A clinical and laboratory investigation of synthetic materials to enhance healing and aid regenerative procedures in periodontal surgery

This study investigated the use of synthetic materials to enhance healing and to encourage regeneration of periodontal tissues after surgical therapy. The study was in two parts, a clinical investigation of the use of hydroxy-apatite implant material, and a laboratory investigation of biodegradable polymer membranes being developed for use as barrier membranes in the technique known as guided tissue regeneration. The aim of this study was to evaluate the efficacy of these materials in surgical wounds, to observe their limitations and to establish their potential to enhance regeneration of tissues. The hydroxy-apatite material was well tolerated by the tissues, but clinically significant benefits could not be established. Radiographically significantly more infill occurred in the sites which received the implant material, with some evidence of the material being modified with time so that the density and structure became more similar to that of the approximating host bone. Histological assessment of specimens from three individuals who were not in the clinical trial demonstrated resorption and osteoid formation over a longer time period. Both the radiographic and histological investigations indicated that there was a wide variation in the tissue responses to this material. The membrane materials were also well tolerated by the tissues, but a highly variable tissue response to them was also noted. Absorption of the biodegradable materials was irregular and unpredictable. The non-degradable Gore-Tex material was associated with prolonged inflammation, poor wound healing and epithelial downgrowth. It was therefore concluded that variable and unpredictable tissue responses occur in relation to these materials. The variations described were attributed to localised tissue responses, and individual site and host variations, rather than to the materials themselves. Other factors like the surface roughness, hydrophobicity or electrostatic surface changes of the materials may also be of importance. Although in general, for the clinical study, results were found to be equal to, or marginally better than control procedures, the enhancement of tissue regeneration using the synthetic implant materials or barrier membranes employed in this study to augment periodontal surgery is not entirely predictable

Sheep mandibular animal models for dental implantology research

Hardcopy of thesis in two volumes; digitized version in one PdfThis inquiry investigated the suitability of the jaw of domestic sheep as an animal model for dental implantology research. Initially, parameters for osseous healing of critical size defects (CSD) in the sheep mandible were established. Pilot studies were conducted using machined-surface implants and a surgical protocol established for dental implant placement in ovine mandibular sites. Subsequent experiments considered the utility of this animal model for examination of techniques designed to enhance osseointegration. Hydroxyapatite-coated implants were compared with titanium plasma-sprayed (TPS) implants, either alone or combined with autogenous bone grafts or a bone graft/collagen vehicle loaded with transforming growth factor-beta (TGF-B). Immunofluorescent bone labelling gave information on the mineral apposition rate (MAR). Implant survival and "acceptability" (likelihood of clinical success) were major output variables, along with histomorphometric analysis of percent bone-implant contact (%BIC) and percent peri-implant bone density (%density). Naturally-occurring "broken-mouth" periodontitis in sheep was identified as a potential confounder. Subsequent experiments considered implants with different surfaces. The model was also extended from a two-stage surgical protocol to include single-stage implants. The effect of pre-existing ovine peridontitis was also examined. A systematic review and meta-analysis of published animal implant experiments was conducted in order to validate the candidate sheep model. Major findings were as follows. The size of non-healing sheep mandibular unicortical CSD is > 12mm. Attempts to establish a chronic non-healing CSD were unsuccessful. The sheep diastema proved unsuitable for implant placement. The model was modified to a postextraction protocol. Implant "acceptability" rates after 3 months integration in the sheep mandible (defined as implant survival with %BIC >10%) ranged from 50% - 100% for different implant surface treatments and placement protocols. Histomorphometric analyses revealed that %BIC ranged from 11 ± 17% to 81 ± 29 % for different titanium surfaces and up to 85 ± 11 % for hydroxyapatite surfaces. Implants with TGF-B plus autogenous bone grafts had %BIC of 36 ± 30% compared with 43 ± 30% for implants with grafts alone. Bone per unit area (%density) adjacent to, but outside of the implant threads, ranged from 63 ± 16% to 86 ± 3% and was markedly lower for titanium plasma-sprayed surfaces and for one-stage implants. Within the implant threads, %density varied from 31 ± 33% to 73.4 ± 8.3%, and was markedly lower for machined titanium surfaces. Sheep periodontitis had little effect on the protocols investigated. The sheep mandibular model was found to be comparable to similar models in other species and merits further development

Development of Jetting Techniques for the Delivery of Mesenchymal Stromal Cells for Therapeutic Applications

