Investigations into silicate-substituted hydroxyapatite (Si-HA) were performed. The aqueous precipitation method produced phase pure Si-HA with modi cations to the method causing impurities in the material. A novel study using Raman spectroscopy followed the behaviour of the silicate ions and provided a new interpretation regarding silicate substitution. The silicate ions created interactions with hydroxyl ions, initially, which reduced upon sintering of the material. As the silicate ions do not behave inde- pendently in the HA structure initially, suggests that these interactions may contribute to the bioactivity of Si-HA. Also industrial aspects of Si-HA were investigated regarding the silicate reagent (TEOS). A small di erence of 1% in the percentage concentration of TEOS was not negligible and caused a decrease in the amount of silicate substituted into HA. Di erent brands and grades of TEOS did produce Si-HA with similar structural properties. Therefore, a variety of brands and grades of TEOS can be used and thus the most cost e ective choice can be made. The rst analytical investigations into the molecular arrangement of fully mineralised osteoarthritic (OA) and osteoporotic (OP) bone were performed through small angle neutron scattering (SANS) studies. This study provided a description for the molecular arrangement of collagen molecules, along the lateral plane, regarding the molecular di- ameter and the packing of these molecules into the bril by the development of a model based on SANS theory. The collagen molecules behave like a 2-dimensional liquid-like system. Through the development of the model, the rst written solution for the struc- ture factor for a system of hard-disks was stated. This study provided an understanding into how collagen molecules are arranged in OA and OP bone. Also, compositional studies iterated possible di erences between the organic content of OA and OP bone. Thus the organic content of bone may play a role in the bone disorders.

Bone grafting is an integral part of reconstructive surgery. In the United States alone over 250,000 bone grafts were harvested annually. While autogenic bone grafting has always been associated with donor site morbidity, bone graft substitutes have been suggested as a solution. In this project, a bone graft substitute using human dental pulp cells (HDPCs) and peptide nanofibre hydrogel was being developed. HDPCs were isolated from extracted teeth. After culture and expansion, unsorted HDPCs were encapsulated into peptide nanofibre hydrogel. These cell-gel constructs were cultured for two weeks in ordinary culture medium and then for 2-3 more weeks in osteogenic lineage induction medium. The post-induced cell-gel derived constructs were transplanted into skin pouches or calvarial bone defects of nude mice. When transplanted subcutaneously, the cell-gel derived constructs were harvested at four to twelve weeks postoperatively (n=5). Tissue samples were processed for contact radiograph, histological examination and antibody staining. These constructs developed into vascularised, mineralised tissue pieces. Though bone marker proteins (osteopontin, osteocalcin and osteonectin) were detected in these tissue pieces, the histological structure of their tissue matrix did not resemble bone matrix. Later, it was accidentally noted that portions of constructs touching the bone defect margin, would form bone through direct matrix transformation. This indicated that the current cell-gel model was potentially the first study model of tissue engineering bone by simulating intramembranous ossification. In the bone defect trial, obviously mineralized cell-gel derived constructs of matching shape and size were selected to patch the 3mm calvarial bone defects (n=5). Bone defect specimens were harvested at two weeks post-operation. The development of radio-opaque structures within the bone defects were evaluated in virtual 3-dimensional models constructed with data collected by microtomographic scanning. The bone nature of these radio-opaque structure were validated histologically (by staining with Hematoxylin and Eosin, Periodic acid-Schiff stain and Picrosirius red) and immunologically (with antibody against human collagen-I, osteonectin and parathyroid hormone receptor). The radio-opaque structures developed into the bone defect were evaluated positive for bone. And significantly more bone regeneration was observed in the test group (n=4) than in the control (n=2). The mean area percentages of regeneration were 46.3% and 0% respectively (p< 0.05). While the majority of studies in bone tissue engineering have worked with bone marrow stromal cells and scaffolds of synthetic polymer or calcium based materials, this is the first successful attempt of using HDPCs and peptide nanofibre hydrogel to engineer bone (in a nude mice mode). And the potential of these cell-gel derived constructs to promote bone regeneration was demonstrated. But this was the result from a single experiment of small sample size in one animal model only. It needs to be fortified by further experiments with larger population size and in other animal models. To increase clinical usefulness, the construct will need to be scaled up to centimetre size level. This will necessitate a change of its configuration from bead into meshwork. And, the data collected to date will shed light onto the redevelopment of all the relevant protocols. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

