Master of Science, University of Toledo, 2020, Mechanical Engineering

Synthetic bone cements have been used as organic graft substitutes for since the early 20th century for multiple surgical procedures including orthopedic and dental applications. Ceramic bone cement can primarily consist of phosphate, magnesium, and calcium which are all completely biocompatible and have exceptional properties for bone growth. However, a few main issues with phosphate-based cements includes their poor mechanical and physical qualities such as compressive strength, crack propagation, injectability, and cell culturing. This limits the uses of the cement to non-load bearing bone filler. The other issue is the potential for phase separation during injection in surgery. This causes the liquid component of the cement to be filter pressed through the powder component, and making the cement not set and deteriorate before bone regeneration. However, this would be unacceptable for clinical use. Recent studies have shown that these properties can be better developed through the incorporation additives like fiber reinforcements and retarders, increasing the liquid to powder ratio (LPR), decreasing the particle size, and selecting an efficient syringe. These strategies were used to improve the injectability of the both calcium phosphate cement (CPC) and magnesium phosphate cement (MPC) while maintain the mechanical and biological properties. In the first study the CPC's LPR was increased to 0.4, their powder particle sizes were decreased to less than 90 μm, and a suitable amount of citric acid was added as a retarder. Also, in some of the composition of CPC newberyite (NB), a reinforcement platelet particle, was added in different amounts to test the strength of the cement. In the second study MPC's LPR was increased to 0.4, their powder particle sizes were decreased to less than 45 μm, and a suitable amount of boric acid was added as a retarder. All components of both the CPC and MPC have good biological properties and many papers have shown that changing these (open full item for complete abstract)

Committee: Sarit Bhaduri (Committee Chair); Matthew Franchetti (Committee Member); Vijay Goel (Committee Member) Subjects: Biomedical Engineering

Master of Science, University of Toledo, 2018, Mechanical Engineering

Calcium phosphate (CaP) compounds have been used as orthopedic, spinal and dental implants, and bone graft substitutes for several decades. Their good biocompatibility and bioactivity and most importantly their resemblance to bone and teeth mineral, make them perfect for orthopedic applications. However, the available CaPs possess a major drawback of slow bone formation rate resulting in a longer time for recovery of patients. Thus, this affects the psychological, physical and economic well-being of the patient and their family members. Electrical stimulation has been proven to enhance the osseous formation in different animal studies which in turn led towards the development of different piezoelectric devices and piezoelectric/biomaterial composites. Keeping these facts in mind, present work utilized the piezoelectric nature of Barium titanate (BT) into the different CaP compounds. The prime focus of this thesis is to enhance the electrical properties of CaP such that it helps to promote early osteogenesis. Furthermore, the minimally invasive surgery demands for the injectable self-setting CaP formulations whereas dense CaP scaffolds are most for the load-bearing applications. To address these applications, we carried out two different projects, first being injectable monetite based piezoelectric bone cement and second sintered HA-BT piezobiocomposites. Interestingly, as far as our knowledge, no literature is available on the CaP bone cement with piezoelectric properties. Thus, the development of piezo- CaP bone cement is the first of its kind and signifies the novelty of this thesis. Here, BT particles act as a source of electrical energy during normal physical loading conditions. The incorporation of BT into CaPs results in three major advantages. First, it improves the electrical properties (dielectric constant, piezoelectric coefficient) of the CaPs. Second, considering CaPs as a preferable cell-growing scaffold, BT incorporation enhances osteoblast cell activ (open full item for complete abstract)

Committee: Sarit B. Bhaduri Ph.D. (Committee Chair); Mehdi Pourazady Ph.D. (Committee Member); Matthew Franchetti Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Science in Engineering, University of Akron, 2006, Biomedical Engineering

Autogenous bone graft (ABG) is considered the evaluation standard for cranial defect reconstruction material. A variety of bone substitutes have been used as alternative materials for this procedure, each having its own advantages and disadvantages. Carbonated calcium phosphate (CCPP), a biomaterial form of hydroxyapatite (HA), has been increasingly used for cranial reconstructions. For defects of certain size and shape, CCPP is used with a titanium mesh for structural stability. At the present time there have been no published studies in the literature comparing the biomechanical and histological properties of these cranial bone reconstruction structures over time. In this study two different reconstruction structures were compared to autogenous bone grafts with respect to time. Reconstruction structure A (RCA) used a slow setting CCPP, whereas reconstruction structure B (RCB) used a fast setting CCPP. Unilateral or bilateral cranial defect reconstructions were conducted on sheep with full thickness defect sizes of 1.5 × 3.0 cm. A total of 24 sheep were divided into eight groups with post surgical periods of 0, 6 and 12 months. The skulls' biomechanical properties were evaluated using a free weight drop test protocol. In addition, intact parietal bone was also evaluated at 12 months as a control. Peak acceleration, peak force transmission and time to peak acceleration parameters obtained from the drop weight test were used for analysis. Immediately post-surgery there were no significant differences in any biomechanical characteristics of the experimental groups. At 12 months, the autogenous bone graft (ABG) reconstructions had a significantly superior impact characteristic compared to reconstructions of slow setting CCPP with titanium mesh scaffold and reconstructions of fast setting CCPP with titanium mesh scaffold (p<0.05). At 12 months ABG was not significantly different from the intact bone (p>0.05).

Committee: Glen Njus (Advisor) Subjects: