Tesi sul tema "Enamel"
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1
Fletcher, Jane. "Regenerative Dental Enamel". Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525455.
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2
Fong, Hanson Kwok. "Towards enamel biomimetics : structure, mechanical properties & biomineralization of dental enamel /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10606.
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3
Wong, Hai Ming. "Developmental defects of enamel". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36269815.
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4
Wong, Hai Ming, e 王海明. "Developmental defects of enamel". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36269815.
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5
Benson, Philip Edward. "Measurement of enamel demineralisation". Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368002.
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6
Kirkham, J. "The mineralisation of dental enamel : An investigation into the role of developing enamel proteins". Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354310.
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7
Lihong, He. "Mechanical behaviour of human enamel and the relationship to its structural and compositional characteristics". Connect to full text, 2008. http://hdl.handle.net/2123/3536.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Sydney, 2008.Title from title screen (viewed 9 October 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Biomaterials Science Research Unit, Faculty of Dentistry. Includes bibliographical references. Also available in print form.
8
McKee, Marc Douglas. "A morphological and functional investigation of the enamel organ and enamel in the rat incisor /". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75424.
Testo completoAbstract (sommario):
A morphological and functional investigation of the enamel organ and enamel was carried out on the incisor of the rat. Using transmission electron microscopy and other electron optical techniques, the ultrastructure of enamel hydroxyapatite crystallites and the morphology of the cells of the enamel organ related to these crystallites were examined. In the enamel secretion zone, putative cell communication via matched approaches of rough endoplasmic reticulum to the ameloblast cell membrane was not confirmed. Throughout the enamel organ, extracellular permeability was assessed using radiolabeled proteins as tracers. Regional differences were found, especially related to the two types of maturation ameloblasts. Several modified histochemical techniques were successfully applied to the enamel such that the functional contribution of each type of ameloblast was ascertained. In this way it was demonstrated that several functional cell subpopulations exist and that they can be correlated with different calcium and protein distributions within the enamel. In vivo injection of vinblastine, and in vitro treatments with other drugs, all severely modified the enamel maturation staining pattern and $ sp{45}$Ca uptake. In addition, it was found that ruffle-ended maturation zone ameloblasts possess higher levels of specific transferrin receptor sites relative to smooth-ended ameloblasts, a finding that may be directly related to the deposition of iron within the enamel.
9
湯翠明 e Sui-ming Lily Tong. "The clinical and microscopic effects of vital bleaching and enamel micro-abrasion on surface enamel". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B30433204.
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10
Tong, Sui-ming Lily. "The clinical and microscopic effects of vital bleaching and enamel micro-abrasion on surface enamel /". Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21129678.
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11
King, Nigel Martyn. "Prevalence and characteristics of developmental defects of dental enamel in Hong Kong". Thesis, Hong Kong : Dept. of Children's Dentistry & Orthodontics, University of Hong Kong, 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12838007.
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12
Hung, Cheung-sing Tony. "Bonding of dental alloys to enamel". Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/HKUTO/record/B39558150.
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13
孔祥陞 e Cheung-sing Tony Hung. "Bonding of dental alloys to enamel". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39558150.
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14
Creanor, Stephen Leonard. "Remineralisation of the incipient enamel lesion". Thesis, University of Glasgow, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305637.
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15
Birch, W. J. "Incremental growth of deciduous tooth enamel". Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1348309/.
Testo completoAbstract (sommario):
Deciduous tooth formation begins before birth and ends after birth. This makes it more difficult to construct a continuous developmental chronology for deciduous teeth than for permanent teeth. The discovery of the neonatal line in enamel and confirmation that it marks birth, allowed the expansion of deciduous dental chronologies, which until this time had been largely based on qualitative descriptions. The aim of this study was to use the daily incremental record in deciduous enamel to document rates of enamel formation and to use these data to produce regression equations that describe the average rates of deciduous enamel formation for each tooth type. These formulae can then be applied to all deciduous teeth even when daily increments are not visible, in order to estimate crown formation times and other events during crown development, as well as to determine the age at death where enamel formation has ceased prior to completion. In permanent teeth, rates of enamel formation vary between 2.5μm per day at the EDJ to 6.5μm per day at the enamel surface. Seventy deciduous ground sections were examined and it was established that the daily rates in deciduous enamel varied less, with regional weighted means for all tooth types ranging from 2.85μm per day at the EDJ to 3.40μm per day at the enamel surface with extreme outliers of 2.07 to 4.97μm per day. The average daily incremental growth rate of enamel in deciduous teeth was calculated for each tooth type, the weighted mean of the apposition rate over both aspects (labial/buccal and lingual) and over all three regions (cervical, lateral and occlusal) for all tooth types was 3.23μm per day. A key finding of this study was that there is a marked reduction in the enamel formation rate in the zone immediately following the neonatal line or following other accentuated striae assumed to be associated with stressful events. A catch-up phase usually followed these events, during which the previous rates recovered. These data provide clear evidence of enamel hypoplasia associated with both the birth process and other events that cause stress in perinatal life.
16
Williams, David Michael. "Psychological impact of dental enamel opacities". Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/55569/.
Testo completoAbstract (sommario):
Conclusion: Implicit measures of attitude can be used to identify variation in the strength of attributions made about different dental conditions. Explicit measures may measure the valence of attitudes. This study suggests that mild fluorosis may be perceived more favourably than untreated dental caries. It has also shown that traditional approaches to assessing the perception of fluorosis may have exaggerated its impact.
17
Chew, Hooi Pin. "Novel assessments of early enamel erosion". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/novel-assessments-of-early-enamel-erosion(3d27373c-adf3-4254-9789-66b587b22d92).html.
