Apical debris extrusion of full-sequenced rotary systems in narrow ribbon-shaped canals

The effect of different kinematics on apical debris extrusion with a single-file system

To compare the amount of extruded debris caused by different motions using a single-file system. Fifty mandibular first molar teeth were randomized into 5 groups (n = 10) according to the motion tested: Optimize Torque Reverse (OTR), TF Adaptive Motion (TFA), continuous rotation (CR), reciprocation motion (+ 150°, -30°) (REC), and Jeni motion (Jeni). One Curve single file 25/06 (Micro-Mega, Besançon, France) was used in all experimental groups. The root canals were irrigated with 2.5% NaOCl, and the extruded debris were collected at pre-weighted glass vials. The glass vials were kept inside an incubator for one week at 70 °C to dry out the irrigating solution. The extruded debris was quantified by subtracting the pre-instrumentation from the post-instrumentation weight of the glass vials. The time required for each instrumentation procedure was digitally recorded. All data were analyzed statistically with one way ANOVA and post hoc Tukey test (P < 0.05). All the motions extruded apically debris with Jeni mode caused significantly less debris extrusion than TFA, REC, and CR (P < 0.05) while no significant difference emerged with OTR. Preparation time was not significantly different in all groups. Within the limits of the present study, all the kinematics produced apically debris extrusion, with Jeni reporting a similar amount of debris compared with OTR and significantly less than TFA, REC, and CR. Preparation time was similar among the tested kinematics.

Effectiveness of conservative instrumentation in root canal disinfection

OBJECTIVES

The impact of conservative instrumentation on the disinfection of root canals with different curvatures has not yet been determined. This ex vivo study aimed to evaluate and compare the effect of conservative instrumentation with TruNatomy (TN) and Rotate and a conventional rotary system, ProTaper Gold (PTG), on root canal disinfection during chemomechanical preparation of straight and curved canals.

MATERIALS AND METHODS

Ninety mandibular molars with straight (n = 45) and curved (n = 45) mesiobuccal root canals were contaminated with polymicrobial clinical samples. Teeth were divided into three subgroups (n = 14) according to the file systems and the curvature. Canals were instrumented with TN, Rotate, and PTG, respectively. Sodium hypochlorite and EDTA were used as irrigants. Intracanal samples were taken before (S1) and after (S2) instrumentation. Six uninfected teeth were used as negative controls. The bacterial reduction between S1 and S2 was measured by ATP assay, flow cytometry, and culture methods. Kruskal-Wallis and ANOVA tests were followed by the Duncan post hoc test (p < 0.05).

RESULTS

Bacterial reduction percentages were similar for the three file systems in straight canals (p > 0.05). However, PTG showed a lower reduction percentage of intact membrane cells in flow cytometry than TN and Rotate (p = 0.036). For the curved canals, no significant differences were obtained (p > 0.05).

CONCLUSION

Conservative instrumentation of straight and curved canals using TN and Rotate files resulted in similar bacterial reduction compared to PTG.

CLINICAL RELEVANCE

The disinfection efficacy of conservative instrumentation is similar to conventional instrumentation in straight and curved root canals.

Quantitative Assessment of Apically Extruded Debris after Single-Files Supplemental Retreatment considering Apical Patency Influence: In Vitro Study

Objective

This study aims to assess the impact of re-establishing apical patency on the quantity of debris extruded through the apex after three supplementary retreatment files (TruNatomy (TRN), WaveOne Gold (WOG), and XP endo Finisher R (XPFR)).

Materials and Methods

Eighty single-rooted mandibular premolars were prepared with ProTaper Universal rotary systems (PTU) up to F3 and obturated. The samples were divided into two main groups according to the presence or absence of the apical patency (n = 40), GI with apical patency and GII without apical patency. Based on the file system, which was adopted to eliminate the previous filling, each group had four subgroups (n = 10). In GI PTUR and GII PTUR, ProTaper Universal retreatment files (PTUR) were utilized only to remove the most primary filling material (control groups). In the other groups (PTUR) used, it was first followed by supplementary files. The quantity of debris extruded by different retreatment file systems was determined and compared to the corresponding control group with or without apical patency. Data were analyzed using a two-way ANOVA with a post hoc Tukey's multiple comparison test at a 5% significance level.

Results

There was a statistically significant difference among the control and experimental groups. XPFR had the least quantity of extruded debris. Apical patency did not affect the debris extrusion.

Conclusion

All tested files led to a significant apical debris extrusion regardless of apical patency.

Mechanical Properties of the New Generation RACE EVO and R-Motion Nickel-Titanium Instruments

This study aimed to evaluate and compare the dynamic cyclic fatigue, torsional and bending resistance of two novel RACE EVO (FKG Dentaire SA, La Chaux de Fonds, Switzerland) and R-Motion (FKG) nickel−titanium instruments with traditional RaCe (FKG) instruments. RACE EVO, R-Motion and RaCe instruments with a size of 25 and taper of 0.06 were used. A dynamic cyclic fatigue test was used to assess the time to fracture. The fractured surfaces were further analyzed using scanning electron microscopy at ×350 and ×3000 magnifications. A torsional resistance test was performed to measure the maximum torsional strength and angle of rotation. Phase transformations with temperature were evaluated using differential scanning calorimetry. The results were statistically analyzed with a Kruskal−Wallis test at a 5% significance level. R-Motion had the highest time to fracture and the lowest torsional and bending resistance, whereas RaCe had the lowest time to fracture and the highest torsional and bending resistance (p < 0.05). In relation to the angle of rotation, RACE EVO instruments had the highest deformation capacity followed by R-Motion and RaCe instruments (p < 0.05). The greater cyclic fatigue resistance and lower torsional and bending resistance results indicate that the novel R-Motion and RACE EVO instruments are less rigid and more flexible than RaCe instruments.

The effect of the NiTi alloy modification and the taper of endodontic instruments on the cyclic fatigue resistance

Background/Aim: The fracture of engine-driven instruments during root canal treatment has been tried to be eliminated by developing the manufacturing process of the files. The aim of this study was to assess cyclic fatigue resistance (CFR) of the two different rotary filesEdgeSequel™ Sapphire (ES) and Race® Evo (RE)which are produced by two different manufacturing technologies. Material and Methods: While RE is manufactured from heat-treated NiTi alloy with the electropolished surface, ES undergoes a non-disclosed thermal treatment called FireWire heat treatment. The CFRs of ES and RE comprising of similar tip size and taper (15/.04 and 25/.04) were compared on a cyclic fatigue device with an artificial stainless-steel canal (60° curvature, 5 mm radius, 1.5 mm width, and 3.0 mm depth). The continuous water spray with a syringe at 35.5°C was used to decrease the friction and to simulate in vivo conditions. All procedures were performed at recommended speed and torque for both files until fracture occurred. The time to failure (TF) was recorded and the number of cycles to failure (NCF) was calculated. The Weibull calculations (Weibull modulus, R2, predicted cycles, and time for 99 % survival) for NCF and TF were also done. The data were statistically analyzed with the independent two-sample t-test and the paired two-sample t-test. The significance level was set at p < 0.05. Results: Both ES and RE showed a better CFR in 15/.04 tip size than 25/.04 (P < 0.05). The TF of the ES were higher than the RE (P < 0.05). The highest and lowest Weibull modulus values were obtained with RE 15/.04 and RE 25/.04, respectively. Conclusions: Both the tip diameter and alloy modification of the instruments affected the CFR. FireWire heat treatment was associated with longer TF. The bigger the tip diameter, the lower the CFR for both tested products.