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At least 145 records · Page 8Linked to original sources

PubMed1999

Corrosion in stainless-steel and nickel-titanium files.

This study evaluated and compared the corrosion susceptibility of stainless-steel and nickel-titanium (NiTi) endodontic files immersed in sodium hypochlorite. For each of the stainless-steel files (Kerr K-Flex, Caulk Flex-O, and Union Broach Flex-R) plus the NiTi files (Union Broach NiTi and Tulsa NiTi), the cutting flutes of 24 ISO size 20 files were immersed into 5.25% sodium hypochlorite. Their open circuit potential (OCP) was recorded for 1 h on a strip chart with high impedance. The strip chart recording for each file was classified into a stability score: (i) stable, (ii) unstable, or (iii) erratic. The OCP was measured by a potentiostat and a standard calomel electrode reference. The OCP classification of unstable and erratic for the files evaluated were as follows: K-Flex (16%), Flex-R (12%), Flex-O (75%), Union Broach NiTi (62%), and Tulsa NiTi (0%). After OCP testing, each of the 120 files was inspected by light microscopy at x 25. The frequencies of visually observed corrosion were detected as follows: K-Flex (2/24), Flex-R (1/24), Flex-O (6/24), Union Broach NiTi (2/24), and Tulsa NiTi (0/24). There was a significant difference in corrosion frequency between brands when evaluated by OCP and light microscopy; however, there was no significant difference between stainless steel and NiTi.

Analysis of Variance↗

PubMed2001

A reconstructed computerized tomographic comparison of Ni-Ti rotary GT files versus traditional instruments in canals shaped by novice operators.

AIM: The aim of this study was to compare the effects of preparation with conventional stainless steel Flexofiles and Gates Glidden burs versus nickel-titanium GT rotary files in the shaping of mesial root canals of extracted mandibular molars. METHODOLOGY: A total of 54 canals from 27 mesial roots of mandibular molar teeth were prepared using one of two methods by novice dental students. One canal in each root was prepared by a crown-down approach. utilizing stainless steel Flexofiles and Gates Glidden burs. The other canal was prepared using nickel-titanium GT rotary files in a crown-down fashion as recommended by the manufacturer. Preoperative CT scans of each root were recorded and 50 canal specimens were available for postoperative comparisons. Following canal shaping, postoperative scans were superimposed on the original images. Changes in canal area, canal transportation and thickness of remaining root structure at strategic levels of the root were analyzed. The time taken for each method was also noted. RESULTS: At the coronal and mid-root coronal one-third sections, the rotary GT files produced a significantly smaller postoperative canal area (P < 0.05). In the mid-root sections there was significantly less transportation of the root canal toward the furcation, and less thinning of the root structure with GT files compared to the stainless steel files (P < 0.05). Overall, there was greater conservation of structure coronally and more adequate shape in the mid-root level. The GT rotary technique was significantly faster than the stainless steel hand-held file technique (P < 0.0001). Two GT instruments fractured during the study. CONCLUSIONS: Under the conditions of this study, novice dental students were able to prepare curved root canals with Ni-Ti GT rotary files with less transportation and greater conservation of tooth structure, compared to canals prepared with hand instruments. The rotary technique was significantly faster.

Dental High-Speed Technique↗

PubMed2001

Comparison of the first file that fits at the apex, before and after early flaring.

The purpose of this study was to compare the first file that fits to the apex (FFFA) in each canal before and after early flaring to analyze if the size of file to fit to the apex would increase after flaring. One hundred mesial canals of lower first and second molars with complete apical formation and patent foramens were selected. The samples were randomly divided into two groups of 50 canals each. A file was fit to the apex in each canal and that size recorded. Radicular flaring was completed using Gates-Glidden drills in group 1 and Rapid Body Shapers in group 2. After flaring a file was again fit to the apex in the same manner as before and its size recorded. The mean diameter of FFFA before flaring (file diameters in mm x 10(-2)) was 14.46 (+/-4.12) and after 23.3 (+/-7.2) for group 1 (p < 0.001), whereas in group 2 the mean diameter of FFFA was 17.2 (+/-4.96) before and 25.6 (+/-6.36) after (p < 0.001). A Wilcoxon t test indicates a significant difference (p < 0.001) between the diameter of FFFA before and after flaring in both groups. The increase in diameter was approximately two file sizes for both groups. From this observation it is concluded that early radicular flaring increases the size file that is snug at the apex, and awareness of that difference gives the clinician a better sense of canal size. Early flaring of the canal provides better apical size information and with this awareness, a better decision can be made concerning the appropriate final diameter needed for complete apical shaping.

