Saudi Cultural Missions Theses & Dissertations
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Item Restricted Development and Optimization of a Microwave and Plasma Treatment System(2024-12) Alfawaz, saleh Abdullah; El-Ghazaly, Samir MThis dissertation details the development and optimization of a microwave and plasma disinfection system aimed at enhancing microbial inactivation for applications in healthcare, food safety, and environmental sanitation. The system integrates microwave and plasma technologies to leverage their synergistic effects. Microwave radiation provides rapid volumetric heating, disrupting microbial cells through thermal mechanisms, while plasma technology introduces reactive species that inactivate microorganisms via non-thermal pathways. This combination seeks comprehensive disinfection by utilizing microwaves' deep penetration and plasma's potent surface sterilization. A primary challenge addressed is precise temperature control to prevent overheating and ensure consistent disinfection efficacy. The system employs a solid-state microwave generator operating at 2.45 GHz with adjustable power from 140 W to 1400 W. Microwave energy is directed through a WR340 waveguide into a modified cavity with metal plates to prevent leakage and ventilation holes for airflow management. A WR340 horn antenna delivers microwaves directly to samples placed on a stationary glass plate within the cavity. For accurate temperature monitoring and control, the system uses both infrared (IR) and fiber optic (FO) temperature sensors. The FO sensor, immune to electromagnetic interference, provides real-time temperature data inside the microwave cavity. This data is processed by a Python-based control program that dynamically adjusts microwave power to maintain the sample temperature within a desired range, preventing overheating and material degradation. An atmospheric-pressure plasma jet is integrated into the cavity, introducing plasma above the sample. The plasma operates alongside the microwave system, either sequentially or simultaneously, enhancing disinfection through reactive species like radicals and ions. The synergy between microwave heating and plasma-induced chemical reactions results in more effective microbial inactivation. Experimental evaluations were conducted on various microorganisms, including Escherichia coli, yeast, and influenza A virus. The study explored different treatment parameters, such as microwave power levels (200 W, 400 W, 600 W), exposure times, and the effects of predefined microwave on/off cycles versus real-time temperature feedback control. Incorporating the FO sensor improved temperature regulation, leading to more consistent microbial inactivation compared to systems relying solely on IR sensors. Results demonstrated that the optimized system effectively inactivated a broad spectrum of microorganisms while preventing overheating and preserving material integrity. Predefined microwave cycles standardized pathogen exposure durations, enhancing the reproducibility and reliability of the disinfection process. Combining microwave and plasma treatments achieved higher disinfection efficacy than either method alone, confirming the benefits of their synergistic application. This research advances microwave and plasma disinfection technologies by providing practical solutions for system optimization and temperature control. The developed system addresses key challenges in the field, offering an efficient alternative to conventional sterilization methods. The findings have significant implications for applications requiring rapid and reliable disinfection, aligning with the growing demands of the global sterilization and disinfection market. Future work should explore scaling the system for industrial applications, investigate the long-term effects of microwave and plasma exposure on various materials, and further examine the mechanisms behind enhanced microbial inactivation. Addressing these areas will refine the technology for broader use, contributing to improved public health and safety.16 0Item Restricted Clinical Investigation of the Impact of Endodontic Disinfection on the Bacteriome of Root Canal Infection Using Next-Generation Sequencing on the Illumina MiSeq Platform(University of Maryland, Baltimore, 2024-07-01) Alquria, Theeb; Martinho, FredericoThe primary cause of root canal infection is bacteria and their by-products, making disinfection of the root canal system a key goal in endodontic therapy. However, the complex anatomy of root canal systems, particularly the isthmus and its ramifications, poses challenges for effective disinfection. Currently, no disinfection protocol can eliminate all bacterial contents from root canal infections, driving the ongoing search for an optimal disinfection approach. Recently, next-generation sequencing (NGS), particularly the Illumina MiSeq platform, has been widely explored in endodontic infections due to its low sequencing error rates, cost-effectiveness, and high-quality reads. Leveraging advanced sequencing techniques to reveal the bacteriome of root canal infections and assess the impact of current disinfection methods could enable the development of more targeted and effective disinfection protocols. This dissertation presents an interventional clinical study aiming to investigate the diversity and composition of the bacteriome in primary endodontic infection (PEI) with apical periodontitis (AP) and evaluate the impact of root canal disinfection on the endodontic bacteriome using NGS on the Illumina MiSeq Platform. First, we characterized the bacteriome in PEI with AP, identified core and rare bacteriome species, and analyzed community diversity metrics using the Illumina MiSeq platform. Our results showed that Bacteroidetes, Firmicutes, Synergistetes, Fusobacteria, and Actinobacteria were the most abundant bacterial phyla. We identified 113 genera and 215 species. Analysis revealed differences in abundant taxa among distinct age, gender, symptomatology, and lesion size groups. These findings suggest that the bacteriome in PEI with AP is complex and has high microbial heterogeneity among patients. Moreover, age, gender, symptomatology, and lesion size might play a role in the abundant taxa present in PEI with AP. Second, we determined quantitatively and qualitatively the impact of chemomechanical preparation (CMP) using 2.5% sodium hypochlorite (NaOCl) on the bacteriome found in PEI with AP using the Illumina MiSeq platform. Despite a significant decrease in bacterial abundance, our findings demonstrated a distinct community composition and increased alpha diversity after CMP. We observed differential enrichment of specific taxa, including Stenotrophomonas_unclassified, Enterococcus_unclassified, and Actinomyces_unclassified, suggesting lower effectiveness of CMP using 2.5% NaOCl against these taxa. Findings from this dissertation highlight the complexity and heterogeneity of the bacteriome in PEI with AP, emphasizing the influence of patient-related factors on microbial diversity. The research highlighted the limited effectiveness of current endodontic disinfection protocols, specifically the use of 2.5% NaOCl, in reducing bacterial abundance while revealing limitations against certain taxa. These insights provide a foundation for developing more targeted and effective disinfection strategies, potentially leading to improved outcomes in endodontic therapy.10 0