Mechanical stress and melanoma: a retrospective analysis of 129 cases of plantar melanoma / 中华皮肤科杂志

Objective:To analyze potential roles of mechanical stress in the formation of plantar melanoma.Methods:A retrospective analysis was conducted on 129 cases of plantar melanoma in Xiangya Hospital, Central South University between 2014 and 2021, and the distribution and clinical characteristics of plantar melanoma were analyzed. The goodness-of-fit test was used to compare the distribution of plantar melanoma between weight-bearing areas (the toes, forefoot, lateral midfoot, heel) and non-weight-bearing areas of the foot (the arch) , while t test, Fisher′s exact test and Wilcoxon rank sum test were used to analyze differences in clinicopathological characteristics of plantar melanoma between weight-bearing areas and non-weight-bearing areas of the foot. Results:Among the 129 patients with plantar melanoma, 66 (51.2%) were males and 63 (48.8%) were females, and their age at onset was 60.6 ± 13.1 years. Plantar melanoma mostly occurred on the heel (65 lesions, 1.31 lesions per square centimeter) , followed by the forefoot (31 lesions, 0.41 lesions per square centimeter) , the bottom of the toes (15 lesions, 0.43 lesions per square centimeter) , lateral midfoot (11 lesions, 0.38 lesions per square centimeter) and the arch of foot (7 lesions, 0.16 lesions per square centimeter) . The goodness-of-fit test showed that melanoma was more prone to occur in the weight-bearing areas than in the non-weight-bearing areas ( χ2 = 66.59, P < 0.001) ; compared with the arch of foot, a higher incidence density was observed in the heel and forefoot ( χ2 = 38.29, 5.23, P < 0.001, = 0.022, respectively) . There were no significant differences in the gender ratio, age and occupation of patients, prevalence rates of left/right foot involvement, Breslow thickness, ulceration status, Clark grades, lymph node metastasis rate, and stages between melanomas in the weight-bearing areas and those in non-weight-bearing areas (all P > 0.05) . Conclusion:Plantar melanoma was more prone to occur in the weight-bearing areas than in the non-weight-bearing areas, suggesting that mechanical stress may be related to the occurrence and development of melanoma.

Research progress concerning the signaling pathway mechanisms related to mechanical stress-induced bone regeneration / 中华创伤骨科杂志

Elucidation of the signaling pathway mechanisms related to the mechanical stress-mediated bone regeneration is of great significance for improvement of bone regeneration and clinical treatment of bone-related diseases such as bone defects and bone elongation. Mechanical stress transmits mechanical stimuli into cells through the piezo channels and integrins, causing a variety of signaling pathway responses, which in turn changes transcription factor translocation, gene expression, and osteoblast differentiation to promote bone regeneration ultimately. This article reviews the research progress concerning the mechanisms related to mechanical stress-mediated bone tissue regeneration.

Analysis of the mechanical behavior of the posterior cruciate ligament in a porcine model / Análise do comportamento mecânico do ligamento cruzado posterior em modelo suíno

ABSTRACT Introduction: The knee has shown a significant increase in the frequency of injury due to sports practice. This increase and the improvement of surgical techniques of ligament reconstruction have led to a greater indication of this treatment to achieve a function close to normal. Objective: To conduct a preliminary analysis of the ligament behavior. Methods: The study consisted of the validation of an anatomical model of the pig, in which five models were subjected to mechanical tests. The data on the loads of the in situ model and the strains of the posterior cruciate ligament were collected. Results: The analysis of the tensile load showed, at first, a nonlinear increase in stresses. Subsequently, the pig's knee showed a relatively linear intermediate response until failure around 1,200 N. Strain × time showed a response of the posterior cruciate ligament, which also has a relatively linear response. Conclusion: We observed a linear behavior in the range of 1,000 to 5,000 microstrains in the strain of the posterior cruciate ligament. We suggest further studies to understand knee ligaments regarding their behavior in their function. Level of Evidence IV, Biomechanical Study.

RESUMO Introdução: O joelho tem demonstrado um aumento significativo de frequência de lesão devido à prática esportiva. Esse aumento e a melhoria das técnicas cirúrgicas de reconstrução ligamentar têm levado a maior indicação desse tratamento com o objetivo de se atingir uma função próxima do normal. Objetivo: Realizar uma análise preliminar do comportamento ligamentar. Métodos: O estudo consistiu na validação de um modelo anatômico do porco, em que cinco modelos foram submetidos a ensaios mecânicos. Foram coletados os dados das cargas do modelo in situ e das deformações do ligamento cruzado posterior. Resultados: Na análise da carga trativa, foi observado que em um primeiro momento existe um aumento não linear das tensões. Em sequência, há uma resposta intermediária relativamente linear do joelho suíno até a falha em torno de 1.200 N. A deformação versus tempo mostrou uma resposta do ligamento cruzado posterior, que também possui uma resposta relativamente linear. Conclusão: Observou-se um comportamento linear na faixa de 1.000 até 5.000 microstrains na deformação do ligamento cruzado posterior. Sugerem-se novos estudos para a compreensão dos ligamentos do joelho quanto ao comportamento deles na sua função. Nível de Evidência IV, Estudo Mecânico.

Mecanosensores en el cambio de fenotipo de la musculatura lisa vascular / Mechanosensors and phenotype changes in vascular smooth muscle

Resumen: Introducción: Las células de la musculatura lisa vascular (CMLV) se caracterizan por mantener cierto grado de desdiferenciación, variando su fenotipo entre el contráctil y el secretor, de acuerdo con las necesidades del tejido, y el contráctil predominante en condiciones fisiológicas. Cualquier alteración del estímulo mecánico, ya sea en el flujo sanguíneo o la tensión mecánica ejercida sobre las CMLV, conducen a cambios de su fenotipo y remodelamiento de la vasculatura, lo que puede constituir el punto de inflexión de varias patologías relevantes en la salud pública como, por ejemplo, la hipertensión arterial. Objetivo: Realizar una revisión sobre los mecanosensores y las vías transduccionales conocidas e implicadas en el cambio de fenotipo de las CMLV. Metodología: Se realizó una búsqueda sistemática en las bases de datos PubMed, Scopus, Google Académico y Scielo sobre la mantención y cambio de fenotipo de las células de la musculatura lisa vascular asociado principalmente a el estrés mecánico, la participación de los mecanosensores más relevantes y las vías de señalización involucrados en este proceso. Conclusión: Los mecanosensores implicados en el cambio de fenotipo de las CMLV contemplan principalmente receptores acoplados a proteína G, moléculas de adhesión y canales iónicos activados por estiramiento. Los estudios se han concentrado en la activación o inhibición de vías como las proteínas quinasas activadas por mitógenos (MAPK), la vía AKT, mTOR y factores transcripcionales que regulan la expresión de genes de diferenciación y/o desdiferenciación, como las miocardinas. Existen además otros receptores involucrados en la respuesta al estrés mecánico, como los receptores tirosina quinasas. A pesar de la importancia que reviste el conocimiento de los mecanosensores y las vías implicadas en el cambio de fenotipo de las CMLV, así como el papel que cumplen en el establecimiento de patologías vasculares, es aún escaso el conocimiento que se tiene sobre los mismos.

