Uwe Wolfram
Research interests
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InterestsBiomechanics, Biomechanical Engineering, Biomaterials, Biomaterial Science, Biomedical
Publications
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Impact of measurement errors on the determination of the linear modulus of human meniscal attachments.
Journal of the mechanical behavior of biomedical materials. 06/2012; 10:120-7.
For the development of meniscal substitutes and related finite element models it is necessary to know the mechanical properties of the meniscus and its attachments. Measurement errors can falsify the determination of material properties. Therefore the impact of metrological and geometrical measureme... [more] For the development of meniscal substitutes and related finite element models it is necessary to know the mechanical properties of the meniscus and its attachments. Measurement errors can falsify the determination of material properties. Therefore the impact of metrological and geometrical measurement errors on the determination of the linear modulus of human meniscal attachments was investigated. After total differentiation the error of the force (+0.10%), attachment deformation (-0.16%), and fibre length (+0.11%) measurements almost annulled each other. The error of the cross-sectional area determination ranged from 0.00%, gathered from histological slides, up to 14.22%, obtained from digital calliper measurements. Hence, total measurement error ranged from +0.05% to -14.17%, predominantly affected by the cross-sectional area determination error. Further investigations revealed that the entire cross-section was significantly larger compared to the load-carrying collagen fibre area. This overestimation of the cross-section area led to an underestimation of the linear modulus of up to -36.7%. Additionally, the cross-sections of the collagen-fibre area of the attachments significantly varied up to +90% along their longitudinal axis. The resultant ratio between the collagen fibre area and the histologically determined cross-sectional area ranged between 0.61 for the posterolateral and 0.69 for the posteromedial ligament. The linear modulus of human meniscal attachments can be significantly underestimated due to the use of different methods and locations of cross-sectional area determination. Hence, it is suggested to assess the load carrying collagen fibre area histologically, or, alternatively, to use the correction factors proposed in this study.
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2.13Impact points
Internal morphology of human facet joints: comparing cervical and lumbar spine with regard to age, gender and the vertebral core.
Journal of anatomy. 03/2012; 220(3):233-41.
Back pain constitutes a major problem in modern societies. Facet joints are increasingly recognised as a source of such pain. Knowledge about the internal morphology and its changes with age may make it possible to include the facets more in therapeutic strategies, for instance joint replacements or... [more] Back pain constitutes a major problem in modern societies. Facet joints are increasingly recognised as a source of such pain. Knowledge about the internal morphology and its changes with age may make it possible to include the facets more in therapeutic strategies, for instance joint replacements or immobilisation. In total, 168 facets from C6/7 and L4/5 segments were scanned in a micro-computed tomography. Image analysis was used to investigate the internal morphology with regard to donor age and gender. Additional data from trabecular bone of the vertebral core allowed a semi-quantitative comparison of the morphology of the vertebral core and the facets. Porosity and pore spacing of the cortical sub-chondral bone does not appear to change with age for either males or females. In contrast, bone volume fraction decreases in females from approximately 0.4 to 0.2 , whereas it is constant in males. Trabecular thickness decreases during the ageing process in females and stays constant in males , whereas trabecular separation increases during the ageing process in both genders. The results of this study may help to improve the understanding of pathophysiological changes in the facet joints. Such results could be of value for understanding back pain and its treatment.
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3.10Impact points
High-resolution ZTE imaging of human teeth.
