Gates-Glidden Research Articles

The use of modified nickel–titanium rotary file for preparing staging platform to retrieve instrument fragments from narrow and curved canal

Abstract Staging platform (SP) uses a modified Gates Glidden (GG) to help retrieve separated instruments deep in the root canal. However, GG drills may cause damage or severe dentin loss. A 46-year-old male patient was referred to the endodontic postgraduate clinics complaining of pain on biting related to the mandibular right second molar (#47). The preoperative periapical radiograph of #47 showed a previously initiated root canal treatment with an approximately 8-mm separated instrument in the apical third of a curved mesiolingual canal. A nickel–titanium (NiTi) rotary file size 25/0.04 was flattened with a carbide bur. The modified file was then used to create a centered SP. After SP was achieved, an ultrasonic tip was used at lower power for the trephination of dentin. The fragment became loose, and retrieval was achieved. The use of a modified NiTi rotary file presented a safe and alternative option to establish SP for instrument retrieval instead of using GG drills.

Comparative Evaluation of the Efficacy of ProTaper & Mtwo Rotary Retreatment System and Conventional Hand H-files for Removal of Gutta-percha from Root Canal - A Stereomicroscopic Study.

Root canal retreatment aims to eliminate or substantially reduce the microbial load from the root canal and removal of previous root filling materials is the primary goal of nonsurgical retreatment. To comparatively evaluate the effectiveness of ProTaper retreatment files, Mtwo retreatment files, and Hedstrom files along with Gates Glidden (GG) Drill by using a stereomicroscope for the detection of remaining gutta-percha after root canal retreatment using a stereomicroscope. Forty-five test samples were divided into three experimental groups (15 samples each), such as Group A-ProTaper retreatment files; Group B-Mtwo retreatment files; Group C-Hedstrom files along with Gates Glidden Drill. After routine endodontic treatment in the test samples, gutta-percha was removed from the test samples as per the division of different retreatment file systems. Further, test samples were divided longitudinally and were evaluated under the stereomicroscope. Stereomicroscopic images were captured and analysed under Image Analyser Software-Image J. One-way ANOVA test was used for comparison of gutta-percha removal between the groups and Tukey's post hoc test was used for pairwise comparisons. The least remaining filling material was seen in specimens retreated with the ProTaper universal system. The highest remaining filling material was seen in specimens retreated with Hedstrom file with Gates Glidden Drill. All experimental test techniques left gutta-percha remnants within the root canal. ProTaper universal rotary retreatment system proved to be an efficient method of removing gutta-percha and left relatively less volume in comparison with other test systems.

Comparative Evaluation of Antimicrobial Efficacy of Various Antibiotic Pastes and Calcium Hydroxide Using Chitosan as a Carrier Against Enterococcus faecalis: An In Vitro Study.

The use of intracanal medicaments between appointments can serve as an important aid in the sterilization of the root canal system. Calcium hydroxide is commonly used, but it is not completely effective against Enterococcus faecalis. A triple antibiotic paste (TAP) is used but has the problem of tooth discoloration. Double antibiotic paste (DAP) or modified TAP (MTAP) has been suggested to solve this. Chitosan has been used as a vehicle in pharmacology, and it has inherent antibacterial properties too. This study compares the efficacy of DAP and MTAP using chitosan as a vehicle with calcium hydroxide. Sixty single-rooted teeth were taken and decoronated with a length of 13 mm. Biomechanical preparation (BMP) was done with #3 Gates-Glidden (GG) drills, 17% ethylenediaminetetraacetic acid (EDTA), and 5.25% sodium hypochlorite (NaOCl) used for irrigation. These were kept in microcentrifuge tubes with 1 ml brain heart infusion (BHI)broth. Contamination was done with E. faecalis strain for 21 days. DAP and MTAP pastes were prepared and added to the chitosan solution. Groups were divided into 10 each, each medicament with saline or chitosan as the vehicle. The microbial load was measured at the end of two and seven days. The level of significance was kept at p = 0.05. Statistical analysis was done with the Kruskal-Wallis test and analysis of variance (ANOVA). DAP and MTAP groups with chitosan showed a significant reduction in the microbial load when compared to calcium hydroxide with chitosan. DAP and MTAP with chitosan can be effective intracanal medicaments against E. faecalis in refractory endodontic cases.

