internal fixation was 594, 421 and 393 MPa, respectively. At 2,100 N axial load, the relative displacement of the fracture end of the three internal fixation methods was 0.85, 0.35 and 0.23 mm; the peak stress of the fracture end was 170.05, 46.36 and 5.24 MPa; the peak stress of internal fixation was 724, 504 and 460 MPa, respectively.Conclusion:The partial direct reconstruction of medial support under the neck by DCS+MABP may have better biomechanical properties in the revision of medial defective intertrochanteric fractures.

Mises stress analysis of 42A2 type tibial mid segment oblique fracture fixed with external locking plate at different angles / 中国医师杂志

Objective:To establish a three-dimensional model of locking plate fixation for 42A2 type oblique tibial fractures with different fracture line directions and different angles between the fracture line and the long axis of the tibia. Finite element analysis was used to calculate and analyze the biomechanics of locking plate, screw, and tibia, providing theoretical basis for clinical application.Methods:A healthy adult volunteer, 25 years old, male, with a height of 173 cm and a weight of 69.5 kg, was selected to perform computed tomography (CT) scans on the left tibia. Relevant data were obtained to establish a locking steel plate fixation model for 42A2 type tibia with different oblique fracture line directions and different angles between the fracture line and the long axis of the tibia. Eight hole pure titanium plates were used for fixation, respectively. We compared the Mises stress changes of locking plates, screws, and tibia in different angle fracture models.Results:In the case of a 42A2 type fracture in the left oblique direction with a fracture line from outside to inside, the maximum Mises stress in the tibia was 114 MPa, the maximum Mises stress in the screw was 279.8 MPa, and the maximum Mises stress in the locking steel plate was 302.4 MPa; In the case of a 42A2 type fracture in the right oblique fracture with a fracture line from the bottom to the top, the maximum Mises stress of the tibia was 93.41MPa, the maximum Mises stress of the screw was 353.4 MPa, and the maximum Mises stress of the locking steel plate was 411.8 MPa.Conclusions:Regardless of the oblique fractures in both left and right directions, the maximum stress values are: locking plate>screw>tibia; When the position of the locking steel plate is fixed, the maximum stress values of the locking steel plate and screw are both right oblique fracture>left oblique fracture; And the maximum stress values all increase with the increase of angle.