Effect of post-polymerization heat treatments on the cytotoxicity of two denture base acrylic resins

Introduction: Most denture base acrylic resins have polymethylmethacrylate in their composition. Several authors have discussed the polymerization process involved in converting monomer into polymer because adequate polymerization is a crucial factor in optimizing the physical properties and biocompatibility of denture base acrylic resins. To ensure the safety of these materials, in vitro cytotoxicity assays have been developed as preliminary screening tests to evaluate material biocompatibility. 3H-thymidine incorporation test, which measures the number of cells synthesizing DNA, is one of the biological assays suggested for cytotoxicity testing. Aim: The purpose of this study was to investigate, using 3H-thymidine incorporation test, the effect of microwave and water-bath post-polymerization heat treatments on the cytotoxicity of two denture base acrylic resins. Materials and Methods: Nine disc-shaped specimens (10 x 1 mm) of each denture base resin (Lucitone 550 and QC 20) were prepared according to the manufacturers' recommendations and stored in distilled water at 37°C for 48 h. The specimens were assigned to 3 groups: 1) post-polymerization in a microwave oven for 3 min at 500 W; 2) post-polymerization in water-bath at 55°C for 60 min; and 3) without post-polymerization. For preparation of eluates, 3 discs were placed into a sterile glass vial with 9 mL of Eagle's medium and incubated at 37°C for 24 h. The cytotoxic effect of the eluates was evaluated by 3H-thymidine incorporation. Results: The results showed that the components leached from the resins were cytotoxic to L929 cells, except for the specimens heat treated in water bath (p<0.05). Compared to the group with no heat treatment, water-bath decreased the cytotoxicity of the denture base acrylic resins. Conclusion: The in vitro cytotoxicity of the tested denture base materials was not influenced by microwave post-polymerization heat treatment.

Fatigue resistance of bovine teeth restored with resin-bonded fiber posts: Effect of post surface conditioning

This study evaluated the effect of post surface conditioning on the fatigue resistance of bovine teeth restored with resin-bonded fiber-reinforced composite (FRC). Root canals of 20 single-rooted bovine teeth (16 mm long) were prepared to 12 mm using a preparation drill of a double-tapered fiber post system. Using acrylic resin, each specimen was embedded (up to 3.0 mm from the cervical part of the specimen) in a PVC cylinder and allocated into one of two groups (n = 10) based on the post surface conditioning method: acid etching plus silanization or tribochemical silica coating (30 μm SiOx + silanization). The root canal dentin was etched (H2PO3 for 30 seconds), rinsed, and dried. A multi-step adhesive system was applied to the root dentin and the fiber posts were cemented with resin cement. The specimens were submitted to one million fatigue cycles. After fatigue testing, a score was given based on the number of fatigue cycles until fracture. All of the specimens were resistant to fatigue. No fracture of the root or the post and no loss of retention of the post were observed. The methodology and the results of this study indicate that tribochemical silica coating and acid etching performed equally well when dynamic mechanical loading was used.

Cementation of fiber post: influence of the cement insertion techniques on the bond strength of the fiber post-root dentin and the quality of the cement layer.

The aim of this study was to assess the influence of resin cement insertion methods on the bond strength of a fiber post to root dentin and quality of the cement layer. Forty bovine single-roots (length =16 mm) were randomly allocated into four groups, according to the cement insertion methods (N.=10): Gr1- Lentulo drill #40, Gr2- Centrix syringe, Gr3- Explorer #5, Gr4- fiber post. The root canals were prepared at 12 mm, using preparation bur # 3 of a cylinder quartz-FRC post (Aesthet post-plus, Bisco). The fiber posts were cemented using a multi-step etch-and-rinse adhesive system (All Bond 2®, Bisco) and a dual-cured resin cement (Duolink, Bisco). Each root was cut into seven samples: four samples of 1.8 mm thickness for push-out testing, and three with 0.5 mm for cement layer quality analyzing. One-way ANOVA was used for the push-out test values and the One-Way Kruskal-Wallis (P<0.05) and Dunn (10%) tests for the cement layer analyzes. ANOVA showed that the cement layer quality was affected by the cement insertion methods (P=0.0044): Gr1 (3.8 ± 1.3a), Gr2 (3.2 ± 1.3a), Gr3 (5.2 ± 1.5a,b) and Gr4 (5.2 ± 1.5b) (Dunn test), whereas the bond strength (MPa) was not affected by cement insertion methods: G1 (4.2 ± 1.3), G2 (3.2 ± 1.8), G3 (4.5 ± 0.9), G4 (3.1 ± 1.3). The fiber posts should be cemented with the assistance of the lentulo drill or centrix syringe to promote the best cement layer results.