Testo completoAbstract (sommario):
Dental erosion has been defined as a chemical process that involves the dissolution of enamel and dentine by acid(s) not derived from bacteria when the surrounding aqueous phase is under-saturated with tooth mineral. Clinically however, dental erosion hardly ever occurs exclusively from the other modes of tooth wear such as abrasion and attrition. Hence the term erosive wear has been proposed and used to describe erosion-facilitated wear.With the prevalence of erosive wear being reported to be on the rise among children and adolescents in many countries, a plethora of oral health products such as dentifrices and mouth rinses had been put forward with claims of increasing the resistance of the enamel and / or dentine from being demineralised. However, the efficacy of these oral health products is still widely questionable as the studies carried out were mainly in vitro and / or in situ studies and the contradictory results were reported by different groups of researchers.The above mentioned discrepancies are often due to non-standardised in vitro and in situ study designs of erosion studies. Parameters such as type of acid used, concentration of acid used, duration of acid exposure, inclusion or exclusion of abrasion in the study model, ex vivo or in vivo acid challenge, ex vivo or in vivo treatment with oral health product and the nature of pellicle on the specimen are often varied.The availability of an detection tool which could be used to measure demineralisation on natural tooth surface in vivo would exclude many of the inevitable variability in in situ and in vitro study design, such as the simulation of the intra oral conditions in which the erosion challenge and intervention take place and the nature of the pellicle formed on the specimens. Hence with an in vivo detection tool, it is hopeful that the efficacy of any interventions would be evaluated more accurately and its results expounded to a wider context. It would be useful if the tool was sensitive to the very early stages of the erosion process as this would entail shorter and more economical study designs. Arising from the problems discussed above, potential non-invasive assessment methods that could be used clinically to measure demineralisation were explored and it was found that two optical methods, Optical Coherence Tomography (OCT) and Quantitative Light-induced Fluorescence (QLF) were potential methods for the tasks.The studies described in this thesis were divided into three main big sections; the first being the in vitro validation work of the two optical methods (Chapter 5 and 6), the second, validation of these methods in situ (Chapter 7) and finally the assessment of the efficacy of a high fluoride dentifrice on early enamel erosion using these two methods (Chapter 8).In the in vitro validation (Chapter 5), it was demonstrated that both QLF and OCT were able to detect erosion-interval related changes in natural surface samples eroded with orange juice for 60 minutes. However, results of Multiple Linear Regression and Paired t test suggest that QLF was more sensitive than OCT in the detection of demineralisation changes in this particular experimental setting. QLF demonstrated a R2 value of 0.590 while the best of the OCT outcome measure demonstrated a R2 value of 0.319.Further in vitro study (Chapter 6) was performed to explore the use of a moistened-exposed surface as a reference method for both OCT and QLF as it was felt that it would be beneficial if a coated reference area which posts as an additional step for error could be done away with. Results of this study showed that the moistened-exposed surface could be used a reference method for QLF only but not for OCT. Furnished with the findings of the above mentioned in vitro validation studies, an in situ validation of both the optical methods was performed (Chapter 7). It was found that OCT and QLF were able to longitudinally measure in situ demineralisation on polished and natural surfaced enamel which were subjected to 150 minutes of in vivo exposure to orange juice. Similar to the results of the in vitro study, QLF was found to be more sensitive than OCT in the detection of demineralisation changes on natural surfaced enamel. The last in situ study (Chapter 8) was to evaluate whether there was a protective effect of treating human enamel with a high-concentrated fluoride dentifrice during an active erosion phase and whether OCT and QLF were able to detect the protective effect. It was found that treating natural surface enamel with a 5000ppm NaF dentifrice increased its resistance against concurrent in vivo erosive challenge with an orange juice challenge. QLF was able to detect the protective effect of the 5000ppm NaF dentifrice on natural surface enamel against early in vivo erosion with an orange juice challenge regime while OCT did not.
18
Choi, Yuen-ling Ruth. "The prevalence of enamel defects in Hong Kong Children in 1983 and 1991 a thesis submitted to the University of Hong Kong in partial fulfilment of the requirements for the degree of Master of Dental Surgery /". Click to view the E-thesis via HKUTO, 1993. http://sunzi.lib.hku.hk/HKUTO/record/B38628508.
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19
Itthagarun, Anut. "Effect of dentifrices on the fluoride uptake, de/ remineralization andmorphology of sound enamel and initial enamel lesions". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31238622.
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20
蔡苑玲 e Yuen-ling Ruth Choi. "The prevalence of enamel defects in Hong Kong Children in 1983 and 1991: a thesis submitted to the University ofHong Kong in partial fulfilment of the requirements for the degree ofMaster of Dental Surgery". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B38628508.
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21
Itthagarun, Anut. "Effect of dentifrices on the fluoride uptake, de/ remineralization and morphology of sound enamel and initial enamel lesions /". Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B2112971X.
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22
Nkosi, P. M. "Efficacy of enamel sealants in preventing demineralisation". Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5068_1263936707.
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23
Walsh, Paula. "Acid permeation into dental enamel and hyroxyapatite". Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317283.
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24
Dansie, Brian L. "Micronutrition and Enamel Disturbances in Bronchopulmonary Dysplasia". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372026150.
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25
Pellillo, Sonni. "Effects of sodium hypochlorite on enamel composition". Thesis, NSUWorks, 2015. https://nsuworks.nova.edu/hpd_cdm_stuetd/66.
Testo completoAbstract (sommario):
The purpose of this study was to evaluate the effects of sodium hypochlorite on the organic and inorganic composition of enamel. Background: With the advent of enamel bonding for orthodontic appliances in the late 1970s, it has been shown that traditional phosphoric acid etching affects the inorganic portion of the enamel.1, 2 In an attempt to enhance the acid etching pattern and, furthermore, the bond strength, additional pretreatment techniques that target the organic components of the enamel biofilm have been proposed. One such method is the non-invasive enamel pretreatment with 5.25% sodium hypochlorite (NaOCl) prior to phosphoric acid etching.3, 4 It has been suggested that the mechanism by which sodium hypochlorite enhances the etching pattern is enamel deproteinization, in which organic elements, including the acquired film, are removed from the enamel surface.3, 5 This presumption is based on the multitude of endodontic literature supporting the use of NaOCl as an effective irrigant in root canal therapy6-13. In contrast to dentin and pulpal tissue, enamel is comprised of minimal organic matter.14, 15 As a result of this fact and the limited amount of experimentation of the effect of NaOCl on the enamel surface, the true mechanism by which sodium hypochlorite enhances the etching pattern of enamel is questionable.5, 16 The objective of this study was to determine the compositional effects of sodium hypochlorite on human enamel. Methods: Following IRB approval, 120 enamel sections from 22 extracted human premolar teeth were randomly divided into three experimental groups and one control group.17 The control group (E = enamel) received no treatment. The first experimental group (A = phosphoric acid) received a 15-second treatment with 37% phosphoric acid, rinsed with distilled water and air sprayed for 20 seconds, then dried with oil free compressed air. The second experimental group (H = sodium hypochlorite) received a treatment of 5.25% sodium hypochlorite for 60 seconds, washed with distilled water for 10 seconds, and dried. The third experimental group (HA = sodium hypochlorite + phosphoric acid) received a treatment of 5.25% sodium hypochlorite for 60 seconds, washed with distilled water for 10 seconds, dried, then receive the 15-second treatment with 37% phosphoric acid as in Group A.3 Following treatment preparations of the four groups, scanning electron microscopy (SEM)/energy-dispersive X-ray spectrometer (EDX) analysis was performed for all groups.18 For elemental concentration, a one-way ANOVA and Tukey’s post hoc statistical tests were applied.17, 19, 20 ANOVA and Tukey tests were performed at a significance level of p ≤ 0.05. Results: There were no significant effects of treatment on the enamel elements carbon (C), calcium (Ca) sodium (Na), oxygen (O), and phosphorous (P). There was a significant effect of treatment on the amount of chlorine (Cl) in enamel between groups acid (A) and hypochlorite + acid (HA) as well as between groups hypochlorite (H) and hypochlorite + acid (HA) (p = 0.004). The amount of variation of iodine (I) in the enamel composition between untreated enamel (E) and enamel treated with sodium hypochlorite + phosphoric acid (HA) was significant (p = 0.004). Additionally, there was a significant decrease in the quantity of antimony (Sb) found in the control group (E) versus the hypochlorite + acid (HA) experimental group (p = 0.002). Lastly, tin (Sn) was significantly reduced from the enamel surface (E) when treated with hypochlorite + acid (HA) (p = 0.008). Conclusions: The various treatments minimally affected the elemental concentrations of C, Ca, Na, O, and P. The amount of chlorine present in enamel significantly increased following treatment with sodium hypochlorite (H) alone and even more so following treatment with phosphoric acid and sodium hypochlorite (AH). In contrast, elements I, Sb, and Sn demonstrated a congruent reduction in concentration after treatment with hypochlorite and acid (HA). Although it has been hypothesized that sodium hypochlorite targets the organic pellicle present on the surface of enamel via a process known as deproteinization, the findings presented here suggest that pre-treatment with NaOCl impacts the inorganic components of enamel more so than the organic constituents. These quantitative findings corroborate the enhanced etching pattern that can be visualized under scanning electron microscopy in this as well as previous studies.
