Effects of PEEK Anisotropy Formed by 3D Printing on Mechanical Properties of Femoral Substitutes / 医用生物力学

Objective Aiming at the problem of significant anisotropy in the three-dimensional ( 3D) printed polyether-ether-ketone ( PEEK) bone substitutes manufactured by material extrusion technology, taking the femur, the main load-bearing long bone of the lower limb, as an example, the biomechanical properties of the femoral model under different direction in the build chamber were evaluated by the combination of finite element analysis and in-vitro mechanical experiment. Methods A left femoral model was obtained by reconstruction from CT data. The stress and displacement of the 3D printed PEEK femur with different directions in the build chamber under five physiological postures in the human gait cycle were simulated by varying the orthogonal anisotropy mechanical properties. An in-vitro mechanical experiment was conducted to investigate the safety and stability of the femur through a 3D printed PEEK femur. Results When the long axis of the femur model was perpendicular to the building platform of the 3D printer, a better mechanical property was obtained, and the maximum von Mises stress was 46. 56 MPa, which was lower than the yield stress of PEEK, while the maximum displacement was larger than that of the natural femur under same loading condition. Therefore, the 3D printed PEEK femur met the strength requirement, but the stability needs to be improved. Conclusions The long axis is recommended to be perpendicular to the building platform when the material extrusion technology was used for the substitute of the load-bearing long bone, and the effect of its anisotropy on service performance of the substitute should be carefully considered when the 3D printing technology is used for load-bearing bone substitute.

Spatial variability of precompression stress and volumetric water content of a red-yellow latosol (Oxisol) / Variabilidade espacial da pressão de preconsolidação e da umidade volumétrica de um latossolo vermelho amarelo

The intensive agricultural machinery traffic to which soils under coffee crops are exposed may cause significant changes in soil structure. The goals of this study were to: a) characterize the spatial variability of precompression stress (σp) and volumetric water content (θ) of a Red-Yellow Latosol (Oxisol) and determine their spatially dependent structures using ordinary kriging semivariograms; b) using this date to construct a load-bearing capacity (LBC) map for the site, identifying the depth with higher ; and c) use the map as a decision support tool regarding agricultural machinery logistic management in coffee plantations. The research was conducted on an experimental farm of the Agricultural Research Company of Minas Gerais (Epamig), Patrocinio, MG, on a clayey Oxisol. Samples were collected from 2.0 × 1.5 m sampling pits at intersections of a rectangular 40 × 150 m grid, totaling 28 sampling points. The soil samples were collected with metal rings (0.0254 m in height and 0.0630 m in diameter) using an Uhland sampler. Sampling at each pit was at 3 layers: 0.00­0.03 m, 0.10­0.13 m, and 0.25­0.28 m, and seven samples arranged in a matrix form were collected at each layer, totaling 588 samples. The σp and θ showed a spatially dependent structure. The depth of 0.00­0.03 m showed higher LBC, indicating that this depth was more compacted compared to other depths. Based on the σp maps, the tractor and the combine should not traffic into the areas at water content of 0.45 m3 m-3, because the soil has a LBC of 200 kPa. If this condition is not respected, additional compaction will occur. Tractor traffic is permissible when the water content reaches values less than 0.36 m3 m-3, whereas for combine traffic, the water content values must be less than 0.30 m3 m-3.

