Observation of Azimuth-Dependent Suppression of Hadron Pairs in Electron Scattering off Nuclei.

We present the first measurement of dihadron angular correlations in electron-nucleus scattering. The data were taken with the CLAS detector and a 5.0 GeV electron beam incident on deuterium, carbon, iron, and lead targets. Relative to deuterium, the nuclear yields of charged-pion pairs show a strong suppression for azimuthally opposite pairs, no suppression for azimuthally nearby pairs, and an enhancement of pairs with large invariant mass. These effects grow with increased nuclear size. The data are qualitatively described by the gibuu model, which suggests that hadrons form near the nuclear surface and undergo multiple scattering in nuclei.These results show that angular correlation studies can open a new way to elucidate how hadrons form and interact inside nuclei.

Plant species effects on soil nutrients and chemistry in arid ecological zones.

The presence of vegetation strongly influences ecosystem function by controlling the distribution and transformation of nutrients across the landscape. The magnitude of vegetation effects on soil chemistry is largely dependent on the plant species and the background soil chemical properties of the site, but has not been well quantified along vegetation transects in the Great Basin. We studied the effects of plant canopy cover on soil chemistry within five different ecological zones, subalpine, montane, pinyon-juniper, sage/Mojave transition, and desert shrub, in the Great Basin of Nevada all with similar underlying geology. Although plant species differed in their effects on soil chemistry, the desert shrubs Sarcobatus vermiculatus, Atriplex spp., Coleogyne ramosissima, and Larrea tridentata typically exerted the most influence on soil chemistry, especially amounts of K(+) and total nitrogen, beneath their canopies. However, the extent to which vegetation affected soil nutrient status in any given location was not only highly dependent on the species present, and presumably the nutrient requirements and cycling patterns of the plant species, but also on the background soil characteristics (e.g., parent material, weathering rates, leaching) where plant species occurred. The results of this study indicate that the presence or absence of a plant species, especially desert shrubs, could significantly alter soil chemistry and subsequently ecosystem biogeochemistry and function.

Surgical excision versus imiquimod 5% cream for nodular and superficial basal-cell carcinoma (SINS): a multicentre, non-inferiority, randomised controlled trial.

BACKGROUND: Basal-cell carcinoma is the most common form of skin cancer and its incidence is increasing worldwide. We aimed to assess the effectiveness of imiquimod cream versus surgical excision in patients with low-risk basal-cell carcinoma. METHODS: We did a multicentre, parallel-group, pragmatic, non-inferiority, randomised controlled trial at 12 centres in the UK, in which patients were recruited between June 19, 2003, and Feb 22, 2007, with 3 year follow-up from June 26, 2006, to May 26, 2010. Participants of any age were eligible if they had histologically confirmed primary nodular or superficial basal-cell carcinoma at low-risk sites. We excluded patients with morphoeic or recurrent basal-cell carcinoma and those with Gorlin syndrome. Participants were randomly assigned (1:1) via computer-generated blocked randomisation, stratified by centre and tumour type, to receive either imiquimod 5% cream once daily for 6 weeks (superficial) or 12 weeks (nodular), or surgical excision with a 4 mm margin. The randomisation sequence was concealed from study investigators. Because of the nature of the interventions, masking of participants was not possible and masking of outcome assessors was only partly possible. The trial statistician was masked to allocation until all analyses had been done. The primary outcome was the proportion of participants with clinical success, defined as absence of initial treatment failure or signs of recurrence at 3 years from start of treatment. We used a prespecified non-inferiority margin of a relative risk (RR) of 0.87. Analysis was by a modified intention-to-treat population and per protocol. This study is registered as an International Standard Randomised Controlled Trial (ISRCTN48755084), and with ClinicalTrials.gov, number NCT00066872. FINDINGS: 501 participants were randomly assigned to the imiquimod group (n=254) or the surgical excision group (n=247). At year 3, 401 (80%) patients were included in the modified intention-to-treat group. At 3 years, 178 (84%) of 213 participants in the imiquimod group were treated successfully compared with 185 (98%) of 188 participants in the surgery group (RR 0.84, 98% CI 0.78-0.91; p<0.0001). No clear difference was noted between groups in patient-assessed cosmetic outcomes. The most common adverse events were itching (211 patients in the imiquimod group vs 129 in the surgery group) and weeping (160 vs 81). We recorded serious adverse events in 99 (40%) of 249 participants in the imiquimod group and 97 (42%) of 229 in the surgery group had serious adverse events, but none were regarded as related to treatment. 12 (5%) participants in the imiquimod group withdrew because of adverse events compared with four (2%) in the surgery group. INTERPRETATION: Imiquimod was inferior to surgery according to our predefined non-inferiority criterion. Although excisional surgery remains the best treatment for low-risk basal-cell carcinoma, imiquimod cream might still be a useful treatment option for small low-risk superficial or nodular basal-cell carcinoma dependent on factors such as patient preference, size and site of the lesion, and whether the patient has more than one lesion. FUNDING: Cancer Research UK.

