Effect of the photoinitiator system on the polymerization of secondary methacrylamides of systematically varied structure for dental adhesive applications.

OBJECTIVE: The aim of this study was to investigate the influence of the photoinitiator system on the polymerization kinetics of methacrylamide-based monomers as alternatives to methacrylates in adhesives dental-based materials. METHODS: In total, 16 groups were tested. Monofunctional monomers (2-hydroxyethyl methacrylate) - HEMA; (2-hydroxy-1-ethyl methacrylate) -2EMATE, (2-hydroxyethyl methacrylamide) - HEMAM; and (N-(1-hydroxybutan-2-yl) methacrylamide) -2EM; were combined with bifunctional monomers containing the same polymerizing moieties as the monofunctional counterparts (HEMA-BDI; 2EMATE-BDI; HEMAM-BDI; and 2EM-BDI) at 50/50 M ratios. BHT was used as inhibitor (0.1 wt%) and the photoinitiators used were: CQ + EDMAB (0.2/0.8), BAPO (0.2), IVOCERIN (0.2), and DMPA (0.2), in wt%. The polymerization kinetics were monitored using Near-IR spectroscopy (∼6165 cm-1) in real-time while the specimens were photoactivated with a mercury arc lamp (Acticure 2; 320-500 nm, 300 mW/cm2) for 5 min, and maximum rate of polymerization (Rpmax, in %.s-̄1), degree of conversion at Rpmax (DC@Rpmax, in %), and the final degree of conversion (Final DC, in %) were calculated (n = 3). Initial viscosity was measured with an oscillating rheometer (n = 3). Data were analyzed using Two-way ANOVA for the polymerization kinetics and one-way ANOVA for the viscosity. Multiple comparisons were made using the Tukey's test (∝ = 0.05). RESULTS: There was statistically significant interaction between monomer and photoinitiator (p < 0.001). For the methacrylates groups, the highest Rpmax was observed for HEMA + DMPA and 2EMATE + BAPO. For methacrylamides groups, the highest Rpmax were observed for HEMAM and 2EM, both with DMPA. Final DC was higher for the methacrylate groups, in comparison with methacrylamide groups, independent of the photoinitiators. However, for the methacrylamide groups, the association with BAPO led to the lowest values of DC. In terms of DC@Rpmax, methacrylate-based systems showed significantly higher values than methacrylamide formulations. DMPA and Ivocerin led to higher values than CQ/EDMAB and BAPO in methacrylamide-based compounds. BAPO systems showed de lowest values for both HEMA and HEMAM formulations. For the viscosity (Pa.s), only 2EM had higher values (1.60 ± 0.15) in comparison with all monomers. In conclusion, polymerization kinetics was affected by the photoinitiators for both monomers. Viscosity was significantly increased with the use of secondary methacrylamide. SIGNIFICANCE: this work demonstrated the feasibility of using newly-synthesized methacrylamide monomers in conjunction with a series of initiator systems already used in commercial materials.

Effect of the addition of thiourethane oligomers on the solâ¿¿gel composition of BisGMA/TEGDMA polymer networks.

