Thesis--University of Turku, 1999. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (Ph. D.)--University of Maryland, 1998. / Includes bibliographical references.

Thesis (doctoral)--Katholieke Universiteit te Nijmegen, 1988. / Text in English with a summary in Dutch. "Een wetenschappelijke proeve op het gebied van geneeskunde en tandheelkunde"--T.p. Includes bibliographical references.

Universiẗat, Diss., 2002--Mainz.

Indiana University-Purdue University Indianapolis (IUPUI) / Clinical studies on composite resins in Class II Resotrations place in adults indicate that wear is the predominant problem. However, little has been published on the use of composites for such restorations in primary teeth. The purpose of this study was to compare amalgam to composite resins in such restorations. Two composite resins (Adaptic and Radio-opaque Adaptic) served as the Experiemental material and amalgam, (Dispersalloy) was the control . One operator placed 57 sets, one restoration of each of the three materials per set, in 50 patients at the Riley Children's Hospital in Indianapolis. Evaluations were made at baseline, six months, one year, two years, and three years using the Ryge-USPHS criteria and by means of casts poured from elastomeric impressions. Results of the Ryge-USPHS criteria indicated no wear or color change of the composites after two years (p=N.S.). However, of the 49 sets that returned at one year, two composites had caries around the restoration. This particular observation was monitored at the three-year time interval and found not to increase around any other composite restorations. Composite restorations in posterior primary teeth compared equally to amalgam (Dispersalloy) for the first two years of the project. The loss of anatomic form was significant after three years (p=.05).

Indiana University-Purdue University Indianapolis (IUPUI) / The investigation was undertaken to determine the effects of the polishing and finishing of dental amalgam in relation to its marginal breakdown. The study was also conducted to make a clinical comparison of the marginal integrity of Dispersalloy restorations as compared to Twentieth Century Fine Cut Alloy restorations in both the polished and unpolished state. Forty patients with a total of 131 Class I amalgam restorations were used as the study group. The two alloy systems and polish or unpolish techniques were selected from a random table. Photographic evaluation of the restorations was used to judge the degree of marginal breakdown. The results of the study at the one-year evaluation show two main findings: (1) the Dispersalloy restorations showed less marginal breakdown than the Twentieth Century Fine Cut Alloy restorations, and (2) there was no significant difference between the polished and unpolished restorations overall.

Concerns arise in radiation therapy for head and neck cancers when dental prostheses are involved. These prostheses are high-density materials that induce image artifacts in computed tomography (CT) scans used for dose calculation. Two approaches are utilized in mitigating the impact of these artifacts on the accuracy of dose calculation. First, metal artifact reduction (MAR) algorithms or dual-energy CT scans are used to recover image quality. Second, a planning protocol is adopted whereby residual artifacts are manually contoured and assigned appropriate densities. This study evaluated the current planning process using a holistic approach. In this work, an axial section of a head phantom containing dental implants at the level of the oral cavity was constructed and scanned using various protocols on two different commercial scanners; Philips and Siemens, to assess the appearance of artifacts. An MVCT image set was merged with the corresponding kVCT image to improve visualization of the dental implants for use in density overrides. Three ion chamber measurement points in the simulated mouth facilitated the determination of measured dose which was compared to calculated dose at various single beam irradiation geometries. The influence of density override values on agreement between calculation and measurement was investigated for each geometry and imaging modality. Percent error was computed, and initial results compared to results manipulated by use of; a CT density table (Head); density overrides of walls and wax; and density overrides of walls, wax, and effective density of saturation regions. The study established that normal tissue doses are not significantly affected by metal artifact reduction (MAR) algorithms, and improvements in dose calculation compared to uncorrected CT images are small. Furthermore, the inclusion of a MVCT image set improved implant visualization reducing the treatment planning time while providing more information. Evidence led to the deduction that manual overrides of effective density for clipped OMAR CT pixels reduce dose calculation errors. When the phantom was configured with amalgam and Co-Cr-Mo alloy dental implants the effective density of these implants was found to be 4.5 g/cm3. When the phantom was configured with implants containing amalgam and gold, the effective density of amalgam in the presence of gold was 5.5 g/cm3 while gold had an effective density of 6.5 g/cm3. The median and maximum range of errors for the uncorrected images were ± 0.6 % and 7.4% respectively for the phantom configured with amalgam and Co-Cr-Mo (tray one) and ± 0.5 % and 18.1 % respectively for the phantom containing amalgam and gold (tray two). The median and maximum range of errors for the corrected images after applying overrides of effective densities were ± 0.5 % and 4.7% respectively for tray one and ± 0.3 % and 7.7 % respectively for tray two. In conclusion, introduction of density overrides of walls, wax and effective density of high-density materials can reduce the errors induced by metal artifacts and improve the accuracy of dose calculations in treatment planning systems to deliver the relevant dose to a target organ. / Thesis / Master of Science (MSc)

