Alternative method of photopolymerization of composite resin specimen for flexural strength test / Método alternativo de fotopolimerização de resinas compostas para teste de flexão

The flexural resistence is one of the most used test in researchs of mechanical characterization of resin composites for dental restoration. ISO 4049 photopolymerization technique performed static application stages of light tip. To polymerize the entire area of the specimen some areas must receive extra radiation. These areas with extra radiation are called overlap areas. In an attempt to remedy this problem, this research compared the ISO method with a new method using constant movement (CM) during photopolymerization. Twenty specimens (SPs) were produced with 25 x 2 x 2 mm, for each group, 10 specimens being polymerized by the static technique recommended by the ISO-4049 and 10 specimens polymerized by the CM technique for each LED curing light used. After Tukey's statistical analysis, it was found that there was no statistical difference in relation to flexural strength (FS) and for the flexural modulus of elasticity (EF). However, the standard deviation of both FS and EF were much lower in MC than in ISO. Therefore, the photopolymerization by CM of the samples for the flexural strength test proved to be a possible solution to the problem of overlap of the technique proposed by ISO.

O teste de flexão é um dos mais utilizados em pesquisa de caracterização mecânica de compósitos resinosos para restauração dentária. A técnica ISO 4049 é feita em etapas com aplicação estática da luz. Para que toda a área do corpo de prova receba esta radiação é preciso que outras áreas recebam radiação extra. Na tentativa de sanar tal problema, esta pesquisa comparou o método da ISO com um método que utiliza um movimento constante (MC) durante a fotopolimerização. Foram produzidos 20 corpos de provas (CPs) com 25 x 2 x 2 mm, para cada grupo, sendo 10 polimerizados pela técnica estática recomendada pela normativa ISO-4049 e 10 polimerizados pela técnica de movimentação contínua (MC) para cada fotopolimerizador LED utilizado. Após análise estatística de Tukey apurou-se que não houve diferença estatística em relação à resistência à flexão (RF) e para o módulo de elasticidade em flexão. Porém, percebe-se, que o desvio padrão tanto da RF quanto do EF foram bem menores em MC do que em ISO. Sendo assim, a fotopolimerização em movimentação constante (MC) das amostras para o teste de resistência à flexão se mostrou como uma possível solução para o problema de sobreposição na técnica proposta pela ISO.

3D printing process of gelatin/oxidized nanocellulose skin scaffold with high elastic modulus and high porosity / 中国组织工程研究

BACKGROUND:In the treatment of skin trauma with active repair,tissue engineering techniques are needed to generate new tissue to replace necrotic tissue.Skin scaffolds have a good application prospect in the field of wound repair.Skin scaffolds need to present three-dimensional porous structures with certain mechanical strength to meet the needs of cell proliferation and division.However,the mechanical strength of the currently used gelatin-based biomaterials is weak and cannot meet the requirements of the use of skin scaffolds. OBJECTIVE:To study the 3D printing process used in the preparation of tissue engineering skin scaffolds by gelatin/oxidized nanocellulose composites,and focus on the relationship between the porosity and mechanical strength of the scaffolds prepared under different process parameters. METHODS:Oxidized nanocellulose whiskers at 10%concentration were extracted from Humulus scandens and then compounded with 5%gelatin to obtain gelatin/oxidized nanocellulose composites.The elastic modulus of gelatin and gelatin/oxidized nanocellulose composite was determined.Skin scaffolds were prepared by 3D printing extrusion molding using gelatin/oxidized nanocellulose composite as the base material.Mechanical and rheological properties of the composite were tested to determine extrusion molding parameters(filling gap 1.5-2.5 mm,uniform distribution of 0.1 mm;air pressure of 160-200 kPa),and the skin scaffold with a three-dimensional porous structure was prepared.The compressive performance of the skin scaffold was tested and compared with the finite element analysis results.The relationship between the filling gap and the porosity and mechanical strength of the scaffold was demonstrated. RESULTS AND CONCLUSION:(1)The elastic modulus of 5%gelatin was increased by 8.84 times by adding 10%oxidized nanocellulose whisker.A gel filament with a diameter of 1 mm was obtained by extrusion at the air pressure of 160 kPa.When the filling gap increased from 1.5 mm to 2.5 mm,the theoretical porosity of the scaffold increased from 33%to 60%,but the compressive strength decreased from 230 000 Pa to 95 000 Pa.(2)These findings showed that the skin scaffold with theoretical porosity of 50%and elastic modulus of 160 000 Pa was prepared by using 2 mm filling gap.The scaffold had a clear three-dimensional porous structure.