OBJECTIVES: Thiourethane oligomers have been shown to increase the fracture toughness and reduce the polymerization stress of methacrylate-based materials. However, network formation has not been elucidated in these materials yet. The aim of this study was to evaluate how the addition of a thiourethane oligomer (TU) influences the sol/gel composition and network structure of methacrylate-based materials using dynamic mechanical analysis and extraction methods. MATERIALS AND METHODS: BisGMA/TEGDMA at systematically varied mass ratios (20/80 to 80/20wt%) were mixed with pre-polymerized thiourethane oligomers at 0 (control) or 20wt%, synthesized by combining pentaerythritol tetra-3-mercaptopropionate with dicyclohexylmethane 4,4⿲-Diisocyanate, at 1:2 isocyanate:thiol. 0.1wt% of 2,2-Dimethoxy-2-phenylacetophenone was added as the photoinitiator and 0.3wt% of 2,6-di-tert-butyl-4-methylphenol was added as a free radical inhibitor. Disk specimens (0.8ÿ10mm in diameter, n=3) were photoactivated at 270mW/ (320â¿¿500nm) for 1min. The degree of conversion (DC) was measured in near-IR (Ë¿6165cmâ¿¿1). Specimens were immersed in two different solvents (water for 7 days or dicholoromethane for 48h). Water sorption (WS) and solubility (SL) were obtained according to ISO 4049. The leachates for both solutions were analyzed with 1H-NMR (400MHz, CDCL3). Bar specimens (1ÿ3ÿ25mm, photocured and then post-processed at 180°C for 8h to DC>95%) were subjected to dynamic mechanical analysis (â¿¿30 to 230°C) to obtain glass transition temperature (Tg), tan delta curves and crosslinking density (ν). Data was analyzed with two-way ANOVA/Tukeyâ¿¿s test (95%). RESULTS: In general, the presence of TU increased the overall conversion. The WS was similar for all groups, but the SL decreased by 2-fold with the addition of the TU oligomer for all compositions, except BisGMA/TEGDMA 80/20. The BisGMA concentration of the leachates increased with increasing BisGMA in the initial mixture, and with the presence of thiourethane. This compositional drift of the gel with the presence of TU was attributed to the preferential dissolution of TEGDMA into the TU network. Tg and ν decreased with the addition of TU, as expected. The addition of TU produced more homogeneous networks, as evidenced by narrower breadth of the tan delta curve. CONCLUSION: The addition of TU affected the composition of the sol/gel in crosslinked networks, which were more homogeneous and presented 2-fold less potentially toxic leachates than the methacrylate controls. CLINICAL SIGNIFICANCE: The addition of TU may produce less cytotoxic materials based on the increased conversion and reduced amount of unreacted extractables from its network after water storage.

Effect of thermally deposited siloxane-methacrylate coating on bonding to glass fibre posts.

AIM: To evaluate the alterations promoted by a thermally deposited siloxane-methacrylate coating on the surface of glass fibre posts and their effect on the bond strength of resin-core materials to the posts. METHODOLOGY: Fibre post surfaces were treated with experimental thermally deposited siloxane-methacrylate coatings or clinically available treatments (i.e. hydrogen peroxide and methylene chloride); nontreated posts were used as controls. The contact angles formed between the post surface and the water/adhesive were measured with a tensiometer. Scanning electron microscopy and electron dispersive spectroscopy were used to examine the topographies and chemical changes in the post surfaces following treatment. Surface roughness was evaluated with laser interferometry. Core resin was bonded to the fibre posts, and microtensile bond strength testing was subsequently performed. The data were individually submitted to anova and Tukey's tests (α = 0.05). RESULTS: The water contact angle was reduced significantly (P < 0.05) by the thermally deposited siloxane-methacrylate coating. All treatments significantly increased the adhesive contact angle (P ≤ 0.016) compared to the control as well as the surface roughness (P ≤ 0.006) and the amount of Si on post surfaces. Greater percentages of Si were observed for the thermally deposited coating. The bond strength to the posts was significantly improved by the thermally deposited coating (P < 0.05), whereas the other treatments did not differ from the control. CONCLUSION: Treating the surface of glass fibre posts with a thermally deposited siloxane-methacrylate coating improved the bond strength to resin-based materials. The coating could be performed by manufacturers of glass fibre posts in order to reduce the number of clinical steps required for luting posts into root canals.

Etching a fiber post surface with high-concentration bleaching agents.

