The Effect of Instrumentation Taper on Dentin Conservation

Introduction: The aim of this in vitro study was two part. The first being to assess and compare the amount of dentin removed by an instrument with a taper of 0.04 versus an instrument with a taper of 0.06 using the Edge Evolve® file system at different increments within the canal system. Secondly, this study evaluated whether instrumentation with either taper resulted in a remaining dentin thickness (RDT) of less than 0.3mm. If this RDT was imposed upon, fracture resistance was compromised. Both pre and post instrumentation measurements were taken of samples instrumented with the 0.04 and 0.06 tapered files. Methods: Ten maxillary premolars exhibiting Weine class III canal systems and minimal to no root canal curvature were mounted in an acrylic resin filled K-cube. Each acrylic resin cube was sectioned horizontally at 3, 6, 9, and 12mm increments from the apex. The K-cube is a device which allows the investigator to disassemble and then reassemble root slices in their original orientation. Dentin thickness was measured at three positions on each canal using the Zeiss Discovery V20 stereomicroscope. The sections were then reassembled into the K-cube. The ten premolar roots were separated into two groups. In half of the teeth the buccal canals were instrumented with 0.04 tapered files and the lingual canals instrumented with 0.06 tapered files. In the other half of the teeth, instrumentation was reversed: the buccal canals were instrumented with 0.06 tapered files and the lingual canals were instrumented with 0.04 tapered files. Root sections were again separated, and the remaining dentin thickness was measured. A repeated-measures mixed-model ANCOVA was performed to analyze the effect of taper on RDT. Results: The amount of dentin removed was statistically different between the two tapers (P=0.02). Across all of the slices and positions, the 0.04 tapered instruments had an average pre-post difference of 0.1313mm. The 0.06 tapered instruments had an average pre-post difference of 0.1672mm. None of the instruments imposed upon the recommended 0.3mm RDT. Conclusion: The 0.04 tapered files instrument with greater conservancy than the 0.06 tapered files. The 0.06 tapered files had their greatest effect on the canal in the 9mm and 12mm sections. However, neither taper imposed upon the recommended RDT for optimal fracture resistance within the apical 12mm root portion observed in this study. Keywords: Instrumentation, Edge Evolve, Root canal preparation, Tape

Efficient circuit triggers high-current, high-voltage pulses

Modified circuit uses diodes to effectively disconnect the charging resistors from the circuit during the discharge cycle. Result is an efficient parallel charging, high voltage pulse modulator with low voltage rating of components

Fatigue properties of sheet, bar, and cast metallic materials for cryogenic applications

Cryogenic fatigue and tensile properties for metallic materials are determined in the operating life-time range of ten thousand to ten million cycles at room temperature, at minus 320 degrees F, and at minus 423 degrees F. Results are presented as stress versus number of cycles to failure

City strategy : final evaluation

The City Strategy (CS) concept was first announced in the 2006 Welfare Reform Green Paper – A new deal for welfare: Empowering people to work. CS was designed at a time of growth in the national economy to combat enduring pockets of entrenched worklessness and poverty in urban areas by empowering local institutions to come together in partnerships to develop locally sensitive solutions. It was premised on the idea that developing a better understanding of the local welfare to work arena would allow partnerships to align and pool funding and resources to reduce duplication of services and fill gaps in provision. The ‘theory of change’ underlying CS suggested that such an approach would result in more coordinated services which would be able to generate extra positive outcomes in terms of getting people into jobs and sustaining them in employment over and above existing provision. CS was initially set to run for two years from April 2007 to March 2009 in 15 CS Pathfinder (CSP) areas, varying in size from five wards in one town through single local authority areas to subregional groupings of multiple local authority areas, across Great Britain. In July 2008, the Secretary of State for Work and Pensions announced an extension for a further two years to March 2011. In April 2009, two local areas in Wales, which were in receipt of monies from the Deprived Areas Fund (DAF), were invited by the Department for Work and Pensions (DWP) to form local partnerships with a similar remit to the CSPs, albeit more limited in scope – to develop locally sensitive solutions to economic inactivity, to the CSPs. During the period that the CS initiative was operational, economic conditions changed markedly with a severe recession, followed by fragile recovery. The CSPs had to cope with ongoing changes in policy throughout the lifetime of the CS initiative, including a General Election and a new Coalition Government at Westminster early in the fourth year. While policy changes are a fact of life for local practitioners operating in the welfare to work arena, the global recession in 2008/09 marked a fundamental change in the context in which local partnerships operated

