Laurdan Spectrum Decomposition as a Tool for the Analysis of Surface Bilayer Structure and Polarity: a Study with DMPG, Peptides and Cholesterol

The highly hydrophobic fluorophore Laurdan (6-dodecanoyl-2-(dimethylaminonaphthalene)) has been widely used as a fluorescent probe to monitor lipid membranes. Actually, it monitors the structure and polarity of the bilayer surface, where its fluorescent moiety is supposed to reside. The present paper discusses the high sensitivity of Laurdan fluorescence through the decomposition of its emission spectrum into two Gaussian bands, which correspond to emissions from two different excited states, one more solvent relaxed than the other. It will be shown that the analysis of the area fraction of each band is more sensitive to bilayer structural changes than the largely used parameter called Generalized Polarization, possibly because the latter does not completely separate the fluorescence emission from the two different excited states of Laurdan. Moreover, it will be shown that this decomposition should be done with the spectrum as a function of energy, and not wavelength. Due to the presence of the two emission bands in Laurdan spectrum, fluorescence anisotropy should be measured around 480 nm, to be able to monitor the fluorescence emission from one excited state only, the solvent relaxed state. Laurdan will be used to monitor the complex structure of the anionic phospholipid DMPG (dimyristoyl phosphatidylglycerol) at different ionic strengths, and the alterations caused on gel and fluid membranes due to the interaction of cationic peptides and cholesterol. Analyzing both the emission spectrum decomposition and anisotropy it was possible to distinguish between effects on the packing and on the hydration of the lipid membrane surface. It could be clearly detected that a more potent analog of the melanotropic hormone alpha-MSH (Ac-Ser(1)-Tyr(2)-Ser(3)-Met(4)-Glu(5)-His(6)-Phe(7)-Arg(8)-Trp(9)-Gly(10)-Lys(11)-Pro(12)-Val(13)-NH(2)) was more effective in rigidifying the bilayer surface of fluid membranes than the hormone, though the hormone significantly decreases the bilayer surface hydration.

Polarity-Dependent Transcranial Direct Current Stimulation Effects on Central Auditory Processing

Given the polarity dependent effects of transcranial direct current stimulation (tDCS) in facilitating or inhibiting neuronal processing, and tDCS effects on pitch perception, we tested the effects of tDCS on temporal aspects of auditory processing. We aimed to change baseline activity of the auditory cortex using tDCS as to modulate temporal aspects of auditory processing in healthy subjects without hearing impairment. Eleven subjects received 2mA bilateral anodal, cathodal and sham tDCS over auditory cortex in a randomized and counterbalanced order. Subjects were evaluated by the Random Gap Detection Test (RGDT), a test measuring temporal processing abilities in the auditory domain, before and during the stimulation. Statistical analysis revealed a significant interaction effect of time vs. tDCS condition for 4000 Hz and for clicks. Post-hoc tests showed significant differences according to stimulation polarity on RGDT performance: anodal improved 22.5% and cathodal decreased 54.5% subjects' performance, as compared to baseline. For clicks, anodal also increased performance in 29.4% when compared to baseline. tDCS presented polarity-dependent effects on the activity of the auditory cortex, which results in a positive or negative impact in a temporal resolution task performance. These results encourage further studies exploring tDCS in central auditory processing disorders.

Probing the dependence of the properties of cellulose acetates and their films on the degree of biopolymer substitution: use of solvatochromic indicators and thermal analysis

