Evaluation of Different Retention Systems on a Distal Extension Removable Partial Denture Associated With an Osseointegrated Implant

The aim of this study was to evaluate the biomechanical behavior of a mandibular distal extension removable partial denture (DERPD) associated with an implant and different retention system, by bidimensional finite element method. Five hemimandible models with a canine and external hexagon implant at second molar region associated with DERPD were simulated: model A, hemimandible with a canine and a DERPD; model B, hemimandible with a canine and implant with a healing abutment associated to a DERPD; model C, hemimandible with a canine and implant with an ERA attachment associated to a DERPD; model D, hemimandible with a canine and implant with an O'ring attachment associated to a DERPD; and model E, hemimandible with a canine and implant-supported prosthesis associated to a DERPD. Cusp tips were loaded with 50 N of axial or oblique force (45 degrees). Finite element analysis was performed in ANSYS 9.0. model E showed the higher displacement and overload in the supporting tissues; the patterns of stress distribution around the dental apex of models B, C, and D were similar. The association between a DERPD and an osseointegrated implant using the ERA or O'ring systems shows lower stress values. Oblique forces showed higher stress values and displacement. Oblique forces increased the displacement and stress levels in all models; model C displayed the best stress distribution in the supporting structures; healing abutment, ERA, and O'ring systems were viable with RPD, but DERPD association with a single implant-supported prosthesis was nonviable.

Influence of Implant Design on the Biomechanical Environment of Immediately Placed Implants: Computed Tomography-Based Nonlinear Three-Dimensional Finite Element Analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biomechanical Evaluation of Platform Switching in Different Implant Protocols: Computed Tomography-Based Three-Dimensional Finite Element Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Brain serotonin blockade and paradoxical salt intake in rats

Serotonin antagonism in the lateral parabrachial nucleus (LPBN) enhances sodium appetite induced by hypovolaemia and angiotensin-mineralocorticoid activation, but produces no sodium intake in euhydrated animals. In the present work, male adult rats (n=21) that received bilateral injections of the serotonergic antagonist methysergide (4 mug/ 0.2 mul) into the LPBN combined to intragastric load of 2 M NaCl (2 ml/rat), ingested hypertonic NaCl (ingestion of 4.3+/-1.6 ml/2 h of 0.3 M NaCl versus vehicle into LPBN: 0.2+/-0.2 ml/2 h, P<0.05). Methysergide- and vehicle-treated animals also ingested water (9.5+/-0.7 and 7.2+/-0.5 ml/2 h, respectively, P>0.05) as expected from the state of cell dehydration produced by the load. Ingestion of water (11.0+/-1.2 ml/2 h), and of 0.3 M NaCl (1.1+/-0.7 ml/2 h) were not altered by methysergide in NaCl loaded rats with misplaced LPBN injections (n=15). The ingestion of hypertonic NaCl by rats with serotonergic blockade in the LPBN suggests that the circuits subserving sodium appetite are activated, but at the same time strongly inhibited through the LPBN, during cell dehydration. (C) 2003 IBRO. Published by Elsevier Ltd. All rights reserved.

Participation of alpha-1 and alpha-2 adrenoceptors of the lateral hypothalamic area in water intake, and renal sodium, potassium and urinary Volume excretion induced by central administration of angiotensin II