Abstract: Introduction: Vascular smooth muscle cells (VS- MCs) are characterized by maintaining a certain de- gree of dedifferentiation. VSMCs may vary their phenotype between contractile and secretory according to tissue needs. Under physiological conditions, the predominant phenotype is contractile. Any alteration of the mechanical stimulus, either in the blood flow or the mechanical stress exerted on the VSMCs, leads to changes in their phenotype and remodeling of the vasculature. These changes can constitute the turning point in several hypertension and other diseases relevant in public health. Objective: To review the main mechanosensor and transduction pathways involved changes in VSMCs phenotype. Methods: A systematic search of PubMed, Scopus, Google Scholar and Scielo databases was carried out to ascertain the state of the art regarding the maintenance and change of VSMCs phenotype mainly associated with mechanical stress. Additionally, the participation of the most relevant mechanosensors and the signaling pathways involved in this process are discussed. Conclusion: The mechanosensors involved in the change in VSMCs phenotype mainly contempla- te G-protein-coupled receptors, adhesion molecules, and stretch-activated ion channels. Studies have been focused on the activation or inhibition of MAPK, AKT, mTOR, pathways and transcriptional factors that regulate the expression of differentiation and/or des differentiation genes such as Myocardins. There are also other receptors involved in the response to mechanical stress such as the tyrosine kinases receptor. Although the importance of understanding mechanosensors, the signaling pathways involved in VSMC phenotype switching and their role in the establishment of vascular pathologies, knowledge about them is limited.

Effect of microrna-132-3p overexpression onproliferation and osteogenic differentiation of mc3t3-e1 cells / 中国组织工程研究

BACKGROUND: Mechanical stress can influence the proliferation and differentiation of MC3T3-E1 cells and trigger differential expression of miR-132-3p. However, further research is warranted concerning whether tensile stress can influence the proliferation and differentiation of osteoblasts by regulating miR-132-3p. OBJECTIVE: To determine the expression of osteogenic differentiation markers and miR-132-3p in MC3T3-E1 cells under 12% cyclic stretch and to explore the effect of miR-132-3p on cell proliferation and differentiation. METHODS: MC3T3-E1 cells were loaded with 0% and 12% tensile stress, and alkaline phosphatase activity, osteocalcin mRNA and miR-132-3p expression levels were detected. MC3T3-E1 cells were transiently transfected with miR-132-3p mimics and a negative control transfection group was set up. The expression of alkaline phosphatase, osteocalcin and Runx2 mRNA in transfected cells were detected by qRT-PCR, and the effect of miR-132-3p on cell proliferation were detected by cell counting kit-8 assay. RESULTS AND CONCLUSION: The alkaline phosphatase activity and osteocalcin mRNA expression were down-regulated in MC3T3-E1 cells under 12% stretch stress (P < 0.01), and the expression of miR-132-3p was significantly increased (P < 0.05). QRT-PCR results showed the expression levels of osteogenic differentiation markers alkaline phosphatase activity, osteocalcin, and Runx2 mRNA in miR-132-3p mimics group were significantly decreased after intracellular transfection of miR-132-3p (P < 0.05). Compared with the negative control transfection group, the cell proliferation in the miR-132-3p mimic group was decreased at 24, 48, and 72 hours after transfection (P < 0.001), and the most obvious reduction was observed after 48-hour transfection. These findings indicate that 12% cyclic tensile stress can negatively regulate the proliferation and differentiation ability of MC3T3-E1 cells by overexpressing miR-132-3p.

Mechanism underlying mechanical stress regulating fibroblasts-derived exosomes at the osteotomized end following hallux valguscorrection / 中国组织工程研究

BACKGROUND: Bandage internal fixation (defined as the interphalangeal insertion of “8”-shaped bandage for elastic external fixation) produces a suitable mechanical environment for bone healing after minimally invasive treatment of hallux valgus. Stress stimulation is essential for bone healing after osteotomy, but the mechanism is still unclear OBJECTIVE: To study the regulatory mechanism of mechanical stress on fibroblasts-derived exosomes. METHODS: The medial bone tissue of the first metatarsal bone obtained in the surgery for hallux valgus was taken as a specimen. The fibroblasts were passaged in vitro via direct tissue adherent culture. The loading system provided a cell strain simulating external fixation using “8”-shaped bandage for the pressure-loading culture of hallux valgus fibroblasts, and then exosomes were extracted. Size distribution, morphology and markers of exosomes were detected by electron microscopy, nanoparticle tracking analysis and western blot assay. The study protocol was approved by the Ethics Committee of Wangjing Hospital of China Academy of Chinese Medical Sciences with approval No. 2013-03-21 on March 21, 2013. RESULTS AND CONCLUSION: Static stretching (15%) could promote the secretion of exosomes from fibroblasts. The expression of CD9 and CD81 was detected in the fibroblasts-derived exosomes of the control group and the experimental group. Range of exosome particle size distribution was consistent in the two groups of exosomes, and 15% static stretching increased the concentration of exosomes. This indicates that 15% static stretching helps fibroblasts secrete growth factors, which in turn contribute to osteoblast osteogenesis.