Mesenchymal stromal cells (MSC) are an important cell source for tissue engineering and regenerative medicine (TERM) and cell therapies. Intravenous injections (I.V.) injections and scaffold implantation are currently the predominant methods of MSC administration. However, both approaches have encountered serious problems for example with I.V. injections, cells can move through the blood stream to any site in vivo provoking problems such as MSC entrapment, and failure to target the injury site. For tissue engineering (TE) applications administration of MSC to a target area include the fabrication of artificial three dimensional (3D) constructs. However, the synthesised environments of these 3D constructs have been associated with numerous limitations including, poor cellular responses, lack of cell infiltration and limited access to essential nutrients and oxygen through the scaffolds. Therefore, the overall aim of the study is to address obstacles associated with MSC administration from either I.V. injections or scaffold transplantation, by using a jetting methodology called bio-electrospraying (BES) to deliver cells directly to an injured region. A major difficulty associated with BES is reproducibility of data between different labs. This is due to the type of apparatus used as electrospray devices tend to be built “in-house”, which adversely affects reproducibility of parameters, including flowrate, potential difference (PD) and voltages. To overcome these problems we used Spraybase®, a commercially available electrospray apparatus. We aimed to establish optimised “gold standard” parameters, for a commercial electrospray instrument that would allow reproducibility between experiments/labs and/or medical environments. By modifying the shape of the ground electrode component, the commercial electrospray was transformed into a fully functional electrospinning device. 3D constructs were fabricated using our own blends of polymer mixtures involving PEO, collagen and agarose. Two distinct sets of electrospun fibres were examined in relation to surface texture, pore and fibre size. These preliminary results may benefit future applications for TE either/or by using our polymer hybrids, electrospinning apparatus and functional parameters. Finally, the BES technique was developed further to make it more clinically applicable. To achieve this, the jetting process was first explored to investigate its affects on mouse bone-derived mesenchymal stromal cells (mBMSC) at a cellular and immunological level. Known characterisations of MSC, i.e. expression of specific surface markers, suppression of T- cell activation, multilineage differentiation, and the pro-reparative properties were analysed for BES BMSC. It was determined that BES BMSC behaved similar to their non-BES counterparts in all biological aspects. The commercial electrospray was then modified to include a specially designed catheter with single needle configuration attached. This catheter fits all types of endoscopes suitable for keyhole surgeries. The only adjustment to the previous established BES parameters was to the flowrate. This was to accommodate the length fluid/cells had to travel through the catheter. We assessed if the optimized parameters were effective with the catheter by BES mBMSC onto 3D collagen-Glycosaminoglycan (CG) scaffolds, and allowing them to differentiate into chondrocytes. The results from this study indicated mBMSC remained fully functional and differentiated as normal after 21days on the scaffolds. To determine if the spray from the catheter was reaching the intended target site, differentiated chondrocytes were BES to a specific area on the scaffolds. Analysis showed chondrocyte staining only at the targeted area. These results also demonstrated huge potential for cartilage regenerative therapies. BES chondrocyte cells to an injured region using arthroscopy with this catheter can eliminate issues with immune rejection caused by scaffolds, or issues with the scaffolds themselves (mentioned above). Delivering specific number of MSC and/or other cell types directly to a specific tissue injury site, using the modified commercially available electrospray apparatus, with optimised parameters including low voltages, has revolutionised MSC delivery for therapeutic applications. This set up can potentially eliminate the complications associated with MSC entrapment, while limiting the need for artificial scaffolds in TE

Human Teeth

This book provides information on nomenclature, tooth numbering systems, tooth morphology, and anatomy and stages of tooth formation. It continues with root canal morphology and anatomy of incisors, canines, premolars, and molars. External and internal anatomies of mandibular permanent incisors and maxillary permanent first molars are presented according to a literature review. Orofacial structures affecting tooth morphology are discussed in detail. The book ends with the evolution of dental implant shapes and today�s custom root analog implants

An investigation into 3D printing of osteological remains: the metrology and ethics of virtual anthropology

Three-dimensional (3D) printed human remains are being utilised in courtroom demonstrations of evidence within the UK criminal justice system. This presents a potential issue given that the use of 3D replicas has not yet been empirically tested or validated for use in crime reconstructions. Further, recent movements to critically evaluate the ethics surrounding the presentation of human remains have failed to address the use of 3D printed replica bones. As such, this research addresses the knowledge gap surrounding the accuracy of 3D printed replicas of skeletal elements and investigates how the public feels about the use of 3D printed replicas. Three experimental studies focussed on metrology and identified 3D printed replicas to be accurate to within ± 2.0 mm using computed tomography (CT) scanning, and to within ± 0.2 mm or to 0-5% difference using micro-CT. The potential loss of micromorphological details was also examined and identified that quality control steps were key in identifying and mitigating loss of detail. A fourth experimental study collected data on the opinion of the public of the use of 3D printed human remains in courtroom demonstrations. Respondents were broadly positive and considered that prints can be produced ethically by maintaining the dignity and respect of the decedent. A framework that helps to assess ethical practices was developed as well as an adaptable pathway that can assist with assessing the quality and accuracy of 3D prints. The findings from this research contribute to an empirical evidence base that can underpin future 3D printed crime reconstructions and provides guidance for creating accurate 3D prints that can inform future practice and research endeavours

2014 - 2015 University Catalog

This is a one-year Catalog, effective beginning Summer Quarter 2014. Volume 104, Number 1, July 2014https://scholarsrepository.llu.edu/univcatalog/1002/thumbnail.jp