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At least 109 records · Page 6Linked to original sources

PubMed1989

Dentine-removing characteristics of an ultrasonically energized K-file.

This in vitro study evaluated the pattern of dentine removal when an ultrasonically energized file (Cavi-Endo-size 25 file) was applied to flat surfaces of dentine under standardized conditions. The influences of power setting, interfacial force between file and dentine, direction of file oscillation and operator-assisted movement were examined. Impressions of the instrumented surfaces revealed characteristic patterns consisting of a series of oblique crests, each one parallel to the next and separated by a constant distance along the line of contact with the file. Determination of height, width and separation of these crests with a Reflex microscope aided objective assessment. The simplest pattern was formed when the energized file was held against the dentine (power setting = 1; interfacial force = 30 g). Increasing the power setting to 8 caused deeper troughs over the apical 5 mm. The width of the crests corresponded to the taper of the file except at the apical tip where the crests were relatively wider. However, increasing the interfacial force to 60 g reduced the efficiency of the apical part of the file. The superimposition of operator-induced movement greatly increased the extent of dentine removal, resulting in a tapering groove with a persistent crestal pattern. Oscillation of the file perpendicular to the dentine surface had a significantly greater influence on dentine removal, producing a deeper groove than was obtained with oscillation parallel to the surface. These findings may be of relevance in aiding controlled root canal preparation when using the Cavi-Endo instrument.

Dental Cavity Preparation↗

PubMed1994

Efficacy of sterilization of endodontic files after autoclaving in a synthetic sponge.

A common way of sterilizing endodontic files for clinical use is to insert them into synthetic sponges. The files are sterilized in the sponge, and the sponge is then used on the patient tray for ease of file retrieval. The ability to sterilize the files in a sponge has been questioned. The purpose of the present investigation was to evaluate the sterility of files and spore strips following autoclaving in a sponge. Commercial spore strips and contaminated endodontic files were inserted into sponges, sealed in sterilization pouches and autoclaved. The spore strips and the files were removed from the sponge and cultured for growth of microorganisms. Results show that no microbes were cultured from spore strips or contaminated files after autoclaving them in the sponges sealed in autoclave pouches. These results indicate that the insertion of files into the sponges used in this study does not obstruct the autoclaving process.

Colony Count, Microbial↗

PubMed1996

Factors affecting the cutting ability of sonic files.

The aim of this study was to investigate the cutting ability of sonic files. A model system was developed and the following variables evaluated: file type. Heliosonic or Shaper; file length, 21 or 29 mm; power, air inlet ring opening of half or fully open; stroke length, 2 or 4 mm; stroke rate, one or two cycles per second; and load 50 or 100 g. A 2(6) full-factorial analysis with two replications into the effect of the above variables on the cutting ability of the MM1500 sonic instrument was performed. A new size 25 file was used for each cut, together with water irrigation, and the substrate used was 1-mm thick sections of bovine bone. The differences between the variables were significant (ANOVA, P < 0.001). However, examination of the F-values showed that the most significant variable to affect cutting was load, followed by power, file type, stroke length and stroke rate, with the least significant variable being file length. The most significant interaction was between rate and length of stroke. An increase in stroke rate from one to two cycles per second at a stroke length of 2 mm produced an increase in cutting for both the Heliosonic and Shaper files. However, at the longer stroke length of 4 mm, the same increase in rate resulted in a decrease in cutting for the Shaper files. Therefore, it is suggested that operators should press the file against the canal wall and move it slowly to maximise cutting.

Analysis of Variance↗

PubMed2005

Influence of cervical preflaring on apical file size determination.

