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At least 55 records · Page 3Linked to original sources
PubMed1992

Comparison of six files to prepare simulated root canals. 1.

A total of 300 simulated root canals of various angles and positions of curvature in clear resin blocks were prepared by hand using either K-files, K-Flex files, Flexofiles, Flex-R files, Hedstrom files or Unifiles. Each file type was used to prepare 50 canals employing a linear filing motion and an anticurvature stepback technique. Part 1 of this two-part report describes the efficacy of the files in terms of preparation time, instrument failure, loss of canal length and weight loss from the blocks. Two-way analysis of variance confirmed that there was significant variation for each parameter between instruments, between canal types, and with interaction between instruments and canal types. Overall, preparation with Hedstrom files was significantly quicker than with any other file, whilst preparation with K-files and K-Flex files took significantly longer. Fracture and deformation of instruments occurred substantially less often with Flex-R and Hedstrom files, but significantly more often with Unifiles. Loss of working distance occurred with all file types, but was significantly greater in canals prepared with K-files. Unifiles and Hedstrom files were responsible for significantly more weight loss than the other files, whilst K-files produced significantly less weight loss. Canals with rough undulating walls were created most often by Hedstrom files and Unifiles. Overall, under the conditions of this study, Flexofiles, Flex-R files and Hedstrom files appeared to be substantially more effective than K-files, K-Flex files and Unifiles.

Analysis of Variance↗
PubMed2004

A new insight into the oscillation characteristics of endosonic files used in dentistry.

The aim of this study was to assess the oscillation characteristics of unconstrained endosonic files using a scanning laser vibrometer (SLV). Factors investigated included file vibration frequency and node/antinode location as well as the variation in file displacement amplitude due to increasing generator power setting. A 30 kHz Mini Piezon generator (Electro-Medical Systems, Switzerland) was used in conjunction with a #15 and #35 K-file. Each file was fixed in position with the long axis of the file perpendicular to the SLV camera head. The laser from the SLV was scanned over the length of the oscillating file for generator power settings 1 to 5 (minimum to half power). Measurements were repeated ten times. The fundamental vibration frequency for both files was 27.50 kHz. Scans of each file showed the positions of nodes/anti-nodes along the file length. The #15 file demonstrated no significant variation in its mean maximum displacement amplitude with increasing generator power, except at power setting 5, where a decrease in displacement amplitude was observed. The #35 file showed a general increase in mean maximum displacement amplitude with increasing power setting, except at power setting 4 where a 65% decrease in displacement amplitude occurred. In conclusion, scanning laser vibrometry is an effective method for assessing endosonic file vibration characteristics. The SLV was able to demonstrate that (unloaded) file vibration displacement amplitude does not increase linearly with increasing generator power. Further work is being performed on a greater variety of files and generators. Vibration characteristics of files under various loads and varying degrees of constraint should also be investigated.

Dentistry↗
PubMed2006

The effect of pre-soaking and time in the ultrasonic cleaner on the cleanliness of sterilized endodontic files.

AIMS: To assess whether pre-soaking files in an enzymatic cleaner prior to ultrasonic cleaning had any effect on cleanliness and also to assess the effect of the time that endodontic files spend in an ultrasonic bath prior to sterilization on their overall cleanliness. METHODOLOGY: Twenty root canals in a total of ten patients were cleaned and shaped using conventional techniques. Following use, some of the files were pre-soaked and then ultrasonically cleaned for either 5, 10, 30 or 60 min. Other files had no pre-soaking and were then ultrasonically cleaned. There were two control groups, one where the files were pre-soaked and not ultrasonically cleaned and the other where the files were neither pre-soaked nor ultrasonically cleaned. All files were then subjected to a standard packing and autoclaving process. Following autoclaving, the files were examined using a light microscope at a magnification of 40x. The cutting section of each file was divided into two parts, the tip and the shaft, for visualization under the microscope. Any debris or cement on the files was scored using a modification of the scale used by Smith et al. (Journal of Hospital Infection, 51, 2002, 233). The data were analysed using one-way analysis of variance. RESULTS: Pre-soaking had no significant effect on the cleanliness of the files (P = 0.18 at the tip, P = 0.93 at the shaft). Ultrasonic cleaning had a significant effect on the cleanliness of the files (P < 0.00) but there was not a linear relationship between cleanliness and the ultrasonic cleaning time. There was little benefit in extending the ultrasonic cleaning time beyond 5 min. Calcium hydroxide deposits on two files were resistant to ultrasonic cleaning. CONCLUSIONS: There is no benefit in pre-soaking endodontic files prior to ultrasonic cleaning. The optimum time for ultrasonic cleaning was between 5 and 10 min. Further ultrasonic exposure, up to 60 min, did not improve cleanliness. Although a majority of files were free from debris following ultrasonic cleaning, a substantial minority still retained debris. This supports the case for endodontic files being single-use only.