Prolonged suppression of ecosystem carbon dioxide uptake after an anomalously warm year.

Terrestrial ecosystems control carbon dioxide fluxes to and from the atmosphere through photosynthesis and respiration, a balance between net primary productivity and heterotrophic respiration, that determines whether an ecosystem is sequestering carbon or releasing it to the atmosphere. Global and site-specific data sets have demonstrated that climate and climate variability influence biogeochemical processes that determine net ecosystem carbon dioxide exchange (NEE) at multiple timescales. Experimental data necessary to quantify impacts of a single climate variable, such as temperature anomalies, on NEE and carbon sequestration of ecosystems at interannual timescales have been lacking. This derives from an inability of field studies to avoid the confounding effects of natural intra-annual and interannual variability in temperature and precipitation. Here we present results from a four-year study using replicate 12,000-kg intact tallgrass prairie monoliths located in four 184-m(3) enclosed lysimeters. We exposed 6 of 12 monoliths to an anomalously warm year in the second year of the study and continuously quantified rates of ecosystem processes, including NEE. We find that warming decreases NEE in both the extreme year and the following year by inducing drought that suppresses net primary productivity in the extreme year and by stimulating heterotrophic respiration of soil biota in the subsequent year. Our data indicate that two years are required for NEE in the previously warmed experimental ecosystems to recover to levels measured in the control ecosystems. This time lag caused net ecosystem carbon sequestration in previously warmed ecosystems to be decreased threefold over the study period, compared with control ecosystems. Our findings suggest that more frequent anomalously warm years, a possible consequence of increasing anthropogenic carbon dioxide levels, may lead to a sustained decrease in carbon dioxide uptake by terrestrial ecosystems.

Concurrent and lagged impacts of an anomalously warm year on autotrophic and heterotrophic components of soil respiration: a deconvolution analysis.

*Partitioning soil respiration into autotrophic (R(A)) and heterotrophic (R(H)) components is critical for understanding their differential responses to climate warming. *Here, we used a deconvolution analysis to partition soil respiration in a pulse warming experiment. We first conducted a sensitivity analysis to determine which parameters can be identified by soil respiration data. A Markov chain Monte Carlo technique was then used to optimize those identifiable parameters in a terrestrial ecosystem model. Finally, the optimized parameters were employed to quantify R(A) and R(H) in a forward analysis. *Our results displayed that more than one-half of parameters were constrained by daily soil respiration data. The optimized model simulation showed that warming stimulated R(H) and had little effect on R(A) in the first 2 months, but decreased both R(H) and R(A) during the remainder of the treatment and post-treatment years. Clipping of above-ground biomass stimulated the warming effect on R(H) but not on R(A). Overall, warming decreased R(A) and R(H) significantly, by 28.9% and 24.9%, respectively, during the treatment year and by 27.3% and 33.3%, respectively, during the post-treatment year, largely as a result of decreased canopy greenness and biomass. *Lagged effects of climate anomalies on soil respiration and its components are important in assessing terrestrial carbon cycle feedbacks to climate warming.

Atmospheric mercury exchange with a tallgrass prairie ecosystem housed in mesocosms.

