T-Bar clasp-retained removable partial denture as an alternative to implant-based prosthetic treatment

This article reports the case of a 55-year-old female patient who presented with unsatisfactory temporary crowns in the right mandibular premolars and molars, and a premolar-to-molar fixed partial denture in the left side. The clinical and radiographic examinations revealed a fracture of the left first premolar that was a retainer of the fixed partial denture and required extraction. Initially, the acrylic resin crowns were replaced by new ones, and a provisional RPD was made using acrylic resin and orthodontic wire clasps to resolve the problem arising from the loss of the fixed partial denture. Considering the patient's high esthetic demands, the treatment options for the definitive prosthetic treatment were discussed with her and rehabilitation with implant-supported dentures was proposed because the clinical conditions of the residual alveolar ridge were suitable for implant installation, and the patient's general health was excellent. However, the patient did not agree because she knew of a failed case of implant-retained denture in a diabetic individual and was concerned. The patient was fully informed that implant installation was the best indication for her case, but the arguments were not sufficient to change her decision. The treatment possibilities were presented and the patient opted for a clasp-retained removable partial denture (RPD) associated with the placement of crowns in the pillar teeth. The temporary RPD was replaced by the definitive RPD constructed subsequently. Although RPD was not the first choice, satisfactory esthetic and functional outcomes were achieved, overcaming the patient's expectations. This case report illustrates that the dentist must be prepared to deal with situations where, for reasons that cannot be managed, the patient does not accept the treatment considered as the most indicated for his/her case. Alternatives must be proposed and the functional and esthetic requirements must be fulfilled in the best possible manner.Este artigo relata o caso de uma paciente de 55 anos que apresentava no arco mandibular coroas provisórias insatisfatórias nos pré-molares do lado direito e uma prótese parcial fixa de molar a pré-molar no lado esquerdo. Os exames clínico e radiográfico revelaram uma fratura do primeiro pré-molar esquerdo que era um retentor da prótese parcial fixa e teve a extração indicada. Inicialmente, as coroas provisórias foram substituídas por novas e uma prótese parcial removível provisória foi confeccionada com resina acrílica e grampos de fio ortodôntico a fim resolver os problemas relacionados à perda da prótese parcial fixa. Considerando a forte demanda estética da paciente, foram discutidas as opções de tratamento protético definitivo. Foi proposta a reabilitação com prótese implanto-suportada uma vez que as condições clínicas do rebordo alveolar se apresentavam adequadas para instalação de implantes e a saúde geral da paciente era excelente. Entretanto, a paciente não concordou com o tratamento proposto, alegando saber de um caso clínico em que houve insucesso na reabilitação por prótese implanto-suportada em um paciente diabético. Ela foi inteiramente informada de que a colocação de implantes era a melhor indicação para seu caso, mas os argumentos não foram suficientes para mudar sua decisão. As possibilidades de tratamento foram apresentadas e a paciente optou por uma prótese parcial removível (PPR) retida a grampos associada com coroas nos dentes pilares. Na seqüência, a PPR provisória foi substituída por uma PPR definitiva. Embora a PPR não tivesse sido a primeira escolha, foram obtidos resultados estéticos e funcionais satisfatórios, superando as expectativas da paciente. Este relato de caso ilustra que o dentista deve estar preparado para enfrentar situações em que, por razões que não possam ser administradas, o paciente não aceite o tratamento considerado mais indicado para seu caso. Alternativas devem ser propostas e as exigências estéticas e funcionais devem ser contempladas da melhor maneira possível

A survey of recent results for the generalizations of ordinary differential equations

This is a review paper on recent results for different types of generalized ordinary differential equations. Its scope ranges from discontinuous equations to equations on time scales. We also discuss their relation with inclusion and highlight the use of generalized integration to unify many of them under one single formulation

Proton-Coupled Electron-Transfer Mechanism for the Radical Scavenging Activity of Cardiovascular Drug Dipyridamole

Dipyridamole (DIP) is a well-known pharmaceutical drug used as a coronary vasodilator and anti-platelet agent in clinics for treating several cardiovascular diseases. Primarily, the therapeutic effects of the drug are attributed to its antioxidant potency. In this research, we aim to declare the unknown antioxidant mechanism of DIP as well as its potent chain-breaking antioxidant activity in polar aqueous medium inside the cells, using different experimental methods and theoretical quantum calculations. Data demonstrated the higher antioxidant capacity of DIP against ROS and free radicals in polar cell's interior. DIP is capable of generating long living and noninvasive DIP• radicals in oxidant condition that leads to an effective “chain-breaking antioxidant” activity. Quantum computational data indicated that DIP antioxidant has more favorable ionization potential than trolox which means DIP has higher antioxidant activity. Also, data showed that the direct hydrogen-transfer is not a favorable process to construct DIP• because of high barrier energy, though electron-transfer process can more easily to produce DIP•+ with the lowest barrier energy. Altogether, the electron donating potency of DIP to reduce ferric ion, having the low anodic oxidation peak potential, producing long lived stable DIP• radicals and protecting myoblast cells from oxidation, proposed the excellent “chain-breaking antioxidant” potency via electron-transfer mechanism of this vasodilator DIP drug in polar aqueous medium