Evaluation of the relationship between neck and shoulder pain and scalene muscles based on shear wave elastography / 中国组织工程研究

BACKGROUND:In clinical work,the stiffness of neck soft tissue in patients with neck and shoulder pain is mainly detected through palpation,which is highly subjective and lacks an objective basis.Real-time shear wave elastography is a quantitative elastic ultrasound technique that can objectively assess muscle elasticity and muscle status. OBJECTIVE:To apply real-time shear wave elastography to assess the stiffness of scalene muscles in patients with neck and shoulder pain and to observe the characteristics of muscle stiffness changes in the bilateral anterior,middle and posterior scalene muscles in patients with neck and shoulder pain. METHODS:From December 2021 to June 2022,36 healthy subjects(control group)and 36 patients with neck and shoulder pain(test group)were recruited at the Shenzhen Hospital of Guangzhou University of Chinese Medicine.Real-time shear wave elastography was applied to measure the mean values of elastic modulus and cross-sectional area of the anterior and middle and posterior scalene muscles bilaterally in the neutral and lateral flexion positions of the neck in both groups. RESULTS AND CONCLUSION:In the same position,there were no significant differences between the mean Values of elastic modulus of the left and right anterior scalene muscles as well as between the mean Values of elastic modulus of the left and right middle scalene muscles in each group(P>0.05);there were no significant differences between the cross-sectional area of the left and right anterior scalene muscles as well as the cross-sectional area of the left and right posteromedial scalene muscles in each group(P>0.05);and the elastic modulus and cross-sectional area of the posteromedial scalene muscles were significantly higher than those of the anterior scalene muscles in both groups(P<0.01,P<0.001).The mean Values of elastic modulus of the anterior and posteromedial scalene muscles were higher in the test group than in the control group in the neutral and lateral neck flexion positions(P<0.001),while the cross-sectional areas of the anterior and posteromedial scalene muscles were lower than those in the control group(P<0.01,P<0.001).To conclude,real-time shear wave elastography can be used to visually evaluate the differences in the mean Values of elastic modulus of the anterior and posteromedial scalene muscles in different states of the neck muscles in patients with neck and shoulder pain,whose bilateral scalene muscles are in a state of strain and stiffness.

Effect of bone cement with different elastic moduli injected into intervertebral space on stress of adjacent upper and lower vertebrae / 中国组织工程研究

BACKGROUND:In recent years,the treatment method of injecting bone cement into the intervertebral space has been introduced from abroad for the treatment of lumbar recurrent pain caused by lumbar disc degeneration and intervertebral space narrowing;however,some patients had vertebral fractures after treatment;the fracture may occur because the bone cement injected into the intervertebral space has a poor elastic modulus. OBJECTIVE:To analyze the effect of bone cement with different elastic moduli injected into the intervertebral space on the maximum stress of upper and lower vertebrae using a three-dimensional finite element model. METHODS:A volunteer with normal spine was recruited to obtain CT data.The finite element model of L2-L5 lumbar spine was established using Mimics,Geomagic,SolidWorks,and Ansys.Subsequently,a L3-L4 intervertebral space injection model with different doses(1 mL and 4 mL)of bone cement was established.Four different elastic moduli(1 000,2 000,4 000,and 8 000 MPa)were assigned to bone cement at each dose.Pressure and bending moment were applied on the surface of the L2 vertebral body to analyze the stress on the lower surface of the L3 vertebral body and the upper surface of the L4 vertebral body. RESULTS AND CONCLUSION:(1)In the case of the same amount of bone cement injection,as the elastic modulus of bone cement increased,the stress on the lower surface of L3 vertebral body and the upper surface of L4 vertebral body increased.Among them,the bone cement with an elastic modulus of 1 000 MPa had the least effect on the lower surface of L3 vertebral body and the upper surface of L4 vertebral body.Bone cement with elastic modulus of 8 000 MPa had the greatest effect on the lower surface of L3 vertebral body and the upper surface of L4 vertebral body.Bone cement with different elastic moduli had little effect on the motion range of the whole lumbar spine.(2)The results indicate that injecting bone cement with lower elastic modulus while meeting treatment requirements can reduce the risk of postoperative fractures.