Avaliaram-se clinicamente e por meio de radiografias interproximais, 558 restaurações de amálgama e 81 de resina composta em dentes posteriores, em 96 pacientes adultos atendidos na disciplina de Clínica Integrada da Faculdade de Odontologia da Universidade de São Paulo. Foram registrados os seguintes critérios: cárie secundária, falta de integridade marginal, falta de contato interproximal, condição da superfície oclusal das restaurações, falta de material restaurador, presença de fratura da restauração ou do dente e excessos interproximais, enumerados de 1 a 7, respectivamente. Somente foi considerado 1 critério para cada restauração. Coletaram-se informações referentes à idade, gênero, presença de doenças sistêmicas, dieta, índice de placa bacteriana, freqüência de escovação, uso do fio dental e substâncias fluoretadas para bochecho. A análise estatística baseou-se nos testes de qui-quadrado e exato de Fisher. A análise clínica das restaurações dentárias demonstrou que das 639 restaurações avaliadas, 325 apresentaram um dos critérios utilizados, sendo o critério 4 (oxidação, corrosão e descoloração aceitável) mais freqüente, seguido do critério 1 (cárie secundária). Pode-se concluir que: o principal defeito identificado nas restaurações de amálgama foi oxidação e sobrecontorno (50,34%), seguido de cárie secundária (19,33%); enquanto que para as resinas compostas foi cárie secundária (40%), seguido de alteração de cor aceitável (28%); houve associação entre o tipo de material restaurador (amálgama) e o critério 4 (corrosão e oxidação, p<0,0001) o que 8 não ocorreu com os demais critérios; houve associação entre placa bacteriana e cárie secundária (p=0,046), não houve associação entre placa bacteriana e gênero (p=0,755), não houve associação entre cárie secundária e dieta (p=0,407), cárie secundária e relato de doenças (p=0,329), cárie secundária e freqüência de escovação (p= 0,745) e placa bacteriana e freqüência de escovação (p= 0,903). / It was clinical evaluated 558 amalgam restorations and 81 resin restorations in posterior teeth. It was registered in a own paper these failures of restorations: secondary caries, defective margins, contact faulty, loose of restorative material, poor conditions of oclusal surface restoration, fracture of restoration or fracture of tooth structure and interproximal cervical area over contoured. These failures were recorded by the number one until seven, in order. It was evaluated 96 adults patients from Clínica Integrada in FOUSP. To determine the conditions of oral environment of these patients were asked to them about age; sex; the conditions of health; dietary, act of dental brushing, use of fluoride substances, use of dental prosthetics and buccal open in millimeters. The data were then analyzed by chi-quadrado and Fisher tests. The clinical analyze showed that 325 restorations had failures and the most failure was poor conditions of oclusal surface restorations and secondary caries. An overall view of the results allowed to conclude that main failure in amalgam restorations was poor conditions of oclusal surface restorations (50,34%) and secondary caries (19,33%); related to resins was secondary caries (40%) and inadequate color (28%); there was association between 4 criteria and amalgam restorations (p<0.0001), there was association between plaque and secondary caries (p= 0,046); there wasn’t association between caries and act of brushing (p=10 0,745), caries and dietary (p= 0,407), caries and diseases (p= 0,329), plaque and gender (p= 0,755) and plaque and act of brushing (p=0,903).