O tráfego intenso de máquinas agrícolas sobre solos cultivados com cafeeiro pode causar alterações significativas na estrutura do solo. Os objetivos deste estudo foram: a) avaliar e identificar a variabilidade espacial da pressão de preconsolidação (σp) e a umidade volumétrica (θ) de um Latossolo Vermelho-Amarelo (LVA) e determinar a estrutura de dependência espacial através de semivariogramas utilizando a krigagem ordinária; b) verificar no mapa, a profundidade com maior capacidade de suporte de carga (CSC) do solo ; c) dar suporte a tomada de decisão no manejo do maquinário agrícola da cultura cafeeira e utilizar esses mapas para a logística de manejo de trafego de máquinas. O experimento foi conduzido num LVA textura muito argilosa na Fazenda da Epamig (Empresa de Pesquisa Agropecuária de Minas Gerais), em Patrocínio-MG. A amostragem foi realizada numa malha retangular (150 m x 40 m), onde foram coletadas amostras indeformadas em anéis metálicos de 0,0254 m de altura por 0,0630 m de diâmetro com auxílio do amostrador tipo Uhland em 28 trincheiras. Cada trincheira possui três degraus que correspondem às profundidades de (0.00-0.03; 0.10-0.13 e 0.25-0.28 m) e as dimensões dos degraus foram de 2,0 x 1,5 m, coletaram-se sete amostras (disposta em forma matricial) para cada degrau, totalizando 588 amostras. A σp e θ apresentaram estrutura de dependência espacial. A profundidade de 0.00-0.03m apresentou maior CSC indicando que esta profundidade está mais compactada em relação as demais profundidades. Com base nos mapas da σp, o trator e a colhedora não devem trafegar na área para umidade volumétrica igual a 0.45 m3 m-3, pois o solo possui CSC de 200 kPa. Se essa condição for desrespeitada, a compactação adicional poderá ocorrer. Para o tráfego do trator, deve-se esperar por um período, para que a θ atinja um valor menor que 0.36 m3 m-3, enquanto que para o tráfego da colhedora deve-se esperar a θ atingir valor menor que 0.30 m3 m-3.

Effect of the restorative technique on load-bearing capacity, cusp deflection, and stress distribution of endodontically-treated premolars with MOD restoration

OBJECTIVES: To evaluate the influence of the restorative technique on the mechanical response of endodontically-treated upper premolars with mesio-occluso-distal (MOD) cavity. MATERIALS AND METHODS: Forty-eight premolars received MOD preparation (4 groups, n = 12) with different restorative techniques: glass ionomer cement + composite resin (the GIC group), a metallic post + composite resin (the MP group), a fiberglass post + composite resin (the FGP group), or no endodontic treatment + restoration with composite resin (the CR group). Cusp strain and load-bearing capacity were evaluated. One-way analysis of variance and the Tukey test were used with α = 5%. Finite element analysis (FEA) was used to calculate displacement and tensile stress for the teeth and restorations. RESULTS: MP showed the highest cusp (p = 0.027) deflection (24.28 ± 5.09 µm/µm), followed by FGP (20.61 ± 5.05 µm/µm), CR (17.72 ± 6.32 µm/µm), and GIC (17.62 ± 7.00 µm/µm). For load-bearing, CR (38.89 ± 3.24 N) showed the highest, followed by GIC (37.51 ± 6.69 N), FGP (29.80 ± 10.03 N), and MP (18.41 ± 4.15 N) (p = 0.001) value. FEA showed similar behavior in the restorations in all groups, while MP showed the highest stress concentration in the tooth and post. CONCLUSIONS: There is no mechanical advantage in using intraradicular posts for endodontically-treated premolars requiring MOD restoration. Filling the pulp chamber with GIC and restoring the tooth with only CR showed the most promising results for cusp deflection, failure load, and stress distribution.

Soil compaction caused by harvest and logging operations in eucalyptus forests in coarse-textured soils from northeastern Brazil / Compactação do solo causada por operações de colheita e baldeio em florestas de eucalipto em solos de textura grosseira do nordeste do Brasil