26
Al-Azzawi, Samaa. "Variations of the elastic modulus of human enamel :". Thesis, Queen Mary, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404377.
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27
Peck, S. "Acoustic microscopy of caries in human dental enamel". Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375312.
Testo completo
28
Zhu, Jiajun, e 朱嘉珺. "Ultra-structural aspects of human enamel surface pretreatments". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208558.
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29
Tetlow, Andrew Peter. "Linear enamel hypoplasia at Santa Rita Corozal, Belize". Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4608.
Testo completoAbstract (sommario):
The focus of this thesis is an analysis of a sample of dentition collected from the Postclassic Maya site of Santa Rita Corozal in Northern Belize. The goal of this study is to determine what the presence (or absence) of Linear Enamel Hypoplasia (LEH) can demonstrate about the general health (i.e. stress, disease, nutrition, and weaning age) and social status of a single subset of the Late Postclassic (900-1500 CE) Maya living at Santa Rita Corozal. Specifically, this thesis focuses on dentition of thirteen individuals from a large Postclassic platform group. The sample consists of sub-adult and adult female dentition from individuals that are associated with the same relative time period (Late Postclassic). The question being addressed in this thesis is: why has LEH presented in these individuals? These samples will also be compared to other studies involving LEH throughout the Maya area, in both similar and dissimilar environments. The preponderance of female and sub-adult remains also makes this platform group a very interesting topic of study for LEH in the Maya area, as it is unusual to find a concentrated area of individuals such as these. Importantly, the results of this study show that there is no significant relationship between general levels of stress and the overall status of an individual. Measurements collected from the LEH affected teeth demonstrate that all of the LEH episodes occurred before the age of 6. The mean age for the teeth sampled that show signs of LEH is 3.5 years, which is consistent with theories pertaining to the weaning age of the Maya during concomitant time periods. However, the size of this sample precludes any concrete conclusions about weaning ages and stress in general among the Maya at Santa Rita Corozal. It is also possible that these events are related to larger issues such as regional droughts or water-born disease.ID: 029050230; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.A.)--University of Central Florida, 2010.; Includes bibliographical references (p. 102-109).
M.A.
Masters
Department of Anthropology
Sciences
30
Boyle, Edward Liam. "Factors affecting demineralisation and remineralisation of human enamel". Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367095.
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31
Kosztolowicz, Tadeusz, e Katarzyna D. Lewandowska. "Subdiffusive reaction front in the enamel caries process". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196978.
Testo completoAbstract (sommario):
Starting with the equation describing subdiffusion associated with chemical reactions for one-static reactant, we show that the reaction front X f evolves in time as x f ~ t α/2 with α < 1. The equation is applied to the carious lesion which is caused by the chemical reactions of diffusing acid molecules or pure hydrogen ions with static hydroxyapatite in the tooth enamel. Comparing our theoretical results with the already published experimental ones, we conclude that in some cases the transport process of the acids in the tooth enamel appears to be subdiffusive and should be described by the subdiffusion-reaction equation with the fractional time derivative.
32
Kosztolowicz, Tadeusz, e Katarzyna D. Lewandowska. "Subdiffusive reaction front in the enamel caries process". Diffusion fundamentals 2 (2005) 124, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14466.
Testo completoAbstract (sommario):
Starting with the equation describing subdiffusion associated with chemical reactions for one-static reactant, we show that the reaction front X f evolves in time as x f ~ t α/2 with α < 1. The equation is applied to the carious lesion which is caused by the chemical reactions of diffusing acid molecules or pure hydrogen ions with static hydroxyapatite in the tooth enamel. Comparing our theoretical results with the already published experimental ones, we conclude that in some cases the transport process of the acids in the tooth enamel appears to be subdiffusive and should be described by the subdiffusion-reaction equation with the fractional time derivative.
33
Wang, Hsiao-Chuan David. "Laser ultrasonic technique for evaluating human dental enamel". Thesis, The University of Sydney, 2009. https://hdl.handle.net/2123/29230.
Testo completoAbstract (sommario):
An optical, non—contact, non—destructive ultrasonic technique utilising laser generated
and detected surface acoustic waves is proposed to replace, or complement,
conventional diagnostic methods for quantitative evaluation of the elastic modulus,
and hence the mineralisation and strength, of human dental enamel. This technique
has the ability to provide repetitive measurements for determining the location and the
severity of the decaying dental hard tissue as well as assessing the efficacy of
reparative treatments.
In this thesis a laser ultrasonic technique that can perform remote elasticity evaluation
for surface material of small dimension samples is presented. The generation of
surface acoustic waves is achieved by short focused laser pulses with optical energy
below the damage threshold. The detection mechanism is an interferometer with a
manoeuvrable and extremely compact sensor head using optical fibre. The measured
surface wave propagation velocity, and especially its dispersion, is then used to
determine the state of elasticity, as a function of depth, of the surface material of the
specimen.
This evaluation technique was validated by measuring well characterised metal
structures before applying to evaluate human dental enamel. Tooth samples with
artificial lesions were prepared. Sound enamel and lesioned regions, as well as lesions
of different severities, were measured and the results are clearly distinguishable from
each other and fit well with physical expectations and theoretical values. In addition,
results from progressive monitoring of the change in enamel elasticity during a two
week remineralisation process match with the actual physical changes and hence
confirm the efficacy of the treatment and the ability of this system to evaluate
faithfully the physical changes that have occurred.