Although cellulose acetates, CAs, are extensively employed there is scant information about the systematic dependence of their properties on their degree of substitution, DS; this is the subject of the present work. Nine CAs samples, DS from 0.83 to 3.0 were synthesized; their films were prepared. The following solvatochromic probes have been employed in order to determine the empirical polarity, E (T)(33); ""acidity, alpha""; ""basicity, beta"", and ""dipolarity/polarizability, pi*"" of the casted films: 2,6-dichloro-4-(2,4,6-triphenyl-pyridinium-1-yl) phenolate, WB; 4-nitroaniline; 4-nitroanisole; 4-nitro-N,N-dimethylaniline; 2,6-diphenyl-4-(2,4,6-triphenyl-pyridinium-1-yl)phenolate, RB. Additionally, two systems, ethanol plus ethyl acetate (EtOH-EtAc), and cellulose plus cellulose triacetate, CTA, were employed as models for CAs of different DS. Regarding the model systems, the following was observed: (i) For EtOH-EtAc, the dependence of all solvatochromic parameters on the ""equivalent-DS"" of the binary mixture was non-linear because of preferential solvation; (ii) The dependence of E (T)(33) on equivalent DS of the cellulose-CTA films is linear, but the slope is smaller than that of the corresponding plot for CAs. This is attributed to the more efficient hydrogen bonding in the model system, a conclusion corroborated by IR measurements. The dependence of solvatochromic parameters of CAs on their DS is described by the simple equations; a consequence of the substitution of the OH by the ester group. The thermal properties of bulk CAs samples were investigated by DSC and TGA; their dependence on DS is described by simple equations. The relevance of these data to the processing and applications of CAs is briefly discussed.

Development of a fast capillary electrophoresis method for the determination of propranolol-Total analysis time reduction strategies

The aim of this study was to develop a fast capillary electrophoresis method for the determination of propranolol in pharmaceutical preparations. In the method development the pH and constituents of the background electrolyte were selected using the effective mobility versus pH curves. Benzylamine was used as the internal standard. The background electrolyte was composed of 60 mmol L(-1) tris(hydroxymethyl)aminomethane and 30 mmol L(-1) 2-hydroxyisobutyric acid,at pH 8.1. Separation was conducted in a fused-silica capillary (32 cm total length and 8.5 cm effective length, 50 mu m I.D.) with a short-end injection configuration and direct UV detection at 214 nm. The run time was only 14 s. Three different strategies were studied in order to develop a fast CE method with low total analysis time for propranolol analysis: low flush time (Lflush) 35 runs/h, without flush (Wflush) 52 runs/h, and Invert (switched polarity) 45 runs/h. Since the three strategies developed are statistically equivalent, Mush was selected due to the higher analytical frequency in comparison with the other methods. A few figures of merit of the proposed method include: good linearity (R(2) > 0.9999); limit of detection of 0.5 mg L(-1): inter-day precision better than 1.03% (n = 9) and recovery in the range of 95.1-104.5%. (C) 2009 Elsevier B.V. All rights reserved.

Digital subtraction radiographic analysis of the combination of bioabsorbable membrane and bovine morphogenetic protein pool in human periodontal infrabony defects

OBJECTIVES: This study assessed the bone density gain and its relationship with the periodontal clinical parameters in a case series of a regenerative therapy procedure. MATERIAL AND METHODS: Using a split-mouth study design, 10 pairs of infrabony defects from 15 patients were treated with a pool of bovine bone morphogenetic proteins associated with collagen membrane (test sites) or collagen membrane only (control sites). The periodontal healing was clinically and radiographically monitored for six months. Standardized pre-surgical and 6-month postoperative radiographs were digitized for digital subtraction analysis, which showed relative bone density gain in both groups of 0.034 ± 0.423 and 0.105 ± 0.423 in the test and control group, respectively (p>0.05). RESULTS: As regards the area size of bone density change, the influence of the therapy was detected in 2.5 mm² in the test group and 2 mm² in the control group (p>0.05). Additionally, no correlation was observed between the favorable clinical results and the bone density gain measured by digital subtraction radiography (p>0.05). CONCLUSIONS: The findings of this study suggest that the clinical benefit of the regenerative therapy observed did not come with significant bone density gains. Long-term evaluation may lead to a different conclusions.

