bluuebunny/crossref_metadata_2025 huggingface dataset:
Microhabitat Characteristics That Regulate Ant Richness Patterns: The Importance of Leaf Litter for Epigaeic Ants
Authors: Queiroz Antonio Cesar Medeiros de , Ribas Carla Rodrigues , França Filipe Machado
Published: February 2014

We assessed the effect of conditions and resources on the species richness of epigaeic ants in a cloud forest of the Ibitipoca State Park, Brazil. We hypothesized that the characteristics that are best related with the epigaeic microhabitat affects ant richness more closely than other characteristics. At each sampling site (36 in total) we set up an epigaeic pitfall to capture ants and measured the following environmental variables (conditions and resources): tree density, tree height, circumference at breast height, density of the herbaceous and shrubby vegetation, weight and heterogeneity of the leaf litter, and canopy cover. We built general linear models and used a function that classifies alternative models according to the second-order Akaike information criterion (AICc), in order to assess which environmental variables affect ant species richness. We collected 37 ant species and the models that better explained the variations in ant richness were: (1) null model; (2) heterogeneity of the leaf litter; and (3) weight of the leaf litter. These two environmental variables are positively related to ant richness. It is possible that epigaeic ants are influenced by the high quantity and quality of food and nesting sites provided by a heterogeneous and abundant leaf litter. Relationships between species richness and environmental characteristics should consider different predictor variables related to the microhabitat, since each microhabitat may have a specific pattern and predictor variable. Thus, the understanding of the effects of the microhabitat variables on species richness could help predicting the consequences of anthropogenic impacts
Notes on biology of Brazilian populations of ants of the Pachycondyla foetida species complex (Formicidae: Ponerinae)
Authors: Fernandes Itanna Oliveira , De Oliveira Marcio Luiz , Delabie Jacques Hubert Charles
Published: February 2014

In ants, biology studies are especially important to complete the information aiming to identify species belonging to unresolved or confused taxa in taxonomy. Such observations allow the inclusion of biological data with other characteristics of determined group, something that preserved specimens in collections do not reveal, such as nesting site, foraging time, nuptial flight and especially the relationship between castes, supporting taxonomic analysis and descriptions. Here, nests of three species of the complex foetida of the genus Pachycondyla were observed and collected in three Brazilian localities. Pleometrosis, secondary monogyny and cannibalism were observed for the ant P. inversa. In many ant species, queens newly mated are associated with other queens to establish new colonies, independent of parenthood. In the ant genus Pachycondyla, the reproductive structure varies broadly and aggressiveness seems to be an important factor in structuring the organization and reproductive division in the colony. The occurrence of males in nests of P. inversa and P. curvinodis allowed the description of males. The nuptial flight period was estimated to of P. inversa (August), P. villosa (October) and P. curvinodis (November).
Temporal variation in the abundance of Orchid Bees (Hymenoptera: Apidae) in a Neotropical Hygrophilous Forest
Authors: Castro Maurício Meirelles do Nascimento , Garófalo Carlos Alberto , Serrano José Carlos , Silva Cláudia Inês
Published: February 2014

Although bees are important pollinators in several ecosystems around the world, studies on bee diversity in hygrophilous forests are scarce. This type of vegetation is restricted to permanently wet soils and, therefore, has particular floristic, structure and physiognomy. The goal of the present study was to inventory and analyze the temporal variation of the euglossine bees that occur in a neotropical hygrophilous forest. In order to sample male bees we used four chemical baits, eucalyptol, eugenol, vanillin, and methyl salicylate. The captures were made once a month, from March 2010 to February 2011, from 9:00 am to 12:00 pm. We captured 113 individuals of three genera and five species (in decreasing order of abundance): Eulaema nigrita Lepeletier, 1841 (n=52), Euglossa pleosticta Dressler, 1982 (34), Exaerete smaragdina (Guérin-Méneville, 1844) (12), Euglossa carolina Nemésio, 2009 (11), and Euglossa fimbriata Rebêlo & Moure, 1968 (4). The most attractive bait was eucalyptol (n=98), followed by vanillin (11), and eugenol (4). Both temperature and rainfall affected significantly the distribution of the number of males throughout the year. The highest number of Euglossini species and individuals was sampled in the warm and rainy season, with activity peaks varying among species.
Neotenic reproductives influence worker caste differentiation in the termite Reticulitermes speratus (Isoptera; Rhinotermitidae)
Authors: Hayashi Yoshinobu , Miyata Hitoshi , Kitade Osamu , Lo Nathan
Published: February 2014

Division of labor among castes in social insect colonies increases ergonomic efficiency and colony-level fitness, and has played a key role in the ecological success of social insects. Knowledge of the factors that regulate castes is important for understanding adaptive social organization. Our previous study on the termite Reticulitermes speratus demonstrated that the presence of a pair of nymphoid reproductives during development affected offspring caste ratios. In the present study, we investigated further the influence of individual neotenics on offspring caste ratios. Parthenogenetically-produced offspring were reared in worker-tended experimental colonies with the addition of different forms (nymphoid or ergatoid) and numbers of neotenics, and compared the caste ratios of the offspring between the different experimental treatments. We found that all offspring in worker-only tended colonies became nymphs, while a proportion of offspring in colonies with a single neotenic (with the exception of male ergatoids) differentiated into workers. These results show offspring caste ratios are influenced by the presence of single female ergatoids, single female and male nymphoids, while they remain unaffected by the presence of male ergatoids.
Evaluation of formic acid toxicity to subterranean termite, Reticulitermes chinensis Snyder
Authors: Xie Yongjian , Du Qin , Huang Qiuying , Lei Chaoliang
Published: February 2014