NMR in biomedicine. 01/2012;
MRI with zero echo time (ZTE) is achieved by 3D radial centre-out encoding and hard-pulse RF excitation while the projection gradient is already on. Targeting short-T(2) samples, the efficient, robust and silent ZTE approach was implemented for high-bandwidth high-resolution imaging requiring partic... [more] MRI with zero echo time (ZTE) is achieved by 3D radial centre-out encoding and hard-pulse RF excitation while the projection gradient is already on. Targeting short-T(2) samples, the efficient, robust and silent ZTE approach was implemented for high-bandwidth high-resolution imaging requiring particularly rapid transmit-receive switching and algebraic image reconstruction. The ZTE technique was applied to image extracted human teeth at 11.7T field strength, yielding detailed depictions with very good delineation of the mineralised dentine and enamel layers. ZTE results are compared with UTE (ultra-short echo time) MRI and micro-computed tomography (μCT), revealing significant differences in SNR and CNR yields. Compared to μCT, ZTE MRI appears to be less susceptible to artefacts caused by dental fillings and to offer superior sensitivity for the detection of early demineralisation and caries lesions. Copyright © 2012 John Wiley & Sons, Ltd.
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3.61Impact points
Effect of Subchondral Drilling on the Microarchitecture of Subchondral Bone: Analysis in a Large Animal Model at 6 Months.
The American journal of sports medicine. 01/2012;
BACKGROUND: Marrow stimulation techniques such as subchondral drilling are clinically important treatment options for symptomatic small cartilage defects. Little is known about whether they induce deleterious changes in the subchondral bone. HYPOTHESIS: Subchondral drilling induces substantial alter... [more] BACKGROUND: Marrow stimulation techniques such as subchondral drilling are clinically important treatment options for symptomatic small cartilage defects. Little is known about whether they induce deleterious changes in the subchondral bone. HYPOTHESIS: Subchondral drilling induces substantial alterations of the microarchitecture of the subchondral bone that persist for a clinically relevant postoperative period in a preclinical large animal model. STUDY DESIGN: Controlled laboratory study. METHODS: Standardized full-thickness chondral defects in the medial femoral condyles of 19 sheep were treated by subchondral drilling. Six months postoperatively, the formation of cysts and intralesional osteophytes was evaluated. A standardized methodology was developed to segment the ovine subchondral unit into reproducible volumes of interest (VOIs). Indices of bone structure were determined by micro-computed tomography (micro-CT). RESULTS: Analysis of the microarchitecture revealed the absence of zonal stratification in the ovine subarticular spongiosa, permitting an unimpeded and simultaneous analysis of the entire subchondral trabecular network. Subchondral drilling led to the formation of subchondral bone cysts (63%) and intralesional osteophytes (26%). Compared with the adjacent unaffected subchondral bone, drilling induced significant alterations in nearly all parameters for the microarchitecture of the subchondral bone plate and the subarticular spongiosa, most importantly in bone volume, bone surface/volume ratio, trabecular thickness, separation, pattern factor, and bone mineral density (BMD) (all P ≤ .01). CONCLUSION: The data show that the ovine subchondral bone can be reliably evaluated using micro-CT with standardized VOIs. We report that subchondral drilling deteriorates the microarchitecture both of the subchondral bone plate and subarticular spongiosa and decreases BMD. These results suggest that the entire osteochondral unit is altered after drilling for an extended postoperative period. CLINICAL RELEVANCE: The subchondral bone remains fragile after subchondral drilling for longer durations than previously expected. Further evaluations of structural subchondral bone parameters of patients undergoing marrow stimulation are warranted.
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1.61Impact points
Autofluorescence imaging, an excellent tool for comparative morphology.
Journal of microscopy. 08/2011; 244(3):259-72.
Here we present a set of methods for documenting (exo-)morphology by applying autofluorescence imaging. For arthropods, but also for other taxa, autofluorescence imaging combined with composite imaging is a fast documentation method with high-resolution capacities. Compared to conventional micro- an... [more] Here we present a set of methods for documenting (exo-)morphology by applying autofluorescence imaging. For arthropods, but also for other taxa, autofluorescence imaging combined with composite imaging is a fast documentation method with high-resolution capacities. Compared to conventional micro- and macrophotography, the illumination is much more homogenous, and structures are often better contrasted. Applying different wavelengths to the same object can additionally be used to enhance distinct structures. Autofluorescence imaging can be applied to dried and embedded specimens, but also directly on specimens within their storage liquid. This has an enormous potential for the documentation of rare specimens and especially type specimens without the need of preparation. Also for various fossils, autofluorescence can be used to enhance the contrast between the fossil and the matrix significantly, making even smallest details visible. 'Life-colour' fluorescence especially is identified as a technique with great potential. It provides additional information for which otherwise more complex methods would have to be applied. The complete range of differences and variations between fluorescence macrophotography and different types of fluorescence microscopy techniques are here explored and evaluated in detail. Also future improvements are suggested. In summary, autofluorescence imaging is a powerful, easy and fast-to-apply tool for morphological studies.
