Hedstrom Files Research Articles

Efficacy, cleaning ability and safety of different devices for gutta-percha removal in root canal retreatment

The purpose of this study was to evaluate the efficacy, cleaning ability and safety of five different devices and techniques to remove gutta-percha root canal fillings. One hundred and twenty extracted single-rooted anterior and premolar teeth were enlarged to ISO size 35 and obturated with laterally condensed gutta-percha using AH 26 as the sealer. Removal of gutta-percha was performed with the following devices and techniques: (a) Gates-Glidden and Hedstrom files, (b) only Hedstrom files, (c) Hedstrom files and chloroform, (d) the Endotec and Hedstrom files, and (e) the XGP drill and Hedstrom files. The following data were recorded: time taken to reach the desired working length, time required for the removal of the gutta-percha, and the amount of material extruded apically. The teeth were split longitudinally and photographed. Cleanliness of the root canal walls was scored using the projected slides with a total magnification of approximately 70x. The fastest technique to reach the working length was using the XGP drill (e), followed by the Gates-Glidden drills (a), Hedstrom files and chloroform (c), and the Endotec device (d). The use of Hedstrom files (b) without any additional support proved to be most time-consuming. Differences were statistically significant (U-test, P > 0.05) between the rotary devices and the manual techniques. Time for complete removal of gutta-percha was again shortest with the XGP drills (e), followed by the Gates-Glidden burs (a), the Endotec device (d), Hedstrom files with chloroform (c), and Hedstrom files alone (b). The XGP burs and the Gates-Glidden drills worked significantly faster than the other techniques. The amount of debris and filling material extruded apically in most cases did not exceed 0.1 mg. No significant differences could be detected between the groups (U-test, P > 0.05). Root canal cleanliness proved best following the use of Hedstrom files without additional support (b) and the Gates-Glidden drills (a), followed by Hedstrom files in combination with chloroform (c), the XGP-gutta-percha remover (e), and the Endotec device (d). When using the XGP two instrument fractures occurred in the apical parts of the root canals preventing further instrumentation to the apical foramen. When using the Gates-Glidden burs four instrument fractures occurred, but all fragments could be removed with forceps immediately. The results suggest that the XGP gutta-percha remover and the Gates-Glidden drills are efficient and time saving devices to remove gutta-percha but include a certain risk of instrument breakage and may leave some filling material inside the root canal. The best root canal cleanliness was achieved with Hedstrom files alone which, on the other hand, were shown to be the most time-consuming.

Wear Resistance of Cryogenically Treated Stainless Steel Files

Cryogenic treatment, which involves ultra-sub-zero treatment of metal alloys, has been shown to improve the wear resistance of several types of stainless steel. The purpose of this study was to examine the effect of cryogenic treatment on wear resistance of Flex-R and Hedstrom (Union Broach) files. These instruments were attached to an Instron testing machine and underwent 300 push-pull strokes (6-mm movement range, 600-mm/min speed, 1-N loading) against 1.5-mm thick dentin wafers. Their wear was determined by comparing the depth of grooves (without changing file position) cut in acrylic specimens (1.5-mm thick) before and after machining dentin. The mean and standard deviation (n = 20) of the relative change in cutting efficiency was determined for the files. An analysis of variance showed that the cutting efficiency of all files decreased significantly after wearing on dentin (p < 0.0001). However, when comparing the post-/pre-cutting efficiency ratios of the files, it was seen that cryogenic treatment did not affect the wear resistance of the files.

A Comparative Scanning Electron Microscopic Investigation of the Efficacy of Manual and Automated Instrumentation of Root Canals

The cleaning effectiveness of automated and manual root canal instrumentation was investigated with the aid of a scanning electron microscope. Hand instrumentation was performed with K-Flexofiles used in a reaming working motion and according to the step-back technique and with Hedstrom files used in a filing motion. Automated preparation was performed with the KaVo-Endo Flash device featuring torque-limited rotation using K-Flexofiles, as well as with the mechanical ProFile system using rotary nickel-titanium instruments. Twelve teeth each with either straight or curved root canals were instrumented to size 40. After cracking the roots longitudinally (n = 120), the amount of debris and smear layer were quantified on the basis of a numerical evaluation scale (1 through 5). Comparison of manual instrumentation with the automated KaVo-Endo Flash resulted in an equivalent degree of canal cleaning. Complete cleanliness was not achieved by any of the techniques and devices investigated. Best instrumentation results, especially in curved canals, were obtained with rotary ProFile instruments.

