Acoustic emission(AE) is one of the most sensitive techniques to non invasively monitor deformation, fatigue, and fracture of many materials. The purpose of this study was to evaluate the potential to use AE to detect local failure events within porous ceramic materials. The primary material of interest was mineralized trabecular bone. A better understanding of the failure of trabecular bone is highly relevant to skeletal fragility diseases such as osteoporosis. This study sought to develop a post processing technique that could strengthen the relation between the events detected and the phenomena occurring as a specimen is loaded. The deficiency in other techniques is that they did not fully make a quantitative correlation between acoustic emission event characteristics and the physical occurrence of damage events. The study evaluated the use of seismic power laws because these laws were able to attach a quantitative model to an earthquake and its successive aftershocks. Earthquake transmission has similar propagation attributes when compared to acoustic emission; seismic waves radiate from the epicenter of an earthquake. Acoustic waves radiate from the source of energy release in an acoustic emission event. The study measured the acoustic emission response of trabecular bone and highly oriented ceramics. The bone and ceramics were extracted in two perpendicular directions so that the structural orientation was different. The study sought to evaluate if the power-laws could differentiate the acoustic emission response based on varying the material and varying the structural orientation. The samples were quasi-statically compressed; the mechanical and acoustic emission data were simultaneously recorded. The study found that using the seismic power-law did not statistically differentiate the directional orientation for trabecular bone or ceramic specimens. Acoustic emission did indicate that event detection was different for each type of the of material. Correlations were established with the acoustic emission response and the mechanical testing data. These relationships were explainable because of the mechanical properties of the material.

No description available.

Clinicians have described the success rates of dental implants. The use of implants is projected to increase in the future. With a 5-10% failure rate, it is unclear the exact factors that are associated with implant failures. To improve upon these success rates, it is critical to understand parameters associated with implant failure including: periodontitis, peri-implantitis, systemic diseases, site preparation, dental history of the implant site, bone quality, materials, occlusion, and treatment timelines. While bone quality is associated with failure, objective measures to assess bone quality and characteristics are scarce. Therefore, the aim of this study is to determine whether possible comorbidities, associated dental parameters, and measurable bone quality are possible predictors of implant failure. In this study, we utilized the electronic health record system axiUm® to retrospectively investigate non-failed (NF) and failed (F) dental implants from a patient cohort with 149 implants placed between 2012-2015 at Virginia Commonwealth University School of Dentistry. A chart review was conducted extracting information on age, gender, systemic diseases, smoking, occlusal trauma, parafunction, bone grafting history, treatment timelines, implant site/type/placement protocol, infection, torque at placement, bone quality and microarchitecture assessed by the novel, innovative technology: trabecular bone score (TBS). A total of 149 implants, 46 failures and 105 non-failed controls, were selected based on similar implant sites. Preliminary data obtained from analysis suggests that average time from implant placement to failure was 6.6 months (0.55 years). Parafunction habit (p=0.0202) and increased number of implants (p=0.0478) were found to be associated with increased implant failure.

In this study, trabecular architecture is considered as a cellular solid structure, including both intact and damaged bone models. ??Intact?? bone models were constructed based on ideal versions of 25, 60 and 80-year-old specimens with varying trabecular lengths and orientations to 5%, and 10% covariance of variation (COV). The models were also flipped between longer transverse and longer longitudinal trabeculae. With increasing COV of lengths and orientations of trabecular bone, the apparent modulus is linearly decreased, especially in the longer transverse trabeculae lengths. ??Damaged?? bone models were built from the 25 year old model at 5% COV of longer transverse trabeculae, and with removing trabeculae of 5% and 10% of trabecular volume in transverse and longitudinal directions, respectively, as well as in combination to total 10% and 15%. With increasing percent of trabeculae missing, the apparent modulus decreased, especially dramatically when removal was only in the transverse direction. The trabecular bone models were also connected to a cortical shell and it was found that the apparent modulus of an entire slice was increased in comparison to the modulus of trabecular bone alone. We concluded that the architecture of trabecular bone, especially both lengths and percent of trabecular missing in the longitudinal direction, significantly influences mechanical properties.

In this study, trabecular architecture is considered as a cellular solid structure, including both intact and damaged bone models. ??Intact?? bone models were constructed based on ideal versions of 25, 60 and 80-year-old specimens with varying trabecular lengths and orientations to 5%, and 10% covariance of variation (COV). The models were also flipped between longer transverse and longer longitudinal trabeculae. With increasing COV of lengths and orientations of trabecular bone, the apparent modulus is linearly decreased, especially in the longer transverse trabeculae lengths. ??Damaged?? bone models were built from the 25 year old model at 5% COV of longer transverse trabeculae, and with removing trabeculae of 5% and 10% of trabecular volume in transverse and longitudinal directions, respectively, as well as in combination to total 10% and 15%. With increasing percent of trabeculae missing, the apparent modulus decreased, especially dramatically when removal was only in the transverse direction. The trabecular bone models were also connected to a cortical shell and it was found that the apparent modulus of an entire slice was increased in comparison to the modulus of trabecular bone alone. We concluded that the architecture of trabecular bone, especially both lengths and percent of trabecular missing in the longitudinal direction, significantly influences mechanical properties.

