Probability of survival and stress distribution of narrow diameter implants with different implant-abutment taper angles.

This study evaluated the probability of survival, failure mode, and stress distribution of narrow diameter implants (NDIs) with internal implant-abutment conical connection comprised of different taper angles and thread designs. Sixty-three NDIs (Ø 3.5 × 8.5 mm) were divided according to the taper angle (TA), internal diameter (ID), and trapezoidal thread design (TD) (n = 21/group), as follows: (a) 11.5°U (11.5° TA; ID: 2.5 mm; TD: dual threaded); (b) 11.5°S (11.5° TA; ID: 2.5 mm; TD: single threaded); (c) 16°S (16° TA; ID: 2.72 mm; TD: single threaded). They were subjected to step-stress accelerated life testing. The reliability and use-level probability Weibull curves were calculated at 50, 100, and 150 N for a mission of 100,000 cycles and the failure mode was analyzed using a scanning electron microscope. For finite element analysis the von-Mises stress (σvM ) was calculated for the abutment and implant. All groups showed high reliability (above 84%) and failures occurred predominantly in the abutment. In the FEA, 11.5°U showed higher σvM for the implant. All NDIs showed high reliability at clinically challenging loads. The system with greater taper angle showed lower σVm in the implant, and dual threaded implants showed a higher stress concentration in the implant and cortical bone.

Zirconia-reinforced lithium silicate crowns: Effect of thickness on survival and failure mode.

OBJECTIVE: To evaluate the reliability and failure mode of zirconia-reinforced lithium silicate (ZLS) molar crowns of different thicknesses. METHODS: Monolithic ZLS molar crowns (0.5mm, 1.0mm, and 1.5 mm thickness) were modeled and milled using a CAD/CAM system (n = 21/group). Crowns were cemented on dentin-like epoxy resin replicas with a resin cement. The specimens were subjected to single load-to-failure test for step-stress profiles designing. Mouth-motion step-stress accelerated-life test was performed under water by sliding an indenter 0.7 mm lingually down on the distobuccal cusp until specimen fracture or suspension. Use level probability Weibull curves and reliability were calculated and plotted. Polarized-light optical microscope and scanning electron microscope (SEM) were used to characterize fracture patterns. RESULTS: Irrespective of crown thickness, beta (ß) values were higher than 1 and fatigue accelerated failures. While 0.5 mm ZLS crowns exhibited a significant reduction in the probability of survival at 200N, 300N and 400 N mission loads (69%, 41% and 19%, respectively), no significant difference was observed between 1.0 mm and 1.5 mm crowns. Both thicknesses have maintained the survivability at approximately 90%. Failure primarily comprised bulk fracture where radial cracks originated from the cementation surface beneath the indenter loading trail and propagated towards the cervical margin. SIGNIFICANCE: 1.5 mm- and 1.0 mm-thickness monolithic ZLS crowns presented higher probability of survival compared to 0.5 mm crowns. Bulk fracture was the chief failure mode, regardless of thickness.

Stress distribution of single-implant-retained overdenture reinforced with a framework: A finite element analysis study.

STATEMENT OF PROBLEM: Studies have demonstrated the effectiveness of a single-implant-retained mandibular overdenture for elderly patients with edentulism. However, due to the high concentration of stress around the housing portion of the single implant, this prosthesis tends to fracture at the anterior region more than the 2-implant-retained mandibular overdenture. PURPOSE: The purpose of this finite-element analysis study was to evaluate the stress distribution in a single-implant-retained mandibular overdenture reinforced with a cobalt-chromium framework, to minimize the incidence of denture base fracture. MATERIAL AND METHODS: Two 3-dimensional finite element models of mandibular overdentures supported by a single implant with a stud attachment were designed in SolidWorks 2013 software. The only difference between the models was the presence or absence of a cobalt-chromium framework at the denture base between canines. Subsequently, the models were imported into the mathematical analysis software ANSYS Workbench v15.0. A mesh was generated with an element size of 0.7 mm and submitted to convergence analysis before mechanical simulation. All materials were considered to be homogeneous, isotropic, and linearly elastic. A 100-N load was applied to the incisal edge of the central mandibular incisors at a 30-degree angle. Maximum principal stress was calculated for the overdenture, von Mises stress was calculated for the attachment and implant, and minimum principal stress was calculated for cortical and cancellous bone. RESULTS: In both models, peak stress on the overdenture was localized at the anterior intaglio surface region around the implant. However, the presence of the framework reduced the stress by almost 62% compared with the overdenture without a framework (8.7 MPa and 22.8 MPa, respectively). Both models exhibited similar stress values in the attachment, implant, and bone. CONCLUSIONS: A metal framework reinforcement for a single-implant-retained mandibular overdenture concentrates less stress through the anterior area of the prosthesis and could minimize the incidence of fracture.

Follow-up of rheumatic carditis treated with steroids.

