Stainless Steel Hand Files Research Articles

Fracture Strength of Tooth Roots following Canal Preparation by Hand and Rotary Instrumentation

The study aimed to determine fracture loads in tooth roots after canal preparation using different techniques. Mesiobuccal roots of 39 extracted mandibular molars were used. Three groups each of 13 roots were prepared by stainless steel hand files (K-files), and two rotary nickel-titanium techniques (Lightspeed and Greater Taper files). After obturation, a vertical load was applied by means of a spreader inserted into the canal until fracture occurred. The mean fracture load was 10.2 ± 4.4 kg for K-files, 15.7 ± 9.1 kg for Lightspeed and 13.2 ± 6.1 kg for Greater Taper files, but differences were not statistically significant (p > 0.05). Most fracture lines were incomplete fractures on the buccal surface, followed by proximal and compound fractures. Greater apical enlargement (Lightspeed) or increased canal taper (Greater Taper files) did not increase fracture susceptibility of tooth roots.

The Influence of a Manual Glide Path on the Separation Rate of NiTi Rotary Instruments

The dual purpose of this study was, to evaluate the fracture rate of Ni-Ti rotary instruments when following a manual glide path and using stainless steel hand files before carrying out instrumentation by means of rotary files and, to compare the results in this study with those obtained in two previous analyses, in which the glide path technique was not used. A total of 208 canals obtained from a pool of freshly extracted human mandibular and maxillary molars was divided into three groups corresponding to; K3, ProFile and ProTaper. The coronal 2/3 of each tooth were used. In all three groups the apical portion of the samples was prepared with size 10-20 stainless steel K-type hand files. The apical stops were prepared using K3, ProFile and ProTaper rotary instruments. Logistic regression model analysis indicated that breakage was significantly associated with the angle of curvature of the canal (OR = 1.078; 95% CI = 1.032–1.12; p = 0.001), and with the number of clinical uses (files used more than eight times broke more frequently that those used 1 or 2 times; OR: 22.686; 95% CI: 2.6–191.3; p = 0.004). The breakage rate obtained in the present study is significantly lower than in our previous studies, in which the angle of curvature was also greater than 30° and rotational speed a constant 350 rpm, but in which the canals were not first prepared with hand files (25/205 = 12% versus 16/61 = 26%, p = 0.007). Based on the results of this study, we recommend the use of stainless steel hand files to prepare the apical 1/3 of curved canals before introducing rotary files.

Microbial status of apical root canal system of human mandibular first molars with primary apical periodontitis after “one-visit” endodontic treatment

To assess the in vivo intracanal microbial status of apical root canal system of mesial roots of human mandibular first molars with primary apical periodontitis immediately after one-visit endodontic treatment. The residual intracanal infection was confirmed by correlative light and transmission electron microscopy. Sixteen diseased mesial roots of mandibular first molars were treated endodontically, each in one visit. Mesio-buccal canals were instrumented using stainless steel hand files and mesio-lingual canals with a nickel-titanium rotary system. The canals were irrigated with 5.25% sodium hypochlorite (NaOCl) during the instrumentation procedures, rinsed with 10 mL of 17% ethylenediamine tetraacetic acid (EDTA), and obturated with gutta-percha and zinc oxide eugenol cement. Thereafter, the apical portion of the root of each tooth was removed by flap-surgery. The specimens were fixed, decalcified, subdivided in horizontal plane, embedded in plastic, processed, and evaluated by correlative light and transmission electron microscopy. Fourteen of the 16 endodontically treated teeth revealed residual intracanal infection after instrumentation, antimicrobial irrigation, and obturation. The microbes were located in inaccessible recesses and diverticula of instrumented main canals, the intercanal isthmus, and accessory canals, mostly as biofilms. The results show (1) the anatomical complexity of the root canal system of mandibular first molar roots and (2) the organization of the flora as biofilms in inaccessible areas of the canal system that cannot be removed by contemporary instruments and irrigation alone in one-visit treatment. These findings demonstrate the importance of stringent application of all nonantibiotic chemo-mechanical measures to treat teeth with infected and necrotic root canals so as to disrupt the biofilms and reduce the intraradicular microbial load to the lowest possible level so as to expect a highly favorable long-term prognosis of the root canal treatment.

