Fani Anagnostou

Publications (12)31.26 Total impact

• Article: Mode III cleavage of a coin-shaped titanium implant in bone: effect of friction and crack propagation.

  Vincent Mathieu, Romain Vayron, Etienne Barthel, Davy Dalmas, Emmanuel Soffer, Fani Anagnostou, Guillaume Haiat
  [show abstract] [hide abstract]
  ABSTRACT: Endosseous cementless implants are widely used in orthopaedic, maxillofacial and oral surgery. However, failures are still observed and remain difficult to anticipate as remodelling phenomena at the bone-implant interface are poorly understood. The assessment of the biomechanical strength of the bone-implant interface may improve the understanding of the osseointegration process. An experimental approach based on a mode III cleavage mechanical device aims at understanding the behaviour of a planar bone-implant interface submitted to torsional loading. To do so, coin-shaped titanium implants were inserted on the tibiae of a New Zealand white rabbit for seven weeks. After the sacrifice, mode III cleavage experiments were performed on bone samples. An analytical model was developed to understand the debonding process of the bone-implant interface. The model allowed to assess the values of different parameters related to bone tissue at the vicinity of the implant with the additional assumption that bone adhesion occurs over around 70% of the implant surface, which is confirmed by microscopy images. The approach allows to estimate different quantities related to the bone-implant interface such as: torsional stiffness (around 20.5 N m rad(-1)), shear modulus (around 240 MPa), maximal torsional loading (around 0.056 N.m), mode III fracture energy (around 77.5 N m(-1)) and stress intensity factor (0.27 MPa m(1/2)). This study paves the way for the use of mode III cleavage testing for the investigation of torsional loading strength of the bone-implant interface, which might help for the development and optimization of implant biomaterial, surface treatment and medical treatment investigations.
  Journal of the mechanical behavior of biomedical materials. 04/2012; 8:194-203.
• Article: Influence of healing time on the ultrasonic response of the bone-implant interface.

  Vincent Mathieu, Romain Vayron, Emmanuel Soffer, Fani Anagnostou, Guillaume Haïat
  [show abstract] [hide abstract]
  ABSTRACT: The aim of the present study is to investigate the effect of bone healing on the ultrasonic response of coin-shaped titanium implants inserted in rabbit tibiae. The ultrasound response of the interface was measured in vitro at 15 MHz after 7 and 13 weeks of healing time. The average value of the ratio r between the amplitudes of the echo of the bone-implant interface and of the water-implant interface was determined. The bone-implant contact (BIC) was measured by histomorphometry and the degree of mineralisation of bone was estimated qualitatively by histologic staining. The significant decrease of the ultrasonic quantitative indicator r (p = 2.10⁻⁴) vs. healing time (from r = 0.53 to r = 0.49) is explained by (1) the increase of the BIC (from 27% to 69%) and (2) the increase of mineralization of newly formed bone tissue, both phenomena inducing a decrease of the gap of acoustical impedance.
  Ultrasound in medicine & biology 04/2012; 38(4):611-8. · 2.02 Impact Factor
• Article: Influence of healing time on the echographic response of the bone-implant interface.

  Vincent Mathieu, Romain Vayron, Emmanuel Soffer, Fani Anagnostou, Guillaume Haiat
  [show abstract] [hide abstract]
  ABSTRACT: The study aims at investigating the effect of bone healing on the ultrasonic response of coin-shaped titanium implants. Sixteen implants were inserted on the tibiae of rabbits. Two groups of eight samples were considered, each group corresponding to a healing duration (7 or 13 weeks). After the sacrifice, the ultrasonic response of the bone-implant interface was measured in vitro at 15 MHz with a 2-D scanning device. The average value of the ratio r between the amplitudes of the echo of the bone-implant interface and of the water-implant interface was determined. The fraction of implant surface in contact with bone was measured by histomorphometry. The ultrasonic quantitative indicator r decreases significantly with healing time (p = 2.10(-4), from r = 0.53 to r = 0.49). Two phenomena are responsible for the decrease of the gap of acoustical impedance at the bone-implant interface: i) the increase of mineralization of newly formed bone tissue and ii) the increase of the bone-implant contact fraction (from 27 % to 69 %).
  The Journal of the Acoustical Society of America 04/2012; 131(4):3368. · 1.55 Impact Factor
• Article: Ultrasonic set up for the assessment of the stability of a cylinder inserted in a solid.