ABSTRACT Planted forests occupy more than 6.5 million ha in Brazil, where harvest and logging operations are performed with increasingly heavier machinery, increasing the risk of soil compaction. Soil compaction can be avoided if soil load bearing capacity is not exceeded, what makes it important to assess both the soil strength and the impact of different operations. The aim of this study was to evaluate the load bearing capacity of some coarse textured soils (two Hapludult and one Haplorthod) in two soil horizons (BA and B), from northeastern Brazil; and to assess the impact of harvest and logging operations performed with harvester and forwarder. Although the Haplorthod presented higher load bearing capacity in both the BA horizon (for the whole moisture range) and the B horizon (for higher water contents), it suffered the greatest soil compaction. Traffic with the harvester resulted in soil compaction in both the BA and the B horizons, but the increase in bulk density was higher on the later, reaching 18.7% in the Haplorthod. The forwarder traffic intensity and the presence of plant residue cover significantly affected the occurrence of soil compaction. In the BA horizon, the increase in soil bulk density for different forwarder traffic intensities was 3 passes ~ 6 passes < 12 passes ~ 16 passes. The increase in bulk density was higher in the Haplorthod, reaching 32% after 16 forwarder passes over bare soil. Significant linear regressions were obtained from the number of forwarder passes and the increase in bulk density.

RESUMO As florestas plantadas ocupam mais de 6,5 milhões de ha no Brasil, nas quais as operações de colheita e baldeio são realizadas com maquinário cada vez mais robusto, o que aumenta o risco de compactação do solo. A compactação do solo pode ser evitada se a sua capacidade de suporte de carga não for excedida, o que torna importante a avaliação tanto da resistência mecânica do solo quanto o impacto de diferentes operações. O objetivo deste estudo foi avaliar a capacidade de suporte de carga de solos de textura grosseira (dois Hapludult e um Haplorthod) em dois horizontes (BA e B) do Nordeste do Brasil; além de avaliar o impacto das operações de colheita e baldeio de madeira realizadas com harvester e forwarder. Apesar de o Haplorthod ter apresentado a maior capacidade de suporte de carga no horizonte BA (para toda a faixa de umidade) e no horizonte B (para maiores umidades) ele foi a classe de solo que apresentou maior compactação. O tráfego com o harvester resultou em compactação tanto no horizonte BA quanto no B, mas o aumento da densidade do solo foi maior no último, chegando a 18,7% no Haplorthod. A intensidade de tráfego do forwarder e a presença de resíduos de plantas na superfície do solo afetaram significativamente a ocorrência de compactação do solo. No horizonte BA, o aumento da densidade do solo em decorrência da intensidade de tráfego do forwarder foi de 3 passadas ~ 6 passadas < 12 passadas ~ 16 passadas. O aumento de densidade do solo foi maior no Haplorthod, atingindo 32% após 16 passadas sobre o solo descoberto. Regressões lineares significativas foram obtidas a partir do número de passadas do forwarder e o aumento na densidade do solo.

Soil susceptibility to compaction under use conditions in southern Brazil / Susceptibilidade do solo à compactação sob condições de uso no sul do Brasil

ABSTRACT The degree of soil compaction is intensified by its inadequate management, compaction being variable depending on soil type since even under identical management conditions, different types have different abilities to withstand load. The objective of this study was to evaluate the susceptibility to compaction of different classes of soils under no-tillage (NT) croping system compared to the original condition. Thus, i) soils with the same source material have distinct resistance to compression with increased NT adoption time; ii) the most sensitive indicators of this change are the ratios mass:volume and volume:volume and; iii) there is a relationship between resistance and compaction susceptibility with the amount and type of oxide. Soil samples were collected in areas under NT and under natural condition in order to assess the impact imposed by the NT on the attributes density and porosity, precompression stress and compressibility index and relate them to the oxide type of, and content in, the soils under study. The results show that the density and macroporosity were those most affected by the NT agricultural use, regardless of soil type, that is, its dynamic is related more to soil use and less to mineralogical characteristics. The soil resistance and compaction susceptibility were higher in soil developed in basalt, followed by those developed in sandstone and granite. Both the organic matter content and type and concentration of iron oxides were related to the soil resistance and susceptibility to compaction.

