Objectives: To compare the osseointegration of conventionally and immediately restored tapered implants in a split-mouth animal model, and to compare different methods of analysis for measuring osseointegration. Materials & Methods: Twenty tapered implants were placed in the posterior mandibles of ten sheep, three months after premolar extractions. Ten control implants were placed and were restored after three months submerged healing. Ten test implants were placed on the contralateral side at this time and immediately restored. Animals were sacrificed after a further three months healing. Resonance frequency analysis (Implant Stability Quotient, ISQ), and standardized radiographs were taken at all stages. Alveolar bone height relative to the implant shoulder was measured on digitized radiographs. Histomorphometric and micro-Computed Tomograph ([mu]CT) morphometric analysis for Bone-to-Implant Contact (BIC) and Bone Density (BD) were performed. Radiographic, stability and morphometric measurements were compared statistically. Results: Only three (30%) of conventionally restored and two (20%) immediately restored implants survived (p = 0.74). Mean crestal bone level after three months loading differed significantly (control 5.3 � 0.9 mm versus test 0.9 � 1.3 mm; p = 0.02). Control implants lost more crestal bone over three months than test implants but this was not statistically significant (3.5 � 1.0 mm versus 0.7 � 1.0 mm; p = 0.06). The test group showed a higher mean ISQ value (85.4 � 6.9) compared to the control group (72 � 14.4; p = 0.349). Both groups showed a slightly reduced stability during the loaded period. This was more marked for the test group but not statistically significant (-0.5 � 3.8 ISQ versus -4.35 � 6.6 ISQ; p = 0.8). A statistically significant negative correlation was found between the loss of crestal bone and ISQ with loading (Pearson�s coefficient of correlation r = -0.473 p = 0.026). Both groups showed a statistically significant difference in BIC for both histomorphometric analaysis (HMA); p = 0.039 and [mu]CT morphometric analysis; p = 0.013. When the two forms of morphometric analysis were compared, HMA and [mu]CT morphometric analysis differed significantly for both BIC (p = 0.05) and BD (p = 0.048). However, a statistically significant correlation was found between the two measuring techniques, for both BIC (r = 0.335 p = 0.013) and BD (r = 0.439 p = 0.01). Conclusions: The placement of wide-bodied 3i Osseotite NT[TM] tapered implants into sheep mandible resulted in high failure rate regardless of the loading protocol. The sheep mandibular model may be inappropriate as a model for evaluation of immediate loading, and to test implants which are designed for soft bone. Further investigations are needed to look into the variations in bone microstructure along with their impact on the mechanics of implant-bone union. Although a statistically significant difference was found between the two measurement techniques, a positive correlation was found between HMA and [mu]CT morphometric analysis suggesting non-invasive methods may have a potential in assessing osseointegration. Further research is required to optimize the variables in [mu]CT analysis, such as, voltage, filters, and thresholding to minimize artifacts and to maximize bone contrast when titanium implants are present.

Rationale/ Hypothesis: Reactive oxygen species, including lipid hydroperoxides, play a critical role as second messengers in many physiological processes in the body. Heightened reactive oxygen species production at the time of birth imposes an oxidative stress upon the lung, which may trigger postnatal alveologenesis and physiological lung cell apoptosis in the neonatal rat. Methods: Neonatal rats were subcutaneously injected daily with vehicle (corn oil) or diphenyl-phenyl diamine for the first 6 days of life to study alveologenesis and physiological lung cell apoptosis. Add-back experiments were conducted with a prototypic lipid hydroperoxide, t-butyl hydroperoxide. Main Results: Treatment with diphenyl-phenyl diamine resulted in parenchymal thickening, reduced numbers of secondary crests and enlarged air spaces, all consistent with the inhibition of alveologenesis and reduced physiological lung cell apoptosis. Conclusion: Following an oxidative stress at birth, lipid hydroperoxide formation triggers postnatal alveologenesis and physiological lung cell apoptosis in the neonatal rat.