Mechanism of dna methylation in exercise intervention for osteoporosis / 中国组织工程研究

BACKGROUND: The dynamic balance between bone formation mediated by osteoblasts and bone resorption mediated by osteoclasts is the basis for maintaining the stability of the body’s bone tissue. The metabolic imbalance between them can cause bone loss and fine structure degeneration of the bone cells, leading to osteoporosis. OBJECTIVE: To review the role of DNA methylation in osteoporosis and to explore the mechanism of exercise affecting DNA methylation and DNA methylation regulating bone metabolism. METHODS: A computer-based search of PubMed and CNKI databases was performed for relevant articles published from January 2002 to April 2020 with “DNA methylation; Osteoporosis; Exercise intervention; Mechanical stress; Osteogenic differentiation” as key words in English and Chinese, respectively. Initially, finally 52 eligible articles were included for result analysis. RESULTS AND CONCLUSION: DNA methylation is a relatively conservative and stable apparent modification, which regulates gene expression, silencing and disease occurrence. Studies have shown that reduced methylation levels of genes such as β-catenin, Runx2, osteopontin (OPG) can promote their expression and activate Wnt Pathway, whereas the reduction of methylation level of Sclerosin, receptor activator of nuclear factor kappa B ligand (RANKL) and other genes can promote their expression, and inhibit Wnt pathway and reduce the ratio of OPG/RANKL, thereby affecting the proliferation, differentiation and function of osteoblasts and osteoclasts, and accordingly regulating dynamic equilibrium between bone formation and bone resorption. Osteoblasts and osteoclasts act as sensitive cells for mechanical stimulation. Bone can transform the mechanical load generated by exercise into biological stimulation that acts on the differentiation and function of related bone cells, thereby regulating bone metabolism. In vitro experiments have indicated that different forms of mechanical stress stimulations can change the methylation level of genes such as OPN and GNAS1 to regulate their expression, which has a positive effect on bone formation. Bone tissue is a mechanically sensitive tissue, and DNA methylation can regulate bone metabolism by regulating a variety of factors.

Fatiga cíclica de cuatro sistemas reciprocantes en una canaleta dinámica de raíces simuladas / Cyclical fatigue of four reciprocating systems in a dynamic dump of simulating roots / Fadiga cíclica de quatro sistemas reciprocantes em uma com canais simulados

En conductos radiculares curvos, la utilización de limas que eviten desvíos y fracturas del instrumento por fatiga y que mantengan curvaturas originales son aspectos importantes en el tratamiento endodóntico. Ob-jetivo: Se evaluó la resistencia a la fatiga cíclica de cuatro sistemas reciprocantes en una canaleta dinámica que simuló tres curvaturas diferentes. Materiales y Método: Estudio in vitro; la muestra con 48 limas se dividió en cuatro grupos (n= 12/grupo): WaveOne® (WO), WaveOne® Gold (WOG), Reciproc® (R) y Reciproc® Blue (RB), cuatro limas de cada sistema se usaron en una canaleta que simuló tres angulaciones 45°, 60° y 90°; montadas en un motor X-Smart Plus®, las limas se introdujeron 23 mm en los conductos para ser activadas continuamente a 300/500 oscilaciones/minuto hasta que se produjo la fractura. Se registró tiempo y zona de fractura. Se realizó el test Kruskal Wallis con un nivel de confianza del 95% para las comparaciones. Resul-tados: RB presentó mayor resistencia a la fatiga cíclica que WO y WOG en todas las angulaciones y que R a 90° (p= <0,05). R presentó mayor resistencia que WOG a 45° y 60°, sin embargo, a 90° WOG fue superior que R y WO (p<0,05). No hubo diferencias en cuanto a la zona de fractura que aconteció en la porción apical. Conclusiones: La resistencia se reduce cuando aumenta el grado de curvatura. RB fue significativamente más resistente a la fatiga cíclica que WO y WOG en todas las angulaciones y que R a 90°. La zona de fractura se produjo en la porción apical de las limas.

In the curved canals, the use of files that avoid deviations and fractures of the instrument due to fatigue and that maintain original curvatures are important aspects in endodontic treatment. Objective: The resistance to cyclic fatigue of four reciprocating systems was evaluated in a dynamic gutter that stimulated three different curvatures. Materials and Method: In vitro study, the sample with 48 files was divided into four groups (n = 12 /group): WaveOne® (WO), WaveOne® Gold (WOG), Reciproc® (R) and Reciproc® Blue (RB), four files from each system were used in a gutter that simulated three angulations 45o , 60 o and 90 o . The files which were mounted on an X-smart Plus® were inserted 23 mm into the conduits to be continuously activated at 300/500 oscillations per minute until the fracture occurred. Time and fracture zone were recorded. The Krustal Wallis test was performed with a 95% confidence level for the comparisons. Results: RB presented greater resis-tance to cyclic fatigue than WO and WOG at 45o and 60o, however, at 90o WOG was higher than R and WO (p<0.05). There were no differences regarding the fracture zone occurred in the apical portion. Conclusions: The resistance decreases when the degree of curvature increases. RB was significantly more resistance to cyclic fatigue than WO and WOG at all angulations and R at 90o. The fracture zone occurred in the apical portion of the files.

Em canais radiculares curvos, o uso de limas que evitem desvios e fraturas do instrumento devido à fadiga e que mantêm as curvaturas originais são aspectos importantes no tratamento endodôntico. Objetivo: avaliar a resistência à fadiga cíclica de quatro sistemas reciprocantes em uma canaleta artificial que simula três curva-turas diferentes. Materiais e Método: estudo in vitro; a amostra com 48 limas foi dividida em quatro grupos (n = 12 / grupo): WaveOne® (WO), WaveOne® Gold (WOG), Reciproc® (R) e Reciproc® Blue (RB), quatro limas de cada sistema foram usadas em uma canaleta que simulo três angulações 45 °, 60 ° e 90 °; se montaram em um motor X Smart Plus®, as limas foram inseridas 23 mm nos condutos para serem ativadas continuamente a 300/350 oscilações / minuto até ocorrer uma fratura. O tempo e a zona de fratura foram registrados. O teste de Kruskal Wallis foi realizado com um nível de confiança de 95% para as comparações. Resultados: O RB apresenta maior resistência à fadiga cíclica que o WO e o WOG em todas as angulações e que R a 90 ° (p = <0,05). R apresentou maior resistência que WOG a 45 ° e 60 °, no entanto, a 90 ° WOG foi maior que R e WO (p <0,05). No existiu diferença na zona de fratura que ocorreu na porção apical. Conclusões: a resistência diminui quando o grau de curvatura aumenta. RB foi significativamente mais resistente à fadiga cíclica do que WO e WOG em todos os ângulos e R a 90 °. A zona de fratura ocorre na parte apical das limas.

