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Large general hospitals currently play an increasingly important role in the diagnosis and treatment for acute critical patients and difficult diseases because of the development of dual referral system and hierarchical diagnosis, as well as the formation of medical treatment alliance. Patients with oral cancers are often associated with systemic diseases, which increases the complexity of the condition. Thus, meeting the demand through the traditional single medical model is difficult. As such, a multidisciplinary team (MDT) model has been proposed and has achieved a good clinical effect. To standardize the application of this model, we organized an event in which relevant experts discussed and formulated a consensus to provide standardized suggestions on the MDT process and the diagnosis and treatment of common systemic diseases as reference for clinical practice.
Subject(s)
Humans , Consensus , Mouth Neoplasms/therapy , Patient Care Team , Referral and ConsultationABSTRACT
Objective To investigate the variations of elastic modulus and hardness of human dentin with aging and location. Methods The non-carious third molars were collected and divided into youth group, middle-aged group and elderly group. Nanoidentation test was conducted on the dentin specimens from multiple regions to test their mechanical properties. Results The elastic modulus and hardness in outer and middle dentin were greater than those in inner dentin; the elastic modulus and hardness increased with the aging in each region of the dentin. Conclusions The dentin shows a gradient mechanical property. The stiffness and hardness in middle and outer dentin are greater than those in inner dentin. The deformation resistance in middle and outer dentin is stronger than that in inner dentin. Meanwhile, elastic modulus and hardness of the dentin increase with the aging.
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Objective To investigate the variations of elastic modulus and hardness of human dentin with aging and location.Methods The non-carious third molars were collected and divided into youth group,middle-aged group and elderly group.Nanoidentation test was conducted on the dentin specimens from multiple regions to test their mechanical properties.Results The elastic modulus and hardness in outer and middle dentin were greater than those in inner dentin;the elastic modulus and hardness increased with the aging in each region of the dentin.Conclusions The dentin shows a gradient mechanical property.The stiffness and hardness in middle and outer dentin are greater than those in inner dentin.The deformation resistance in middle and outer dentin is stronger than that in inner dentin.Meanwhile,elastic modulus and hardness of the dentin increase with the aging.
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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.
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Objective To study the feasibility of using digital volume correlation (DVC) method to track displacement and deformation of lung tumor and chest during the period of respiration. Methods A DVC algorithm suitable for tracking 3D movement of tissues in chest was proposed. The 4D CT imaging technique was adopted to acquire images of a patient with lung cancer during one complete respiration stage. The inhalation was set as the initial stage for reference, to determine the locations of lung cancer and chest. Four specified regions of both the tumor and chest at the initiation of inhalation stage were selected. The corresponding 3D displacement of lung in the following 5 inhalation phase stages, i.e. 20%, 40% 60%, 80% and 100% as well as 3D displacement of chest in 100% inhalation phase stage were analyzed by DVC software. Results The displacement and deformation error of tumor was within 1 mm, while that of chest was within 0.5 mm. The maximum displacement of tumor presented itself along the vertical direction of human body during respiration, while that of chest at the end of inhalation stage appeared along the front and back direction of human body. Conclusions DVC methods can be potentially used to detect displacement and deformation of body tissues such as lung tumor and chest during the respiratory cycle. This study provides references for noninvasive, non X-ray, real-time image-guided radiation therapy for lung cancer based on DVC method.
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The purpose of this study was to investigate how cyclic loading influenced the fracture toughness of hot-press lithium disilicate and zirconia core materials and whether there was an increase in the propensity for crown failure. Two types of all-ceramic crowns including the IPS e.max Press system (n=24) and the Lava zirconia system (n=24), were selected. Sectioned specimens were subjected to cyclic loading with the maximum magnitude of 200 N (R=0.1) until two million cycles. The material properties including Young's modulus (E) and hardness (H) and the fracture toughness (KIC) of the core materials were evaluated using indentation methods (n=12 each). The load-bearing capacities of the specimens were examined by means of monotonic load to fracture (n=12 each). It was found that the material properties, including E, H and KIC, of the two types of dental ceramics, were reduced. Statistical analysis indicated that there were no significant influences of fatigue loading on material properties E and H for both types of dental ceramics or KIC for zirconia, while for the IPS e.max Press core, KIC, which was parallel to the direction of the lithium disilicate crystals, was significantly reduced (P=0.001). A conclusion was drawn that zirconia possesses high mechanical reliability and sustainable capacity to resist fatigue loading, while fatigue loading remarkably degraded the anisotropic mechanical behaviour of hot-press lithium disilicate ceramics.
