Objectives 1. To define the normative airway of Chinese population using three-dimensional imaging and computer analysis 2. To evaluate the upper airway differences in patients with normal facial profile and those with skeletal class III deformity 3. To evaluate the differences in upper airway models among patients with different dentofacial deformities and describe the role of computational fluid dynamics (CFD) in the human upper airway Materials and Methods Part I : Three-Dimensional Analysis of the Normative Upper Airway in Chinese This was a cross-sectional observational study. Cone beam computerized tomography (CBCT) scans of one hundred patients were analyzed. Computer analysis of the different upper airway parameters were studied including airway length and volume, as well as airway dimensions at the axial level of the soft palate, hard palate, base of tongue, and epiglottis. The most constricted airway location was identified and correlation analysis with variables of interest was done. Part II: A Cone Beam Computerized Tomography Study of Airway in Skeletal Class I and Class III Cone-beam computed tomography (CBCT) records of 200 patients were used to evaluate the upper airway dimensions. This sample consisted of patients with normal facial profile (Class I) and those demonstrating skeletal class III deformities. Computer analysis of the upper airway parameters such as airway length, airway volume, airway anterior-posterior and cross-sectional area dimensions at the hard palate, soft palate, base of tongue and epiglottis were performed. The most constricted airway sites were identified. Part III: Computational fluid dynamics study of upper airway in different dentofacial deformities Cone-beam computed tomography records of 12 patients were used to evaluate the upper airway. This sample consisted of facial skeletal Class I, II and III subjects. The upper airway models were constructed to allow CFD simulations in the airway from the epiglottis to the hard palate. Cross-sectional area, pressure, velocity and resistance were measured based on the reconstructed meshed models. Results Part I : Three-Dimensional Analysis of the Normative Upper Airway in Chinese In 100 subjects (40 males, 60 females) aged 16-40 years with normal facial profile, we found that the most constricted site occurs at the level of the soft palate. This surface area of this site was found to be linearly correlated to the airway volume, suggesting a significant relationship between the most constricted area and the total airway volume. Gender differences were found in airway length, volume, and in the dimensions at the base of tongue and epiglottis region. The mean airway length was 54.12 mm + 6.19 for males and 49.25 mm + 4.86 for females; airway volume of 15.09 cm3 + 4.92 for males and 13.12 cm3 + 4.72 for females. Part II: A Cone Beam Computerized Tomography Study of Airway in Skeletal Class I and Class III The sample consisted of 100 Class I (41 males, 59 females) with a mean age of 25.4 years and 100 Class III (38 males, 62 females) with a mean age of 23.5 years. Gender differences were noted in the airway length, airway volume and dimensions at the base of tongue and epiglottis for both groups. Males showed longer airway length, larger airway volume, larger airway dimensions at the base of tongue and epiglottis compared to females. Significant differences in all the airway parameters between the two groups were found except for airway length. The soft palate was found to be the most constricted airway site observed in the Class I subjects while Class III subjects showed restriction in both the soft palate and epiglottis region. Part III: Computational fluid dynamics study of upper airway in different dentofacial deformities The airflow was variable among airway in different skeletal deformities. The pressure changes along airway of Class II were the largest, followed by Class I. The pressure drop in the airway of Class III subjects were the smallest. The larger pressure differences would cause greater resistance in the airway. The highest resistance was observed in the airway of Class II subjects. Conclusion Part I : Three-Dimensional Analysis of the Normative Upper Airway in Chinese This airway data provide a normative reference that can be used in various dentofacial analysis as well as for diagnosis and treatment planning for related dentofacial deformities and in understanding the pathophysiology for sleep-related breathing disorders. Part II: A Cone Beam Computerized Tomography Study of Airway in Skeletal Class I and Class III The upper airway is larger in patients with Class III deformity than those with a normal facial profile. The site of restriction is commonly observed at the soft palate in the Class I group whereas patients with Class III deformity, the airway restriction sites are at both the soft palate and epiglottis. Understanding of the upper airway differences in between class I and class III facial deformities can have implications on treatment planning for orthognathic surgery. Part III: Computational fluid dynamics study of upper airway in different dentofacial deformities The results in this study suggest that skeletal pattern showed a significant correlation with pressure and resistance along the upper airway. / published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

published_or_final_version / abstract / toc / Dentistry / Master / Master of Philosophy

No description available.