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3.98Impact points
In vivo degradation of low temperature calcium and magnesium phosphate ceramics in a heterotopic model.
Acta biomaterialia. 05/2011; 7(9):3469-75.
Bone replacement using synthetic and degradable materials is desirable in various clinical conditions. Most applied commercial materials are based on hydroxyapatite, which is not chemically degradable under physiological conditions. Here we report the effect of a long-term intramuscular implantation... [more] Bone replacement using synthetic and degradable materials is desirable in various clinical conditions. Most applied commercial materials are based on hydroxyapatite, which is not chemically degradable under physiological conditions. Here we report the effect of a long-term intramuscular implantation regime on the dissolution of various low temperature calcium and magnesium phosphate ceramics in vivo. The specimens were analysed by consecutive radiographs, micro-computed tomography scans, compressive strength testing, scanning electron microscopy and X-ray diffractometry. After 15months in vivo, the investigated materials brushite (CaHPO(4)·2H(2)O), newberyite (MgHPO(4)·3H(2)O), struvite (MgNH(4)PO(4)·6H(2)O) and hydroxyapatite (Ca(9)(PO(4))(5)HPO(4)OH) showed significant differences regarding changes of their characteristics. Struvite presented the highest loss of mechanical performance (95%), followed by newberyite (67%) and brushite (41%). This was accompanied by both a distinct extent of cement dissolution as well as changes of the phase composition of the retrieved cement implants. While the secondary phosphate phases (brushite, newberyite, struvite) completely dissolved, re-precipitates of whitlockite and octacalcium phosphate were formed in either particulate or whisker-like morphology. Furthermore, for the first time the possibility of a macropore-free volume degradation mechanism of bioceramics was demonstrated.
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2.66Impact points
Damage accumulation in vertebral trabecular bone depends on loading mode and direction.
Journal of biomechanics. 02/2011; 44(6):1164-9.
Osteoporotic vertebral fractures constitute a major clinical problem in ageing societies. A third of all vertebral fractures is caused by falls, 15% by lifting heavy loads or traffic accidents and over 50% are not relatable to a traumatic event. In the latter case vertebrae show sinter processes whi... [more] Osteoporotic vertebral fractures constitute a major clinical problem in ageing societies. A third of all vertebral fractures is caused by falls, 15% by lifting heavy loads or traffic accidents and over 50% are not relatable to a traumatic event. In the latter case vertebrae show sinter processes which indicate the accumulation of damage and permanent deformation. Accumulated damage may not be visible on radiographs but increases the risk of fracture and could lead to vertebral collapse. Clear understanding of the accumulation of damage and residual strains and their dependence on loading mode and direction is important for understanding vertebral fractures. Altogether, 251 cylindrical samples (8×18-25mm) were obtained from 50 male and 54 female fresh frozen human vertebrae (T1-L3) of 65 (21-94) years. Vertebrae were randomly assigned to three groups cranial-caudal, anterior-posterior and latero-lateral. Specimens were mechanically loaded in compression, tension or torsion in five load steps at a strain rate of 0.2%/s. Three conditioning cycles were driven per load step. Stress-strain curves were reconstructed from the force-displacement or from the moment-twist angle curves. Damage accumulated from 0 to 86% in compression, from 0 to 76% in tension and from 0 to 86% in torsion through the five load steps. Residual strains accumulated from 0 to -0.008mm/mm in compression, 0 to 0.006mm/mm in tension and 0 to 0.026rad/rad in torsion. Significantly less damage (p<0.05) but not residual strains accumulated in transverse directions. This study provides detailed experimental insights into the damage behaviour of vertebral trabecular bone under various loads occurring in vivo. Damage but not residual strain evolution seems to be anisotropic. Both seem to evolve differently under different loading modes. The results could be of importance in understanding vertebral fractures.