Subject(s)
Humans , Crowns , Mastication , Materials TestingABSTRACT
Objective To develop an improved DIC (digital image correlation) algorithm suitable for measuring large ROM (range of motion) of the cervical spine, as traditional DIC algorithm is not capable of accurately measuring ROM of the cervical spine due to its large rotation angles. Methods An algorithm which allowed rotation of the subset window was proposed to achieve robust correlation matching in the measurement. A new iterative variable, which represented the orientation of the subset, was introduced and incorporated in the Newton-Raphson iteration method together with the position variables (x,y). By assigning an initial guess to these variables individually, the precise location and rotation angle could be determined in the deformed image. The precision of the proposed method was evaluated by translation and rotation experiments. ResultsThe translation experiment confirmed that the proposed method had the same accuracy as the traditional DIC, and the displacement measurement accuracy was within 0.5%. While the rotation experiment indicated that the proposed method could measure the deformation at any angles with precision less than 0.5°. The method was then applied to the measurement of ROM of cervical spine subjected to compressive loads and received good results. Conclusions Compared with the traditional DIC algorithm, the proposed method can achieve accurate measurement with large ROM for cervical spine tests with different loads, and provide an effective means for assessing the stability and physiological activities of cervical spine.
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Objective To investigate the feasibility of simulating the deformation and displacement of lung tumors by simulating the motion of lung tumors during respiration using finite element method (FEM). Methods The CAD (computer-aided design) surfaces of the lung at multiple inhalation phases were reconstructed from 4D CT images of a patient with lung tumor. The finite element model was established according to the surface at the beginning of inhalation. Distributed surface loads were defined by the differences between each individual surface and the surface at the beginning of inhalation, and applied to the surface of the model. The motion and deformation of lung tumors were then simulated using FEM within the inhalation cycle. Results The numerical simulation indicated that the estimated errors for the lung and the tumor’s motion and deformation were less than 2 mm and 1 mm, respectively. The use of linear elastic relationship for tumor with elastic modulus of 50 kPa could achieve higher precision in simulation. Conclusions The deformation of lung and the displacement of lung tumor are possible to be simulated accurately by FEM. This research provides references for the X-ray free lung tumor tracking method based on numerical simulation.
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Objective To explore the mechanical testing technique suitable for biological materials under water environment. Methods Based on digital image correlation (DIC) method, the unique lens sleeves which can avoid the distortion caused by underwater photography was designed, and this technique was applied to determining mechanical properties of the fish scales. Results The experiment on translation of the water sink indicated that the use of the designed lens sleeves could effectively reduce errors for underwater measurement with high precision; the mechanical testing on fish scales showed that different regions of the fish scales had obviously different mechanical properties, but the differences induced by regions of the dehydrated fish scales were significantly reduced. Conclusions The designed lens sleeves in this study can be applied to image acquisition effectively, and determination of mechanical properties of the biological materials under water environment was achieved using DIC method.
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Researches on mechanical properties of biological hard tissues are of great importance to the prevention and treatment for both bone diseases and oral diseases. Meanwhile, biological materials possess superior mechanical properties due to long-term evolution, and studies on the structure and mechanical properties of these materials can provide useful solutions for the design of engineering materials. However, unlike engineering materials, mechanical studies on biological materials need specific methods to accurately characterize the mechanical performance. This paper summarized the research methods on mechanical properties of biological hard tissues, including routine mechanical tests, fracture mechanics tests, nanoindentation tests, as well as numerical simulation techniques in nano, micro and macro scales.