This study focused on characterizing air-surface mercury Hg exchange for individual surfaces (soil, litter-covered soil and plant shoots) and ecosystem-level flux associated with tallgrass prairie ecosystems housed inside large mesocosms over three years. The major objectives of this project were to determine if individual surface fluxes could be combined to predict ecosystem-level exchange and if this low-Hg containing ecosystem was a net source or sink for atmospheric Hg. Data collected in the field were used to validate fluxes obtained in the mesocosm setting. Because of the controlled experimental design and ease of access to the mesocosms, data collected allowed for assessment of factors controlling flux and comparison of models developed for soil Hg flux versus environmental conditions at different temporal resolution (hourly, daily and monthly). Evaluation of hourly data showed that relationships between soil Hg flux and environmental conditions changed over time, and that there were interactions between parameters controlling exchange. Data analyses demonstrated that to estimate soil flux over broad temporal scales (e.g. annual flux) coarse-resolution data (monthly averages) are needed. Plant foliage was a sink for atmospheric Hg with uptake influenced by plant functional type and age. Individual system component fluxes (bare soil and plant) could not be directly combined to predict the measured whole system flux (soil, litter and plant). Emissions of Hg from vegetated and litter-covered soil were lower than fluxes from adjacent bare soil and the difference between the two was seasonally dependent and greatest when canopy coverage was greatest. Thus, an index of plant canopy development (canopy greenness) was used to model Hg flux from vegetated soil. Accounting for ecosystem Hg inputs (precipitation, direct plant uptake of atmospheric Hg) and modeled net exchange between litter-and-plant covered soils, the tallgrass prairie was found to be a net annual sink of atmospheric Hg.

Surgery Versus 5% Imiquimod for Nodular and Superficial Basal Cell Carcinoma: 5-Year Results of the SINS Randomized Controlled Trial.

We previously reported modest clinical 3-year benefit for topical imiquimod compared with surgery for superficial or nodular basal cell carcinoma at low-risk sites in our noninferiority randomized controlled SINS trial. Here we report 5-year data. Participants were randomized to imiquimod 5% cream once daily (superficial basal cell carcinoma, 6 weeks; nodular basal cell carcinoma, 12 weeks) or excisional surgery (4-mm margin). The primary outcome was clinical absence of initial failure or signs of recurrence at the 3-year dermatology review. Five-year success was defined as 3-year success plus absence of recurrences identified through hospital, histopathology, and general practitioner records. Of 501 participants randomized, 401 contributed to the modified intention-to-treat analyses at year 3 (primary outcome), 383 (96%) of whom had data at year 5. Five-year success rates for imiquimod were 82.5% (170/206) compared with 97.7% (173/177) for surgery (relative risk of imiquimod success = 0.84, 95% confidence interval = 0.77-0.91, P < 0.001). These were comparable to year 3 success rates of 83.6% (178/213) and 98.4% (185/188) for imiquimod and surgery, respectively. Most imiquimod treatment failures occurred in year 1. Although surgery is clearly superior to imiquimod, this study shows sustained benefit for lesions that respond early to topical imiquimod.

Nocturia Work Productivity and Activity Impairment Compared with Other Common Chronic Diseases.

OBJECTIVES: The International Continence Society defines nocturia as the need to void one or more times during the night, with each of the voids preceded and followed by sleep. The chronic sleep disturbance and sleep deprivation experienced by patients with nocturia affects quality of life, compromising both mental and physical well-being. This paper aims to characterise the burden of nocturia by comparing published data from patients with nocturia with data from patients with any of 12 other common chronic conditions, specifically focusing on its impact on work productivity and activity impairment, as measured by the instrument of the same name (WPAI). METHODS: A systematic literature review of multiple data sources identified evaluable studies for inclusion in the analysis. Study eligibility criteria included use of the WPAI instrument in patients with one of a predefined list of chronic conditions. We assessed the quality of each included study using the Newcastle-Ottawa scale and extracted basic study information, work and activity impairment data. To assess how work and activity impairment from nocturia compares with impairment from other common chronic diseases, we conducted two data syntheses (pooled and unpooled). RESULTS: The number of evaluable studies and the range of overall work productivity impairment reported, respectively, were as follows: nocturia (3; 14-39 %), overactive bladder (5; 11-41 %), irritable bowel syndrome/constipation (14; 21-51 %), gastroesophageal reflux disease (GERD) (13; 6-42 %), asthma/allergies (11; 6-40 %), chronic obstructive pulmonary disease (COPD) (7; 19-42 %), sleep problems (3; 12-37 %), arthritis (13; 21-69 %), pain (9; 29-64 %), depression (4; 15-43 %) and gout (2; 20-37 %). CONCLUSIONS: The overall work productivity impairment as a result of nocturia is substantial and was found to be similar to impairment observed as a result of several other more frequently researched common chronic diseases. Greater awareness of the burden of nocturia, a highly bothersome and prevalent condition, will help policy makers and healthcare decision makers provide appropriate management of nocturia.