INTRODUCTION: Commonly, resin composites/cements fail to achieve proper bonding to fiber posts when their surfaces have not been previously etched. This study evaluated the effect of the concentration and application mode of hydrogen peroxide on the surface topography and bond strength of resin composite to glass-fiber posts. METHODS AND MATERIALS: Fiber posts were immersed in 24% or 35% solutions (a high-concentration bleaching agent) of hydrogen peroxide (H2O2), or these solutions were applied over the post surface using a microbrush (n=10). Posts without any treatment were used as a control. After etching, the posts were silanated and an adhesive was applied. The posts were positioned in a mold, and a resin composite was incrementally inserted and light-cured. The post/resin assembly was serially sectioned into several beams that were subjected to a tensile bond strength test. The data were subjected to the two-way analysis of variance and Tukey test (α=0.05). The Dunnet's test was used to compare the experimental conditions to the control. The surface topography was analyzed using scanning electronic microscopy. RESULTS: The non-etched post presented a relatively smooth surface without fiber exposure. Except for the application of 24% H2O2, the other experimental conditions increased the number of exposed fibers and bond strength in relation to the control. Although immersion resulted in higher values for the 24% H2O2 application, the mode of application did not alter bond strength when 35% H2O2 was used. CONCLUSIONS: The effect of the mode of application of H2O2 depended on its level of concentration. A high-concentration bleaching agent improved the bond strength of the resin composite to the post surface, regardless of which mode was used.

The effect of prophylaxis method on microtensile bond strength of indirect restorations to dentin.

The aim of this study was to evaluate the effect of different materials used for dentin prophylaxis on the microtensile bond strengths (µTBS) of adhesively cemented indirect composite restorations. Sixty bovine incisors had the buccal surface ground with wet #600-grit silicon carbide abrasive paper to obtain a flat exposed superficial dentin and were submitted to different prophylaxis protocols, as follows: 3% hydrogen peroxide (HydP); 0.12% chlorhexidine (Chlo); sodium bicarbonate jet (SodB); 50-µm aluminum oxide air abrasion (AirA); pumice paste (PumP), and control group-water spray (Cont). After prophylaxis protocols a resin composite block (3.0 mm × 5.0 mm × 5.0 mm) was adhesively cemented using dual resin cement (Rely X ARC). After 24 hours of water storage, specimens were serially sectioned perpendicular to the bonded interface into 1-mm-thick slices. Each specimen was trimmed with a diamond bur to an hourglass shape with a cross-sectional area of approximately 1.0 mm(2) at the bonded area. Specimens were tested (µTBS) at 0.5 mm/min using a universal testing machine. Scanning electron microscopy was used to examine the effects of prophylaxis techniques on dentin. Bond strength data (MPa) were analyzed by one-way analysis of variance and failure mode by Fisher test (α=0.05). µTBS data, means (SD), were (different superscripted letters indicate statistically significant differences): AirA, 25.2 (7.2)(a); PumP, 24.1 (7.8)(a); Chlo, 21.5 (5.6)(a); Cont, 20.6 (8.1)(a); HydP(,) 15.5 (7.6)(b); and SodB(,) 11.5 (4.4)(c). The use of aluminum oxide air abrasion, pumice paste, and chlorhexidine before acid etching did not significantly affect µTBS to dentin; however, the use of hydrogen peroxide and sodium bicarbonate jet significantly reduced µTBS.

Application of a computational model of vagus nerve stimulation.

OBJECTIVES: The most widely used and studied neurostimulation procedure for medically refractory epilepsy is vagus nerve stimulation (VNS) Therapy. The goal of this study was to develop a computational model for improved understanding of the anatomy and neurophysiology of the vagus nerve as it pertains to the principles of electrical stimulation, aiming to provide clinicians with a systematic and rational understanding of VNS Therapy. MATERIALS AND METHODS: Computational modeling allows the study of electrical stimulation of peripheral nerves. We used finite element electric field models of the vagus nerve with VNS Therapy electrodes to calculate the voltage field for several output currents and studied the effects of two programmable parameters (output current and pulse width) on optimal fiber activation. RESULTS: The mathematical models correlated well with strength-duration curves constructed from actual patient data. In addition, digital constructs of chronic versus acute implant models demonstrated that at a given pulse width and current combination, presence of a 110-µm fibrotic tissue can decrease fiber activation by 50%. Based on our findings, a range of output current settings between 0.75 and 1.75 mA with pulse width settings of 250 or 500 µs may result in optimal stimulation. CONCLUSIONS: The modeling illustrates how to achieve full or nearly full activation of the myelinated fibers of the vagus nerve through output current and pulse width settings. This knowledge will enable clinicians to apply these principles for optimal vagus nerve activation and proceed to adjust duty cycle and frequency to achieve effectiveness.