Isolation of Pseudomonas aeruginosa strains from dental office environments and units in Barretos, state of São Paulo, Brazil, and analysis of their susceptibility to antimicrobial drugs

A wide variety of opportunistic pathogens has been detected in the tubing supplying water to odontological equipment, in special in the biofilm lining of these tubes. Among these pathogens, Pseudomonas aeruginosa, one of the leading causes of nosocomial infections, is frequently found in water lines supplying dental units. In the present work, 160 samples of water, and 200 fomite samples from forty dental units were collected in the city of Barretos, State of São Paulo, Brazil and evaluated between January and July, 2005. Seventy-six P. aeruginosa strains, isolated from the dental environment (5 strains) and water system (71 strains), were tested for susceptibility to six antimicrobial drugs most frequently used against P. aeruginosa infections. Susceptibility to ciprofloxacin, followed by meropenem was the predominant profile. The need for effective means of reducing the microbial burden within dental unit water lines is emphasized, and the risk of exposure and cross-infection in dental practice, in special when caused by opportunistic pathogens like P. aeruginosa, are highlighted.

Analysis of TMJ vibration sounds before and after use of two types of occlusal splints

Temporomandibular joint (TMJ) sounds are important and common physical signs of temporomandibular disorders (TMD). The aim of this study was to evaluate the influence of the effect of the use of occlusal bite splints (stabilizing and repositioning) on the sounds produced in the TMJ, by means of the electrovibratography (EVG). Thirty-one patients with TMD from the Dental School of Ribeirão Preto, University of São Paulo, Brazil were selected for this study. Group 1 (n=23) wore stabilizing bite splints and Group 2 (n=8) used anterior repositioning splints. Before and after treatment with occlusal splints both groups were analyzed using the SonoPAK Q/S recording system (BioResearch System, Inc.). The treatments with stabilizing bite splints were satisfactory, since they reduced the total amount of the sound energies (p<0.05), but the use of anterior repositioning splints for no more than 4 weeks produced significantly better results (p<0.01). The total amount of vibration energy involved in the vibrating movements of the TMJ showed significant improvement using anterior repositioning splints.

Adhesion of an endodontic sealer to dentin and gutta-percha: shear and push-out bond strength measurements and SEM analysis

The use of an adequate method for evaluation of the adhesion of root canal filling materials provides more reliable results to allow comparison of the materials and substantiate their clinical choice. The aims of this study were to compare the shear bond strength (SBS) test and push-out test for evaluation of the adhesion of an epoxy-based endodontic sealer (AH Plus) to dentin and gutta-percha, and to assess the failure modes on the debonded surfaces by means of scanning electron microscopy (SEM). Three groups were established (n=7): in group 1, root cylinders obtained from human canines were embedded in acrylic resin and had their canals prepared and filled with sealer; in group 2, longitudinal sections of dentin cylinders were embedded in resin with the canal surface smoothed and turned upwards; in group 3, gutta-percha cylinders were embedded in resin. Polyethylene tubes filled with sealer were positioned on the polished surface of the specimens (groups 2 and 3). The push-out test (group 1) and the SBS test (groups 2 and 3) were performed in an Instron universal testing machine running at crosshead speed of 1 mm/min. Means (±SD) in MPa were: G1 (8.8±1.13), G2 (5.9±1.05) and G3 (3.8±0.55). Statistical analysis by ANOVA and Student's t-test (a=0.05) revealed statistically significant differences (p<0.01) among the groups. SEM analysis showed a predominance of adhesive and mixed failures of AH Plus sealer. The tested surface affected significantly the results with the sealer reaching higher bond strength to dentin than to gutta-percha with the SBS test. The comparison of the employed methodologies showed that the SBS test produced significantly lower bond strength values than the push-out test, was skilful in determining the adhesion of AH Plus sealer to dentin and gutta-percha, and required specimens that could be easily prepared for SEM, presenting as a viable alternative for further experiments.

