Effect of the different debonding strength of metal and ceramic brackets on the degree of enamel microcrack healing

ABSTRACT Objective: This study aims to determine shear debonding strength of metal and ceramic brackets, and the degree of enamel crack healing. Material and Methods: Extracted human maxillary premolars were flattened on the buccal surface, and randomly separated into five groups (n = 15). In control groups (groups 1 and 2), metal and ceramic brackets were bonded on flat polished enamel, while in experimental groups (groups 3 and 4), metal and ceramic brackets were bonded on the surface with boundary where corner cracks were created. Additionally, fifteen specimens (group 5) were also prepared for an indentation procedure with no bracket installation. The degree of crack healing was measured. All brackets were detached with a universal testing machine, and the adhesive remnant index (ARI) was also identified. Healing degree and apparent fracture toughness were then calculated. Results: Between groups with similar bracket types, there was no statistically significant difference in debonding strength. Regarding bracket types, ceramic brackets provided significantly higher debonding strength than metal brackets. There was a significant difference in ARI scores between metal and ceramic brackets. The corner cracks showed signs of healing in both horizontal and vertical directions. No statistically significant difference in the healing rates among the groups was found and the apparent fracture toughness increased from the initial to the final measurement. Conclusions: Within the limitations of this study, even though ceramic brackets required significantly higher debonding force compared to metal brackets, debonding stress was limited to the bonding site and did not affect the surrounding cracks on enamel.

RESUMO Objetivo: O presente estudo teve como objetivo determinar a resistência ao cisalhamento de braquetes metálicos e cerâmicos, e o grau de reparo de fraturas no esmalte. Métodos: Pré-molares superiores, extraídos de humanos, foram aplainados na face vestibular e aleatoriamente divididos em cinco grupos (n = 15). Nos grupos controle (Grupos 1 e 2), os braquetes metálicos e cerâmicos foram colados em esmalte liso e polido; enquanto nos grupos experimentais (Grupos 3 e 4), os braquetes metálicos e cerâmicos foram colados em superfície delimitada, em cujos cantos foram criadas fissuras. Adicionalmente, foram também preparados 15 espécimes (Grupo 5) para um teste com indentação, sem a instalação de braquetes. O grau de reparo das fraturas foi avaliado. Todos os braquetes foram descolados usando uma máquina universal de testes, e o índice de adesivo remanescente (ARI) também foi avaliado. O grau de reparo e a tenacidade à fratura aparente foram então calculados. Resultados: Entre os grupos com o mesmo tipo de braquetes, não houve diferença estatisticamente significativa na força de descolagem. Com relação aos tipos de braquetes, os cerâmicos apresentaram uma força de descolagem significativamente maior do que os metálicos. Houve uma diferença significativa nos escores ARI entre os braquetes metálicos e os cerâmicos. As fraturas de canto mostraram sinais de reparo nos sentidos horizontal e vertical. Não foi detectada diferença estatisticamente significativa no grau de reparo entre os grupos, e a tenacidade à fratura aparente aumentou da mensuração inicial para a final. Conclusão: Considerando-se as limitações desse estudo, apesar de os braquetes cerâmicos necessitarem de força de descolagem significativamente maior do que os braquetes metálicos, a tensão de descolagem foi limitada ao sítio de colagem, não afetando as fraturas de esmalte ao redor.

Regional Mechanical Properties of the Sclera / 医用生物力学

Objective To investigate the differences in mechanical properties of the sclera in different regions. Methods The sclera of sus scrofa was divided into 3 regions, namely, anterior, equatorial and posterior area. Local indentation was performed on different areas of the whole sclera. Strip specimens of different regions were circumcised along the equatorial direction, and subjected to uniaxial stretching by INSTRON 5544. Results Within the normal physiological stress range, the stiffness at anterior, equatorial, and posterior area of the sclera measured by local indentation was (0.91±0.21), (0.6±0.16), (0.39±0.13) MPa, respectively. The elastic modulus at anterior, equatorial, and posterior area of the sclera measured by uniaxial stretching was (1-28±0.37), (0.95±0.31), (0.72±0.28) MPa, respectively. Conclusions The local indentation could reflect regional mechanical properties of the sclera. The anterior sclera performed a higher stiffness than the equatorial and posterior areas. The results provide references for further study on the pathogenesis of ocular diseases including myopia.

