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PubMed2005

Finite element analysis in functional morphology.

This article reviews the fundamental principles of the finite element method and the three basic steps (model creation, solution, and validation and interpretation) involved in using it to examine structural mechanics. Validation is a critical step in the analysis, without which researchers cannot evaluate the extent to which the model represents or is relevant to the real biological condition. We discuss the method's considerable potential as a tool to test biomechanical hypotheses, and major hurdles involved in doing so reliably, from the perspective of researchers interested in functional morphology and paleontology. We conclude with a case study to illustrate how researchers deal with many of the factors and assumptions involved in finite element analysis.

Anatomy↗

PubMed2003

Finite element analysis of stresses in molars during clenching and mastication.

STATEMENT OF PROBLEM: During physiological functions of the masticatory system such as swallowing and chewing, teeth are subjected to variations in force application. Most in vitro analyses of stress have not analyzed the combined forces acting on teeth. PURPOSE: The purpose of this study was to analyze the stresses induced in a mandibular molar during clenching and chewing of morsels with various elastic moduli. MATERIALS AND METHODS: The investigation was performed by means of finite element analysis with the use of contact elements. Two-dimensional models of the mandibular first molar and the crown of the opposing maxillary molar were created. The computerized simulation evaluated the clenching and chewing of 4 morsels with different elastic moduli (similar to hard gum, tough meat, bone, and combination of hard gum and bone). The movement of the studied teeth was simulated in the frontal plane. Teeth models crushed morsels and closed into the maximal intercuspation position. The values of stresses in the mandibular molar were calculated during these situations. RESULTS: The study revealed that clenching of molars and chewing morsels of high elastic moduli resulted in maximal equivalent stresses within occlusal enamel. During mastication of morsels of low elastic moduli the stress concentration was located in the cervical region of the lingual side of the mandibular molar. Masticating a low-elasticity morsel containing a fragment of bone caused the highest equivalent stresses in the lingual wall and high tensile stresses in enamel near the central intercuspal fissure of the tooth studied. CONCLUSION: During mastication of various morsels, maximal equivalent stresses occurred in occlusal enamel and in the cervical region of the lingual wall of the first mandibular molar. The more unfavorable and highest stresses were exerted during mastication of nonhomogeneous morsels.

Bite Force↗

PubMed1992

Finite element analysis of interface geometry effects on the crestal bone surrounding a dental implant.

Using a two-dimensional axisymmetric finite element analysis technique, different geometrical configurations of implants, abutments, and interfaces have been investigated to alter the stress distribution in the crestal bone region. The crestal bone region is of particular interest due to observations of progressive bone resorption (saucerization). The ability of a prosthetic restoration-implant construct to transfer an appropriate stress at this region will, by definition of Wolff's law (bone's response to strain) and principles of bone remodeling, help to maintain the integrity of the surrounding bone via force transfer. The two geometries investigated involved a traditional flat mating surface and a slanted (oblique) mating surface. In both models a vertical load of 400 N (63 N/rad across 2 pi radians) was applied to the abutment apex. In the crestal bone region the oblique mating surface increased the transfer of horizontal stress 67 percent over the traditional flat mating surface design. The magnitude of stress transferred and the area which it was transferred across was increased in this region. Results indicate potentially more favorable mechanical conditions for bone maintenance surrounding an endosseous dental implant may be achieved if force is transferred preferentially via circumferential grooves and an oblique (dished) implant-abutment mating surface. These theoretical results are consistent with basic principles of stress transfer, stress shielding, and remodeling as well as clinical observations of bone maintenance and resorption.

Alveolar Bone Loss↗

PubMed2004

Rigid design of fast scanning probe microscopes using finite element analysis.

To improve the performance of atomic force microscopes regarding speed and noise sensitivity, it is important to consider the mechanical rigidity of the actuator (scanner), and the overall mechanical structure. Using finite element analysis in the design process, it was possible to increase the first resonance frequency from 950 Hz for the whole system to 23.4 kHz for the whole system. This constitutes a factor of approximately 25 in resonance frequency and a factor of 625 in stiffness and, hence, noise immunity.

Electronics↗

PubMed2005

Finite element analysis model to simulate the behavior of luting cements during setting.

