Researches on bone defects are focused on the use of composites due to the composite and well-organized hierarchical structure of the bone. In this study, it is aimed to develop Polycaprolactone based implants with different organic &amp / #8211 / DBM, HYA- and/or inorganic &amp / #8211 / bioglass, calcium sulfate- compositions for augmenting bone healing. Bioactivity of the discs was evaluated by scanning electron microscopy and EDS analysis after incubation in SBF for 1, 7 and 14 days. All bioglass containing groups showed apatite molecules at different incubation times. Degradation studies demonstrated that only PCL/BG/HYA discs had fast degradation upon incubations in PBS (4 and 6 weeks). Initial mechanical properties of composites were found to be directly related to the composition. However, decreases in disc mechanical properties were also obtained in the same order with the amount of water uptake at composite groups. According to biocompatibility studies investigated with cytotoxicity tests on Saos-2 cells, all groups, except the HYA involving one were found as biocompatible. After in vivo application of discs to critical size defects on rabbit humeri (for 7 weeks), their efficacy on healing was studied with computerized tomography, SEM and biomechanical tests. The results revealed that bone-implant interface formation has started for all groups with high bone densities at the interface of implant groups compared to empty defect sites of negative controls. Also the healing was suggested to be gradual from bone to implant site as microhardness values increased at regions closer to bone. However, regeneration was found to not reach to healthy bone levels.

Muscle strength is assumed to be closely related with BMD, the so called determinant of bone strength, however, new methods for bone strength measurement are arising. The purpose of this study was to determine the relationship between bone mineral density (BMD), muscle strength and natural frequency of the radius in the dominant and non-dominant arm in healthy and osteopenic individuals aged between 50-70 years. Sixty sedentary male (thirty healthy and thirty osteopenic) participated this study. Bone mineral density assessment was performed by dual x-ray absorbtiometry (DEXA) and quantitative computed tomography (QCT), whereas muscle strength was measured by an isokinetic dynamometer quantitatively. Natural frequency of the radius was determined by a dual channel frequency analyzer. Differences between BMD, muscle strength and natural frequency in healthy and osteopenic participants according to dominancy were examined by Analysis of Variance (ANOVA). Pearson Product Correlation Coefficient test was conducted to determine the magnitude of the correlation between cortical, trabecular and average BMD, muscle strength and natural frequency. Results demonstrated a statistically significant difference between BMD, natural frequency and muscle strength in the dominant arm of both groups. There was also a significant difference in the non-dominant arm in terms of BMD, natural frequency and muscle strength, except in total work in the non-dominant arms. Moreover, there was a moderate positive correlation between BMD measured by DEXA and natural frequency in the dominant arm (r = ,59 / p &lt / .001) and non-dominant arm (r = 0,64 / p &lt / 0.001), whereas the muscle strength was correlated to BMD with a low positive correlation in terms of peak torque in extension (r = ,36 / p = ,005), peak torque in flexion (r = ,31 / p = ,016), total work in extension (r = ,28 / p = ,030) and total work in flexion (r = ,27 / p = ,041) in the dominant arms. The correlation between muscle strength and BMD was not significant in the non-dominant arm. The highest correlation between natural frequency and bone geometry parameters was observed in cortical thickness (r = ,82 / p = ,02). A statistically significant positive correlation (r = ,81 / p = ,04) was also observed between average BMD measured by QCT and by DEXA. In summary, according to the findings of this study, it can be concluded that vibration analysis is a precise method in predicting bone strength that depends highly on its size, shape and the distribution of its trabecular and cortical components.

In order to elucidate the effects of NPY directly on bone tissue, two different doses of NPY (NPY dose 1= 1X10-5 M and NPY dose 2 = 1X 10&amp / #65533 / 6 M) and NPY dose 2 plus its inhibitor were applied together with hyaluronic acid (HA) into the intramedullary area of right tibia of Wistar rats. HA alone was administered as the control group. On three time points, day one, week one and week two after administration, the tibiae were collected and stored at &amp / #65533 / 20oC for analysis. Evaluation was performed via conventional radiography, dual energy X-ray absorbtiometry (DEXA), quantitative computerized tomography (QCT), three point bending test (TPB) and histology techniques. QCT was used to assess both atomic content and density of both medulla and cortex of tibiae. From DEXA results, it was observed that inhibition of NPY causes an increase in the bone mass from first day to second week. This phenomena was also observed in histology results so that new bone formation in the inhibitor administered bone was encountered at week two. In both medulla and cortex areas&amp / #65533 / atomic content, an increase in average effective atomic number was displayed after administration of NPY plus NPY inhibitor throughout two weeks. In addition, density of medulla of tibiae measured by QCT also revealed an increase in bone mass when inhibitor is applied throughout two weeks. As a result, overall evaluation of data obtained from DEXA, QCT and histological analysis revealed that NPY inhibits bone formation or have a pro-osteoclastic effect / inversely HA displayed osteogenic effect.