  Vincent Mathieu, Fani Anagnostou, Emmanuel Soffer, Guillaume Haiat
  [show abstract] [hide abstract]
  ABSTRACT: The study aims at proposing a new experimental ultrasonic methodology for the estimation of the stability of a cylinder inserted in a solid. Such a technology may have various fields of application: aeronautics, car industry, mechanics or also surgery. The present prototype is dedicated to the study of the stability of dental implants. Cylindrical titanium implants were inserted in four groups of rabbit femurs, each group corresponding to a controlled level of stability of the cylinders. The 10 MHz ultrasonic response of the cylinder is processed to derive quantitative indicators based on the temporal variation of the signal amplitude. Analysis of variance (ANOVA) (p < 10(-5)) tests revealed statistical distributions of indicators significantly correlated with the stability of the cylinders. A numerical finite-difference time-domain model was considered in order to understand the origin of the different echoes and the importance of lateral wave propagation was evidenced. The numerical model also enabled to estimate the sensitivity of the indicators to variations in the material properties of the materials in contact with the cylinders.
  The Journal of the Acoustical Society of America 04/2012; 131(4):3439. · 1.55 Impact Factor
• Article: Nanoindentation measurements of biomechanical properties in mature and newly formed bone tissue surrounding an implant.

  Romain Vayron, Etienne Barthel, Vincent Mathieu, Emmanuel Soffer, Fani Anagnostou, Guillaume Haiat
  [show abstract] [hide abstract]
  ABSTRACT: The characterization of the biomechanical properties of newly formed bone tissue around implants is important to understand the osseointegration process. The objective of this study is to investigate the evolution of the hardness and indentation modulus of newly formed bone tissue as a function of healing time. To do so, a nanoindentation device is employed following a multimodality approach using histological analysis. Coin-shaped implants were placed in vivo at a distance of 200 μm from the cortical bone surface, leading to an initially empty cavity of 200 μm * 4.4 mm. Three New Zealand White rabbits were sacrificed after 4, 7, and 13 weeks of healing time. The bone samples were embedded and analyzed using histological analyses, allowing to distinguish mature and newly formed bone tissue. The bone mechanical properties were then measured in mature and newly formed bone tissue. The results are within the range of hardness and apparent Young's modulus values reported in previous literature. One-way ANOVA test revealed a significant effect of healing time on the indentation modulus (p < 0.001, F = 111.24) and hardness (p < 0.02, F = 3.47) of bone tissue. A Tukey-Kramer analysis revealed that the biomechanical properties of newly formed bone tissue (4 weeks) were significantly different from those of mature bone tissue. The comparison with the results obtained in Mathieu et al. (2011, "Micro-Brillouin Scattering Measurements in Mature and Newly Formed Bone Tissue Surrounding an Implant," J. Biomech. Eng., 133, 021006). shows that bone mass density increases by approximately 13.5% between newly formed bone (7 weeks) and mature bone tissue.
  Journal of Biomechanical Engineering 02/2012; 134(2):021007. · 1.90 Impact Factor
• Article: Numerical simulation of ultrasonic wave propagation for the evaluation of dental implant biomechanical stability.

  Vincent Mathieu, Fani Anagnostou, Emmanuel Soffer, Guillaume Haiat
  [show abstract] [hide abstract]
  ABSTRACT: Osseointegration of dental implants remains poorly understood. The objective of this numerical study is to understand the propagation phenomena of ultrasonic waves in prototypes cylindrically shaped implants and to investigate the sensitivity of their ultrasonic response to the surrounding bone biomechanical properties. The 10 MHz ultrasonic response of the implant was calculated using a finite difference numerical simulation tool and was compared to rf signals taken from a recent experimental study by Mathieu et al. [Ultrasound Med. Biol. 37, 262-270 (2011a)]. Reflection and mode conversion phenomena were analyzed to understand the origin of the different echoes and the importance of lateral wave propagation was evidenced. The sensitivity of the ultrasonic response of the implant to changes of (i) amount of bone in contact with the implant, (ii) cortical bone thickness, and (iii) surrounding bone material properties, was compared to the reproducibility of the measurements. The results show that, either a change of 1 mm of bone in contact with the implant, or 1.1 mm of cortical thickness or 12% of trabecular bone mass density should be detectable. This study paves the way for the investigation of the use of quantitative ultrasound techniques for the evaluation of bone-implant interface properties and implant stability.
  The Journal of the Acoustical Society of America 06/2011; 129(6):4062-72. · 1.55 Impact Factor
• Article: Micro-Brillouin scattering measurements in mature and newly formed bone tissue surrounding an implant.