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Freies Tool zur Steifigkeitsberechnung knöcherner Strukturen aus klinischen Bilddaten – Entwicklung, Validierung und Erprobung von FEA4DICOM
Proceedings of ACUM 2010, Aachen; 11/2010
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2.66Impact points
Internal forces and moments in the femur of the rat during gait.
Journal of biomechanics. 09/2010; 43(13):2473-9.
The rat is of increasing importance for experimental studies on fracture healing. The healing outcome of long bone fractures is strongly influenced by mechanical factors, such as the interfragmentary movement. This movement depends on the stability of the fracture fixation and the musculoskeletal lo... [more] The rat is of increasing importance for experimental studies on fracture healing. The healing outcome of long bone fractures is strongly influenced by mechanical factors, such as the interfragmentary movement. This movement depends on the stability of the fracture fixation and the musculoskeletal loads. However, little is known about these loads in rats. The musculoskeletal loads during gait were estimated using an inverse-dynamic musculoskeletal model of the right hindlimb of the rat. This model was based on a micro-CT scan of the lower extremities and an anatomical study using 15 rat cadavers. Kinematics were reconstructed from X-ray movies, taken simultaneously from two perpendicular directions during a gait cycle. The ground reaction forces were taken from the literature. The muscle forces were calculated using an optimization procedure. The internal forces and moments varied over the gait cycle and along the femoral axis. The greatest internal force (up to 7 times bodyweight) acted in the longitudinal direction. The greatest internal moment (up to 13.8 bodyweight times millimeter) acted in the sagittal plane of the femur. The validity of the model was corroborated by comparing the estimated strains caused by the calculated loads on the surface of the femoral mid-shaft with those from the literature. Knowledge of the internal loads in the femur of the rat allows adjustment of the biomechanical properties of fixation devices in fracture healing studies to the desired interfragmentary movement.
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2.66Impact points
Valid micro finite element models of vertebral trabecular bone can be obtained using tissue properties measured with nanoindentation under wet conditions.
Journal of biomechanics. 03/2010; 43(9):1731-7.
Osteoporosis-related vertebral fractures represent a major public health problem. Anatomy-specific CT-based finite element (FE) simulations could help in identifying which vertebrae have the highest risk of fracture and thus help to decide upon the need for vertebroplasty or other surgical intervent... [more] Osteoporosis-related vertebral fractures represent a major public health problem. Anatomy-specific CT-based finite element (FE) simulations could help in identifying which vertebrae have the highest risk of fracture and thus help to decide upon the need for vertebroplasty or other surgical intervention. Continuum level FE simulations require effective macroscopic material properties of the vertebra. Micro finite element (microFE) models can be used to circumvent the difficult experiments that are necessary to determine these effective properties. From a quantitative point of view, these microFE models depend critically on the chosen trabecular tissue properties. The question remains whether linear elastic microFE models of vertebral trabecular bone with and without specimen-specific tissue properties yield similar results as non-destructive macroscopic experiments under moist conditions. microFE models were set up from microCT scans with specimen-specific or average tissue moduli measured by nanoindentation under dry and wet testing conditions. Non-destructive macroscopic mechanical compression, tension and torsion tests were performed. Experimentally obtained and simulated apparent stiffnesses were compared. No significant difference was found when comparing microFE simulations with wet tissue properties and experiments for tension, compression and torsion (p>0.05). Concordance correlation coefficients were high for tension and compression (r(c)(wet)>or=0.96,p<0.05) but moderate for torsion (r(c)(wet)=0.81,p<0.05). The agreement between simulation and experiment was confirmed by Bland-Altman plots which showed mean differences <or=10MPa. Surprisingly, the agreement between simulation and experiment was not reduced by using an average tissue modulus. The results indicate that valid microFE models can be set up using average tissue properties obtained under wet indentation conditions.