Bone graft substitute is a continuously developing field in orthopedics. When compared to tradition biomaterial in the field such as PLA or PCL, elastomer like polyurethane offers advantages in its high elasticity and flexibility, which establish an intimate contact with surrounding bones. This tight contact can provide a stable bone-material interface for cell proliferation and ingrowth of bone. The aim of this study is to evaluate the osteogenesis capabilities of a porous polyurethane scaffold in a critical size bone defect. In this study, a porous scaffold synthesized from segmented polyurethane is put under in vitro and in vivo tests to evaluate its potential in acting as a bone graft substitute for critical size bone defects. In vitro results indicate osteoblast-like cells are proliferating on the polyurethane scaffold during the 21-days experiment. Cells express their normal morphology when seeded on polyurethane under fluorescent staining. Although cells show a relatively lower cell activity then that seeded on culture plate, they share a similar alkaline phosphatase activity profile with the controls during the experiment period. In the in vivo animal model, reconstructed images from micro CT scanning indicates there are bone ingrowth inside the scaffold. Histology also indicates a tight interface has formed between bone and polyurethane, with osteogenic cells proliferating on the surface. The result has indicates polyurethane is a potential material for orthopedics in acting as a bone graft substitute. / published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy

No description available.

Thesis (Ph. D.)--University of Alabama at Birmingham, 1997. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 1997. / Includes bibliographical references.

Silicon substituted hydroxyapatite (SiHA) has been reported to produce faster bone in- growth in vitro compared to hydroxyapatite (HA). The mechanism by which silicate ions in these materials trigger bone growth and differentiation remains unclear. In vitro models were used in this thesis to investigate human osteoblast cell responses on exposure to silicon containing materials and silicate ion solutions. The amounts of serum protein bound to SiHA was significantly higher than that in HA (p<O.OOl). Culture of both primary human osteoblast (HOB) cells and an osteosarcoma cell line (MG-63 cells) showed that SiHA discs were biocompatible to the cells; flat cell morphologies, higher degree of cellular processes, and a covering with minuscule bone mineral-like crystals were observed. To elucidate the effects of silicate ions alone on osteoblast functions, a 1000 ppm standard silicon solution was supplemented into cell culture medium to produce silicate ion concentration of 20 and 500 ~M; it was found that the former had little effect on both cell types. Significant increases in levels of total DNA (p<0.001), protein (p<0.001), and collagen (p<0.001) were observed in HOB cells, but not in MG-63 cells, in cultures with 500 ~M silicate ions. Likewise, expression of COL-J al (p<0.001), BMP-2 (p<0.05), PHOSPHO-J (p<0.001) genes were up-regulated in both cells types cultured with 500 ~M silicate ions. Further studies proposed that the activation of cell proliferation by this silicate ion-containing medium, observed as increases in total DNA, involved TGF~1 and/or IGF-I receptors. In trying to understand this, it was latterly identified that the pH changes of the serum- supplemented culture medium that occurred during supplementation with the alkali silicate ion solution and subsequent neutralisation with HCI were the actual cause of the marked enhancement in HOB cell proliferation. Silicate ions did still appear to have a direct effect on some HOB cell responses, due to observing comparable effects of 20 and 500 ~M silicate ions on e.g. TNAP and PHOSPHO-J gene expression, compared to silicate ion-free controls.