RESUMO O grau de compactação do solo é intensificado pelo seu inadequado manejo, sendo a compactação depente do tipo de solo, uma vez que mesmo sob condições idênticas de uso, diferentes solos têm diferentes habilidades para suportar a carga. O objetivo deste estudo foi avaliar a susceptibilidade à compactação de diferentes classes de solos sob sistema plantio direto (PD) em relação ao estado original. Assim, i) solos com o mesmo material de origem apresentam distinta resistência à compressão com o aumento do tempo adopção do PD; ii) os indicadores mais sensíveis desta mudança são os da relação massa: volume e volume: volume e; iii) existe uma relação entre resistência e suscetibilidade à compactação com a quantidade e o tipo de óxido. As amostras de solo foram coletadas em áreas sob PD e sob condição natural (CN), a fim de avaliar o impacto imposta pelo PD sobre os atributos densidade e porosidade, tensão de pré-compressão e índice de compressibilidade e relacioná-los com o tipo de óxido e conteúdo. Os resultados mostram que a densidade e a macroporosidade foram os mais afetados pelo uso agrícola em PD, independentemente do tipo de solo, ou seja, a sua dinâmica está mais relacionada com o uso do solo e menos com as características mineralógicas. A resistência do solo e suscetibilidade à compactação foram maiores no solo desenvolvido em basalto, seguido por aqueles desenvolvidos em arenito e granito. Tanto o teor de matéria orgânica e tipo e concentração de óxidos de ferro foram relacionados com a resistência do solo e susceptibilidade à compactação.

Fracture resistance of zirconia and resin nano ceramic implant abutments according to thickness after thermocycling / 대한치과보철학회지

PURPOSE: The aim of this in vitro study is to investigate load bearing capacity of esthetic abutments according to the type of material and wall thickness. MATERIALS AND METHODS: 70 specimens equally divided into seven groups according to their abutment wall thicknesses. The abutments prepared with titanium 0.5 mm wall thickness were used as a control group (Ti-0.5), whereas zirconia abutments and resin nano ceramic abutments with wall thickness 0.5 mm, 0.8 mm and 1.0 mm were prepared as test groups (Zir-0.5, Zir-0.8, Zir-1.0 and RNC-0.5, RNC-0.8, RNC-1.0). All specimens were tested in a universal testing machine to evaluate their resistance to fracture and all of them underwent thermo-cycling before loading test. Mean fracture values of the groups were measured and statistical analyses were made using two-way ANOVA. RESULTS: Zir-1.0 showed the highest mean strength (2,476.3 ± 342.0 N) and Zir-0.8 (1,518 ± 347.9 N), Ti-0.5 (1,041.8 ± 237.2 N), Zir-0.5 (631.4 ± 149.0 N) were followed. The strengths of RNC groups were significantly lower compared to other two materials (RNC-1.0 427.5 ± 72.1, RNC-0.8 297.9 ± 41.2) and the strengths of all the test groups decreased as the thickness decreases (P < .01). RNC-0.5 (127.4 ± 35.3 N) abutments were weaker than all other groups (P < .05). CONCLUSION: All tested zirconia abutments have the potential to withstand the physiologic occlusal forces in anterior and posterior regions. In resin nano ceramic abutments, wall thickness more than 0.8 mm showed the possibility of withstanding the occlusal forces in anterior region.

Weight of school material and back pain in students leaving their books at school / Peso do material escolar e dor nas costas em alunos que deixam seus livros na escola

ABSTRACT BACKGROUND AND OBJECTIVES: The prevalence of back pain in children and adolescents has been reason for school health concern. Among different causes, school material weight is highlighted since studies have shown that it exceeds recommended values. So, strategies to decrease material weight have been adopted, such as the availability of cabinets or shelves to leave the books at school. However, it is not well explained whether such strategies would solve the problem. This study aimed at observing the association between school material weight and back pain in students who leave their material at school. METHODS: Sample was made up of 48 students of the 5th year of Basic Education of a municipal school of Petrolina-PE. Students and their materials were weighed. The back pain and body posture evaluation instrument was used to evaluate back pain. RESULTS: Mean school material weight was 10.8±3.9% of body weight, without difference between genders. From 48 students, 20 have reported back pain and there has been no association between back pain and gender or school material weight. CONCLUSION: Among students, 41.67% have reported back pain, while 52.09% carried weight above 10% of body weight, but there has been no association between school material weight and back pain.

