Includes bibliographical references.

Bibliography: leaves 157-177.

Background and objectives: The most widely accepted tooth movement model is defined by the pressure-tension hypothesis. An orthodontic force applied to a tooth generates areas of compression and tension in the periodontal ligament (PDL), which are transmitted to the alveolar bone. Areas of tissue exposed to tensile strain undergo bone deposition, whereas areas of tissue exposed to compressive strain undergo bone resorption. We propose that human PDL cells in monolayer culture exposed to tensile mechanical strain would express multiple genes involved in osteogenesis. Materials and Methods: Human PDL cells were isolated and cultured from premolar teeth that were extracted for orthodontic reasons. These cells were plated on control and experimental Uniflex[TM] plates. Using a Flexercell FX4000 strain unit, PDL cells on experimental plates were exposed to a 12% uni-axial cyclic strain for 6 seconds out of every 90 seconds over a 24 hour period. RNA was extracted from the PDL cells at 6 hours, 12 hours and 24 hours. The differential expression of 78 genes implicated in osteoblast differentiation and bone metabolism was analysed using real-time reverse transcriptase polymerase chain reaction (RT-PCR) array technology. Results: Of the 78 genes tested, sixteen genes showed statistically significant (p<0.05) changes in expression in response to the mechanical strain regime. Eight genes were up-regulated (ALPL, BMP2, BMP6, COL2A1, ICAM1, PHEX, SOX9, and VEGFA) and eight genes were down-regulated (ANXA5, BMP4, COL11A1, COL3A1, EGF, ITGB1, MSX and SMAD1). Conclusions: This study has demonstrated that cultured human PDL cells express multiple osteogenic genes under tensile strain, which suggests that PDL cells may have a potential role in osseous remodeling during tooth movement. Key Words: Tooth movement, human PDL cells, tensile mechanical strain, osteogenic genes, real-time RT-PCR array, and Flexercell FX4000.

As a logical extension of previous work conducted into viscoelastic atomization, initially motivated by the need to improve spray coating transfer efficiencies, an experimental investigation into the spray-surface interaction for a number of Newtonian and non-Newtonian substitute test liquids is presented. Three model elastic liquids of varying polymer molecular weight and three inelastic liquids of varying shear viscosity were sprayed upon a moving surface to isolate the effect of elasticity and shear viscosity, respectively, on spray impaction behavior. In addition, two liquids exhibiting shear thinning behavior and an industrial top of rail liquid friction modifier, KELTRACK, for use in the railroad industry, were included in the spray tests. High-speed photography was used to examine the impingement of these liquids on the surface. Ligaments, formed as a consequence of a liquid’s viscoelasticity, were observed impacting the surface for 300K PEO, 1000K PEO, and KELTRACK. These ligaments were broadly classified into four groups, based on their structure. Splashing of elastic liquid ligaments and droplets led to filamentary structures being expelled from the droplet periphery, which were then carried away by the atomizing air jet, leading to reductions in transfer efficiency. The effect of increasing elasticity amongst the three varying molecular weight elastic solutions was shown to increase the splash threshold; a similar effect was noted with increasing shear viscosity. Attempts were made at quantifying a critical splash-deposition limit for all test liquids however due to imaging system limitations, no quantitative conclusions could be made. For KELTRACK, both droplets and ligaments spread and deposited on the rail surface upon impact, with no observed splash or rebound. Splash was only noted when droplets impinged directly on a previously deposited liquid film and even then, splashing was well contained. Thus, KELTRACK’s current rheological formulation proved to be very effective in ensuring high coating transfer efficiencies.

As a logical extension of previous work conducted into viscoelastic atomization, initially motivated by the need to improve spray coating transfer efficiencies, an experimental investigation into the spray-surface interaction for a number of Newtonian and non-Newtonian substitute test liquids is presented. Three model elastic liquids of varying polymer molecular weight and three inelastic liquids of varying shear viscosity were sprayed upon a moving surface to isolate the effect of elasticity and shear viscosity, respectively, on spray impaction behavior. In addition, two liquids exhibiting shear thinning behavior and an industrial top of rail liquid friction modifier, KELTRACK, for use in the railroad industry, were included in the spray tests. High-speed photography was used to examine the impingement of these liquids on the surface. Ligaments, formed as a consequence of a liquids viscoelasticity, were observed impacting the surface for 300K PEO, 1000K PEO, and KELTRACK. These ligaments were broadly classified into four groups, based on their structure. Splashing of elastic liquid ligaments and droplets led to filamentary structures being expelled from the droplet periphery, which were then carried away by the atomizing air jet, leading to reductions in transfer efficiency. The effect of increasing elasticity amongst the three varying molecular weight elastic solutions was shown to increase the splash threshold; a similar effect was noted with increasing shear viscosity. Attempts were made at quantifying a critical splash-deposition limit for all test liquids however due to imaging system limitations, no quantitative conclusions could be made. For KELTRACK, both droplets and ligaments spread and deposited on the rail surface upon impact, with no observed splash or rebound. Splash was only noted when droplets impinged directly on a previously deposited liquid film and even then, splashing was well contained. Thus, KELTRACKs current rheological formulation proved to be very effective in ensuring high coating transfer efficiencies.

