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Early Application of Laser-Activated Irrigation During Root Canal Debridement
No full textReducing microorganisms and intracanal debris is a central goal of chemomechanical preparation. A crown-down approach to cleaning and shaping the root canal system has been recommended to extrude less debris into the periapical tissues in infected root canals. The aim of this study was to investigate the impact of a crowndown irrigation approach involving the application of an early step of laser-activated irrigation (LAI) before establishing initial patency or completing instrumentation. The impact of early LAI on time required to achieve initial patency and canal cleanliness was investigated and compared to conventional needle irrigation (CNI).
The mesiobuccal (MB) and distobuccal (DB) roots of 65 extracted human permanent maxillary molars were included in the study. One hundred twenty roots underwent the patency investigation where root canals were treated according to a LAI or CNI irrigation protocol using 3% sodium hypochlorite (NaOCl) early in chemomechanical preparation before patency was established or manual instrumentation was completed. Time required to achieve initial patency was recorded. A scanning electron microscopic (SEM) investigation was then performed using 10 root canals from each irrigation protocol and five additional control root canals. The quantity of debris remaining on the root canal walls was analyzed.
The Mann-Whitney U test found no significant difference in time required to establish initial patency between groups (p = .534). In the SEM investigation, the Kruskal-Wallis test revealed a significant difference in the debris scores among LAI CNI, and control groups (p < .001). The LAI group had significantly lower debris scores than the control and CNI groups (p < .001).
Early implementation of the laser in the chemo-mechanical preparation of root canals had no measurable impact on time required to establish initial apical patency. However, within the parameters of the study, early LAI with NaOCl resulted in a significant reduction in the amount of debris remaining on root canal walls compared to CNI and control root canals
Starsky & Hutch Concordance
No full textPossibly published in the 1980s.Also known as: Starsky & Hutch Concordance
Exploiting Sulfur(VI) Fluoride Exchange Click Chemistry for Efficient Synthesis of Degradable Polysulfamides
Get PDFPlastic waste accumulation has emerged as a severe environmental issue since last century, resulting in short-term-irreparable damage to the marine ecosystem. One strategy to help solve this critical problem relies on the design of chemically recyclable or upcyclable polymers as alternatives to conventional plastics. To identify such polymers, our approach is based on molecular editing of known soft materials. We hypothesize that small modification of the polymer architecture might preserve or even improve its physical properties, while imparting improved degradability for recycling or upcycling. For example, replacing the repeating carbonyl functional group (���CO���) present in high-commodity polyureas by a ���SO2��� motif would provide polysulfamides, a virtually unknown family of polymers. Polysulfamides could provide a more sustainable alternative to polyureas that are known to be challenging to degrade.
This dissertation first discuss the design of a synthesis of N,N���-disubstituted sulfamides through Sulfur Fluoride Exchange (SuFEx) click chemistry. Our initial strategy to access polysulfamides relied on A2B2 monomers featuring bis(sulfamoyl fluoride)s and readily available bis(amine)s. Polymers with diverse backbones and improved molar masses compared to prior studies were prepared through this A2B2 strategy. Additionally, polysulfamides showcased high thermal stability, as well as tunable glass-transition temperatures. The instability of a couple of bis(sulfamoyl fluoride) monomers prompted us to explore an ���AB��� strategy featuring Boc-protected AB monomer precursors. Acidic deprotection allowed the formation of stable ammonium AB monomers, which were subsequently polymerized upon the addition of a base. To our delight, by taking advantage of the built-in 1:1 functional group, we found the AB strategy delivered similar to higher molar masses of polysulfamides than our previous study.
We tested the degradability of all synthesized polymers in aqueous media and we found that aryl-based polysulfamides were fully hydrolyzed in a HCl solution at 120 ��C with high recovery yields (>80%) of the bis(amine) monomers. In contrast, alkyl-based polysulfamides did not degrade in these conditions, which led us to develop an oxidative method to degrade these polymers. Upon subjection to a solution of commercial bleach and sodium hydroxide solution, bis(carboxylic acid)s were isolated in low to high yields. Because such compounds are common monomers for polyesters including polyethylene terephthalate (PET), this oxidative process can be regarded as an upcycling of alkyl-based polysulfamides.
Finally, to gain insights in the physical properties of polysulfamides, a key step for their implementation as plastic materials, we explored their assembly driven by hydrogen bonding in a dual experimental/computational study. Techniques including powder X-ray diffraction (PXRD) and FTIR spectroscopy, were combined with a coarse-grained (CG) model and molecular dynamics (MD) developed by the Jayaraman group at the University of Delaware. Following experimental validation of the computational model, the influence of various parameters including bulkiness, length, and uniformity in length of the repeating units was investigated. The bulkiness and length of repeating units have been identified thus far are critical parameters affecting the polymer assembly