AIM: To investigate the influence of cervical preflaring with different instruments (Gates-Glidden drills, Quantec Flare series instruments and LA Axxess burs) on the first file that binds at working length (WL) in maxillary central incisors. METHODOLOGY: Forty human maxillary central incisors with complete root formation were used. After standard access cavities, a size 06 K-file was inserted into each canal until the apical foramen was reached. The WL was set 1 mm short of the apical foramen. Group 1 received the initial apical instrument without previous preflaring of the cervical and middle thirds of the root canal. Group 2 had the cervical and middle portion of the root canals enlarged with Gates-Glidden drills sizes 90, 110 and 130. Group 3 had the cervical and middle thirds of the root canals enlarged with nickel-titanium Quantec Flare series instruments. Titanium-nitrite treated, stainless steel LA Axxess burs were used for preflaring the cervical and middle portions of root canals from group 4. Each canal was sized using manual K-files, starting with size 08 files with passive movements until the WL was reached. File sizes were increased until a binding sensation was felt at the WL, and the instrument size was recorded for each tooth. The apical region was then observed under a stereoscopic magnifier, images were recorded digitally and the differences between root canal and maximum file diameters were evaluated for each sample. RESULTS: Significant differences were found between experimental groups regarding anatomical diameter at the WL and the first file to bind in the canal (P < 0.01, 95% confidence interval). The major discrepancy was found when no preflaring was performed (0.151 mm average). The LA Axxess burs produced the smallest differences between anatomical diameter and first file to bind (0.016 mm average). Gates-Glidden drills and Flare instruments were ranked in an intermediary position, with no statistically significant differences between them (0.093 mm average). CONCLUSIONS: The instrument binding technique for determining anatomical diameter at WL is not precise. Preflaring of the cervical and middle thirds of the root canal improved anatomical diameter determination; the instrument used for preflaring played a major role in determining the anatomical diameter at the WL. Canals preflared with LA Axxess burs created a more accurate relationship between file size and anatomical diameter.

Analysis of Variance↗

PubMed1995

Relationship between file size and stiffness of nickel titanium instruments.

The purpose of this study was to evaluate the relationship existing between file size and stiffness for 3 endodontic files made of nickel titanium. Three groups of instruments with different cross-sections were tested: a triangular cross-section, a square cross-section and a modified triangular cross-section. The instruments were tested from size 15 to size 40 or 60 according to ANSI/ADA specification no. 28 for binding moment evaluation. There was a statistically significant difference between the 3 groups: the square cross-section K files presented a larger bending moment than the triangular cross-section K files, which presented a larger bending moment than the modified cross-section K files. Like the stainless steel instruments, there was an exponential relationship between file size and bending moment for triangular and square cross-section K files, but a linear relationship between file size and bending moment for the files with a modified triangular cross-section.

Analysis of Variance↗

PubMed2006

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

The purpose of this study was to investigate the influence of cervical preflaring on determination of the initial apical file in mesiobuccal roots of maxillary molars. Fifty first molars with degree of curvature of the mesiobuccal root between 10 degrees and 15 degrees were utilized. After standard access opening and removal of pulp tissue, the working length (WL) was determined at 1 mm from the root apex. Five groups (n=10) were formed at random, according to the type of cervical preflaring performed. In group 1, the size of the initial apical file was determined without cervical preflaring. In groups 2 to 5, the cervical and middle thirds of the canals were preflared with Gates-Glidden drills, K3 Orifice Opener instruments, ProTaper instruments and LA Axxess burs, respectively. Canals were sized manually with K-files, starting with size 08 K-files, inserted passively up to the WL. File sizes were increased until a binding sensation was felt at the WL and the size of the file was recorded. The binding instruments were fixed into the canals at the WL with methylcyanacrylate. Cross-sections of the WL region were examined under scanning electron microscopy and the discrepancies between the canal diameter and the diameter of first file to bind at the WL were calculated using UTHSCSA ImageTool software. Data were analyzed statistically by ANOVA and multiple comparisons were done by Tukey's HSD post-hoc test. Significant differences (p<0.001) were found among the groups. The major discrepancy was observed for the group without preflaring (mean 0.1543 mm +/- 0.0216). Cervical preflaring with LA Axxess burs produced the least discrepancies between the canal size and the diameter of the initial apical instrument (mean 0.026 mm +/- 0.0037), followed by ProTaper files (mean 0.0567 mm +/- 0.0354). Canals preflared with Gates-Glidden drills and K3 Orifice Opener instruments showed statistically similar discrepancy results to each other (p>0.05) (means 0.1167 mm +/- 0.0231 and 0.1313 mm +/- 0.0344, respectively). In conclusion, preflaring of the cervical and middle thirds improved the determination of the initial apical instrument. Canals preflared with LA Axxess burs showed a more accurate binding of the files to the anatomical diameter at the WL in the mesiobuccal roots of maxillary first molars.

Cyanoacrylates↗

PubMed1989

A proposed standard data file format for hyperthermia treatments.