Additive manufacturing technologies are enabling newfound degrees of geometrical complexity to be realised, particularly with regards to internal structures. All of these manufacturing technologies are dependant on their prior design in an appropriate electronic form, either by reverse engineering, or, primarily, by computer-aided design. Within these emerging applications is the design of scaffolds with an intricate and controlled internal structure for bone tissue engineering. There is a consensus that ideal bone scaffold geometry is evident in biological trabecular structures. In their most basic topological form,these structures consist of the non-linear distribution of irregular interconnecting rods and plates of different size and shape. Complex and irregular architectures can be realised by several scaffold manufacturing techniques, but with little or no control over the main features of the internal geometry, such as size, shape and interconnectivity of each individual element. The combined use of computer aided design systems and additive manufacturing techniques allows a high degree of control over these parameters with few limitations in terms of achievable complexity. However, the design of irregular and intricate trabecular networks in computer aided design systems is extremely time-consuming since manually modelling an extraordinary number of different rods and plates, all with different parameters, may require several days to design an individual scaffold structure. In an attempt to address these difficulties, several other research efforts in this domain have largely focussed on techniques which result in designs which comprise of relatively regular and primitive shapes and do not represent the level of complexity seen biologically. Detailed descriptions of these methods are covered in chapter 1. An automated design methodology for trabecular structures is proposed by this research to overcome these limitations. This approach involves the investigation of novel software algorithms, which are able to interact with a conventional computer aided design program and permit the automated design of geometrical elements in the form of rods, each with a different size and shape. The methodology is described in chapter 2 and is tested in chapter 3. Applications of this methodology in anatomical designs are covered in chapter 4. Nevertheless, complex designed rod networks may still present very different properties compared to trabecular bone geometries due to a lack detailed information available which explicitly detail their geometry. The lack of detailed quantitative descriptions of trabecular bone geometries may compromise the validity of any design methodology, irrespective of automation and efficiency. Although flexibility of a design methodology is beneficial, this may be rendered inadequate when insufficient quantitative data is known of the target structure. In this work a novel analysis methodology is proposed in chapter 5, which may provide a significant contribution toward the characterisation and quantification of target geometries, with particular focus on trabecular bone structures. This analysis methodology can be used either to evaluate existing design techniques or to drive the development of new bio-mimetic design techniques. This work then progresses to a newly derived bio-mimetic automated design technique, driven by the newly produced quantitative data on trabecular bone geometries. This advanced design methodology has been developed and tested in chapter 6. This has demonstrated the validity of the technique and realised a significant stage of development in the context and scope of this work.

L’os subit perpétuellement des contraintes mécaniques et physiologiques, ainsi sa qualité et sa résistance à lafracture évoluent constamment au cours du temps à travers le processus de remodelage osseux. Cependant,certaines pathologies osseuses comme l’ostéoporose ou la maladie de Paget altèrent cette dernière et conduisent àune augmentation du risque de fracture osseuse. La qualité osseuse est non seulement définie par la densitéminérale osseuse (DMO) mais également par les propriétés mécaniques ainsi que la microarchitecture. Au total, onévalue en France à environ 3 millions le nombre de femmes et 1 million le nombre d’hommes souffrantd’ostéoporose, pour un coût estimé à 1 milliard d’euros. La prévention par le développement d’outils de diagnosticest nécessaire. Le diagnostic doit permettre d’estimer la qualité osseuse (propriétés mécaniques, activitéscellulaires, architecture). Ces travaux de thèse proposent un modèle innovant permettant de combiner lesdifférents facteurs agissant sur le remodelage osseux, à savoir : (i) le comportement mécanique, (ii) l’activitécellulaire, (iii) le processus de transduction ; visant à traiter les différentes informations d’origines mécanique etbiochimique. Les lois de comportement mécaniques et cellulaires sont issues de modèles validés dans la littératureet la stratégie d’unification voit sa justification à travers différents travaux sur les mécanismes de transduction.Ainsi, l’implémentation de ces trois acteurs du remodelage dans une analyse par éléments finis permet d’obtenirun modèle mécano-biologique du remodelage de l’os trabéculaire. Le modèle est applicable à différentes échelles etpermet d’étudier le niveau de remodelage local modulé par l’activité physique et la concentration de certains agentsbiochimiques. L’application du modèle sur un volume virtuel de fémur selon différents scénarios cliniques donnedes résultats conformes aux observations faites en imagerie médicale. / By continuously undergoing mechanical and physiological stresses, bone quality and bone strength evolve throughremodeling process. However, osteoporosis and Paget’s disease for instance alter bone quality and increase the risk of bone fracture. Bone quality is mainly defined by its Bone Mineral Density (BMD) but mechanical properties and microarchitecture have also to be taken into account for a proper definition. About 3 million of women and 1 million of men suffer from osteoporosis which costs approximately 1 billion Euros per year in France. This highlights the necessity to develop diagnostic tools in order to enable proper bone quality characterization (mechanical properties, cellular activity and architecture).This thesis proposes an original model combining the main bone remodeling constituents which are : (i) the mechanical behavior, (ii) the cellular activity, (iii) the transduction phase ; enabling mechanical and biochemical information processing. Mechanical and cellular behavior models are taken from already published work and the transduction phase model unifying mechanical and biological information is inspired from the literature. Consequently, the implementation of these three main bone remodeling constituents into a finite element analysis gives a plausible mechano-biological model of trabecular bone remodeling. The developed model can be used at different scales in order to study the local amount of bone remodeled, magnified by physical activity and the concentration of some biochemical agents. Its application on virtual volume of femora under different clinical scenarios gives good results in respect to medical images observations.