This is the first time, to the best of our knowledge, that a laser based surface wave
velocity dispersion technique has been successfully applied to human dental enamel.
34
Al-Obaidi, Rand. "In vitro enamel subsurface lesions : characterization and treatment". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTT017/document.
Testo completoAbstract (sommario):
Les taches blanches sont liées à l'hypominéralisation sous la surface de l'émail et sont la 1ère étape du développement de la carie dentaire. La détection précoce des caries dentaires naissantes avant qu'elles n'atteignent le stade de la cavitation offre une opportunité pour des soins dentaires efficaces. Pour réaliser les objectifs de cette étude qui sont de renforcer l'idiome des soins minimalement invasifs, nous avons identifié un modèle de cycle de pH modifié qui permet d’imiter les conditions intra-buccales qui conduisent à la formation de lésions de type tache blanche, dans un court laps de temps. Des techniques optiques non invasives, comme la microscopie Raman confocale et la microscopie multiphotonique, ont été utilisées dans cette étude pour détecter de petits changements dans la composition chimique de l'émail in vitro.De plus, la technique de nano-indentation a été appliquée pour étudier les changements dans les propriétés mécaniques de l'émail et les relier à ceux affectant sa composition chimique après l'induction des caries, afin d‘ajouter de la spécificité chimique-mécanique aux informations sur les lésions sous-surface de l'émail. Les résultats obtenus démontrent un grand potentiel pour les techniques examinées, fournissant une base pour des applications intéressantes dans le diagnostic clinique de différentes pathologies dentaires. Pour résoudre le problème du traitement des lésions primitives sans intervention chirurgicale, l'efficacité de la crème GC Tooth Mousse et du dentifrice contenant de la nano-hydroxyapatite «KAREX» dans l'amélioration de la reminéralisation de l'émail déminéralisé par la localisation du phosphate de calcium amorphe à la surface de la dent a été inspectée. L'étude a indiqué le manque de preuves fiables soutenant l'efficacité des agents reminéralisants dans le traitement des taches blanches. Ce travail doit être poursuivi par d'autres études in-vitro et par des études cliniquesWhite spot lesion is the subsurface hypomineralization of enamel indicating the 1st stage of dental caries development. Early detection of incipient dental caries before it reaches the stage of cavitation offers an opportunity for effective dental care. The objectives of this study were to strengthen the idiom of minimally invasive treatment. In order to achieve the specified goals; we have identified a modified pH cycling model that can mimic the intraoral conditions leading to white spot lesions formation in a short time. In addition, non-invasive optical techniques, such as confocal Raman microscopy and multiphoton microscopy were used in this study to detect small changes in the enamel chemical composition in vitro.Furthermore, nano-indentation technique was used to detect the changes in the mechanical properties of enamel and relate them to those affecting its chemical composition after caries induction in order to add chemico-mechanical specificity in providing important information about subsurface lesions in enamel. The obtained results demonstrate a great potential for the examined techniques, providing a basis for interesting applications in the clinical diagnosis of various pathological conditions in dentistry. To treatment the incipient carious lesions non-invasively, the effectiveness of GC Tooth Mousse cream and nHA containing-dentifrice "KAREX" in the remineralization of demineralized enamel through localizing amorphous calcium phosphate at tooth surface has been inspected. The study indicated a lack of reliable evidence supporting the efficacy of remineralizing agents in the treatment of white spot lesions. Within the limitations of this study, further laboratory studies together with clinical research are therefore required to increase the available knowledge on this prevalent subject
35
Shabanian-Borojeni, Mitra. "Wear studies of enamel and some restorative materials". Title page, contents and summary only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phs5241.pdf.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves [1-20]). 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.
36
He, Lihong. "Mechanical Behaviour Of Human Enamel And The Relationship To Its Structural And Compositional Characteristics". Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/5106.
Testo completoAbstract (sommario):
Doctor of Philosophy(PhD)Objectives As the outer cover of teeth structure, enamel is the hardest, stiffest and one of the most durable load-bearing tissues of the human body. Also, enamel is an elegantly designed natural biocomposite. From a material science point of view, scientists are interested in the structure and function of the nature material. How does nature design the material to meet its functional needs? From a dental clinic point of view, dental practitioners are keen to know the properties of enamel and compare it with different dental materials. What kind of dental materials can best simulate enamel as a restoration in the oral cavity? The research presented in this thesis on the mechanical behaviour of enamel in respect of its structural and compositional characteristics will attempt to provide answers or indications to the above questions. Theoretical analysis, as well as experimental investigations of both man-made and natural composites materials, has shown that hierarchical microstructure and organic matrix glues the inorganic particles together and plays an important role in regulating the mechanical properties of the composite. Bearing this finding in mind, in the current investigations, we assume the hierarchical microstructure and trace protein remnants in enamel regulate the mechanical behaviour of the natural biocomposite to meet its functional needs as a load bearing tissue with superb anti-fatigue and wear resistant properties. One of the important reasons that dental hard tissues haven’t been thoroughly investigated is due to the limited sample volume. Fortunately, with the development of nanoindentation technique and equipment, it is now possible to explore the mechanical properties of small volume samples. The application of nanoindentation on dental hard tissues has been documented. However, most investigations have concentrated on only reporting the basic mechanical properties such as elastic modulus and hardness. Very few of them have taken the role of microstructure and composition of these natural biocomposites into their considerations. The main aim of this investigation is to interpret how microstructural and compositional features of enamel regulate its mechanical behaviour. To achieve this goal, the analytical methods considering nanoindentation data need to be expanded so that more information not only elastic modulus and hardness but also stress-strain relationship, energy absorption ability, and creep behaviour may be evaluated with this technique. These new methods will also be of benefit to dental material evaluation and selection. Materials and methods Based on the Oliver-Pharr method1 for the analysis of nanoindentation data, Hertzian contact theory2 and Tabor’s theory3, a spherical nanoindentation method for measuring the stress-strain relationship was developed. Furthermore, nanoindentation energy absorption analysis method and nanoindentation creep test were developed to measure the inelastic property of enamel. With the above methods, sound enamel samples were investigated and compared with various dental materials, including dental ceramics and dental alloys. • Firstly, using a Berkovich indenter and three spherical indenters with 5, 10 and 20 µm nominal radius, the elastic modulus, hardness and stress-strain relationship of different samples were investigated and compared. • Secondly, mechanical properties of enamel in respect to its microstructure were investigated intensively using different indenters by sectioning teeth at different angles. • Thirdly, inelastic behaviour of enamel such as energy absorption and creep deformation were observed and compared with a fully sintered dense hydroxyapatite (HAP) disk to illustrate the roles of