Rationale/ Hypothesis: Reactive oxygen species, including lipid hydroperoxides, play a critical role as second messengers in many physiological processes in the body. Heightened reactive oxygen species production at the time of birth imposes an oxidative stress upon the lung, which may trigger postnatal alveologenesis and physiological lung cell apoptosis in the neonatal rat. Methods: Neonatal rats were subcutaneously injected daily with vehicle (corn oil) or diphenyl-phenyl diamine for the first 6 days of life to study alveologenesis and physiological lung cell apoptosis. Add-back experiments were conducted with a prototypic lipid hydroperoxide, t-butyl hydroperoxide. Main Results: Treatment with diphenyl-phenyl diamine resulted in parenchymal thickening, reduced numbers of secondary crests and enlarged air spaces, all consistent with the inhibition of alveologenesis and reduced physiological lung cell apoptosis. Conclusion: Following an oxidative stress at birth, lipid hydroperoxide formation triggers postnatal alveologenesis and physiological lung cell apoptosis in the neonatal rat.

THESIS SUMMARY:GENERAL AIMThe general aim of this thesis was to study the generation of contractile force by human alveolar epithelial cells in culture in response to biochemical or mechanical stimuli using traction microscopy.SPECIFIC AIMS1. To implement a traction microscopy setup to measure the contractile force generated by human alveolar epithelial cells in culture.1.1. To implement and validate a software to determine the deformation field induced by adhered cells on the elastic substrate, following previously described algorithms.1.2. To implement and validate a software to determine the traction field induced by adhered cells and other contractility parameters, following previously described algorithms.1.3. To implement a software to determine the contour of an adhered cell from a brightfield or phase contrast image of the cell.2. To study the contractile response of human alveolar epithelial cells in response to thrombin.2.1. To determine the gel substrate conditions and gel fabrication procedure which enable suitable cell culture and optimal detection of traction forces exerted by human alveolar epithelial cells. These gel conditions include: concentration of polyacrilamide gel components to provide optimal gels stiffness; concentration of fluorescent beads to optimally compute gel deformation; and suitable gel coating to enable cell attachment.2.2. To determine the gel elastic properties (Young's modulus) by atomic force microscopy.2.3. To measure the time-course of the contractile response to thrombin challenge.2.4. To study the distribution of contractile forces exerted by adhered cells before and after thrombin stimulation.2.5. To measure actin polymerization and reorganization induced by thrombin challenge.2.6. To study the role of the actin cytoskeleton in the contractile response to thrombin by pre-treatments with cytochalasin D.2.7. To study the role of pathways signalling MLC phosphorilation in the contractile response to thrombin by pre-treatments with ML7 and Y-27632.3. To study the contractile response of human alveolar epithelial cells subjected to stretch.3.1. To determine a suitable gel substrate that firmly attaches to a flexible membrane, allowing biaxial stretch application (max ~15%) and cell culture.3.2. To determine the gel elastic properties (Young's modulus) of the gel at different strain levels by atomic force microscopy.3.3. To implement and validate a stretching device to apply controlled biaxial and uniform strains to cultured cells and simultaneously measure contractile forces by deforming the gel substrate to which they are adhered.3.4. To adapt the existing traction microscopy algorithms and software to allow computation of large bead displacements (~20 μm) and corresponding stretch fields.3.5. To measure contractile forces exerted by human alveolar epithelial cells before, during and after being subjected to a stepwise deformation of up to 11.5% linear strain.3.6. To assess the role of actin polymerization in the contractile response to stretch.3.7. To assess the role of actomyosin crossbridges attachment or detachment in the contractile response to stretch.3.8. To assess temporal changes in cell contractility after stretch release. / "Estudi de la contracció de cèl·lules epitelials alveolars en resposta a estímuls inflamatoris i de deformació mitjançant microscopia de tracció"TEXT:L'epiteli alveolar forma una barrera cel·lular semipermeable entre l'espai alveolar i l'interstici del pulmó, permetent l'intercanvi gasós a la vegada que restringeix el pas de líquid, macromolècules i cèl·lules cap a l'alvèol. El trencament de la monocapa, degut a la formació de forats entre cèl·lules adjacents, pot donar lloc a l'augment de la permeabilitat i l'entrada de líquid a l'alvèol, característics del dany pulmonar agut. La integritat de la monocapa epitelial es regeix per un equilibri dinàmic de forces als punts d'unió cèl·lula-cèl·lula, i cèl·lula-matriu. Les forces en joc es divideixen en una component de tensió centrípeta i una component d'adhesió centrífuga. La