The Effect of Bevel on Fracture Resistance of GIC Restorations in Primary Molars: In Vitro Study Rôle du Biseau dans la Résistance à la Fracture des Restaurations aux Ciments Verres-Ionomères des Molaires Temporaires : Étude In Vitro

Background: Glass ionomer cements (GICs) are commonly used for restorations in primary molars due to their adhesive, hydrophilic, and bioactive properties. However, their low mechanical resistance may limit their use in proximal cavities. Recent advancements in GICs, such as the high viscosity GIC EQUIA Forte®, have improved their mechanical properties. The effect of a Cavo superficial bevel on the mechanical strength of GIC restorations has been previously studied. Objectives: To investigate the effect of a Cavo superficial bevel on fracture resistance and the type of fracture (adhesive, cohesive, or catastrophic) in EQUIA Forte® GIC restorations in primary molars. Methods: 56 standardized proximal cavities were created on 51 temporary molars. The cavities were randomly divided into two groups: group I without a Cavo superficial bevel (n=28) and group II with a 45° Cavo superficial bevel (n=28). The cavities were restored with EQUIA Forte®. The samples were subjected to thermocycling and artificial aging, then, an axial speed loading of 1 mm/min was applied until fracture. Fracture toughness was recorded, and the type of fracture was observed under an optical microscope. A Mann-Whitney U test was used to compare the average fracture resistance between the groups. All tests were two-tailed and the level of significance was set at 5%. Results: The average fracture resistance for group I was (237.57 ± 139.97 N) and for group II was (294.89 ± 171.07 N). There was no statistically significant difference in fracture resistance between the two groups (p\u3e0.05). Mixed fractures were observed in all samples, with adhesive fractures only present in group I and cohesive fractures only present in group II. Conclusion: The Cavo superficial bevel does not significantly affect the fracture resistance of GIC restorations in primary molars. However, the bevel design may prevent adhesive and catastrophic fractures. Contexte : Les ciments verres-Ionomères (CVI) sont couramment utilisés pour les restaurations des molaires temporaires grâce à leurs propriétés adhésives, hydrophiles et bioactives. Cependant, leur faible résistance mécanique limite leur utilisation dans les cavités proximales. Avec les récents progrès de cette classe de matériaux, un CVI à haute viscosité a été introduit : EQUIA Forte®, visant à améliorer leurs propriétés mécaniques. Le rôle du biseau cavo-superficiel sur la résistance mécanique des restaurations au CVI a déjà été étudié. Objectifs : Tester le rôle du biseau dans l’amélioration de la résistance à la fracture et d’étudier la nature du trait de fracture adhésif, cohésif, ou catastrophique des restaurations aux CVI EQUIA Forte® des molaires temporaires. Méthodes : 56 cavités proximales standardisées ont été réalisées sur 51 molaires temporaires. Ces cavités ont été divisées aléatoirement en deux groupes : groupe I sans biseau cavo-superficiel (n=28) et groupe II avec biseau cavo-superficiel de 45° (n=28). Les cavités ont été restaurées par EQUIA Forte®. Les échantillons ont été soumis à un thermocyclage et à un vieillissement artificiel, puis une vitesse axiale de chargement de 1 mm/min a été appliquée jusqu\u27à la fracture. La résistance à la fracture a été enregistrée et le type de fracture a été observé au microscope optique. Le test de Mann-Whitney U a été utilisé pour comparer la résistance moyenne à la fracture entre les groupes. Tous les tests étaient bilatéraux et le niveau de signification a été fixé à 5 %. Résultats : La résistance moyenne à la fracture pour le groupe I était de (237,57 ± 139,97 N) et pour le groupe II était de (294,89 ± 171,07 N). Il n\u27y avait pas de différence statistiquement significative en termes de résistance à la fracture entre les deux groupes (p \u3e 0,05). Cependant, des fractures mixtes ont été observées dans tous les échantillons, les fractures adhésives étant uniquement présentes dans le groupe I et les fractures cohésives présentes uniquement dans le groupe II. Conclusion : Le biseau cavo-superficiel n\u27influence pas de manière significative la résistance à la fracture des restaurations CVI des molaires temporaires. Cependant, il s’est avéré que la conception du biseau empêche les fractures adhésives et catastrophiques d’avoir lieu. Mots clés : Biseau, CVI, Classe II, Molaires Temporaires, Restauration, Type de fractur

Glyoxal oxidases from Pycnoporus cinnabarinus : production, characterization and application