Glutamatergic antagonism in the NTS decreases post-inspiratory drive and changes phrenic and sympathetic coupling during chemoreflex activation

For a better understanding of the processing at the nucleus tractus solitarius (NTS) level of the autonomic and respiratory responses to peripheral chemoreceptor activation, herein we evaluated the role of glutamatergic neurotransmission in the intermediate (iNTS) and caudal NTS (cNTS) on baseline respiratory parameters and on chemoreflex-evoked responses using the in situ working heart-brain stem preparation (WHBP). The activities of phrenic (PND), cervical vagus (cVNA), and thoracic sympathetic (tSNA) nerves were recorded before and after bilateral microinjections of kynurenic acid (Kyn, 5 nmol/20 nl) into iNTS, cNTS, or both simultaneously. In WHBP, baseline sympathetic discharge markedly correlated with phrenic bursts (inspiration). However, most of sympathoexcitation elicited by chemoreflex activation occurred during expiration. Kyn microinjected into iNTS or into cNTS decreased the postinspiratory component of cVNA and increased the duration and frequency of PND. Kyn into iNTS produced no changes in sympathoexcitatory and tachypneic responses to peripheral chemoreflex activation, whereas into cNTS, a reduction of the sympathoexcitation, but not of the tachypnea, was observed. The pattern of phrenic and sympathetic coupling during the chemoreflex activation was an inspiratory-related rather than an expiratory-related sympathoexcitation. Kyn simultaneously into iNTS and cNTS produced a greater decrease in postinspiratory component of cVNA and increase in frequency and duration of PND and abolished the respiratory and autonomic responses to chemoreflex activation. The data show that glutamatergic neurotransmission in the iNTS and cNTS plays a tonic role on the baseline respiratory rhythm, contributes to the postinspiratory activity, and is essential to expiratory-related sympathoexcitation observed during chemoreflex activation.

Multi-step adhesive cementation versus one-step adhesive cementation: push-out bond strength between fiber post and root dentin before and after mechanical cycling

This study evaluated the effects of mechanical cycling on resin push-out bond strength to root dentin, using two strategies for fiber post cementation. Forty bovine roots were embedded in acrylic resin after root canal preparation using a custom drill of the fiber post system. The fiber posts were cemented into root canals using two different strategies (N = 20): a conventional adhesive approach using a three-step etch-and-rinse adhesive system combined with a conventional resin cement (ScotchBond Multi Purpose Plus + RelyX ARC ), or a simplified adhesive approach using a self-adhesive resin cement (RelyX U100). The core was built up with composite resin and half of the specimens from each cementation strategy were submitted to mechanical cycling (45 degree angle; 37 degrees C; 88 N; 4 Hz; 700,000 cycles). Each specimen was cross-sectioned and the disk specimens were pushed-out. The means from every group (n = 10) were statistically analyzed using a two-way ANOVA and a Tukey test (P = 0.05). The cementation strategy affected the push-out results (P < 0.001), while mechanical cycling did not (P = 0.3716). The simplified approach (a self-adhesive resin cement) had better bond performance despite the conditioning. The self-adhesive resin cement appears to be a good option for post cementation. Further trials are needed to confirm these results.

Academic and clinical preparation in speech-language pathology and audiology: a global training consortium

ABSTRACT: Purpose: To describe a research-based global curriculum in speech-language pathology and audiology that is part of a funded cross-linguistic consortium among 2 U.S. and 2 Brazilian universities. Method: The need for a global curriculum in speechlanguage pathology and audiology is outlined, and different funding sources are identified to support development of a global curriculum. The U.S. Department of Education’s Fund for the Improvement of Post-Secondary Education (FIPSE), in conjunction with the Brazilian Ministry of Education (Fundacao Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior; CAPES), funded the establishment of a shared research curriculum project, “Consortium for Promoting Cross-Linguistic Understanding of Communication Disabilities in Children” for East Tennessee State University and the University of Northern Iowa and 2 Brazilian universities (Universidade Federal de Santa Maria and Universidade de São Paulo-Baurú). Results: The goals and objectives of the research-based global curriculum are summarized, and a description of an Internet-based course, “Different Languages, One World,” is provided Conclusion: Partnerships such as the FIPSE–CAPES consortium provide a foundation for training future generations of globally and research-prepared practitioners in speechlanguage pathology and audiology.