Research progress on the mechanical compatibility of restorative materials with dental tissue / 口腔疾病防治

@#As the main means of mastication, teeth can withstand countless functional contacts. The mechanical properties of teeth are closely related to their tissue structure. Enamel and dentin have a high hardness and modulus of elasticity, and their graded structure allows them to withstand bite forces without being susceptible to fracture. When tooth tissue is defective, full crown restoration is often needed to restore the normal shape and function of the tooth. Metal materials, ceramic materials, and polyetheretherketone (PEEK) materials are commonly used for crown restoration. Metal materials have certain disadvantages in terms of aesthetics and are relatively rarely used in clinical practice. Ceramic materials with different compositions exhibit differences in performance and aesthetics, but their elastic modulus and hardness are much higher than those of dental tissue, resulting in mismatching mechanical properties. In contrast, the elastic modulus of PEEK is lower than that of tooth tissue and similar to that of bone tissue, but its properties can be improved by fiber reinforcement. Notably, when the mechanical properties of a restoration material and tooth tissue are not fully matched, the interface between them often forms a potential weak link, which ultimately affects the stability and long-term effect of the restoration. This article introduces the mechanical properties and corresponding structural characteristics of enamel and dentin. On this basis, the advantages and limitations of existing restoration materials are analyzed, and the possibility of biomimetic design of full crowns is further explored.

Value of endoscopic ultrasound elastography versus contrast-enhanced computed tomography in the diagnosis of gastrointestinal stromal tumors / 中国基层医药

Objective:To investigate the clinical value of endoscopic ultrasound elastography versus contrast-enhanced computed tomography in the risk stratification of gastrointestinal stromal tumors (GISTs). Methods:Clinical and imaging data were obtained from 77 patients who were confirmed to have GISTs and underwent endoscopic or surgical treatment at Wenzhou Central Hospital between May 2019 and April 2021. Endoscopic ultrasound elastography based on a five-point scoring system and hypotonic gastrointestinal contrast-enhanced computed tomography were performed for preoperative risk stratification of GISTs. The two techniques were compared in terms of the accuracy of preoperative risk stratification of GISTs. The imaging features of the two techniques were summarized.Results:According to the postoperative pathological results, 13 patients were at high risk, 13 patients were at medium risk, 35 patients were at low risk, and 16 patients were at extremely low risk. These patients were divided into two groups according to postoperative pathological results: a low-risk group (low risk + extremely low risk) and a medium- and high-risk group (high + medium risk). In the low-risk group ( n = 51), 42 patients were identified by endoscopic ultrasound elastography to have low-risk GISTs and were recommended to receive endoscopic treatment, while the rest 9 patients were identified to have medium-risk GISTs. Contrast-enhanced computed tomography findings revealed that 30 patients had low-risk GISTs and were recommended to receive endoscopic treatment, and 21 patients had medium-risk GISTs. In the medium- and high-risk group ( n = 26), 4 patients were identified by endoscopic ultrasound elastography to have low-risk GISTs, and 22 patients had medium- or high-risk GISTs. Contrast-enhanced computed tomography findings revealed that 9 patients were identified to have low-risk GISTs, and 17 patients had medium- or high-risk GISTs. Endoscopic ultrasound elastography yielded an overall diagnostic accuracy of 83.11% (64/77), while contrast-enhanced computed tomography had an overall diagnostic accuracy of 61.04% (47/77). Endoscopic ultrasound elastography outperformed contrast-enhanced computed tomography in accurate risk stratification of GISTs ( χ2 = 4.66, P < 0.05). In terms of predicting high-risk GISTs, endoscopic ultrasound elastography had a sensitivity of 84.62% and a specificity of 82.35%, both were higher than those of contrast-enhanced computed tomography (sensitivity: 65.38%; specificity: 58.82%), but the differences in sensitivity and specificity between the two techniques were not significant (sensitivity: Fisher's exact test P = 0.590, specificity: χ2 = 0.93, P > 0.05). Conclusion:Endoscopic ultrasound elastography appears to have a better overall diagnostic accuracy in the risk stratification of GISTs compared with contrast-enhanced computed tomography. The combined use of these two techniques may offer a better comprehensive understanding of the perilesional structure and organ involvements and distant metastasis than a single technique, thereby providing a reliable reference for the choice of treatment for GISTs.

Exploratory study on noninvasive evaluation of renal histopathology by ultrasonic shear wave elastography / 中华肾脏病杂志