La biomasse végétale est une alternative durable et écologique pour les ressources fossiles. L'exploitation et la valorisation de cette biomasse sont rendues possibles grâce à la capacité naturelle des enzymes fongiques à dégrader et modifier cette biomasse. Parmi ces enzymes, les glyoxal oxydases génératrices de H2O2 (GLOX) restent un groupe peu étudié avec un seul exemple de protéine caractérisée dans la littérature à partir d’un champignon dégradant le bois.Dans cette thèse, trois GLOX, précédemment identifiées dans le génome du champignon dégradant le bois Pycnoporus cinnabarinus (PciGLOX), ont été sélectionnées, produites par voie hétérologue et caractérisées. La caractérisation a révélé des différences entre les trois PciGLOX dans la stabilité des protéines, la spécificité du substrat et l’efficacité catalytique. Les protéines PciGLOX sont produites sous leur forme inactive et leur mécanisme d'activation a été étudié. La capacité des GLOX à catalyser la réaction d'oxydation du 5-hydroxyméthylfurfural (HMF), d’intérêt industriel, a été étudiée pour la première fois dans ce travail. Le HMF a été oxydé par PciGLOX en acide 5-hydroxyméthyl-2-furancarboxylique (HMFCA) comme produit principal. Le HMFCA est difficile à produire par catalyse chimique et est utilisé dans la production de polyesters et de produits pharmaceutiques. PciGLOX ont également été capables de produire l’acide furandicarboxylique (FDCA), qui est un précurseur dans les procédés de production du bioplastique. Ce travail ouvre de nouvelles perspectives pour étudier plus en détail le rôle de GLOX dans la dégradation de la lignocellulose, et dans les applications biotechnologiques.Plant biomass is a sustainable and eco-friendly alternative for fossil fuels. The exploitation and valorisation of plant biomass is possible through biotechnological processes that rely on the natural ability of fungal enzymes to degrade and modify this biomass. Among these enzymes are H2O2-generating glyoxal oxidases (GLOX), which haven’t been extensively studied with only one example in the literature on GLOX from wood-degrading fungi. In this thesis three GLOX, previously identified in the genome of the wood-degrading fungus Pycnoporus cinnabarinus (PciGLOX), were heterologously produced and characterisation. The three PciGLOX showed differences in their stability, substrate preferences and catalytic properties. The ability of GLOX to catalyse the biotechnologically important oxidation reaction of 5-hydroxymethylfurfural (HMF) was investigated for the first time in this work. PciGLOX oxidized HMF to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), which is difficult to produce via chemical catalysis and is used in polyesters and pharmaceutical products production. PciGLOX were also able to oxidize HMF derivatives leading to the formation of the final product furandicarboxylic acid (FDCA), which is a bioplastic precursor. PciGlOX proteins are produced in their inactive form and their activation mechanism was investigated in this thesis. This work opens new prospects to investigate more the role of GLOX in plant biomass degradation and biotechnology, and the possible optimization techniques of the catalytic properties of this enzyme

Glyoxal oxidases: their nature and properties

International audienceH2O2 has been found to be required for the activity of the main microbial enzymes responsible for lignin oxidative cleavage, peroxidases. Along with other small radicals, it is implicated in the early attack of plant biomass by fungi. Among the few extracellular H2O2-generating enzymes known are the glyoxal oxidases (GLOX). GLOX is a copper-containing enzyme, sharing high similarity at the level of active site structure and chemistry with galactose oxidase. Genes encoding GLOX enzymes are widely distributed among wood-degrading fungi especially white-rot degraders, plant pathogenic and symbiotic fungi. GLOX has also been identified in plants. Although widely distributed, only few examples of characterized GLOX exist. The first characterized fungal GLOX was isolated from Phanerochaete chrysosporium. The GLOX from Utilago maydis has a role in filamentous growth and pathogenicity. More recently, two other glyoxal oxidases from the fungus Pycnoporus cinnabarinus were also characterized. In plants, GLOX from Vitis pseudor-eticulata was found to be implicated in grapevine defence mechanisms. Fungal GLOX were found to be activated by peroxidases in vitro suggesting a synergistic and regulatory relationship between these enzymes. The substrates oxidized by GLOX are mainly aldehydes generated during lignin and carbohydrates degradation. The reactions catalysed by this enzyme such as the oxidation of toxic molecules and the production of valuable compounds (organic acids) makes GLOX a promising target for biotechnological applications. This aspect on GLOX remains new and needs to be investigated

Determining the mechanisms of fungal growth and deconstruction of alkali lignins.

International audienc

Characterization of two novel hydrogen peroxide producing glyoxal oxidases from Pycnoporus cinnabarinus implicated in the breakdown of lignocelluloses

International audienc

Characterization of two novel hydrogen peroxide producing glyoxal oxidases from Pycnoporus cinnabarinus implicated in the breakdown of lignocelluloses

International audienc

Characterization and Dye Decolorization Potential of Two Laccases from the Marine-Derived Fungus <i>Pestalotiopsis</i> sp.