OBJECTIVES: Besides the fixation of the restoration, an important function of dental luting cements is to seal the gap between tooth and restoration. However, as a result of adhesion, curing contraction is hindered, creating stresses. To maintain the seal these stresses neither exceed the bond nor the cohesive strength of the cement. The aim of this study was to evaluate a rather simple model, which mimics the setting behavior of luting cements based on the division of the setting process into a liquid, visco-elastic and elastic phase, for its suitability to predict in Finite Element Analysis (FEA) the magnitude of the setting stresses occurring clinically. METHODS: Commercial luting cement, RelyX ARC, was used in this study. In a dynamic test set-up the stresses, the elastic strain, and the shrinkage were determined. Two layers with different thicknesses and different ratios between bonded and free surface (C-factor) were examined. The parameters were used in three-dimensional FEA models. The experimental contraction stresses were compared with the results of the FEA. RESULTS: In cement layers with uniform layer thickness, it is possible to predict the contraction stresses with the found parameters. The smallest plastic deformations and contraction stresses were found in the thinnest layer. The studied model was reliable in predicting the experimental stresses. SIGNIFICANCE: The results of this study may be used for the prediction using FEA of the actual stresses occurring in dental restorations.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2006

Non-linear finite element analysis of the failure progression of fiber-reinforced ceramics produced by tape casting technique.

The purpose of this study was to investigate the failure progression process of fiber-reinforced ceramic by finite element (FE) analysis. The three-dimensional FE model for three-point bending simulation was 40 mm long, 4 mm wide, 3 mm thick, and with a span length of 30 mm. Nodal force with load increment of 20 N was applied at the center of the upper surface of the beam. To evaluate matrix fracture and fiber fracture, von Mises criterion and Tsai-Hill criterion were used respectively. Consequently, the stress-deflection curve obtained from FE simulation agreed with that obtained from the experimental testing. Differences in flexural strength and modulus between the analytical and experimental results were 1.3 and -2.9% respectively--demonstrating a close agreement between both results. In conclusion, the FE model applied in the present study was shown to be valid for predicting the failure progression of fiber-reinforced ceramics.

Aluminum Oxide↗

PubMed1998

Finite element analysis of non-axial versus axial loading of oral implants in the mandible of the dog.

The influence of axial and non-axial occlusal loads on the bone remodelling phenomena around oral implants in an animal experiment is simulated in a finite element analysis. The axial and non-axial loading conditions were introduced by inserting a bilaterally supported fixed partial prosthesis and a cantilever fixed partial prosthesis on two IMZ implants in the mandible of beagle dogs. Earlier quantitative and qualitative histological analyses revealed a statistically significant different remodelling response between both loading conditions. Two-dimensional and three-dimensional models are built to analyse and compare von Mises equivalent stress, maximum principal stress, maximum principal strain and strain energy density distributions, first around a free-standing implant and subsequently around the implants of the two prosthesis designs under the respective resultant in vivo loads. Strong correlations between the calculated stress distributions in the surrounding bone tissue and the remodelling phenomena in the comparative animal model are observed. It is concluded that the highest bone remodelling events coincide with the regions of highest equivalent stress and that the major remodelling differences between axial and non-axial loading are largely determined by the horizontal stress component of the engendered stresses.

Alveolar Process↗

PubMed2006

Biomechanical modeling and design optimization of cartilage myringoplasty using finite element analysis.

The purpose of this study was to determine the acoustic transfer characteristics of cartilage for optimal cartilage myringoplasty. In order to do so, we developed a cartilage plate/tympanic membrane-coupled model using finite element analysis. Cartilage specimens of the tragus were obtained from fresh human cadavers, and the parameters of the tragus were determined by curve fitting and cross-calibration. A cartilage plate was used to repair an eardrum perforation, and the new coupled tympanic membrane-cartilage complex was loaded into our 3-dimensional biomechanical model of the middle ear for analysis. Our results show that first the beta-damping value of the cartilage plate depends on frequency. The value of beta damping was close to 3 x 10(-4) s at lower frequencies and 5 x 10(-6) s at higher frequencies. Secondly, reducing cartilage thickness leads to an improvement of its acoustic transfer qualities. From an acoustics point of view, the 0.1- to 0.2-mm cartilage plate seems to be most preferable with regard to tympanic membrane vibration. Furthermore, thicknesses of 0.2 mm at lower frequencies and 0.1 mm at higher frequencies were regarded as good compromises between sufficient mechanical stability and low acoustic transfer loss.

