A finite element study on stress distribution of two different attachment designs under implant supported overdenture

Objective

This study aimed to evaluate stress patterns generated within implant-supported mandibular overdentures retained by two different attachment types: ball and socket and locator attachments.

Materials and methods

Commercial CAD/CAM and finite element analysis software packages were utilized to construct two 3D finite element models for the two attachment types. Unilateral masticatory compressive loads of 50, 100, and 150 N were applied vertically to the overdentures, parallel to the longitudinal axes of the implants. Loads were directed toward the central fossa in the molar region of each overdenture, that linear static analysis was carried out to find the generated stresses and deformation on each part of the studied model.

Results

According to FEA results the ball attachment neck is highly stressed in comparison to the locator one. On the other hand mucosa and cortical bone received less stresses under ball and socket attachment.

Conclusions

Locator and ball and socket attachments induce equivalent stresses on bone surrounding implants. Locator attachment performance was superior to that of the ball and socket attachment in the implants, nylon caps, and overdenture. Locator attachments are highly recommended and can increase the interval between successive maintenance sessions.     

Deciphering the canonical blockade of activated Hageman factor (FXIIa) by benzamidine in the coagulation cascade: A thorough dynamical perspective

The experimental inhibitory potency of benzamidine (BEN) paved way for further design and development of inhibitors that target β‐FXIIa. Structural dynamics of the loops and catalytic residues that encompass the binding pocket of β‐FXIIa and all serine proteases are crucial to their overall activity. Employing molecular dynamics and post‐MD analysis, this study sorts to unravel the structural and molecular events that accompany the inhibitory activity of BEN on human β‐FXIIa upon selective non‐covalent binding. Analysis of conformational dynamics of crucial loops revealed prominent alterations of the original conformational posture of FXIIa, evidenced by increased flexibility, decreased compactness, and an increased exposure to solvent upon binding of BEN, which could have in turn interfered with the essential roles of these loops in enhancing their procoagulation interactions with biological substrates and cofactors, altogether resulting in the consequential inactivation of FXIIa. A sustained interaction of the catalytic triad residues and key residues of the autolysis loop impeded their roles in catalysis which equally enhanced the inhibitory potency of BEN toward β‐FXIIa evidenced by a favorable binding. Findings provide essential structural and molecular insights that could facilitate the structure‐based design of novel antithrombotic compounds with enhanced inhibitory activities and low therapeutic risk.     

Improved Strength and Toughness of Carbon Woven Fabric Composites with Functionalized MWCNTs

This investigation examines the role of carboxyl functionalized multi-walled carbon nanotubes (COOH-MWCNTs) in the on- and off-axis flexure and the shear responses of thin carbon woven fabric composite plates. The chemically functionalized COOH-MWCNTs were used to fabricate epoxy nanocomposites and, subsequently, carbon woven fabric plates to be tested on flexure and shear. In addition to the neat epoxy, three loadings of COOH-MWCNTs were examined: 0.5 wt%, 1.0 wt% and 1.5 wt% of epoxy. While no significant statistical difference in the flexure response of the on-axis specimens was observed, significant increases in the flexure strength, modulus and toughness of the off-axis specimens were observed. The average increase in flexure strength and flexure modulus with the addition of 1.5 wt% COOH-MWCNTs improved by 28% and 19%, respectively. Finite element modeling is used to demonstrate fiber domination in on-axis flexure behavior and matrix domination in off-axis flexure behavior. Furthermore, the 1.5 wt% COOH-MWCNTs increased the toughness of carbon woven composites tested on shear by 33%. Microstructural investigation using Fourier Transform Infrared Spectroscopy (FTIR) proves the existence of chemical bonds between the COOH-MWCNTs and the epoxy matrix.     

Association of PTPN22 gene polymorphism and systemic lupus erythematosus in a cohort of Egyptian patients: impact on clinical and laboratory results

To assess the possible association between the protein tyrosine phosphatases non-receptor 22 (PTPN22) gene 1858 CT polymorphism and the predisposition to systemic lupus erythematosus (SLE) in Egyptian patients and its influence on clinical and laboratory parameters. PTPN22 gene 1858 CT polymorphisms were analyzed in forty SLE patients and 20 normal controls by real-time polymerase chain reaction (PCR) technology, using the TaqMan 5-allele discrimination assay. Detailed history, clinical examination, and investigations were done to detect various organ involvement. The homozygous genotype TT was absent in both SLE and controls. The CC genotype was observed in 47.5% SLE and 80% controls; the CT genotype was found in 52.5% patients and 20% controls. The frequencies of the C and T alleles were 74 and 26% in SLE and 90 and 10% in controls, respectively. The presence of CT genotype increased the risk for developing SLE by 4.42. Renal involvement was significantly higher in SLE patients with CT (76.2%) compared to those with CC genotype (42.1%).