RESUMO JUSTIFICATIVA E OBJETIVOS: A prevalência de dor nas costas em crianças e adolescentes tem sido motivo de preocupações no âmbito da saúde escolar. Entre as diferentes causas, o peso do material escolar destaca-se, uma vez que pesquisas mostram que este excede os valores recomendados. Assim, estratégias para reduzir o peso do material têm sido adotadas, como a disponibilidade de armários ou de estantes para deixar os livros na escola. Contudo, não está bem esclarecido se essas estratégias solucionam o problema. O objetivo deste estudo foi verificar a associação entre o peso do material escolar e a presença de dor nas costas em alunos de uma escola, os quais deixam seus livros na escola. MÉTODOS: A amostra foi composta por 48 alunos do 5º ano do Ensino Fundamental de uma escola municipal de Petrolina-PE. Os alunos e seus materiais foram pesados. Para avaliar a presença de dor nas costas, foi utilizado o questionário de Avaliação da Postura Corporal e Dor nas Costas. RESULTADOS: O peso médio do material escolar foi 10,8±3,9% do peso corporal, não sendo encontrada diferença entre os gêneros. Dos 48 alunos, 20 relataram sentir dor nas costas e não foi encontrada associação da presença de dor nas costas com o gênero e com o peso do material escolar. CONCLUSÃO: Entre os alunos, 41,67% relataram sentir dor nas costas, enquanto que 52,09% transportam um peso superior a 10% do peso corporal, mas não foi encontrada associação entre o peso do material escolar e a presença de dor nas costas.

Effects of adhesives aging in water on load-bearing capacity of monolithic CAD/CAM lithium disilicate crowns / 医用生物力学

Objective To analyze the contact failure of monolithic lithium disilicate CAD/CAM crowns by experiment and numerical simulation, and explore the influences of adhesives aging in water on load-bearing capacity of the crowns. Methods The specimens of sectioned monolithic lithium disilicate crowns were designed and manufactured, and evenly divided into two groups and stored in the air and in the distilled water for 30 days, respectively. The specimens were then subjected to monotonic contact loads to compare and analyze their load-bearing capacity. The fractured surfaces and adhesive interfaces of the specimens were observed by scanning electronic microscope. Meanwhile, the stress distribution on the crowns was calculated by numerical simulation to analyze the adhesives aging influence on load-bearing capacity of the crowns. Results The fracture loads on crowns stored in the air and in the water were (561.51 ± 65.66) N and (398.09 ± 90.20) N, respectively, indicating a significant difference. The tensile stress increased considerably at lower surface of the ceramic crown due to the reduction of adhesive strength at the interface of ceramic crown and substrate, which could increase the propensity of contact failure. Conclusions The adhesives aging in water reduces the bonding strength, and accordingly changes the tensile stress distributions, which can lower the load bearing capacity of the lithium disilicate crowns. The research finding provides references for the design and manufacturing of all-ceramic CAD/CAM restored crowns in clinic.