Morphological analysis of glass, carbon and glass/carbon fiber posts and bonding to self or dual-cured resin luting agents

OBJECTIVE: The aim of this study was to evaluate the morphology of glass (GF), carbon (CF) and glass/carbon (G/CF) fiber posts and their bond strength to self or dual-cured resin luting agents. MATERIAL AND METHODS: Morphological analysis of each post type was conducted under scanning electron microscopy (SEM). Bond strength was evaluated by microtensile test after bisecting the posts and re-bonding the two halves with the luting agents. Data were subjected to two-way ANOVA and Tukey's test (α=0.05). Failure modes were evaluated under optical microscopy and SEM. RESULTS: GF presented wider fibers and higher amount of matrix than CF, and G/CF presented carbon fibers surrounded by glass fibers, and both involved by matrix. For CF and GF, the dual-cured material presented significantly higher (p<0.05) bond strength than the self-cured agent. For the dual agent, CF presented similar bond strength to GF (p>0.05), but higher than that of G/CF (p<0.05). For the self-cured agent, no significant differences (p>0.05) were detected, irrespective of the post type. For GF and G/CF, all failures were considered mixed, while a predominance of adhesive failures was detected for CF. CONCLUSION: The bonding between fiber posts and luting agents was affected by the type of fibers and polymerization mode of the cement. When no surface treatment of the post is performed, the bonding between glass fiber post and dual-cured agent seems to be more reliable.

Influence of cervical preflaring on determinationof apical file size in mandibular molars: SEM analysis

This study investigated the influence of cervical preflaring with different rotary instruments on determination of the initial apical file (IAF) in mesiobuccal roots of mandibular molars. Fifty human mandibular molars whose mesial roots presented two clearly separated apical foramens (mesiobuccal and mesiolingual) were used. After standard access opening and removal of pulp tissue, the working length (WL) was determined at 1 mm short of the root apex. Five groups (n=10) were formed at random, according to the type of instrument used for cervical preflaring. In group 1, the size of the IAF was determined without preflaring of the cervical and middle root canal thirds. In groups 2 to 5, preflaring was performed with Gates-Glidden drills, ProTaper instruments, EndoFlare instruments and LA Axxes burs, respectively. Canals were sized manually with K-files, starting with size 08 K-files, inserted passively up to the WL. File sizes were increased until a binding sensation was felt at the WL and the size of the file was recorded. The instrument corresponding to the IAF was fixed into the canal at the WL with methylcyanoacrylate. The teeth were then sectioned transversally 1 mm short of the apex, with the IAF in position. Cross-sections of the WL region were examined under scanning electron microscopy and the discrepancies between canal diameter and the diameter of IAF were calculated using the tool "rule" (FEG) of the microscope's proprietary software. The measurements (µm) were analyzed statistically by Kruskal-Wallis and Dunn's tests at 5% significance level. There were statistically significant differences among the groups (p<0.05). The non-flared group had the greatest discrepancy (125.30 ± 51.54) and differed significantly from all flared groups (p<0.05). Cervical preflaring with LA Axxess burs produced the least discrepancies (55.10 ± 48.31), followed by EndoFlare instruments (68.20 ± 42.44), Gattes Glidden drills (68.90 ± 42.46) and ProTaper files (77.40 ± 73.19). However, no significant differences (p>0.05) were found among the rotary instruments. In conclusion, cervical preflaring improved IAF fitting to the canals at the WL in mesiobuccal roots of maxillary first molars. The rotary instruments evaluated in this study did not differ from each other regarding the discrepancies produced between the IAF size and canal diameter at the WL.

Ex vivo analysis of root canal cleaning using Endo-PTC associated to NaOCl and different irrigant solutions

The aim of this study was to assess qualitatively, by means of SEM images, the cleaning of the dentin walls of root canals after chemical-surgical preparation using Endo-PTC cream with 0.5% and 1% sodium hypochlorite and different final irrigating solutions. Seventy-two single-rooted human teeth were divided into eight groups and prepared using Endo-PTC cream with sodium hypochlorite (NaOCl) at different concentrations, and irrigated with NaOCl at different concentrations. Final irrigation was performed with either EDTA-T or EDTA-C. The best results were obtained with Group 1, followed by Groups 5, 2, 7, 8, 3, 6 and 4. We can conclude that the use of 0.5% NaOCl during instrumentation and final flush of the root canals was more efficient in cleaning than was 1% sodium hypochlorite. EDTA-T was more efficient in removing smear layer than EDTA-C, and the cervical third presented better cleaning of the root canal walls than did the middle third, which showed cleaner dentin walls than the apical third.