OBJECTIVE: To present the long-term follow-up of children hospitalised for severe rheumatic carditis who were treated with corticosteroids. METHODS: This is a retrospective analysis of the outcome of 242 patients with severe rheumatic carditis after discharge from two public hospitals in Niteroi, Brazil. We followed up 118 patients for 4 years or more, with an average of 7.7 years. They were treated with antibiotics to accomplish bacterial eradication and either intravenous methylprednisolone - 40 cases - or oral prednisone - 78 patients - to treat carditis. They were followed up in outpatient clinic. RESULTS: Cardiac failure was categorised as classes III and IV according to the New York Heart Association classification. In the intravenous corticosteroid group, 21 cases (52.5%) had isolated mitral valve regurgitation, 12 (30%) had mitral plus aortic involvement, and seven (17.5%) had aortic lesion only. In the oral prednisone group, 45 (58%) had mitral valve regurgitation only, 27 (34%) had mitral plus aortic involvement, and six (8%) had aortic lesion only. A total of 28 children were in their first disease attack, of whom 19 (68%) had a rupture of chordae tendineae. A total of 58 patients (49%) sustained recurrence of carditis because of neglected secondary prophylaxis. In all, 19 cases (16%) underwent cardiac surgery - valve replacement or valvuloplasty. In 33% of the cases, the outcome was favourable - asymptomatic at follow-up. The overall mortality rate was 6.8%. CONCLUSION: Many critically ill patients who complied with secondary prophylaxis were left with minor injuries, whereas those who neglected it or abandoned it had serious sequelae. The rate of abandonment and loss to follow-up was very high. Many cases (49%) were re-hospitalised because of carditis recurrence.

Contribuição ao estudo farmacobotânico da Echinodorus macrophyllus (Kunth) Micheli (chapéu-de-couro) - Alismataceae / Contribution to the pharmacobotanical study of Echinodorus macrophyllus (Kunth) Micheli (chapéu-de-couro) - Alismataceae

A Echinodorus macrophyllus (Kunth) Micheli - Alismataceae, conhecida como chapéu-de-couro, chá-mineiro, erva-de-pantâno, erva-de-bugre, congonha-do-brejo e erva-do-brejo, ocorre em Minas Gerais e São Paulo. Embora tenha importância terapêutica, comercial e estar inscrita nas duas primeiras edições da Farmacopéia Brasileira (1924, 1959), são poucos os estudos que a contemplam. Este presente trabalho teve como objetivo estudar a morfoanatomia foliar e do pecíolo da E. macrophyllus, a fim de ampliar o seu conhecimento farmacognóstico, visando o controle de qualidade. A descrição macroscópica foi realizada à vista desarmada, com recursos óticos e as dimensões, com paquímetro. As características anatômicas foram determinadas, após a colheita, nos fragmentos de folhas e pecíolos fixos, seccionados à mão livre e fixados em glicerina, azul-de-astra ou fucsina. O estudo morfo-anatômico da folha e do pecíolo da E. macrophyllus contribuiu para ampliar e aprofundar as informações contidas nas Farmacopéias Brasileiras (1924, 1959). As características estruturais assinaladas auxiliam na identificação da espécie e fornece parâmetros que poderão ser aplicados futuramente no controle de qualidade farmacognóstico. E, inseriu no contexto da descrição anatômica, a presença de pêlos tectores e de células diafragmáticas, estruturas chaves no diagnóstico da espécie, não descritas pelas Farmacopéias Brasileiras (1929, 1959).

Echinodorus macrophyllus (Kunth) Micheli - Alismataceae, known as "chapéu-de-couro", "chá-mineiro", "erva-de-pântano", "erva-de-bugre", "congonha-do-brejo", "erva-do-brejo", occurs in Minas Gerais and São Paulo. Although it has therapeutic and commercial importance and is described in the two first editions of the Brazilian Pharmacopoeia (1924, 1959), there are few studies that contemplate it. This present work had the objective to study the leaf and petiole morpho-anatomy of A. macrophyllus, in order to extend its pharmacognosy knowledge, aiming at the quality control. The macroscopic description was carried through disarmed sight, with optical resources and the dimensions with a caliper. The anatomical c haracteristics had been determined, after the harvest, in the fragments of leaves and fixed petioles, freehand sectioned and stained either in glycerin, astra-blue or fuchsine. The morpho-anatomical study of the leaf and petiole of A. macrophyllust contributed to extend and deepen the information contained in the Brazilian Pharmacopoeia (1924, 1959). The designated structural characteristics assist in the identification of the species and supply parameters that could be applied in the pharmacognosy quality control in the future. And, the presence of non-glandular trichomes in the midribs (adaxial and abaxial surface) and the petiole exhibits diaphragm (specialized cells), key structures in the diagnosis of the species, that are not described in the Brazilian Pharmacopoeia (1924, 1959), were inserted in the context of the anatomical description.