Bakgrund: Behandlingen av Mediala collateral ligament (MCL) skador är debatterad. En skada på MCL kan leda till sämre medial stabilitet och nedsatt aktivitetsförmåga. Målet med den konservativa behandlingsformen är att minska svullnad och smärta för att på så vis få tillbaka full rörlighet och stabilitet. Behandlingen innebär ofta någon form av öppen eller låst ortos tillsammans med ett rehabiliteringsprogram. Syftet: Syftet med studien är att utifrån litteraturen analysera studiernas bevisvärde och beskriva konservativa behandlingsmetoder för MCL, med öppna och låsta ortoser tillsammans med träning. Metod: En litteraturstudie användes, då syftet var att göra en beskrivning av kunskapsläget. Artikelsökningen resulterade i 13 inkluderade studier. För att bestämma bevisvärde för studierna användes en granskningsmall av Carlsson och Eiman (2003) och Statens beredning för medicinsk utvärderings punkt om studiedesign. Resultat: Studierna fick bevisvärden från lågt - mycket lågt. Efter analys av de inkluderade studierna framkom att den mediala knästabiliteten uppvisade ett varierat resultat i båda grupperna med öppen och låst ortos. Dock återgick de flesta patienter till sin tidigare aktivitetsförmåga efter behandlingarnas slut. Slutsats: Av litteraturstudien kan inga slutsatser dras gällande i vilken utsträckning den mediala knästabiliteten och aktivitetsförmågan förändrats efter konservativ behandling med öppen respektive låst orts tillsammans med träning. Studiernas låga bevisvärde och varierade behandlingsmetoder inom låst respektive öppen ortos försvagar slutsatsen ytterligare.

An estimated 200,000 injuries to the anterior cruciate ligament (ACL) occur annually in the United States, with approximately 100,000 total ACL reconstructions performed each year. Due to inherent limitations with existing ACL reconstruction strategies, the development of tissue engineered ligaments is a key area of musculoskeletal research. Although great strides have been made in the scaffold design, current strategies are limited by the inability to replicate the mechanical behavior of native ligament tissue with synthetic polyesters or natural polymers. Poly(ester urethane)s have recently been investigated as possible scaffold materials because of their established biocompatibility, excellent mechanical properties, and exceptionally tunable structure. However, non-specific degradation makes it difficult to tailor polyurethane structure to complement ligament regeneration. In contrast, a biomaterial that features system-responsive degradation would integrate with native ligament remodeling and thus provide effective load transfer to newly formed tissue that is necessary to restore mechanical integrity. In this study, enzyme-labile peptide sequences were conjugated to ether-based polyols to form collagen-mimetic soft segments that feature cell-responsive degradation. Synthetic routes were first developed to functionalize these polyols with favorable end groups for peptide coupling. Upon successful conjugation, biodegradable soft segments were then incorporated into the structure of linear polyurea elastomers. By varying soft segment chemistry, soft segment molecular weight, and the hard to soft segment ratio, a library of cell-responsive, biodegradable polyureas was developed. This library can then be used to elucidate key structure-property relationships necessary to complement neotissue formation. Overall, synthesis of a novel biomaterial that combines the strength and tunability of synthetic elastomers with cell-responsive degradation will assist in the development of an improved tissue engineered graft for ACL reconstruction.

Reproduction de : Thèse d'exercice : Médecine vétérinaire : Toulouse 3 : 2008. / Titre provenant de l'écran titre. Bibliogr. f. 128-133.

Dissertation (Ph.D.)--University of Toledo, 2009. / "In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biomedical Sciences." Title from title page of PDF document. Bibliography: p. 128-144.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Biomedical Engineering." Includes bibliographical references (p. 102-113).