An analysis of canal centering using mechanical instrumentation techniques

The purpose of this study was to compare canal transportation in moderately curved canals using mechanical instrumentation systems. Mesial roots of mandibular first or second molars were mounted in resin using a modified Bramante muffle system and divided into four groups. The roots were cross-sectioned 2 mm from the working length and at the height of root curvature. Tracings of the canal were made from preinstrumentation slides of the cross-sections. The canals were prepared using ProFile Series 29 rotary instruments, Quantec 2000 rotary instruments, Flex-R files in the Endo Gripper contra-angle handpiece, and Shaping Hedstrom files in the M4 contra-angle handpiece. Tracings of the prepared canals were made onto the originals from postinstrumentation slides. A canal centering ratio was calculated along the line of maximum transportation. Quantec 2000 rotary instruments yielded significantly greater transportation at the apical level when compared with the Profile Series 29 system. There were no other significant differences in transportation at either level. There were no differences in the direction of canal transportation between instrument systems, and the direction of canal transportation was not related to the direction of canal curvature. Canal preparation time was shortest with Profile Series 29 system followed by Flex-R files in the Endo Gripper, Quantec 2000, and Shaping Hedstrom files in the M4.

Effectiveness of eucalyptol and d-limonene as gutta-percha solvents

Eucalyptol and d-limonene were evaluated for their ability to serve as a substitute solvent for chloroform. The amount of time required to soften and remove the gutta-percha in 72 instrumented and filled simulated root canals in epoxy blocks was measured. After preparation to the apices of the block canals with a #60 file, four different filling techniques were used. These obturations were softened with each solvent and then removed, first using a #15 Hedstrom file inserted to full working length, and then removing the remaining filling mass with a #60 reamer. The two instrument placements were timed: one for the Hedstrom file insertion to the apex and the other for the reamer to remove the filling material. Neither the different solvents nor the filling techniques had a significant effect on the times required for the H-files to reach the apex. However, the times for the reamer to remove the filling materials were effected both by the filling techniques and the solvents used.

Shaping ability of the M4 handpiece and Safety Hedstrom files in simulated root canals.

The aim of this study was to assess the shaping ability of the M4 reciprocating handpiece and Safety Hedstrom files in simulated canals. A total of 40 simulated canals of various angles and positions of curvature were prepared with an M4 handpiece using Safety Hedstrom files oriented with the ground, flattened surface towards the inner aspect of the curve. A standard regimen was adopted throughout. Pre- and post-operative longitudinal images of the canals were taken with a video camera and stored and manipulated in a computer with image analysis software. The presence of canal aberrations and the amount and location of resin material removed as a result of preparation were determined from composite images of superimposed pre- and post-operative views. Preparation time varied significantly (P < 0.001) between the canal types; overall, 20 degrees canals were prepared more quickly than 40 degrees canals. Zips and elbows were observed in 16 out of the 40 canals with most (11) being created in 40 degrees specimens. Ledges were found in 19 canals and perforations in only 1. There were no significant differences between canal shapes for these aberrations. Excessive removal of material from the inner aspect of the canal at the curve to create a danger zone was found in 20 canals, but only in those with 40 degrees curves. Significant differences in total canal width between the canal types were seen at the zips (P < 0.05), elbows (P < 0.05) and danger zones (P < 0.001). Transportation at the danger zones varied significantly (P < 0.001) between canal types. Under the conditions of this study, the M4 handpiece and Safety Hedstrom files created hour-glass preparations in a substantial proportion of canals. In reality, the Safety Hedstrom file with its one flattened surface was ineffective at reducing removal of material along the inner aspect of canal curves in severely curved specimens and clearly has the potential to create strip perforations in teeth.

Endodontic measurements in digital radiographs acquired by a photostimulable, storage phosphor system.

Digora is a newly developed digital system for intraoral radiography utilizing photostimulable storage phosphor image plates. The aim was to test the quality of the system in respect to the visibility of endodontic files and root apices at different exposures. In teeth from five dry mandibular jaw sections, Hedstrom files no. 15 were placed with the file tip at varying distances from the apex. The specimens were covered with soft tissue equivalent material and placed behind a 2-cm thick polymethyl methacrylate cylinder filled with water. Distance from focus to image plate was 30 cm. Exposures were made at 60 kV and 7 mA at 7 timer settings from 16 ms to 1000 ms in 50% increments. All images were viewed from the monitor by each of 8 observers allowed to use available contrast enhancement facilities to obtain subjectively good image quality. Utilizing built-in measurement functions, distances from file tip and root apex, respectively, to a reference line were measured in 0.1 mm. For measurements between file tip and reference line, and root apex and reference line, there was no statistically significant difference between measurements made at the lowest exposure, compared to the second lowest exposure but there was a statistically significant difference compared to the 5 highest. Measurements at the second lowest exposure were not significantly different from those obtained at the 5 highest exposures. Interobserver variability expressed as standard deviation between observers showed the largest value for measurements obtained at the lowest exposure. The mean observed distances between the tip of the file and the root apex were calculated and showed no statistically significant differences between different exposures. We concluded that the Digora intraoral image plate system provided reliable endodontic measurements even at very low exposures.