Comparison of Root Dentinal Crack Formation after Coronal Pre-Flaring using Different Rotary Instruments: An In vitro Study.

The aim of this study was to see the incidence of cracks in root dentin after coronal flaring using various rotary instruments such as Gates Glidden (GG) drills, ProTaper Universal SX, OneFlare, and HyFlex EDM. Seventy freshly extracted premolar teeth with single canal were collected. All the teeth were randomly divided into five groups of fourteen each (n = 14), of which one group served as the control and the rest of the four groups were instrumented with GG drills, ProTaper Universal SX, OneFlare, and HyFlex EDM, respectively. The GG drills resulted in a higher rate of crack formation in root dentin (P < 0.05) than the ProTaper Universal SX, OneFlare, and HyFlex EDM instruments (P > 0.05). The use of GG drills resulted in more crack formation. However, the results for the ProTaper Universal SX, OneFlare, and HyFlex EDM flaring instruments were less in terms of crack formation.

Comparative Evaluation of Antimicrobial Efficacy of Sodium Hypochlorite, Triphala, Eucalyptus, and Carvacrol against Enterococcus faecalis: An In Vitro study.

This study aimed to evaluate the antimicrobial effect of sodium hypochlorite (NaOCl), Triphala, Eucalyptus, and carvacrol on Enterococcus faecalis as the most common microorganism isolated from infected root canals. Seventy-five mandibular premolar teeth were randomly distributed into five study groups: 5.25% NaOCl, 10% Triphala, 1.25% Eucalyptus, 0.6% carvacrol, and negative control (saline) group. Samples were taken using paper points from the canal spaces and using Gates-Glidden (GG) drills from dentinal tubules; after sample culturing, the colony forming unit (CFU) were counted, which was analyzed by the Wilcoxon signed-rank test. All irrigants have shown a reduction of microorganisms in the root canal space. After the use of NaOCl and Eucalyptus, the bacterial count was significantly reduced in the canal, as well as dentin sampling, as compared to Triphala and carvacrol. The antimicrobial efficiency of all irrigants against E. faecalis revealed a significant difference (p < 0.05). All irrigants exerted significant antimicrobial activity against E. faecalis. Around 1.25% of Eucalyptus was the most effective irrigant than 5.25% of NaOCl, Triphala, and carvacrol. Panchal VV, Dahake PT, Kale YJ, et al. Comparative Evaluation of Antimicrobial Efficacy of Sodium Hypochlorite, Triphala, Eucalyptus, and Carvacrol against Enterococcus faecalis: An In Vitro study. Int J Clin Pediatr Dent 2022;15(5):514-519.

The Effect of Gates-Glidden Drills on the Quality of Root Canal Treatment by Pre-Clinical Dental Students.

AIM:This study was conducted to investigate the effect of applying Gates-Glidden (GG) drill by pre-clinical dental students on root canal treatment quality.METHOD:A total of 56 first molars consisting of 168 canals were selected in this study. For this purpose, 56 students who had been formerly trained by two methods of root canal preparation were randomly divided into two groups (n = 28). Group 1: the step-down method by GG and Group 2: step-back technique without GG. The prepared teeth were filled with gutta-percha/ZOE sealer using lateral condensation. Periapical radiographs were taken before and the following treatment to survey occurrence of preparation errors and CBCT images to determine residual dentine at furcation region.RESULTS:The findings showed that among 10 error types in specimens prepared by students, the occurrence of underfilling, overfilling, inappropriate, ledge formation, and single cone was more common without GG. There were no significant differences in residual dentine amount at furcation region between preparation with and without using GG (P > 0.05).CONCLUSION:Using GG for root canal preparation by dental students resulted in low errors and not an increased dentine removal risk.