Distribution characteristics and clinical significance of clavicle microindentation hardness / 中华创伤杂志

Objective To investigate the distribution characteristics and significance of bone hardness in different segments and layers of clavicle. Methods The right clavicles of three fresh Chinese corpses were taken and then divided into proximal, middle and distal segments according to Allman's classification. The clavicles were cut with diamond saw in the vertical of long axis equidistant exactly into 15 layers ( proximal:3 layers; midshaft:7 layers; distal:5 layers ) , and each layer was divided into four directions:superior, inferior, anterior, and posterior. The bone hardness were measured by Vickers microindentation, HV ( kgf/mm2 ) . The distribution of bone hardness was recorded and analyzed. Results A total of 180 parts of cortical bone were measured, generating 900 measurements. Meanwhile, a total of 45 parts of cancellous bone were measured, generating 225 measurements. We found that:(1)The average hardness of cortical bone was (35.9 ±8.1)HV, and the midshaft segment[(41.3 ±6.8)HV] was harder than the proximal segment [(33.8 ±6.1)HV] and the distal segment [(29.7±5.4)HV](P<0.05);(2)Theaveragehardnessofcancellousbonewas(30.7±6.2)HV, and there were significant differences among the midshaft segment [(34. 5 ± 5. 5)HV], the proximal segment [(29.2±2.9)HV] and the distal segment [(26.3 ±5.1)HV](P<0.05);(3)for cortical bone, the hardest segment was the fifth layer of the midshaft segment [(44. 8 ± 8. 6)HV] while the most soft segment was the fourth layer of the distal segment [(28. 0 ± 3. 5)HV](P<0. 05);(4)for cancellous bone, the hardest segment was the fifth layer of the midshaft segmnet [(36. 8 ± 5. 1)HV] while the most soft was the fifth layer of the distal segment [(23. 0 ± 4. 4) HV] (P<0. 05);(5) There were no statistically significant differences among four directions of segments(P >0. 05). Conclusion The microindentation hardness varies greatly among different segments and layers of the clavicles. The cortical bone and cancellous bone have consistent hardness changes, which shows that the middle segment is obviously harder than the proximal and distal segments with a gradually gradient decreasing trend from the middle to both ends. The data can be used to guide the design of 3D printing implants that conform to the stress conduction characteristics of the clavicle under physiological conditions, and provide good data support for the modeling and finite element analysis of the clavicle under simulated physiological conditions.

Distribution characteristics and clinical significance of clavicle microindentation hardness / 中华创伤杂志

Objective@#To investigate the distribution characteristics and significance of bone hardness in different segments and layers of clavicle.@*Methods@#The right clavicles of three fresh Chinese corpses were taken and then divided into proximal, middle and distal segments according to Allman's classification. The clavicles were cut with diamond saw in the vertical of long axis equidistant exactly into 15 layers (proximal: 3 layers; midshaft: 7 layers; distal: 5 layers), and each layer was divided into four directions: superior, inferior, anterior, and posterior. The bone hardness were measured by Vickers microindentation, HV(kgf/mm2). The distribution of bone hardness was recorded and analyzed.@*Results@#A total of 180 parts of cortical bone were measured, generating 900 measurements. Meanwhile, a total of 45 parts of cancellous bone were measured, generating 225 measurements. We found that: (1)The average hardness of cortical bone was (35.9±8.1)HV, and the midshaft segment [(41.3±6.8)HV] was harder than the proximal segment [(33.8±6.1)HV] and the distal segment [(29.7±5.4)HV](P<0.05); (2)The average hardness of cancellous bone was (30.7±6.2)HV, and there were significant differences among the midshaft segment [(34.5±5.5)HV], the proximal segment [(29.2±2.9)HV] and the distal segment [(26.3±5.1)HV](P<0.05); (3)for cortical bone, the hardest segment was the fifth layer of the midshaft segment [(44.8±8.6)HV] while the most soft segment was the fourth layer of the distal segment [(28.0±3.5)HV](P<0.05); (4)for cancellous bone, the hardest segment was the fifth layer of the midshaft segmnet [(36.8±5.1)HV] while the most soft was the fifth layer of the distal segment [(23.0±4.4)HV](P<0.05); (5)There were no statistically significant differences among four directions of segments(P>0.05).@*Conclusion@#The microindentation hardness varies greatly among different segments and layers of the clavicles. The cortical bone and cancellous bone have consistent hardness changes, which shows that the middle segment is obviously harder than the proximal and distal segments with a gradually gradient decreasing trend from the middle to both ends. The data can be used to guide the design of 3D printing implants that conform to the stress conduction characteristics of the clavicle under physiological conditions, and provide good data support for the modeling and finite element analysis of the clavicle under simulated physiological conditions.