Are cost benefits of anticoagulation for stroke prevention in atrial fibrillation underestimated?

BACKGROUND AND PURPOSE: Stroke outcomes in patients with atrial fibrillation (AF) tend to be worse than those in patients without AF. The objective of this study was to evaluate whether the cost benefits of anticoagulation for stroke prevention in AF may currently be underestimated by existing economic models that do not distinguish between different stroke outcomes. METHODS: A literature review was conducted in 3 areas: (1) studies comparing stroke outcomes in AF and non-AF patients; (2) studies providing long-term cost of stroke estimates; and (3) studies modeling the cost-effectiveness of anticoagulation with a vitamin K antagonist (eg, warfarin) in AF patients. RESULTS: There is considerable evidence that stroke in AF patients has a worse outcome than in patients without AF, including higher mortality, severity, and recurrence rates, and greater functional impairment and dependency. Estimates of the long-term cost of stroke of different severities were between US 24,991 dollars for a mild stroke over 5 years and US 142,251 dollars for a major ischemic stroke over a lifetime (2004 prices). The cost of a severe ischemic stroke may typically be 3-times that of mild stroke. However, cost-effectiveness models for anticoagulation in patients with AF have used average (not AF-specific) cost-of-stroke data, and most have used stroke severity distributions derived from clinical trials, which may differ from those in clinical practice. CONCLUSIONS: Existing economic models underestimate the cost benefits of anticoagulation for stroke prevention because they do not adjust for poorer outcomes associated with cardioembolic strokes.

Cost effectiveness of rosuvastatin in treating patients to low-density lipoprotein cholesterol goals compared with atorvastatin, pravastatin, and simvastatin (a US Analysis of the STELLAR Trial).

Statin therapy decreases low-density lipoprotein cholesterol levels and the risk of coronary heart disease but has a considerable short-term effect on health care budgets. The cost effectiveness of rosuvastatin (Crestor) has been compared with those of atorvastatin, pravastatin, and simvastatin in lowering low-density lipoprotein cholesterol levels and achieving National Cholesterol Education Program Adult Treatment Panel III low-density lipoprotein cholesterol goals. The analysis was conducted from the perspective of health care payers in the United States. Clinical data were obtained from the Statin Therapies for Elevated Lipid Levels Compared Across Doses to Rosuvastatin (STELLAR) trial. Drug costs were based on wholesale acquisition costs. Cost effectiveness was assessed with the net monetary benefit approach and a 1-year time horizon. Rosuvastatin at 10 mg, the recommended starting dose, was the most cost-effective statin over a large range of "willingness-to-pay" values for a unit of clinical effect (i.e., a 1% decrease in low-density lipoprotein cholesterol or a patient achieving the goal).

Gonadotropin subunit messenger RNA concentrations after blockade of gonadotropin-releasing hormone action: testosterone selectively increases follicle-stimulating hormone beta-subunit messenger RNA by posttranscriptional mechanisms.

Regulation of gonadotropin gene expression by sex steroids may occur via direct effects on the pituitary and/or indirect effects of steroids mediated through hypothalamic GnRH. We aimed to define the effects of testosterone (T) on alpha, LH beta, and FSH beta mRNA expression in the male rat after blockade of GnRH action on the gonadotrope. A water-soluble GnRH antagonist was administered iv to castrate male rats (increased endogenous GnRH secretion) and to castrate T-replaced rats in which gonadotropin subunit mRNAs had been increased by prior treatment with exogenous GnRH pulses. In castrate male rats, GnRH antagonist resulted in a fall in all three subunit mRNAs. Alpha and LH beta declined at slower rates (half-disappearance after 50 and 65 h, respectively), and neither fell to values present in intact rats over 84 h. In contrast, FSH beta mRNA declined more rapidly, with a half-disappearance after 20 h. In castrate T-replaced rats, alpha mRNA declined at a rate similar to that in castrates (half-disappearance after 50 h). LH beta declined more slowly, and the rate of FSH beta decline was markedly prolonged in the presence of T (half-disappearance time increased from 20 to 50 h). These results suggest that T exerts direct effects on FSH beta transcription or mRNA stability which are independent of GnRH action. To assess these possibilities, a long-acting GnRH antagonist (Detirelix) was administered to castrate male rats, which also received T or sham implants 4 days after castration. FSH beta mRNA levels fell during the 4 days of Detirelix alone, but the addition of T on day 4 resulted in a 2-fold rise in FSH beta mRNA, restoring FSH beta mRNA to levels present in intact rats. Serum FSH closely paralleled FSH beta mRNA concentrations. Alpha mRNA was reduced by 25%, and LH beta mRNA concentrations were unchanged in the presence of T. The rate of alpha mRNA transcription was markedly reduced and that of LH beta tended to fall in T-treated rats, but T had no significant effect on the FSH beta transcription rate. Thus, the action of T to increase concentrations of cytosolic FSH beta mRNA appears to be exerted at a posttranscriptional level, possibly via effects of T on FSH beta mRNA stability. This may represent a mechanism by which T can effect differential regulation of gonadotropin subunit mRNA concentrations.