Micro-computed tomographic comparative evaluation of efficacy of different rotary instrument systems for removal of gutta-percha/bioceramic sealer from oval root canals (in vitro study)

Aim: This study used micro-computed tomography (CT) to compare the efficacy of three techniques for removing the root canal filling in single oval-shaped root canals after using laterally compacted gutta-percha/bioceramic sealer (BCS). Materials and Methods: Root canals in 30 single-rooted teeth will be instrumented with the ProTaper NEXT (Dentsply Maillefer, Ballaigues, Switzerland) and obturated using lateral condensation technique with gutta-percha and BCS. The teeth were divided randomly into three groups (n = 10). Removal of the root fillings was performed using one of the following techniques: group 1: ProTaper Universal Retreatment System with continuous rotational motion (RM); Group 2: Reciproc files with reciprocating adaptive motion; and Group 3: retreatment was done using Gates Glidden (GG) drills and H files. The teeth were scanned with CT scans. The percentage of remaining filling material was recorded. The data were analyzed statistically using the one-way ANOVA test and Tukey's post hoc test. Two-way ANOVA was used to study the effect of the interaction of file type and root segment, at a 95% confidence level (P

DETECTION OF CRACK FORMATION FOLLOWING CORONAL FLARING WITH THREE DIFFERENT INSTRUMENTS USING TWO EVALUATION METHODS (IN VITRO STUDY)

INTRODUCTION: Coronal flaring is now considered as an essential preparatory step in root canal treatment sequence. OBJECTIVES: To detect crack formation after coronal flaring of root canals with Gates Glidden (GG) drills, ProTaper Universal (PT) SX, and Endoflare (Ef) flaring instruments using cone beam computed tomography (CBCT) and scanning electron microscope (SEM). MATERIALS AND METHODS: Thirty mesiobuccal canals of mandibular first molars were selected. Teeth specimens were classified into three equal groups according to the instrument used for coronal flaring. Group1: Gates Glidden drills, group 2: ProTaper Universal SX and group 3: Endoflare instruments. Preoperative and postoperative (CBCT) imaging was performed and defect formation was detected. All roots were sectioned horizontally at 2,4and 6 mm from the cementoenamel junction. The sections were inspected under SEM, and any defect formations were recorded and compared with CBCT images according to scoring system. Data were collected and then statistically analyzed at an alpha error of 0.05. P≤0.05 were considered significant. RESULTS: The Ef file produced significantly less dentinal defects compared with the GG and PT SX at the three studied sections. Significant differences were found between the 3 groups at 2 and 4 mm with values (P=0.026) & (P=0.050) respectively, while no significant difference was found at 6mm with value of (P=0.217) when using the 2 evaluation methods. There was a significant difference (P=0.049) between the two used evaluation methods. CONCLUSIONS: Although all used coronal flaring instruments caused dentinal defects, Endoflare file showed the least defects. CBCT was not able to detect the smallest defects such as craze lines while SEM showed more capabilities and was considered as a confirmatory method. KEYWORDS: Coronal flaring, cracks, cone beam computed tomography, scanning electron microscope.

Failure analysis of eleven Gates Glidden drills that fractured intraorally during post space preparation. A retrieval analysis study.

The purpose of this study was to determine the failure mechanism of clinically failed Gates Glidden (GG) drills. Eleven retrieved GG drills (sizes #1 to #3) which fractured during root canal preparation were collected and the fracture location was recorded based on macroscopic observation. All fracture surfaces were investigated by a SEM. Then the fractured parts were embedded in acrylic resin and after metallographic preparation, the microstructure and elemental composition was evaluated by SEM and EDS. The Vickers hardness (HV) of all specimens was also determined. Macroscopic examination and SEM analysis showed that the drills failed near the hand piece end by torsional fatigue with fatigue cracks initiating at several locations around the circumference and propagating toward the center. Final fracture followed by a tensile overloading at the central region of cross section. Microstructural analysis, hardness measurements and EDS show that the drills are made of a martensitic stainless steel like AISI 440C. Based on the findings of this study, clinicians should expect fatigue fracture of GG drills that have small size during root canal preparation. Selection of a more fatigue resistant stainless steel alloy and enhancing the instrument design might reduce the incidence of quasi-cleavage fracture on GG drills.

