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At least 379 records · Page 21Linked to original sources

PubMed2002

Evaluation of Glyde File Prep in combination with sodium hypochlorite as a root canal irrigant.

The purpose of this study using a scanning electron microscope was to investigate the efficacy of four different irrigation techniques after canal preparation with Profile Ni-Ti rotary instruments. A modified technique for the use of Glyde File Prep is proposed. Forty anterior teeth were divided into four groups, instrumented, and irrigated as follows: physiological solution (group A), 2.5% sodium hypochlorite (group B), 2.5% sodium hypochlorite and Glyde File Prep (group C), and 2.5% sodium hypochlorite and Glyde File Prep applied at the end of the preparation with sterile paper points (group D). After scanning electron microscopic evaluation at three different levels, debris, smear layer, and dentinal tubules were scored. Groups A and B had significantly more smear layer and less open tubules on the canal walls compared with the group C and group D samples. Differences in the mean amount of debris between group A samples and other irrigation regimes were statistically significant.

Chelating Agents↗

PubMed2002

Gutta-percha retreatment: effectiveness of nickel-titanium rotary instruments versus stainless steel hand files.

This study compared the cleanliness of the root canal walls after retreatment using nickel titanium (NiTi) rotary and stainless steel (SS) files. Also compared were time of retreatment and canal deviation. Forty extracted canines were step-back prepared and obturated with gutta-percha and sealer. Retreatment was performed either by using chloroform and SS hand files or chloroform and NiTi rotary files. Time for retreatment was recorded. Radiographs of the root canal system before and after retreatment were made. Teeth were split longitudinally, photographed, and projected onto a screen. The amount of gutta-percha/sealer remaining on the canal walls was then traced and measured. The amount remaining was analyzed and compared statistically between NiTi and SS groups by t test. Results showed that the mean percentage of wall coverage by remaining obturating material in the SS group was 13.6% and was 15.2% for the NiTi group. There was no statistically significant difference (p = 0.361). No severe canal deviation occurred with either retreatment method. Mean retreatment time for the SS group was 6.3 min and 7.9 min for the NiTi group; the difference was statistically significant (t test p < 0.001). In conclusion, NiTi rotary and SS hand were similar in material remaining after retreatment, but SS hand was a bit faster.

Cuspid↗

PubMed2002

Effect of physical vapor deposition on cutting efficiency of nickel-titanium files.

The purpose of this study was to investigate possible changes in cutting efficiency of nickel-titanium K-files that had undergone physical vapor deposition coating. Titanium nitride coatings were deposited using different process parameters. A total of 84 nickel-titanium K-files (size 35) were randomly divided into 7 groups of 12 instruments each. Groups A to F (experimental): instruments were coated with titanium nitride using different process parameters regarding substrate temperature, applied voltage, coating thickness, and ion bombardment. Group K (control): samples were not coated with titanium nitride. The cutting efficiency of all instruments was determined in a rotary working motion by means of a computer-driven testing device. Special plastic samples with a cylindrical canal were used, and the maximum penetration depth of the instruments into the lumen was the criterion for cutting efficiency. Instruments of groups A, F, and C achieved significantly greater penetration depths than the uncoated instruments of the control group (p < 0.05). Cutting efficiency of physical vapor deposition-coated nickel-titanium files was increased by up to 26.2% in comparison with uncoated instruments.

Analysis of Variance↗

PubMed2004

Comparison instrumentation reamers and files versus a flat-sided design of conventional noninterrupted, flat-sided design.

The in vitro study measured the time required to instrument and shape canals by conventional reamers and files compared with a newly introduced reamer and file system. This experiment was divided into four groups with 10 block samples for each group. The results of instrumentation time demonstrate that the noninterrupted flat-sided design (EZ-Fill SafeSider reamers) produced the fastest times for comparably shaped canals because of reduced engagement of the instrument with the walls of the canal compared with conventional instruments. The conventional designs for both reamers and files result in increased instrumentation time compared with their EZ-Fill SafeSider counterparts.

Acrylic Resins↗

PubMed2002

Different time regimes of tracer exchange in single-file systems.

A complete description of the time dependence of tracer exchange in single-file systems is given. It is based on the combined application of dynamic Monte Carlo simulations and analytical calculations. Depending on the time elapsed, the tracer exchange is found to have different time scaling related to transport modes of either normal diffusion or single-file diffusion. The mode of single-file diffusion is reproduced by recent tracer exchange experiments conducted by laser-polarized 129Xe NMR spectroscopy.