Influence of matrix metalloproteinase synthetic inhibitors on dentin microtensile bond strength of resin cements.

This study evaluated the effect of dentin pretreatment with 2% chlorhexidine (CHX) or 24% ethylenediamine tetra-acetic acid gel (EDTA) on the dentin microtensile bond strength (µTBS) of resin cements. Composite blocks were luted to superficial noncarious human dentin (n=10) using two resin cements (RelyX ARC [ARC] and RelyX U100 [U100]) and three dentin pretreatments (without pretreatment-control, CHX, and EDTA). CHX was applied for 60 seconds on the acid-etched dentin in the ARC/CHX group, and for the same time on smear layer-covered dentin in the U100/CHX group. EDTA was applied for 45 seconds on smear-covered dentin in the U100/EDTA group, and it replaced phosphoric acid conditioning in the ARC/EDTA group for 60 seconds. After storage in water for 24 hours, specimens were prepared for microtensile bond strength testing. The results were submitted to two-way analysis of variance (ANOVA) followed by Tukey test. ARC produced significantly higher µTBS (p<0.05) compared to the U100, except when EDTA was used. For ARC, no pretreatment and CHX produced higher µTBS than EDTA. For U100, EDTA produced higher µTBS; no statistical difference occurred between CHX pretreatment and when no pretreatment was performed. While CHX did not affect immediate dentin bond strength of both cements, EDTA improved bond strength of U100, but it reduced dentin bond strength of ARC.

Efeito de um programa de manejo farmacoterapêutico em um grupo de idosos com hipertensão em Aracaju-Sergipe / Effect of a drug therapy management program in a group of elderly patients with hypertension in Aracaju (Sergipe, Brazil).

O presente estudo visou avaliar o efeito de um programa de manejo farmacoterapêutico no atendimento de idosos com hipertensão arterial sistêmica assistidos em unidade básica de saúde no município de Aracaju-Sergipe. Foram selecionados 30 idosos portadores de hipertensão, entre 60 e 75 anos de ambos os gêneros. Foi realizado um estudo de intervenção. Ao longo do estudo foram avaliadas as mudanças referentes ao manejo da farmacoterapia, de janeiro de 2007 a agosto de 2008. As variáveis analisadas foram: perfil sócio-demográfico e farmacoterapêutico e freqüência de comorbidades. A média de idade foi 69 ± 4 anos, com prevalência do gênero feminino. Os dados obtidos mostraram freqüência das comorbidades, especialmente nos sistema cardiovascular (100%) e músculo-esquelético (90%). Com relação ao perfil farmacoterapêutico foram identificados 76 diferentes tipos de especialidades farmacêuticas. Os medicamentos mais consumidos foram a hidroclorotiazida (53,3%) e o captopril (30%). Além disso, as intervenções reduziram o uso de AINEs (25,3% para 10%) e de polifarmácia (de nove para seis pacientes). O levantamento do perfil farmacoterapêutico forneceu elementos relevantes para compreender o uso de medicamentos em uma unidade de saúde, bem como, para eleger prioridades no cuidado aos idosos com hipertensão e elaborar estratégias em que o farmacêutico possa intervir de modo a reduzir e prevenir problemas farmacoterapêuticos.

This study was designed to assess the effect of a drug therapy management program on the treatment of elderly patients with systemic arterial hypertension who were attended at a primary health care unit (PCHU) in the city of Aracaju (SE). An intervention study was carried out at the PCHU, for which a sample of 30 elderly patients (60 - 75 years old) with hypertension, of both genders, was selected. During the study, changes in drug therapy management, from January 2007 up to August 2008, were assessed. The variables analyzed were socio-demographic and drug therapy profiles, as well as the frequency of comorbidity. The mean age was 69 ± 4 years, with a preponderance of women. The data showed a high frequency of comorbidity, especially in cardiovascular (100%) and musculoskeletal (90%) systems. Regarding the drug therapy profile, 76 different drugs were found. Those consumed most were hydrochlorothiazide (53.3%) and captopril (30%). The interventions reduced the prescription of NSAIDs (25.3% to 10%) and the practice of polypharmacy (nine to six patients). The drug therapy profile obtained from the survey provided details that could be employed to understand the use of drugs in a PCHU; for instance, to select priorities in caring for the elderly with hypertension and develop strategies in which the pharmacist can intervene to reduce and prevent drug therapy problems.