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Objective To investigate effects of aging on the fracture mechanical behavior of human dentin with finite element numerical method. Methods The finite element model was established according to the typical compact tension specimen in the experiment. The stable crack growth in human dentin was simulated with the cohesive zone model to compare the crack extensions of the young and aged dentin. Results The growth toughness and plateau toughness of the aged dentin were 0.51 and 1.19 MPa•m1/2, respectively, which were significantly lower than those of the young dentin (7.48, 1.71 MPa•m1/2). However, the initiation toughness of the young and aged dentin showed no significant difference with 0.51 and 0.38 MPa•m1/2, respectively. Conclusions The crack growth resistance of human dentin is decreased significantly with aging. Based on the cohesive zone model, the crack growth behavior of biological hard tissue, whose mechanical properties are related with age (such as the human dentin), can be well predicted by using numerical methods.
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Objective To develop a microscopic 3D morphology testing system used for measuring the natural texture of human incisor, and provide practical data for the individualized technique used in dental restoration. Methods Based on microscope and digital image correlation (DIC), a microscopic 3D morphology testing system with its software was developed. The precision of this system was then evaluated, and the characterization of the 3D surface morphology for human incisor was measured by the system. Results Within the field of view (FOV) of 17 mm×12 mm, the accuracy of in plane displacement was estimated as 0.6 μm, while that of out of plane displacement was 5.4 μm. The dimension of horizontal grooves on the labial surface of incisor was determined, where the depth and length for the long groove were 83 μm and 5.28 mm, respectively; the depth and length for the short groove were 40 μm and 4.24 mm, respectively, and the space between the two grooves was 2.85 mm. Conclusions The microscopic 3D morphology testing system is an effective instrument for measuring the surface morphology of human incisors accurately.
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Objective To analyze the compressive strength and fracture mode between four kinds of dental zirconia CAD/CAM ceramic materials by Hertzian contact test. Methods Four CAD/CAM ceramic materials including Cercon smart, Lava, Porcera, and CEREC 3 were selected. Six zirconia sectioned flat specimens were prepared in each group. The critical load and fracture load as well as the fracture mode for each specimen were analyzed with digital image correlation (DIC) technique. Results It was found that cracks were initiated at the middle level of the veneer below the contact zone and propagating along an arc curve into the core/veneer interface, which eventually caused the debonding of the core/veneer layers. For the four ceramic systems, there were no significant differences in the critical load（P＞0.05）, while there were significant differences in the fracture load（P＜0.05）. Conclusions The compressive strength of the four zirconia CAD/CAM ceramic materials could substantially meet the clinic requirement for oral functions regarding the maximum occlusal load. Crack initiation and complete fracture only occurred in the veneer, which indicated that the strength of the veneer should be further reinforced.
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Objective To compare the stresses on the end plate of adjacent lumbar vertebrae between intra-segmental fixation and inter-segmental fixation in treating lumbar spondylolysis by three-dimensional finite element analysis. Method Based on the established finite element model of L4 lumbar spondylolysis, the lumbar internal fixation such as rods and trans-pedicle screws were reconstructed to make the finite element models of intra segmental and inter segmental internal fixation with the same constraint and loading conditions. The stresses on endplate of adjacent lumbar vertebrae of finite element models were measured under three mechanical conditions:spondylolysis, intra-segmental fixation and inter-segmental fixation. Results High stresses were observed under two kinds of internal fixation conditions compared with the spondylolysis condition at the lower endplate of L4 under axial loading(P<0.05). The stresses at the lower endplate of L4 under intra segmental fixation condition were similar as that of the spondylolysis condition under flexion, extension and lateral bending loading. With the same loading, higher stresses were observed under inter-segmental fixation condition compared with the spondylolysis condition, and so did the lower stresses at upper endplate of S1(P<0.05). The lower stresses at the upper endplate of S1 under intra-segmental fixation condition were observed compared with the other two conditions under rotating loading (P<0.05). Conclusions The intra segmental fixation can not only provide stability for lumbar spondylolysis under axial, flexion, extension, lateral bending,but also preserve the normal activity at adjacent disc levels, especially under rotating loading.