Two laccase-encoding genes from the marine-derived fungus Pestalotiopsis sp. have been cloned in Aspergillus niger for heterologous production, and the recombinant enzymes have been characterized to study their physicochemical properties, their ability to decolorize textile dyes for potential biotechnological applications, and their activity in the presence of sea salt. The optimal pH and temperature of PsLac1 and PsLac2 differed in relation to the substrates tested, and both enzymes were shown to be extremely stable at temperatures up to 50 &#176;C, retaining 100% activity after 3 h at 50 &#176;C. Both enzymes were stable between pH 4&#8211;6. Different substrate specificities were exhibited, and the lowest Km and highest catalytic efficiency values were obtained against syringaldazine and 2,6-dimethoxyphenol (DMP) for PsLac1 and PsLac2, respectively. The industrially important dyes&#8212;Acid Yellow, Bromo Cresol Purple, Nitrosulfonazo III, and Reactive Black 5&#8212;were more efficiently decolorized by PsLac1 in the presence of the redox mediator 1-hydroxybenzotriazole (HBT). Activities were compared in saline conditions, and PsLac2 seemed more adapted to the presence of sea salt than PsLac1. The overall surface charges of the predicted PsLac three-dimensional models showed large negatively charged surfaces for PsLac2, as found in proteins for marine organisms, and more balanced solvent exposed charges for PsLac1, as seen in proteins from terrestrial organisms

Acute Kidney Injury Post-cardiac Surgery in Infants and Children: A Single-Center Experience in a Developing Country.

Introduction: The incidence of acute kidney injury (AKI) in pediatric patients following cardiac surgery varies between 15 and 64%, with a mortality rate of 10-89% among those requiring dialysis. This variation in the incidence and mortality of AKI across studies is probably due to the inconsistent definitions used for AKI. The purpose of this study is to present our experience with AKI post-cardiac surgery with emphasis on predisposing or aggravating factors. Patients and Methods: We evaluated the incidence of AKI using the KDIGO criteria in 150 infants and children undergoing cardiac surgeries between 2015 and 2017. Post-operatively, all patients were admitted to the pediatric intensive care unit (PICU) at a tertiary care center in a developing country. This is a retrospective chart review in which data collected included age, gender, type of heart disease, prior cardiac surgeries, RACHS-1 category, and pre- and post-operative creatinine levels. Neonates were not included in this study. Results: Six percent of the studied patients were below 1 year of age, 84% 1-10 years, and 10% 10-18 years. Fourteen patients (9.3%) developed AKI. Patients with cyanotic heart disease were more prone to develop AKI (78%) compared to those with non-cyanotic heart disease (44%). Children with AKI had a higher length of stay in PICU, 2.56 ± 1.44 vs. 4 ± 2.66 (p- 0.02). Serum lactic acid was higher in patients who developed AKI with a mean value of 6.8 ± 6.9 vs. 2.85 ± 1.55 mmol/l in the non-AKI group (p- 0.03). Lower hemoglobin levels and hyperlactic acidemia were significantly more prevalent in the AKI group. There were five deaths in this series (3.3%), and four of those (80%) were in the AKI group. Conclusion: Using the KDIGO criteria, the incidence of AKI in infants and children following cardiac surgery was 9.3%. This is slightly lower than in previously published studies where the range was between 15 and 64%. Children with cyanotic cardiac disease, hyperlactic acidemia, and anemia were more prone to developing AKI. Identifying patients at risk might help decrease the risk of post-operative AKI

Gut microbiota interplay with COVID-19 reveals links to host lipid metabolism among Middle Eastern populations

The interplay between the compositional changes in the gastrointestinal microbiome, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) susceptibility and severity, and host functions is complex and yet to be fully understood. This study performed 16S rRNA gene-based microbial profiling of 143 subjects. We observed structural and compositional alterations in the gut microbiota of the SARS-CoV-2-infected group in comparison to non-infected controls. The gut microbiota composition of the SARS-CoV-2-infected individuals showed an increase in anti-inflammatory bacteria such as Faecalibacterium (p-value = 1.72 × 10–6) and Bacteroides (p-value = 5.67 × 10–8). We also revealed a higher relative abundance of the highly beneficial butyrate producers such as Anaerostipes (p-value = 1.75 × 10–230), Lachnospiraceae (p-value = 7.14 × 10–65), and Blautia (p-value = 9.22 × 10–18) in the SARS-CoV-2-infected group in comparison to the control group. Moreover, phylogenetic investigation of communities by reconstructing unobserved state (PICRUSt) functional prediction analysis of the 16S rRNA gene abundance data showed substantial differences in the enrichment of metabolic pathways such as lipid, amino acid, carbohydrate, and xenobiotic metabolism, in comparison between both groups. We discovered an enrichment of linoleic acid, ether lipid, glycerolipid, and glycerophospholipid metabolism in the SARS-CoV-2-infected group, suggesting a link to SARS-CoV-2 entry and replication in host cells. We estimate the major contributing genera to the four pathways to be Parabacteroides, Streptococcus, Dorea, and Blautia, respectively. The identified differences provide a new insight to enrich our understanding of SARS-CoV-2-related changes in gut microbiota, their metabolic capabilities, and potential screening biomarkers linked to COVID-19 disease severity