One of the most critical areas of research essential to improve the clinical use of hyperthermia in cancer therapy is the determination and evaluation of temperature during therapy. In order to improve the dissemination of newly developed thermometry measurement and analysis programs and facilitate the transport of hyperthermia data files between computers for both intra- and inter- institutional use, we propose a standard file format, the Hyperthermia Data Standard (HDS), which can be used for all hyperthermia data. This data file consists of segments of which nine have been defined. The first is an initial /VERSION segment which identifies the file standard. This is followed by eight major segments: 2) a /IDENT segment which contains file and patient identification information; 3) a /TEXT segment containing additional miscellaneous documentation; 4) a /TUMOR segment which provides tumor and treatment site information; 5) a /HSETUP segment which contains treatment setup information; 6) a /FORMAT segment which defines the data segment structure; 7) a /DATA segment containing the actual thermometry data; 8) a /FOLLOWUP segment for documenting patient response; and 9) an /ANALYSIS segment containing summary information. All segments begin and end with a specified delimiter and, except for the first two (/VERSION and /IDENT), may be repeated more than once. For ease in debugging and verifying adherence to the standard, all information in the file is encoded in printable ASCII characters. All segments consist solely of records containing KEYWORDS and KEYWORD VALUES which identify specified information. Certain KEYWORDS are standard, i.e., having specified names and information formats as defined in this document. The /DATA segment consists of ASCII encoded chronological treatment thermometry and other data whose format and structure is identified in the /FORMAT segment. The /ANALYSIS segment provides the flexibility to store the results of any analysis program along with the actual data file for ease of data management. This thermometry data file standard is designed to provide both flexibility and extendability for all possible forms of hyperthermia treatment data. Furthermore, it is designed to provide a simple format which may be easily read by higher level languages. This document is intended for commercial manufacturers and others who are writing programs to document clinical hyperthermia treatments with the intention that they either use this format for their data storage or provide a means to convert their data into this format.(ABSTRACT TRUNCATED AT 400 WORDS)

Body Temperature↗

PubMed1993

Variations in the size of the ischemic myocardium due to differences in the normal file.

The myocardial thallium concentration is different during pharmacologic than exercise stress testing due to differences in coronary blood flow and cardiac output. These differences may affect the quantitative measurement of the size of ischemic myocardium if a stress-specific normal file is not used. This study examined this concept in 34 patients with isolated left anterior descending coronary artery disease. All patients underwent tomographic thallium imaging during adenosine infusion (140 micrograms/kg/min for 6 minutes). The size of the ischemic myocardium was measured from the polar map using two different normal files; one derived from normal subjects undergoing treadmill exercise testing, and the second from normal subjects undergoing adenosine stress testing. The extent perfusion abnormality was 19 +/- 13% using the exercise file, and 11 +/- 10% using adenosine file (difference; 8.1 +/- 1.6%, P = 0.0001), the severity score was 580 +/- 480 using exercise file, and 310 +/- 310 using the adenosine file (P < 0.001). The differences were present in the 20 patients with moderate stenosis (50 to 70% diameter stenosis); 17 +/- 10% versus 7 +/- 7% (P = 0.001), and in the 14 patients with severe stenosis (> 70% diameter stenosis); 24 +/- 16% versus 18 +/- 10% (P = 0.03). Thus, stress-specific normal file should be used for sizing the perfusion abnormality. The use of exercise file overestimates defect size in patients undergoing pharmacologic stress testing.

Adenosine↗

PubMed1990

Information retrieval for teaching files: a preliminary study.

A computer algorithm for information retrieval from an electronic teaching file has been developed. This index enables the user to retrieve cases from a teaching file, based on the input of a combination of features. The algorithm is based on nearest neighbor analysis, and is programmed in the "C" language. A teaching file with this index is very easy to use as a reference resource for diagnosing unknown cases. A model was developed for a preliminary test of how likely a user would be to review a teaching file case that is the same diagnosis as an unknown case, thereby reducing uncertainty of diagnosis. The model used 110 cases of arthritis radiographs of hands scored by a skeletal radiologist. The result of the model suggests that the correct diagnosis would be reviewed 83% of the time. A standard method of reducing uncertainty of diagnosis (the maximum likelihood discriminant function) would have picked the correct diagnosis 78% of the time. The results indicate that a teaching file with the computer index is a practical tool for dealing with the uncertainty in diagnosis of unknown cases. The computer index could be included with videodisc-based teaching files (such as the American College of Radiology files). Using teaching files as a reference for interpreting unknown cases may reduce interobserver variability.

Algorithms↗

PubMed1985

An outcome-coded birth file from machine readable vital records.