Lesão aguda da parede arterial provocada pelo método de interrupção temporária de fluxo em diferentes vias de cirurgia aórtica: estudo morfológico e biomecânico da aorta de porcos / Acute aortic wall injury caused by aortic cross-clamping: morphological and biomechanical study of the aorta in a swine model of three aortic surgery approaches

Resumo Contexto O clampeamento aórtico e a oclusão da aorta com balão poderiam levar a lesões na parede aórtica. Objetivo O objetivo deste estudo foi verificar as alterações da parede aórtica relacionadas ao método de interrupção de fluxo (cample ou balão) em diferentes técnicas disponíveis para cirurgia de aorta. Métodos Os experimentos foram realizados em 40 porcos fêmeas pesando de 25-30 kg, alocados para quatro grupos: S (n = 10), nenhuma intervenção (sham); C (n = 10), laparotomia mediana transperitoneal para acesso à aorta abdominal infrarrenal com tempo de clampeamento de 60 minutos; L (n = 10), cirurgia laparoscópica da aorta abdominal infrarrenal com tempo de clampeamento de 60 minutos; EV (n = 10), controle aórtico proximal com inserção de cateter-balão para oclusão aórtica por acesso femoral, inflado a fim de promover oclusão aórtica contínua por 60 minutos. Após a eutanásia, as aortas foram removidas e seccionadas para obtenção de espécimes histológicos destinados a análises morfométricas e por microscopia de luz. Os fragmentos longitudinais restantes foram estirados até a ruptura, e determinaram-se padrões mecânicos. Resultados Observou-se redução do limite de proporcionalidade da aorta abdominal, diminuição da rigidez e da carga de ruptura nos grupos submetidos a campleamento aórtico (C e L) em comparação ao grupo EV. Conclusões O campleamento aórtico durante cirurgia aberta ou laparoscópica pode afetar as propriedades mecânicas da aorta, ocasionando redução de resistência da parede aórtica sem desencadear alterações na estrutura histológica da parede aórtica.

Abstract Background Aortic cross-clamping and balloon occlusion of the aorta could lead to damage to the aorta wall. Objective The aim of this study was to investigate changes to the aorta wall related to the method used to interrupt flow (clamping or balloon) in the different techniques available for aortic surgery. Methods Experiments were performed on 40 female pigs, weighing 25-30kg, which were randomly allocated to 4 study groups: S (n=10), no intervention (sham group); C (n=10), midline transperitoneal laparotomy for infrarenal abdominal aortic access with 60 min of cross-clamping; L (n=10), laparoscopic infrarenal abdominal aortic surgery with 60 min of cross-clamping; EV (n=10), remote proximal aortic control with transfemoral arterial insertion of aortic occlusion balloon catheter, inflated to provide continued aortic occlusion for 60min. After euthanasia, the aortas were removed and cross-sectioned to obtain histological specimens for light microscopic and morphometric analyses. The remaining longitudinal segments were stretched to rupture and mechanical parameters were determined. Results We observed a reduction in the yield point of the abdominal aorta, decrease in stiffness and in failure load in the aortic cross-clamping groups (C and L) compared with the EV group. Conclusions Aortic cross-clamping during open or laparoscopic surgery can affect the mechanical properties of the aorta leading to decrease in resistance of the aorta wall, without structural changes in aorta wall histology.

Interfacial properties and bottom/top hardness ratio produced by bulk fill composites in dentin cavities

Abstract The aim of this study was to evaluate the bond strength, bottom/top hardness ratio, marginal adaptation, and interfacial nanoleakage of regular viscosity bulk fill composites (RVBFC) and regular viscosity traditional composites (RVTC). Two RVBFC (Filtek Bulk Fill and Aura Bulk Fill) and two RVTC (Filtek Z250XT and Aura) were assessed. Forty conical cavities (4.8×2.8×4.0) were prepared in bovine dentin and restored with composites (n=10). After 24h in water, marginal adaptation was evaluated by staining with a caries detector. The top and bottom surfaces of the conical restorations were stained for five seconds and the gap percentage in the composite/dentin interface was determined using digital images on a measurement program (ImageTool). The Vickers microhardness was measured and the bottom/top microhardness ratio (B/T) was determined. Push-out bond strength test was performed in a universal testing machine (0.5mm/min) and failure modes were evaluated in a stereomicroscope (20×). Other specimens (n=3) were produced for interfacial nanoleakage evaluation. Data were analyzed using one and two-way ANOVA and Tukey's test (α=0.05). The gap percentage was higher in the bottom compared to the top. The B/T ratio of the Aura Bulk Fill was statistically lower than other composites. Push-out bond strength were similar among composites. The RVBFC presented lower nanoleakage than the RVTC in the bottom of the conical restoration and there was no difference among the materials in the top surfaces. In conclusion, Filtek Bulk Fill performed better than Aura Bulk Fill regarding the analyzed properties.

Resumo O objetivo deste estudo foi avaliar a resistência de união, razão base/topo de microdureza, adaptação marginal e nanoinfiltração interfacial de resinas compostas bulk fill (BF) e tradicional (RT) de viscosidade regular.: Duas BF (Filtek Bulk Fill e Aura Bulk Fill) e duas RT (Filtek Z250XT e Aura) foram testados. Quarenta cavidades cônicas (4,8×2,8×4,0) foram preparadas em dentina bovina e restauradas com os compósitos (n=10). Depois de 24 h em água, a adaptação marginal foi avaliada por meio do corante com detector de cárie. As faces de topo e base das restaurações cônicas foram coradas por cinco segundos e a porcentagem de fendas na interface compósito/dentina foi determinada utilizando-se imagens analisadas num programa (ImageTool). A microdureza Vickers foi mensurada e a razção base/topo de microdureza (B/T) foi determinada. A resistência de união por push-out foi executada numa máquina de ensaios universal (0,5mm/min) e o padrão de fratura avaliado num estereomicroscópio (20x). Espécimes adicionais (n=3) foram confeccionados para avaliação da nanoinfiltração interfacial. Os dados foram analisados por meio de ANOVA a dois fatores e teste de Tukey (a=0,05). A porcentagem de fendas foi maior na base que no topo. A B/T da Aura Bulk Fill foi estatisticamente menor que os demais compósitos. A resistência de união por push-out foi similar entre os compósitos. As BF apresentaram menos nanoinfiltração que as RT na base das restaurações cônicas e não houve diferenças entre os materiais no topo. Conclui-se que a Filtek Bulk Fill comportou-se melhor que a Aura Bulk Fill considerando-se as propriedades analisadas.