Preparation and study of magnetic thin film based sub-micron structures

Due to its high Curie temperature of 420K and band structure calculations predicting 100% spin polarisation, Sr2FeMoO6 is a potential candidate for spintronic devices. However, the preparation of good quality thin films has proven to be a non-trivial task. Epitaxial Sr2FeMoO6 thin films were prepared by pulsed laser deposition on different substrates. Differing from previous reports a post-deposition annealing step at low oxygen partial pressure (10-5 mbar) was introduced and enabled the fabrication of reproducible, high quality samples. According to the structural properties of the substrates the crystal structure and morphology of the thin films are modified. The close interrelation between the structural, magnetic and electronic properties of Sr2FeMoO6 was studied. A detailed evaluation of the results allowed to extract valuable information on the microscopic nature of magnetism and charge transport. Smooth films with a mean roughness of about 2 nm have been achieved, which is a pre-requisite for a possible inclusion of this material in future devices. In order to establish device-oriented sub-micron patterning as a standard technique, electron beam lithography and focussed ion beam etching facilities have been put into operation. A detailed characterisation of these systems has been performed. To determine the technological prospects of new spintronics materials, the verification of a high spin polarisation is of vital interest. A popular technique for this task is point contact Andreev reflection (PCAR). Commonly, the charge transport in a transparent metal-superconductor contact of nanometer dimensions is attributed solely to coherent transport. If this condition is not fulfilled, inelastic processes in the constriction have to be considered. PCAR has been applied to Sr2FeMoO6 and the Heusler compound Co2Cr0.6Fe0.4Al. Systematic deviations between measured spectra and the standard models of PCAR have been observed. Therefore existing approaches have been generalised, in order to include the influence of heating. With the extended model the measured data was successfully reproduced but the analysis has revealed grave implications for the determination of spin polarisation, which was found to break down completely in certain cases.

The preparation of mono- and di-substitution products of trichloro-s-triazine by replacement of chlorine by trialkylsilylphenyl

"Materials Central, Contract no. AF 33(616)-6480, Project no. 7340."

Polymer film formulations for the preparation of enteric pharmaceutical capsules

Objectives. Standard pharmaceutical capsules are designed to dissolve in the acidic environment of the stomach releasing the encapsulated contents for absorption. When release is required further along the gastrointestinal tract capsules can be coated with acid insoluble polymers to enable passage through the stomach and dissolution in the intestine. This paper describes formulations that have the potential to be used to produce two-piece hard capsules for post-gastric delivery without the requirement of an exterior coat. Methods. The formulation uses three polysaccharides: sodium alginate, hypromellose and gellan gum to provide acid insolubility and the ability to form capsules using standard industrial equipment. Key findings. The rheological profile, on cooling, of the base material, water content and thickness of the films were shown to be comparable with those of commercial capsules. The capsules remained intact for 2 h in 100 mm HCl at pH 1.2, and within 5 min of being removed from the acid and submerged in phosphate-buffered saline at pH 6.8 were ruptured. Conclusions. Selected formulations from this study have potential for use as delayed release capsules.

Psychological risk factors for chronic post-surgical pain after inguinal hernia repair surgery:a prospective cohort study.

A significant proportion of patients experience chronic post-surgical pain (CPSP) following inguinal hernia surgery. Psychological models are useful in predicting acute pain after surgery, and in predicting the transition from acute to chronic pain in non-surgical contexts. This is a prospective cohort study to investigate psychological (cognitive and emotional) risk factors for CPSP after inguinal hernia surgery. Participants were asked to complete questionnaires before surgery and 1 week and 4 months after surgery. Data collected before surgery and 1 week after surgery were used to predict pain at 4 months. Psychological risk factors assessed included anxiety, depression, fear-avoidance, activity avoidance, catastrophizing, worry about the operation, activity expectations, perceived pain control and optimism. The study included 135 participants; follow-up questionnaires were returned by 119 (88.1%) and 115 (85.2%) participants at 1 week and 4 months after surgery respectively. The incidence of CPSP (pain at 4 months) was 39.5%. After controlling for age, body mass index and surgical variables (e.g. anaesthetic, type of surgery and mesh type used), lower pre-operative optimism was an independent risk factor for CPSP at 4 months; lower pre-operative optimism and lower perceived control over pain at 1 week after surgery predicted higher pain intensity at 4 months. No emotional variables were independently predictive of CPSP. Further research should target these cognitive variables in pre-operative psychological preparation for surgery. © 2011 European Federation of International Association for the Study of Pain Chapters.