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<p><b>OBJECTIVE</b>To investigate the effects of different X-ray doses on the expression of nuclear factor-kappaB (NF-kappaB) P65 in human oral squamous cell carcinoma cell (OSCC) line and the relationship between NF-kappaB P65 and radiation-induced OSCC cell line apoptosis.</p><p><b>METHODS</b>The squamous cell carcinoma of Tca8113 cell was cultivated in the 37 degrees C, 5% CO2 incubator after recovery. The experiment samples were divided into six groups (control group, 2, 4, 6, 8, 10 Gy). After growing to logarithm period, Tca8113 cells were irradiated using above-mentioned X-ray doses. The immunocyteochemistry and Western blot were used to detect the expression of NF-kappaB P65 after irradiation in various times (1, 3, 6, 10, 24, 48 h). The apoptosis rates under different radiotherapy dose were detected by flow cytometer and TDT-mediated dUTP-biotin nick end labeling (TUNEL).</p><p><b>RESULTS</b>Compared with the control group, cytoplasm expression of P65 under different X-ray doses had statistically significant differences (P < 0.05). While the cytoplasm P65 protein expression at different time were compared each other, the 3 h group demonstrated significant difference (P < 0.05). Apoptosis rates in various groups, compared with control group, had statistically significant differences (P < 0.05). While the groups at different time points were compared each other, the apoptosis rates of 3 h group had significant differences (P < 0.05).</p><p><b>CONCLUSION</b>X-ray can activate the NF-kappaB P65 in oral squmaous cell carcinoma cell lines. The correlation between expressional quantity of P65 and radiotherapy induced apoptosis of oral squamous cell carcinoma cell lines possesses positive correlation. The activated and intranuclear P65 may have radiotherapy resistant effect.</p>
Subject(s)
Humans , Apoptosis , Carcinoma, Squamous Cell , Cell Line, Tumor , Mouth Neoplasms , Transcription Factor RelAABSTRACT
Objective The objective of this study is to investigate the effects of the thickness of the adhesives (3M ESPE RelyX ARC) on the internal stress distribution of the IPS Empress II full-ceramic crowns using Finite Element Analysis (FEA). Methods A dummy Empress II ceramic crown restoration of the mandible right first molar was prepared according to standard dental process. Followed by micro-CT scanning, four 3D numerical models with cement thickness 60, 90, 120 and 150μm were established. The models were subjected to four loading conditions and stresses in veneer and core layers were presented. Results Numerical results indicate that when adhesive thickness increases from 60μm to 90μm, the maximum principal stress either in veneer or core decreases. However, when thickness increases to 150μm, stress variation trends differ from adhesives. Conclusion The normal stresses in adhesives remain a low level when the thickness varies from 90μm to 120μm, while the shear stress is less sensitive to the thickness when it exceeds 90μm. There is an optimal thickness which can reduce the tensile stress in the core and veneer. Attention should be paid to the shear strength of the adhesives since the shear stress could cause failure in the adhesive layer.
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Objectives To construct three-dimensional finite element model of lumbar spondylolysis, then to verify its validity by comparison of biomechanics in vitro. Methods According to the radiological data of a patient with lumbar spondylolysis, the bone and intervertebral disc of L4-S1 were reconstructed by Simpleware software. The lumbar attaching ligaments and articular capsule were added into simulating model by Ansys software. Finally, the three-dimensional finite element model of lumbar spondylolysis was simulated successfully, and validated by lumbar spondylolysis biomechanical experiment in vitro. Results The reconstruction of digital model is contained of the bones of lumbar spine which includes of vertebral cortical bone, cancellous bone, facet joint, pedicle, lamina, transverse process and spinous process,as well as annulus fibrosus, nucleus pulposus,superior and inferior end-plates. Besides, anterior and posterior longitudinal ligaments, flavum ligament, supraspinal and interspinal ligaments and articular capsule of facet joint are also attached. The model consisted of 281,261 nodes and 661,150 elements. Imitation of spondylolysis is well done in this model. The validity of the model is verify by comparison of the results of biomechanics in vitro which involved in the trends under loading of stress/strain of L4 inferior facet process, L5 superior and inferior facet process, S1 superior facet process and the trend of stress/strain of lateral and medial L4 inferior facet process. Conclusions Lumbar spondylolysis is reconstructed to three-dimensional model using finite element analysis, and can be further used in the research of biomechanics of lumbar spondylolysis.