Removal of overextended gutta-percha root canal fillings in endodontic failure cases

A procedure is proposed for the complete removal of an overextended root canal filling when associated with a root canal treatment failure. First, the gutta-percha is softened with xylene and removed to a distance of 2 to 3 mm short of the apex. Second, the remaining gutta-percha, which is preserved as solid as possible, is removed by a Hedstrom file. The file is extended 0.5 to 1.0 mm beyond the apex, firmly engages the gutta-percha and is slowly removed. In 17 of the 18 cases, this procedure successfully removed the overextended gutta-percha.

Effect of preflaring on tactile detection of the apical constriction

The efficacy of tactile detection of the apical constriction in flared and nonflared root canals was examined in 120 root canals of adult patients. In 68 nonflared (group 1) root canals, a #15 or #20 K-file was used to detect ("feel") the apical constriction. In 52 teeth (group 2), Hedstrom files, Gates Gliden drills #2 to #4, and ultrasonic files were used to enlarge the canal orifice and flare the coronal portion of the root canals before testing the apical constriction. After placing a #15 or #20 file in each root canal, a radiograph was taken, and the distance between the tip of the file and the radiographic apex was measured. The location of the file tip was classified into three categories: (a) within 1 mm short of the radiographic apex; (b) underextended, more than 1 mm short of the radiographic apex; and (c) overextended beyond the radiographic apex. In group 1 (nonflared), 32.3% of the root canals were classified in category a, as compared with 75.0% in group 2 (preflared). Over 26% of the root canals in group 1 and approximately 4% of the canals in group 2 were included in category b. Files inserted in preflared root canals had a significantly lower incidence of overextension than those placed in nonflared canals (21% versus 41%). The ability to determine the apical constriction by tactile sensation was significantly increased when the canals were preflared (p < 0.0001).

Root canal instruments are poorly standardized

In an earlier study we demonstrated that root canal instruments vary greatly in their effectiveness in removing substrates. To further analyze the reason for this variation of results, the dimensions of the instruments used were considered of interest as their matching effectiveness may be size dependent. Nine different brands of Hedstrom files, seven brands of K files, and four brands of special files were examined. The measurements were done in a computerized measuring microscope and the data were compared with earlier reported data on machining. Although the dimensions of the instruments varied greatly, no correlation could be found between the machining and dimensions. Only one brand of files was completely within allowable size range.

An assessment of the plastic Thermafil obturation technique

Adaptation and placement of alpha-phase gutta-percha delivered with a plastic core-carrier, Thermafil, was compared to the lateral condensation of gutta-percha in a specific tooth model. Fifty-one mandibular molar roots with separate canals, patent canal orifices and curvatures greater than 15 degrees were cleaned and shaped with K-files and 2.5% sodium hypochlorite to a size 30 at the apex, and flared with Hedstrom files to create a continuously tapering funnel preparation. Canals were randomly obturated with Sealapex root canal sealer and either alpha-phase gutta-percha on a plastic Thermafil carrier, or standard beta-phase gutta-percha with lateral condensation. Roots were radiographed from the proximal and evaluated by three examiners, based on established criteria for overall material adaptation, apical adaptation, and filling material extrusion. Thermafil provided a statistically significant better overall canal obturation (P < 0.001), while, in the apical third, both techniques were not significantly different (P > 0.05). When the apical orifice was patent there was a significant propensity for the extrusion of filling materials beyond the apex (P < 0.001) with the Thermafil technique.