Objective:To determine a relationship between ultrasound shear wave elastography (SWE) and pathological lessions of renal tissues in children with chronic kidney disease (CKD).Methods:It was a cross-sectional observational study, involving children admitted to the Department of Pediatrics of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology from January to December 2021 with definite pathological diagnosis through kidney biopsy. The SWE was used to determine the Young's modulus (elastic modulus) of the cortex and medulla of the upper, middle, and lower poles of the kidney. The renal histopathology was classified or graded. The statistical method was used to analyze the relationship between Young's modulus of the inferior polar cortex (YM cor) and medulla (YM med) of the right kidney and renal pathology. Results:The study included 110 children with definite pathological diagnosis through renal biopsy, aged (10.1±3.4) years old (2-17 years old), with 55 males (50.0%). The body mass index was (20.6±2.4) kg/m 2, and mean arterial pressure was (95±24) mmHg. There were 94 patients (85.4%) with CKD stage 1, 8 patients (7.3%) with CKD stage 2, and 8 patients (7.3%) with CKD stage 3. There was no significant difference of YM cor and YM med in the upper and middle poles of the right kidneys, and YM med in the lower poles of right kidneys in CKD patients with different stages (all P>0.05). Both YM cor [(15.75±3.36) kPa] and YM med [(13.50±2.43) kPa] of CKD stage 3 patients were significantly higher than those of CKD stage 1 patients [(12.94±2.45) kPa, (11.88±2.23) kPa](both P<0.05). There was no significant difference of YM cor and YM med in the lower poles of right kidneys between stage 1 and stage 2 CKD patients (both P>0.05). YM cor[(17.93±3.23) kPa] and YM med [(15.50±1.48) kPa] in patients with crescentic glomerulonephritis were higher than those in patients with focal segmental glomerulosclerosis [(12.71±2.42) kPa, (11.57±2.63) kPa] and mesangial proliferative glomerulonephritis [(12.73±2.04) kPa, (11.48±2.10) kPa](all P<0.05). There was no significant difference of YM cor and YM med between focal segmental glomerulosclerosis and mesangial proliferative glomerulonephritis (both P>0.05). YM cor [(16.30±2.63) kPa] and YM med [(15.54±1.59) kPa] of Lee's Ⅳ grade of IgA nephropathy were higher than those of Lee's Ⅲ grade [(13.32±2.70) kPa, (12.57±2.50) kPa](both P<0.05), while the International Study of Kidney Disease in Children grade of purpura nephritis had no significant correlation with YM cor and YM med (both P>0.05). YM cor [(15.41±2.37) kPa] and YM med [(13.82±2.59) kPa] of interstitial fibrosis/tubular atrophy (T1/T2) group of IgA nephropathy mixed with purpura nephritis were significantly higher than those of T0 group's [(12.99±2.40) kPa, (11.79±2.05) kPa] (both P<0.05). Moreover, crescent formation (C1) group had a higher YM cor [(14.21±2.77) kPa] and YM med [(12.80±2.47) kPa] than those in C0 group [(12.73±2.15) kPa, (11.59±1.97) kPa] (both P<0.05), while YM cor and YM med were unrelated to the mesangial hypercellularity (M), endocapillary cellularity (E), segmental sclerosis or adhesion (S) indicators (all P>0.05). In lupus nephritis patients, YM cor ( r=0.744, P=0.035) and YM med ( r=0.728, P=0.009) were favorably linked with the chronic index, but not with the activity index (both P>0.05). Conclusions:Renal interstitial fibrosis/tubular atrophy and crescentic development are connected with YM cor and YM med at the lower pole of the kidney as measured by SWE. SWE can be used to assess the chronic renal lesions in children with CKD in the early and middle stages. It may develop into a new noninvasive way to assess renal pathology.

Adventitial Collagen Cross-Linking by Glutaraldehyde Reinforcing Human Saphenous Vein - Implication for Coronary Artery Bypass Grafting

ABSTRACT Introduction: A weak venous wall is one of the major reasons contributing to vein graft failure after coronary artery bypass grafting (CABG). We investigated whether adventitial collagen cross-linking by glutaraldehyde reinforces venous wall, preserving the endothelium of veins during high-pressure distention. Methods: Human saphenous veins (SVs) were collected from 40 patients undergoing CABG, and adventitia cross-linking was performed with 0.3% glutaraldehyde for five minutes. The cross-linked SVs were accessed by biodegradation assay, immunofluorescent staining, and tensile test. Native SVs and cross-linked SVs from another 20 patients received the 200 mmHg pressure distention for two minutes. Pressure-induced injury of SVs were accessed by immunohistochemistry and electron microscopy. Results: Time to digestion was 97±13 minutes for native SVs and 720±0 minutes for cross-linked SVs (P<0.05). After adventitial cross-linking, the collagen I fibres of the vein remarkably presented with compact and nonporous arrangement. In the high-stretch region (stretch ratio 1.4-1.8), the Young's elastic modulus of stress-stretch ratio curve in cross-linked SVs was larger than that in native SVs (13.88 vs. 5.83, P<0.05). The cross-linked SVs had a lower extent of endothelial denudation without fibre fracture during high-pressure distension than native SVs. Comparing with the non-cross-linked SVs, the percentage of endothelial nitric oxide synthase staining length on the endothelium of cross-linked SVs was significantly preserved after high-pressure distension (85.2% vs. 64.7%, P<0.05). Conclusion: Adventitial collagen cross-linking by glutaraldehyde reinforced venous wall by increasing stiffness and decreasing extensibility of SVs and mitigated the endothelial damage under high-pressure distension.