Anti-Infective Agents, Local↗

PubMed2002

Patency file and apical transportation: an in vitro study.

The purpose of this study was to evaluate the transportation produced at the apical foramen by the use of stainless steel and nickel-titanium K-files #10, #15, #20, and #25 as a patency file. Thirty human maxillary lateral incisors were transversally cut at 4 mm from the apex and mounted in square pieces of silicone with special marks to ensure repositioning of the specimens. The specimens were randomly divided in two equal groups of 15. In group A, stainless steel K-files #10, #15, #20, and #25 were used as a patency file. In group B, a stainless steel K-file #10 followed by nickel-titanium K-files #15, #20, and #25 were used as in group A. Sodium hypochlorite was used as the irrigating solution. Photographic slides of the apical foramen of each specimen before instrumentation and after the use of each file size were taken. The photographic slides of each specimen were mounted in slide mounts, projected onto the same drawing paper, and superimposed according to the peripheral shape of the root. Transportation of the apical foramen was determined comparing the five drawings of each specimen. Transportation was detected in 18 of the 30 specimens; 9 in group A and 9 in group B. No statistically significant differences were seen between groups (p = 1.00).

Dental Alloys↗

PubMed2005

An in vitro comparison of the rake angles between K3 and ProFile endodontic file systems.

The purpose of this study was to compare rake angles of the ProFile and K3 file systems. Twenty-five 40/0.06 taper files were obtained for each system. Five files from the same manufacturer were placed perpendicularly into a vial of Epoxicure Resin and left to set for 24 h. The set-ups were removed from the vials and each were sectioned 5 mm from the tip of the files and polished. A photomicrograph was taken of each file with 100x magnification. Five sets of ProFile and five sets of K3 files were processed in this manner. Images were captured digitally, and rake angles of each file were measured. Multivariate ANOVA found a significant difference (p < 0.001) among the three negative rake angles of the ProFile system compared with the K3 system.

Dental Instruments↗

PubMed1989

Oscillatory pattern of sonically powered endodontic files.

When operated in air, the sonic endodontic instrument produced a movement at the driver head which resulted in a large elliptical oscillation of the file. This motion had similar properties to ultrasonically operated files in that there was a distinct variability in the magnitude of the vibratory motion between files of different design, length and thickness. When the sonic file was loaded, the elliptical motion was eliminated leaving a pure longitudinal file oscillation. This mode of vibration was particularly efficient as it was largely unaffected by loading, with the displacement amplitude being similar for different types of file used. The oscillatory pattern of the sonic file may offer a useful mode of mechanically assisted root canal preparation.

Root Canal Therapy↗

PubMed1996

A comparison of stainless steel and nickel-titanium K-files in curved root canals.

The purpose of this study was to determine the effects of hand instrumentation using traditional stainless steel K-files and nickel-titanium K-files on the final shape of curved root canals. A total of 24 moderately curved canals in the mesial roots in extracted human mandibular first molars were randomly divided into two groups. These were instrumented manually using either stainless steel or nickel-titanium, K-files with the stepdown technique. The cross-sectional shape of each canal at three different horizontal levels were captured, before and after instrumentation, into a computer for comparison using image analyser software. Three parameters at each level were evaluated: (i) amount of dentine removed; (ii) least remaining dentine thicknesses on mesial and furcal aspects; and (iii) the amount and direction of canal transportation. The results showed that the two file types removed similar amounts of dentine at all three levels examined. The nickel-titanium files left a thicker layer of dentine on both the mesial and furcal aspects than stainless steel files. However, the difference was not significant (pooled T-test, P > 0.05). Both types of files transported the centre of the canals but the nickel-titanium instrument seemed to be safer because of the reduced amount of transportation towards the danger areas.

Dental Instruments↗

PubMed2006

Ex vivo study of the efficacy of H-files and rotary Ni-Ti instruments to remove gutta-percha and four types of sealer.