The Accuracy of the Root ZX Electronic Apex Locator Using Stainless-Steel and Nickel-Titanium Files

Numerous apex locator studies have been performed. Generally, they use only stainless-steel hand files for testing purposes. Today many clinicians use both stainless-steel and nickel-titanium files during the treatment of a case. Given the widespread use of nickel-titanium files, a comparison of the accuracy in determining length with an apex locator using stainless-steel and nickel-titanium files seems clinically relevant. Campbell et al. (1) published a study where only nickel-titanium files were used. A literature search failed to reveal any studies that directly compared stainlesssteel and nickel-titanium files when used with an apex locator to determine length measurements in the same tooth. The purpose of this study was to determine if there is a measurable difference in accuracy of length determination when stainless-steel and nickeltitanium files were used for this purpose in the same tooth.

Analysis of Mechanical Preparations in Extracted Teeth Using ProTaper Rotary Instruments: Value of the Safety Quotient

The purpose of this study was to apply the Endographe to analyze the vertical forces and torque developed during mechanical preparations in extracted teeth. The data collected in this study may be used to calculate the safety quotient (SQ) as proposed by J.T. McSpadden. The SQ formula is defined as the torque required to break a file at D3 divided by the mean working torque required to cut dentin. The Endographe is a unique force-analyzer device equipped to measure, record, and generate graphs of the vertical forces and torque exerted during root canal preparation. All preparations were performed by endodontists in roots with narrow, more restrictive canals, larger, more open canals, or in roots sectioned in two halves. All canals, including the sectioned canals, were prepared with ProTaper files in accordance with the manufacturer's guidelines for use. For narrow canals, the mean values of the generated vertical forces (g) and torque (g.cm) varied from 80 (+/- 20) g (SX) to 232 (+/- 60) g (F2) and from 80 (+/- 24) g x cm (F1) to 150 (+/- 45) g x cm (S2), respectively. For large canals, the mean values of the generated vertical forces (g) and torque (g x cm) varied from 80 (+/- 20) g (SX) to 340 (+/- 20) g (F1) and from 31 (+/- 9) g x cm (S2) to 96 (+/- 35) g x cm (SX), respectively. The SQ varied from 0.93 to 7.95 for narrow canals and from 1.58 to 14.50 for large canals. The SQ is intended to provide values that can be analyzed to predict whether a rotary file will have a tendency to break or will work safely during clinical use. However, if the formula is going to provide useful information, it must index the "rotation to failure torque" with the "mean working torque" at a specific location along the cutting blades of a file. Additionally, this mathematical formula does not account for factors such as the concentration of forces, the way the instruments are used, or the wear of the instruments. A precise protocol for canal preparation should emphasize using small flexible stainless steel hand files to create or verify that within any portion of a root canal there is sufficient space for rotary instruments to follow. When there is a confirmed smooth, reproducible glide path, then a "secured" space exists to safely guide the more flexible terminal extent of a rotary NiTi file. Endogrammes provide an innovative approach to the analysis of mechanical preparations and suggest that the ProTaper shaping files are best used with lateral forces to decrease the coronal screwing effect. The ProTaper finishing files should be used with slow penetration and be introduced only into canals that have a confirmed smooth and reproducible glide path. When any part of the overall length of a canal has been secured, then the number of instruments, the time spent utilizing each instrument, and the overall time progressing through a sequence of instruments to shape this region of the canal is reduced.

Identifying Multiplanar Root Canal Curvatures Using Stainless-Steel Instruments

Information obtained from careful observation of stainless-steel hand file deformation can be a critical step in efficient root canal space debridement. Secondary and tertiary canal curvatures that occur most often in the proximal view have been reported in the literature. Except in teeth that are clinically rotated, there is currently no method for observing the proximal view of root canal systems. This article presents a simple clinical procedure for detecting the three-dimensional anatomy of root canal spaces. We refer to the procedure as file molding.

The Quality of Apical Canal Preparation Using Hand and Rotary Instruments with Specific Criteria for Enlargement Based on Initial Apical File Size