  Vincent Mathieu, Kenji Fukui, Mami Matsukawa, Masahiko Kawabe, Romain Vayron, Emmanuel Soffer, Fani Anagnostou, Guillaume Haiat
  [show abstract] [hide abstract]
  ABSTRACT: The evolution of implant stability in bone tissue remains difficult to assess because remodeling phenomena at the bone-implant interface are still poorly understood. The characterization of the biomechanical properties of newly formed bone tissue in the vicinity of implants at the microscopic scale is of importance in order to better understand the osseointegration process. The objective of this study is to investigate the potentiality of micro-Brillouin scattering techniques to differentiate mature and newly formed bone elastic properties following a multimodality approach using histological analysis. Coin-shaped Ti-6Al-4V implants were placed in vivo at a distance of 200 μm from rabbit tibia leveled cortical bone surface, leading to an initially empty cavity of 200 μm×4.4 mm. After 7 weeks of implantation, the bone samples were removed, fixed, dehydrated, embedded in methyl methacrylate, and sliced into 190 μm thick sections. Ultrasonic velocity measurements were performed using a micro-Brillouin scattering device within regions of interest (ROIs) of 10 μm diameter. The ROIs were located in newly formed bone tissue (within the 200 μm gap) and in mature bone tissue (in the cortical layer of the bone sample). The same section was then stained for histological analysis of the mineral content of the bone sample. The mean values of the ultrasonic velocities were equal to 4.97×10(-3) m/s in newly formed bone tissue and 5.31×10(-3) m/s in mature bone. Analysis of variance (p=2.42×10(-4)) tests revealed significant differences between the two groups of measurements. The standard deviation of the velocities was significantly higher in newly formed bone than in mature bone. Histological observations allow to confirm the accurate locations of the velocity measurements and showed a lower degree of mineralization in newly formed bone than in the mature cortical bone. The higher ultrasonic velocity measured in newly formed bone tissue compared with mature bone might be explained by the higher mineral content in mature bone, which was confirmed by histology. The heterogeneity of biomechanical properties of newly formed bone at the micrometer scale may explain the higher standard deviation of velocity measurements in newly formed bone compared with mature bone. The results demonstrate the feasibility of micro-Brillouin scattering technique to investigate the elastic properties of newly formed bone tissue.
  Journal of Biomechanical Engineering 02/2011; 133(2):021006. · 1.90 Impact Factor
• Article: Ultrasonic evaluation of dental implant biomechanical stability: an in vitro study.

  Vincent Mathieu, Fani Anagnostou, Emmanuel Soffer, Guillaume Haïat
  [show abstract] [hide abstract]
  ABSTRACT: Dental implants are widely used for oral rehabilitation. However, there remain risks of failure that are difficult to anticipate. The objective of this ex vivo study is to investigate the potentiality of quantitative ultrasound (QUS) to assess the amount of bone in contact with titanium prototype cylindrical implants. Four groups of 10 rabbit femurs each are considered, corresponding to different amounts of bone in contact with the implant. The 10 MHz ultrasonic response of the implant is processed to derive a quantitative indicator I, based on the temporal variation of the signal amplitude. Analysis of variance (ANOVA) (p < 10(-5)) tests revealed a statistical distribution of I significantly correlated with the amount of bone in contact with the cylinders. An analytical model considering the propagation of lateral waves allows the understanding of the physical origin of the echoes. QUS technique may be used to investigate the amount of bone in contact with a cylinder implant.
  Ultrasound in medicine & biology 02/2011; 37(2):262-70. · 2.02 Impact Factor
• Source

  Available from: Sébastien Zilber

  Article: Osteoblastic differentiation of human mesenchymal stem cells with platelet lysate.

  Nathalie Chevallier, Fani Anagnostou, Sebastien Zilber, Gwellaouen Bodivit, Sophie Maurin, Aurelie Barrault, Philippe Bierling, Philippe Hernigou, Pierre Layrolle, Helene Rouard
  [show abstract] [hide abstract]
  ABSTRACT: Culture of expanded mesenchymal stem cells (MSCs) seeded on biomaterials may represent a clinical alternative to autologous bone graft in bone regeneration. Foetal bovine serum (FBS) is currently used for MSC expansion, despite risks of infectious disease transmission and immunological reaction due to its xenogenic origin. This study aimed to compare the osteogenic capacities of clinical-grade human MSCs cultured with FBS or allogenic human platelet lysate (PL). In vitro, MSCs cultured in PL both accelerate the expansion rate over serial passages and spontaneously induce osteoblastic gene expression such as alkaline phosphatase (ALP), bone sialoprotein (BSP), osteopontin (Op) and bone morphogenetic protein-2 (BMP-2). In vivo, ectopic bone formation is only observed on ceramics seeded with MSCs grown in PL medium implanted under the skin of immunodeficient mice for 7 weeks. In conclusion, allogenic human PL accelerates MSC proliferation and enhances MSC osteogenic differentiation.
  Biomaterials 09/2009; 31(2):270-8. · 7.40 Impact Factor
• Source

  Available from: Graciela Pavon-Djavid

  Article: Osteoblast functions on functionalized PMMA-based polymers exhibiting Staphylococcus aureus adhesion inhibition.