Coronal and apical leakage analysis of two different root canal obturation systems

This study compared the coronal and apical leakage of AH Plus with gutta-percha to that of Epiphany with Resilon. Twenty-four single rooted teeth were instrumented and divided into 2 groups according to the solutions for smear layer removal and the obturation materials employed: Group A - 17% EDTA-T and AH Plus with gutta-percha; Group B - primer and Epiphany with Resilon. The Group B specimens were light-cured in the coronal area for 20 s. The external root surfaces were covered with a double layer of ethyl cyanoacrylate, except for the apical foramen and the cavity access. The teeth were immersed in 0.5% methylene blue for 48 h. The specimens were rinsed, dried and axially split for dye penetration measurement with the ImageLab 2.3 software. The t-test showed no significant differences for coronal leakage between the groups, but there were significant differences for apical leakage between the groups (P < 0.05). AH Plus with gutta-percha and Epiphany with Resilon provided the same coronal seal, whereas Epiphany with Resilon provided the best apical seal.

Analysis of contamination of endodontic absorbent paper points

PURPOSE: The aim of this study was to assess the contamination status of endodontic absorbent paper points from sterilized or not sterilized commercial packs, as well as paper points exposed to the dental office environment. METHODS: Twenty absorbent paper points were evaluated for contamination status packed under different conditions: commercial/sterilized pack, commercial/non-sterilized pack, exposed to the clinical environment, and intentionally contaminated (positive control). Contamination was determined qualitatively and quantitatively by aerobiosis, capnophilic growth, and pour plate. The Petri dishes were analyzed with a colony counter, and the results were expressed as colony-forming units. The data were analyzed by Kruskal-Wallis test (α=0.05). RESULTS: No difference in colony-forming units was found among the groups of endodontic absorbent paper points. All groups were contaminated by fungi and bacteria. CONCLUSION: It can be concluded that the sterilization of absorbent endodontic paper points before clinical use should be recommended regardless of commercial presentation

Analysis of the periodontal status of patients with mandibular-bonded retainers

PURPOSE: This clinical study evaluated the periodontal status of patients with bonded retainers as compared to a non-treated control group. METHODS: Forty dental students were included in the sample and divided into the following two groups: 1) a test group of 20 subjects that, after orthodontic treatment, have been bonded retainer users for at least 2 years and 2) a control group of 20 patients that never experienced orthodontic treatment nor used any bonded retainer. The region associated with the retainer in the test group and the lower canine-to-canine region in the control group were examined according to the following clinical parameters: plaque index (PI), bleeding on probing (BOP), gingival recession (GR), clinical attachment level (CAL) and probing depth (PD). RESULTS: No differences were observed for GR or BOP (P>0.05). In contrast, the test group showed higher values of CAL and PD at proximal sites when compared to controls (P<0.05). In addition, IP was significantly increased at buccal and lingual sites (P<0.05). CONCLUSION: The placement of orthodontic bonded retainers negatively affected periodontal health, resulting in increased PI, PD and CAL.

Analysis of the stimulated whole saliva in overweight and obese school children

OBJECTIVE: To determine if some stimulated whole saliva parameters are influenced by an increase of Body Mass Index. METHODS: Controlled cross-sectional study involving 90 school children of both genders between 7 and 10 years of age, from Bragança Paulista - SP. Three groups were formed: overweight, obese and control. Body Mass Index and diet intake by the Food Register method were evaluated. The salivary pH, flow rate, buffer capacity, protein, phosphate, calcium, fluoride, total and free sialic acid, and peroxidase activity were determined. RESULTS: The overweight and obese groups showed greater energy and lipid intake (P< 0.001) than the control group. There was no difference in the saliva flow rate between groups, however only the control group showed a mean value considered normal. In the overweight and obese groups a decrease in both the concentration of phosphate (P< 0.001) and peroxidase activity (P<0.001) was observed. In the obese group an increase in the concentrations of free sialic acid (P= 0.004) and protein (P= 0.003) occurred. CONCLUSION: Overweight and obese children show alterations in the concentrations of phosphate, free sialic acid and proteins, and in the peroxidase activity that are favorable conditions for dental caries.