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Objective To investigate mechanical properties of the thoracic spine fixed with pedicle screws that were placed using a “funnel technique”. MethodFourteen thoracic spinal segments (T6 to T10) were collected from adult cadavers. These specimens were divided into two groups, 7 in each, and fixed with pedicle screw using funnel and Magerl techniques. The displacement stiffness of the spinal segment and the pull out strength of the pedicle screw were tested for intact and fixed spinal specimens. The displacement stiffness was measured from different loading directions, including axial compression, anterior flexion, posterior extension, lateral bending and axial torsion. ResultsCompared to the intact spine segments, the displacement stiffness is significantly increased (P＜0.05) at all directions in the segments fixed with either funnel or Magerl technique; however, there is no significant difference between the groups fixed with different technique. The screw pull out strength is significantly decreased (P＜0.05) in spine segments fixed with Funnel technique compared to those fixed with Magerl technique. ConclusionsSince funnel technique removed a portion of bone from the posterior side of the vertebral pedicle, it can raise the accuracy and safety for the placement of pedicle screw. Although this technique does not affect the stiffness of fixed spinal segment, it may decrease the anchor strength of pedicle screw. Accordingly, we recommend that the funnel technique can be considered as a complement method for the fixation of vertebral fracture using pedicle screws.
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Objective To investigate the effects of the thickness of the adhesives(3 M ESPE RelyX ARC)on the internal stress distribution of the IPS Empress Ⅱ full-ceramic crowns by using Finite Element Analysis(FEA).Method A dummy Empress Ⅱ ceramic crown restoration of the mandible right first molar was prepared according to standard dental process.Followed by micro-CT scanning,four 3D numerical models with cement thickness 60,90,120 and 150 μm were established respectively.The models were subjected to four loading conditions and stresses in veneer and core layers were presented.Result Numerical results indicate that when adhesive thickness increases from 60 μm to 90 μm,the maximum principal stress either in veneer or core decreases.However,when thickness increases to 150 μm,stress variation trends differ from adhesives.Conclusions The normal stresses in adhesives remain a low level when the thickness varies from 90 μm to 120 μm,while the shear stress is less sensitive to the thickness when it exceeds 90 μm.There is an optimal thickness which can reduce the tensile stress in the core and veneer.Attention should be paid to the shear strength of the adhesives since the shear stress could cause failure in the adhesive layer.
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Objective To construct three-dimensional finite element model of lumbar spondylolysis,then to verify its validity by comparison of biomechanics in vitro.Method According to the radiological data of a patient with lumbar spondylolysis,the bone and intervertebral disc of L4-S1 were reconstructed by Simpleware software.The lumbar attaching ligaments and articular capsule were added into simulating model by Ansys software.The three-dimensional finite element model of lumbar spondylolysis was finally simulated successfully,and validated by lumbar spondylolysis biomechanical experiment in vitro.Results The reconstruction of digital model contained the bones of lumbar spine which include vertebral cortical bone,cancellous bone,facet joint,pedicle,lamina,transverse process and spinous process,as well as the annulus fibrosus,nucleus pulposus,superior and inferior end-plates.Besides,anterior and posterior longitudinal ligaments,flavum ligament,supraspinal and interspinal ligaments and articular capsule of facet joint are also attached.The model consisted of 281,261 nodes and 661,150 elements.Imitation of spondylolysis is well done in this model.The validity of the model was verified by comparison of the results of biomechanics in vitro which involved in the trends under loading of stress/strain of L4 inferior facet process,L5 superior and inferior facet process,S1 superior facet process and the trends of stress/strain of lateral and medial L4 inferior facet process.Conclusions Three-dimensional model of lumbar spondylolysis is reconstructed using finite element analysis,and can be further used in the research in biomechanics of lumbar spondylolysis.