RESUMEN
INTRODUCTION: This study evaluated the effect of traditional and conservative endodontic access cavity designs in combination with WaveOne Gold and TruNatomy instrumentation systems on the fracture resistance of mandibular first molars by means of nonlinear finite element analysis (FEA). METHODS: Micro-CT images of 4 human mandibular first molars were used to generate representative FEA models. The mandibular first molars samples were scanned before and after endodontic access cavity preparation and instrumentation of all 3 canals. Five nonlinear static loads were applied vertically and horizontally to specific contact points on the occlusal surface of the teeth. Maximum von Mises stress before failure and distribution of von Mises strains were recorded and compared between groups. RESULTS: Molars with conservative endodontic access cavities required similar levels of loads to reach failure compared with their control samples, whereas molars with traditional endodontic access cavities required significantly reduced loads in order to fail. According to the numerical investigation, the type of instrumentation system was found to have an insignificant effect on the fracture resistance of the teeth under study. Von Mises stress was concentrated around the cervical region and in the larger distal roots for all numerical models. CONCLUSIONS: The fracture resistance of mandibular first molars is influenced significantly by a reduction in dental hard tissue, which was found to control the level of the ultimate failure load for each tooth.
Asunto(s)
Caries Dental , Diente no Vital , Diente , Humanos , Análisis de Elementos Finitos , Diente Molar , Cavidad Pulpar/diagnóstico por imagen , Preparación del Conducto RadicularRESUMEN
INTRODUCTION: The purpose of this study was to evaluate and compare 2 different access cavity designs in combination with 2 popular single-file preparation systems to see which combination preserves dentin, more specifically pericervical dentin, best. The minimum remaining dentin thickness and dentin volumes were evaluated pre- and postinstrumentation. METHODS: Sixty extracted human mandibular molars were selected and randomly divided into 2 different access cavity design preparation groups: traditional access cavities (n = 30) and conservative access cavities (n = 30). Within each cavity preparation design group, the 30 teeth were divided into 2 instrumentation groups (WaveOne Gold Primary; Dentsply Sirona, Ballaigues, Switzerland [n = 15] and TruNatomy Prime, Dentsply Sirona [n = 15]). Samples were scanned using micro-computed tomographic imaging before and after access cavity preparation as well as after final endodontic instrumentation. The pericervical remaining dentin thickness and dentin volume changes were evaluated and compared. RESULTS: Conservative access cavity designs resulted in more favorable remaining dentin thickness. The least amount of mean dentin volume loss was also recorded in the conservative access cavity preparation groups regardless of the preparation instrumentation. CONCLUSIONS: In terms of the remaining pericervical dentin thickness and dentin volume reductions, the authors conclude that conservative access cavity designs preserve dentin best.
Asunto(s)
Cavidad Pulpar , Preparación del Conducto Radicular , Humanos , Cavidad Pulpar/diagnóstico por imagen , Oro , Dentina/diagnóstico por imagenRESUMEN
INTRODUCTION: The aim was to compare the glide path and final preparation times of WaveOne Gold and TruNatomy in conjunction with two different endodontic access cavity designs in extracted human molar teeth. METHODS: 60 extracted human mandibular molars with mesiobuccal canals were selected and randomly divided into two different access cavity design preparation groups (n = 30). Traditional access cavities (TAC) and conservative access cavities (CAC). Within each cavity design group, the 30 teeth were divided in to two instrumentation groups (WaveOne Gold Primary (n = 15) and TruNatomy Prime (n = 15)). Group 1: TAC, #10 stainless steel manual K-file followed by WaveOne Gold Glider and WaveOne Gold Primary. Group 2: CAC, #10 stainless steel manual K-file followed by WaveOne Gold Glider and WaveOne Gold Primary. Group 3: TAC, #10 stainless steel manual K-file followed by TruNatomy Orifice Modifier and Glider and TruNatomy Prime. Group 4: CAC, #10 stainless steel manual K-file followed by TruNatomy Glider and TruNatomy Prime. Glide path and final preparation times were recorded. RESULTS: Shaping time with TruNatomy Glider in combination with TruNatomy Prime instruments were faster compared to the WaveOne Gold Glider/ WaveOne Gold Primary instruments regardless of the type of access cavity preparation. TAC design yielded faster preparation time (38.2 ± 4.57 seconds) compared to the CAC (55.6 ± 6.91 seconds) in the WaveOne Gold Glider/ WaveOne Gold Primary instrumentation group. No difference was found between the different access cavity design groups in combination with TruNatomy Glider/TruNatomy Prime preparation. CONCLUSION: Preparation time with TruNatomy Glider and Prime instruments was significantly faster than WaveOne Gold Glider/WaveOne Gold Primary, regardless of the access cavity design. TAC design in combination with WaveOne Gold Glider/ WaveOne Gold Primary instrumentation resulted in faster preparation time compared to WaveOne Gold Glider/WaveOne Gold in combination with the CAC design.