Yes / Age at death estimation of human skeletal remains is one of the key issues in constructing a biological profile both in forensic and archaeological contexts. The traditional adult osteological methods evaluate macroscopically the morphological changes that occur with increasing age of specific skeletal indicators, such as the cranial sutures, the pubic bone, the auricular surface of the ilium and the sternal end of the ribs. Technologies such as CT and laser scanning are becoming more widely used in anthropology, and several new methods have been developed. This review focuses on how the osteological age-related changes have been evaluated in digital data. Firstly, the 3D virtual copies of the bones have been used to mimic the appearance of the dry bones and the application of the traditional methods. Secondly, the information directly extrapolated from CT scan has been used to qualitatively or quantitatively assess the changes of the trabecular bones, the thickness of the cortical bones, and to perform morphometric analyses. Lastly, the most innovative approach has been the mathematical quantification of the changes of the pelvic joints, calculating the complexity of the surface. The importance of new updated reference datasets, created thanks to the use of CT scanning in forensic settings, is also discussed. / CV was supported from the Danish Council for Independent Research (DFF – 4005-00102B – FTP)

No description available.

L'ostéoporose est un problème majeur de santé publique (150000 fractures par an en France), qui se traduit par une diminution de la masse et de la « qualité » osseuse entraînant une augmentation du risque fracturaire. Basés uniquement sur une mesure de densité minérale osseuse, les moyens cliniques actuels de diagnostic de cette pathologie apparaissent insuffisants pour quantifier précisément la résistance mécanique de l'os. Dans cette optique, il est primordial de pouvoir évaluer non seulement l'évolution de masse osseuse au cours du temps, mais également ses propriétés mécaniques tant macro que micro. Cette thèse est consacrée au développement d'un modèle numérique de remodelage osseux intégrant des paramètres mécano-biologiques permettant de simuler à la fois la dégradation d'une microstructure d'os trabéculaire au cours du temps ainsi que son adaptation mécanique. Une modification de ces paramètres permet de simuler des cas pathologiques avec ou sans traitements anti-ostéoporotiques. Le remodelage est ensuite couplé au processus de mécanotransduction, en intégrant l'influence du chargement mécanique sur la réponse cellulaire. Différents cas de chargement ont été ainsi modélisés, en particulier faible chargement tel que l'alitement, ou surchargement tel que la pratique d'activités sportives. L'hyperminéralisation ainsi que l'hétérogénéité du tissu osseux ont été intégrés au modèle et leur influence sur la localisation des sites de remodelage a été également analysée. Les résultats des simulations obtenus à partir de microarchitectures d'os humain sur plusieurs années sont encourageants car ils concordent avec les observations cliniques. / Osteoporosis is characterized by a low bone mass density but also an alteration of mechanical properties. The clinical diagnostic is made from the measure of the bone mineral density (BMD) but this examen seems insufficient to quantify bone resistance. In this work, a numerical model of cancellous bone degradation, aging and mechanical adaptation is proposed. Based on hypermineralization, this model simulates the cancellous bone remodeling process over many years. This model allows to predict the behavior of cancellous adaptation in a mechanical low loading case for instance. Results are similar to clinicial tendancy.