Differential regulation of gonadotropin subunit gene expression by gonadotropin-releasing hormone pulse amplitude in female rats.

The role of GnRH in regulating gonadotropin subunit gene expression was examined in adult female rats. Animals were ovariectomized, estradiol implants inserted sc, and jugular cannulae placed into the right atria. On the next day, animals were given GnRH pulses (saline to controls) every 30 min for up to 48 h and alpha, LH beta, and FSH beta mRNA levels measured by hybridization to cDNA probes. To determine the effects of GnRH treatment duration, rats received GnRH pulses (25 ng at 30-min intervals) for 6, 12, 24, and 48 h. FSH beta mRNA was increased (by 92%) after 6 h of pulses and remained elevated through 48 h. alpha mRNA was not increased until 12 h (27% increase) and rose further (57%) by 48 h. LH beta mRNA levels were only transiently increased at 12 h (67%) and values were not different from saline controls after 24 or 48 h. To examine whether the rise in serum PRL which is characteristic of the ovariectomized-estradiol animal model was responsible for the decrease in LH beta mRNA responsiveness to GnRH over longer durations, studies were repeated in bromocriptine-treated animals (0.6 mg sc, twice daily). The results showed similar response patterns for all three subunit mRNAs including the decrease in LH beta after 48 h. A third experiment examined the effect of varying GnRH pulse amplitude (0.5-250 ng/pulse at 30-min intervals) over 12 h. alpha mRNA levels were increased by all GnRH doses greater than 5 ng with maximum responses after 250 ng pulses. LH and FSH beta mRNAs were both elevated by GnRH pulse doses of 0.5-25 ng (P less than 0.05 vs. saline controls). Maximal increases (2-fold) were seen after 5 ng pulses for LH beta and after 15-ng pulses for FSH beta mRNA. These results show that pulsatile GnRH increases FSH beta mRNA more rapidly than alpha or LH beta mRNAs in female rats. In addition, high amplitude GnRH pulses increase only alpha mRNA, whereas both LH beta and FSH beta mRNAs show maximum responses to lower doses. The data suggest that alterations in the amplitude of the GnRH pulsatile signal can exert differential effects on gonadotropin gene expression.

Thyrotoxicosis caused by thyroid cancer.

Well-differentiated follicular carcinoma causing thyrotoxicosis is a rare entity. The age and sex distribution is no different from that of other patients with follicular carcinoma, with 87% older than the age of 40 and a female:male ratio of 3:1. The clinical presentation is similar to that of Graves' patients except that evidence of metastatic disease is often present (soft tissue masses, bone pain). The metastases are in the usual locations (bone, lung, mediastinum) and are often bulky. Despite the poor efficiency of iodine uptake and thyroid hormone production, the large tumor mass is capable of producing excessive hormone. Laboratory data confirm the hyperthyroid state, but the occurrence of T3 elevations with normal T4 levels is common, and T3 toxicosis may be missed if only T4 levels are measured. The role of thyroid stimulating immunoglobulins is still evolving, but such stimulators may support the growth of metastatic thyroid carcinoma and promote the development of hyperthyroidism. The treatment of these patients varied. Most had thyroidectomy followed by 131I therapy. Dosimetry allows for the administration of the largest dose of 131I with acceptable side effects. A good response to radioiodine predicted a more favorable outcome. The survival of patients with metastatic thyroid carcinoma causing hyperthyroidism does not differ from euthyroid patients with metastatic follicular disease (10-year survival, 59%).