This study examined formic acid contact and fumigation toxicity to R. chinensis in the laboratory. In the contact toxicity bioassay, the LD50 values ranged from 267.86 to 287.68 μg adult-1 for workers, 279.09 μg adult-1 for alates (male and female) and 223.08 μg adult-1 for soldiers after 24 h, respectively. In the fumigation bioassays, the LC50 values ranged from 0.84 to 1.08 μg ml-1 for workers, 1.19 μg ml-1 for alates (male and female) and 0.57 μg ml-1 for soldiers after 24 h, respectively. At the concentration of 2.50 μg ml-1, the KT50 value of formic acid ranged from 25.38 to 34.75 min for workers, from 42.21 to 45.62 min for alates (male and female), from 32.18 to 36.37 min for soldiers. Although formic acid was significantly less toxic to subterranean termite than bifenthrin, but higher toxic to many other pest insects. The findings of this study provide important confirmation of formic acid with fumigation toxicity against termite. It may be worth investigating the use of formic acid for managing subterranean termite.
Nuclear Magnetic Resonance Spectra and 207Pb Chemical-Shift Tensors of Lead Carboxylates Relevant to Soap Formation in Oil Paintings
Authors: Catalano Jaclyn , Yao Yao , Murphy Anna , Zumbulyadis Nicholas , Centeno Silvia A. , Dybowski Cecil
Published: February 2014

Soap formation in traditional oil paintings occurs when heavy-metal-containing pigments, such as lead white, 2PbCO3·Pb(OH)2, and lead tin yellow type I, Pb2SnO4, react with fatty acids in the binding medium. These soaps may form aggregates that can be 100–200 μm in diameter, which swell and protrude through the paint surface, resulting in the degradation of the paint film and damage to the integrity of the artwork. The factors that trigger soap formation and the mechanism(s) of the process are not yet well understood. To elucidate these issues, chemical and structural information is necessary, which can be obtained using solid-state 207Pb and 13C nuclear magnetic resonance (NMR). In this article, we report 207Pb and 13C solid-state NMR spectra and 207Pb chemical-shift tensors of lead carboxylates implicated in soap formation: lead stearate, lead palmitate, and lead azelate, in addition to lead oleate and lead heptanoate for comparison. The 13C cross polarization with magic-angle spinning (MAS) spectra of these lead carboxylates show resonance doubling for the carbons closest to the lead, indicating two different conformations of the fatty acid chains in the asymmetric unit. The 207Pb NMR spectra, from which tensors were determined, were obtained with direct excitation and spin-temperature alternation, with and without MAS, and with the wide band uniform rate smooth truncation Carr-Purcell-Meiboom-Gill pulse sequence. The results of these experiments show that the local coordination environment of lead azelate is different from lead palmitate and lead stearate and could thus be distinguished from these in a paint film displaying soap formation. In addition, comparing the 207Pb NMR chemical-shift tensors of the lead carboxylates studied shows that crystal packing of the acyl chains may be a factor in determining the coordination environment around the lead.
J-PET analysis framework for the prototype TOF-PET detector
Authors: Krzemień Wojciech , Silarski Michał , Stoła Karol , Trybek Damian , Bednarski Tomasz , Białas Piotr , Czerwiński Eryk , Kapłon Łukasz , Kochanowski Andrzej , Korcyl Grzegorz , Kowal Jakub , Kowalski Paweł , Kozik Tomasz , Molenda Marcin , Moskal Paweł , Niedźwiecki Szymon , Pałka Marek , Pawlik Monika , Raczyński Lech , Rudy Zbigniew , Salabura Piotr , Sharma Neha Gupta , Słomski Artur , Smyrski Jerzy , Strzelecki Adam , Wiślicki Wojciech , Zieliński Marcin , Zoń Natalia
Published: February 2014

Novel time-of-flight positron emission tomography (TOF-PET) scanner solutions demand, apart from the state-of-the-art detectors, software for fast processing of the gathered data, monitoring of the whole scanner, and reconstruction of the PET image. In this article, we present an analysis framework for the novel STRIP-PET scanner developed by the J-PET collaboration in the Institute of Physics of the Jagiellonian University. This software is based on the ROOT package used in many particle physics experiments.
Characterization of ABC transporters in human skin
Authors: Osman-Ponchet Hanan , Boulai Anais , Kouidhi Magali , Sevin Karine , Alriquet Marion , Gaborit Alexandre , Bertino Béatrice , Comby Pierre , Ruty Bernard
Published: February 2014

Background: Most identified drug transporters belong to the ATP-binding cassette (ABC) and solute carrier (SLC) families. Recent research indicates that these transporters play an important role in the absorption, distribution and excretion of drugs, and are involved in clinically relevant drug-drug interactions for systemic drugs. However, very little is known about the role of drug transporters in human skin, especially in the disposition of topically applied drugs, and their involvement in drug-drug interactions. The aim of this work was to characterize the ABC transporters in human skin.

Methods: Expressions of ABCB1 multidrug resistance protein 1 (MDR1) also known as P-gp, ABCC1 and ABCC2 multidrug resistance-associated protein 1 and 2 (MRP1 and MRP2), and ABCG2 brest cancer resistance protein (BCRP) in human skin tissues were analyzed by quantitative real-time polymerase chain reaction (RT-PCR). The modulations of ABCB1 and ABCC1 expressions were analyzed after ex vivo treatment of human skin with rifampicin and dexamethasone. The localization of the major transporter MRP1 in human skin was analyzed by immunohistochemistry. Finally, functional analysis of MRP1 in human skin was performed using different specific substrates and inhibitors.