  Fani Anagnostou, Aurore Debet, Graciela Pavon-Djavid, Zakaryia Goudaby, Gérard Hélary, Véronique Migonney
  [show abstract] [hide abstract]
  ABSTRACT: Staphylococcus aureus adhesion and osteoblast functions were assessed on functionalized poly(methyl methacrylate)-based terpolymers bearing randomly distributed carboxylate and sulfonate groups. These terpolymers were synthesized by radical polymerization, characterized by nuclear resonance spectroscopy and classified by the ratio R=[COO(-)/COO(-)+SO(3)(-)] in the range 0.5-0.8. Bacterial adhesion study showed that fibronectin-coated terpolymers with R varying from 0.5 to 0.8 exhibited inhibition rate of S. aureus adhesion from 90% to 98% as compared to the adhesion on unfunctionalized poly(methyl methacrylate). In contrast, the adhesion of osteoblasts onto the same functionalized terpolymers was decreased by 20% when compared to the results obtained on poly(methyl methacrylate). While the amount of attached osteoblasts are similar onto all the functionalized terpolymers whatever its R value, the cell proliferation was different and was found to vary with R in the range 0.5-0.8. Osteoblast proliferation, alkaline phosphatase activity and accumulation of calcium in the extracellular matrix of these cells, cultured on the functionalized terpolymers with R equal to 0.7-0.8 were similar to that observed onto non-functionalized poly(methyl methacrylate). In contrast, osteoblast proliferation was inhibited on terpolymers with an R value around 0.6. These results provide evidence that functionalized poly(methyl methacrylate)-based terpolymers with R ratio equaling 0.7-0.8 simultaneously inhibit bacteria adhesion and support osteoblast functions pertinent to new bone formation. These functionalized polymers could, therefore, be used as coating or grafted on orthopedic and dental implants to render them both bone compatible and able to prevent bacterial infection.
  Biomaterials 08/2006; 27(21):3912-9. · 7.40 Impact Factor
• Article: Effects of platelet lysates on select bone cell functions.

  Emmanuel Soffer, Jean-Pierre Ouhayoun, Christine Dosquet, Alain Meunier, Fani Anagnostou
  [show abstract] [hide abstract]
  ABSTRACT: Although platelet-rich plasma and platelet concentrates have been used to promote bone healing in orthopaedic and maxillofacial surgery, the underlying cellular-level mechanisms remain poorly understood. The present in vitro study investigated the effects of human platelet lysate (PL) on selected functions of cultured bone cells. Cells from 18-day-old fetal rat calvaria were isolated by a collagenase digestion procedure. PL was added at different concentrations on pre- or post-confluent cell stage. After 1 day, bone cell proliferation was maximal and half-maximal in the presence of PL from 3 x 10(8) and 0.5 x 10(8) platelets/ml, respectively. During 17 h, the number of bone cells traversing the scrape border of a scrape wound model increased by 16-fold in the presence of PL from 3 x 10(8) platelets/ml. The presence of PL from 3 x 10(8) platelets/ml in pre-confluent bone cell cultures for 48 h resulted in a threefold decrease of alkaline phosphatase (ALP) specific activity. In the case of confluent bone cells, the presence of PL (from 1 x 10(6) to 3 x 10(8) platelets/ml) for 11 days, the ALP specific activity and total calcium content decreased in a PL dose-dependent manner and reached a minimum in the presence of PL from 3 x 10(8) platelets/ml. In summary, short-term PL exposure (up to 24 h) promotes the proliferative and chemotactic bone cell functions while long-term PL exposure results in a decrease of both ALP activity and mineral formation. These data show that the soluble components contained in PL may affect the bone healing process by modulating differently bone cell functions.
  Clinical Oral Implants Research 11/2004; 15(5):581-8. · 2.51 Impact Factor
• Article: Fibrin sealants and platelet preparations in bone and periodontal healing.

  Emmanuel Soffer, Jean Pierre Ouhayoun, Fani Anagnostou
  [show abstract] [hide abstract]
  ABSTRACT: Fibrin sealants and platelet concentrates have been used alone or in association with bone substitutes to promote bone healing in orthopedic and oral surgery. Commercial fibrin sealants are homologous plasma-derived products that mimic the last step of a coagulation cascade, leading to a fibrin clot. They are used for topical hemostasis and tissue sealing and as melting agents for particulate bone substitutes. Infectious risk led to the development of autologous fibrin sealants from the patient's own plasma. However, their fabrication results in less reproducible or less satisfactory rheologic properties. The use of autologous products with high platelet concentrations, such as platelet-rich plasma, platelet concentrate, and platelet gels, has recently been suggested for combining the fibrin sealant properties with the growth factor effects of platelets. We describe the characteristics and limitations of fibrin sealants (commercial/autologous) and platelet preparations and review their effects on bone and periodontal healing as reported in experimental studies and clinical trials.
  Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontics 06/2003; 95(5):521-8. · 1.46 Impact Factor