Mechanical property analysis of PVA/HA composite hydrogel and its finite element simulation / 医用生物力学

Objective To study the effect from the content change in hydroxyapatite (HA) on mechanical properties of polyvinyl alcohol/hydroxyapatite(PVA/HA)composite hydrogel and its load bearing characteristics based on experiment and finite element simulation. Methods The compression and stress relaxation tests of PVA/HA composite hydrogel were performed on the UMT test machine. Through the simulation and experimental results, the load-bearing characteristics of PVA/HA composite hydrogel and the effect of HA on PVA/HA composite hydrogel performance were investigated. Results With HA content increasing, the compression modulus of PVA/HA composite hydrogel was first increased and then decreased, while its permeability coefficient was first decreased and then increased. When the HA content was 3%，the compression modulus of PVA/HA composite hy drogel reached maximum (1.25 MPa)and its permeability coefficient reached minimum(1.59×10-3 mm4•N-1•s-1). The fluid bearing proportion of PVA/HA composite hydrogel was first increased and then decreased with the loading time increasing, which presented a nonlinear change. The proportion of the fluid bearing was significantly increased after HA added into PVA / HA composite hydrogel. The stress relaxation rate was first increased and then decreased with HA content increasing. Under the same loaded displacement, PVA / HA composite hydrogel with 3% HA content could disperse more contact stress. Conclusions The internal bearing characteristics of PVA / HA composite hydrogel have a great impact on its mechanical properties. When the HA content is 3%, the PVA / HA composite hydrogel has the best mechanical properties, which are closer to those of the natural articular cartilage.

COMPARISON OF THE GAIT OF WOMEN WITH A LOAD ON THEIR BELLY AND THAT OF PREGNANT WOMEN / 体力科学

Gait analysis was conducted on 7 healthy pregnant women (pregnant group) and 6 non-pregnant women (pseudo-pregnant group) using a 3-D motion analysis system (VICON 460) and two forceplates (Kistlar 9286A). The data was collected at 8-9 months of gestation (pregnant condition) and 4-8 months postpartum (non-pregnant condition) in the pregnant group. In the pseudo-pregnant group, the participants walked with a 5kg-load on their belly (pregnant condition) and without any load (non-pregnant condition). Comparisons using two-way ANOVAs with repeated measures were conducted. Interaction of group × condition was not observed in the measured gait parameters except the angle of the maximum hip adduction. Main effect in the condition and the group was found in some parameters. In the pregnant condition, gait velocity was slower (pregnant group 68.7±8.6 m/min pseudo-pregnant group 63.8±4.8 m/min) than in the non-pregnant condition (pregnant group 75.5±3.2 m/min pseudo-pregnant group 69.8±8.7 m/min). The second vertical peak ground reaction force was smaller in the pregnant condition (pregnant group 105.4±4.8 % pseudo-pregnant group 108.4±6.3 % of body-weight) than in the non-pregnant condition (pregnant group 114.3±7.4 % pseudo-pregnant group 113.5±4.2 % of body-weight). These results demonstrated that pregnant condition changed kinetic and kinematic characteristics of the gait.

Comparative study between two elbow flexion exercises using the estimated resultant muscle force / Estudo comparativo entre dois exercícios de flexão do cotovelo utilizando a estimativa da força muscular resultante

OBJECTIVE: The present study sought to compare the estimated resultant muscle force required throughout the range of motion in two variations of elbow flexion exercise: the Scott exercise, performed with the aid of a Scott bench, and the unsupported exercise, performed with the upper arm simply resting on the leg. METHOD: Eight healthy individuals performed each exercise eight times, with the same 4kg load. The biceps brachii and triceps brachii muscles were monitored using surface electromyography and the elbow joint movement was measured using an electrogoniometer. A mechanical model of the situation was proposed to evaluate the resultant muscle force acting throughout the range of motion of the exercise. RESULTS: Comparisons between the two exercise variations presented significant differences (p<0.01) in practically all of the angles. CONCLUSION: Analysis of the model suggests that greater muscle demand is not necessarily associated with higher resistance torque values in the exercise as it is fundamental to take into consideration the moment arm of the muscles involved.