Results: The expressions of ABCB1, ABCC1, ABCC2, and ABCG2 were all detected in human skin, of which the expression of ABCC1 was considered the most important. The comparison of human skin with human hepatocytes and kidneys shows that the expression of ABCC1 increased 15-fold in skin than in hepatocytes. Immunohistochemistry revealed marked expressions of MRP1 within the hair follicle, sweat gland and muscle, as well as moderate expression in the basal epidermis. Functional analysis demonstrated that the skin absorptions of rhodamine 123, [3H]-vinblastine, and [3H]-LTC4 were markedly decreased in the presence of MRP1 inhibitors (verapamil and MK571), thus supporting the role of MRP1 in the uptake of compounds from the epidermal compartment as well as their secretion into the bloodstream and sweat ducts.

Conclusions: The present findings are the first to demonstrate the involvement of MRP1 in drug uptake in human skin.
Circadian rhythm, sleep pattern, and metabolic consequences: an overview on cardiovascular risk factors
Authors: Machado Roberta Marcondes , Koike Marcia Kiyomi
Published: February 2014

Sleep duration is a risk factor for cardiovascular disease. Alteration in sleep pattern can induce the loss of circadian rhythmicity. Chronically, this desynchronization between endogenous rhythm and behavioral cycles can lead to an adverse metabolic profile, a proinflammatory condition and can increase the risk of cardiovascular disease. The circadian cycle can vary due to environmental cues. The circadian pacemaker is located in the suprachiasmatic nuclei; this central clock coordinates the circadian rhythm in the central nervous system and peripheral tissues. The mechanisms involved in sleep disturbance, circadian misalignment and adverse metabolic effects have yet to be fully elucidated. This review looks over the association among sleep alteration, circadian rhythm and the development of risk factors implicated in cardiovascular disease.
Self-excited Oscillations and Fuel Control of a Combustion Process in a Rijke Tube
Authors: Pušenjak Rudolf R. , Tičar Igor , Oblak Maks M.
Published: February 2014

This paper treats the control of nonstationary oscillations of the pressure which arise in the combustion process of a Rijke tube. The low order model of a nonstationary combustion process in a Rijke tube with multiplicative feedback control function is considered, which is investigated by means of two-DOF coupled van der Pol oscillator. The self-excited oscillations in the combustion process are analysed by means of the Extended Lindstedt-Poincare (EL-P) method with multiple time scales. By applying the EL-P method, it is ascertained, that nonstationary oscillations are almost periodic with amplitude and phase, which are functions of the slow time scale. Without control of the fuel influx, the self excited oscillations can approach limit cycles. By applying the fuel control, the influence of control parameters on the quenching of the self excited oscillations is investigated in a phenomenon of competitive quenching and mutual synchronization with close frequencies and multiple harmonics, respectively.
Compatibilization of polyamide 6/poly(2,6-dimethyl-1,4-phenylene oxide) blends by poly(styrene-co-maleic anhydride)
Authors: Guo Zhenghong , Shen Yu , Fang Zhengping
Published: February 2014

The properties of polyamide 6 (PA6)/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends (60/40, wt%) compatibilized by poly(styrene-co-maleic anhydride) (SMA) were studied. The addition of SMA can form an in situ copolymer, SMA-graft-PA6. The SMA-graft-PA6 copolymer actually plays a key role as a compatibilizer to improve the interface between PA6 and PPO. It was found that the effect of compatibilization resulted in improvement of the morphology, impact strength and water absorbability of PA6/PPO blends (60/40, wt%), but with no favorable effects for thermal stability. However, at high SMA contents, the properties of PA6/PPO (60/40, wt%) blends deteriorated to some degree.
Effect of different amounts of modified talc on the mechanical, thermal, and crystallization properties of poly(butylene succinate)
Authors: Sun Bingxin , Chuai Chengzhi , Luo Si , Guo Ying , Han Chunyang
Published: February 2014

Poly(butylene succinate) (PBS) with different ratios of modified talc was prepared by twin-screw extruding. The effect of different loading amounts of talc on the mechanical, thermal, and crystallization properties of PBS was investigated. The mechanical test results indicate that the stiffness of the composites was increased linearly with increasing talc content, and the tensile strength and elongation stayed at relatively high levels when the talc amount is <15 phr. Thermal gravimetric analysis showed that the thermal stability of PBS composites was improved notably with a small amount (5–10 phr) of talc; however, high loading of talc did not help further improve the thermal stability. Differential scanning calorimetry data showed that the melting enthalpy (ΔHm), crystallization enthalpy (ΔHc), and crystallinity degree (Xc) decreased when the talc increased and crystallization temperature (Tc) was moving to relatively high values. The results of X-ray diffraction demonstrated that the incorporation of talc inhibited the PBS crystallization behavior significantly but did not change the crystal structure. Scanning electron microscopic studies indicated that the homogeneous dispersion and smoother fracture surfaces of the composite became inhomogeneous and coarse with higher talc loading.
Culture Change at Genentech: Accelerating Strategic and Financial Accomplishments
Authors: Chatman Jennifer
Published: February 2014