Stress analysis of maxillary central incisors endodontically -treated with varying ferrule heights and three different post dowel materials - a finite element analysis / Análisis de tensión de los incisivos centrales superiores tratados endodónticamente con diferentes alturas de férula y tres materiales diferentes de clavija posterior: un análisis de elementos finitos

Statement of problem : fracture of endodontically treated teeth is reduced by the use of a post with ferrule, but the effect of different ferrule configurations and dowel materials is not clear. Purpose: to evaluate the effect of ferrules with different configurations and heights on the stress of endodontically treated teeth restored with three different post and dowel materials. Materials and Methods: fifteen models of maxillary central incisors restored with porcelain fused to metal crowns were obtained using pro engineer software. the models were divided into three groups, each consisting of five models with ferrule heights of 0mm, 2mm, 4mm, 2mm with oblique fracture, 4mm with oblique fracture, the models under group GFR were restored with fiberglass reinforced post (GFR) and composite core build-up, group NiCr with a custom cast post metal alloy (NiCr), and group Zr with zirconia post (Zr) and composite core build-up. an oblique load of 100N and 150N at an angle of 135 degrees was applied to the palatal surface of the tooth, a vertical load of 100N and 150N at an angle of 90 degrees was applied to the incisal tip of the tooth. The maximum principal stress and the von mises stress was calculated for the remaining tooth structure and post apex using the finite element analysis (FEA) software. Results: the maximum von misses stress was observed in the apex of the post (p<0.05). Group Zr showed the highest mean stress (6.39Mpa) followed by group NiCr (5.65Mpa). There was a significant difference between post and between NiCr and Zr post for 2mm and 4mm ferrule height, while for 0mm ferrule there was a significant difference between the GFR and NiCr groups (p<0.05). Under oblique load, the maximum mean stress was observed in remaining tooth structures while for vertical load, it was observed at the apex of the post. Regarding ferrule heights, there were significant differences between 0mm-2mm, and 0mm-4mm uniform ferrule in post apex in the case of NiCr posts (p<0.05). Absence of ferrule resulted in higher stress for the NiCr group. Conclusion: higher loads that led to fracture were observed only at the apex of the post. Zirconia posts (group Zr) had higher fracture loads, whereas absence of ferrule resulted in higher fracture load with custom cast posts (group NiCr). Fracture thresholds were high on the remaining tooth structure for all the dowel systems especially for composite core build up irrespective of ferrule height and configuration. Clinical implications: appropriate selection of post and dowel materials in different configurations of ferrule heights ensures clinical success.

Indicación del problema: la fractura de los dientes tratados endodónticamente se reduce mediante el uso de un poste con férula, pero el efecto de diferentes configuraciones de férula y materiales de clavija no está claro. Propósito: evaluar el efecto de los casquillos con diferentes configuraciones y alturas sobre el estrés de los dientes tratados endodónticamente restaurados con tres materiales diferentes de postes y tacos. materiales y métodos: quince modelos de incisivos centrales superiores restaurados con porcelana fundida a coronas de metal se obtuvieron con el software Pro Engineer. Los modelos se dividieron en tres grupos, cada uno de los cuales consta de cinco modelos con alturas de casquillo de 0mm, 2mm, 4mm, 2mm con fractura oblicua, 4mm con fractura oblicua. los modelos del grupo GFR fueron restaurados con poste reforzado con fibra de vidrio (GFR) y acumulación de núcleo compuesto, grupo nicr con una aleación de metal de poste fundido personalizado (NiCr) y grupo Zr con poste de zirconia (Zr) y acumulación de núcleo compuesto. se aplicó una carga oblicua de 100N y 150N en un ángulo de 135º a la superficie palatina del diente. se aplicó una carga vertical de 100N y 150N en un ángulo de 90º a la punta incisal del diente. la tensión principal máxima y la tensión de von mises se calcularon para la estructura dental restante y después del vértice utilizando el software de análisis de elementos finitos (FEA). Resultados: el estrés máximo de von falta se observó en el vértice de la publicación (p<0.05). El grupo Zr mostró el mayor estrés medio (6.39Mpa) seguido del grupo NiCr (5.65Mpa). Hubo una diferencia significativa entre la publicación NiCr y Zr para la altura de la férula de 2mm y 4mm, mientras que para la férula de 0mm hubo una diferencia significativa entre los grupos GFR y NiCr (p<0,05), bajo la carga oblicua, la tensión media máxima en las estructuras dentales restantes, mientras que para la carga vertical, se observó en el vértice del poste. En cuanto a las alturas de la férula, hubo diferencias significativas entre la férula uniforme de 0mm-2mm y de 0mm-4mm en el post-apex en el caso de los postes de NiCr (p<0.05), la ausencia de férula dio como resultado un mayor estrés para el grupo NiCr. Conclusión: las cargas más altas que llevaron a la fractura se observaron solo en el vértice del poste; Los postes de zirconia (grupo Zr) tuvieron mayores cargas de fractura, mientras que la ausencia de férula dio como resultado una mayor carga de fractura con postes moldeados personalizados (NiCr de grupo). Los umbrales de fractura fueron altos en la estructura dental restante para todos los sistemas de clavijas, especialmente para la acumulación de núcleos compuestos independientemente de la altura y configuración de la férula. Implicaciones clínicas: la selección adecuada de materiales de postes y tacos en diferentes configuraciones de alturas de férulas asegura el éxito clínico.

Effect of sclerostin on the functions and related mechanisms of cementoblasts under mechanical stress / 华西口腔医学杂志

OBJECTIVE@#The purpose of this study is to investigate the potential effects of sclerostin (SOST) on the biological funtions and related mechanisms of cementoblasts under mechanical stress.@*METHODS@#OCCM-30 cells were treated with varying doses of SOST (0, 25, 50, and 100 ng·mL⁻¹) and were loaded with uniaxial compressive stress (2 000 μ strain with a frequency of 0.5 Hz) for six hours. Western blot was utilized to detect the expressions of β-catenin, p-smad1/5/8, and smad1/5/8 proteins. Alkaline phosphatase (ALP) activity was determined, and reverse transcription polymerase chain reaction was used to measure the expressions of runt-related transcription factor 2 (Runx-2), osteocalcin (OCN), bone sialoproteins (BSP), receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) mRNA.@*RESULTS@#The expression of p-smad
1/5/8 was significantly downregulated with increasing SOST. β-catenin and smad1/5/8 exhibited no difference. ALP activity decreased under mechanical compressive stress with increasing SOST concentrations. Runx-2 expression was reduced with increasing SOST concentrations, and a similar trend was observed for the BSP and OCN expressions. When the SOST concentration was enhanced, RANKL expression gradually increased, whereas the expression of OPG decreased.@*CONCLUSIONS@#Under mechanical comprehensive stress, SOST can adjust the bone morphogenetic protein (BMP) /smad signal pathway. Osteosclerosis inhibits the mineralization of cementoblasts under mechanical compressive stress, which may be achieved by inhibiting the expressions of osteogenesis factors (Runx2, OCN, BSP, and others) and by promoting the ratio of cementoclast-related factors (RANKL/OPG) through BMP signal pathways.