We developed a computer program which generates an outcome-coded birth file from a standard birth file and a matched birth-infant death file. This program uses only anonymous computerized vital records of the kind available to researchers in most states. Despite a large population (Illinois 1977 births totaled 178,728) all death records were uniquely matched with birth records, allowing creation of the desired file. Such a file permits the researcher to use a variety of standard software packages without the problems of data re-entry or the use of multiple input files. Creating this outcome-coded file is relatively inexpensive, can be done without enlisting special assistance from state vital records personnel, does not require access to restricted files, and greatly streamlines use of perinatal vital records for research applications, especially multivariable modeling.

Birth Certificates↗

PubMed2006

Microbial contamination of endodontic files received from the manufacturer.

This study was conducted to test the sterility of new unused endodontic files received from manufacturers. Fifteen types of hand and rotary files from five manufacturers were tested. Positive microbial cultures were obtained from 13% of the 150 files tested. Autoclaved files were intentionally contaminated with bacterial species recovered from the positive cultures to evaluate a chairside sterilization method. Immersion of contaminated files in 5.25% sodium hypochlorite for five minutes sterilized the files. The results of this study indicate that endodontic files should be sterilized before clinical use. It is also suggested that manufacturers list the sterility state of their endodontic files on their packaging.

Bacillaceae↗

PubMed2006

Cyclic fatigue of three types of rotary nickel-titanium files in a dynamic model.

The cyclic fatigue resistance of three types of nickel-titanium rotary files was compared in a model using reciprocating axial movement. The influence of file size and taper was also investigated and fracture patterns were examined under SEM. The 10 experimental groups consisted of ProFiles, K3s, and RaCe files, size 25 in .04 and .06 tapers, as well as ProFiles and K3s, size 40 in .04 and .06 tapers. Each file was rotated freely at 300 rpm inside a stainless steel tube with a 60 degree and 5 mm radius of curvature. A continuous 3 mm oscillating axial motion was applied at 1 cycle per second by attaching an electric dental handpiece to the most inferior load cell of an Instron machine using a custom-made jig. The number of rotations to failure was determined and analyzed using analysis of variance and Tukey's post hoc tests. Overall, K3 25/.04 files were significantly more resistant to cyclic fatigue compared to any other group in this study. In the 25/.04 category, K3s were significantly more resistant to failure than ProFiles and RaCe files. Also in the same category, ProFiles significantly outlasted RaCe files. In the 25/.06 group, K3s and ProFiles were significantly more resistant to failure than RaCe files, but K3s were not significantly different than ProFiles. In the 40/.04 and 40/.06 groups, K3s were significantly more resistant to cyclic fatigue than ProFiles. SEM observations demonstrated mostly a ductile mode of fracture. The results suggest that different cross-sectional designs, diameters, and tapers all contribute to a nickel-titanium instrument's vulnerability to cyclic failure.

Analysis of Variance↗

PubMed1995

A comparison of maintenance of canal curvature using balanced-force instrumentation with three different file types.

Forty-five extracted human molar teeth with curved facial or mesial canals were instrumented to a #45 file with three different file types using balanced-force (BF) instrumentation. Pre- and postoperative X-rays were taken, projected, and file location traced to determine the canal curvature according to the method of Schneider. Results showed statistically less reduction in canal curvature with nickel-titanium (NT) files compared with either Flex-R (FR) (p < 0.05) or K-Flex (KF) files (p < 0.0021). There was no significant difference comparing FR with KF files (p > 0.05). Under the conditions of this study, NT files used with the BF technique were significantly less likely to change canal curvature than either FR or KF files when instrumenting curved root canals.

Dental Pulp Cavity↗

PubMed1992

Effect of precurving endosonic files on the amount of debris and smear layer remaining in curved root canals.

Endosonic files are prone to constraint; this reduces their efficiency, particularly in the apical third and in curved root canals. Precurving the file may reduce constraint, thereby improving the file's ability to debride. This investigation was undertaken to compare both straight and precurved endosonic files as to debris and smear layer removal. Thirty-six curved root canals were randomly allocated into six groups. Each group was prepared using a step-down technique, then instrumented with either a straight or precurved endosonic file of size 15, 20, or 25. The tooth roots were split and examined under the scanning electron microscope. Blind examinations were made for debris and smear layer removal and evaluation scores were analyzed using a log linear approach. The root canals instrumented with the precurved files had a significantly lower debris score than those prepared with straight files. Precurving did not affect smear layer removal. In conclusion, precurving of files decreased the amount of debris but did not affect smear layer removal.

Dental Cavity Preparation↗

PubMed1990

Torsional properties of twisted and machined endodontic files.

