A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Dentistry in the branch of Maxillofacial and Oral Surgery 31 May 2018. / Aim The aim of this retrospective study was to determine the outcomes of secondary alveolar bone grafts (SABG) in cleft patients treated at the Wits Dental Hospital at the Charlotte Maxeke Johannesburg Academic Hospital. Objectives To record the demographic data of patients who had secondary alveolar bone grafts, and to assess the outcomes of SABG by evaluating clinical variables and the quantity of bone post SABG. Methods Records of 19 patients with a total of 23 clefts were examined to evaluate the amount of bone at the cleft site following secondary alveolar bone graft. Socio-demographic information was collected as well as the clinical variables of the type of graft used, canine eruption, keratinised tissue around teeth close to the cleft, and closure or persistence of any oronasal fistula. The amount of bone at the graft site was measured on CBCT images using the Chelsea scale. Comparisons of Chelsea scale scores and CBCT findings were carried out. SPSS ® 24 was used to analyse the data. All statistical tests were conducted at 5% significance level. Results Most (52%) patients were male, with 57% having left unilateral cleft. The majority of them received autogenous bone grafts from the chin. Most (65.2%) of the patients showed good clinical outcomes, whilst showing evidence of bone resorption in and around the graft site on CBCT images. Fifteen of the patients were considered to have partial alveolar graft resorption. Conclusion In the majority of patients, 3D CBCT images revealed bone resorption in areas that 2D images gave an impression of presence of bone. However, the majority of patients indicated good clinical outcomes despite the poor radiological findings. / LG2018

No description available.

This paper will seek to evaluate results obtained from mechanical testing and computational analysis to determine the efficacy of new thread designs for bone screws in their various applications and uses in surgical treatments. These new thread designs will be tested against the market standard buttress thread and any resulting trends will be analyzed. Four different thread designs were tested in 90 degree cyclic loading and then subsequently an axial pullout test. The parameters of interest from these tests such as peak to peak displacement over cycle and axial load versus axial displacement were recorded. These four designs were the Osteocentric A and C designs, the Synthes buttress screw, and a buttress screw with a matching major diameter to the Osteocentric A and C threads

No description available.

In the United States, osteoporosis results in about 1.5 million annual fractures, costing approximately $15 billion. Calcitonin is safe and effective in slowing osteoporotic bone loss, but its effect is transient. The current studies were designed to explore the dose-dependent effects of salmon calcitonin on bone turnover in ovariectomized rats and to determine if the decrease in therapeutic effectiveness of calcitonin demonstrated over time with higher doses is due to oversuppression of bone turnover. Doses of 5, 15, & 50 IU/kg BW/day of calcitonin were compared to placebo in 12-week-old ovariectomized and sham-ovariectomized Sprague-Dawley rats for 24 weeks. The spinal bone mineral content (BMC) as measured by DXA in ovariectomized subjects receiving 5 & 15 IU/kg of calcitonin was not significantly different from sham-ovariectomized subjects, while spinal BMC of subjects receiving 50 IU/kg was significantly lower than shamovariectomized subjects (p<0.05). Femoral BMC of ovariectomized subjects was significantly lower than sham-ovariectomized subjects (p<0.05), but no significant differences were noted between treatment groups. Scanning electron microscopy (SEM) demonstrated a decrease in number and density of trabeculae and in cortical thickness when comparing femurs from ovariectomized with sham-ovariectomized subjects. SEM of subjects receiving 50 IU/kg displayed greater bone loss than other groups. No significant differences were noted between groups for levels of urinary helical peptides or serum pyridinoline [ELISA], indicators of bone resorption. Urinary calcium excretion [capillary ion electrophoresis] was significantly higher in subjects receiving 50 IU/kg of calcitonin than other ovariectomized subjects (p<0.05). Serum levels of osteocalcin [RIA], an indicator of bone formation, were significantly higher in subjects receiving 5 IU/kg of calcitonin than control subjects and those receiving 50 IU/kg (p<0.05). Production of antibodies to calcitonin [ELISA] by subjects in this study did not correlate with changes in bone turnover or bone density. The results of this study do not provide evidence higher doses of calcitonin result in oversuppression of bone turnover. However, urinary calcium excretion affected bone resorption in a reverse dose-dependent manner, suggesting the calciuric effect may be responsible for less effective outcomes seen with higher doses of calcitonin.

Consensus in scientific literature is that hyperglycemia, which is a condition that manifests in individuals with uncontrolled diabetes, causes compromised bone growth, but the exact mechanisms of are unknown. It has been estimated that 5% of dental implant failures that have previously been linked to unknown causes may be associated with undiagnosed diabetes. It is important to study the early stages of bone growth as it is accepted that they are critical in the long-term success rate of endosseous implants. This study aimed to investigate the bone healing seen in the hyperglycemic group compared to the normal (i.e. control) group, at an early time point, using high-resolution microscopy techniques. Ten young (200-250gram) male Wistar rats were used for this study with five rats assigned to the control group and the other five rats intravenously injected with 65 mg/kg of streptozotocin (STZ) to induce diabetes. An osteotomy model was used to make a 1.3mm defect in the diaphysis of the rat femurs. After five days, the femurs were removed, fixed in glutaraldehyde, dehydrated, and embedded in resin. Structural and chemical analyses were conducted on the samples using a variety of microscopy techniques to examine various factors of bone quality including: bone porosity, relative mineralization level, and the arrangement of collagen and mineral. When analyzing the micro-structure, the hyperglycemic group showed increased porosity in the newly formed bone as compared to the control group. However, no significant differences were found in the nano-structure when analyzing the arrangement of collagen and mineral.Therefore, the results in this thesis suggest that alterations in micro-architecture rather than nano-architecture may play a pivotal role in the compromised bone healing in uncontrolled diabetes at this five-day time point. Future work should investigate additional time points in the bone healing process. / Thesis / Master of Applied Science (MASc) / According to the International Diabetes Federation, 387 million people worldwide are living with diabetes of which 46.3% are undiagnosed. Uncontrolled diabetes results in hyperglycemia, which is a condition where there is an increased level of glucose in the blood. When diabetes is not regulated correctly with medication, it leads to problems in the long-term success rate of dental implants. The objective of this thesis was to investigate the early stages of bone formation, which are accepted to be critical in the long-term success rate of dental implants, in hyperglycemic animal models compared to control groups using various microscopy techniques. The different techniques used allowed for the structural and elemental compositions of bone to be studied on the micro-scale and nano-scale. It was shown that at the 5-day healing time point studied, the micro-structure, rather than the nano-structure, was negatively altered in the hyperglycemic group compared to the control group.