OBJETIVO: O presente estudo objetivou comparar a força muscular resultante estimada necessária durante toda a amplitude do exercício de flexão de cotovelo, executado em duas variações: exercício Scott, realizado com auxílio do banco Scott, e exercício sem suporte, realizado com o braço apenas apoiado na perna. MÉTODO: Oito indivíduos saudáveis realizaram oito execuções de cada exercício, com uma carga fixa de 4kg. Os músculos bíceps braquial e tríceps braquial foram monitorados com eletromiografia de superfície e o movimento da articulação do cotovelo acompanhado com eletrogoniometria. Um modelo mecânico da situação foi proposto para avaliar a força muscular resultante atuante durante toda a amplitude do exercício. RESULTADOS: Comparações entre os exercícios apresentaram diferenças significativas em praticamente todas as angulações (p<0,01). CONCLUSÃO: A análise do modelo sugere que a maior exigência muscular não necessariamente está associada aos maiores valores do torque de resistência do exercício, sendo fundamental levar em consideração a distância perpendicular da musculatura envolvida.

Efeitos de sessões educativas no uso das mochilas escolares em estudantes do ensino fundamental I / Effects of educational sessions on school backpack use among elementary school students

OBJETIVO: Avaliar a modificação na quantidade de carga transportada, o modelo e o modo de transportar mochilas escolares após sessões educativas. MÉTODOS: Estudo de uma série de casos, com 99 crianças de sete a 11 anos do ensino fundamental, em escola particular da cidade São Paulo, São Paulo. Foram avaliadas a massa corporal (kg) e estatura dos alunos (cm), quantidade de carga transportada nas mochilas (kg). Os modelos e os modos de transporte das mochilas foram avaliados por filmagem pré e pós-intervenção. Como medida de intervenção, os sujeitos (crianças, pais e professores) foram submetidos a uma sessão educativa, que consistiu de orientações teóricas sobre coluna vertebral e transporte de carga. Para os escolares foi adicionada orientação prática das posturas corretas no transporte de carga. Os escolares receberam um reforço prático mensal por três meses. Pais e professores receberam reforço em folheto informativo e orientações na homepage da escola. Os dados foram analisados pelos testes estatísticos de igualdade de duas proporções e Wilcoxon. O nível de significância adotado foi 5 por cento. RESULTADOS: O modelo de mochila modificou para duas alças de 46,5 por cento para 60,6 por cento (p=0,046), modo de transporte para ombro bilateral de 41,4 por cento para 55,6 por cento (p=0,047). A carga transportada nas mochilas diminuiu 2,66kg (p<0,001) e a relação massa corporal do sujeito e carga transportada nas mochilas diminuiu 7 por cento. Na modificação por categorias, o número de alunos do grupo inadequado (carga transportada>15 por cento da massa corporal do aluno) diminuiu (p<0,001). CONCLUSÕES: As sessões educativas promoveram mudanças na utilização de mochilas, revelando adesão satisfatória ao modelo de intervenção proposto entre os escolares e o importante papel da Fisioterapia na saúde escolar.

OBJECTIVE: To evaluate the changes in loads carried, in the model of backpack used and in the way of carrying school backpacks after the implementation of an educational program. METHODS: This study was performed on 99 children aged seven to 11 years at elementary school level in a private school in São Paulo, São Paulo, Brazil. The subjects' body mass (kg) and height (cm) and the loads carried in their backpacks (kg) were evaluated. The backpack models and the ways of carrying them were evaluated by filming before and after the intervention. The intervention program consisted of educational sessions offered to the children, parents and teachers. The sessions involved lectures about the spine and about the principles of load carrying. The children also received practical guidance relating to correct postures for load carrying. The children received monthly practical reinforcement for three months. The parents and teachers received reinforcement by means of information flyers and guidance on the school's home page. The data were analyzed by means of two-proportion equality and Wilcoxon statistical tests. The significance level was considered as α=0.05. RESULTS: The use of a two-strap backpack model increased from 46.5 percent to 60.6 percent (p=0.046) and carrying it on two shoulders increased from 41.4 percent to 55.6 percent (p=0.047). The load carried in the backpacks decreased by 2.66kg (p<0.001) and the ratio between the subject's body mass and the load carried in the backpacks decreased by 7 percent. With regard to change per category, the number of subjects in the inappropriate group (load carried>15 percent of the subject's body mass) decreased (p<0.001). CONCLUSIONS: The educational sessions promoted changes in backpack use and it was observed a satisfactory adherence to the intervention program proposed. These results demonstrate the importance of Physical Therapy educational programs in schoolchildren's health.