Eye bank versus surgeon prepared Descemet stripping automated endothelial keratoplasty tissues: Influence on adhesion force in a pilot study

Purpose: To evaluate and compare the biomechanical properties of the eye bank?prepared and surgeon prepared Descemet stripping automated endothelial keratoplasty (DSAEK) tissues. Methods: In this laboratory study, corneal tissues for research were randomly allocated in the following groups: a) surgeon?cut DSAEK and b) eye bank?prepared (pre?cut and pre?loaded) DSAEK. Endothelial cell loss (ECL), immunostaining for tight junction protein ZO?1, elastic modulus, and adhesion force were investigated. Results: ECL was not found to be significantly different between surgeon?cut DSAEK (7.8% ±6.5%), pre?cut DSAEK (8.6% ±2.3%), and pre?loaded DSAEK (11.1% ±4.8%) (P = 0.5910). ZO?1 was expressed equally across all groups. Surgeon?cut DSAEK grafts showed a significantly higher elastic modulus compared to pre?cut and pre?loaded DSAEK groups (P = 0.0047 and P < 0.0001, respectively). Adhesion force was significantly greater in the surgeon?cut DSAEK compared to pre?cut (P < 0.0001) or pre?loaded DSAEK groups (P = 0.0101). Conclusion: The laboratory data on the biomechanics of DSAEK grafts suggests that surgeon?cut DSAEK grafts present higher elastic modulus and adhesion force compared to eye bank?prepared DSAEK grafts.

Finite Element Analysis and Clinical Research Progress of Tympanic Membrane Perforation and Tympanic Membrane Repair Materials / 医用生物力学

Tympanic membrane perforation is one of the common diseases in otolaryngology. The main causes of tympanic membrane perforation are otitis,trauma and etc. With the rapid development of finite element analysis method, this method is applied to clinical evaluation of tympanic membrane perforation and repair materials. By establishing the finite element model of the middle ear, the characteristics of tympanic membrane perforation and tympanic membrane repair materials were analyzed from the biomechanical aspect, with combination of clinical application results. In this review, the finite element analysis and clinic research progress of tympanic menbrane perforation and tympanic membrane repair materials were summarized.

Preparation and characterization of dissolving microneedles with nano-enhanced mechanical properties / 药学学报

In this paper, the effects of the blend of nanoparticles and microneedle matrix materials on the mechanical properties of dissolving microneedles were studied mainly, so as to construct microneedles with excellent mechanical properties. Different kinds of nanoparticles (calcium carbonate, hydroxyapatite, silica), particle sizes (20, 60, 100 nm) and the proportion of prescription (2%, 6%, 10%) were blended with the matrix material [polyvinyl pyrrolidone (PVP), poly(1-vinylpyrrolidone-co-vinyl acetate)(PVP/VA)] to form dissolving microneedles. The effects of nanoparticles on the elastic modulus and hardness of the microneedles were investigated using a nanoindenter. The results showed that the elastic modulus and hardness of PVP microneedles were significantly improved by nano-calcium carbonate (P < 0.001), and the elastic modulus and hardness of PVP/VA microneedles were significantly improved by nano-hydroxyapatite (P < 0.001). When the particle size of hydroxyapatite was 20 nm, the elastic modulus of PVP/VA microneedles was (10.6 ± 1.0) GPa, and the hardness was (0.47 ± 0.06) GPa. As the size of the nanoparticles increases, the mechanical performance of the microneedles decreases. When the mass proportion of nano-hydroxyapatite increased from 2% to 6%, the elastic modulus and hardness of the microneedles were significantly improved (P < 0.001), but the effect of continue increasing the proportion of nanoparticles on the microneedles was not significant. The nano-enhanced PVP/VA dissolving microneedles has no irritant effect on intact skin and has a slight irritation to damaged skin, but they disappear completely after 72 h. Animal experiments have been approved by the Laboratory Animal Welfare and Ethics Committee of Zhejiang University of Technology. Therefore, the nano-enhanced dissolving microneedles has good biological safety. To sum up, it is necessary to select the appropriate kind of nanoparticle, particle size, and prescription ratio when microneedles constructing with a given matrix material, so as to effectively improve its mechanical performance.