component centrípeta es deguda a les forces de contracció generades activament per la maquinària contràctil cel·lular i el retrocés passiu degut a la deformació cíclica a la que es troben sotmeses les cèl·lules alveolars durant la respiració. Per tal de garantir la integritat de la monocapa, les forces d'adhesió han de ser capaces de contrarestar la tensió centrípeta. L'equilibri de forces als punts d'unió pot veure's compromès degut a estímuls inflamatoris o bé mecànics.El projecte de tesi es centra en el paper de les forces actives de contracció sobre la integritat de la monocapa alveolar en resposta a estímuls característics del dany pulmonar agut. Per tal d'estudiar aquesta component contràctil, el present projecte ha utilitzat la microscopia de tracció. Aquesta tècnica permet mesurar la força que cèl·lules adherents aïllades realitzen sobre el seu substrat, així com la seva distribució espaial i evolución temporal. La tècnica consisteix en cultivar cèl·lules adherents sobre substrats elàstics que contenen microesferes fluorescents. Comparant la posició de les microesferes quan la cèl·lula es troba adherida al substrat i un cop aquesta ha estat desenganxada amb tripsina, podem calcular la força que la cèl·lulaadherent realitzava sobre el substrat.El projecte de tesi inclou dos estudis concrets, dedicats a dos estímuls característics de dany pulmonar agut als qual poden trobar-se sotmeses les cèl·lules epitelials alveolars. El primer estudi (secció 3) es centra en l'efecte que el mediador inflamatori trombina provoca sobre la realització de forces contràctils per part de cèl·lules alveolars epitelials. El segon estudi (secció 4) es centra en la resposta contràctil de cèl·lules alveolars epitelials a l'aplicar deformacions externes, simulant les condicions de respiració mecànica que requereixen molts pacients amb dany pulmonar agut.

Real time detection of Volatile Organic Compounds (VOCs) using Selected Ion Flow Tube – Mass Spectrometry (SIFT-MS) provides a unique opportunity for research into breath testing for clinical diagnosis. However, before engaging in research into breath analytes as markers of disease, appropriate breath collection methods are required. Collection of breath for SIFT-MS instruments fall into two categories, direct breath collection into the instrument and the remote breath collection onto a storage medium. This thesis describes the development and validation of both methods of breath collection equipment for SIFT-MS analysis. Development of the direct breath collection device involved standardising and optimising the way in which breath is sampled by SIFT-MS. Design considerations include ergonomics, patient safety, breathing resistance, materials, and appropriate operating conditions of the device. Results from materials testing showed that all materials emit VOCs and the best approach is to minimise VOC emission by careful material selection. To minimise flow resistance experienced by the patient, the capillary from which the SIFT-MS instrument samples, is placed as close as possible to the users mouth. The optimal operating temperature of the device was found to be 100°C - 120°C, which ensures that water vapour will not condense inside the capillary causing blockage. In order to ensure patient safety the device is adequately insulated using stagnant air which also minimises VOC emission from insulation materials. Because a SIFT-MS instrument is large and cannot be easily shifted around a hospital, a system of remote sample collection is required. It is also important to separately collect and analyse breath from the respiratory alveolar region. For this reason the remote breath collection device designed also fractionates collected breath samples into the breath from the upper airways and alveolar breath. The storage medium chosen for the collected breath samples is a gas sampling bag made from Tedlar™. Collection of breath into Tedlar™ bags allows breath to be stored as a whole air sample, the ideal form for analysis with the SIFT-MS technique. Alveolar breath is fractionated from deadspace gasses by measuring a subject's exhalation and collecting the portion of interest. The breath exhalation is measured by an averaging Pitot tube and pressure transducer. Signal processing and automation of the remote breath collection device is controlled by a Cypress Microsystems PSoC microcontroller. To validate the device isoprene and acetone concentrations in fractionated breath samples were compared with a whole breath sample. Results showed that the alveolar breath fraction had a higher concentration of acetone than the upper airway fraction, indicating that the breath was successfully fractioned. However, isoprene concentrations were lower in both fractions due to hyperventilation of the subject causing a dilution effect of alveolar VOCs. Therefore, a higher sample collection volume is required per exhalation, and regulating subjects' breathing rate will avoid the dilution effect observed in collected breath samples. Overall, this thesis had designed, developed and validated two forms of breath collection systems for use with SIFT-MS technology.