The circumventricular structures and the lateral hypothalamus (LH) have been shown to be important for the central action of angiotensin II (ANGII) on water and electrolyte regulation. Several anatomical findings have demonstrated neural connection between circumventricular structures and the LH, the present experiments were conducted to investigate the role of the alpha-adrenergic antagonists and agonistic injected into the LH on the water intake, sodium and potassium excretion elicited by injections of ANGII into the lateral ventricle (LV), the water intake was measured every 30 min over a period of 120 min. The sodium, potassium and urinary volume were measured over a period of 120 min in water-loaded rats. The injection of ANGII into the LV increased the water intake, which was reduced by previous injection of clonidine (an alpha-2-adrenergic agonist) into the LH. The injection of yohimbine (an alpha-2-adrenergic antagonist) and prazosin (an alpha-l-adrenergic antagonist) into the LH, which was done before injecting ANGII into the LV, also reduced the water intake induced by ANGII. The injection of ANGII into the LV reduced the sodium, potassium and urinary volume. Previous treatment with clonidine attenuated the action of ANGII in reducing the sodium, potassium and urinary volume, whereas previous treatment with yohimbine attenuated the effects of ANGII but with less intensity than that caused by clonidine. Previous treatment with prazosin increased the inhibitory effects of ANGII in those parameters. The injection of yohimbine and prazosin, which was done before the injection of clonidine, attenuated the effect of clonidine on the ANGII mechanism. The results of this study led us to postulate that when alpha-2-adrenergic receptors are blocked, the clonidine may act on the imidazoline receptors to produce its effects on the ANGII mechanism. We may also conclude that the LH is involved with circumventricular structures, which present excitatory and inhibitory mechanisms. Such mechanisms are responsible for regulating the renal excretion of sodium, potassium and water, (C) 2000 Elsevier B.V.

Influence of thermal and mechanical stresses on the strength of intact and relined denture bases

Statement of problem. Denture bases may become increasingly weaker as a result of thermal stress and flexural cyclic loading. Information regarding this potential problem and its relationship to the denture base reline is limited.Purpose. This study evaluated the influence of thermal and mechanical stresses on the strength of intact and relined denture bases.Material and methods. Twenty-eight microwave-polymerized (Acron MC) intact denture bases were prepared in the shape of a 3-mm-thick maxillary denture. Additionally, fifty-six 2-mm-thick denture bases were relined with 1 mm of autopolymerizing resin (Tokuyama Rebase Fast II or New Truliner) (n = 28). Intact and relined specimens were divided into 4 groups (n = 7) as follows: without stress (control); a mechanical stress at 0.8 Hz for 10,000 cycles; 5000 thermal cycles between 5 degrees C and 55 degrees C; or a combination thermo-mechanical stress. The specimens were vertically loaded in compression with a rounded rod at 5 mm/min until failure, using a universal testing machine. Data on maximum fracture load (N), deflection at fracture (%), and fracture energy (N-mm) were analyzed by 2-way analysis of variance and Student-Newman-Keuls tests (alpha = .05).Results. The strength of the denture bases relined with New Truliner was not significantly affected by any of the experimental conditions, but comparing the control groups, New Truliner exhibited the lowest maximum fracture load values. The maximum fracture load of intact denture bases (P = .002) and those relined with Tokuyama Rebase Fast II (P = .01) showed a significant decrease after thermal stress. Additionally, cyclic loading significantly decreased the maximum fracture load (P < .001), deflection at fracture (P = .025), and fracture energy (P < .001) of intact denture bases and those relined with Tokuyama Rebase (P values of .002, .039, and .001, respectively).Conclusion. Thermal and mechanical stresses exert deleterious effects on the strength of intact and/or relined denture bases, which vary according to the relining material used.

Effect of microwave disinfection on the flexural strength of hard chairside reline resins

Objectives: This study investigated the effect of microwave disinfection (650 W/6 min) on the flexural strength of five hard chairside reline resins (Kooliner, Duraliner II, Tokuso Rebase Fast, Ufi Get Hard, New Truliner) and one denture base resin (Lucitone 550).Methods: Thirty-two specimens (3.1x10x64 mm) from each acrylic resin were produced and divided into four groups of eight specimens each. The flexural test was performed after polymerization (G1), after two cycles of microwave disinfection (G2), after 7 days storage in water at 37 degrees C (G3) and after seven cycles of microwave disinfection (G4). Specimens from group G4 were microwaved daily being stored in water at 37 degrees C between exposures. The specimens were placed in three-point bend fixture in a MTS machine and loaded until failure. The flexural values (MPa) were submitted to ANOVA and Tukey's test (p=0.05).Results: Two cycles of microwave disinfection promoted a significant increase in flexural strength for materials Kooliner and Lucitone 550. After seven cycles of microwave disinfection, materials Kooliner and New Truliner showed a significant increase (p<0.05) in flexural values. The flexural strength of the material Tokuso Rebase was not significantly affected by microwave irradiation. Seven cycles of microwave disinfection resulted in a significant decrease in the flexural strength of material Duraliner II. Material Ufi Get Hard was the only resin detrimentally affected by microwave disinfection after two and seven cycles.Conclusions: Microwave disinfection did not adversely affect the flexural strength of all tested materials with the exception of material Ufi Get Hard. (c) 2005 Elsevier Ltd. All rights reserved.