Biomechanical Phenomena↗

PubMed2002

[Finite element analysis of lumbar facet joint contact model].

OBJECTIVE: To establish a finite element model of the fourth and fifth lumber segments in order to analyze the biomechanical characteristics of facet joints under different pressure loads. METHODS: CT sectional images of L(4-5) segments were obtained to construct a finite element model, adopting contact model to simulate the condition the superior and inferior facets were in. RESULTS: The facet joint exhibited different performances under different conditions, and more loads was forced on it when the model was twirled. CONCLUSION: The facet joints should be simulated as in condition of contact to help correct understanding of the biomechanical characteristics of the spinal segment.

Biomechanical Phenomena↗

PubMed1983

A survey of finite element analysis in orthopedic biomechanics: the first decade.

The finite element method (FEM), an advanced computer technique of structural stress analysis developed in engineering mechanics, was introduced to orthopedic biomechanics in 1972 to evaluate stresses in human bones. Since then, this method has been applied with increasing frequency for stress analyses of bone and bone-prosthesis structures, fracture fixation devices and various kinds of tissues other than bone. The aims of these investigations were to assess relationship between load carrying functions and morphology of the tissues, and to optimize designs and fixation techniques of implants. Although the amounts of significant findings and useful concepts generated by the FEM during the first decade of its application in this field were limited, many publications have served to illustrate its capabilities and limitations. The method is now well established as a tool for basic research and for design analysis in orthopedic biomechanics, and the number of publications in which it is used is increasing rapidly. In the meantime, following developments in engineering mechanics, the capabilities of the method are augmented which, together with an increasing sophistication of computers, guarantees exciting possibilities for the future. However, the biological structures and the clinical problems concerned are complex. Scientific progress in this area requires a sound understanding of engineering mechanics on the one hand, and a profound appreciation of the complex reality on the other. These features were not always apparent in the FEM work reported during the first ten years. In the following survey, the developments of FEM applications in orthopedic biomechanics during the first decade are discussed. Special problem areas are indicated and future trends anticipated.

Biomechanical Phenomena↗

PubMed2006

Loading of bone surrounding implants through three-unit fixed partial denture fixation: a finite-element analysis based on in vitro and in vivo strain measurements.

Implant-borne fixed partial dentures (FPDs), whether cementable or screwable superstructures, ought to display a true passive fit. The objective of this in vivo-based finite-element analysis is, therefore, to quantify the degree of stress which occurs in the bone around the implants as a result of the fixation of cemented and screw-retained FPDs. On the basis of a simulated patient situation with two implants, six groups of implant-supported superstructures containing 10 samples each were fabricated. Strain gauges which were mounted on the pontics of the restorations were subsequently used to take in vivo measurements (Ethics Commission Approval No. 2315). Taking the values obtained as a basis, the von Mises equivalent stress was chosen to illustrate bone loading in three-dimensional finite-element models. Superstructure fixation caused residual interface stress as high as 30 MPa. Similar stress magnitudes can be observed for axial implant loading of 200 N. Assuming that the axial loading of a single implant with 200 N is within the bone's physiological range, it can be concluded that the degree of stress resulting from the fixation of superstructures alone does not constitute a risk.

Cementation↗

PubMed2005

Effects of different inter-implant distances on the stress distribution around endosseous implants in posterior mandible: a 3D finite element analysis.

PURPOSE: The aim of this study was to evaluate the effects of different inter-implant distances on stress distribution in the bone around the endosseous titanium implants under vertical, oblique and horizontal loads in the posterior mandibular edentulousim by finite element analysis (3D FEA). MATERIALS AND METHODS: 3D FEA models representing mandible and ITI implant (Straumann, Waldenburg, Switzerland) were simulated. The distances in-between the units were set at 0.5, 1.0 and 2.0 cm. Vertical (V) 70 degrees N, 60 degrees oblique (BL) 35 degrees N in buccolingual direction and horizontal (MD) 14 degrees N in mesiodistal direction loads were applied to each of these designs. The principal stresses (tensile and compressive stress) on each model were calculated using MSC MARC finite element analyze solver software. RESULTS: The tensile stress (P(max)) values have been evaluated that they rose at the cervical region of buccal side when the inter-implant distances increased under V and BL loads and they diminished while the inter-implant distances decreased. In short inter-implant distances the compressive stress (P(min)) has been presented with increased values and found at the lingual surface of the cervical region. DISCUSSION: The results of this study indicated that the magnitude of the stress was influenced by complex factors such as the direction of loads and the distance between adjacent fixtures. The stress occurring around fixtures differs significantly with various types of inter-implant distance. CONCLUSION: The evaluation of tensile and compressive stresses for cortical and cancellous bone under V, MD and BL loading conditions in aspect of inter-implant distance shows; the 1.0 cm of inter-implant distance is the optimum distance for two fixture implantation.