Effects of Liquid Medium Environment on Elastic Modulus of Breast Cancer Cells / 医用生物力学

Objective To study the effect of three kinds of commonly used liquid culture media for in vitro cell experiments on elastic modulus of breast cancer cells, so as to provide references for developing novel diagnosis and treatment approach of tumour based on mechanics principles. Methods The elastic modulus and adhesion force of breast cancer cells MCF7 to atomic force microscopy (AFM) probes in phosphate buffered solution(PBS), Dulbecco’s modified eagle media (DMEM) and DMEM+10% fetal bovine serum (FBS) were measured using AFM technology. Results The elastic moduli of breast cancer cells in PBS, DMEM and DMEM+10% FBS were 2.59, 2.11 and 1.59 kPa, respectively. The cell adhesion forces in the above three kinds of liquid medium environment were 63.81, 66.09 and 121.97 pN, respectively. Cell adhesion force in DMEM+10%FBS was significantly different from that of the other two kinds of liquid media. Conclusions There are significant differences in elastic modulus of breast cancer cells in three kinds of liquid media. The difference between DMEM and DMEM+10%FBS might be caused by the different adhesion force caused by serum proteins in the media, and the difference between DMEM and PBS might be attributed to the difference in pH of the media.

Mechanical Properties of Calcification from Human Aortic Valve / 医用生物力学

Objective To measure mechanical properties of calcified tissues from human aortic valve by nanoindentation test. Methods Leaflets from 5 patients with aortic stenosis were collected. Elastic modulus and hardness of the calcified leaflets were obtained by nanoindentationtest. Results The elastic modulus and hardness of the calcified leaflets were (15.69±3.89) GPa and (0.59±0.15) GPa, respectively. Conclusions The elastic modulus and hardness of the calcified valve tissues can be obtained by nanoindentationtest, which provides experimental data for biomechanical research of the valve.

Prediction Method of Elastic Modulus of Trabecular Bone Based on SE-DenseVoxNet / 中国医疗器械杂志

Osteoporosis is one of the common metabolic diseases, which can easily lead to osteoporotic fractures. Accurate prediction of bone biomechanical properties is of great significance for the early prevention and diagnosis of osteoporosis. Bone mineral density measurement is currently used clinically as the gold standard for assessing bone strength and diagnosing osteoporosis, but studies have shown that bone mineral density can only explain 60% to 70% of bone strength changes, and trabecular bone microstructure is an important factor affecting bone strength. In order to establish the connection between trabecular bone microstructure and bone strength, this paper proposes a prediction method of trabecular bone modulus based on SE-DenseVoxNet. This method takes three-dimensional binary images of trabecular bone as input and predicts its elastic modulus in the z-axis direction. Experiments show that the error and bias between the predicted value of the method and the true value of the sample are small and have good consistency.

Effect of antioxidant agents after dental bleaching on luting of ceramic laminates / Efeito de agentes antioxidantes pós-clareamento na cimentação de laminados cerâmicos

O objetivo deste estudo in vitro foi avaliar o efeito da aplicação de agentes antioxidantes após o clareamento dentário e previamente à cimentação de laminados cerâmicos na estabilidade cromática do conjunto restaurador, assim como nas propriedades mecânicas de nanodureza (HIT), módulo de elasticidade (Eit*), grau de conversão, resistência de união e morfologia da interface adesiva. Ademais, a neutralização de peróxido de hidrogênio e a caracterização superficial do esmalte, como ângulo de contato, energia de superfície, energia livre total de interação, microscopia eletrônica de varredura e espectroscopia de energia dispersiva do substrato submetido à ação das soluções antioxidantes e do agente clareador também foram analisados. Duzentos e quarenta e dois blocos de esmalte dentário (7x8x0,6mm) foram utilizados para o processo de cimentação e distribuídos em grupos experimentais de acordo com os métodos de procedimentos (grupo não clareado, grupo clareado com Whiteness HP Maxx 35%), tipos de antioxidantes adotados (controle; ácido ascórbico 10% e α-tocoferol 10%) e períodos de cimentação (após 24 horas e 14 dias do processo de cimentação) (n = 22). Foi utilizado o sistema adesivo Tetric N Bond Universal e o cimento resinoso Variolink Esthetic LC (Ivoclar Vivadent) como agentes cimentantes. Os dados foram submetidos a testes estatísticos de normalidade e analisados por ANOVA e teste de Tukey (α = 0,05). Os dados da morfologia da interface adesiva, obtidas pela microscopia confocal a laser, foram submetidas ao teste Kappa inter-examinadores e os dados foram submetidos aos testes Kruskal-Wallis e Dunn (α = 0,05). Os resultados mostraram que, de modo geral, a utilização da solução antioxidante α-tocoferol 10% pós-clareamento no período mediato promoveu resultados satisfatórios com relação à estabilidade cromática do conjunto restaurador, assim como para as propriedades mecânicas, grau de conversão, resistência de união e morfologia da interface adesiva comparado ao grupo clareado sem associação dos agentes antioxidantes, tanto para o período mediato, quanto para o período de 14 dias (p< 0,05). A solução de αtocoferol 10% apresentou maiores valores de neutralização do peróxido de hidrogênio e maiores valores de molhabilidade do esmalte em relação aos grupos controle e ácido ascórbico (p< 0,05). A energia de superfície e energia livre total de interação do esmalte dentário foi significativamente influenciada pelo tratamento clareador (p< 0,05). Dessa forma, conclui-se que o emprego da solução antioxidante α-tocoferol 10% promoveu resultados promissores, sugerindo que o mesmo poderia ser utilizado mediatamente após o clareamento dental na cimentação de laminados cerâmicos(AU)