Effect of disinfection by microwave irradiation on the strength of intact and relined denture bases and the water sorption and solubility of denture base and reline materials

This study evaluated the influence of microwave disinfection on the strength of intact and relined denture bases. Water sorption and solubility were also evaluated. A heat-polymerized acrylic resin (Lucitone 550) was used to construct 4-mm-thick (n = 40) and 2-mm-thick (n = 160) denture bases. Denture bases (2mm) were relined with an autopolymerizing resin (Tokuso Rebase Fast, Ufi Gel Hard, Kooliner, or New Truliner). Specimens were divided into four groups (n = 10): without treatment, one or seven cycles of microwave disinfection (650 W for 6 min), and water storage at 37 degrees C for 7 days. Specimens were vertically loaded (5 mm/min) until failure. Disc-shaped specimens (50 min x 0.5 mm) were fabricated (n = 10) to evaluate water sorption and solubility. Data on maximum fracture load (N), deflection (%), and solubility (%) were analyzed by two-way analysis of variance and Student-Newman-Keuls tests (alpha = 0.05). One cycle of microwave disinfection decreased the deflection at fracture and fracture energy of Tokuso Rebase Fast and New Truliner specimens. The strength of denture bases microwaved daily for 7 days was similar to the strength of those immersed in water for 7 days. Microwave disinfection increased the water sorption of all materials and affected the solubility of the reline materials. (C) 2007 Wiley Periodicals, Inc.

Mitochondrial alterations and apoptosis in smooth muscle from aged rats

We studied changes in mitochondrial morphology and function in the smooth muscle of rat colon. Under confocal microscopy, tissues loaded with potentiometric dye displayed rapid and spontaneous depolarization. Cyclosporin A (CsA), inhibitor of the permeability transition pore (PTP), caused an increase in mitochondrial membrane potential (DeltaPsi(m)) in tissues from adult young animals. In aged rats these changes were not observed. This suggests that physiological activation of PTP in aged rats is reduced. Electron microscopy showed alterations of the mitochondrial ultrastructure in tissues from aged rats involving a decreased definition of the cristae and fragmentation of the mitochondrial membranes. We also detected an increase in apoptotic cells in the smooth muscle from aged animals. Our results show that the aging process changes PTP activity, the ability to maintain DeltaPsi(m) and mitochondrial morphology. It is suggested that these can be associated with mitochondrial damage and cell death. (C) 2004 Elsevier B.V. All rights reserved.

Customized fiber glass posts. Fatigue and fracture resistance

Purpose: To evaluate the root fracture strength of human single-rooted premolars restored with customized fiberglass post-core systems after fatigue simulation. Methods: 40 human premolars had their crowns cut and the root length was standardized to 13 mm. The teeth were endodontically treated and embedded in acrylic resin. The specimens were distributed into four groups (n=10) according to the restorative material used: prefabricated fiber post (PFP), PFP+accessory fiber posts (PFPa), PFP+unidirectional fiberglass (PFPf), and unidirectional fiberglass customized post (CP). All posts were luted using resin cement and the cores were built up with a resin composite. The samples were stored for 24 hours at 37 degrees C and 100% relative humidity and then submitted to mechanical cycling. The specimens were then compressive-loaded in a universal testing machine at a crosshead speed of 0.5 mm/minute until fracture. The failure patterns were analyzed and classified. Data was submitted to one-way ANOVA and Tukey's test (alpha= 0.05). Results: The mean values of maximum load (N) were: PFP - 811.4 +/- 124.3; PFPa - 729.2 +/- 157.2; PFPf - 747.5 +/- 204.7; CP - 762.4 +/- 110. Statistical differences were not observed among the groups. All groups showed favorable restorable failures. Fiberglass customized post did not show improved fracture resistance or differences in failure patterns when compared to prefabricated glass fiber posts. (Am J Dent 2012;25:35-38).