The torsional properties of conventionally twisted K-type endodontic files and recently developed machined K-type endodontic files were compared. File sizes 10 through 40 were subjected to torsional load in clockwise and counterclockwise directions independently. Results showed that a statistically significant reduction in clockwise rotation occurred at failure with all of the machined files except size 10. Counterclockwise rotation at failure was also significantly lower for the machined files in sizes 10 through 30. There was no difference in torsional strength between the file types regardless of rotation direction. Therefore, machined files exhibit less ductility than twisted files prior to fracture and may be more susceptible to torsional failure clinically.

Dental Stress Analysis↗

PubMed1998

Comparison of debris extruded apically in straight canals: conventional filing versus profile .04 Taper series 29.

The purposes of this study were to determine quantitatively the amount of debris and irrigant forced in an apical direction, the frequency of apical plug development, and the time required to prepare canals when a step-back technique using K-files was compared with the .04 Taper system. Sixty-nine extracted teeth with straight canals were divided into four statistically similar groups. Two groups were instrumented either 1 mm short of the apical foramen or to the apical foramen with K-files. The other two groups were instrumented to the same levels using .04 Taper files. The extruded debris and irrigant were collected in preweighed vials. The weight of the debris and volume of irrigant extruded using both techniques were compared and analyzed using paired t test and one-way ANOVA. Tukey's Multiple Comparisons Procedure showed K-files used to the apical foramen extruded significantly more debris than the other three groups (p < 0.01). The .04 Taper files used 1 mm short extruded less debris than the other groups. Significantly more irrigant was extruded when filing was performed to the apical foramen (p < 0.007), regardless of the technique used. More apical plugs were created in teeth filed short of the apical foramen, but the difference between the two preparation techniques was not statistically significant. It took significantly less time to instrument canals with the .04 Taper system than with K-files (p < 0.002).

Analysis of Variance↗

PubMed2005

Removal of methylated arsenic in groundwater with iron filings.

Field and laboratory experiments were conducted to study the potential use of Fe filings to remove monomethyl arsenate (MMA) and dimethyl arsenate (DMA) from contaminated waters. Batch experiments show that the affinity of MMAfor Fe filings is comparable to that of inorganic arsenate, but lower than that for arsenite. In contrast, very little DMA was retained by Fe filings or their corrosion products. The wide range of affinities of different As species for Fe filings was confirmed by a series of retention and selective-leaching experiments using small columns and As-spiked groundwater. The effectiveness of Fe filings was also demonstrated with a field deployment at a U.S. Superfund site where groundwater is highly contaminated with both organic and inorganic As species. Over the course of 4 months, a 3 L cartridge of Fe filings removed > 85% of As contained in 16000 L of groundwater containing 1-1.5 mg/L total dissolved As, approximately 30% of which was organic As. The results indicate that Fe filings could be used to treat groundwater contaminated with MMA, which is the main organic form of As at most contaminated sites. Indications of partial demethylation in the column of Fe filings suggest conditions might be optimized further to enhance the removal of DMA.

Arsenates↗

PubMed2001

The standardized-taper root canal preparation--part 6. GT file technique in abruptly curved canals.

AIM: To describe the application of GT files in roots with abrupt curvatures. SUMMARY: Most dentists interpret obstructions to instrument progress as calcification, rather than abrupt curvature. Basically, there are not any apically calcified canals, only clinicians who are not clever enough or patient enough to sneak to patency. Dentists should be on their guard and sensitive to the 'rubber band' sensation of residual pulp tissue, and the 'loose resistance' sensation of the curved or ledged canal. Residual pulp tissue should be removed and the canal lubricated. The ledged or curved canal will only be helped by file bending. The size 10 file test is the key to identify canals requiring pre-bent instruments. The canal should first be flared short of the obstruction, before shaping the canal after it with regular, pre-bent K-files. Pre-bent GT hand-files can then be used with care to blend the apical and more coronal regions for final shape. Cone-fit may then require chilling and pre-bending GP cones (pre-bend more than one), before packing the canal. KEY LEARNING POINTS: Root canals do not calcify apically. File progress is prevented by pulp tissue, abrupt curvatures or ledging. Loose resistance to the passage of a size 10 file shows the canals that require instrument pre-bending. This test should be repeated at intervals during the preparation. Even NiTi GT files can be pre-bent for use in abrupt curves. Gutta percha cones can be pre-bent after chilling.

Dental Pulp Cavity↗