AIM: To compare the efficacy of ProFile rotary Nickel-Titanium (Ni-Ti) instruments and Hedstroem-files (H-files) combined with Gates-Glidden (GG) drills during removal of gutta-percha root fillings used in combination with one of the four representative sealers. METHODOLOGY: Forty-eight single-rooted human teeth, with fully formed apices and straight root canals were used. The root canals were accessed and instrumented using a stepback technique with H-files. They were randomly assigned to four groups and subsequently filled with a combination of lateral and vertical condensation of gutta-percha and one of the following sealers: Roth 811, AH26, Endion and Roekoseal. The root fillings were removed 1 year later, using either H-files in combination with GG drills or the ProFile Ni-Ti system. Teeth were then grooved longitudinally and split. The amount of gutta-percha and sealer remaining on the root canal walls was traced and scored visually with the aid of a stereomicroscope. The scores were analysed and statistically compared with the Kruskal-Wallis test between the ProFile and H-file groups, as well as among the four sealer subgroups. Two samples from each group were studied under the scanning electron microscope to enhance inspection of canal walls and remaining material. RESULTS: Sealer remnants were observed with both techniques mainly in the middle and apical third of the root canal. The ProFile system and the H-files were associated with similar amounts of remaining filling material (P > 0.05). In the cervical third of the root canal all sealer remnants were removed with both techniques. In the middle and apical third AH26 was associated with a statistically significant greater quantity of remnants on the root canal walls with both removal techniques (P < 0.05). Endion, Roth 811 and Roekoseal were associated with approximately the same amount of filling material in the middle third of the root canal (P > 0.05), whereas in the apical third Endion was associated with significantly more remnants of filling material than the other two sealers with either ProFile or H-files (P < 0.05). CONCLUSIONS: None of the methods used for the removal of root fillings was totally effective, especially in the apical third of the root canal.

Dental Cements↗

PubMed1994

Relationship between file size and stiffness of stainless steel instruments.

The purpose of this study was to evaluate the relationship existing between file size and stiffness for three endodontic files of different cross-sections. Three groups of instruments were tested: Flexofiles from the Maillefer company, K Files and K-Flex from the Kerr company. Flexofiles have a triangular cross-section, K Files a square cross-section, and K-Flex instruments a rhombus cross-section from size 15 to size 40. For each group, 10 files from size 15 to size 40 were compared according to ANSI/ADA specification N degrees 28 for bending moment evaluation. There was a statistical difference between the three groups: the square cross-section K files presented a larger bending moment than the rhombus cross-section K Flex, which presented a higher bending moment than the triangular cross-section Flexofiles. There was an exponential relationship between file size and bending moment.

Analysis of Variance↗

PubMed1996

Cutting efficiency of K-files manufactured with different metallic alloys.

The aim of this study was to compare, in vitro, the machining efficiency of different triangular cross-section K-files made of nickel titanium (Nitiflex, Naviflex), titanium (Microtitane), and stainless steel (Flexofile, Flex-R). Ten instruments of each K-file from size 25 to 40 were tested. The cutting efficiency was assessed in a linear motion using an indentation caliper to measure the depth of grooves. The load applied (in grams) was equal to the ISO file size. Each file was allowed to do 100 back-and-forward movements. Files made of stainless steel were the most effective, in particular Flexofile. There were statistically significant differences between Flexofile and Flex-R in all sizes. In the group of nickel titanium instruments, Nitiflex was significantly more efficient than Naviflex in all sizes. The machining ability of titanium files was higher than that of Naviflex but lower than that of Nitiflex and stainless steel files.

Alloys↗

PubMed1997

A comparison of dentine removal using safety or conventional Hedstrom files.

Mandibular molars (n = 20) were divided and the mesial roots mounted in an acrylic mould which allowed them to be removed, sectioned horizontally and then reassembled. The furcal root canal wall thickness 7 mm from the apex was measured prior to instrumentation. The roots were allocated to two groups (n = 10). One group was instrumented using the step back technique with safety Hedstroms in one canal and conventional Hedstrom files in the other canal. The second group was instrumented using a crown down approach (using files and Gates Glidden drills to provide early radicular access). The furcal root canal wall thickness was then remeasured and the amount of dentine removed calculated. The results showed that the safety Hedstrom file removed less dentine from the furcal region of the canal compared to the conventional Hedstrom file. This however was not statistically significant (Paired t test, n = 10, p > 0.05). The amount of dentine removed using the crown down technique was significantly greater than that using the step back technique (Two sample t, n = 20, p < 0.01). In conclusion, less dentine was removed from the furcal region with safety Hedstrom files compared to conventional Hedstrom files; however, Gates Glidden drills removed more dentine than either type of hard file.

Dental Instruments↗

PubMedDate not supplied

Image file formats: past, present, and future.