Biomechanical Adjustments in Lumbar Spine Associated with Sudden Upper Limb Loading

OBJECTIVE: To investigate the response of back muscle, the flexion moment and the kinematic change of lumbar spine during sudden upper limb loading between expected and unexpected conditions. METHOD: 23 healthy young subjects (13 male and 10 female, mean age 26.6+/-3.3) were recruited. We measured the latency of paraspinal muscle contraction (erector spinae and lumbar multifidus), flexion moment of lumbar spine, and kinematic change of lumbar spine during sudden upper limb loading by using surface EMG system, motion analysis system, and force platform. 6 trials with 3 eye opened and 3 eye closed were performed randomly. RESULTS: The latency of paraspinal muscle contractions was significantly slower during eyes closed condition than during eyes opened condition after sudden upper limb loading (p<0.05). The flexion moment and the flexion change of lumbar spine increased significantly during eyes closed condition compared with eyes opened condition (p<0.05). CONCLUSION: The response of paraspinal muscle was significantly slower and the flexion moment and the flexion change of lumbar spine was higher during unexpected condition than during expected condition after sudden upper limb loading. Therefore, the spinal stability is more decreased during unexpected condition than expected condition.

An evaluation of the primary implant stability and the immediate load-bearing capacity according to the change of cortical bone thickness / 대한치과보철학회지

STATEMENT OF PROBLEM: Cortical bone plays an important role in the primary implant stability, which is essential to immediate/early loading. However, immediate load-bearing capacity and primary implant stability according to the change of the cortical bone thickness have not been reported. PURPOSE: The objectives of this study were (1) to measure the immediate load-bearing capacity of implant and primary implant stability according to the change of cortical bone thickness, and (2) to evaluate the correlation between them. MATERIAL AND METHODS: 48, screw-shaped implants (3.75 mmx7 mm) were placed into bovine rib bone blocks with different upper cortical bone thickness (0-2.5 mm) and resonance frequency (RF) values were measured subsequently. After fastening of healing abutment, implants were subjected to a compressive load until tolerated micromotion threshold known for the osseointegration and load values at threshold were recorded. Thereafter, RF measurement after loading, CT taking and image analysis were performed serially to evaluate the cortical bone quality and quantity. Immediate load-bearing capacity and RF values were analyzed statistically with ANOVA and post-hoc method at 95% confidence level (P<0.05). Regression analysis and correlation test were also performed. RESULTS: Existence and increase of cortical bone thickness increased the immediate load-bearing capacity and RF value (P<0.05). With the result of regression analysis, all parameters of cortical bone thickness to immediate load-bearing capacity and resonance frequency showed significant positive values (P<0.0001). A significant high correlation was observed between the cortical bone thickness and immediate load-bearing capacity (r=0.706, P<0.0001), between the cortical bone thickness and resonance frequency (r=0.753, P<0.0001) and between the immediate loadbearing capacity and resonance frequency (r=0.755, P<0.0001). Conclusion. In summary, cortical bone thickness change affected the immediate load-baring capacity and the RF value. Although RF analysis (RFA) is based on the measurement of implant/bone interfacial stiffness, when the implant is inserted stably, RFA is also considered to reflect implant/bone interfacial strength of immediately after placement from high correlation with the immediate loadbaring capacity. RFA and measuring the cortical bone thickness with X-ray before and during surgery could be an effective diagnosis tool for the success of immediate loading of implant.