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4.09Impact points
Rehydration of Vertebral Trabecular Bone: Inuences on its Anisotropy, its Stiffness and the Indentation Work with a View to Age, Gender and Vertebral Level.
Bone. 10/2009;
For understanding the fracture risk of vertebral bodies the macroscopic mechanical properties of the cancellous core are of major interest. Due to the hierarchical nature of bone, these depend in turn on the micromechanical properties of bone extra cellular matrix which is at least linear elastic tr... [more] For understanding the fracture risk of vertebral bodies the macroscopic mechanical properties of the cancellous core are of major interest. Due to the hierarchical nature of bone, these depend in turn on the micromechanical properties of bone extra cellular matrix which is at least linear elastic transverse isotropic. The experimental determination of local elastic properties of bone ex vivo necessitates a high spatial resolution which can be provided by depth-sensing indentation techniques. Using microindentation, this study investigated the effects of rehydration on the transverse isotropic elastic properties of vertebral trabecular bone matrix obtained from two orthogonal directions with a view to microanatomical location, age, gender, vertebral level and anatomic direction in a conjoint statistics. Biopsies were gained from 104 human vertebrae (T1 - L3) with a median age of 65 (21 - 94) years. Wet elastic moduli were 29% lower (p<0.05) than dry elastic moduli. For wet indentation the ratio of mean elastic moduli tested in axial to those tested in transverse indentation direction were 1.13 to 1.23 times higher than for dry indentation. The ratio of elastic moduli tested in the core to those tested in the periphery of trabeculae was 1.05 to 1.16 times higher when testing wet. Age and gender did not show any influence on the elastic moduli for wet and dry measurements. The correlation between vertebral level and elastic moduli became weaker after rehydration (p(wet) < 0.09 , r(2)(wet) = 0.14), and (p(dry) < 0.01 , r(2)(dry) = 0.38). Elastic and dissipated energies were similarly affected by rehydration compared to the elastic modulus. No significant difference in the energies could be found for gender (p<0.05). Significant differences in the energies were found for age (p<0.05) after rehydration. Qualitative and quantitative insights into the transverse isotropic elastic properties of trabecular bone matrix under two testing conditions over a broad spectrum of vertebrae could be given. This study could help to further improve understanding of the mechanical properties of vertebral trabecular bone.
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2.66Impact points
Statistical osteoporosis models using composite finite elements: A parameter study.
Journal of biomechanics. 08/2009;
Osteoporosis is a widely spread disease with severe consequences for patients and high costs for health care systems. The disease is characterised by a loss of bone mass which induces a loss of mechanical performance and structural integrity. It was found that transverse trabeculae are thinned and p... [more] Osteoporosis is a widely spread disease with severe consequences for patients and high costs for health care systems. The disease is characterised by a loss of bone mass which induces a loss of mechanical performance and structural integrity. It was found that transverse trabeculae are thinned and perforated while vertical trabeculae stay intact. For understanding these phenomena and the mechanisms leading to fractures of trabecular bone due to osteoporosis, numerous researchers employ micro-finite element models. To avoid disadvantages in setting up classical finite element models, composite finite elements (CFE) can be used. The aim of the study is to test the potential of CFE. For that, a parameter study on numerical lattice samples with statistically simulated, simplified osteoporosis is performed. These samples are subjected to compression and shear loading. Results show that the biggest drop of compressive stiffness is reached for transverse isotropic structures losing 32% of the trabeculae (minus 89.8% stiffness). The biggest drop in shear stiffness is found for an isotropic structure also losing 32% of the trabeculae (minus 67.3% stiffness). The study indicates that losing trabeculae leads to a worse drop of macroscopic stiffness than thinning of trabeculae. The results further demonstrate the advantages of CFEs for simulating micro-structured samples.