Human saliva coronal microleakage in obturated root canals: An in vitro study

This study assessed salivary penetration through obturated root canals as related to time by using two methods of analysis--histological examination and dye penetrations. A total of 160 human maxillary anterior teeth were instrumented to size 60 Hedstrom file. Ten of the teeth were not obturated; 150 teeth were obturated by lateral condensation of gutta-percha and Roth's root canal sealer. Fifty of these teeth received intermediate restorative material temporaries to a thickness of approximately 3 mm. All teeth were immersed in 50 ml of whole human saliva and kept at 37 degrees C and 100% humidity. The saliva was changed daily. At 2, 7, 14, 28, and 90 days, 32 teeth were removed from the saliva. Of these, two were unobturated and were examined for bacterial penetration by culturing of the apical one-third. Ten teeth without temporaries were immersed in Pelikan ink for 2 days to demonstrate the extent of salivary penetration. These teeth were decalcified and cleared to allow direct measurement of dye penetration. Decalcified serial 7-microns-thick sections were prepared from the remaining 20 teeth, 10 with and 10 without intermediate restorative material temporaries. The sections were stained with hematoxylin and eosin stain and Brown and Hopps stain. Saliva penetration assessed in histological sections was significantly less than was visualized with dye analysis. Salivary penetration at 3 months was significantly greater than at the four earlier study periods. This amount of salivary penetration was considered to be clinically significant. The results strongly suggest retreatment of obturated root canals that have been exposed to the oral cavity for at least 3 months.

Halothane and eucalyptol as alternatives to chloroform for softening gutta-percha

Because chloroform was identified as a potential carcinogen by the Food and Drug Administration, interest has been revived to identify an alternative solvent to soften gutta-percha for removal from obturated root canals. This study compared the effectiveness of halothane, eucalyptol, and chloroform in softening gutta-percha in simulated root canals. One milliliter of a solvent was placed into a small glass funnel whose stem was obturated with a 30-mm column of gutta-percha. After 30 s, softening was evaluated for each solvent by recording the time required to reach a depth of 10 mm by hand filing with a #100 Hedstrom file. The depth of penetration of a #40 finger plugger under constant weight for 15 min was also determined for each solvent. By using a one-way analysis of variance and Scheffe's test, all comparisons were not significant except for the depth of penetration with constant weight between chloroform and halothane (p less than 0.05). The results indicate that halothane and eucalyptol are suitable alternatives to chloroform as gutta-percha softening solvents.

The influence of different root canal instruments on root canal preparation: an in vitro study

Nine endodontic instruments from different manufacturers (Reamers, K-files, Hedstrom files, K-Flex files, Flexofiles, S-files, Burns Unifiles, Flexicut files and Flex-R files) were used to prepare 180 simulated root canals in resin blocks. The instrument's ability to reproduce a theoretical pre-established ideal canal shape was assessed by comparing the original canal path with the resulting enlarged canal shape by a double exposure photographic method. The individual ability of each instrument to transport debris was also observed during instrumentation under a stereomicroscope. Regardless of the instrument type, none was able to reproduce ideal results; however, clinically acceptable results could be obtained with all of them. The coronal and apical debris transportation characteristics proved to be similar with all instruments.

Machining efficiency of Flex-R, K-Flex, Trio-Cut, and S files

Many root canal instruments with several different designs have been introduced during recent years. This article evaluates the machining properties of four such instruments: the Flex-R, K-Flex, Trio-Cut, and S file. There are large variations in the machining properties of these instruments. The results are comparable to findings when evaluating conventional root canal files which show that the Hedstrom file is much more efficient when considering removal of material than the K file. The Flex-R file, K-Flex file, and Trio-Cut file are similar in design. The two former brands perform in a similar fashion, while the Trio-Cut file is less efficient than any of the evaluated K files. The S file performs as a Hedstrom file which can be expected from its similarity in design to that instrument.

A comparison of endodontic file tip quality

Tip angulation and four visual characteristics denoting manufacturing quality of endodontic files were studied. One-hundred eighty K-type, Hedstrom, and Flex-type files from two manufacturers (Kerr and Mallefer) were evaluated. Photomicrographs (x 115) were made of each file. Two evaluators examined the photomicrographs. Tip angulation was studied to determine if files were compliant with ANSI/ADA Specification Nos. 28 and 58. The four visual characteristics compared in the study were symmetry versus asymmetry, smooth versus irregular, tip configuration, and shoulder configuration. Statistical analysis was made using the chi-square method. Mallefer files appear to be more in conformity with specifications for tip angle and more meticulously manufactured than Kerr files. Kerr Hedstrom files appear to conform less often to tip angle specifications than Kerr K-type or K-Flex files. K-type and Flex-type file tips appear to be better manufactured than Hedstrom file tips. Certification status of a file manufacturer did not correlate with a higher level of compliance with tip angulation specifications or with a better machined file tip.