The aim of this study was to compare the quality of apical enlargement of mesiobuccal canals of mandibular molars using conventional stainless steel hand files (K files) and nickel-titanium (Ni-Ti) rotary instruments (LightSpeed). Thirty freshly extracted mandibular molars were randomly assigned to three equal groups (n = 10 each group). The mesiobuccal canals were instrumented with K file using step-back technique without coronal flaring (control; group 1), K file using step-back technique after coronal flaring (group 2), and LightSpeed instrumentation (group 3). Specific criteria for apical enlargement based on initial apical size were used. For step-back techniques, the master apical file sizes were based on the Grossman criterion of three sizes larger than the first file that bound at working length, without coronal flaring (group 1) and with flaring (group 2). For the LightSpeed (LS) group, the master apical rotary sizes were based on the manufacturer's recommendation. Canal cleanliness, canal transportation, and final canal shapes were determined histologically at 1-mm and 3-mm levels short of the working length. Canals were prepared to significantly larger sizes using LS instrumentation than with either hand instrumentation techniques (15-17 ISO units, p < 0.001). LS instrumentation allowed greater apical enlargement with significantly cleaner canals, less apical transportation, and better canal shape than both hand instrumentation groups at both levels (p < 0.05). None of the three techniques was totally effective in cleaning the apical canal space. It was concluded that greater apical enlargement using LS rotary instruments is beneficial as an attempt to further debride the apical third region in mesiobuccal canals of mandibular molars. Instrument designs, alloy properties, and canal curvature are important factors that determine the feasibility of greater apical enlargement in narrow canals.

Effect of Early Coronal Flaring on Working Length Change in Curved Canals Using Rotary Nickel-Titanium Versus Stainless Steel Instruments

This in vitro investigation examined pre- and postinstrumentation working length (WL) measurements in curved root canals. The conditions compared were combinations of (a) stainless steel hand files + Gates Glidden drills (SS) versus nickel-titanium rotary files (Ni-Ti); and (b) early coronal flaring (flaring completed before WL determination) versus late coronal flaring (flaring completed after WL determination). Coronal flaring was accomplished for the SS group using Gates Glidden drills and for the Ni-Ti group using rotary Ni-Ti files (n = 15/group). WL was determined before coronal flaring, immediately after coronal flaring, and again after canal preparation. Results indicated that WL decreased for all canals as a result of canal preparation. The mean decrease in WL was significantly greater for the SS group (-0.48 mm +/- 0.32) than for the Ni-Ti group (-0.22 mm +/- 0.26). Less change in WL occurred in both groups when initial WL was determined after coronal flaring (SS: -0.12 mm +/- 0.13, Ni-Ti: -0.14 mm +/- 0.25).

Gutta-percha Retreatment: Effectiveness of Nickel-Titanium Rotary Instruments Versus Stainless Steel Hand Files

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

The Deterioration of Rotary Nickel-Titanium Files under Controlled Conditions

It has been shown that rotary nickel-titanium files cannot be used indefinitely. Researchers and clinicians have not been able to agree on how many times a file can be used before being discarded, except if a file has fractured or become visibly distorted. This study used ISO size 20 files of 0.04 taper in the curved canals of extracted mandibular molars. The canals had been previously instrumented to an ISO size 15 with stainless steel hand files. The irrigant used during rotary and hand instrumentation was Glyde. The rotary files were closely examined with scanning electron microscopy before use to detect any defects. They were then reexamined after each of five uses to document deterioration. An electric handpiece was configured to rotate at 150 rpm and secured to the testing device, which also held the extracted tooth. The testing device controlled the load at 8 N, the depth of penetration for each canal and the rate of penetration (12 mm/min). Used instruments demonstrated surface fatigue wear and cracking. Torsional moment at failure was determined on a torsiometer for used and new instruments. Data (n = 10) were analyzed by analysis of variance. The torsional moment for used and new instruments was not affected by use (p = 0.25).

A comparison of canal centering ability of four instrumentation techniques

The purpose of this study was to compare three engine driven (nickel-titanium) NiTi instrument systems with hand files for their effect on canal transportation. Mesial roots of mature lower first molars with separate canals were paired on the basis of curvature and morphology. Canal lengths were standardized to 11 mm from orifice to apical foramen. Profile, Lightspeed, McXIM, and Flex-R hand filing techniques respectively were randomly assigned to one of the four canals of each tooth pair. The roots were mounted and sectioned at 1 mm, 3 mm, and 5 mm from working length using a modified Bramante technique. All sections were video imaged preoperatively after instrumentation to size #30 and after final instrumentation to size #40. The images were computer analyzed for changes in canal area and centering at each stage of instrumentation. Preparation time was also recorded. Data were analyzed using ANOVA. The NiTi systems remained better centered in the canal than stainless steel hand files. There were no significant differences among the NiTi systems at any level. The difference between hand filing and the NiTi techniques was more pronounced at size #40 than at size #30. The NiTi systems were all significantly faster than hand filing. No significant differences in preparation were found between the NiTi systems when canals were instrumented to the size nearest #40.

RS 21 Comparison of Ni-Ti and stainless steel hand files using computed tomography

RS 21 Comparison of Ni-Ti and stainless steel hand files using computed tomography