Radiographic and scanning electron microscopic assessment of root canal filling remnants after endodontic re-instrumentation

Objective: Failures in endodontic treatment may occur by several reasons. Endodontic retreatment is an interesting alternative to manage this clinical problem. However, it is not possible to completely remove the root canal filling by any current retreatment technique. The aim of this study was to evaluate the presence of residual root canal filling materials after endodontic re-instrumentation. Material and Methods: Sixty extracted anterior human teeth were prepared by step-back technique with Flexofiles, K-files and Gates-Glidden (GG) burs. Between the use of each file or bur, root canals were irrigated with sodium hypochlorite (NaOCl). Smear layer was removed by irrigation with ethylenediaminetetraacetic acid and NaOCl. After drying with paper points the root canals were randomly divided into 5 groups (n = 12), according to filling material: Resilon cones/Real Seal sealer or gutta-percha cones and Endofill, Sealapex, AH Plus or MTA Fillapex sealers. After one week, root canal fillings were removed using Eucaliptol and K-files. Root canals were re-instrumented with K-files and GG burs sized larger than the first ones. The removal of root canal filling material was analyzed by radiography and scanning electron microscopy (SEM). Statistical analysis was performed using Binary Logistic Regression test (P &lt; 0.05). Results: Radiographic and SEM analysis showed that material from the MTA Fillapex group was better removed than that from Endofill, Sealapex, AH Plus and Real Seal groups. Conclusion: After re-instrumentation, MTA Fillapex group showed less remnants into the root canals than Endofill, Sealapex, AH Plus and Real Seal groups. Residual material was most often found in the apical third.Keywords Dental radiography; Endodontic retreatment; Root canal filling materials; Scanning electron microscopy.

Efficacy of LA Axxess burs, Gates Glidden drills and Protaper Sx in obtaining straight line access in mesiobuccal roots of mandibular first molars: A cone-beam computed tomography assessment.

Objective:This study aims at cone-beam computed tomography (CBCT) evaluation of the ability of Gates Glidden (GG) drills, Protaper Sx, and LA Axxess burs to produce a straight line access (SLA) in mesiobuccal canals of mandibular first molars.Methodology:Forty-five freshly extracted mandibular teeth with a canal curvature of 10-20° were taken for the study and divided into three groups according to the instruments used for cervical preflaring: Group I (LA Axxess burs), Group II (GG drills), and Group III (Protaper Sx). Pre- and post-instrumentation CBCT images were evaluated for comparing the ability of GG drills, Protaper Sx and LA Axxess burs to produce an SLA in mesiobuccal canals of mandibular first molars.Results:There was no significant change (P = 0.06) in the angle in the preSLA images of LA Axxess Group I (12.37 ± 1.01), GG Group II (13.39 ± 1.74), and Protaper Sx Group III (13.90 ± 1.74). The mean decrease in the angle from preSLA to postSLA was significant for all the three groups (P = 0.0001). However, the mean change was highest in Group I (4.25 ± 1.14), followed by Group II (3.28 ± 1.22) and Group III (2.89 ± 1.53).Conclusion:LA Axxess burs were the most effective in reducing the coronal curvature and produced a straighter access to apical third compared to GG Drills and Protaper Sx.

Evaluation of occlusal fracture resistance of three different core materials using the Nayyar core technique.

Aim:The aim and purpose of this study was to determine the occlusal fracture resistance of three core buildup materials using the Nayyar technique.Materials and Methods:Thirty human extracted maxillary premolars were used for the study. The test samples were decoronated till the cementoenamel junction (CEJ) and proper cleaning and shaping was done with protaper niti files till the F3. Corresponding f3 protaper(Dentysply)gutta pecha cones were selected and obturated. The gutta-percha was removed till the depth of 4 mm from the coronal orifice with Gates Glidden (GG) drills for all the samples; then the samples were randomly divided into three different groups. Group I was restored with universal composite Z350XT, group II was restored with light curable glass ionomer cement (GIC), and group III was restored with miracle mix. The coronal buildup was done using compound supported matrix. The fracture resistance strength of all the specimen groups was tested under a universal testing machine.Results:The data of the study were statistically analyzed by one-way analysis of variance (ANOVA) and Bonferroni's comparison test. Results of the study showed that group I that was restored with the universal composite Z350XT showed much higher fracture resistance strength compared to the other two groups. Statistically significant difference was noted between group I and group II and also between group I and group III.Conclusion:It can be concluded that the core buildup done with composite offered better occlusal fracture resistance strength compared to light curable GIC and miracle mix.