The Mexican tetra, Astyanax mexicanus, exists as two morphs of a single species, a sighted surface morph and a blind cavefish. In addition to eye regression, cavefish have an increased number of taste buds, maxillary teeth and have an altered craniofacial skeleton. I investigated the effect the lens has on the development of the surrounding skull by ablating the lens over early ontogeny. This unique long-term study sheds light on how early embryonic manipulations on the eye can affect the shape of the adult skull. The effects of lens ablation were analyzed using landmark based morphometric analyzes. Morphometric analyzes indicate that there is a significant difference in the shape of the supraorbital bone and suborbital bones four through six. These bones expand into the eye orbit exhibiting variability in their shape. Interestingly, the number of caudal teeth on the lower jaw is also affected by lens ablation. I compared these findings between morphs and across two teleost species. I conducted lens removal in the surface fish to determine if it would produce a cavefish phenotype. Lens removal in the surface fish only partially results in a cavefish phenotype, indicating that lens loss is not solely responsible for the phenotypic differences between the two morphs. The effects of lens removal were then compared in the Mexican tetra and zebrafish. Surprisingly, the results indicate that the same bones are variable in shape in both species, indicating that the variability of these bones is conserved across species. Finally, I compared laser lens damage and full lens removal, to investigate the capacity for both lens regeneration and healing in the Mexican tetra. Together, the lens healing and regeneration studies indicate that lens absence in early development does not influence the shape of the skull. Lens absence during later development influences the mechanical forces in the skull resulting in the bones of the orbital region changing in size and shape. This study highlights the dynamic nature of the skull and sheds light on the influence the eyes (a soft tissue) have on the surrounding skull (a hard tissue) a topic which has been overlooked in the literature.

Abrasive wear occurs when a contact associated with stress between a metal surface and a herd particle (frequently of mineral origin) leads to friction between the two. In a very wide range of industrial applications, abrasive wear is the main reason for component and equipment repair or replacement. In most of these applications, especially those of earth moving, construction and mining equipment, digger teeth are used to improve equipment performance. Digger teeth can be produced in different shapes and sizes (mainly by casting) and a wide range of materials are used. This project is concerned with both a field trial of the wear of digger teeth fixed to the front of a bucket used in a gravel pit, and also a laboratory investigation of abrasive wear mechanisms. It was found that the wear of digger teeth increased with increasing working hours, but the wear rate eventually decreased. The dimensions and shape of the front of the tooth changed and gravel removal became more inefficient. Plastic deformation and phase transformation were observed in the worn surfaces of the teeth. In the laboratory study, many parameters were investigated utilising a pin-on disc technique. Wear rate increases linearly with load and decreases with sliding distance. The effect of attack angle on abrasive wear showed that wear volume increases with increasing attack angle up to a certain value (90°) and then decreases. Corrosion increases the initial wear rate, and the amount of material removed in the wet corrosive test was higher than the corresponding dry test. It was difficult to reproduce the same results from the field trial in the laboratory because of the difference in the conditions in the two cases. Optical and scanning electron microscopy were used to study the worn surfaces, abrasive papers and wear debris. Different abrasive wear mechanisms were observed throughout this investigation. A cutting mechanism associated with spiral debris was observed during short pin-on disc tests and with higher attack angles. A ploughing action associated with plate-like debris was observed during longer tests and at lower attack angles. Fragmentation was observed in brittle materials.

There is a general assumption that permanent teeth in children are emerging into the oral cavity earlier than the dates given in published scientific studies conducted many years ago. In the course of this research a rigorous experimental protocol was devised to provide reliable data collection and analysis methods and give contemporary emergence rate estimations with a strong scientific basis. In addition equations are presented to predict the chronological age of children using only the sex of the child and the number of permanent teeth present. Data was collected between April 1998 and July 2001 from 12,395 children between 4 and 15 years of age, in the Colchester area of the UK. The results show that the ages of emergence of the permanent teeth are later than previously assumed. This research also confirms previous research showing that girl's teeth emerge before boy's teeth, that there is no statistical difference in the age of emergence contra-lateral teeth in the same arch and that there is a statistical difference in the age of emergence of ipsi-lateral teeth in opposing arches.