Adjusting to job relocation:relocation preparation can reduce relocation stress

This study, for the first time, examines the relationship between pre-move relocation preparation with psychological well-being to job relocation. Psychological reactions of 54 relocators were measured before and after their move. The greater the reported pre-move relocation preparation the better was the relocators' post-move mental health and job-related contentment and enthusiasm. Furthermore, pre-move relocation preparation was associated with reduced problems during the move and this, in turn, resulted in better post-move adjustment.

Impact of Vegetable Preparation Method and Taste-Test on Vegetable Preference for First Grade Children in the United States

How children rate vegetables may be influenced by the preparation method. The primary objective of this study was for first grade students to be involved in a cooking demonstration and to taste and rate vegetables raw and cooked. First grade children of two classes (N= 52: 18 boys and 34 girls (approximately half Hispanic) that had assented and had signed parental consent participated in the study. The degree of liking a particular vegetable was recorded by the students using a hedonic scale of five commonly eaten vegetables tasted first raw (pre-demonstration) and then cooked (post-demonstration). A food habit questionnaire was filled out by parents to evaluate their mealtime practices and beliefs about their child’s eating habits. Paired sample t-tests revealed significant differences in preferences for vegetables in their raw and cooked states. Several mealtime characteristics were significantly associated with children’s vegetable preferences. Parents who reported being satisfied with how often the family eats evening meals together were more likely to report that their child eats adequate vegetables for their health (p=0.026). Parents who stated that they were satisfied with their child’s eating habits were more likely to report that their child was trying new foods (p<.001). Cooking demonstrations by nutrition professionals may be an important strategy that can be used by parents and teachers to promote vegetable intake. It is important that nutrition professionals provide guidance to encourage consumption of vegetables for parents so that they can model the behavior of healthy food consumption to their children.

Selective Preparation of Semiconducting Single-Walled Carbon Nanotubes: From Fundamentals to Applications

Aligned single-walled carbon nanotubes (SWNTs) synthesized by the chemical vapor deposition (CVD) method have exceptional potential for next-generation nanoelectronics. However, there are considerable challenges in the preparation of semiconducting (s-) SWNTs with controlled properties (e.g., density, selectivity, and diameter) for their application in solving real-world problems. This dissertation describes research that aims to overcome the limitations by novel synthesis strategies and post-growth treatment. The application of as-prepared SWNTs as functional devices is also demonstrated. The dissertation includes the following parts: 1) decoupling the conflict between density and selectivity of s-SWNTs in CVD growth; 2) investigating the importance of diameter control for the selective synthesis of s-SWNTs; 3) synthesizing highly conductive SWNT thin film by thiophene-assisted CVD method; 4) eliminating metallic pathways in SWNT crossbars by gate-free electrical breakdown method; 5) enhancing the density of SWNT arrays by strain-release method; 6) studying the sensing mechanism of SWNT crossbar chemical sensors.

New dimeric supramolecular structure of mixed (phthalocyaninato)(porphyrinato)-europium(III) sandwiches : preparation and spectroscopic characteristics

The mixed double-decker Eu\[Pc(15C5)4](TPP) (1) was obtained by base-catalysed tetramerisation of 4,5-dicyanobenzo-15-crown-5 using the half-sandwich complex Eu(TPP)(acac) (acac = acetylacetonate), generated in situ, as the template. For comparative studies, the mixed triple-decker complexes Eu2\[Pc(15C5)4](TPP)2 (2) and Eu2\[Pc(15C5)4]2(TPP) (3) were also synthesised by the raise-by-one-story method. These mixed ring sandwich complexes were characterised by various spectroscopic methods. Up to four one-electron oxidations and two one-electron reductions were revealed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). As shown by electronic absorption and infrared spectroscopy, supramolecular dimers (SM1 and SM3) were formed from the corresponding double-decker 1 and triple-decker 3 in the presence of potassium ions in MeOH/CHCl3.