Internal mechanical work and maximum subtalar joint pronation in different gradients / Trabalho mecânico interno e máxima pronação subtalar em diferentes gradientes de inclinação / Trabajo mecánico interno y máxima pronación subtalar en diferentes gradientes de inclinación

Abstract Introduction: Some authors have described the importance of physiological intensity in the behavior of the biomechanical aspects of running (for example, subtalar pronation), but the complex relationships between these variables are not yet well understood. Objective: This study investigated the influence of positive gradients on internal mechanical work (Wint) and maximum subtalar pronation at a submaximal running speed. Method: Sixteen male, trained long-distance runners (age: 29 ± 7 yr; stature: 1.72 ± 0.07 m; body mass: 72.1 ± 10.6 kg), performed four running economy tests (gradients: +1%, +5%, +10% and +15%, respectively) for four minutes at a same submaximal running speed to quantify the maximum values of subtalar pronation and predict the Wint values. Data were analyzed using descriptive statistics, Student's T-test, and one-way repeated-measures (ANOVA) along with the Statistical Package for the Social Sciences (SPSS) version 20.0. Results: Wint increased according to the gradient (p < 0.05). However, no significant differences were observed in the maximum values of maximum subtalar pronation corresponding to each gradient. Conclusion: Results show the maximum subtalar pronation during submaximal running depends on the speed rather than intensity of effort.

Resumo Introdução: Autores têm descrito a importância da intensidade fisiológica no comportamento dos aspectos biomecânicos da corrida (por exemplo, a pronação subtalar), mas as complexas relações entre essas variáveis todavia não estão bem compreendidas. Objetivo: O presente estudo investigou a influência de gradientes de inclinação positivos, a uma mesma velocidade de corrida, no trabalho mecânico interno (Wint) e na máxima pronação subtalar. Método: Dezesseis corredores masculinos, especialistas em longas-distâncias (idade: 29 ± 7 anos; estatura: 1,72 ± 0,07 m; massa corporal: 72,1 ± 10,6 kg) realizaram quatro testes de economia de corrida (gradientes: +1%, +5%, +10% e +15%, respectivamente), de quatro minutos cada, em uma mesma velocidade submáxima de corrida, objetivando quantificar os valores de máxima pronação subtalar e predizer os Wint. Foi realizada a análise descritiva e aplicados os testes T de Students e ANOVA de Medidas Repetidas, todos através do software Statistical Package for the Social Sciences (SPSS), versão 20.0. Resultados: O Wint aumentou com o gradiente (p < 0,05). Entretanto, diferenças estatisticamente significativas não foram observadas nos valores de máxima pronação subtalar correspondentes a cada gradiente. Conclusão: Os resultados do presente estudo revelam que a máxima pronação subtalar durante a corrida submáxima é dependente da velocidade em comparação a intensidade de esforço.

Resumen Introducción: Autores tienen descrito la importancia de la intensidad fisiológica en el comportamiento de los aspectos biomecánicos de la carrera (por ejemplo, la pronación subtalar), mas las complejas relaciones entre esas variables todavía no están bien comprendidas. Objetivo: El presente estudio investigó la influencia de gradientes de inclinación positivos, a una misma velocidad de carrera, en el trabajo mecánico interno (Wint) y en la máxima pronación subtalar. Método: Dieciséis corredores masculinos, especialistas en largas-distancias (edad: 29 ± 7 años; estatura: 1,72 ± 0,07 m; masa corporal: 72,1 ± 10,6 kg) realizaron cuatro testes de economía de carrera (gradientes: +1%, +5%, +10% e +15%, respectivamente), de cuatro minutos cada, en una misma velocidad submáxima de carrera, objetivando cuantificar los valores de máxima pronación subtalar y predecir los Wint. Fue realizada la análisis descriptiva y aplicados los testes T de Students y ANOVA de Medidas Repetidas, todos realizados en el software Statistical Package for the Social Sciences (SPSS), versión 20.0. Resultados: EL Wint aumentó con el gradiente (p < 0,05). Entretanto, diferencias estadísticamente significativas no fueran observadas en los valores de máxima pronación subtalar correspondientes a cada gradiente. Conclusión: Los resultados del presente estudio revelan que la máxima pronación subtalar durante la carrera submáxima es dependiente de la velocidad en comparación a la intensidad del esfuerzo.

A novel cannula for uniform mixing of liquid substances

Uniform mixing of liquid substances is difficult to attain. Recently, mixtures of fat and platelet-rich plasma (PRP) have been used extensively in autologous fat transfer. Although various methods have been utilized to mix the fat and PRP involved in this procedure, these methods still carry disadvantages in the time taken and the potential for cell damage, and it is questionable whether effective mixing can occur using these techniques. To facilitate mixing that is as uniform as possible, the authors of this study invented a special cannula. Use of the conventional luer-lock-to-luer-lock connector method has been found to cause cell damage and makes it difficult to achieve uniform mixing, while random injection-type mixing has been shown to have limited accuracy and effectiveness. We expect that the newly designed cannula will solve the problem detailed above.

Three-Dimensional Finite Element Analysis of Varying Diameter and Connection Type in Implants with High Crown-Implant Ratio

Abstract The aim of this study was to evaluate the effect of varying the diameter, connection type and loading on stress distribution in the cortical bone for implants with a high crown-implant ratio. Six 3D models were simulated with the InVesalius, Rhinoceros 3D 4.0 and SolidWorks 2011 software programs. Models were composed of bone from the posterior mandibular region; they included an implant of 8.5 mm length, diameter Ø 3.75 mm or Ø 5.00 mm and connection types such as external hexagon (EH), internal hexagon (IH) and Morse taper (MT). Models were processed using the Femap 11.2 and NeiNastran 11.0 programs and by using an axial force of 200 N and oblique force of 100 N. Results were recorded in terms of the maximum principal stress. Oblique loading showed high stress in the cortical bone compared to that shown by axial loading. The results showed that implants with a wide diameter showed more favorable stress distribution in the cortical bone region than regular diameter, regardless of the connection type. Morse taper implants showed better stress distribution compared to other connection types, especially in the oblique loading. Thus, oblique loading showed higher stress concentration in cortical bone tissue when compared with axial loading. Wide diameter implant was favorable for improved stress distribution in the cortical bone region, while Morse taper implants showed lower stress concentration than other connections.