This case study describes the culture change process and positive outcomes at one of Genentech's largest divisions, Immunology and Opthamology (GIO). Senior Vice President Jennifer Cook worked with her team to develop a culture that would tie together four brands that previously were not in the same division. Despite various challenges along the way, Cook pursued a culture change approach with definitive and relatively rapid outcomes. This is a story of the role of leaders in undertaking and inspiring major culture change.
Managing Value in Supply Chains: Case Studies on the Sourcing Hub Concept
Authors: Agrawal Anupam , De Meyer Arnoud , Van Wassenhove Luk N.
Published: February 2014

A firm's raw material sourcing knowledge can be a strategic resource. This article explores how firms can capture and use this knowledge. It examines the sourcing experiences of four firms in four different countries in the automotive industry and identifies the raw material sourcing knowledge-related parameters. Synthesizing the findings from these case studies, it proposes the concept of the sourcing hub—a collaborative center involving the firm, its suppliers, and raw material suppliers—which can effectively capture and deploy the raw material sourcing knowledge for managing value in upstream sourcing.
Coping with Open Innovation: Responding to the Challenges of External Engagement in R&D
Authors: Salter Ammon , Criscuolo Paola , Ter Wal Anne L.J.
Published: February 2014

Open innovation often requires wholesale changes to the nature of R&D. However, academic research and managerial practice have paid little attention to the challenges that individuals face in the daily pursuit of open innovation. As a result, there is little understanding of how individuals cope with open innovation, and which organizational practices can support them in this role. Drawing on the experiences of R&D professionals, this article identifies four specific challenges and coping strategies of individuals engaged in open innovation. It proposes a range of open innovation practices that organizations can implement to better equip their staff to undertake effective external engagement.
LWA as Internal Curing Agent to Control Availability of Internal Curing Water in Concrete
Authors: Rendon Luis Emilio , Rendon Montserrat , Ramirez Norma
Published: February 2014

The effectiveness of lightweight aggregate (LWA) as an internal curing agent (ICA) to reduce concrete shrinkage is evaluated for repair concrete used in cultural heritage works (RCCHW) using curing periods of 30 days. Normal weight aggregate is replaced by LWA at volume replacement levels ranging from 10 to 14%. The mixtures contain Portland cement maintaining the paste content at approximately 24.1% of concrete volume. Comparisons are made with mixtures containing low-absorption granite and high-absorption limestone normal weight coarse aggregates. At the replacement levels used in this study, LWA results in a small reduction in concrete density, no appreciable effect on concrete compressive strength, and a decrease in concrete shrinkage for drying periods up to 30 days. With a curing period of 14 days, all mixtures with LWA exhibited less shrinkage than the mixtures with either low- or high-absorption normal weight aggregates.
Evaluation of Corrosion Rate of Steel Rebars Embedded in Mortar Mixed with Triturated Tire Particles
Authors: Flores Valdez Claudia Berenice , Pérez-Gutiérrez Francisco G. , Álvarez Imelda Esparza , García Orlando Guarneros , Rodríguez Reyna Sandra Luz
Published: February 2014

Different materials, such as triturated waste tire (WT) particles, have been proposed as aggregate to improve mortar properties and reduce its cost in recent years. Using WT as aggregate implies material recycling, providing an environmental benefit. Previous studies show controversy on the chloride ion diffusion coefficient in mortar test specimens as a function of the WT content. The objective of this investigation is to evaluate the corrosion rate of steel reinforcement embedded in mortar specimens using WT as aggregate when exposed to chlorides. Electrochemical techniques, mercury intrusion porosimetry and scanning electron microscope were used to measure corrosion rate, porosity and microstructure of mortar matrix, respectively. Corrosion rate and porosimetry results were found to directly correlate for test pieces with 7.5% of WT compared with control samples and test pieces containing 5%, 10% of WT; such results are supported by visual inspection of steel reinforcements. Our results show that substituting 7.5% of sand with WT when preparing mortar provides the optimum protection.
Structural and Photoluminescence Studies of Ni-doped ZnO Nanoparticles Synthesized by Solution Combustion Method
Authors: SILAMBARASAN Murugesan , SARAVANAN Shanmugam , OHTANI Naoki , SOGA Tetsuo
Published: February 2014

In this paper, the authors have reported the structural and photoluminescence (PL) studies of pure and nickel (Ni) doped zinc oxide (ZnO) nanoparticles synthesized by the solution combustion method. The structural, morphological and optical studies are carried out by powder x-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and PL spectra, respectively. The XRD pattern indicates that the prepared particles are in hexagonal wurtzite structure with the average crystalline size is around 35-50nm. Room temperature PL shows the near band edge related emission and the results are related several intrinsic defects in the ZnO nanoparticles.
Si Surface Orientation Dependence on the Electrical Characteristics of HfN Gate Insulator with sub-0.5 nm EOT Formed by ECR Plasma Sputtering
Authors: Atthi Nithi , Han Dae-Hee , Ohmi Shun-ichiro
Published: February 2014

This paper investigated the silicon substrate orientation dependence on the electrical properties of high-κ HfN gate insulator formed by electron-cyclotron-resonance (ECR) plasma sputtering. The effect of N2/4.9%H2 forming-gas annealing (FGA) was studied. By using N2/4.9%H2 FGA at 500°C for 20 min, the interfacial layer (IL) formation was not formed and led to the zero-interface layer (ZIL). The EOTs of 0.47 and 0.51 nm with leakage current of 1.1 and 1.4 A/cm2 (@VFB -1 V) were obtained on p-Si(100) and p-Si(110), respectively. The density of interface states (Dit) with the order of 1011 cm-2eV-1 was obtained on both p-Si(100) and p-Si(110). This suggests that the direct deposition of HfN film with ZIL prevented the degradation of electrical characteristics on the p-Si(100) and p-Si(110) substrate in comparison to the case of oxide-based hafnium gate insulator.
In situ determination of effective tip radius in dynamic atomic force microscopy
Authors: Maragliano C. , Glia A. , Stefancich M. , Chiesa M.
Published: February 2014

Atomic force microscopy (AFM) suffers from an important limitation: it does not provide quantitative information about the scanned sample. This is because too many unknowns come into play in AFM measurements. The shape of the tip is probably the most important. A technique able to characterize in situ the shape of the tip apex would represent an important step ahead to turn the AFM into a quantitative tool.

