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.
The aim of this paper is to show that the l/n expansion for n-photon processes can be considered as a quasiclassical one. We discuss qualitatively the domain of validity of the leading term of this expansion and show how corrections to it can be accounted for in a systematic and univocal way. Applications to photoionisation processes in strong laser or microwave fields are also discussed.
Micro-Brillouin scattering (μ-BR) and a 200 MHz scanning acoustic microscope (SAM) with similar spatial resolutions were applied to evaluate tissue elastic properties in two directions in a trabecula. Acoustic impedance measured by SAM was in the range of 5–9 Mrayl. Wave velocities determined by μ-BR were in the range of (4.75–5.11) × 103 m/s. Both exhibited a similar trend of variation across the trabecula and were significantly correlated (R2 = 0.63–0.67, p < 0.01). μ-BR is useful for the evaluation of tissue stiffness within a trabecula. Combined with SAM or nanoindentation, it can provide additional information to assess elastic anisotropy at the micro-scale.
Ultrasonic wave velocities in small trabeculae of bovine femur were investigated using a micro-Brillouin scattering technique. Our micro-Brillouin scattering system enables the measurement of wave velocities in the GHz range over a minute area (diameter: approximately 10 µm). Using thin trabecular specimens with a thickness of about 150 µm, the distribution of longitudinal wave velocity in a trabecula was observed. In the direction parallel to the trabecular alignment, the velocity changed depending on the measurement position. We measured 20 different trabeculae in our specimens, and the average wave velocities in each trabecula were similar at approximately 4.92×103 m/s. In addition, the difference in average velocity was not statistically significant between trabeculae that align in the bone axis or anterior–posterior directions. These data tell us the possibility that the average wave properties are similar in all trabeculae.
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