Objectives: To compare the osseointegration of conventionally and immediately restored tapered implants in a split-mouth animal model, and to compare different methods of analysis for measuring osseointegration. Materials & Methods: Twenty tapered implants were placed in the posterior mandibles of ten sheep, three months after premolar extractions. Ten control implants were placed and were restored after three months submerged healing. Ten test implants were placed on the contralateral side at this time and immediately restored. Animals were sacrificed after a further three months healing. Resonance frequency analysis (Implant Stability Quotient, ISQ), and standardized radiographs were taken at all stages. Alveolar bone height relative to the implant shoulder was measured on digitized radiographs. Histomorphometric and micro-Computed Tomograph ([mu]CT) morphometric analysis for Bone-to-Implant Contact (BIC) and Bone Density (BD) were performed. Radiographic, stability and morphometric measurements were compared statistically. Results: Only three (30%) of conventionally restored and two (20%) immediately restored implants survived (p = 0.74). Mean crestal bone level after three months loading differed significantly (control 5.3 � 0.9 mm versus test 0.9 � 1.3 mm; p = 0.02). Control implants lost more crestal bone over three months than test implants but this was not statistically significant (3.5 � 1.0 mm versus 0.7 � 1.0 mm; p = 0.06). The test group showed a higher mean ISQ value (85.4 � 6.9) compared to the control group (72 � 14.4; p = 0.349). Both groups showed a slightly reduced stability during the loaded period. This was more marked for the test group but not statistically significant (-0.5 � 3.8 ISQ versus -4.35 � 6.6 ISQ; p = 0.8). A statistically significant negative correlation was found between the loss of crestal bone and ISQ with loading (Pearson�s coefficient of correlation r = -0.473 p = 0.026). Both groups showed a statistically significant difference in BIC for both histomorphometric analaysis (HMA); p = 0.039 and [mu]CT morphometric analysis; p = 0.013. When the two forms of morphometric analysis were compared, HMA and [mu]CT morphometric analysis differed significantly for both BIC (p = 0.05) and BD (p = 0.048). However, a statistically significant correlation was found between the two measuring techniques, for both BIC (r = 0.335 p = 0.013) and BD (r = 0.439 p = 0.01). Conclusions: The placement of wide-bodied 3i Osseotite NT[TM] tapered implants into sheep mandible resulted in high failure rate regardless of the loading protocol. The sheep mandibular model may be inappropriate as a model for evaluation of immediate loading, and to test implants which are designed for soft bone. Further investigations are needed to look into the variations in bone microstructure along with their impact on the mechanics of implant-bone union. Although a statistically significant difference was found between the two measurement techniques, a positive correlation was found between HMA and [mu]CT morphometric analysis suggesting non-invasive methods may have a potential in assessing osseointegration. Further research is required to optimize the variables in [mu]CT analysis, such as, voltage, filters, and thresholding to minimize artifacts and to maximize bone contrast when titanium implants are present.