Orientador: Eduardo Hochuli Vieira / Coorientadora: Alessandra Marcondes Aranega / Banca: Roberta Okamoto / Banca: Idelmo Rangel Garcia Junior / Resumo: Objetivos: Comparar através de análise hitométrica e imunoistoquimica o comportamento do ChronOs® (β-TCP) e do Bio-Oss® (Osso bovino inorgânico ) puros e misturados ao osso autógeno na proporção 1:1 em seios maxilares de humanos. Metodologia: 30 pacientes foram convidados para participar deste trabalho, resultando em 30 seios enxertados com osso autógeno puro (grupo A (controle)), ChronOs® puro (grupo C), ChronOs® em adição de osso autógeno na proporção 1:1(grupo CA), Bio-Oss® puro (grupo B) e Bio-Oss® em adição de osso autógeno na proporção de 1:1 (grupo BA), onde foram realizadas biopsias 6 meses após a realização desses enxertos e analisadas através de histometria (analisadas através do software ImageJ) e imunoistoquimica (RUNX2, VEGF e Osteocalcina). Os resultados foram tabulados, o teste de Shapiro-Wilk foi aplicado para avaliação da normalidade, em seguida foram aplicado os testes Kruskal-Wallis e Anova 1 fator para os dados paramétricos e não paramétricos sucetivamente e o teste de Tukey como pós teste. Resultados: Para neoformação óssea o grupo A foi maior que os grupos B e BA e o grupo CA foi maior que o grupo BA (p<0,05). Para os remanescentes de biomateriais o grupo BA apresentou um número maior que os grupos Chronos C, CA e A (p<0,05). Para tecido mole o grupo C foi maior que o grupo B (p<0,05). O resultado das imunomarcações mostrou marcação fraca para RUNX 2 nos grupos A, C, B e BA e marcação moderada para o grupo CA. Marcação intensa para VEGF nos grupos B e CA ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Objectives: To compare the performance of ChronOs® (β - TCP) and Bio - Oss® (Inorganic bovine bone) pure and mixed with autogenous bone in a 1: 1 ratio in maxillary sinuses of humans through h i s tometric and immunohistochemical analysis. Metodology : 30 patients were invit ed to participate of this study, resulting in 3 0 grafted sinuses with pure autogenous bone (group A (control) ), pure ChronOs® (group C), ChronOs® in addition 1: 1 autogenous bone (group CA), pure Bio - Oss® (group B) and Bio - Oss® in addition 1: 1 (group BA), w h ich biopsies were performed 6 months after the grafting and analyzed by histology (analyzed using ImageJ software) and immunohistochemistry (RUNX2, VEGF and Osteocalcin). The results were tabulated, the Shapiro - Wilk test was applied to evaluate the normal ity, then the Kruskal - Wallis and Anova 1 tests were applied for the parametric and non - parametric data and Tukey test as post test was applied . Results: The group A was higher than B and BA groups, and the group CA was higher than the BA group (P <0.05). For the remainder of biomaterials, BA group presented a higher number than Chronos C, CA and A groups (P <0.05). For soft tissue, group C was greater than group B (P <0.05). The immunolabeling results showed poor labeling for RUNX 2 in groups A, C, B and B A and moderate labeling for CA group. Intense labeling 25 for VEGF in B and CA groups, moderate in groups A and C and weak in BA group . For Osteocalcin, there was an intense marking ... (Complete abstract electronic access below) / Mestre

Synthesis of chemically modified or ion-substituted hydroxyapatite (HA) as a bioactive bone replacement material is of great interest since the main component of hard tissues in vertebrates is a substituted apatite. The most abundant species in natural bone mineral other than calcium and phosphate ions is carbonate ions. Carbonate ions can be substituted at 2 distinct sites in the HA lattice; the hydroxide (OH) site and the phosphate (PO4) site. Synthetic silicate substituted HA (SiHA) and carbonate-substituted HA (CHA) have each previously been shown to enhance new bone formation when compared to HA in vivo. The positive bioactive properties that result, individually, from carbonate or silicate substitution led to the hypothesis that simultaneous co-substitution of these two ions in to the HA lattice would lead to further improved bioactivity. A range of novel silicate and carbonate co-substituted HA (SiCHA) materials were prepared with silicate substitution of up to 12.5 wt% (3.8 wt% Si) and carbonate substitution up to 8.2 wt%. These compositions were characterised extensively, examining both their chemical and physical attributes. These compositions were single phase after sintering in a wet CO2 atmosphere to near-theoretical density, and contained carbonate ions on both hydroxide and phosphate sites. The grain sizes of these ceramic specimens of these compositions were intermediate between those of CHA and SiHA controls. Further controlled synthesis demonstrated that carbonate and silicate ions could be substituted in non-equimolar quantities, and increased amounts of carbonate could be substituted independently on to the hydroxide site of the SiCHA samples. The biological response to these materials was assessed by completing direct and indirect cell culture experiments using both the MG-63 osteoblast-like cell line and primary human osteoblast (pHOB) cells. The silicate and carbonate co-substituted materials and their dissolution products were not toxic to either of the cell lines, and cell proliferation was observed with all materials studied. The effect of the synthesis route on the purity of silicate-substituted hydroxyapatite (SiHA) was also assessed, with a particular focus on the role of tetraethyl orthosilicate (TEOS) as the source of silicate. The outcomes of this study showed that the final composition of SiHA was strongly dependent on how and when the tetraethyl orthosilicate (TEOS) solution was incorporated during the precipitation reaction.