Journal Article↗

PubMed2003

Infinitely fast diffusion in single-file systems.

We have used dynamic Monte Carlo(DMC) methods and analytical techniques to analyze single-file systems for which diffusion is infinitely fast. We have simplified the master equation removing the fast reactions, and we have introduced a DMC algorithm for infinitely fast diffusion. The DMC method for fast diffusion give similar results as the standard DMC with high diffusion rates. We have investigated the influence of characteristic parameters, such as pipe length, adsorption, desorption, and conversion rate constants on the steady-state properties of single-file systems with a reaction, looking at cases when all the sites are reactive and when only some of them are reactive. We find that the effect of fast diffusion on single-file properties of the system is absent even when diffusion is infinitely fast. Diffusion is not important in these systems. Smaller systems are less reactive and the occupancy profiles for infinitely long systems show an exponential behavior.

Journal Article↗

PubMed2002

PDB Goodies--a web-based GUI to manipulate the Protein Data Bank file.

PDB Goodies is a web-based graphical user interface (GUI) to manipulate the Protein Data Bank file containing the three-dimensional atomic coordinates of protein structures. The program also allows users to save the manipulated three-dimensional atomic coordinate file on their local client system. These fragments are used in various stages of structure elucidation and analysis. This software is incorporated with all the three-dimensional protein structures available in the Protein Data Bank, which presently holds approximately 18 000 structures. In addition, this program works on a three-dimensional atomic coordinate file (Protein Data Bank format) uploaded from the client machine. The program is written using CGI/PERL scripts and is platform independent. The program PDB Goodies can be accessed over the World Wide Web at http://144.16.71.11/pdbgoodies/.

Computer Graphics↗

PubMed1994

A model system for evaluating filing technique.

The aim of this study was to develop a model system to demonstrate the pattern of load and how much is applied. A lower molar was mounted on a beam and attached to a mandibular phantom head jaw. A strain gauge fitted to the beam allowed loading of the molar to be recorded, during root canal preparation. Ten operators were asked to instrument the distal root canal; after preparation the operators were shown a graphical representation of the loads applied. This formed the basis of discussion and instruction in filing technique. The operators then repeated the filing. The results showed that prior to instruction operators used a push-pull motion, applying a constant lateral force to the canal wall. After instruction and discussion of the graphical representation of the loads applied the stroke rates used were slower and loads applied were higher (two-sample t-test, n = 10, P < 0.01). The experiment was repeated 1 year later and this showed that the change in technique had been retained. In conclusion, this model system allows visual feedback to the operator and can be used as an aid to teaching filing technique.

Analysis of Variance↗

PubMed1995

Torsional and stiffness properties of nickel-titanium K files.

The purpose of this study was to compare stiffness and resistance to fracture of four brands of nickel titanium K files. Instruments of sizes 15 to 40 were tested according to ANSI/ADA Specification No. 28. Resistance to fracture was determined by twisting and measuring the maximum torque and angular deflection at failure. Stiffness was determined by measuring the moment required to bend the instrument 45 degrees. The permanent deformation angle remaining between the tip and the flutes of the instruments after bending ceased was also recorded. Nickel titanium K files satisfied and far exceeded specification standards for stiffness. They also satisfied and exceeded the standards for angular deflection at failure. They met or exceeded the maximum torque at failure standards in all sizes except for the size 40 of the Maillefer Niti, and the size 30 of the MacSpadden Niti. Nickel titanium K files presented a null permanent deformation angle. Clinical studies are required to evaluate the influence of low bending moment on other properties such as breakage and canal transportation.

American Dental Association↗

PubMed2006

Comparison of curved canals preparations using profile, GT and Hero 642 rotary files.

This study compared preparations of curved canals, using Profile, GT file and Hero 642 rotary files. A total of 30 mesiobuccal canals of extracted first and second mandibular molars were used in this study. The teeth were embedded in resin and a pre-operative radiograph was taken. The specimens were then randomly divided into three instrument groups. Pre- and post-instrumentation radiographic images were scanned and superimposed using the VISI CAD/CAM program. At nine horizontal sections at 1 mm increments from the apex, it calculated pre- and post-instrumentation cross sectional areas (mm(2)) and enlargements to the inner aspect and outer aspects (mm). A Kruskal-Wallis test found no statistical difference among the groups in terms of total areas removed by each instrument (P > 0.05). It also found no significant difference in any group between the total of the inner and outer enlargements (P > 0.05). However the GT file removed significantly more material from the outer side of the canal than the inside at sections 3-5, and the Hero removed significantly more material from the outer side at sections 7-9 (P < 0.05). All instruments produced preparations that maintained original canal curvatures.