Arklių dantų pakitimai gali būti siejami su daugeliu kitų ligų tokių kaip diegliai, išliesėjimas ir pašaro metimas iš burnos ir panašiai, todėl svarbu laiku aptikti dantų pakitimus ir juos gydyti. 2011 - 2013 metais LSMU veterinarijos akademijos stambių gyvulių klinikoje buvo gydyti 1010 arklių, iš jų 2011 metais buvo 10,57 proc. susijusių su dantų ligomis, 2012 metais - 15,97 proc., 2013 metais 15,95 proc. Dažniausi dantų pakitimai arkliams per 2011 - 2013 metus buvo aštrūs emalio kraštai. Arklio dantys dėvisi visą jo gyvenimą kramtant pašarą, o kasmet tai sudaro apie 2 - 3 mm. Dažniausiai atlikta dantų procedūra per 2011 - 2013 metus buvo dantų lyginimas. 2011 - 2013 metų statistika rodo, kad kasmet arklių su dantų problemomis atvedama daugiau, o tai rodo didesnį gyvūnų augintojų susidomėjimą savo augintiniais. / Clinical evaluation and treatment of equine dental abnormalities performed in Large animal clinic at the department of Non-communicable diseases LUHS Veterinary Academy in 2011 - 2013. In total there were registered 1010 horse patients during the 2011 – 2013 years, including 149 patients associated with dental abnormalities. Horses with dental problems were 10.57% in 2011, 15.97% in 2012, 15.95% in 2013 from all horse patient at LUHS Veterinary Academy Large animal clinic . The most common dental lesions in 2011 - 2013 were the sharp enamel edges. These patients were – 24 in 2011, 54 in 2012 and 71 in 2013 patients. According to the literature, the horse's teeth continue to grow throughout its life. The growing horse teeth worn during mastication process, which is about 2-3 mm annually. Another factor influencing the formation of sharp enamel edges - the specific structure of the head of a horse that is difference in the lower and upper jaw size. The upper jaw is wider than the lower, for that reason, the upper jaw teeth sharp enamel edges are formed from the side of the cheek, while mandibular teeth sharp enamel edges formed by the tongue side. Most common dental procedures performed in 2011 - 2013 has been a dental floating. This procedure is used in many dental abnormalities such as tooth overgrowth, sharp enamel edges resulting from, tooth hooks and so on. This procedure is also used as a prophylactic measure. ... [to full text]

The pressure-tension hypothesis is the governing dogma of orthodontic tooth movement. This theory proposes that the application of loads to the crown of a tooth during orthodontic mechano-therapy results in differential site-specific reactionary strains in the para-dental tissues. Briefly, following the application of orthodontic load the bone and periodontal ligament (PDL) on one side of the tooth is placed in compression favoring bone resorption, while on the other side of the tooth they are placed in tension favoring osteogenesis The present in vitro model provides a surrogate for the PDL on the tension side of the tooth during orthodontic tooth movement and aims to identify mechanically induced changes in the expression of osteo-regulatory cytokines in human PDL cell cultures in response to tensile mechanical strain. Materials and Methods: PDL explants were obtained from pathology free bicuspids of two human subjects following extraction of the teeth for orthodontic purposes. Following serial passage, cells were plated on Uniflex� plates and consigned to either the experimental or control groups. Experimental cells were exposed to a cyclic uniaxial tensile mechanical strain for 6,12 or 24 hours using the Flexercell FX 4000 strain unit. Total RNA was extracted using a two-step procedure and samples were analysed using real-time RT-PCR assays for a range of osteo-regulatory cytokines. Results: Human PDL cells expressed mRNA for a range of cytokines of known significance to osteogenesis and osteoclastogenesis in response to mechanical stimulation. Conclusions: The production of osteo-regulatory cytokines by PDL cells in response to mechanical strain suggests that these cells have the potential to contribute to the osseous modeling of orthodontic tooth movement. The presence of osteogenic signalling drive in response to tensile strain tends to support the basic assertions of the pressure-tension hypothesis.

Copies of author's previously published articles inserted. / Bibliography: leaves 136-155. / xxi, 180 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines tooth-to-tooth contact under controlled experimental conditions that simulate bruxism. Focuses on the wear characteristics of enamel and factors influencing the nature and extent of human enamel wear. / Kaidonis, John Aristidis / Thesis (Ph.D.)--University of Adelaide, Dept. of Dentistry, 1995?

Includes bibliographical references (leaves [1-20]). / xxi, 168, [20] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A systematic analysis of wear involving the in vitro analysis of the wear of standard composite resin and glass ionomer cements restorations under controlled conditions; and, the qualitative and quantitative investigation of wear over a range of pH's and loads which might be encountered clinically in order to develop a "wear map" of the micromorphology of wearing teeth and restorations and a systematic modeling of wear rates. / Thesis (Ph.D.)--University of Adelaide, Dept. of Dentistry, 2001