Standard methods can be destructive to the tip and are time consuming. Two main methods are currently used to characterize the tip radius in situ without affecting its shape. The first consists of characterizing the tip radius by monitoring the dynamics of the cantilever. The value of free amplitude, for which transitions from the attractive to repulsive force regimes are observed, strongly depends on the curvature of the tip. The second method to characterize the tip radius consists instead on fitting the capacitance curve of the tip-sample system with an analytical function.

In this work we compare the two methods to characterize in situ the tip radius and results are verified with SEM images. The value of the free amplitude is correlated with the value of R while the capacitance curve is derived with a method we proposed. Tips with different tip radii are used. The investigation is conducted with the aim of determining the most reliable technique for characterizing the tip radius for both sharp and blunt tips.
In Vitro Alkaline pH Resistance of Enterococcus faecalis
Authors: Weckwerth Paulo Henrique , Zapata Ronald Ordinola , Vivan Rodrigo Ricci , Tanomaru Filho Mário , Maliza Amanda Garcia Alves , Duarte Marco Antonio Hungaro
Published: February 2014

Enterococcus faecalis is a bacterial species often found in root canals with failed endodontic treatment. Alkaline pastes are widely used in Endodontics because of their biocompatibility and antimicrobial activity, but this microorganism can resist alkalinity. The purpose of this study was to evaluate in vitro the alkaline pH resistance of E. faecalis for different periods up to 14 days. Samples were obtained from the oral cavity of 150 patients from the Endodontic clinic. The pH of the experimental tubes (n=84) was first adjusted with 6M NaOH to pH values of 9.5, 10.5, 11.5 and 12.5 (21 tubes per pH). Twenty clinical isolates and the ATCC 29212 strain were tested. The 5 positive controls and experimental tubes of each pH were inoculated with 10 µL of bacterial suspension and incubated at 36 °C for 24, 48 and 72 h, 7 and 14 days. For each period, the turbidity of the medium was visually compared with a 0.5 McFarland standard. The presence of the microorganism was confirmed by seeding on M-Enterococcus agar. Four tubes containing BHI broth adjusted to the tested pHs were incubated for 14 days to verify if pH changes occurred. The pH of inoculated BHI broth was also measured on day 14 to determine if the microorganism acidified the medium. The growth of all E. faecalis strains occurred at pH 9.5 to 11.5 in all periods. Although turbidity was not observed at pH 12.5, there was growth of 13 and 2 strains at 24 and 48 h, respectively, on M-Enterococcus agar. No tube showed growth at pH 12.5 after 72 h. It was concluded that E. faecalis can survive in highly alkaline pH, and some clinical isolates require 72 h at pH 12.5 to be killed.
Preferences on Vital and Nonvital Tooth Bleaching: A Survey Among Dentists from a City of Southern Brazil
Authors: Demarco Flávio Fernando , Conde Marcus Cristian Muniz , Ely Caroline , Torre Eliana Nascimento , Costa José Ricardo Souza , Fernández María Raquel , Tarquinio Sandra Beatriz Chaves
Published: February 2014

This study evaluated the preferences of general dentists regarding vital and nonvital tooth bleaching therapies and investigated whether the time of clinical practice and post-graduate training influence these options. A cross-sectional study was conducted using a questionnaire with closed questions applied to dentists (n=276) of a mid-sized city of the southern Brazil (Pelotas, RS). Information was collected regarding sociodemographic variables, level of specialization and time since graduation. In addition, options regarding bleaching therapies including the first choice of material, technique and clinical practice for vital and nonvital tooth bleaching therapies were included. Data were submitted to descriptive analysis and the associations were evaluated using chi-square and Fisher exact tests (α=0.05). The response rate was 68% (n=187). At-home bleaching therapy was broadly preferred (78.1%) over in-office (21.9%) bleaching. For at-home bleaching, most dentists answered to use 10% carbamide peroxide (CP) (40.2%) and >30% hydrogen peroxide (HP) (31.7%) for nonvital therapies. The majority of dentists with post-graduation training preferred at-home bleaching techniques (p=0.003). At-home bleaching therapy was also more indicated by younger dentists. No association was found between the choice for nonvital bleaching therapies and time since graduation (p=0.532) or continuous education (p=0.083). In conclusion, at-home bleaching was preferred over in-office therapies; 10% CP and >30% HP were chosen as first option agents to treat discolored vital and nonvital teeth, respectively. The time in clinical practice and the level of specialization affected dentists' choices only for vital tooth bleaching treatment.
Microbiological Evaluation of Different Irrigation Protocols on Root Canal Disinfection in Teeth with Apical Periodontitis: An In Vivo Study
Authors: Cohenca Nestor , Silva Lea Assed Bezerra , Silva Raquel Assed Bezerra , Nelson-Filho Paulo , Heilborn Carlos , Watanabe Evandro , Saraiva Maria Conceição Pereira
Published: February 2014