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2.88Impact points
A downloadable meshed human canine tooth model with PDL and bone for finite element simulations.
Dental materials : official publication of the Academy of Dental Materials. 07/2009;
OBJECTIVE: The aim of this study is to relieve scientists from the complex and time-consuming task of model generation by providing a model of a canine tooth and its periradicular tissues for Finite Element Method (FEM) simulations. METHODS: This was achieved with diverse commercial software, based ... [more] OBJECTIVE: The aim of this study is to relieve scientists from the complex and time-consuming task of model generation by providing a model of a canine tooth and its periradicular tissues for Finite Element Method (FEM) simulations. METHODS: This was achieved with diverse commercial software, based on a micro-computed tomography of the specimen. RESULTS: The Finite Element (FE) Model consists of enamel, dentin, nerve (innervation), periodontal ligament (PDL), and the surrounding cortical bone with trabecular structure. The area and volume meshes are of a very high quality in order to represent the model in a detailed form. Material properties are to be set individually by every user. The tooth model is provided for Abaqus((R)), Ansys((R)), HyperMesh((R)), Nastran((R)) and as STL files, in an ASCII format for free download. SIGNIFICANCE: This can help reduce the cost and effort of generating a tooth model for some research institutions, and may encourage other research groups to provide their high quality models for other researchers. By providing FE models, research results, especially FEM simulations, could be easily verified by others.
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2.66Impact points
Vertebral trabecular main direction can be determined from clinical CT datasets using the gradient structure tensor and not the inertia tensor-A case study.
Journal of biomechanics. 06/2009;
Osteoporosis is a wide spread disease with one-third of all women beyond their menopause and a fifth of men above the age of 50 years suffering from it. Patient specific finite element models would be a great improvement for the diagnosis of vertebral fracture risk. Different material models have be... [more] Osteoporosis is a wide spread disease with one-third of all women beyond their menopause and a fifth of men above the age of 50 years suffering from it. Patient specific finite element models would be a great improvement for the diagnosis of vertebral fracture risk. Different material models have been proposed, which incorporate information about the anisotropy of trabecular bone in addition to bone mineral density (BMD) using a second rank structure tensor. Two alternative structure measurement methods, gradient structure tensor (GST) and inertia tensor (IT), were investigated. Structure was determined from in situ scans. This was compared to structure computed with the mean intercept length (MIL) tensor from muCT scans at the same locations. GST delivered information comparable to MIL regarding the structural main direction even at normal dose standard clinical settings (median of the scalar products of up to approximately 0.98). IT was not comparable to MIL (median approximately 0.4). Neither of the alternatives could determine eigenvalues comparable to these determined from MIL (p>0.5). In conclusion, this study could show that the measurement of the structural main direction is possible for in situ scans in a clinical setting. It was shown that the method of choice to determine trabecular main direction in situ is GST. Knowing the main direction a transverse isotropic fabric tensor can be constructed.
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1.14Impact points
Correspondences of hydrostatic pressure in periodontal ligament with regions of root resorption: A clinical and a finite element study of the same human teeth.
Computer methods and programs in biomedicine. 11/2008;
INTRODUCTION: The main objectives of this study were to generate individual finite element models of extracted human upper first premolars, and to simulate the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models for evaluation of the risk of root resorption. ME... [more] INTRODUCTION: The main objectives of this study were to generate individual finite element models of extracted human upper first premolars, and to simulate the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models for evaluation of the risk of root resorption. METHODS: The individual extracted teeth were from a previous in vivo study that investigated root resorption after application of continuous intrusive forces. The results of experimental examination and simulations were compared on these identical tooth roots. The applied force system was 0.5N and 1.0N of intrusive force. RESULTS: The simulated results during intrusion of 0.5N showed regions near the apical thirds of the roots with hydrostatic pressure over the human capillary blood pressure. These regions correlated with the electron microscopies of previous studies performed in Brazil with the identical teeth. An increased force of 1.0N resulted in increased areas and magnitudes of the hydrostatic pressure. CONCLUSIONS: The key parameter indicating beginning root resorption used in this study was an increased value for hydrostatic pressure in the PDL.