Calcium Hydroxide↗
PubMed2004

A comparative study of crack development in stainless-steel hedstrom files used with step-back or crown-down techniques.

The purpose of this study was to evaluate the effect of step-back (SB) and crown-down (CD) techniques on crack development of stainless-steel Hedstrom files (H-files). Ninety-seven mesial root canals of freshly extracted human mandibular molars were selected. Six sets of H-files (#15, #20, and #25 ISO size each) were used with SB and CD techniques for the chemomechanical preparation of 8, 16, and 24 root canals using 2.5% NaOCl as an irrigant and EDTA gel as a chelating agent. Files were sterilized in an autoclave between successive uses. A seventh unused set served as control. After macroscopic examination all files were embedded in epoxy resin, ground, polished, and studied under a metallographic microscope. The maximum crack size of each file was measured by means of standard image-analysis procedures. Macroscopically the files presented no signs of plastic deformation, apart from a file #15, used with SB technique, which fractured after 16 root-canal preparations. The microscopic examination showed no cracks: on control files, on files used with the CD technique for 8 and 16 cycles, on file #20 used with the SB technique for 8 and 16 cycles, as well as on file 25 used with the SB technique for 8 cycles. Cracks were found on H-file #15 used with the SB technique for 8 and 16 cycles, on file 25 used with the SB technique for 16 cycles, and on all files used for 24 cycles with both SB and CD techniques. Under the conditions of this study it was concluded that the instrumentation technique is deeply implicated in the crack development. Crack propagation was accelerated when SB technique was used.

Chelating Agents↗
PubMed1996

Electronic length measurement using small and large files in enlarged canals.

Electronic apex locators are frequently used attached to a small size endodontic file; however, the effect on the measurement of the relative diameters of the file and the root canal has not been clarified. In this study, the length of enlarged canals was measured using small size files and files matching the canal diameter to observe a possible discrepancy. The accuracy of electronic length control during canal preparation with rotary files was also assessed. The root canals in 21 extracted, single rooted teeth were accessed, and their actual length (AL) established by passing a size 10 file just through the minor apical foramen. The teeth were then embedded in an alginate mold. The initial canal length (IL) was measured with the Root ZX apex locator by negotiating a size 10 file to the apical constriction. The canal was enlarged to size 60 with rotary files while the length was continuously controlled with the apex locator. Then, the final length measurements were obtained with a size 10 file and a size 60 file (FL-10 and FL-60, respectively). The average values of IL, FL-10 and FL-60 were calculated and compared using Repeated Measures Analysis of Variance followed by Tukey's Studentized Range test (P < 0.05). Using composite resin, the size 60 files were secured at the FL-60 length, the teeth were removed from the alginate mold, stained with Picroformal DI Buoin stain and the position of the file tip was observed histomorphometrically after the apical 4 mm of the canal was exposed by grinding the buccal aspect of the root. The IL was 0.45 mm shorter than AL (P < 0.05). The differences between FL-10, FL-60 and IL were not statistically significant. Histomorphometrically, the apical constriction was absent in all the teeth, but the file tips were confined within the root. This study concluded that the Root ZX indicated the location of an apical constriction even when the anatomic constriction was eliminated. In the enlarged canals, length measurements obtained with small and large size files were comparable.