The present in vivo study was designed to evaluate the efficacy of apical negative pressure irrigation (ANP), passive ultrasonic irrigation (PUI) and positive pressure irrigation (PP) in the reduction of intracanal bacteria of dogs' teeth with pulp necrosis and apical periodontitis. Eighty root canals were randomly distributed into 3 experimental and 2 control groups according to the irrigation delivery system: group ANP (n=20), group PUI (n=20), group PP (n=20), group PC (positive control – sterile saline irrigation; n=10) and group NC (negative control - vital pulps not subjected to bacterial inoculation; n=10). The first sample (S1) was collected at baseline, and the second sample (S2) was collected after the disinfection protocols. All samples were seeded in culture media for anaerobic bacteria. CFU counts were analyzed statistically by the Kruskal-Wallis, Dwass-Steel-Critchlow-Fligner post-hoc and Chi-square followed by Tukey like multiple comparisons for proportions (α=0.05). All experimental groups were effective in reducing Gram-positive bacteria compared with PC (p<0.05). Regarding the reduction of Gram-negative bacteria, group ANP was significantly better than PP (p<0.05). No statistically significant difference could be found between PP and PUI (p>0.05). In dog's teeth with apical periodontitis, the use of ANP and PUI can be considered promising disinfection protocols as both delivery systems promoted a significant bacterial reduction.
Mineral Loss and Morphological Changes in Dental Enamel Induced by a 16% Carbamide Peroxide Bleaching Gel
Authors: Soares Diana Gabriela , Ribeiro Ana Paula Dias , Sacono Nancy Tomoko , Loguércio Alessandro Dourado , Hebling Josimeri , Costa Carlos Alberto de Souza
Published: February 2014

The aim of this study was to compare the effect of a 16% carbamide peroxide (CP) gel and a 10% CP gel on mineralized enamel content and morphology. Enamel blocks from bovine incisors were subjected to a 14-day treatment (8 h/day) with 10% or 16% CP gels. Knoop microhardness was evaluated before bleaching and at 1, 7 or 14 days after this treatment (50 g/15 s). Mineral content (energy-dispersive x-ray spectroscopy), surface roughness and topography (atomic force microscopy) were evaluated at the 14-day period. Data were analyzed statistically by two-way ANOVA and Tukey's test (α=0.05). Significant microhardness reduction was observed at the 7 th and 14 th days for 10% CP gel, and for all bleaching times for 16% CP gel (p<0.05). At the 14-day period, a significant decrease in Ca and P content, increase on surface roughness (p<0.05) as well as on picks and valleys distance were observed when both bleaching gels were used. These enamel alterations were more intense for 16% CP gel. It was concluded that both CP-based gels promoted loss of mineral structure from enamel, resulting in a rough and porous surface. However, 16% CP gel caused the most intense adverse effects on enamel.
Efficacy of an Organic Solvent and Ultrasound for Filling Material Removal
Authors: Muller Gabriela Guardiola , Schonhofen Anielle Pinheiro , Mora Patricia Maria Poli Kopper , Grecca Fabiana Soares , So Marcus Vinicius Reis , Bodanezi Augusto
Published: February 2014

The aim of this study was to investigate whether a final rinse with Endosolv R® solvent and ultrasound resulted in cleaner root canal walls during endodontic retreatment. A total of 56 extracted premolar teeth were manually instrumented using a step-back flare technique and filled with gutta-percha and AH Plus sealer. After 9 months, the canals were retreated by removing the gutta-percha and sealer with ProTaper Universal Retreatment and rotary preparation with ProTaper Universal System up to an F5 file. As a final step, the teeth were randomly divided in 4 groups (n=14) and were subjected to passive ultrasonic irrigation (PUI) with either Endosolv R or distilled water. In the control groups, the irrigants were left undisturbed. Roots were cleaved and examined under scanning electron microscopy (SEM), and the amount of filling remnants on the canal walls was assessed by two calibrated examiners in a blinded fashion. Data were analyzed by the Kruskal-Wallis test and the Student-Newman-Keuls post hoc test (α=0.05). All groups presented filling debris in the three root canal thirds after retreatment. There were no significant differences between the groups or among the root canal thirds within each group (p>0.05). PUI with Endosolv R was not effective in the removal of filling debris from root canal walls.
Root Dentin Strain and Temperature Rise During Endodontic Treatment and Post Rehabilitation
Authors: Amade Euridsse Sulemane , Novais Veridiana Resende , Roscoe Marina Guimaraes , Azevedo Fabiane Maria Ferreira , Bicalho Aline Aredes , Soares Carlos Jose
Published: February 2014

This study investigated the effects of endodontic treatment procedures and different post systems rehabilitation steps on the strain and temperature rise on apical and cervical root dentin regions. Twenty-one extracted human canine teeth had two strain gages attached to the distal root surface and two thermocouples attached to the mesial root surface (cervical and apical). The strain and temperature rise were recorded during the following procedures: root canal preparation, final rinse and drying, root canal filling and canal relief. Then the teeth were divided into three groups (n=7), according to the type of post system: CPC, cast post and core; FGP, fiberglass post; and PSP, prefabricated steel post. Data continued to be recorded during the post space preparation, post modeling (only for CPC), post trying and post cementation. Data were subjected to a two-way ANOVA followed by Tukey's test (α=0.05). The post-space preparation caused the highest temperature rise (4.0-14.9 °C) and the highest strain in the apical region during irrespective of post type. The resin cement light-activation resulted in significant temperature increases in the cervical region for all of the groups. The canal relief and the post-space preparation produced highest temperature rises. The CPC post modeling resulted in higher root strain level similarly the level of post preparation. The PSP resulted in highest strain during post trying and post cementation.
A 3-D Finite Element Study of the Influence of Crown-Implant Ratio on Stress Distribution
Authors: Moraes Sandra Lucia Dantas de , Verri Fellippo Ramos , Junior Joel Ferreira Santiago , Almeida Daniel Augusto de Faria , Mello Caroline Cantieri de , Pellizzer Eduardo Piza
Published: February 2014