This study used Backscattered electron imaging (BSE) and X-ray Microanalysis to qualitatively and quantitatively investigate morphology and elemental composition of ankylotic adaptation in the periodontium following hypothermic insult to their maxillary first molars. This method has been shown in previous studies to induce aseptic root resorption along with ankylotic changes within the periodontal ligament (PDL). A secondary objective was to assess the pulpal changes that occurred concurrent with the changes in the periodontium. Twenty-eight eight week old Sprague Dawley rats were divided into four groups of seven animals corresponding to one of four observation periods i.e.: t₁= 7 days, t₂= 14 days, t₃= 21 days, t₄ = 28 days. At t=0 days, six animals in each group received a thermal insult as a continuous 20 minute application of dry ice (CO₂ at -81⁰C) to the crowns of their upper right maxillary molar. The untreated left molars were used as controls. The remaining rat within each group did not receive the dry ice. All rats were given two sequential bone labels, calcein 5mg/kg and alizarin red 30mg/kg, administered intraperitoneally 8 days apart. The timing of the labels was such that all rats were euthanased 2 days after the last label. Following sacrifice, the maxillae were dissected out, fixed in ethanol and embedded in methylmethacrylate. Ten microns thick, undecalcified maxillary first molar coronal sections through the furcation were obtained. For every 3 out of 10 sections: the first was left unstained and undecalcified; the second stained with Von Kossa/haematoxylin & eosin; and the third decalcified and stained with haematoxylin & eosin. Unstained sections were viewed under fluorescence, while transmitted light microscopy was used for the other sections. Following initial analysis, the unstained, undecalcified sections were de-coverslipped and carbon coated. These sections were investigated with scanning electron microscopy and Energy Dispersive X-ray Spectrometry (EDS). Quantitative spot analysis and element mapping was performed on alveolar bone, ankylotic areas, cementum and dentine. A linear mixed effects model was employed to investigate any interaction between the four tissues of interest. A focal pattern of ankylosis was observed at days 14 and 21 in three rats. No ankylosis was observed in the control teeth. SEM revealed a focal type of ankylosis with central nodules of mineralized tissue forming within the PDL. Bridging between bone and dentine occurred with fine trabeculae which extended from the central mineralized nodule. Bridging was progressive and was more extensive at day 21 compared to day 14. At day 28, no ankylosis was observed. EDS analysis revealed that the ankylotic tissue was composed of major constituents Calcium and Phosphorous along with trace elements of Mg and Na. This was comparable to the surrounding alveolar bone, cementum and dentine. There was no statistically significant difference in the Ca/P ratios, Mg when ankylotic material was compared to bone. There was a trend towards elevated Na levels in ankylosis but this was not statistically significant relative to bone. Mg in dentine was lower than for all the other tissues and Na was higher in dentine when compared to bone and cementum. In the pulp, hypothermic injury demonstrated alteration of the odontoblast layer, reduction in cellularity, vascular alterations and tertiary dentin formation. At the 28 day observation period, the cellular and vascular changes had returned to levels comparable to the control teeth, indicating successful pulpal healing and regeneration. Marked tertiary dentine deposition was also observed at days 14, 21 and 28. Pulp chambers were visibly smaller due to tertiary dentine formation, however no pulp necrosis was observed. Thus the aseptic root resorption model, using a continuous 20 minute application of dry ice, suggested the occurrence of reversible pulpal tissue alterations compatible with an inflammatory repair process. The observation of ankylosis initiating as centralised nodules within the PDL suggest that the origins may be a consequence of osteogenic potential from PDL stem cells. The null hypothesis that a single, prolonged thermal insult on a rat molar does not have an effect on mineralized tissue formation and that ankylotic tissue is similar to bone was rejected. ABSTRACT There is a presumption that the ankylotic region formed after periodontal ligament (PDL) injury represents an unremarkable bony repair process. Essentially, the injury triggers an osteogenic repair