protein remnants in regulating the mechanical behaviour of enamel. • Fourthly, to confirm the functions of protein remnants in controlling mechanical behaviour of enamel, enamel samples were treated under different environments such as burning (300°C exposure for 5 min), alcohol dehydration and rehydration to change the properties of proteins before the nanoindentation tests. • Lastly, micro-Raman spectroscopy was employed to measure and compare the indentation residual stresses in enamel and HAP disk to evaluate the role of both hierarchical microstructure and protein remnants in redistributing the stresses and reinforcing the mechanical response of enamel to deformation. Results and significance Nanoindentation is an attractive method for measuring the mechanical behaviour of small specimen volumes. Using this technique, the mechanical properties of enamel were investigated at different orientations and compared with dental restorative materials. From the present study, the following results were found and conclusions were drawn. Although some newly developed dental ceramics have similar elastic modulus to enamel, the hardness of these ceramic products is still much higher than enamel; in contrast, despite the higher elastic modulus, dental metallic alloys have very similar hardness as enamel. Furthermore, enamel has similar stress-strain relationships and creep behaviour to that of dental metallic alloys. SEM also showed enamel has an inelastic deformation pattern around indentation impressions. All of these responses indicated that enamel behaves more like a metallic material rather than a ceramic. Elastic modulus of enamel is influenced by highly oriented rod units and HAP crystallites. As a result, it was found to be a function of contact area. This provides a basis to understand the different results reported in the literature from macro-scale and micro-scale tests. Anisotropic properties of enamel, which arise from the rod units, are well reflected in the stress-strain curves. The top surface (perpendicular to the rod axis) is stiffer and has higher stress-strain response than an adjacent cross section surface because of the greater influence of the prism sheaths in the latter behaviour. Enamel showed much higher energy absorption capacity and considerably more creep deformation behaviour than HAP, a ceramic material with similar mineral composition. This is argued to be due to the existence of minor protein remnants in enamel. Possible mechanisms include fluid flow within the sheath structure, protein “sacrificial bond” theory, and nano-scale friction within sheaths associated with the degustation of enamel rods. A simple model with respect of hierarchical microstructure of enamel was developed to illustrate the structural related contact deformation mechanisms of human enamel. Within the contact indentation area, thin protein layers between HAP crystallites bear most of the deformation in the form of shear strain, which is approximately 16 times bigger than contact strain in the case of a Vickers indenter. By replotting energy absorption against mean strain value of a protein layer, data from different indenters on enamel superimposed, validating the model. This model partially explained the non-linear indentation stress-strain relationship, inelastic contact response and large energy absorption ability of enamel and indicated the inelastic characteristics of enamel were related to the thin protein layers between crystallites. Following different treatments, mechanical properties of enamel changed significantly. By denaturing or destroying the protein remnants, mechanical behaviour, especially inelastic abilities of enamel decreased dramatically, which indicates matrix proteins endow enamel better performance as a load bearing calcified tissue. Comparison of Raman derived residual maps about indentations in enamel and a sintered homogeneous HAP showed the hierarchical structure influenced the residual stress distribution within enamel. Moreover, less residual stresses were found in enamel and were a consequence of the protein remnants. These are evidence as to how the microstructure meets the functional needs of the enamel tissue. In general, evidence from different approaches indicated that the hierarchical microstructure and small protein remnants regulated the mechanical behaviour of enamel significantly at various hierarchical levels utilising different mechanisms. This investigation has provided some basis for understanding natural biocomposites and assisting with dental clinic materials selection and treatment evaluation procedures. References 1. Oliver WC, Pharr GM. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J Mater Res. 1992;7(6):1564-83. 2. Hertz H. Miscellaneous Papers. London: Jones and Schott, Macmillan; 1863. 3. Tabor D. Hardness of Metals. Oxford: Clarendon Press; 1951.
37
Robinson, Bruce William. "A morphological study of the formation of the dentino-enamel junction in the rat molar : the role of dentin in enamel formation". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27630.
Testo completoAbstract (sommario):
This thesis is a morphological study detailing the initial formation of the dentino-enamel junction (DEJ) in the rat molar. It was undertaken to determine how enamel apatite crystals are initiated during tooth development. The DEJ was investigated along its developmental gradient so that both the spatial and temporal sequences of dentin and enamel mineralization could be observed. For this investigation both conventional and selected-area dark-field electron microscopy were applied. The results of this study indicate that enamel crystals arise by epitaxial growth from preformed dentin crystals. This is supported by the temporal relationship beween dentin and enamel where dentin mineralization preceeds enamel mineralization and the intimate spatial relationship between the apatite crystals of dentin and enamel at both the newly formed and the more mature dentino-enamel junction. These results also suggest that the terminal portions of collagen fibrils in the pre-dentin matrix undergo some alteration prior to mineralization which may be related to their function in presenting dentin apatite to the enamel matrix. The interrelatonship between both the inorganic and organic matrices of dentin and enamel are presented in a working model and discussed in light of the mechanisms by which mineralized dentin may promote the formation of enamel crystals.Medicine, Faculty of
Graduate
38
Bertacci, Angelica <1977>. "Evaluation of fluid transport processes in dental enamel. Methods to assess the relevance of enamel permeability in caries prevention and etching treatments". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1561/1/bertacci_angelica_tesi.pdf.
Testo completoAbstract (sommario):
This thesis evaluated in vivo and in vitro enamel permeability in different physiological and clinical conditions by means of SEM inspection of replicas of enamel surface obtained from polyvinyl siloxane impressions subsequently later cast in polyether impression ma-terial. This technique, not invasive and risk-free, allows the evaluation of fluid outflow from enamel surface and is able to detect the presence of small quantities of fluid, visu-alized as droplets. Fluid outflow on enamel surface represents enamel permeability. This property has a paramount importance in enamel physiolgy and pathology although its ef-fective role in adhesion, caries pathogenesis and prevention today is still not fully under-stood.
The aim of the studies proposed was to evaluate enamel permeability changes in differ-ent conditions and to correlate the findings with the actual knowledge about enamel physiology, caries pathogenesis, fluoride and etchinhg treatments. To obtain confirmed data the replica technique has been supported by others specific techniques such as Ra-man and IR spectroscopy and EDX analysis.
The first study carried out visualized fluid movement through dental enamel in vivo con-firmed that enamel is a permeable substrate and demonstrated that age and enamel per-meability are closely related. Examined samples from subjects of different ages showed a decreasing number and size of droplets with increasing age: freshly erupted permanent teeth showed many droplets covering the entire enamel surface. Droplets in permanent teeth were prominent along enamel perikymata.