The purpose of this study was to assess the influence of the crown height of external hexagon implants on the displacement and distribution of stress to the implant/bone system, using the three-dimensional finite element method. The InVesalius and Rhinoceros 4.0 softwares were used to generate the bone model by computed tomography. Each model was composed of a bone block with one implant (3.75x10.0 mm) with external hexagon connections and crowns with 10 mm, 12.5 mm and 15 mm in height. A 200 N axial and a 100 N oblique (45°) load were applied. The models were solved by the NeiNastran 9.0 and Femap 10.0 softwares to obtain the results that were visualized by maps of displacement, von Mises stress (crown/implant) and maximum principal stress (bone). The crown height under axial load did not influence the stress displacement and concentration, while the oblique loading increased these factors. The highest stress was observed in the neck of the implant screw on the side opposite to the loading. This stress was also transferred to the crown/platform/bone interface. The results of this study suggest that the increase in crown height enhanced stress concentration at the implant/bone tissue and increased displacement in the bone tissue, mainly under oblique loading.
Microhardness of Enamel Adjacent to Orthodontic Brackets After CO2 Laser Irradiation and Fluoride Application
Authors: Stangler Leonardo Pucci , Romano Fábio Lourenço , Shirozaki Mariana Umekita , Galo Rodrigo , Afonso Alessandra Marques Correa , Borsatto Maria Cristina , Matsumoto Mírian Aiko Nakane
Published: February 2014

This study evaluated the effectiveness of carbon dioxide (CO2) laser combined or not with fluoride application on the surface microhardness of enamel adjacent to orthodontic brackets. Fifteen human molars were selected from which 30 enamel fragments measuring 4 mm2 were obtained. The fragments were embedded in PCV tubes with acrylic resin and prepared using water abrasive paper, felt disks and alumina. Orthodontic brackets cut in half were bonded to enamel and 3 microhardness readings were performed on the adjacent surface, as follows: initial, after cariogenic challenge and final. The specimens were divided into the following 3 groups (n=10): Group C: control, Group L: irradiated with CO2 laser, and Group FL: topical fluoride application and CO2 laser irradiation. After initial reading, the specimens were placed in a demineralizing solution for 32 h and the second reading was to verify if demineralization was uniform in all groups. After the treatments, the specimens were submitted to DES-RE cycling for 8 days followed by final surface microhardness reading. The data were analyzed statistically using ANOVA and Duncan test (α=0.05). At the final measurement Group FL obtained higher microhardness value than Groups C and L (p<0.05). Groups L and FL were statistically superior to Group C (p<0.05). Irradiation with CO2 laser around orthodontic brackets combined or not with topical fluoride application was effective to increase the surface microhardness of enamel.
Mechanical and Biological Properties of Acrylic Resins Manipulated and Polished by Different Methods
Authors: Santos Rogério Lacerda dos , Pithon Matheus Melo , Carvalho Fabiola Galbiatti , Ramos Aretha Aliny dos Santos , Romanos Maria Teresa Villela
Published: February 2014

This study evaluated the influence of the manipulation technique and polishing method on the flexural strength and cytotoxicity of acrylic resins. Two manipulation techniques and three polishing methods were used in the fabrication of acrylic plates that were divided into 6 groups (n=10). Groups MM, MC and MW: mass technique with mechanical polishing, chemical polishing and without polishing, respectively; and Groups SM, SC and SW: Saturation technique with mechanical polishing, chemical polishing and without polishing, respectively). Flexural strength was tested in a universal testing machine and the cytotoxicity assay used cell cultures (L-929) for periods of 24 h to 168 h. Flexural strength and cytotoxicity data were assessed using two-way and three-way ANOVA, respectively (α=0.05), followed by post hoc Bonferroni test for multiple comparisons. The effect of combinations of manipulation techniques and polishing methods on flexural strength showed significant differences only between Group SC and Groups MW, MM and MC (p<0.01). Cell viability ranged from 51% (3.9%) to 87,6% (3.2) in the 24-h time interval, and from 87.8% (5.0) to 95.7% (3.1%) in the 168-h time interval. With the increase of cell viability, from the third day (72 h), there was no significant difference among the groups, except between MM and SC (p<0.01) at 72 h. In conclusion, the manipulation technique and polishing method had more influence on the cytotoxicity than on flexural strength.
Effect of Two Microshear Test Devices on Bond Strength and Fracture Pattern in Primary Teeth
Authors: Tedesco Tamara Kerber , Garcia Eugenio Jose , Soares Fabio Zovico Maxnuck , Rocha Rachel de Oliveira , Grande Rosa Helena Miranda
Published: February 2014