Gonadotrophin-releasing hormone regulation of gonadotrophin subunit gene expression: studies in tri-iodothyronine-suppressed rats.

We have previously shown that a pulsatile gonadotrophin-releasing hormone (GnRH) stimulus can increase steady-state levels of alpha and LH-beta subunit mRNAs in the male rat pituitary. Since alpha subunit is produced in both thyrotroph and gonadotroph cells, the effect of GnRH specifically on gonadotroph alpha gene expression is uncertain. To address this tissue, adult male rats were given injections of tri-iodothyronine (T3; 20 micrograms/100 g body wt, i.p.) daily for 8 days (day 8 = day of death) in order to decrease thyrotroph alpha mRNA levels (+T3 group). Saline injections (i.p.) were given to control animals (-T3group). Three days before GnRH administration, the animals were castrated and testosterone implants inserted s.c., to inhibit endogenous GnRH secretion. GnRH pulses (25 ng/pulse; 30-min interval) were given to freely moving animals (saline pulses to controls) via an atrial cannula for 12,24 or 48 h. Serum LH and FSH were measured before and 20 min after the last GnRH pulse. Pituitary RNA was extracted and alpha, LH-beta, FSH-beta and prolactin mRNA levels were determined by dotblot hybridization using 32P-labelled cDNA probes. Castration and testosterone replacement reduced alpha and LH-beta mRNA levels by 30 and 40% respectively, compared with levels in untreated intact males, but did not decrease FSH-beta concentrations. T3 administration further decreased alpha mRNA to 30% of values seen in intact males, but LH-beta mRNA levels were unchanged. FSH-beta mRNA concentrations were decreased by 23% in T3-treated rats (P less than 0.05 vs intact controls).(ABSTRACT TRUNCATED AT 250 WORDS)

Gonadal steroids effect similar regulation of gonadotrophin subunit mRNA expression in both male and female rats.

Gonadal steroids can act both indirectly via gonadotrophin-releasing hormone (GnRH) and directly on the pituitary to regulate gonadotrophin subunit gene expression. Recent studies to assess a possible direct action at the pituitary have shown that testosterone, when given to males in the absence of endogenous GnRH action, selectively increases FSH-beta mRNA concentrations. Conversely, in females, oestradiol appears to regulate gonadotrophin subunit mRNAs primarily via GnRH. The present study was designed to determine whether these differing results reflect specific actions of the gonadal steroids themselves or different responses of the pituitary gonadotroph cells in males and females. Rats which had been castrated 7 days earlier were given silicone elastomer implants (s.c.) containing oestradiol (plasma oestradiol 68 +/- 4 ng/l) in males or testosterone (plasma testosterone 3.5 +/- 0.3 micrograms/l) in females in the absence or presence of a GnRH antagonist. Seven days later pituitaries were removed and steady-state mRNA concentrations measured by dot-blot hybridization. In males, oestradiol reduced LH-beta and FSH-beta but not alpha mRNA. The antagonist reduced levels of all three subunit mRNAs in males and the addition of oestradiol had no further effect, suggesting that oestradiol regulates gonadotrophin subunit gene expression in males by suppressing GnRH secretion. In females, testosterone reduced all three subunit mRNAs though FSH-beta remained threefold higher than in intact animals. The GnRH antagonist was as effective as testosterone alone and reduced alpha and LH-beta to levels found in intact animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of massive air embolism during open heart surgery.

Two patients in whom a massive bolus of air was introduced into the arterial circuit and ascending aorta during valve replacement and in whom the recovery was complete are presented. The technical details of the management of this serious accident are described.

Effect of water content on the physical properties of model dentine primer and bonding resins.

OBJECTIVE: Primers and adhesives containing hydroxyethyl methacrylate (HEMA) are placed on moist dentine even though several studies indicate that water may interfere with the polymerization reaction. The purpose of this study was to evaluate the influence of increasing amounts of water on the physical properties of a model dentine primer resin (HEMA) and model dentine bonding resin (a mixture of HEMA and Bis-GMA). METHODS: Miniature (ca 10 x 0.5 mm (long x thick) hour-glass shaped and parallel-sided specimens were created by casting the monomer or comonomer mixtures into appropriately shaped moulds. The water content was either 0, 5, 9, 17 or 29 vol%. One hour after polymerization, half the specimens were subjected to physical testing under dry conditions. The other half were immersed in water for 24 h and then tested while wet. The ultimate tensile strength (UTS), modulus of elasticity (E), percent elongation at failure, and toughness were calculated. RESULTS: The properties of the dry-stored primer and bonding resins were not altered by water incorporation up to 9 vol%. Higher water content lowered the physical properties (P < 0.05). Immersion of primers polymers in water for 24 h significantly decreased their properties. Water immersion of the bonding resins was unaffected only for specimens containing 0 or 5 vol% water. CONCLUSIONS: The plasticizing effects of extrinsic water are far more important than the effects of intrinsic water in poly-HEMA resin. Hybrid layers composed primarily of poly-HEMA would be expected to be more elastic than those made with bifunctional, cross-linked polymer chains.