Computer Simulation↗

PubMed2001

Validation of finite element analysis in dental ceramics research.

STATEMENT OF PROBLEM: In vitro dental materials strength testing of ceramic restorations primarily has involved mechanical evaluations of simplified models. The finite element method (FEM) provides a mathematic analysis to predict strength values, but neither methodology is without the potential for errors. PURPOSE: The purpose of this study was to demonstrate the advantages of combining mechanical testing results and FEM data to determine the strengths of a layered ceramic beam when the layered materials and positions are varied. MATERIAL AND METHODS: Eight finite element 5 x 20 x 1-mm layered beams were modeled. Four of the modeled beams were of the same layered arrangements as physical specimens from a previously published study. The remaining 4 modeled beams provided intermediate layered arrangements not evaluated in the earlier study. A force in newtons was applied in the center of the top layer of each beam until fracture. finite element analysis was performed, and the data were compared with mechanical strength test results from the earlier study. RESULTS: The FEM data of the 8 models demonstrated a linear decrease in load-bearing capacity as the layer thickness of the core material decreased and the layer thickness of the veneer material increased. The progressively decreasing values for the FEM beams were 170, 144, 140, 134, 72, 43, 34, and 27 N. The mean load-bearing capacities of 3 of the 4 mechanically tested beams compared favorably with the FEM data. The strength of the fourth mechanically tested beam, a veneer/core layered arrangement, was 110 N, which was lower than the corresponding FEM value (140 N). The 110 N value fell outside the decreasing linear progression for load, indicating that the FEM data were more accurate and reliable than the mechanical data. CONCLUSION: No one perfect method exists for testing the strength of dental materials. The best approach is to use the results from both mechanical testing and finite element analysis, which together may provide more reliable and valid data than either method alone.

Aluminum Oxide↗

PubMed2005

The long-term mechanical integrity of non-reinforced PEEK-OPTIMA polymer for demanding spinal applications: experimental and finite-element analysis.

Polyetheretherketone (PEEK) is a novel polymer with potential advantages for its use in demanding orthopaedic applications (e.g. intervertebral cages). However, the influence of a physiological environment on the mechanical stability of PEEK has not been reported. Furthermore, the suitability of the polymer for use in highly stressed spinal implants such as intervertebral cages has not been investigated. Therefore, a combined experimental and analytical study was performed to address these open questions. A quasi-static mechanical compression test was performed to compare the initial mechanical properties of PEEK-OPTIMA polymer in a dry, room-temperature and in an aqueous, 37 degrees C environment (n=10 per group). The creep behaviour of cylindrical PEEK polymer specimens (n=6) was measured in a simulated physiological environment at an applied stress level of 10 MPa for a loading duration of 2000 hours (12 weeks). To compare the biomechanical performance of different intervertebral cage types made from PEEK and titanium under complex loading conditions, a three-dimensional finite element model of a functional spinal unit was created. The elastic modulus of PEEK polymer specimens in a physiological environment was 1.8% lower than that of specimens tested at dry, room temperature conditions (P<0.001). The results from the creep test showed an average creep strain of less than 0.1% after 2000 hours of loading. The finite element analysis demonstrated high strain and stress concentrations at the bone/implant interface, emphasizing the importance of cage geometry for load distribution. The stress and strain maxima in the implants were well below the material strength limits of PEEK. In summary, the experimental results verified the mechanical stability of the PEEK-OPTIMA polymer in a simulated physiological environment, and over extended loading periods. Finite element analysis supported the use of PEEK-OPTIMA for load-bearing intervertebral implants.