Analysis of Variance↗
PubMed2006

The effects of file size, sodium hypochlorite and blood on the accuracy of Root ZX apex locator in enlarged root canals: an in vitro study.

BACKGROUND: The initial electronic apex locator (EAL) length measurement is generally established with a small-sized file. It is not known whether file size would be interfering with the reading accuracy of the EAL. This study aimed to evaluate the effect of file size on the accuracy of Root ZX apex locator using an agar model when sodium hypochlorite solution or blood was present during electronic measurements in enlarged root canals. METHODS: A total of 36 extracted lower premolars were used. In stage 1, the canals were instrumented using size 10-40 K-files with a size 40 K-file as the master apical file (MAF). The teeth were then divided randomly into two groups of 18 teeth each. In group A, the teeth were mounted in one per cent agar and irrigated with six per cent sodium hypochlorite solution (NaOCl), while in group B the teeth were mounted in agar and irrigated with human blood. In stage 2, the canals were enlarged using a size 60 K-file as the MAF. In stages 1 and 2, the apical portions of the canals were instrumented using the step-back sequence (up to a size 80 K-file). In stage 3, the canals were enlarged using a size 80 K-file as the MAF. In each stage, the length was measured with a Root ZX until the meter value reached 'APEX' using small and large size files. RESULTS: Three-way ANOVA and Bonferroni test showed that file size, stage of preparation and type of irrigant all had a significant influence on the measurement error (P < 0.0001), with all the interactions between these three factors being significant (P < 0.0001). CONCLUSIONS: As the diameter of the root canal increased, the measured length with the smaller size files became shorter. A file of a size close to the prepared canal diameter should be used for root length measurement in the presence of blood. In the presence of NaOCl, the Root ZX was highly accurate even when the file was much smaller than the diameter of the canal. The agar model was effective and suitable for testing EALs in vitro.

Analysis of Variance↗
PubMed1995

A World-Wide Web radiology teaching file server on the Internet.

OBJECTIVE: Radiology departments have traditionally used film-based collections of interesting cases for teaching purposes. Film-based files are expensive to create and duplicate, and they physically occupy considerable space. As one solution to these problems, our department created an on-line radiology teaching file in digital format. MATERIALS AND METHODS: Our teaching file resides on a Macintosh Quadra 700 computer that is connected to the Internet, a worldwide network of interconnected computers, via our campus Ethernet network. Our digital teaching file images and text are composed in HyperText Markup Language (HTML) and are made available to the world with Webserver software known as MacHTTP. These teaching files are accessed using World-Wide Web (WWW) client software such as Mosaic, MacWeb, or Netscape. RESULTS: Our digital teaching file is available at no charge to anyone in the world with access to the Internet and WWW client software. Our radiology residents can access this file via several workstations in our department. Mosaic is an easy-to-use interface, and the use of our digital teaching file has increased significantly. In the 3 months since its creation, our teaching file has been accessed not only by our radiology residents but also by hundreds of other users in 33 countries. CONCLUSION: Use of Mosaic and the WWW format has resulted in an easy-to-use hypertext interface to the Internet, which allows even persons with little computer experience to navigate through the Internet, read text files, view images (stills and movies), and download files by merely pointing with the mouse and clicking on items of interest. This has allowed us to maintain a central teaching file that is physically small and easy to share with all the hospitals in our system. We invite the worldwide radiology community to access these files and to submit cases from their own teaching files to share with the rest of the world.

Computer Communication Networks↗
PubMed2005

The causes, prevention, and clinical management of broken endodontic rotary files.