Dental Alloys↗

PubMed2000

Drowning and alcohol in New Zealand: what do the coroner's files tell us?

OBJECTIVE: To provide a systematic review of the details on alcohol involvement available in the coronial files to determine if there is enough evidence to estimate the role of alcohol in drowning. METHOD: We reviewed the coroner's files of persons 10 years or older who drowned in New Zealand between 1992-1994 inclusive. RESULTS: A total of 320 coroner's files were examined. Blood Alcohol Concentrations (BACs) were taken in 115 cases (36%) and positive for 50% of these. When accounting for the incomplete testing by using all the information on alcohol involvement collected, between 30-40% of the cases were estimated to have a positive BAC and between 17-24% to have a BAC 100 mg/dL or higher. CONCLUSION: The quality and completeness of current coronial information on alcohol involvement in drowning is insufficient to arrive at an accurate estimate of the percentage of drownings where alcohol was a factor. IMPLICATIONS: Coroners should test drowning victims 10 years and older for BAC. These data should be systematically recorded and processed with the goal of determining who should be targeted in drowning and alcohol prevention programs.

Adolescent↗

PubMed1995

Removal of hard tooth structure by ROOTSHAPE root planing files used with a modified EVA contra-angle.

The results of numerous recent investigations indicate that root contamination with bacteria and endotoxins is limited to the root surface only. Therefore, methods on root surfaces instrumentation that preserve root substance should be focused on. Newly available instruments or treatment systems should be evaluated for their root substance-removing potential. The devices for root planing presented here comprised specific files (Rootshape) (with diamond-coating on their convex working surfaces used in conjunction with a water-spray-cooled contra-angle head transforming rotational movements into translatory oscillations. The substance-removal potential of rigid and flexible files with diamond coatings of 2-4, 15, 25 and 40 microns compared with that of regular hand curettes, was evaluated under various working forces. The results demonstrated, that depending on the grit size of the diamond coating, the Rootshape files removed less and in no instance greater amounts of root surface substance than did hand instruments.

Analysis of Variance↗

PubMed1996

Influence of storage conditions of extracted teeth on dentine removal by a standardised method of filing.

Extracted teeth are often stored in a variety of solutions for different lengths of time prior to use in studies on the efficacy of root canal preparation. The aim of this study was to evaluate the effect of duration (12 h, 1, 4 and 15 weeks) and type of storage medium (Saline, Formal-saline, Sodium Hypochlorite and Dry conditions) on dentine removal by standardised filing. Apparatus was constructed to standardise variables inherent in filing. These included the file, the rate, duration and amplitude of its push-pull motion, its alignment with a flat dentine surface, the interfacial force (80 gms) and rate of irrigation. Freshly extracted teeth were immediately stored in one of the 13 combinations of storage media and duration. The teeth were prepared into test specimens by splitting the roots and flattening the root canal surface. Twenty specimens were designated to each combination. Dentine removal was quantified by profilometry using maximum depth at 8 selected points. Statistical analysis of the mean values showed highly significant differences (p<0.001) between the media at 1, 4 and 15 weeks.When comparisons of mean values were made within the storage groups, there were highly significant differences (p<0.001) in dentine removal between 0, 1, 4 and 15 weeks of storage in sodium hypochlorite and saline. There were no significant differences found for storage in formal-saline. In dry conditions, the differences were significant (p<0.01) between 0, 1, 4 and 15 weeks of storage, but were not significant when the 4 weeks values were excluded.

Analysis of Variance↗

PubMed2003

Effective cleaning protocols for rotary niclkel-titanium files.

Cleaning of dental instruments before sterilisation is an essential part of processing for re-use. Rotary nickel-titanium (NiTi) files as obtained from the manufacturer are mostly not sterile and require cleaning and sterilisation both before first use and for re-use. We describe here two simple, practical cleaning protocols that are effective in removing organic debris from files. Rotary NiTi files can be safely re-used from an infection control perspective.

Dental Alloys↗

PubMed2004

An extensive log-file analysis of step-and-shoot intensity modulated radiation therapy segment delivery errors.