These results obtained through SEM inspection of replicas allowed innovative remarks in enamel physiology. An analogous testing has been developed for evaluation of enamel permeability in primary enamel. The results of this second study showed that primary enamel revealed a substantive permeability with droplets covering the entire enamel sur-face without any specific localization accordingly with histological features, without changes during aging signs of post-eruptive maturation. These results confirmed clinical data that showed a higher caries susceptibility for primary enamel and suggested a strong relationship between this one and enamel permeability.
Topical fluoride application represents the gold standard for caries prevention although the mechanism of cariostatic effect of fluoride still needs to be clarified. The effects of topical fluoride application on enamel permeability were evaluated. Particularly two dif-ferent treatments (NaF and APF), with different pH, were examined. The major product of topical fluoride application was the deposition of CaF2-like globules. Replicas inspec-tion before and after both treatments at different times intervals and after specific addi-tional clinical interventions showed that such globule formed in vivo could be removed by professional toothbrushing, sonically and chemically by KOH. The results obtained in relation to enamel permeability showed that fluoride treatments temporarily reduced enamel water permeability when CaF2-like globules were removed. The in vivo perma-nence of decreased enamel permeability after CaF2 globules removal has been demon-strated for 1 h for NaF treated teeth and for at least 7 days for APF treated teeth.
Important clinical consideration moved from these results. In fact the caries-preventing action of fluoride application may be due, in part, to its ability to decrease enamel water permeability and CaF2 like-globules seem to be indirectly involved in enamel protection over time maintaining low permeability.
Others results obtained by metallographic microscope and SEM/EDX analyses of or-thodontic resins fluoride releasing and not demonstrated the relevance of topical fluo-ride application in decreasing the demineralization marks and modifying the chemical composition of the enamel in the treated area.
These data obtained in both the experiments confirmed the efficacy of fluoride in caries prevention and contribute to clarify its mechanism of action.
Adhesive dentistry is the gold standard for caries treatment and tooth rehabilitation and is founded on important chemical and physical principles involving both enamel and dentine substrates.
Particularly acid etching of dental enamel enamel has usually employed in bonding pro-cedures increasing microscopic roughness. Different acids have been tested in the litera-ture suggesting several etching procedures. The acid-induced structural transformations in enamel after different etching treatments by means of Raman and IR spectroscopy analysis were evaluated and these findings were correlated with enamel permeability. Conventional etching with 37% phosphoric acid gel (H3PO4) for 30 s and etching with 15 % HCl for 120 s were investigated.
Raman and IR spectroscopy showed that the treatment with both hydrochloric and phosphoric acids induced a decrease in the carbonate content of the enamel apatite. At the same time, both acids induced the formation of HPO42- ions. After H3PO4 treatment the bands due to the organic component of enamel decreased in intensity, while in-creased after HCl treatment.
Replicas of H3PO4 treated enamel showed a strongly reduced permeability while replicas of HCl 15% treated samples showed a maintained permeability. A decrease of the enamel organic component, as resulted after H3PO4 treatment, involves a decrease in enamel permeability, while the increase of the organic matter (achieved by HCl treat-ment) still maintains enamel permeability. These results suggested a correlation between the amount of the organic matter, enamel permeability and caries.
The results of the different studies carried out in this thesis contributed to clarify and improve the knowledge about enamel properties with important rebounds in theoretical and clinical aspects of Dentistry.
39
Bertacci, Angelica <1977>. "Evaluation of fluid transport processes in dental enamel. Methods to assess the relevance of enamel permeability in caries prevention and etching treatments". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1561/.
Testo completoAbstract (sommario):
This thesis evaluated in vivo and in vitro enamel permeability in different physiological and clinical conditions by means of SEM inspection of replicas of enamel surface obtained from polyvinyl siloxane impressions subsequently later cast in polyether impression ma-terial. This technique, not invasive and risk-free, allows the evaluation of fluid outflow from enamel surface and is able to detect the presence of small quantities of fluid, visu-alized as droplets. Fluid outflow on enamel surface represents enamel permeability. This property has a paramount importance in enamel physiolgy and pathology although its ef-fective role in adhesion, caries pathogenesis and prevention today is still not fully under-stood.
The aim of the studies proposed was to evaluate enamel permeability changes in differ-ent conditions and to correlate the findings with the actual knowledge about enamel physiology, caries pathogenesis, fluoride and etchinhg treatments. To obtain confirmed data the replica technique has been supported by others specific techniques such as Ra-man and IR spectroscopy and EDX analysis.
The first study carried out visualized fluid movement through dental enamel in vivo con-firmed that enamel is a permeable substrate and demonstrated that age and enamel per-meability are closely related. Examined samples from subjects of different ages showed a decreasing number and size of droplets with increasing age: freshly erupted permanent teeth showed many droplets covering the entire enamel surface. Droplets in permanent teeth were prominent along enamel perikymata.
These results obtained through SEM inspection of replicas allowed innovative remarks in enamel physiology. An analogous testing has been developed for evaluation of enamel permeability in primary enamel. The results of this second study showed that primary enamel revealed a substantive permeability with droplets covering the entire enamel sur-face without any specific localization accordingly with histological features, without changes during aging signs of post-eruptive maturation. These results confirmed clinical data that showed a higher caries susceptibility for primary enamel and suggested a strong relationship between this one and enamel permeability.
Topical fluoride application represents the gold standard for caries prevention although the mechanism of cariostatic effect of fluoride still needs to be clarified. The effects of topical fluoride application on enamel permeability were evaluated. Particularly two dif-ferent treatments (NaF and APF), with different pH, were examined. The major product of topical fluoride application was the deposition of CaF2-like globules. Replicas inspec-tion before and after both treatments at different times intervals and after specific addi-tional clinical interventions showed that such globule formed in vivo could be removed by professional toothbrushing, sonically and chemically by KOH. The results obtained in relation to enamel permeability showed that fluoride treatments temporarily reduced enamel water permeability when CaF2-like globules were removed. The in vivo perma-nence of decreased enamel permeability after CaF2 globules removal has been demon-strated for 1 h for NaF treated teeth and for at least 7 days for APF treated teeth.
Important clinical consideration moved from these results. In fact the caries-preventing action of fluoride application may be due, in part, to its ability to decrease enamel water permeability and CaF2 like-globules seem to be indirectly involved in enamel protection over time maintaining low permeability.
Others results obtained by metallographic microscope and SEM/EDX analyses of or-thodontic resins fluoride releasing and not demonstrated the relevance of topical fluo-ride application in decreasing the demineralization marks and modifying the chemical composition of the enamel in the treated area.
These data obtained in both the experiments confirmed the efficacy of fluoride in caries prevention and contribute to clarify its mechanism of action.
Adhesive dentistry is the gold standard for caries treatment and tooth rehabilitation and is founded on important chemical and physical principles involving both enamel and dentine substrates.