response and the ankylotic tissue merely represents alveolar bone. There is uncertainty whether the oestogenic event is predominantly osteoblast driven, cementoblast directed, or a consequence of osteogenic potential from PDL stem cells. In this study, twenty-eight Sprague Dawley rats were divided into four groups of six animals, corresponding to one of four observation periods, and received a thermal insult as a continuous 20 minute application of dry ice to the crowns of their upper right maxillary molar. The appearance of ankylotic tissues was examined using backscattered electron images using a scanning electron microscope (SEM) equipped with an Energy Dispersive X-ray Analyser (EDS). The Ca, P, and trace elements contents were determined by EDS from four different hard tissue regions: ankylosis; bone; dentine and cementum, and the Ca/P ratios were calculated. Ankylosis was observed at days 14 and 21 in 3 rats and was not seen at day 28. No ankylosis was observed in the control teeth. BSE imaging revealed a focal type of ankylosis with central nodules of mineralized tissue forming within the PDL. The morphological features of ankylotic tissue differed to that of alveolar bone and dentine. Bridging between bone and dentine occurred with fine trabeculae which extended from the central mineralized nodule. EDS analysis showed that the ankylotic tissue was composed of major constituents Ca and P along with trace elements of Mg and Na. This was comparable to the surrounding alveolar bone, cementum and dentine. There was no statistically significant difference in the Ca/P ratios, Mg, and Na between ankylotic material and bone. Statistically significant differences was evident in Mg content between ankylotic material compared to dentine and cementum. Na content was higher in dentine than in ankylotic material. The results of this study indicate that, histochemically, ankylotic material is similar to bone. However, the appearance of ankylotic material as centralised foci with a morphology different from bone suggest that ankylosis may originate from an osteoblastic phenotype originating within PDL. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1522156 / Thesis (D.Clin.Dent.) -- University of Adelaide, School of Denstistry, 2010

This study used Backscattered electron imaging (BSE) and X-ray Microanalysis to qualitatively and quantitatively investigate morphology and elemental composition of ankylotic adaptation in the periodontium following hypothermic insult to their maxillary first molars. This method has been shown in previous studies to induce aseptic root resorption along with ankylotic changes within the periodontal ligament (PDL). A secondary objective was to assess the pulpal changes that occurred concurrent with the changes in the periodontium. Twenty-eight eight week old Sprague Dawley rats were divided into four groups of seven animals corresponding to one of four observation periods i.e.: t₁= 7 days, t₂= 14 days, t₃= 21 days, t₄ = 28 days. At t=0 days, six animals in each group received a thermal insult as a continuous 20 minute application of dry ice (CO₂ at -81⁰C) to the crowns of their upper right maxillary molar. The untreated left molars were used as controls. The remaining rat within each group did not receive the dry ice. All rats were given two sequential bone labels, calcein 5mg/kg and alizarin red 30mg/kg, administered intraperitoneally 8 days apart. The timing of the labels was such that all rats were euthanased 2 days after the last label. Following sacrifice, the maxillae were dissected out, fixed in ethanol and embedded in methylmethacrylate. Ten microns thick, undecalcified maxillary first molar coronal sections through the furcation were obtained. For every 3 out of 10 sections: the first was left unstained and undecalcified; the second stained with Von Kossa/haematoxylin & eosin; and the third decalcified and stained with haematoxylin & eosin. Unstained sections were viewed under fluorescence, while transmitted light microscopy was used for the other sections. Following initial analysis, the unstained, undecalcified sections were de-coverslipped and carbon coated. These sections were investigated with scanning electron microscopy and Energy Dispersive X-ray Spectrometry (EDS). Quantitative spot analysis and element mapping was performed on alveolar bone, ankylotic areas, cementum and dentine. A linear mixed effects model was employed to investigate any interaction between the four tissues of interest. A focal pattern of ankylosis was observed at days 14 and 21 in three rats. No