Incidence of Apical Crack Initiation during Canal Preparation using Hand Stainless Steel (K-File) and Hand NiTi (Protaper) Files.

AimTo evaluate the incidence of apical crack initiation during canal preparation with stainless steel K-files and hand protaper files (in vitro study).Materials and methodsSixty extracted mandibular premo-lar teeth are randomly selected and embedded in an acrylic tube filled with autopolymerizing resin. A baseline image of the apical surface of each specimen was recorded under a digital microscope (80×). The cervical and middle thirds of all samples were flared with #2 and #1 Gates-Glidden (GG) drills, and a second image was recorded. The teeth were randomly divided into four groups of 15 teeth each according to the file type (hand K-file and hand-protaper) and working length (WL) (instrumented at WL and 1 mm less than WL). Final image after dye penetration and photomicrograph of the apical root surface were digitally recorded.ResultsMaximum numbers of cracks were observed with hand protaper files compared with hand K-file at the WL and 1 mm short of WL. Chi-square testing revealed a highly significant effect of WL on crack formation at WL and 1 mm short of WL (p = 0.000).ConclusionMinimum numbers of cracks at WL and 1 mm short of WL were observed with hand K-file and maximum with hand protaper files.How to cite this articleSoni D, Raisingani D, Mathur R, Madan N, Visnoi S. Incidence of Apical Crack Initiation during Canal Preparation using Hand Stainless Steel (K-File) and Hand NiTi (Protaper) Files. Int J Clin Pediatr Dent 2016;9(4):303-307.

The minimum residual root thickness after using ProTaper, RaCe and Gates-Glidden drills: A cone beam computerized tomography study.

Objective:The aim of this study was to evaluate the minimum residual root thickness (MRRT) of the danger zone after preflaring of the mesio-buccal (MB) canal of mandibular first molars using ProTaper, RaCe and Gates-Glidden (GG) drills as coronal shapers by cone beam computerized tomography (CBCT).Materials and Methods:In this experimental study, the initial CBCT scans of 75 MB canals of mandibular first molars were provided within 1, 2, 3 and 4 mm of the furcation level. The samples were divided into three groups. The samples of ProTaper and RaCe groups were prepared up to F2 and #25.04 as the master apical file (MAF), respectively. The coronal preparation of the samples in the GG group was done using GG drills #2, #3 and #4 and canals were prepared till MAF # 25. After obtaining the postinstrumentation images, the MRRT and the amount of removed dentin were analyzed by t-test and ANOVA statistical analyses.Results:The GG drills removed significantly more dentin than RaCe at all the sections (P < 0.05) and more than ProTaper at 3 mm from the furcation. Statistically there was no significant difference between ProTaper and RaCe groups (P > 0.05). There was no significant difference in MRRT between the groups (P > 0.05). The mean MRRT was not < 0.75 mm at all sections.Conclusion:Based on the results of this study, when an appropriate root thickness is initially present, all of the instruments that were investigated may safely be used as coronal shapers in MB canals of mandibular first molars.

Technical quality of root canal therapies performed by novice dental students in preclinical practice.