Severe Hemifacial Spasm is a Predictor of Severe Indentation and Facial Palsy after Microdecompression Surgery

BACKGROUND AND PURPOSE: Hemifacial spasm (HFS) is mostly caused by the compression of the facial nerve by cerebral vessels, but the significance of spasm severity remains unclear. We investigated the clinical significance of spasm severity in patients with HFS who underwent microvascular decompression (MVD). METHODS: We enrolled 636 patients with HFS who underwent MVD between May 2010 and December 2013 at Samsung Medical Center (SMC), Seoul, Korea. Subjects were divided into two groups based on spasm severity: severe (SMC grade 3 or 4) and mild (SMC grade 1 or 2). We compared demographic, clinical, and surgical data between these two groups. RESULTS: The severe-spasm group was older and had a longer disease duration at the time of MVD compared to the mild-spasm group. Additionally, hypertension and diabetes mellitus were more common in the severe-spasm group than in the mild-spasm group. Regarding surgical findings, there were more patients with multiple offending vessels and more-severe indentations in the severe-spasm group than in the mild-spasm group. Even though the surgical outcomes did not differ, the incidence of delayed facial palsy after MVD was higher in the severe-spasm group than in the mild-spasm group. Logistic regression analysis showed that severe-spasm was correlated with longer disease duration, hypertension, severe indentation, multiple offending vessels, and delayed facial palsy after MVD. CONCLUSIONS: Spasm severity does not predict surgical outcomes, but it can be used as a marker of pathologic compression in MVD for HFS, and be considered as a predictor of delayed facial palsy after MVD.

Detection of the viscoelasticity of relaxed myocardium in vivo by intervention ultrasound indentation system / 解放军医学杂志

Objective To explore the viscoelasticity of relaxed myocardium in vivo through indentation method with an intervention ultrasound indentation system (IUIS). Methods Old myocardial infarction (OMI) models of canine were established by ligating left anterior descending branch of coronary artery for 3 months. The indentation creep tests were used respectively in OMI group and shame group (n=8, each) by IUIS in middle and advanced diastole stage in vivo. Test data were processed with three-parameter solid viscoelasticity model, and the viscoelastic parameters, such as instantaneous elastic modulus (E1), relaxation modulus (E∞), creep elastic modulus (E2) and viscous damping coefficient (η) in normal and infarcted myocardium were obtained and compared. Results All the parameters of E1, E∞, E2 and η increased obviously in OMI group than in sham group shown as follows: 27.81±6.74kPa vs. 6.78±2.43kPa; 17.87±3.59kPa vs. 4.52±1.56kPa; 49.54±14.35kPa vs. 16.82±12.37kPa and 1.97±0.78Pa.s vs. 0.66±0.40Pa.s. The differences were statistically significant (P<0.05). Conclusions IUIS is a feasible method to assess the viscoelasticity of relaxed myocardium in vivo. Three-parameter viscoelasticity model can be used to describe creep properties of relaxed myocardium. Both elastic modulus and viscosity resistance have increased in infarcted myocardium.