Despite the rapid growth of the Internet for storage and display of World Wide Web-based teaching files, the available image file formats have remained relatively limited. The recently developed portable networks graphics (PNG) format is versatile and offers several advantages over the older Internet standard image file formats that make it an attractive option for digital teaching files. With the PNG format, it is possible to repeatedly open, edit, and save files with lossless compression along with gamma and chromicity correction. The two-dimensional interlacing capabilities of PNG allow an image to fill in from top to bottom and from right to left, making retrieval faster than with other formats. In addition, images can be viewed closer to the original settings, and metadata (ie, information about data) can be incorporated into files. The PNG format provides a network-friendly, patent-free, lossless compression scheme that is truly cross-platform and has many new features that are useful for multimedia and Web-based radiologic teaching. The widespread acceptance of PNG by the World Wide Web Consortium and by the most popular Web browsers and graphic manipulation software companies suggests an expanding role in the future of multimedia teaching file development.

Computer-Assisted Instruction↗

PubMed2005

Influence of cervical preflaring on determination of apical file size in maxillary premolars: SEM analysis.

The purpose of this study was to investigate the influence of cervical preflaring on the determination of the first file that binds at working length (WL) in buccal roots of maxillary premolars. Five groups (n=10) were formed at random and, after standard access cavities, the WL was determined 1 mm short from the apex. In group 1, the initial apical file was inserted without preflaring of cervical and middle thirds of the root canals. In groups 2 to 5, the cervical and middle thirds were enlarged with sizes 90 and 110 Gates-Glidden drills, K(3) Orifice Opener instruments, ProTaper instruments and LA Axxess burs, respectively. Canals were sized manually with K-files, starting with No. 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 instrument was recorded. Transversal sections of the WL regions were examined under scanning electron microscopy and the discrepancies between the canal diameter and first file to bind at the WL were assessed. Significant differences (p<0.001) were found between the groups. The major discrepancy was found without preflaring (mean 157.8 microm). LA Axxess burs produced the smallest discrepancy (mean 0.8 microm). Gates-Glidden drills and K(3) Orifice Opener instruments showed no significant differences (p>0.05) between their results (83.2 microm and 73.6 microm, respectively). The discrepancy for ProTaper instruments was 35.4 microm on average. In conclusion, the instrument binding technique for determination of the anatomical diameter at the WL was not precise. Preflaring of the cervical and middle thirds improved the determination of the anatomical diameter at the WL, and the type of instrument played a major role. Canals preflared with LA Axxess burs showed a more accurate binding of the files to anatomical diameter.

Analysis of Variance↗

PubMed2006

Effectiveness of rotary and hand files in gutta-percha and sealer removal using chloroform or chlorhexidine gel.

The purpose of this study was to assess in vitro the efficacy of nickel-titanium K3 rotary files and hand files for removal of gutta-percha and sealer from obturated root canals using either chloroform or chlorhexidine as solvents. Sixty extracted single-rooted bovine teeth with straight, large canals were prepared, obtured and randomly assigned to 3 groups (n=20). The teeth were stored at 37 degrees C for 1 month and then the gutta-percha and sealer were removed using different techniques, as follows. Group I: size 3 Gates-Glidden drills plus size 30 hand K-files and Hedström files and chloroform; Group II: K3 NiTi rotary files and chloroform; and Group III: K3 NiTi rotary files and 2% chlorhexidine gel. Radiographs were taken and scanned and the images were digitized. The total area of the canal and the area with remaining obturation material were measured in millimeters using a computed image analysis system (ImageLab). Data were analyzed statistically by one-way ANOVA and Tukey test at 5% significance level. The groups differed statistically (p<0.05) with respect to the average percentage of remaining gutta-percha and sealer, presenting the following sequence of effectiveness (from most to least effective): Group I (15.48%), Group II (28.42%) and Group III (35.96%). The findings of this study showed that, despite the technique used for removal of filling material, none of the retreated canals were completely free of gutta-percha and sealer remnants. The use of stainless steel hand files resulted in a lesser amount of filling debris than the use of nickel-titanium rotary instruments.

Animals↗

PubMedDate not supplied

Design and implementation of a World Wide Web teaching files database on diagnostic radiology.