Influence of endodontic sealer cement on fibreglass post bond strength to root dentine.

AIM: To test the hypothesis that the composition of endodontic sealer cements and the time elapsed between root filling and fibreglass post fixation interferes with adhesion to root canal dentine. METHODOLOGY: Sixty bovine incisor roots were divided into five groups (n = 12): CI, unfilled; SI, filled with a calcium hydroxide-based cement-Sealer 26, and immediate post fixation; S7, Sealer 26 and post fixation after 7 days; EI, filled with a zinc oxide and eugenol-based cement-Endofill and immediate fixation; and E7 Endofill and post fixation after 7 days. The posts were cemented with adhesive system and dual resin cement. Ten roots were cross-sectioned to obtain two 1-mm-thick discs for each cervical (TC), middle (TM) and apical (TA) third of the prepared root portion. The posts were submitted to a micropush-out test. The other two teeth were evaluated using scanning electron microscopy to analyse the bond interface. Data were analysed using anova, Tukey and Dunnett tests (P < 0.05). RESULTS: Group EI was associated with a significant reduction in bond strength values irrespective of the root region; TC = 3.50 MPa (P = 0.0001); TM = 2.22 MPa (P = 0.0043) and TA = 1.45 MPa (P = 0.003). Region of canal had an influence on the values for the cement used in group E7, in which only the TA presented differences from the CI. CONCLUSIONS: Endofill interfered negatively with the bond to root dentine along its full length and in the TA when post fixation was delayed for 7 days. Bond strength decreased from crown to apex in all groups.

Distribution and population structure of the fish Cyphocharax gilbert (Characiformes: Curimatidae) in the Lower Paraíba do Sul River, Brazil

The distribution and population structure of Cyphocharax gilbert in four areas of the lower Paraíba do Sul River and its major tributaries (22ºS, 43ºW) were analyzed between March 1989 and February 1990. The species was common throughout the area, preferring major rivers with high turbidity and sand-mud substrates and range of length and size of specimens found varied depending on the particular characteristics of the site. A predominance of females was found in only area. Nevertheless, in all areas the bimonthly analysis showed preponderance of one of the sexes in periods before or after spawning. Males prevailed in shorter length classes and females in longer ones. There was a prevalence of young in one area that probably was used as a growth and feeding zone. Rev. Biol. Trop. 55 (3-4): 1015-1023. Epub 2007 December, 28.

Se analizó aspectos de la distribución y estructura poblacional de Cyphocharax gilbert en cuatro diferentes áreas del cause bajo del Rio Paraíba do Sul y sus principales afluentes (22ºS, 43ºW), entre marzo de 1989 y febrero de 1990. La especie fue común en toda su extención, ocupando preferentemente los ríos grandes con aguas turbias y substrato de arena-lodo. Los ámbitos de longitud y frecuencia de tamaños variaron con el lugar. Solo en una de las áreas hubo mayor proporción de hembras. Sin embargo, el análisis bimensual mostró una preponderancia de uno de los sexos en períodos antes y después del período reprodutivo en todas las áreas. Los machos prevalecen en los tamaños inferiores y las hembras en los superiores. Huvo una prevalencia de jóvenes en un área usada probablemente como una región para alimentación y crecimiento.

Influence of the shape core on custom cast dowel and core removal by ultrasonic energy.