Instrument quickly transposes ground reference target to eye level

Optical alignment of equipment is facilitated by a traverse target with a string suspending a plumb bob to transpose the ground level point to eye level operation. This instrument appreciably decreases the time required from the present method but achieves the same degree of precision

The low energy expansion of the one-loop type II superstring amplitude

The one-loop four-graviton amplitude in either of the type II superstring theories is expanded in powers of the external momenta up to and including terms of order s^4 log s R^4, where R^4 denotes a specific contraction of four linearized Weyl tensors and s is a Mandelstam invariant. Terms in this series are obtained by integrating powers of the two-dimensional scalar field theory propagator over the toroidal world-sheet as well as the moduli of the torus. The values of these coefficients match expectations based on duality relations between string theory and eleven-dimensional supergravity.Comment: harvmac (b), 25 pages, 3 eps figures. v2: Factors of 2 corrected. Conclusion unchange

Naming and recognition of six foot lesions of sheep using written and pictorial information: a study of 809 English sheep farmers

In 2005, 3000 questionnaires were sent to a random sample of English sheep farmers from a list kept by the English Beef and Lamb Executive (EBLEX) to investigate whether farmers could correctly name six common foot lesions in sheep from a characteristic picture and a written description. The lesions were interdigital dermatitis (ID), footrot (FR), contagious ovine digital dermatitis (CODD), shelly hoof, foot abscess and toe granuloma. In addition, farmers were asked to report the total percent of lame sheep in their flock in 2004 and the percent of this lameness attributable to each of the six lesions listed above. The overall response percentage was 44 with a useable response of 32%. Fifty-nine farmers out of 262 (23%) who answered all six questions named all six lesions correctly. This was greater than expected by chance. The same questionnaire of six lesions was presented at a meeting of specialist sheep advisors, primarily veterinarians, 37/47 (79%) responders named all six lesions correctly. From the six lesions listed above, the percent correctly named by farmers was approximately 83%, 85%, 36%, 28%, 65% and 43% and the percent incorrectly attributed to another lesion was 5%, 47%, 10%, 13%, 35% and 7%, respectively. The most commonly used incorrect name was FR, with farmers tending to name any hoof horn lesion as FR. A comparison of the distribution of sheep lame by a lesion correctly named compared with the same lesion incorrectly named as FR suggested that farmers recognised lesions but did not name them correctly; the distribution of lameness fitted the pattern for the correctly named lesion rather than the pattern of lameness attributed to FR. The results were validated with farm visits and a repeatability study of the questionnaire. The mean farmer-estimated prevalence for all lameness was 10.4%; with 6.9%, 3.7%, 2.4%, 1.9%, 0.9% and 0.8% of the sheep lame with ID, FR, CODD, shelly hoof, foot abscess and toe granuloma respectively from respondents who correctly named these lesions. Whilst ID and FR were the most prevalent causes of lameness in most flocks it is possible that in up to 17% flocks the primary cause of lameness was a different lesion

Farmers' practices and factors associated with the prevalence of all lameness and lameness attributed to interdigital dermatitis and footrot in sheep flocks in England in 2004