Cyclic Stretch Effects on Adipose-Derived Stem Cell Stiffness, Morphology and Smooth Muscle Cell Gene Expression

Recent investigations consider adipose-derived stemcells (ASCs) as a promising source of stemcells for clinical therapies. To obtain functional cells with enhanced cytoskeleton and aligned structure, mechanical stimuli are utilized during differentiation of stem cells to the target cells. Since function of muscle cells is associated with cytoskeleton, enhanced structure is especially essential for these cells when employed in tissue engineering. In this study by utilizing a custom-made device, effects of uniaxial tension (1Hz, 10% stretch) on cytoskeleton, cell alignment, cell elastic properties, and expression of smooth muscle cell (SMC) genes in ASCs are investigated.Due to proper availability ofASCs, results can be employed in cardiovascular engineeringwhen production of functional SMCs in arterial reconstruction is required. Results demonstrated that cells were oriented after 24 hours of cyclic stretch with aligned pseudo-podia. Staining of actin filaments confirmed enhanced polymerization and alignment of stress fibers. Such phenomenon resulted in stiffening of cell body which was quantified by atomic force microscopy (AFM). Expression of SM α-actin and SM22 α-actin as SMC associated genes were increased after cyclic stretch while GAPDH was considered as internal control gene. Finally, it was concluded that application of cyclic stretch on ASCs assists differentiation to SMC and enhances functionality of cells.

Indentation in the Right Ventricle by an Incomplete Pericardium on 3-Dimensional Reconstructed Computed Tomography

We report the case of a 17-year-old girl who presented with an indentation in the right ventricle caused by an incomplete pericardium on preoperative 3-dimensional reconstructed computed tomography. She was to undergo surgery for a partial atrioventricular septal defect and secundum atrial septal defect. Preoperative electrocardiography revealed occasional premature ventricular beats. We found the absence of the left side of the pericardium intraoperatively, and this absence caused strangulation of the diaphragmatic surface of the right ventricle. After correcting the lesion, the patient’s rhythm disturbances improved.

Corneal perforation during scleral indentation in a patient with pellucid marginal degeneration.

An observational case report of corneal perforation following scleral indentation in a patient with previously undiagnosed pellucid marginal degeneration is presented. Clinical examination, investigations, and subsequent management of this unwarranted and rare complication are described and discussed. The case highlights the need for thorough anterior segment examination before indirect ophthalmoscopy particularly in the presence of ectatic corneal pathology in which case scleral indentation should be avoided.

Usefulness of Three Dimensional Proset MR Images for Diagnosis of Symptomatic L5-S1 Foraminal and Extraforaminal Stenosis

OBJECTIVE: To suggest a new useful diagnostic technique, principles of the selective excitation technique-magnetic resonance images (Proset-MRI), and to know the precise radiologic findings that can prove symptomatic foraminal and extraforaminal stenosis at L5-S1. METHODS: Nineteen patients with symptomatic L5-S1 stenosis were checked by Proset-MRI. Four patients were performed decompressive surgery and 15 patients were performed selective nerve root block (SNRB) at L5. The pain scale of patients was checked by Visual Analogue Scale (VAS) scores at the pre- and post-treatment state. RESULTS: Proset-MRI findings of patients with symptomatic stenosis are root swelling (RS) and indentation. The comparisons with VAS scores had a meaningful statistical result at each RS (p<0.01) and indentation (p<0.01). However, the findings of RS combined with indentation lacked statistical significance (p=0.0249). In addition, according to a comparison with the treatment modalities, reducing of VAS scores had statistical meaningful significance in decompressive surgery cases (p<0.01), and also in SNRB cases (p<0.01) after a 3-month follow-up period. CONCLUSION: The three dimensional Proset-MRI is very useful and sensitive technique to diagnose the symptomatic foraminal and extraforaminal stenosis at L5-S1.