Machining efficiency of endodontic K files and Hedstrom files

Methods for the objective evaluation of the machining property of endodontic files were described earlier. These methods were used in this investigation to assess the characteristics of machining of 7 different brands of K files and 10 brands of Hedstrom files. The results show that there are large variations in amounts of material removed by the files. These variations are large between brands of instruments as well as between files of the same brand. Thus, among the 510 files evaluated, the file with the highest machining quality was more than 40 times as effective as the least effective instrument. The highest values among K files were obtained with files manufactured by Maillefer followed by Antaeos, Healthco, JS Dental, Brasseler, and Miltex. Among the Hedstrom files, the most efficient brands were Antaeos and Zipperer followed by Healthco, Hygenic, JS Dental, Miltex, Maillefer, Union Broach, and the least efficient Brasseler. The files did not wear noticeably during these testing procedures. These results clearly indicate that the provider needs more information from the manufacturer in regard to machining and cutting in order to intelligently select instruments. It is suggested that procedures be agreed upon to evaluate machining and cutting of root canal files in order to provide the endodontist with better information about instruments.

Shaping of simulated root canals in resin blocks using files activated by a sonic handpiece.

A total of 180 simulated root canals in clear resin blocks with various lengths and degree of curvature were prepared by either Heliosonic, Rispisonic or Shaper files activated by a sonic handpiece. Each file type was used to prepare 60 canals employing an in/out, circumferential filing motion. The efficacy of the sonic handpiece and the three file designs were assessed by instrumentation time, deformation and fracture of instruments and loss of working distance. The shape of the prepared canals was assessed by direct observation and from composite photographic prints produced by super-imposing negatives of the canals obtained before and after preparation. Overall, canal shaping with the Rispisonic and Shaper files was rapid and efficient whilst that with the Heliosonic files was slower and ineffective. With each file type, prepared straight canals displayed a continuously tapering form that was narrowest at their end-point. The majority of curved canals prepared with Heliosonic files were hourglass in shape whilst the majority prepared with the Rispisonic and Shaper files were tapered. Zips and elbows were only created with Rispisonic and Shaper files in those canals with very short, acute curves. Under the conditions of this study the use of Rispisonic and Shaper files activated by a sonic handpiece proved a satisfactory method of shaping simulated root canals in resin blocks.

Cutting efficiency of endodontic hand instruments. Part 4. Comparison of hybrid and traditional instrument designs

In this study the cutting efficiency of three hybrid designs of endodontic instruments were compared with traditional K-type and H-type files for their ability to enlarge standardized artificial root canals. Sizes #15 through 30 instruments were tested in a clinical manner by serial preparation using a circumferential filing motion as the method of canal enlargement. The relative cutting ability of each group was evaluated in terms of the mean specimen weight loss following serial preparation. The cutting efficiency of each group was reported as the rate of canal enlargement, based on the mean specimen weight loss versus time. Significantly greater cutting efficiency occurred with the newly designed S file and traditional Hedstrom files over other types of hand instruments.

Evaluation of calcium phosphate as a root canal sealer-filler material

This study was conducted to evaluate calcium phosphate cement as a root canal sealer-filler material. Fifteen teeth of one adult beagle dog were instrumented to a #30 Hedstrom file and filled with calcium phosphate cement mixed into a creamy paste using glycerin and phosphoric acid in a ratio of 1:1 in group A and a ratio of 3:1 in group B. Four teeth were used as controls and were filled with gutta-percha using the lateral condensation technique. Histological evaluation of the periradicular tissues of both experimental and control teeth showed variable degrees of inflammatory response after 62 days. Also, calcium phosphate cement showed a uniform and tight adaptability to the dentinal surfaces of the pulp chamber and root canal walls similar to that of gutta-percha cones. This study was conducted to evaluate calcium phosphate cement as a root canal sealer-filler material. Fifteen teeth of one adult beagle dog were instrumented to a #30 Hedstrom file and filled with calcium phosphate cement mixed into a creamy paste using glycerin and phosphoric acid in a ratio of 1:1 in group A and a ratio of 3:1 in group B. Four teeth were used as controls and were filled with gutta-percha using the lateral condensation technique. Histological evaluation of the periradicular tissues of both experimental and control teeth showed variable degrees of inflammatory response after 62 days. Also, calcium phosphate cement showed a uniform and tight adaptability to the dentinal surfaces of the pulp chamber and root canal walls similar to that of gutta-percha cones.