The aim of this study was to investigate whether the risk factors associated with all causes of lameness in sheep differed from those associated with the lesion specific causes of lameness, interdigital dermatitis (ID) and footrot (FR). A total of 809 randomly selected English sheep farmers participated in a postal survey in 2005. Data were requested on their management of lameness in 2004 and whether this had changed from 2003 and the prevalence of all lameness, and lameness caused by ID and FR. The farmer ability to recognise ID and FR was assessed from their responses to a written and pictorial description. On 443 farms where both ID and FR were correctly named by the farmer, the mean prevalence of all lameness, and lameness caused by ID and FR were 10.0% (95% CI: 8.9, 10.8), 6.5% (95% CI: 5.8, 7.3) and 3.1% (95% CI: 2.8, 3.6), respectively. The mean prevalence of all lameness on all 809 farms was not significantly different at 10.2% (95% CI: 9.2, 11.0). The data were analysed using negative binomial regression models with the three outcomes farmer estimated prevalence of all lameness and lameness caused by ID or FR in 2004. Farmers who changed management of sheep between 2003 and 2004 were excluded from the analysis, thus all fixed effects were the farmers’ managements in 2003 and 2004 to ensure that the management was in place for at least one year before the prevalence estimates. Routine foot trimming ≥once/year compared with no routine foot trimming was significantly associated with an increased prevalence of all lameness (prevalence ratio (PR) = 1.34), ID (PR = 1.50) and FR (PR = 1.35). Footbathing was also significantly associated with increased prevalence of all lameness (PR = 1.67), ID (PR = 1.68) and FR (PR = 1.76). A stocking density of >8 ewes/ha was associated with a significantly increased prevalence of all lameness (PR = 1.26) and ID (PR = 1.39). There was a significantly lower prevalence of FR (PR = 0.73; PR = 0.70, respectively) on farms in the North East and South East of England. Separating lame sheep at pasture was associated with a decreased prevalence of all lameness and ID (PR = 0.75; PR = 0.73) and location of the farm in South East England was associated with a lower prevalence of all lameness and ID (PR = 0.75; PR = 0.71, respectively). We conclude that management factors associated with all lameness, and lameness attributed to ID and FR are similar

Recognition of lameness and decisions to catch for inspection among sheep farmers and specialists in GB

Background: Epidemiological studies have used farmer estimates of the prevalence of lameness in their flocks. This assumes that farmers can identify lame sheep. Eight movie clips of sheep with locomotion from sound to moderately lame were used to investigate the ability of farmers and sheep specialists to recognise lame sheep. Each participant was asked to complete a form and indicate, for each movie clip, whether they thought the sheep was lame and whether they would catch it if it was the only lame sheep or if 2 – 5, 6 – 10 or > 10 sheep were equally lame. The farmers' responses were compared with their estimates of flock lameness prevalence and the interval between observing a lame sheep and catching it. Results: 178 farmers and 54 sheep specialists participated. Participants could identify even mildly lame sheep but made a separate decision on whether to catch them. This decision was dependent on the severity of lameness and the number of sheep lame in a group. Those who said they would catch the first lame sheep in a group were significantly more likely to catch mildly lame sheep (farmer-reported median prevalence of lameness 5% (IQR: 2%–6%)). In contrast, farmers who waited for several sheep to be lame indicated that they would only catch more severely lame sheep (farmer reported median flock lameness 11% (IQR: 9%–15%)). Approximately 15% of farmers did not catch individual lame sheep (farmer reported median flock lameness 15% (IQR: 10%–15%)). The flock prevalence of lameness increased as time to treatment increased and time to treatment was positively correlated with only catching more severely lame sheep. Conclusion: If movie-clips are similar to the flock situation, farmers and specialists can recognise even mildly lame sheep but vary in their management from prompt treatment of the first lame sheep in a group to no individual sheep treatments. The former practices would be appropriate to minimise transmission of footrot, a common, infectious cause of lameness and so reduce its incidence. The analysis also suggests that farmers estimate lameness prevalence relatively accurately because farmers who treated the first mildly lame sheep in a group also reported the lowest prevalence of lameness in their flock

A critical comparison of using a probabilistic weather generator versus a change factor approach: irrigation reservoir planning under climate change

In the UK, there is a growing interest in constructing on-farm irrigation reservoirs, however deciding the optimum reservoir capacity is not simple. There are two distinct approaches to generating the future daily weather datasets needed to calculate future irrigation need. The change factor approach perturbs the observed record using monthly change factors derived from downscaled climate models. This assumes that whilst the climate changes, the day-to-day climate variability itself is stationary. Problems may arise where the instrumental record is insufficient or particularly suspect. Alternatively, probabilistic weather generators can be used to identify options which are considered more robust to climate change uncertainty because they consider non-stationary climate variability. This paper explores the difference between using the change factor approach and a probabilistic weather generator for informing farm reservoir design at three sites in the UK. Decision outcomes obtained using the current normal practice of 80% probability of non-exceedance rule and simple economic optimisations are also compared. Decision outcomes obtained using the change factor approach and probabilistic weather generators are significantly different; whether these differences translate to real-world differences is discussed. This study also found that using the 80% probability of non-exceedance rule could potentially result in maladaptation