Evaluation of the interface between one-bottle bonding agents and dentin by cryopreparation and low-temperature scanning electron microscopy (LTSEM). A pilot study on perfused dentinal samples.

OBJECTIVES: Dentin bonding samples are generally observed in the high vacuum chamber of an electron microscope only after completion of the bonding procedure fixation, dehydration and drying of the specimens. The purpose of this study was to observe the effect of each step in the application of various one-bottle dentin bonding agents (DBA) using cryopreparation followed by low-temperature scanning electron microscopy (LTSEM). METHODS: Prime&Bond 2.1 (P&B 2.1), Coltène Experimental (Exp.) and Syntac Single Component (Syntac SC) were applied onto perfused dentin of extracted, human third permanent molar teeth. After acid-etching, rinsing and drying, and following the application of the respective resins, the teeth were fractured at random and plunge-frozen in liquid nitrogen before examination under LTSEM. As this method preserves the state of the treated surface at the moment when it is frozen, each step of the application of the DBA can be observed as if it were a 'real-time' procedure. RESULTS: Acid-etching the dentin resulted in the removal of the smear layer for all materials tested. Those one-bottle DBAs which recommend the application of two consecutive resin layers (P&B 2.1 and Syntac SC) showed incomplete saturation of the dentinal surface after application of the first layer. With Syntac SC the incomplete saturation was more pronounced than with P&B 2.1. The use of Exp. resulted in a much more homogeneous coverage of the dentin despite only one layer of resin having been applied. CONCLUSION: It is concluded that cryo-preparation followed by LTSEM appears to be a method which allows each stage of the application of DBA to be evaluated.

Nanoleakage at the dentin adhesive interface vs microtensile bond strength.

Excessive etching of the dentin may decrease bond strength because the adhesive may fail to completely infiltrate to the base of the over-etched demineralized collagen network. The purpose of the present study was to evaluate the influence of increasing etching times on the microtensile bond strength of Single Bond and the leakage of silver ions within the hybrid layer. After etching occlusal dentin for 15, 30, or 60 seconds with 35% phosphoric acid gel, Single Bond was applied and cured for 10 seconds. Z100 was added and cured for 60 seconds. After 24 hours of water immersion, the teeth were sectioned into slices 0.7 mm thick, and hour-glass-shaped specimens were prepared. Alternate slices were either dried for 30 minutes in air, kept wet, or they were coated with fingernail varnish except for 0.5 mm around the bonded area. Only the varnished samples were then stained with 50% AgNO3. Microtensile bond strength was tested using a Vitrodyne V-1000 universal tester. The samples of the stained group were embedded in self-curing PMMA and polished. All samples were observed with an SEM. Nanoleakage of silver ions was measured by exposure to laser ablation with an inductively connected plasma mass spectrometer and by electron dispersive elemental analysis. Increasing etching times seemed to have a negligible effect on bond strength of Single Bond, producing an average value of ca 38 MPa. However, the silver uptake increased upon prolonged etching times. Short-term results suggest that overetching has no detrimental effect on bond strength values of Single Bond. However, increased silver uptake, depending on the etching time, raises concern about the long-term stability of the bond.

The dual bonding technique: a modified method to improve adhesive luting procedures.

Indirect restorative procedures usually require temporary restorations for protection of the pulp and for restoring the patients esthetic and functional needs. The use of temporary cements, either with or without eugenol, however, considerably decreases the adhesion of the bond on dentin if--according to the conventional technique--such dentin bonding systems are applied once at the moment of final cementation. With a dual application of the dentin bonding agents a considerable increase in bond strength values was discovered. This article presents a modified luting procedure called the "dual bonding technique."