Particularly acid etching of dental enamel enamel has usually employed in bonding pro-cedures increasing microscopic roughness. Different acids have been tested in the litera-ture suggesting several etching procedures. The acid-induced structural transformations in enamel after different etching treatments by means of Raman and IR spectroscopy analysis were evaluated and these findings were correlated with enamel permeability. Conventional etching with 37% phosphoric acid gel (H3PO4) for 30 s and etching with 15 % HCl for 120 s were investigated.
Raman and IR spectroscopy showed that the treatment with both hydrochloric and phosphoric acids induced a decrease in the carbonate content of the enamel apatite. At the same time, both acids induced the formation of HPO42- ions. After H3PO4 treatment the bands due to the organic component of enamel decreased in intensity, while in-creased after HCl treatment.
Replicas of H3PO4 treated enamel showed a strongly reduced permeability while replicas of HCl 15% treated samples showed a maintained permeability. A decrease of the enamel organic component, as resulted after H3PO4 treatment, involves a decrease in enamel permeability, while the increase of the organic matter (achieved by HCl treat-ment) still maintains enamel permeability. These results suggested a correlation between the amount of the organic matter, enamel permeability and caries.
The results of the different studies carried out in this thesis contributed to clarify and improve the knowledge about enamel properties with important rebounds in theoretical and clinical aspects of Dentistry.
40
Song, Rhan-Ju. "Developmental defects of enamel in the Maya of Altun Ha, Belize implications for Ancient Maya childhood health". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21702.pdf.
Testo completo
41
Hodnett, Spencer. "The protective potential of paste containing casein phosphopeptide-amorphous calcium phosphate as measured by confocal microscopy an in vitro study /". Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5051.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains ix, 113 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 69-79).
42
Eimar, Hazem. "Tooth enamel ultrastructure: correlation between composition and physical properties". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106624.
Testo completoAbstract (sommario):
Tooth enamel is one of the hardest materials found in the animal kingdom. Accordingly, understanding its unique characteristics is of special interest for the interpretation of distinct tooth physical properties and for the development of new synthetic materials. Enamel is a composite material that comprises an inorganic matrix composed of hierarchically organized carbonated hydroxyapatite (HA) crystals, and an organic matrix mainly composed of the protein amelogenin. This study was designed to investigate how variations in enamel ultrastructure and chemical composition (organic and inorganic) may affect tooth mechanical and optical properties.One hundred extracted sound teeth were collected from adult patients attending McGill Undergraduate Dental Clinic. Vickers microindentation, Shade spectrophotometry, FTIR, SEM-EDS and XRD were used to asses enamel microhardness, tooth shade (registered in universal shade parameters: lightness, chroma and hue), chemical composition and crystallography (i.e. crystal size, lattice parameters of the crystal; a-axis and c-axis). The data obtained was analyzed for correlation, and statistical significance was set at P <0.05. Tooth enamel crystallographic structure, chemical composition, optical and mechanical properties varied dramatically within the studied population. Tooth enamel microhardness was affected by the size of its HA crystals (R= -0.476, B= -0.028, P= <0.001). Tooth shade hue was influenced by enamel HA crystal size (R= -0.358, B= -0.866, P= 0.007), tooth shade chroma was influenced by enamel HA carbonization (R= -0.419, B= -99.06, P= <0.001), and tooth shade lightness was influenced by both enamel HA crystal size (R= -0.313, B= -1.052, P= 0.019) and the degree of HA carbonization (R= -0.265, B= -57.95, P= 0.033). On the other hand, tooth enamel HA crystal size was inversely correlated with the organic relative content within tooth enamel (R= -0.352, B= -19.4, P= 0.016).This study highlights the variation in tooth enamel ultrastructure and chemical composition, and their association with its optical and mechanical properties. For instance, we have revealed that the organic content in teeth indirectly regulates enamel mechanical and optical properties by controlling the size of HA crystals. On the other hand, variation in the degree of enamel HA carbonization can also affect the tooth optical properties.L'émail des dents est un des matériaux les plus durs chez les animaux. En conséquence, la compréhension de ses propriétés uniques est d'un intérêt particulier pour l'interprétation les propriétés physiques distinctes de la dent, et pour le développement de nouveaux matériaux synthétiques. L'émail est un matériau composite qui contient une matrice inorganique de cristaux d'hydroxyapatite (HA) carbonatés et organisés hiérarchiquement, et une matrice organique composée principalement de la protéine Amelogenin. Cette étude a été désignée pour étudier comment les variations de l'ultra structure de l'émail et la composition chimique (organique et inorganique) peuvent affecter les propriétés mécaniques et optiques des dents. Une centaine des dents saines ont été extraites et recueillies auprès des patients adultes présentés à la clinique dentaire de premier cycle de l'Université McGill. Microindentation Vickers, la couleur spectrophotométrique, FTIR, SEM-EDS et XRD ont été utilisés pour évaluer la microdureté de l'émail, la couleur de la dent (enregistrée selon les paramètres universelles: la luminosité, la saturation et la teinte) et la composition chimique et cristallographique (i.e. la grandeur des cristaux, les paramètres de treillis du cristal; axe a et c). Les données obtenues ont été analysées pour la corrélation. Le niveau de signification statistique a été déterminé pour une valeur de P <0.05.La structure cristallographique de l'émail de la dent, la composition chimique, les propriétés optiques et mécaniques ont été variées considérablement au sein de la population étudiée. La microdureté de l'émail des dents a été influencée par la grandeur de ses cristaux HA (R= -0.476, B= -0.028, P= <0.001). La teinte de la dent a été influencée par la grandeur des cristaux HA de l'émail (R= -0.358, B= -0.866, P=0.007), la saturation a été influencée par la carbonisation de l'HA de l'émail (R= -0.420, B= -99.06, P= <0.001) et la luminosité a été influencée par les deux la grandeur des cristaux de l'HA de l'émail (R= -0.313, B= -1.052, P= 0.019), et le degré de carbonisation de l'HA (R= -0.266, B= -57.95, P= 0.034). D'autre part, la grandeur des cristaux de l'HA de l'émail à été inversement corrélée avec son teneur relative en matière organique (R = -0.352, B= -19.4, P= 0.016). Dans la présente étude, nous avons dévoilé que la variation de l'ultra structure de l'émail des dents et son composition chimique peuvent influencer les propriétés optiques et mécaniques de la dent. Par exemple, nous avons montré que la teneur en matière organique de l'émail des dents contrôle les propriétés mécaniques et optiques en contrôlant la grandeur des cristaux de l'HA. Par contre, la variation dans le degré de carbonisation de l'HA de l'émail peut également affecter les propriétés optiques des dents.
43
Jonas, M. "Electron spin resonance dating and dosimetry of tooth enamel". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.605678.