We present a study to evaluate the monitor unit (MU), dosimetric, and leaf-motion errors found in the delivery of 91 step-and-shoot IMRT treatment plans performed at three nominal dose rates using a dual modality high energy Linac (Varian 2100 C/D, Varian Medical Systems Inc., Palo Alto, CA) equipped with a 120-leaf multileaf collimator (MLC). The analysis was performed by studying log files generated by the MLC controller system. Recent studies by our group have validated that the automatically generated MLC log files accurately record the actual system delivery. A total of 635 beams were delivered at three nominal dose rates: 100, 300, and 600 MU/min. The log files were manually retrieved and analysis software was developed to extract the recorded MU delivery and leaf positions for each segment. Our analysis revealed that the magnitude of segment MU errors were independent of the planned segment MUs. Segment MU errors were found to increase with dose rate having maximum errors per segment of +/-1.8 MU at 600 MU/min, +/-0.8 MU at 300 MU/min, and +/-0.5 MU at 100 MU/min. The total absolute MU error in each plan was observed to increase with the number of plan segments, with the trend increasing more rapidly for higher dose rates. Three dimensional dose distributions were recomputed based on the observed segment MU errors for three plans with large cumulative absolute MU errors. Comparison with the original treatment plans indicated no clinically significant consequences due to these errors. In addition, approximately 80% of the total segment deliveries reported at least one collimator leaf moving at least 1 mm (projected at isocenter) during segment delivery. Such errors occur near the end of segment delivery and have been previously observed by our group using a fast video-based electronic portal imaging device. At 600 MU/min, between 5% and 23% of the plan MUs were delivered during leaf motion that had exceeded a 1 mm position tolerance. These leaf motion errors were not included in the treatment plan recalculations performed in this study.

Biophysical Phenomena↗

PubMed2002

Verification of dynamic and segmental IMRT delivery by dynamic log file analysis.

A program has been developed to evaluate the delivered fluence of step-and-shoot segmental and sliding window dynamic multileaf collimator (MLC) fields. To automate these checks, a number of tools have been developed using data available from the dynamic log files that can be created each time a dynamic delivery occurs. Experiments were performed with a Varian 2100EX with a 120 leaf MLC equipped with dynamic capabilities. A dynamic leaf sequence is delivered and measured with film or an amorphous silicon imager. After delivery, the dynamic log file is written by the accelerator control system. The file reports the expected and actual position for each leaf and the dose fraction every 0.055 seconds. Leaf trajectories are calculated from this data and expected and actual fluence images are created from the difference of opposing leaf trajectories. These images can be compared with the expected delivery, measurements, and calculations of fluence. Tools have been developed to investigate other aspects of the delivery, such as specific leaf errors, beam hold-off flags sent by the control system to the MLC, and gap widths. This program is part of a semi-automated quality assurance (QA) system for pretreatment fluence verification and daily treatment verification of dynamic multileaf collimation (DMLC) delivery.

Computer Simulation↗

PubMed1995

Guide to the Internet. Logging in, fetching files, reading news.

Aside from email and the world wide web, there are several other systems for distributing information on the Internet. Telnet is a system that allows you to log on to a remote computer from anywhere on the Internet and affords access to many useful biomedical sites on the Internet. File transfer protocol (FTP) is a method of transferring files from one computer to another over the Internet. It can be used to download files, including software, from numerous publiclly accessible "anonymous FTP archives" around the world. Such archives can be searched using a tool known as Archie. Network News is a system of electronic discussion groups covering almost every imaginable subject, including many areas of medicine and the biomedical sciences; MOOs are virtual environments that allow real time electronic conferencing and teaching over the Internet. It is difficult to predict the future of medicine on the Internet. However, the net opens up many possibilities not available through previous technologies. It is now up to medical practitioners to realise the Internet's full potential.

Computer Communication Networks↗

PubMed1976

Computer printing and filing of microbiology reports. 1. Description of the system.

From March 1974 all reports from this microbiology department have been computer printed and filed. The system was designed to include every medically important microorganism and test. Technicians at the laboratory bench made their results computer-readable using Port-a-punch cards, and specimen details were recorded on paper-tape, allowing the full description of each specimen to appear on the report. A summary form of each microbiology phrase enabled copies of reports to be printed on wide paper with 12 to 18 reports per sheet; such copies, in alphabetical order for one day, and cumulatively for one week were used by staff answering enquiries to the office. This format could also be used for printing allthe reports for one patient. Retrieval of results from the files was easily performed and was useful to medical and laboratory staff and for control-of-infection purposes. The system was written in COBOL and was designed to be as cost-effective as possible without sacrificing accuracy; the cost of a report and its filing was 17-97 pence.

Computers↗