The aim of this in vitro study was to evaluate the effect of antioxidant agents application after tooth bleaching and prior to luting of ceramic veneers on color stability of the restorative set, as well as on mechanical properties of nanohardness (HIT), elastic modulus (Eit*), degree of conversion, bond strength and morphology of the adhesive interface. Furthermore, the hydrogen peroxide neutralization and surface characterization of enamel, such as contact angle, surface energy, total free energy of interaction, scanning electron microscopy and energy-dispersive spectroscopy of the substrate submitted to the action of antioxidant solutions and bleaching agent were also analyzed. Two hundred forty two dental enamel blocks (7 x 8 x 0.6 mm) were used for the luting process and distributed into experimental groups according to the procedure methods (unbleached group, bleached group with Whiteness HP Maxx 35%), types of antioxidants adopted (control; 10% ascorbic acid and 10% α-tocopherol) and the luting periods (24 hours and 14 days after the luting process) (n = 22). Tetric N Bond Universal adhesive system and Variolink Esthetic LC resin cement (Ivoclar Vivadent) were used as luting agents. Data were submitted to statistical tests of normality and analyzed by ANOVA and Tukey tests (α = 0.05). The adhesive interface morphology data, obtained by confocal laser microscopy, were submitted to the interexaminer Kappa test and the data were submitted to Kruskal-Wallis and Dunn´s tests (α = 0.05). The results showed that, in general, the use of 10% α-tocopherol antioxidant solution after bleaching in mediate period promoted satisfactory results regarding the color stability of the restorative set, as well as for the mechanical properties, degree of conversion, shear bond strength and adhesive interface morphology compared to the bleached group without antioxidant agents association, both for the mediate and 14-day period (P < 0.05). The 10% αtocopherol solution showed higher hydrogen peroxide neutralization values and higher enamel wettability values compared to the control and ascorbic acid groups (P < 0.05). Surface energy and total free energy of interaction of tooth enamel were significantly influenced by the bleaching treatment (P < 0.05). Thus, it is concluded that the use of 10% αtocopherol antioxidant solution promoted promising results, suggesting that it could be used mediately after tooth bleaching on luting of ceramic laminates(AU)

Application Value of Transrectal Shear Wave Elastography Mode Combined with Elastic Modulus in the Diagnosis of Prostate Cancer / 中国医学科学院学报

To explore the value of trans-rectal shear wave elastic mode combined with elastic modulus in the diagnosis of prostate cancer and establish a new method for the evaluation of prostate with trans-rectal shear wave elastography(SWE). The typical findings of trans-rectal ultrasound(US)and SWE in 79 patients with prostate cancer(=41)and benign prostatic hyperplasia(BPH)(=38)confirmed by surgery or US-guided biopsy were analyzed retrospectively.Their diagnostic value were evaluated with the pathological results as the golden standards. Three or more malignant features detected by conventional trans-rectal US(=42.5,<0.001)and asymmetrical SWE mode(=54.2,<0.001)showed statistically significant difference in prostate cancer and BPH groups.The elastic modulus of Emean and Emax in the prostate cancer group were(92.8±21.5)and(114.2±29.8)kPa,which were significantly higher than those in the BPH group [(56.7±14.0)(=-8.8,<0.001)and(68.4±17.2)kPa(=-8.3,<0.001)].The receiver-operating characteristic(ROC)curve with Logistic regression showed that the elastic model combined elastic modulus had the largest area under ROC curve and the highest diagnosis efficiency of prostate cancer,with the cutoff value of 0.45.The diagnosis sensitivity,specificity,positive predictive value,negative predictive value,and accuracy of the combination were 95.1%,89.5%,90.7%,94.4%,and 92.4%,respectively. Combination of SWE mode and elastic modulus is more valuable than elastic modulus alone in the diagnosis of prostate cancer.

Research progresses of ultrasound elastography evaluation on post-stroke spasticity / 中国医学影像技术

Ultrasonic elasticity (UE) is a new type ultrasonic diagnosis technology able to directly measure elastic modulus and reflect muscle stiffness,which has gradually been applied to quantitatively evaluate the degree of post-stroke spasticity (PSS) and guide treatment. The research progresses of UE for evaluation PSS were reviewed in this article.