Asunto(s)
Cavidad Pulpar , Preparación del Conducto Radicular , Diseño de Equipo , Oro , Humanos , Diente Molar , Rotación , Acero InoxidableRESUMEN
Plant immune receptors are often difficult to express heterologously, hindering study of direct interactions between these receptors and their targets with traditional biochemical approaches. The cell-free method ribosome display (RD) enables expression of such recalcitrant proteins by keeping each nascent polypeptide chain tethered to its ribosome, which can enhance protein folding by virtue of its size and solubility. Moreover, in contrast to an in planta readout of receptor activity such as a hypersensitive response that conflates binding and signaling, RD enables direct probing of the interaction between plant immune receptors and their targets. Here, we demonstrate the utility of this approach using tomato recognition of Trichoderma viride ethylene-inducing xylanase (EIX) as a case study. Leveraging the modular nature of the tomato LeEIX2 and LeEIX1 leucine-rich repeat (LRR) receptors, we applied an entropy-informed algorithm to maximize the information content in our receptor segmentation RD experiments to identify segments implicated in EIX binding. Unexpectedly, two distinct EIX-binding hotspots were discovered on LeEIX2 and both hotspots are shared with decoy LeEIX1, suggesting that their contrasting receptor functions are not due to differential modes of ligand binding. Given that most plant immune receptors are thought to engage targets via their LRR sequences, this approach should be of broad utility in rapidly identifying their binding hotspots.
Asunto(s)
Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Solanum lycopersicum/metabolismo , Sitios de Unión , Sistema Libre de Células/química , Sistema Libre de Células/metabolismo , Endo-1,4-beta Xilanasas/química , Endo-1,4-beta Xilanasas/genética , Endo-1,4-beta Xilanasas/metabolismo , Proteínas Fúngicas/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Hypocreales/enzimología , Hypocreales/genética , Solanum lycopersicum/química , Solanum lycopersicum/microbiología , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/inmunología , Enfermedades de las Plantas/microbiología , Proteínas de Plantas/genética , Unión Proteica , Pliegue de Proteína , Ribosomas/química , Ribosomas/genética , Ribosomas/metabolismoRESUMEN
Sea lamprey immunization can yield leucine-rich repeat (LRR) protein binders analogous to globular antibodies developed from mammals. A novel minimal LRR was discovered through lamprey immunization with human immunoglobulin G Fc domain (IgG Fc). Initial attempts to solubly express this LRR protein, VLRB.IgGFc, in Escherichia coli proved challenging, so it was analyzed using the cell-free method ribosome display. In ribosome display, VLRB.IgGFc was found to bind specifically to the Fc domain of IgG, with little observed cross-reactivity to IgA or IgM. The minimal repeat protein architecture of VLRB.IgGFc may facilitate modular LRR extensions to incorporate additional or augmented functionality within a continuous, structurally defined scaffold. We exploited this modularity to design a chimera of a well-characterized, soluble LRR repebody and the initially insoluble VLRB.IgGFc to produce soluble Repe-VLRB.IgGFc. The minimal IgG Fc-binding module, Repe-VLRB.IgGFc, and future-engineered variants thereof should be useful additions to the biotechnological toolbox for detecting, purifying, or targeting IgGs. More generally, this two-step approach of minimal LRR binder discovery via sea lamprey immunization followed by modular augmentation of functionality may be of general utility in protein engineering.
Asunto(s)
Petromyzon , Animales , Humanos , Inmunización , Inmunoglobulina G , Leucina , MamíferosRESUMEN
Although cell-free directed evolution methods have been used to engineer proteins for nearly two decades, selections on more complex phenotypes have largely remained in the domain of cell-based engineering approaches. Here, we review recent conceptual advances that now enable in vitro display of multimeric proteins, integral membrane proteins, and proteins with an expanded amino acid repertoire. Additionally, we discuss methodological improvements that have enhanced the accessibility, efficiency, and robustness of cell-free approaches. Coupling these advances with the in vitro advantages of creating exceptionally large libraries and precisely controlling all experimental conditions, cell-free directed evolution is poised to contribute significantly to our understanding and engineering of more complex protein phenotypes.