Resumo O objetivo deste estudo foi avaliar o efeito da variação do diâmetro e dos tipos de conexão na distribuição do estresse no osso cortical para implantes com a proporção coroa-implante. Seis modelos 3D foram simulados com os programas InVesalius, Rhinoceros 3D 4.0 e SolidWorks 2011. Os modelos foram compostos de osso da região mandibular posterior. Foram incluídos implantes de 8,5 mm de comprimento, diâmetro Ø 3,75 mm ou Ø 5,00 mm, e tipos de conexão como hexágono externo (EH), hexágono interno (IH) e cone Morse (MT). Os modelos foram processados usando os programas Femap 11.2 e NeiNastran 11.0 e usando uma força axial de 200 N e força oblíqua de 100 N. Os resultados foram registrados em termos da tensão principal máxima. O carregamento oblíquo mostrou alta tensão no osso cortical em comparação com a carga axial. Os resultados mostraram que os implantes com maior diâmetro apresentaram distribuição de tensões mais favorável, independentemente do tipo de conexão, enquanto que os implantes cone Morse apresentaram melhores distribuição de tensões comparado aos outros tipos de conexão, especialmente no carregamento oblíquo. Assim, os implantes de maior diâmetro foram mais favoráveis para distribuição das tensões na região de tecido ósseo cortical, enquanto que os implantes cone Morse apresentam menores concentrações de tensões do que as outras conexões.

Evaluation of apoptosis and osteopontin expression in osteocytes exposed to orthodontic forces of different magnitudes

The in vivo response of osteocytes to different force magnitudes soon after they are applied remains to be elucidated. The aim of this study was to examine the early effects of applying a very light (LF: 0,16 N) and a very strong (SF: 2,26 N) orthodontic force during one hour on apoptosis and osteopontin (OPN) expression on alveolar bone osteocytes, in rats. Results: LF: compared to the control group, they showed a significant increase in OPN expression, and a significant decrease in the number of TUNELpositive osteocytes. SF: compared to the control group, they showed a significant increase in OPN expression and a significant decrease in the number of TUNELpositive osteocytes. Our results show that osteocytes respond very early to the application of tension and pressure forces of different magnitudes, and application of forces decreases the number of apoptotic osteocytes and increases OPN expression. These results allow concluding that osteocytes activate rapidly when subjected to locally applied forces, whether these forces be pressure or tension, light or strong forces. Grants: UBACyT 200201301002270 BA and School of Dentistry, University of Buenos Aires (AU)

Hasta el momento no se ha dilucidado la respuesta temprana in vivo de los osteocitos a la aplicación de fuerzas de diferentes magnitudes sobre el hueso. El objetivo de este estudio fue examinar la respuesta temprana de la aplicación de una fuerza ortodóncica muy liviana (FL: 0,16 N) y muy fuerte (FF: 2,26 N) durante una hora sobre la expresión de apoptosis y osteopontina (OPN) en los osteocitos del hueso alveolar, en ratas. Resultados: FL: en comparación con el grupo control, mostraron un aumento significativo en la expresión de OPN y una disminución significativa en el número de osteocitos TUNELpositivos. FF: en comparación con el grupo control, mostraron un aumento significativo en la expresión de OPN y una disminución signi ficativa en el número de osteocitos TUNELpositivos. Nuestros resultados muestran que los osteocitos responden muy temprano a la aplicación de fuerzas de tensión y presión de diferentes magnitudes, y la aplicación de fuerzas disminuye el número de osteocitos apoptóticos y aumenta la expresión de OPN. Estos resultados permiten concluir que los osteocitos se activan rápidamente cuando se los somete a fuerzas aplicadas localmente, ya sean estas fuerzas de presión o tensión, livianas o fuertes (AU)

The effect of mechanical stretching stress on the proliferation, apoptosis of degenerative disc nucleus pulposus cells and expression of extracellular matrix / 中华物理医学与康复杂志

Objective To observe in vitro the effect of mechanical stress at different intensities on the pro-liferation, apoptosis and extracellular matrix of degenerative human nucleus pulposus cells. Methods The cells were isolated and cultured in vitro, and divided into a control group, a low-intensity group, a medium-intensity group and a high-intensity group. The low-, medium- and high-intensity groups were stretched mechanically by 1000 μ, 2000μor 4000μrespectively for 6 hours using a four-point bending system, while the control group was not stressed. Flow cytometry was used to explore any changes in the cell cycle and the proliferation index ( PI) . The expression of proliferating cell nuclear antigen ( PCNA) , B-cell lymphoma-2 ( BCL-2)/Bax, collagen II and aggrecan were meas-ured using real-time quantitative polymerase chain reactions. Results The mechanical stretching significantly influ-enced proliferation, apoptosis and the extracellular matrices compared with the control group. The PI and PCNA ex-pression increased at first and then decreased gradually with the exercise intensity. Compared with the control group, the mRNA expression level of Bcl-2/Bax increased significantly to 1.53 times that of the control group after 1000 μstretching, but to only 0.71 times that of the control group at 2000μand 0.43 times at 4000μ. The gene expression of collagen II increased significantly by 1. 1 times and that of aggrecan by 1. 3 times after 1000 μ stress stimulation compared with the control group ( P≤0.05) . However, the expression of collagen II and aggrecan was inhibited sig-nificantly at 2000 and 4000 μ , with the lowest levels at 4000 μ (P≤0.05). Conclusion Stretching at different intensities has different effects on the proliferation, apoptosis and extracellular matrix of human pulposus cells with degenerate nuclei.

Distribution of stress on TMJ disc induced by use of chincup therapy: assessment by the finite element method

ABSTRACT Objective: To assess the distribution of stress produced on TMJ disc by chincup therapy, by means of the finite element method. Methods: a simplified three-dimensional TMJ disc model was developed by using Rhinoceros 3D software, and exported to ANSYS software. A 4.9N load was applied on the inferior surface of the model at inclinations of 30, 40, and 50 degrees to the mandibular plane (GoMe). ANSYS was used to analyze stress distribution on the TMJ disc for the different angulations, by means of finite element method. Results: The results showed that the tensile and compressive stresses concentrations were higher on the inferior surface of the model. More presence of tensile stress was found in the middle-anterior region of the model and its location was not altered in the three directions of load application. There was more presence of compressive stress in the middle and mid-posterior regions, but when a 50o inclined load was applied, concentration in the middle region was prevalent. Tensile and compressive stresses intensities progressively diminished as the load was more vertically applied. Conclusions: stress induced by the chincup therapy is mainly located on the inferior surface of the model. Loads at greater angles to the mandibular plane produced distribution of stresses with lower intensity and a concentration of compressive stresses in the middle region. The simplified three-dimensional model proved useful for assessing the distribution of stresses on the TMJ disc induced by the chincup therapy.