The aim of this study was to assess the influence of the shape of custom cast dowel and cores on their removal by the use of ultrasound technique. Twenty-four single-rooted bovine teeth were prepared and had cast dowel fixed with zinc phosphate cement. The teeth were randomly divided into two groups: group I- received custom cast dowel and cores made without the coronal portion anatomy, simulating removal this portion with a bur, and group II- received cores that reproduced the coronal anatomy. Both were treated with an ultrasound device in two three-minute cycles (US). The force necessary for dowel removal was determined using a mechanical test machine. In the second stage of the study, the custom cast dowel and cores were again cemented and no ultrasound vibration was used on them (C). Data were submitted to the two-way anova (2 x 2) and Tukey test (P < 0.05), resulting in decreased tensile strength values (Kgf): GIC (49.85 +/- 11.10); GIIC (48.22 +/- 11.09); GIIUS (32.36 +/- 6.21) and GIUS (8.0 +/- 7.52). It was concluded that the shape of the core without the anatomic coronal portion facilitated removal of intra-radicular retention only when associated with the use of ultrasound.

Distribution and population structure of the fish Cyphocharax gilbert (Characiformes: Curimatidae) in the lower Paraíba do Sul River, Brazil.

The distribution and population structure of Cyphocharax gilbert in four areas of the lower Paraíba do Sul River and its major tributaries (22 degrees S, 43 degrees W) were analyzed between March 1989 and February 1990. The species was common throughout the area, preferring major rivers with high turbidity and sand-mud substrates and range of length and size of specimens found varied depending on the particular characteristics of the site. A predominance of females was found in only area. Nevertheless, in all areas the bimonthly analysis showed preponderance of one of the sexes in periods before or after spawning. Males prevailed in shorter length classes and females in longer ones. There was a prevalence of young in one area that probably was used as a growth and feeding zone. v.

When might hemispheric favouring of epileptiform discharges begin?

PURPOSE: EEG studies based on adult populations report interictal epileptiform discharges (EDS) favour the left hemisphere. It is not clear when favouring becomes apparent as similar paediatric studies have not been performed. METHODS: The authors reviewed 1,579 paediatric EEG interpretations for evidence of hemispheric favouring of focal epileptiform discharges. Analysis focused on first-time EEG results. RESULTS: Right hemispheric favouring of interictal epileptiform discharges occurs in childhood, it remits around 5 years of age whereupon left-sided favouring occurs more frequently (P=0.004, Fisher's Exact). CONCLUSION: Hemispheric vulnerabilities to interictal focal epileptiform activity may display discrete age-related favouring. These findings are discussed in context of normal hemispheric maturation.

[Magnesium and myocardial infarction. Brazilian aspects]. / O magnésio e o infarto do miocárdio: aspectos brasileiros.

Most of the brazilian's territory is poor in magnesium (Mg) and an evaluation of urinary Mg indicated very low concentration of this cation in a normal population sample. The study of the behavior of plasmatic Mg in the acute phase of uncomplicated myocardial infarction permitted the following conclusions; a) during the first three days of the clinical course there is significant hypomagnesemia; b) magnesemia rises progressively during the three days of infarction, without however reaching normal levels. The lymphocytic magnesium also show the same behavior. Mg infusion in patients with acute myocardial infarction (four grams of MgSO4 during the first three days) reduced the incidences of arrhythmias, death and the size of infarction, in São Paulo. Another study in Bahia also showed reduction of mortality with infusion of 10 grams of MgSO4 in 24 hours. These studies about the protective role of Mg show potential limitations because the samples were small.

Efeitos sobre o recem-nascido da alcalose respiratoria materna. / Effects on the newborn infant of maternal respiratory alkalosis

Os efeitos da intensa hiperventilacao materna sobre o equilibrio acido-basico e a condicao clinica do recem-nascido foram estudados em pacientes submetidos a cesareana com anestesia geral inalatoria e ventilacao controlada. Em um grupo de controle de 10 pacientes normoventiladas, foram analisados o pH, PaCO2,PaO2 excesso de bases e saturacao da hemoglobina no sangue arterial materno e de arteria e veia umbilicais. Estes valores foram comparados com os obtidos em grupo de 10 pacientes submetidas a hiperventilacao intensa. Com a hiperventilacao materna intensa houve queda na PaO2, saturacao da hemoglobina e PaCO2, acompanhado de aumento no pH, no sangue de arteria e veia umbilicais e nascimento de fetos clinicamente mais deprimidos avaliados segundo o indice de Apgar