ankylosis was observed in the control teeth. SEM revealed a focal type of ankylosis with central nodules of mineralized tissue forming within the PDL. Bridging between bone and dentine occurred with fine trabeculae which extended from the central mineralized nodule. Bridging was progressive and was more extensive at day 21 compared to day 14. At day 28, no ankylosis was observed. EDS analysis revealed that the ankylotic tissue was composed of major constituents Calcium and Phosphorous along with trace elements of Mg and Na. This was comparable to the surrounding alveolar bone, cementum and dentine. There was no statistically significant difference in the Ca/P ratios, Mg when ankylotic material was compared to bone. There was a trend towards elevated Na levels in ankylosis but this was not statistically significant relative to bone. Mg in dentine was lower than for all the other tissues and Na was higher in dentine when compared to bone and cementum. In the pulp, hypothermic injury demonstrated alteration of the odontoblast layer, reduction in cellularity, vascular alterations and tertiary dentin formation. At the 28 day observation period, the cellular and vascular changes had returned to levels comparable to the control teeth, indicating successful pulpal healing and regeneration. Marked tertiary dentine deposition was also observed at days 14, 21 and 28. Pulp chambers were visibly smaller due to tertiary dentine formation, however no pulp necrosis was observed. Thus the aseptic root resorption model, using a continuous 20 minute application of dry ice, suggested the occurrence of reversible pulpal tissue alterations compatible with an inflammatory repair process. The observation of ankylosis initiating as centralised nodules within the PDL suggest that the origins may be a consequence of osteogenic potential from PDL stem cells. The null hypothesis that a single, prolonged thermal insult on a rat molar does not have an effect on mineralized tissue formation and that ankylotic tissue is similar to bone was rejected. ABSTRACT There is a presumption that the ankylotic region formed after periodontal ligament (PDL) injury represents an unremarkable bony repair process. Essentially, the injury triggers an osteogenic repair response and the ankylotic tissue merely represents alveolar bone. There is uncertainty whether the oestogenic event is predominantly osteoblast driven, cementoblast directed, or a consequence of osteogenic potential from PDL stem cells. In this study, twenty-eight Sprague Dawley rats were divided into four groups of six animals, corresponding to one of four observation periods, and received a thermal insult as a continuous 20 minute application of dry ice to the crowns of their upper right maxillary molar. The appearance of ankylotic tissues was examined using backscattered electron images using a scanning electron microscope (SEM) equipped with an Energy Dispersive X-ray Analyser (EDS). The Ca, P, and trace elements contents were determined by EDS from four different hard tissue regions: ankylosis; bone; dentine and cementum, and the Ca/P ratios were calculated. Ankylosis was observed at days 14 and 21 in 3 rats and was not seen at day 28. No ankylosis was observed in the control teeth. BSE imaging revealed a focal type of ankylosis with central nodules of mineralized tissue forming within the PDL. The morphological features of ankylotic tissue differed to that of alveolar bone and dentine. Bridging between bone and dentine occurred with fine trabeculae which extended from the central mineralized nodule. EDS analysis showed that the ankylotic tissue was composed of major constituents Ca and P along with trace elements of Mg and Na. This was comparable to the surrounding alveolar bone, cementum and dentine. There was no statistically significant difference in the Ca/P ratios, Mg, and Na between ankylotic material and bone. Statistically significant differences was evident in Mg content between ankylotic material compared to dentine and cementum. Na content was higher in dentine than in ankylotic material. The results of this study indicate that, histochemically, ankylotic material is similar to bone. However, the appearance of ankylotic material as centralised foci with a morphology different from bone suggest that ankylosis may originate from an osteoblastic phenotype originating within PDL. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1522156 / Thesis (D.Clin.Dent.) -- University of Adelaide, School of Denstistry, 2010

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.