Evaluation of design, mechanical properties, and torque/force generation of heat-treated NiTi glide path instruments

Glide Path in Endodontics: A Literature Review of Current Knowledge

The introduction of nickel-titanium rotary instruments revolutionized shaping procedures as they were able to produce a well-tapered preparation while reducing operator fatigue. The major drawback of rotary instruments was the high risk of fracture due to bending and torsional stress. Thus, the creation of a glide path has been advocated and recommended by most rotary instrument manufacturers. The aim of the present review is to summarize existing knowledge on glide path preparation and identify areas where further research is needed. The primary goal is to provide a comprehensive overview of the techniques and instruments used in glide path preparation, highlighting their advantages and limitations. The secondary goal is to explore the effect of glide path creation on the overall success of endodontic treatment, particularly in terms of reducing procedural errors and improving treatment outcomes. An online search on PubMed, ScienceDirect, UCLA, and Scopus databases was conducted, and 116 articles were identified. Eligible articles were divided into nine categories based on what they researched and compared. The categories included centering ability and/or root canal transportation, cyclic fatigue resistance, glide path and shaping time, tortional stress resistance, apical extrusion of debris and/or bacteria, defects in dentine walls, file separation, postoperative pain assessment, and scouting ability and performance. Establishing a glide path reduces root canal transportation, especially with rotary methods. Reciprocating and heat-treated files offer higher fatigue resistance and shorter preparation time. Instruments with shorter pitch lengths have greater torsional strength. Preparation and coronal preflaring reduce apical debris and bacteria. Glide paths do not affect dentine microcracks, file separation, or defects but reduce immediate postoperative pain and improve cutting ability. Randomized trials are needed to assess their impact on treatment outcomes.

Screw-in force, torque generation, and performance of glide-path files with three rotation kinetics

We aimed to evaluate the screw-in force, torque generation, and performance of three nickel-titanium (NiTi) glide-path files with different rotational kinetics. ProTaper Ultimate Slider (PULS) and HyFlex EDM Glide-path (HEDG) files were used for canal shaping with constant rotation (CON) or the alternative rotation technique (ART). In the ART mode, the NiTi file was periodically rotated at a speed of 1.5 times faster than that in the CON mode. WaveOne Gold Glider was used with reciprocating motion (WOGG_RCP). Sixty J-shaped resin blocks were assigned to five groups: PULS_CON, PULS_ART, HEDG_CON, HEDG_ART, and WOGG_RCP (n = 12). Glide-path preparation was performed using an automated pecking device. During glide-path preparation, the screw-in force and clockwise and counterclockwise torques were recorded and the number of pecking motions required to reach the working length was determined. The centering ratio was calculated after glide-path preparation using stereomicroscopic images. Data were analyzed using one-way analysis of variance with the Games-Howell post hoc test and the Kruskal-Wallis test with Bonferroni correction. PULS_ART generated a lower maximum screw-in force than PULS_CON. The average number of pecking motions required to reach the working length by HEDG_ART was lower than that by HEDG_CON. The mean centering ratios of PULS_CON and HEDG_CON were - 0.04 and - 0.06, respectively, while those of PULS_ART, HEDG_ART, and WOGG_RCP were 0.09, 0.01, and 0.08, respectively. The ART mode reduced the screw-in force of PULS and enabled faster glide-path preparation with the HEDG file.

Dynamic torque and screw-in force of four different glide path instruments assessed in simulated single- and double-curved canals: An in vitro study

Background/purpose

The glide path instruments are the introductory instruments into the canals; thus, they should be durable enough to withstand torsional stress/screw-in force. This study aimed to investigate the torque and screw-in force of TruNatomy Glider (TN), ProGLIDER (PG), Hyflex EDM (EDM) and Dent Craft RE (RE) glide path instruments in single- and double-curved canals.

Materials and methods

Each instrument brand was divided into two groups (n = 7 each) according to the canal configuration. Torque and screw-in force were recorded during automated instrumentation of simulated resin canals with XSmart IQ cordless motor after the canal patency was checked with a #10 K-file. The values were statistically analyzed using the Kolmogorov-Smirnov test followed by the Kruskal Wallis test and the Mann-Whitney U test with Bonferroni correction (α = 0.05).

Results

TN produced significantly higher torque than RE in single-curved canals and PG in double-curved canals (P < 0.05). EDM yielded significantly higher screw-in force than TN and RE in single-curved canals (P < 0.05), but there was no significant difference in double-curved canals (P > 0.05). A significant effect of different canal configurations was only detected for screw-in force in EDM (P < 0.05).

Conclusion

TN in single-curved canals and RE in double-curved canals yielded higher torque values, while EDM exhibited greater screw-in force in both canal configurations. No effect of different canal configurations was detected for torque, but a significant impact was detected for screw-in force in EDM.

Scanning Electron Microscopic Analysis of Deformation of TruNatomy File Systems: An Ex-vivo Study

Aim The aim of the study was to assess the instrument deformation following the usage of the TruNatomy (Dentsply Sirona, USA) file system in extracted premolars using Scanning Electron Microscopy (SEM). Materials and Methods For the present study, 84 extracted mandibular bicuspids were selected. The teeth were divided into two groups: Group 1, TruNatomy (n=42), and Group 2, Hero Shaper (Micro Mega, France) (n=42). The samples were shaped with 0.03 taper to size 36 with TruNatomy instruments and 0.04 taper to size 30 with Hero Shaper instruments. 5 ml of 5.25% Sodium Hypochlorite (NaOCl) and 2 ml of 17% ethylenediaminetetraacetic acid (EDTA) were used for the final irrigation of root canals. The master apical file was used to instrument seven teeth samples for assessing the safety of the instruments after multiple uses and autoclaving. So, a total of six files per group was used for the analysis of any distortions, cracks or micro-fractures after instrumentation of 42 teeth, at the tip (D0) and 5 mm from the tip (D5) of the rotary file under SEM at 500x magnification. Statistical analysis To determine the significance between the groups, the Mann-Whitney U-test was applied. Results The mean surface wear of the instruments, at the tip (D0) in Group 1 was 1.2857 and in Group 2 was 1.4762. The mean spiral distortion of the instruments, at the tip (D0) in Group 1 was 1.1905 and in Group 2 was 1.4286. A statistically significant difference (P<0.05) was observed between the groups for surface wear and spiral distortion at the tip of the file (D0). There was no significant difference between groups for surface wear and spiral distortion values of the instruments at 5 mm from the tip (D5) (P>0.05). Conclusion The instrument distortion of the rotary file systems analysed was minimal following the biomechanical preparation of seven mandibular bicuspids without root curvature, using a single file. Therefore, both rotary file systems can be considered safe.