Fractures of the lower leg are common during frontal automotive collisions and military blasts. These two scenarios cause injury via a similar axial loading mechanism. The majority of previous studies that have conducted axial impact tests to determine the injury limits of the lower leg have simulated automotive impacts; however, due to the viscoelastic nature of bone, it remains unclear whether limits from automotive experiments can be applied to higher-rate blasts. The purpose of this work was to study the effect of load rate on the fracture tolerance of the tibia during these two scenarios. The instrumentation required to quantify impacts to lower leg specimens using a pneumatic impactor was developed, and included capturing synchronized load, acceleration, velocity, strain, and high-speed video data. Subsequently, impact testing was performed on twelve human cadaveric tibias. Velocities and impact durations were matched to literature values to simulate an automotive collision and a military blast. Force and impulse were found to significantly differ between the two conditions, while kinetic energy did not. Specimens impacted at higher rates required greater forces to achieve fracture, which suggests that load rate needs to be accounted for in future injury criteria. Two commonly used anthropomorphic test device lower legs were tested under similar loading conditions, and new thresholds were developed for these devices. Finally, a finite element model was tested for its ability to simulate loading of the tibia during varied impacts. This model can be used to assess injury risk and protective measures for the leg. Understanding the effect of load rate on the tibia’s fracture tolerance is essential when developing injury thresholds that can be applied to impacts of various rates. The results of this work can be used in the future to design and evaluate improved protective systems to be implemented in vehicles. / Thesis / Master of Applied Science (MASc) / Fractures of the lower leg are common during frontal automotive collisions and military blasts. Due to the viscoelastic nature of bone, it remains unclear whether safety limits from automotive experiments can be applied to higher-rate blasts. The purpose of this work was to study the effect of load rate on the fracture tolerance of the tibia during these two scenarios. Impact testing was performed on twelve human cadaveric tibias. Specimens impacted at higher rates required greater forces to achieve fracture, which suggests that load rate needs to be accounted for in future injury criteria. Two commonly used crash test dummy lower legs were tested under similar loading conditions, and a finite element model was developed and tested to simulate loading of the tibia during high-rate impacts. The results of this work can be used to design and evaluate improved protective systems to be implemented in vehicles.

Designing artificial tissue is an essential part of modern-day medicine. This is also true for bone tissue repair. Work presented in this thesis shows the steps and development of novel cellulose-based biomaterials for bone tissue engineering (BTE). Cellulose is used as the core component in these biomaterials. This work begins with an overview of the thesis, followed by a background review of the relevant biological and physical concepts. Thereafter, original research on the biomechanical properties of apple-derived cellulose are carried out in vitro and in vivo. Afterward, relevant physical forces are applied to the same type of material, to investigate the osteogenic response. Finally, cellulose nanofibrils were chemically modified to create scaffolds through UV crosslinking. These were mechanically characterized and used as scaffolds for osteogenic cell culture. As demonstrated in this work, the use of cellulose-sourced biomaterials is certainly a promising alternative compared to the industry standard. Numerous studies have demonstrated how cellulose-based biomaterials can be employed in several branches of reconstructive medicine. However, uncertainties still exist in the application of these materials for bone tissue reconstruction such as their performance under physical stress, and in their scalability. The research presented in this thesis attempts to address these gaps in knowledge. Specifically, the results presented here show how these materials can be promising candidates for low-load BTE applications. Furthermore, it is also demonstrates that mechanosensitive pathways that regulate osteogenesis remain functional on these materials. Finally, UV-curable cellulose-derived scaffolds create a more scalable and controllable biomaterial for BTE implants, notably using light-based three-dimensional printing technologies.

The ability of NSAIDs to delay bone healing has been long known, although the extent and exact mechanism remains elusive. The present study evaluates the effect of short duration NSAID on bone healing in dogs following experimental tibial osteotomy. Carprofen was administered twice daily for either 0, 2, or 8 weeks following surgery. Bone healing was evaluated radiographically using RUST scoring at 4 and 8 weeks postop. Postmortem, quantitative CT of for bone mineral density analysis, histologic cartilage:callus ratio of the fracture, and biomechanical testing were performed. Biomechanically, stiffness and maximum stress were higher in dogs that received no carprofen than those that received 8 weeks. Radiographic healing scores were the same for dogs which did not receive carprofen and those receiving a short course, but both were more healed than dogs which received 8 weeks of carprofen. There was no treatment effect on cartilage:callus ratio or bone mineral density.

No description available.