Quantifying Water-Mediated Protein–Ligand Interactions in a Glutamate Receptor: A DFT Study

It is becoming increasingly clear that careful treatment of water molecules in ligand–protein interactions is required in many cases if the correct binding pose is to be identified in molecular docking. Water can form complex bridging networks and can play a critical role in dictating the binding mode of ligands. A particularly striking example of this can be found in the ionotropic glutamate receptors. Despite possessing similar chemical moieties, crystal structures of glutamate and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) in complex with the ligand-binding core of the GluA2 ionotropic glutamate receptor revealed, contrary to all expectation, two distinct modes of binding. The difference appears to be related to the position of water molecules within the binding pocket. However, it is unclear exactly what governs the preference for water molecules to occupy a particular site in any one binding mode. In this work we use density functional theory (DFT) calculations to investigate the interaction energies and polarization effects of the various components of the binding pocket. Our results show (i) the energetics of a key water molecule are more favorable for the site found in the glutamate-bound mode compared to the alternative site observed in the AMPA-bound mode, (ii) polarization effects are important for glutamate but less so for AMPA, (iii) ligand–system interaction energies alone can predict the correct binding mode for glutamate, but for AMPA alternative modes of binding have similar interaction energies, and (iv) the internal energy is a significant factor for AMPA but not for glutamate. We discuss the results within the broader context of rational drug-design

ENDOR Spectroscopy and DFT Calculations: Evidence for the Hydrogen-Bond Network Within α2 in the PCET of E. coli Ribonucleotide Reductase

Escherichia coli class I ribonucleotide reductase (RNR) catalyzes the conversion of nucleotides to deoxynucleotides and is composed of two subunits: α2 and β2. β2 contains a stable di-iron tyrosyl radical (Y[subscript 122]•) cofactor required to generate a thiyl radical (C[subscript 439]•) in α2 over a distance of 35 Å, which in turn initiates the chemistry of the reduction process. The radical transfer process is proposed to occur by proton-coupled electron transfer (PCET) via a specific pathway: Y[subscript 122] ⇆ W[subscript 48][?] ⇆ Y[subscript 356] in β2, across the subunit interface to Y[subscript 731] ⇆ Y[subscript 730] ⇆ C[subscript 439] in α2. Within α2 a colinear PCET model has been proposed. To obtain evidence for this model, 3-amino tyrosine (NH2Y) replaced Y[subscript 730] in α2, and this mutant was incubated with β2, cytidine 5′-diphosphate, and adenosine 5′-triphosphate to generate a NH2Y730• in D2O. [[superscript 2]H]-Electron–nuclear double resonance (ENDOR) spectra at 94 GHz of this intermediate were obtained, and together with DFT models of α2 and quantum chemical calculations allowed assignment of the prominent ENDOR features to two hydrogen bonds likely associated with C[subscript 439] and Y[subscript 731]. A third proton was assigned to a water molecule in close proximity (2.2 Å O–H···O distance) to residue 730. The calculations also suggest that the unusual g-values measured for NH[subscript 2]Y[subscript 730]• are consistent with the combined effect of the hydrogen bonds to Cys[subscript 439] and Tyr[subscript 731], both nearly perpendicular to the ring plane of NH[subscript 2]Y[subscript 730]. The results provide the first experimental evidence for the hydrogen-bond network between the pathway residues in α2 of the active RNR complex, for which no structural data are available.National Institutes of Health (U.S.) (NIH GM29595

LOCALLY DENSE BASIS SETS FOR ACCURATE THERMOCHEMISTRY

1. D.B. Chesnut and K.D. Moore, J. Comput. Chem, 10, 648, 1989.Author Institution: Department of Chemistry, Carleton UniversityThe use of locally dense basis sets (LDBS) has gained wide acceptance in the field of NMR shielding calculations. This methods allows for the accurate determination of properties, for centers of interest in larger molecules, by treating them with a large basis set while a smaller basis set is used for the rest of the molecule. The required CPU time is greatly reduced by using LDBS while very little accuracy is lost [1]. We have recently examined the use of locally dense basis sets. in conjunction with the B3LYP method, for the determination of bond dissociation energies (BDE) and electron affinities (EA) of large molecules (for example, $\alpha$-tocopherol with 81 atoms). Our method involves assigning basis sets of various sizes to regions of a molecule based on chemical understanding of the various structural features of the subject species. Our current results indicate that BDEs and EAs determined by our approach $(LDBS + B3LYP)$ are remarkably insensitive to these assignments. We will present the results of test calculation which illustrate the utility of our method and discuss some of the implications of our findings