This thesis focuses on in-situ studies at the solid-liquid interface by combining scanning electrochemical microscopy (SECM) with gold and platinum mercury amalgam microelectrodes. It is shown that stripping voltammetry experiments at imaging amalgam microelectrodes provide laterally resolved insight on the electrochemistry of biogeochemically relevant processes. SECM provides information on electroactive surface processes with high spatial resolution, and offers the opportunity to study heterogeneous electron-transfer reactions. Thereby, chemical species of interest, such as metal ions, can be electrochemically detected at mercury amalgam electrodes. Platinum and gold mercury amalgam microelectrodes were developed for the detection of biogeochemically relevant analytes such as manganese and iron during SECM imaging experiments at the mineral/water interface establishing the fundamental basis of SECM imaging with amalgam microelectrodes. SECM experiments were performed for the quantitative determination of Mn2+ during the dissolution of microstructured manganese carbonate (rhodochrosite) precipitates at mildly acidic conditions. SECM images along with spatially resolved quantitative data on the Mn2+ concentration were obtained. This measurement concept was then extended to the investigation of the corrosion behavior of diamond-like carbon (DLC) protected zinc selenide (ZnSe) waveguides applied in mid-infrared attenuated total reflectance spectroscopy at strongly oxidizing conditions. The corrosion behavior of DLC coated and uncoated ZnSe crystals was studied obtaining laterally resolved information on the oxidative degradation of ZnSe at defects of the DLC layer utilizing SECM in combination with square wave anodic stripping voltammetry (SWASV) at gold amalgam microelectrodes. Thereby, insight on the corrosion behavior of ZnSe and concentration profiles of Zn2+ at oxidizing conditions was obtained. These results corroborate the utility of SECM imaging with amalgam microelectrodes for addressing relevant analytical questions. Finally, the developed amalgam microelectrodes were applied for SECM studies of iron-reducing proteins separated from Shewanella microbes in native polyacrylamide gels. After calibration of Pt/Hg microelectrodes in bulk solution for the targeted analytes (iron and sulfur species), SECM approach curves recorded above the native gel enabled positioning of the amalgam electrode in close proximity above protein bands with suspected iron-reducing activity. This technique enabled the (semi)quantitative determination of the anaerobic respiratory activity associated with microbial proteins/protein complexes responsible for the reductive dissolution of manganese and iron oxides above microbial protein bands separated in a native gel matrix.

Mercury amalgam microelectrodes, typically fabricated by electrodeposition of mercury onto metal (platinum, gold, silver) inlaid disks, possess certain advantageous properties for scanning electrochemical microscopy (SECM) and electroanalysis. But as applications require more and more precision, fundamental questions concerning the exact shape and constitution of the amalgam can become important for interpreting SECM experimental data. The purpose of this study is to analyze in depth the formation of the amalgam, in order to provide a better understanding of the key physical processes, and so be able to judge of the accuracy of the currently used models and refine them when necessary. The amalgam formation is the result of several processes that occur roughly at two different scales: the global scale, which is microscopic, and the local scale, of the order of few nanometers. On the global scale, the dominant physical process is the mass transport, driven almost entirely by diffusion, which determines the rate of mercury deposition. Other phenomena occur at the smaller local scale. Their understanding is essential to predict precisely the volume and shape of the amalgam at shorter times. Among these local phenomena, nucleation and droplet interactions appear critical. The former sets the formation rate and the size of the isolated mercury droplets that are initially formed at the surface of the electrode. An understanding of the latter is necessary to determine the droplet coalescence process. Among the specific accomplishments of this Master thesis work, a time scale analysis of the global phenomena has been performed leading to the conclusion that quasi-steady state diffusion of mercury ions in the bulk mainly defines the electrodeposition rate. Then, a series of analytical formulations for diffusion-limited electrodeposition current available in the literature has been quickly analyzed, leading to development of analytical/numerical models. These latter have been implemented, and results were critically compared with experimental data, leading to the conclusion that the early electrodeposition was not enough finely modeled. Mercury droplets nucleation and surface interaction have been identified as relevant processes of this period. They have next been investigated in detail, leading to the characterization of the nucleation process, and the derivation of two complimentary approaches on charged droplet stability. Regime maps have been developed, providing first explanations and quantitative information on charged droplet stability dependence on potential applied, electrolyte and droplet size. Finally, through analysis of theoretical predictions, a series of electroanalytical experiments have been proposed for the future validation of the suggested theoretical models.