Testo completoAbstract (sommario):
Electron spin resonance (ESR) dating is an absolute dating method suitable for the Quaternary (up to 2 million years for tooth enamel). It is based on determining the natural radiation dose to which a sample has been exposed during its burial period. Two methods of deconvolution of ESR spectra are demonstrated. It is argued that the use of integrated spectra is most suitable for dating and dosimetry. This method is applied to the ESR dating signal in fossil tooth enamel. Initially, two models is given consistent results. A broad underlying isotropic signal at g=2.007 is found regardless of the model applied. Q-band ESR spectra of fossil tooth enamel are consistent with a model that describes the spectrum as a superposition of an axialsymmetrically split signal and two isotropic signals. A narrow additional signal is also observed which may interfere with dose response curves. ESR spectra of unirradiated and irradiated aliquots of five samples of Quaternary enamel have been deconvoluted, and growth curves have been generated for each signal component. A model is presented that describes the radiation response of a polycrystalline material. The assumptions underlying the model, the resulting differential equations and a numerical method by which they an be resolved are presented. The model parameters and their correlation with real-world parameters are discussed. The properties of the model and the scope of calculations that can be performed are demonstrated. Tooth enamel has been irradiated in a white synchrotron radiation beam and saturation of the spin concentration has been observed. An absolute spin concentration at saturation of about 3x1017 spins/cm3 for each of the signal components has been found. The directly measured values agree with saturation concentrations determined by extrapolation from fossil tooth enamel. These results support the possibility of a universal growth curve for tooth enamel.
44
Bullion, S. K. "Incremental structures of enamel and their applications to archaeology". Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381241.
Testo completo
45
Hobson, Ross S. "Factors affecting the resin to enamel bond in orthodontics". Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310170.
Testo completo
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Willmot, Derrick Robert. "Measurement of demineralised white enamel associated with orthodontic treatment". Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340219.
Testo completo
47
Patel, V. "Proteomic studies into the pathogenesis of Enamel Renal Syndrome". Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10044766/.
Testo completoAbstract (sommario):
Background: Enamel Renal Syndrome is an autosomal recessive disorder that is characterised by nephrocalcinosis and amelogenesis imperfecta where the causative gene is FAM20A. Unlike most cases of nephrocalcinosis where hypercalciuria is its instrumental cause, patients with ERS have normocalciuria, suggesting an atypical mechanism in calcium handling by the kidneys. Methods: Detection of recombinant FAM20A was performed on HeLa cells and its culture media by Western analysis. Plasma and gingival fibroblasts were used for the detection of FAM20A in control and ERS samples by two-dimensional gel electrophoresis. Human milk was utilised for the quantitation of FAM20A using both shotgun and targeted proteomics approach. Mouse kidneys were used for differential protein expression and functional proteomic analysis to help understand how the absence of FAM20A can severely impact calcium homeostasis. Results: A low amount of FAM20A was detected in human milk. Results from plasma samples and gingival fibroblasts were inconclusive. Differential protein expression profiling of kidneys revealed S100 calcium-binding protein A9 to be 2.9 fold up-regulated in the Fam20a knockout mouse. This protein is a major determinant of arterial calcification. Functional analysis indicated disturbed calcium-regulation mediated by mitochondria and peroxisomes in the absence of Fam20a. Conclusion: The removal of FAM20A triggers a disruptive ripple in the finely tuned intricate pathway of proteins all entangled to regulate calcium homeostasis; a consequence of which leads to ectopic calcification within the interstitium.
48
Lewis, Jamie. "Lying through your teeth : strontium diagenesis in archaeological enamel". Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.686171.
Testo completoAbstract (sommario):
Strontium isotopes are one of the most effective means to characterise mobility in past societies. However the technique proceeds on the basis that Sr recovered from archaeological calcified tissues is biogenic in origin and has not been contaminated by exogenous Sr. Whilst archaeological bone has been shown to be susceptible to uptake of diagenetic Sr, enamel appears to be resistant to alteration. However tooth enamel is the same mineral as bone and is in contact with the same burial environment so why should it be completely immune to diagenesis? This thesis attempts to investigate Sr uptake in archaeological enamel. From an assessment of the literature and trace element uptake models it is clear that uptake of diagenetic Sr into teeth will cause mixing of diagenetic and biogenic Sr in enamel. Thus detection of diagenetic Sr in teeth requires accurate and precise measurements of ⁸⁷Sr/⁸⁶Sr with high spatial resolution. LA-MC-ICP-MS is ideally suited to this but its application to bioapatites is challenging due to isobaric interferences. Here a method is presented which uses a customised plasma interface to reduce the effect of isobaric interferences and enable accurate and precise determinations of ⁸⁷Sr/⁸⁶Sr by LA-MC-ICP-MS. Diagenetic uptake of Sr into archaeological enamel should also cause mixing of biogenic and diagenetic Sr in stable isotope space. Thus if Sr isotopes could be shown to undergo mass dependent fractionation with trophic level this could be used to detect diagenetic Sr. Here stable Sr fractionation is demonstrated between the feed and dental tissues of a cohort of pigs raised on controlled diets. The results show a 0.3 %0 shift in δ⁸⁸Sr with trophic level. The rate and likely mechanism for Sr uptake in bone is assessed by measuring Sr concentration profiles in a suite of archaeological bones by LA-ICP-MS. The results show that the most likely mechanism for Sr uptake is by diffusion with adsorption. Bone is expected to reach equilibrium with the burial environment between 2,200 and 4,000 years, however the biogenic Sr isotope ratio is likely to be compromised long before equilibrium is reached. Strontium concentration, ⁸⁷Sr/⁸⁶Sr and δ⁸⁸Sr profiles are measured in a series of archaeological teeth to assess diagenetic uptake of Sr. Diagenetic uptake of Sr in archaeological enamel is detected with all three of these techniques. Uptake in enamel is consistent with a model of diffusion with adsorption and enamel is likely to reach equilibrium with the burial environment in 67,000 ± 26,000 years. However the biogenic Sr isotope signal will be compromised on significantly shorter time scales. Comparisons of measured uptake profiles with uptake models allows for current enamel decontamination procedures to be assessed. For Holocene age teeth, current decontamination methods are likely sufficient to remove diagenetically altered enamel. For older teeth, whilst decontamination procedures will remove some diagenetic Sr and LA-MC-ICP-MS methods may help to resolve mixing of diagenetic and biogenic Sr for some teeth it will only be possible to return an approximation of the biogenic Sr isotope ratio.
49
Verma, Shefalee. "Effects of fluoridated milk on artificial enamel carious lesions". Thesis, Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B41758201.
Testo completo
50
Bullion, Simone Katrina. "Incremental structures of enamel and their applications to archaeology". Online version, 1987. http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.381241.
Testo completo