This in vitro study evaluated the influence of two devices for application of shear load in microshear tests on bond strength and fracture pattern of primary enamel and dentin. Eighty primary molars were selected and flat enamel (40 teeth sectioned mesio-distally) and dentin (40 teeth sectioned transversally) surfaces were obtained. Both surfaces were polished to standardize the smear layer. Two-step etch-and-rinse adhesive systems (Adper Single Bond and XP Bond) were used. Polyethylene tubes was placed over the bonded surfaces and filled with composite resin. The microshear testing was performed after storage in water (24 h/37 °C) using two devices for application of microshear loads: a notched rod (Bisco Shear Bond Tester) or a knife edge (Kratos Industrial Equipment). Failure modes were evaluated using a stereomicroscope. Bond strength data were subjected to ANOVA and chi-square test to compare the failure mode distributions (α=0.05). No significant differences were observed between the groups for dentin and enamel bond strength or fracture patterns (p>0.05). The predominant failure mode was adhesive/mixed. In conclusion, the devices for application of shear loads did not influence the bond strength values, regardless of adhesive system and substrate.
Predisposing Factors for Traumatic Dental Injury in Primary Teeth and Seeking of Post-trauma Care
Authors: Siqueira Maria Betania Lins Dantas , Gomes Monalisa Cesarino , Oliveira Ana Cristina , Martins Carolina Castro , Granville-Garcia Ana Flavia , Paiva Saul Martins
Published: February 2014

The aim of the present study was to investigate predisposing factors for traumatic dental injury (TDI) in the primary dentition and seeking of dental care after the occurrence of TDI. A randomized population-based cross-sectional study was carried out with 814 children aged 3 to 5 years enrolled at public and private preschools in the city of Campina Grande, PB, Brazil. Parents were asked to fill out a questionnaire on demographic data and the child's history of TDI. TDI was evaluated by clinical examinations performed by three previously calibrated dentists (Kappa: 0.85 to 0.90). Bivariate and multivariate Poisson regression models were constructed for TDI and the parent-reported search for dental care (α=0.05). The prevalence of TDI was 34.6%. The most common type of TDI was enamel fracture (55.0%). The central incisors were the most frequently affected teeth (87.5%). Predictors for TDI in the primary dentition were household income >U$312.50 (PR: 1.355; 95% CI: 1.050-1.724) and overjet >2 mm (PR: 1.539; 95% CI: 1.219-1.942). The predictor for seeking dental care following TDI was parent's age >30 years (PR: 1.753; 95% CI: 1.039-2.960). Household income and overjet were associated with TDI. Among children having suffered TDI, parent's age is a crucial determinant for seeking dental care.
Impact of Malocclusion on Oral Health-Related Quality of Life among Brazilian Preschool Children: a Population-Based Study
Authors: Carvalho Anita Cruz , Paiva Saul Martins , Viegas Claudia Marina , Scarpelli Ana Carolina , Ferreira Fernanda Morais , Pordeus Isabela Almeida
Published: February 2014

The purpose of the present study was to evaluate the impact of malocclusion on Oral Health-Related Quality of Life (OHRQoL) of children and their families. A population-based cross-sectional study was carried out in Belo Horizonte, MG, Brazil. A representative sample of 1069 male and female preschoolers aged 60 to 71 months was randomly selected from public and private preschools and daycare centers. Data were collected using the B-ECOHIS. In addition, a questionnaire addressing socioeconomic and demographic data was self-administered by the parents/guardians. The criteria used to diagnose malocclusion were based on Foster and Hamilton (1969), Graboswki et al. (2007) and Oliveira et al. (2008). Descriptive, univariate and multiple Poison logistic regression analyses were carried out. The prevalence of malocclusion was observed in 46.2% of the children and deep overbite was the most prevalent type of malocclusion (19.7%), followed by posterior crossbite (13.1%), accentuated overjet (10.5%), anterior open bite (7.9%) and anterior crossbite (6.7%). The impact of malocclusion on OHRQoL was 32.7% among the children and 27.1% among the families. In Poisson multiple regression model adjusted for socioeconomic status, no significant association was found between malocclusion and OHRQoL of the children (PR=1.09, 95% CI: 0.96-1.24) and their families (PR=1.11, 95% CI: 0.94-1.31). It is concluded that children with malocclusion in this sample did not have a negative impact on their OHRQoL and of their families.
Do Clinical Experience Time and Postgraduate Training Influence the Choice of Materials for Posterior Restorations? Results of a Survey with Brazilian General Dentists
Authors: Nascimento Gustavo Giacomelli , Correa Marcos Britto , Opdam Niek , Demarco Flavio Fernando
Published: February 2014

The aims of this study were to evaluate the materials available for posterior restorations and to assess whether clinical experience time and post-graduate training influence dentists' choices. A cross-sectional study was conducted using a questionnaire with closed questions applied to dentists (n=276) of a mid-sized city of the southern Brazil. Information was collected regarding sociodemographic variables, level of specialization, time since graduation and working place. In addition, options regarding posterior restorations including the first choice of material, type of composite resin (if used) and use of rubber dam were also collected data. Data were submitted to descriptive analysis and the associations were evaluated using chi-square and Fisher's exact tests (α=0.05). The response rate was 68% (187). Direct composite resin was broadly indicated (73.2%) as the first-choice for posterior restorations. Most professionals used microhybrid composite (74.5%) and 42.6% of the participants used rubber dam for placement of posterior composite restorations. Dentists with more time of clinical practice used less composite (p=0.014). Specialists used more frequently rubber dam to restore posterior teeth than did non-specialists (p=0.006). The results of this survey revealed that direct composite was the first choice of dentists for posterior restorations; microhybrid was the preferred type of composite and the use of rubber dam for composite resin placement in posterior teeth was not frequent; time since graduation and level of specialization affected dentists' choices.