Background:For improving the quality of endodontic performance of practitioners in clinical practice, their basic, preclinical performance and knowledge must be taken into consideration. This study aimed to radiographically evaluate the technical quality of preclinical molar root canal treatments (RCTs) performed by undergraduate dental students at a dental school in Iran. Further, the effect of using Gates-Glidden (GG) drills on the final quality of RCTs was evaluated.Materials and Methods:In this retrospective cross-sectional study, 315 roots of 105 endodontically treated teeth in preclinical practice were evaluated radiographically. The analyzed quality parameters included length, taper and density of fillings, which were scored as S2 (adequate standard), the S1 (slight deviation), or S0 (considerable deviation). For all the parameters, acceptable, moderate and poor fillings received total scores of 6, 3-5 and 0-2, respectively. There were two groups of students: One group had used only K-files, and the other had used K-files along with GG drills. The quality of RCTs between these groups was evaluated using the aforementioned scoring protocol. The results were analyzed using Chi-square, Mann–Whitney and Fisher's exact tests (α = 0.05).Results:Under-fillings (P = 0.001) and under-shapings (P = 0.007) occurred mostly in mandibular root fillings. A lower density was found in maxillary fillings (P < 0.001). No relationship was observed between the technique used (irrespective of GG drills usage) and length (P = 0.499) and taper of fillings (P = 0.238). The roots instrumented with GG drills had a higher filling density (P = 0.004). The quality mean score of RCTs was improved when GG drills were used (P = 0.008).Conclusion:The technical quality of preclinical molar RCTs performed by undergraduate dental students was considered acceptable in 35.6% of the cases. When GG drills were used along with K-files, the technical quality of RCTs was enhanced.

The Efficacy of FlexMaster's IntroFile, PreRaCe and Gates Glidden Drills in Straight-Line Access: A CBCT Assessment.

An overlooked but important part of successful root canal treatment is a straight-line access (SLA). The purpose of this in vitro study was to compare the efficacy of IntroFile and PreRaCe rotary instruments with Gates Glidden (GG) drills in gaining SLA by cone-beam computed tomography (CBCT). A total of forty five extracted mandibular first molars were selected and mounted in dental like arches. Subsequently, they were randomly classified into three groups (n=15). After preparation of a standard access cavity, orifices of the mesiobuccal canal was reached and a #10 file was inserted to explore the canals until the file tip was visible at the apex. Then, preoperative CBCT images were taken. SLA was gained in three groups; group 1, FlexMaster's IntroFile (FM); group 2, PreRaCe (RC) and group 3, GG. Again, the first binding file at the working length (WL) was placed in the canal and postoperative CBCT images in similar positions were taken. The pre/post operative morphology of the canal was evaluated for changes. Data was analyzed using the one-way ANOVA and post-hoc Bonferroni analysis. The average amount of reduction in coronal canal curvature in FM, RC and GG groups was 2.43±1.79, 3.17±2.05 and 8.7±3.45, respectively. This descending trend was statistically significant. The difference between pre/post SLA changes in FM and RC groups was significant compared to GG group, while there were no significant differences between RC and FM. GG drills produced extraordinary results in reducing coronal curvature of the canal and achieving SLA. They are also more effective than nickel-titanium (NiTi) rotary instruments in canals with coronal curvature.

Computed tomography evaluation of residual root thickness after pre-flaring using gates Glidden drills: The sequence effect.

Aim:The aim of the present study is to evaluate the residual root thickness in mesiolingual (ML) canals of mandibular molars after pre-flaring using different sequences of Gates-Glidden (GG) drills.Materials and Methods:Computed tomography (CT) scans of the ML canals of 60 mandibular first molars were provided from areas within 1, 2, 3 and 4 mm of the furcation area and minimum initial root thickness (MIRT) of concave areas was measured at each level. The samples were divided into two groups (G1 and G2) which were prepared by the step-back and crown-down techniques, respectively. In both groups, anti-curvature filing was used. On secondary CT images of the samples in the same position, the minimum residual root thickness (MRRT) and the amount of removed dentin were analyzed by t-test and ANOVA.Results:There was no significant difference for MIRT between the two groups. The MRRT was greater in the G2 group in all the sections, with no significant difference between them. The average of MRRT was not <0.5 mm in any of the groups or sections.Conclusion:Based on the results of this study when the appropriate root thickness is present initially, GG drills used in any sequence may be suitable, safe and cost effective for pre-flaring of mesial canals of mandibular first molars with preserving the root thickness of furcation areas.