INTRODUCTION: The aim of this project was to demonstrate the feasibility and effectiveness of a teaching files database on diagnostic radiology accessible via the Internet and the World Wide Web. The Italian experience in developing a national database named "RadioDB" is presented. MATERIALS AND METHODS: "RadioDB" is sponsored by the Italian Society of Radiology (SIRM) and is based on a multicenter academic collaboration. It constitutes a collection of multimedia case record and teaching files. "RadioDB" is based on a Pentium workstation running a Structured Query Language (SQL) database and a World Wide Web server. Each case record contains at least one radiological image and a text file for case comment with key words and codes from the American College of Radiology (ACR). In most cases, a complete teaching file is also available. Peer reviewed teaching files available on this server are contributed via anonymous file transfer protocol (FTP) through the Internet from various Italian academic Departments of Radiology. RESULTS: Worldwide users can easily access and search "RadioDB" database through a World Wide Web query interface and retrieve on-the-fly case record and teaching files. Users can search the database by author name, description, key words, free text or ACR codes. CONCLUSIONS: "RadioDB" enlarges the base of current off-line educational materials offering and it allows radiologists to improve their medical education.

Education, Medical, Continuing↗

PubMed1993

Perioperative deaths--detection by linkage of hospital discharge and death registration sub-files.

In support of the extension of the National Confidential Enquiry into Perioperative Deaths to Scotland, and in view of increased interest in the use of such deaths as clinical outcome measures in the setting of service contracts, methods have been developed employing the national Hospital Discharge (SMR1) file and Registrar General's Death Registration file on a local microcomputer for the identification of patients who die within 30 days of an operation. Direct interrogation of the SMR1 file for individual records containing both an operation date and date of death yields only those patients who die prior to discharge or transfer. Since in our study these accounted for only 52% of the total perioperative deaths, this may explain previous disillusionment with the potential of computer systems for their identification. By creating each month a SMR1 sub-file of patients having operations and linking this to a second sub-file containing the records of all patients dying in hospital, it was found that 32% of deaths occurred following transfer to a different specialty or hospital, and 8% on re-admission following discharge home. On linking the SMR1 operation sub-file to the death registration file, 8% of the total perioperative deaths were shown to have taken place outside hospital.

Adult↗

PubMed1996

[Optimal protocol for 99mTc-tetrofosmin myocardial SPECT imaging with exercise or dipyridamole stress test and the characteristics of bullseye normal file].

To determine optimal protocol for 99mTc-tetrofosmin SPECT imaging, 30 normal volunteers underwent treadmill or dipyridamole stress test with 770 MBq of tetrofosmin injection. Anterior planar images were acquired every 10-15 minutes for calculating heart/liver ratio. SPECT images were also obtained every 30 minutes for generating Bullseye normal files. In analysis of spatial tracer distribution among normal files, myocardium in Bullseye plot was divided in 9 areas, where mean values of % tracer uptake were calculated and compared by analysis of variance (ANOVA). In those 9 areas, mean values of SD (SD mean) were also compared for predicting artificial blackout in the Bullseye plot among 3 standard normal files: dipyridamole-201Tl, dipyridamole-tetrofosmin (60 min post-injection), and treadmill-tetrofosmin (30 min post-injection). In planar image analysis, high initial uptake in the liver and its acceptable clearance were noted in dipyridamole stress test. Adequate heart/liver ratio was accomplished immediately after treadmill, but 40 minutes later after dipyridamole stress test. ANOVA analysis showed no statistical difference in the spatial % tracer uptake among normal files, irrespective of time after acquisition, data collection time, or difference of tracer. However, SD means in inferior and lateral area of treadmill-tetrofosmin file were significantly small compared to that of dipyridamole-201Tl normal file (p < 0.02 by ANOVA). Thus, we conclude that optimal timing for tetrofosmin SPECT imaging is immediately after treadmill, but at least 40 minutes after dipyridamole stress test. In addition, we should also keep in mind that unexpected blackout may appear in inferior and lateral area, when applying our normal files for reference.

Analysis of Variance↗

PubMed1997

Horizontal wires replace the vertical files.

Traditionally, clippings of newspaper articles, pictures from magazines, pamphlets, charts, graphs, posters, proceedings, or copies thereof, and other miscellaneous information sources have been stored in vertical files in libraries. The practice of creating and maintaining vertical files is extremely time consuming. In a medical library, in particular, old information about diagnosis, treatment, and prognosis can quickly become incorrect, misleading, and possibly harmful. Adequately tending to the vertical files can require a librarian to create a balancing act between properly maintaining vertical files and meeting the needs of the users in other areas of the library. The maintenance of vertical files is, by nature, highly consumptive of paper and space consuming. A reasonable alternative to the traditional vertical files is the World-Wide Web. Search engines exist for locating specific information, and bookmarks and/or links which point users to particularly useful sites can be set in search software. Some methods for searching are discussed, and a variety of World-Wide Web information sources are offered.

Computer Communication Networks↗