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2.66Impact points
A method to obtain surface strains of soft tissues using a laser scanning device.
Journal of biomechanics. 07/2008;
A three-dimensional laser scanning device was developed allowing surface digitization of musculoskeletal and soft tissue structures under different loads. Image-processing algorithms were formulated for image registration. These were used to determine displacement mapping and then surface strains. V... [more] A three-dimensional laser scanning device was developed allowing surface digitization of musculoskeletal and soft tissue structures under different loads. Image-processing algorithms were formulated for image registration. These were used to determine displacement mapping and then surface strains. Various validation experiments were performed. Accuracy was obtained on a test cylinder after rigid rotation and on a silicon cylinder compressed in four loading steps. The system accuracy (including the scanning and the data evaluation) was +/-0.10% strain in vertical and +/-0.16% strain in shear and circumferential direction for the rigid rotation exhibiting the zero-strain situation. Silicon cylinder compression showed that the accuracy was best for small strains, whereas strains >5% evoked a slight underestimation increasing further with higher strains (error of 0.54% for 7.22% vertical strain). It was possible to increase the accuracy by performing the strain measurements via sub-steps. This had a remaining error of 0.41% for 7.22% vertical strain. A further experiment was carried out in order to acquire the surface strain of a human lumbar intervertebral disc while it was forced to flexion and extension. This study introduced a laser-based scanning method to obtain soft tissue surface strains. It is important to know the strain distribution of musculoskeletal structures and soft tissues. This could help to better understand the mechanical loading of biological structures e.g. the processes in fracture healing. These data could also be used to assist in the validation process for finite-element models.
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0.94Impact points
Periodontal ligament hydrostatic pressure with areas of root resorption after application of a continuous torque moment.
The Angle orthodontist. 07/2007; 77(4):653-9.
OBJECTIVE: To evaluate the risk of root resorption, individual finite element models (FEMs) of extracted human maxillary first premolars were created, and the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models was simulated. MATERIALS AND METHODS: A continuous... [more] OBJECTIVE: To evaluate the risk of root resorption, individual finite element models (FEMs) of extracted human maxillary first premolars were created, and the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models was simulated. MATERIALS AND METHODS: A continuous lingual torque of 3 Nmm and 6 Nmm respectively was applied in vivo to the aforementioned teeth. After extraction, FEMs of these double-rooted teeth were created based on high-resolution microcomputed tomographics (micro CT, voxel size: 35 microns). This high volumetric resolution made the recognition of very small resorption lacunae possible. Scanning electron micrographs of the root surfaces were created as well. This enabled the investigation of advantages and disadvantages of the different imaging techniques from the viewpoint of the examination of root resorption. Using the FEMs, the same loading conditions as applied in vivo were simulated. RESULTS: The results of clinical examination and simulations were compared using the identical roots of the teeth. The regions that showed increased hydrostatic pressure (>0.0047 MPa) correlated well with the locations of root resorption for each tooth. Increased torque resulted in increased high-pressure areas and increased magnitudes of hydrostatic pressure, correlating with the experiments. CONCLUSION: If hydrostatic pressure exceeds typical human capillary blood pressure in the PDL, the risk of root resorption increases.
Following (11)
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Frank Niemeyer
Universität Ulm -
Philippe Zysset
Universität Bern -
Dieter Pahr
Technische Universität Wien -
Enrico Dall'Ara
Technische Universität Wien -
Stefan Liebau
Universität Ulm
Topics (6)