Comparative analysis of three rotary instruments used for coronal pre-enlargement in radicular dentin thickness and root canal area of mandibular molars

PURPOSE: The purpose of this study was to evaluate the increase of the cervical area and dentin thickness in mesial and distal walls of the mesial canals from mandibular molars after the use of LA Axxess (LA), CP Drill (CP) and Gates-Glidden (GG) rotary instruments. MATERIAL AND METHODS: Sixty root canals from thirty mandibular first molar were sectioned 3 mm below the cement-enamel junction, divided in 3 groups (n = 20 root canals, each) according to rotary instrument used, and the cervical images were captured before and after pre-enlargement instrumentation. The increase of the instrumented cervical area (mm2) and the dentin removal thickness (mm), at mesial and distal walls were calculated using Image tools software, by comparison of images. Data were analyzed by ANOVA and Tukey tests (p=0.05). RESULTS: All rotary instruments promoted thickness reduction in dentin walls. In mesial wall, all rotary instruments promoted similar thickness reduction of dentinal wall and did not differ from each other (p&gt;0.05). In distal wall, LA Axxess instrument promoted higher dentin thickness reduction than other groups (p&lt;0.05). The three rotary instruments promoted different increase at the instrumented cervical area (p&lt;0.05), LA promoted the highest increase area and GG and CP presented similar results. CONCLUSION: LA 20/0.06 promoted the highest thickness reduction in distal wall and increase of cervical area of root canal. On the other hand, CP was the safest instrument, with lower dentin removal of distal wall and similar increased area to GG.

Temperature rise on the external root surface during removal of endodontic fractured instruments

To investigate the temperature rise (TR) on the external root surface while preparing a staging platform, for removing intra-canal fractured instruments, using Gates Glidden (GG) drills. Thirty extracted mandibular incisors were decoronated and 3-3.5 mm of F3 ProTaper files were fractured 3 mm from the most coronal end of the root. Roots were divided into three groups. GG drills were used in a size-2 to size-5 sequence to prepare the staging platform coronal to the fractured segment. They were rotated at three speeds according to the study groups: group A for 2,000 revolutions per minute (rpm); group B for 4,000 rpm; and group C for 8,000 rpm. Temperature changes were recorded at the proximal and buccal or lingual external root surfaces while preparing the staging platform. Data were analyzed using the paired sample T, one- and two-ways ANOVA tests at p ≤ 0.05. Overall, TR at the proximal root surface (5.44 °C) was significantly higher than that at the buccal or lingual surface (3.25 °C) (p < 0.001). Generally, TR increased significantly as the size of GG drills or the revolution speed increased (p < 0.05). GG5 drills rotated at 8,000 rpm produced the highest TR (10.85 °C). There was no interaction effect of the GG drill size and the revolution speed on TR (p = 0.272). The highest TR on the external root surface, associated with preparation of a staging platform and produced by using GG drills size-5 rotating at up to 8,000 rpm, was lower than the damaging threshold. A staging platform can be performed by modified GG drills (no 2 to 5) rotating at 8,000 rpm without generating a hazardous TR.

Influence of cervical preflaring on determination of apical file size in the palatal roots of maxillary molars

PURPOSE: The aim of this study was to investigate the influence of cervical preflaring in determining the initial apical file (IAF) in the palatal roots of maxillary molars, and to determine the morphologic shape of the canal 1 mm short of the apex. METHODS: After preparing standard access cavities the group 1 received the IAF without cervical preflaring (WCP). In groups 2 to 5, preflaring was performed with Gates-Glidden (GG), Anatomic Endodontics Technology (AET), GT Rotary Files (GT) and LA Axxes (LA), respectively. Each canal was sized using manual K-files, starting with size 08 files, and making passive movements until the WL was reached. File sizes were increased until a binding sensation was felt at the WL. The IAF area and the area of the root canal were measured to verify the percentage occupied by the IAF inside the canal in each sample by SEM. The morphologic shape of the root canal was classified as circular, oval or flattened. Statistical analysis was performed by ANOVA/Tukey test (P GT=AET>GG>WCP. The morphologic shape was predominantly oval. CONCLUSION: The type of cervical preflaring used interferes in the determination of IAF.