Multiple effects of sibutramine on ejaculation and on vas deferens and seminal vesicle contractility

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chemotherapeutic agents in low noncytotoxic concentrations increase immunogenicity of human colon cancer cells

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modal analysis of anisotropic diffused-channel waveguide by a scalar finite element method

A procedure to model optical diffused-channel waveguides is presented in this work. The dielectric waveguides present anisotropic refractive indexes which are calculated from the proton concentration. The proton concentration inside the channel is calculated by the anisotropic 2D-linear diffusion equation and converted to the refractive indexes using mathematical relations obtained from experimental data, the arbitrary refractive index profile is modeled by a. nodal expansion in the base functions. The TE and TM-like propagation properties (effective index) and the electromagnetic fields for well-annealed proton-exchanged (APE) LiNbO3 waveguides are computed by the finite element method.

NONDEGENERATE UMBILICS, THE PATH FORMULATION and GRADIENT BIFURCATION PROBLEMS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of Airborne-Particle Abrasion and Mechanico-Thermal Cycling on the Flexural Strength of Glass Ceramic Fused to Gold or Cobalt-Chromium Alloy

Purpose: To evaluate the effect of airborne-particle abrasion and mechanico-thermal cycling on the flexural strength of a ceramic fused to cobalt-chromium alloy or gold alloy.Materials and Methods: Metallic bars (n = 120) were made (25 mm x 3 mm x 0.5 mm): 60 with gold alloy and 60 with Co-Cr. At the central area of the bars (8 mm x 3 mm), a layer of opaque ceramic and then two layers of glass ceramic (Vita VM13, Vita Zahnfabrick) were fired onto it (thickness: 1 mm). Ten specimens from each alloy group were randomly allocated to a surface treatment [(tungsten bur or air-particle abrasion (APA) with Al(2)O(3) at 10 mm or 20 mm away)] and mechanico-thermal cycling (no cycling or mechanically loaded 20,000 cycles; 10 N distilled water at 37 degrees C and then thermocycled 3000 cycles; 5 degrees C to 55 degrees C, dwell time 30 seconds) combination. Those specimens that did not undergo mechanico-thermal cyclingwere stored inwater (37 degrees C) for 24 hours. Bond strength was measured using a three-point bend test, according to ISO 9693. After the flexural strength test, failure types were noted. The data were analyzed using three factor-ANOVA and Tukey's test (alpha = 0.05).Results: There were no significant differences between the flexural bond strength of gold and Co-Cr groups (42.64 +/- 8.25 and 43.39 +/- 10.89 MPa, respectively). APA 10 and 20 mm away surface treatment (45.86 +/- 9.31 and 46.38 +/- 8.89 MPa, respectively) had similar mean flexural strength values, and both had significantly higher bond strength than tungsten bur treatment (36.81 +/- 7.60 MPa). Mechanico-thermal cycling decreased the mean flexural strength values significantly for all six alloy-surface treatment combinations tested when compared to the control groups. The failure type was adhesive in the metal/ceramic interface for specimens surface treated only with the tungsten bur, and mixed for specimens surface treated with APA 10 and 20 mm.Conclusions: Considering the levels adopted in this study, the alloy did not affect the bond strength; APA with Al(2)O(3) at 10 and 20 mm improved the flexural bond strength between ceramics and alloys used, and the mechanico-thermal cycling of metal-ceramic specimens resulted in a decrease of bond strength.