Complications can occur during many dental procedures. The prepared clinician responds by either correcting the problem during treatment, or, ideally, preventing the problem from occurring in the first place. In endodontic treatment separated rotary Ni-Ti files are a common procedural problem. Through understanding that the main causes of file breakage are cyclic fatigue and torsional stress, a dentist can best prevent this occurrence by using hand files before rotary files, creating a straight-line (glide path) access into a canal, and preflaring the coronal portion before using rotary files in the apical third of the canal. In addition, using an up and down motion with the electric slow-speed handpiece (not allowing the file to bind within the canal) will significantly reduce the incidence of file breakage. If a file does break, successful removal primarily depends on the location of the file in the canal rather than the specific technique employed for removal. A case does not necessarily fail if the separated file cannot be removed. The prognosis when file separation occurs can still be favorable, especially if care was taken to reduce the critical concentration of canal debris with hand instrumentation and chemical irrigation prior to rotary file insertion. In addition, the introduction of a new CS file design will help the dentist increase the chance of removing the file in the event of breakage.

Dental Alloys↗
PubMed1998

Comparison of the performance of four files with rounded tips during shaping of simulated root canals.

A total of 160 simulated canals of various angles and positions of curvature were prepared by hand using either Mani Flexile Files, Mani SEC-O Files, Maillefer Flexofiles, or Zipperer Flexicut Files. After orifice enlargement, each file type was used to prepare 40 canals employing a balanced force motion and a modified double-flared technique. Pre- and postoperative images of the canals were taken with a videocamera, and stored and manipulated in a computer with image analysis software. The presence of canal aberrations and the amount of material removed as a result of preparation were determined from composite images of superimposed pre- and postoperative views. Significant differences (p < 0.001) in preparation time were observed, with Flexile Files being quickest and SEC-O Files being slowest. Overall, Flexofiles and Flexicut Files deformed significantly more (p < 0.001) than Flexile and SEC-O Files. The incidence of canal blockage was not influenced by instrument type, but the incidence of apical extrusion was significantly greater (p < 0.001) with SEC-O Files. SEC-O Files created significantly fewer (p < 0.001) and significantly narrower (p < 0.001) zips, with significantly less (p < 0.001) removal of material from the outer aspect of the curve and thus significantly less (p < 0.001) transportation. Flexicut Files created the widest canals apically, with the greatest removal of material from the outer aspect of the curve and the most transportation. Flexofiles created significantly more (p < 0.001) perforations. Under the conditions of this study, obvious differences between instruments were highlighted with SEC-O Files preparing canals more safely and with least destruction. The unique rounded tip of the SEC-O Files may have had an influence on the outcome.

Analysis of Variance↗
PubMed1994

Physical mechanisms governing the hydrodynamic response of an oscillating ultrasonic file.

Ultrasonically driven vibrating files are known to enhance the efficiency of root canal debridement. This paper presents a phenomenological view of the hydrodynamic response of an oscillating ultrasonic file and the relationship between the file response and various physical factors such as file size and curvature, file surface properties, file velocity amplitude, root canal geometry, and the type of irrigant. Relevant hydrodynamic properties include the propensity of a file to produce stable and transient cavitation, steady streaming, and cavitation microstreaming. These relationships were explored by experiment. Sonoluminescence was employed as an indicator of transient cavitation activity and photographic analysis was utilized as a means for detecting steady streaming, microstreaming, and stable cavitation. Measurements failed to indicate any strong correlation between registered driving power and the propensity to produce transient cavitation. Files that were pitted or possessed salient edges were very effective at generating transient cavitation. When observed, transient cavitation activity generally occurred near the tip of the straight file, provided the wall-loading did not inhibit file motion. In all cases studied, steady streaming and stable cavitation were observed to varying degrees, depending on the amount of file to wall contact. Stable cavitation was probably enhanced by the addition of moderate amounts of dissolved gas into the irrigant. Although the imposition of file-wall contact served to inhibit the production of transient cavitation, this action had relatively little effect on the ability of a file to produce a nominal level of streaming, microstreaming, and stable cavitation. The relationship between these hydrodynamic properties and the process of root canal debridement is addressed. Observations suggest that it is not prudent to ascribe enhanced cleaning effects to any one phenomenon, for it is likely that several factors are involved to varying degrees depending on the local conditions of application.

Luminescent Measurements↗