RESUMO Objetivo: avaliar, por meio do método dos elementos finitos, a distribuição das tensões no disco articular produzidas pela mentoneira ortopédica. Métodos: um modelo tridimensional simplificado do disco articular foi desenvolvido com o software Rhinoceros 3D e exportado para o software ANSYS. Uma carga de 4,9 N (500 gf) foi aplicada na superfície inferior do modelo, com inclinação de 30, 40 e 50o em relação ao plano mandibular Gônio-Mentoniano (GoMe). O ANSYS analisou, por meio do método dos elementos finitos, a distribuição das tensões presentes no modelo do disco articular para as diferentes angulações. Resultados: os resultados mostraram que a concentração das tensões de tração e compressão foi maior na superfície inferior do modelo. A tensão de tração foi mais presente na região média-anterior do modelo, e sua localização não se alterou nas três direções da aplicação da carga. A tensão de compressão foi mais presente nas regiões média e média-posterior do modelo, mas quando a carga a 50o foi aplicada, ela se concentrou na região média. As intensidades das tensões de tração e compressão diminuíram progressivamente à medida que a carga foi aplicada mais verticalmente. Conclusão: as tensões induzidas pela mentoneira ortopédica se localizaram principalmente na superfície inferior do modelo. As cargas com maior angulação em relação ao plano mandibular produziram uma distribuição de tensões com menor intensidade e uma concentração da tensão de compressão na região média do modelo. Um modelo tridimensional simplificado se mostrou útil na avaliação da distribuição das tensões no disco articular induzidas pela mentoneira ortopédica.

Effects of porcelain thickness on the flexural strength and crack propagation in a bilayered zirconia system

Abstract Objective: This study evaluated the influence of porcelain (VM9, VITA Zahnfabrik, Germany) thickness on the flexural strength and crack propagation in bilayered zirconia systems (YZ, VITA Zahnfabrik, Germany). Material and Methods: Thirty zirconia bars (20.0x4.0x1.0 mm) and six zirconia blocks (12.0x7.5x1.2 mm) were prepared and veneered with porcelain with different thickness: 1 mm, 2 mm, or 3 mm. The bars of each experimental group (n=10) were subjected to four-point flexural strength testing. In each ceramic block, a Vickers indentation was created under a load of 10 kgf for 10 seconds, for the propagation of cracks. Results: The results of flexural strength were evaluated by One-way ANOVA and Tukey's test, with a significance level of 5%. The factor "thickness of the porcelain" was statistically significant (p=0.001) and the l-mm group presented the highest values of flexural strength. The cracks were predominant among the bending specimens with 1 and 2 mm of porcelain, and catastrophic failures were found in 50% of 3-mm-thick porcelain. After the indentation of blocks, the most severe defects were observed in blocks with 3-mm-thick porcelain. Conclusion: The smallest (1 mm) thickness of porcelain on the zirconia infrastructure presented higher values of flexural strength. Better resistance to defect propagation was observed near the porcelain/ zirconia interface for all groups. Higher flexural strength was found for a thinner porcelain layer in a bilayered zirconia system. The damage caused by a Vickers indentation near and far the interface with the zirconia shows that the stress profiles are different.

The first assessment of the stress inducible defense of Leucaena leucocephala with acaricidal potential effect against Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) / Primeira avaliação de extratos proteicos de Leucaena leucocephala induzidos por injúria mecânica com atividade carrapaticida sobre Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Abstract Plants respond to wounding caused by mechanical stress or herbivory by synthesizing defense proteins. There are no studies reporting the action of induced plant proteins against ticks. The aim of this study was to investigate the effect of mechanically wounded Leucaena leucocephala leaves against Rhipicephalus (Boophilus) microplus. Initially, we carried out time course experiments to evaluate the impact of mechanical wounding on the protein content and the peroxidase, catalase and protease inhibitor activities in L. leucocephala. We then evaluated the acaricidal activity on R. (B.) microplus from protein extract collected from L. leucocephala after mechanical wounding. L. leucocephala leaves were artificially wounded, and after 6, 12, 24 and 48h, the leaves were collected for protein extraction. Quantitative and qualitative analyses of the proteins were performed. The protein content and peroxidase and protease activities increased 12h after wounding, and the acaricidal activity of this protein extract was evaluated using engorged R. (B.) microplus females. The protein extract obtained after wounding reduced egg production (8.5%) compared to those without wounding. Furthermore, the extract reduced egg hatching by 47.7% and showed an overall efficacy of 56.3% at 0.1 mgP/mL of the protein. We demonstrated that L. leucocephala defensive proteins could be effective against R. (B.) microplus.

Resumo As plantas respondem a injúria causada por estresse mecânico ou por ataque de herbívoros através da síntese de proteínas de defesa. Não há estudos de proteínas induzidas de plantas contra carrapatos. O objetivo deste estudo foi verificar a atividade acaricida de extratos protéicos de folhas Leucaena leucocephala após injúria mecânica, sobre Rhipicephalus (Boophilus) microplus. Inicialmente foram conduzidos experimentos em diferentes intervalos de tempo para avaliar o impacto da injúria mecânica no conteúdo de proteína, atividade de peroxidase, catalase e inibidor de protease de L. leucocephala. Em seguida foi avaliada a atividade acaricida sobre R. (B.) microplus de um extrato protéico após injúria mecânica. Folhas de L. leucocephala foram artificialmente feridas e após 6, 12, 24 e 48h, as folhas foram coletadas para extração de proteínas. Análises quantitativas e qualitativas das proteínas foram realizadas. A quantidade de proteína e atividades de peroxidase e protease aumentaram 12h após a injúria. O extrato proteico obtido após injúria (12h) reduziu a produção de ovos (8,5%) em comparação com extratos de plantas sem injúria. O extrato reduziu 47,7% a eclosão de ovos e apresentou eficácia geral de 56,3% a 0,1 miligrama de proteína por mL (mgP/mL). Apresentamos que proteínas de defesa de L. leucocephala podem ter atividade sobre R. (B.) microplus.