Benzophenones↗

PubMedDate not supplied

Factors affecting crestal bone loss with dental implants partially covered with a porous coating: a finite element analysis.

Limited crestal bone loss has been observed around dental implants partially covered with a porous coating. The results of a two-dimensional finite element analysis suggested that for this implant design, the observed crestal bone loss is the result of low stresses acting on bone around the uncoated superior region of the implant, causing disuse atrophy of bone. This finite element study investigated the effect on crestal bone loss of varying the design of the prosthesis connecting pairs of implants, the length of the uncoated region of the implant, and the friction at the noncoated coronal portion of the implant and adjacent host bone.

Alloys↗

PubMed2003

Finite element analysis of the stresses around fixtures in various reconstructed mandibular models--part II (effect of horizontal load).

UNLABELLED: AIM OF EXPERIMENT: Having already studied the effect of vertical load (Nagasao et al., 2002), the purpose of this study was to investigate the effect of horizontal load on implants embedded into a virtually reconstructed mandible. MATERIAL AND METHODS: Three-dimensional virtual models of various reconstructed mandibles were designed on a PC and 50 N horizontal loads were applied on the cantilever portion of the upper structure. Then, using a finite element analysis, stresses occurring around the implants were calculated, and the directions of the forces that cause the maximum von Mises stresses were evaluated. Finally, the results were compared with those from vertical loading. RESULTS: In all models, the maximum stresses occurred around the implants embedded on the premolar region of the loaded side. In addition, the locations at which the maximum von Mises stresses occurred were greatly influenced by the structural character of the loaded side. CONCLUSION: When horizontal loads were applied to reconstructed mandibles, the location and direction of the maximum stresses around the dental implants appeared to be influenced much more by the structural characters of the reconstructed mandibles when compared with vertical loads.

Bone Transplantation↗

PubMed2005

Comparison of different fixation methods following sagittal split ramus osteotomies using three-dimensional finite elements analysis. Part 1: advancement surgery-posterior loading.

The purpose of this study was to evaluate the mechanical behavior of different fixation methods used in bilateral sagittal split ramus osteotomy (BSSRO). Part 1 comprises of the results of the analysis for mandibular advancement, four different fixation configurations of six hole fragmentation mini plates with monocortical screws and lag screws and posterior loading conditions in the molar and premolar region. The finite element analysis method (FEA) appears suitable for simulating complex mechanical stress situations in the maxillofacial region. The mechanical behavior of selected lag screws with linear or triangular configuration and double parallel or single oblique six hole mini plates with monocortical screws were compared by FEA after 5 mm BSSRO advancement procedure. Four separate three-dimensional finite element models of the mandible were created to simulate the BSSRO and corresponding fixation methods. These models consisted of 122,717 elements and 25,048 nodes. The mechanical parameters of the materials studied were adopted from the literature or were based on manufacturer's information. 500 N posterior occlusal loads were simulated on the distal segments. The commercial finite element solver MSC Marc software was utilized to calculate the stress fields on both the segments and fixative appliances. It was concluded that the use of 2.0mm lag screws placed in a triangular configuration following the BSSRO advancement surgery provides sufficient stability with any rotational movement and less stress fields at the osteotomy site, when compared with the other rigid fixation methods used in the current study.

Bicuspid↗

PubMed2007

Finite element analysis of impact loads on the femur.

OBJECTIVE: To investigate the stress distribution and fracture mechanism of proximal femur under impact loads. METHODS: The image data of one male's femur were collected by the Lightspeed multi-lay spiral computed tomography. A 3D finite element model of the femur was established by employing the finite element software ANSYS, which mainly concentrated on the effects of the directions of the impact loads arising from intense movements and the parenchyma on the hip joint as well as those of the femur material properties on the distribution of the Mises equivalent stress in the femur after impact. RESULTS: The numerical results about the effects of the angle sigma of the impact loads to the anterior direction and the angle gamma of the impact loads to the femur shaft on the bone fracture were given. The angle sigma had larger effect on the stress distribution than the angle gamma, which mainly represented the fracture of the upper femur including the femoral neck fracture when the posterolateral femur was impacted. This result was consistent with the clinical one. The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. CONCLUSIONS: A 3D finite element analysis model of the femoral hip joint under dynamic loads is successfully established by using the impact dynamic theory.

Femur↗