Ultrasound Elastography in Evaluation of Breast Lesions: Phantom and Clinical Studies

PURPOSE: The purpose of this study was to correlate the tissue stiffness measured using ultrasound elastography with directly measured tissue stiffness. MATERIALS AND METHODS: A phantom model consisting of five materials with different levels of stiffness was constructed. Forty one patients who were scheduled to undergo a vacuum-assisted biopsy for breast lesions were prospectively recruited for this study. Elasticity (E) score and strain index obtained with strain imaging were correlated with the directly measured stiffness value of phantom and core specimen. RESULTS: The E score and strain index of each phantom material showed a high level of correlation with the measured stiffness (E score: r = 0.985, P = 0.002; strain index: r = 0.964, P = 0.008). The E score and strain index of the breast lesions showed a low level of correlation with the reference standard (E score: r = 0.261, P = 0.100, strain index: r = 0.397, P = 0.014). The mean value of the E score was significantly greater in malignant (3.6) than in benign lesions (2.4) (P = 0.004). CONCLUSION: Stiffness of the phantom materials assessed by US strain imaging was well correlated with the reference standard of direct measurement. The E score can be used as a non-invasive diagnostic tool in differentiation of benign and malignant breast lesions.

Correlation study on biomechanics of three-foot weight bearing canine model with femoral head osteonecrosis / 医用生物力学

Objective To study changes in biomechanical characteristics of the femoral head during the progression of avascular osteonecrosis and investigate the mechanism of these biomechanical changes. Methods Twenty-four three-foot weight bearing canine models with osteonecrosis of the femoral head (ONFH) were established by fixing one fore limb of the canine. Osteonecrosis was induced in all experimental animals by randomly injecting 5 mL pure ethanol into one side of the femoral head, and the contralateral femoral head was injected with an equal amount of normal saline as the control group. The canines were killed at 1st, 3rd, 6th, and 12th week after the injection of ethanol, with six canines in each group. The radiographic, histological changes and biomechanical characteristics of the femoral head were observed and analyzed. Results At 3rd week, 29% reduction of indentation stiffness and 32.9% reduction of elastic modulus in the cancellous bone were found in the infected femoral heads compared to the control heads, and a low density area was detected only in MRI and osteonecrosis was the main histological characteristics. At 6th and 12th week, the indentation stiffness in the infected femoral heads was reduced by 45.5% and 48.7%, respectively, and the elastic modulus of the cancellous bone in the infected femoral heads was reduced by 34.1% and 32.4%, respectively, compared to the control heads. At 6th week, uneven bone density of the femoral head was detected in radiographs, and the progression of osteonecrosis and bone healing was found at the same time. At 12th week, areas of reduced bone mineral density beneath the load bearing position of the femoral head were observed on radiographs. Collapse of the articular cartilage surface and narrowing of the joint space were the main histological findings. Conclusions Biomechanics is an important factor in the progression of ONFH. The decreased mechanical properties may be a direct reason leading to the late collapse of the femoral head. The treatment of ONFH should focus not only on acceleration of the bone healing, but also on provision of a favorable and stable biomechanical environment for the infected femoral head.

Mechanical bearing characteristics and finite element analysis on bovine knee articular cartilage / 医用生物力学

Objective To analyze the relationship between compression deformation and mechanical bearing characteristics of articular cartilage. Methods Indentation test was used to measure the compression displacement of bovine knee articular cartilage with different indenter diameters and under different loads. The fluid flow and bearing characteristics of the articular cartilage were simulated by the finite element model. Results The maximum relative error between simulated maximum compression displacement and experimental result was 1.73%. The elastic modulus and permeability coefficient of cartilage increased with indenter diameter increasing under the same load, while decreased with indentation load increasing at the same indenter diameter. Fluid flow was mainly in the internal cartilage when the load was exerted on cartilage. With the load sustaining, fluid flow was gradually moved to outside of the cartilage. Pore pressure, axial stress and radial stress on the cartilage surface then presented a nonlinear change due to the fluid flow. Conclusions Fluid flow, pore pressure and stress distribution on the cartilage surface have a great impact on its bearing characteristics, which varies greatly with different indenters and under different loads.