Correlation between Biomechanical Changes at the End of Left Ventricular Systole and Pathogenesis of Diastolic Heart Failure / 医用生物力学

Objective To analyze the correlation of the maximum myocardial stiffness (maxEav), maximum modulus of elasticity (Emax) with the E/A ratio of mltral annulus at the end of left ventricular systole for patients with essential hypertension. Methods 298 patients with essential hypertension were selected as research objects. The left ventricular mass index (LVMI) and relative wall thickness (RWT) of the patients were calculated. Based on LVMI and RWT indexes, the patients were divided into left ventricular normal (LVN) group, left ventricular concentric remodeling (LVCR) group, left ventricular eccentric hypertrophy (LVEH) group, left ventricular concentric hypertrophy (LVCH) group, respectively. In addition, 115 healthy subjects were selected into control group. The subjects were diagnosed by echocardiography, so as to analyze the correlation of maxEav, Emax with E/A. Results The maxEav, Emax and E/A in LVCR group, LVEH group and LVCH group were all negatively correlated. The differences of E/A between LVCR group, LVCH group and control group showed statistical significance. Compared with control groups, both the maxEav and Emax in hypertension group decreased, and the difference was statistically significant. Conclusions The maxEav and Emax are more sensitive and easy indexes to judge left ventricular diastolic function. The analysis on maxEav and Emax changes in patients with left ventricular remodeling and diastolic dysfunction in hypertension, as well as the exploration on pathogenesis of diastolic heart failure, can provide the theoretical basis for prevention and treatment of diastolic heart failure in the future.

Study on mixing technology of post-crosslinking Daphnes Giraldii Cortex gel plaster based on rheological indexes / 中草药

Objective: To optimize the mixing technology of Daphnes Giraldii Cortex gel plaster (DGCGP) by using rheological parameters elastic modulus (G'), viscous modulus (G″), yield stress (τ0), creep compliance [J(t)] and loss coefficient (tanδ) as evaluation indexes. Methods: Using orthogonal design, L9(34) orthogonal design was used to screen out the best mixing technology of DGCGP and predict the suitable coating conditions by taking the temperature, rotating speed and mixing time of the mixed materials as influencing factors and the rheological parameters of the medicated compound as evaluating indexes. Results: The optimum DGCGP mixing process was as following: 70℃ at 10 r/min for 2 h. Under this condition, the viscoelasticity, temperature and shear resistance, deformation resistance and stability of the mixture were all good. Conclusion: DGCGP prepared by this optimized process had good appearance, soft texture, good adhesion with skin, good viscoelasticity and better quality.

Structure and mechanical properties of high- and low-weight-bearing areas of hip cartilage at micro and nano levels / 中国组织工程研究

BACKGROUND: Articular cartilage has a high-weight-bearing area and a low-weight-bearing area. There are different macroscopic elastic moduli in the two regions, but the modulus of the two areas at the micro and nano levels is unknown. Such information is important for further understanding of cartilage micro and nano mechanics. Moreover, the micro and nano structures of the two areas, which influence the cartilage mechanical properties, should be discussed. OBJECTIVE: To investigate the mechanical properties and structure of high- and low-weight-bearing areas of the hip articular cartilage at the micro and nano levels. METHODS: Normal porcine femoral head cartilage was used. Atomic force microscopy with a spherical tip of 5 µm in diameter was used to measure the microscale compressive elastic modulus of different weight-bearing areas of the cartilage. The nanoscale compressive elastic modulus, nano structure, and collagen fiber diameter were measured using a ScanAsyst-Air probe with a radius of curvature of 5 nm. Scanning electron microscopy was employed to identify the microstructure of different weight-bearing areas of the cartilage. RESULTS AND CONCLUSION: The microscale elastic modulus of the high-weight-bearing area of the femoral head cartilage was (433.05±146.52) kPa, and the microscale elastic modulus of the low-weight-bearing area was (331.19±84.88) kPa. The nanoscale elastic modulus of the high- and low-weight-bearing areas of the femoral head cartilage was (1.24±0.42) GPa and (1.28±0.41) GPa, respectively. While no statistically significant differences were found in the elastic modulus of collagen fibers at the nano level (P=0.846 2). The collagen fibers of the high-weight-bearing area arranged more regularly than those of the low-weight-bearing area at the micro level. No significant differences between collagen fiber diameter of the two areas at the nano level were observed (P=0.926 4). To conclude, the collagen fibers of the high-weight-bearing area are cross-linked more regularly than those of low-weight-bearing area. Therefore, the compressive elastic modulus of the high-weight-bearing area at the micro level is significantly higher than that of the low-weight-bearing area, which is consistent with the macroscopic compressive elastic modulus trend. However, high-weight-bearing has no impact on individual collagen fibers at the nano level.