Effect of Ibandronate and hPTH on the Viscoelastic Response of Ovariectomized Rat Femur / 대한골다공증학회지

PTH and ibandronate are proven to be effective in reversing negative effects of postmenopausal osteoporosis in terms of bone architecture and density. However, the changes of viscoelastic properties of the bone during the pathogenesis of osteoporosis and its treatment were seldom studied. Thus, this study aimed at studying the viscoelastic changes in PTH and ibandronate treated ovariectomized rat to assess the efficacy of the treatments. In this study, distal femurs of twenty-two female rats from four different groups (SHM, OVX, PTH and IBN) were evaluated using CT, pQCT and nanoindentation tests. While density parameters were well preserved in ibandronate treated group, elastic modulus and hardness were found to be better in PTH treated group. Thus, cortical and trabecular bone could be differentially affected by these two categories of drug, due to their difference in the action of mechanism. Moreover, viscosity of the cortical bone showed a positive correlation (R(2)=0.72) with bone strength predictor SSIy, which would possibly correlate with fracture risk.

Extrinsic Indentation at Gastric Fundus by Splenic Lymphangioma / 대한소화기내시경학회지

Splenic lymphangioma is a very rare benign condition, and it is classified as one of the cystic proliferations of the spleen. This is considered to result from developmental malformation of the lymphatic system. Splenic lymphangioma is usually seen in children and it is often found incidentally. Herein, we report on an unusual case of splenic lymphangioma in an adult. A 66-year-old woman presented with abdominal pain. On esophagogastroduodenoscopy, the gastric fundus was externally compressed by an extrinsic mass. Computed tomography revealed multiple cystic masses in the spleen. Laparoscopic splenectomy was then performed. The histology revealed multiple splenic lymphangiomas. This case showed an unusual presentation of splenic lymphangioma as gastric extrinsic compression, and this should be examined by imaging studies.

Femoral Head Fracture without Dislocation by Low-Energy Trauma in a Young Adult

We describe the case of a healthy young man with a femoral head fracture by low-energy trauma that occurred without evidence of hip dislocation. While plain radiographs showed no definite fracture or dislocation, computed tomography (CT) and magnetic resonance imaging (MRI) revealed a femoral head fracture with a wedge-shaped cortical depression at the superomedial aspect of the femoral head. Our patient reported feeling that the right hip had been displaced from its joint for a moment. This probably represented subluxation with spontaneous relocation. The characteristic findings and possible mechanisms of this fracture were postulated on the basis of the sequential 3 dimensional-CT and MRI. The clinical results of conservative treatment were better than those of previously reported indentation fractures.

Pseudo-gonio synechia: An artifact on two-mirror gonioscopy.

Gonioscopy is an important component of evaluation of any glaucoma patient. Goldmann two-mirror and Sussman or Zeiss four-mirror are the commonly used gonioscopes. Presence of synechia in the angle is diagnostic of angle closure disease in an occludable angle. A patient with pseudo-goniosynechia that disappeared on indentation gonioscopy with Sussman lens but persisted with manipulation gonioscopy with a Goldmann lens is reported.

Analysis in clinical efficiency of non-contact tonometer and indentation tonometer / 中国实用护理杂志

Objective To compare the measured IOP values by non-contact tonometer and indentation tonometer in order to evaluate the non-contact tonometer in clinical application. Methods 320 eyes of 160 patients for screening of IOP in the clinic were included in the observation, by self-control study, the IOP value of the non-contact tonometer(abbreviated NCT) and the indentation tonometer was compared. Results IOP values measured by NCT was lower than that mesgured by indentation tonometer. Conclusions IOP values measured by NCT was lower than that measured by indentation tonometer, for IOP value around 2.67 kPa measured by NCT, it is best to use indentation tonometer to retest or coming again for subsequent visit.

Analysis of the elastic-plastic indentation properties of materials with varying ratio of hardness to Young's modulus / 西安交通大学学报·英文版

The elastic-plastic indentation properties of materials with varying ratio of hardness to Young's modulus (H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.

Analysis of the elastic-plastic indentation properties of materials with varying ratio of hardness to Young's modulus / 药物分析学报

The elastic-plastic indentation properties of materials with varying ratio of hardness to Young's modulus (H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pileup and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.