Cyclic fatigue resistance of two pediatric rotary files manufactured with different heat treatments: an in-vitro study.

Nickel-titanium (NiTi) instruments offer many advantages during endodontic instrumentation; however, the fracture risk within the canal remains a concern. Manufacturers continuously develop and introduce instruments to the market with supposedly enhanced cyclic fatigue resistance and increased flexibility, achieved through different proprietary manufacturing processes, the details of which have not been made public. In recent years, two rotary systems specially designed for deciduous teeth have been commercially available, but information about their performance is lacking. This investigation aimed to identify which manufacturing process provides better cyclic fatigue resistance: the AF-H Wire technology used in the AF baby rotary files (AF-f) or the CM-Wire technology used in the i3 Gold deciduous teeth rotary files (i3G-f). Forty rotary International Organization for Standardization (ISO) 25/04 files were tested in artificial canals with a standard geometry of 60° angle and 2.5 mm radius until fracture. The number of cycles to fracture was calculated, and the length of the fragments was measured. A scanning electron microscope (SEM) was used to examine the fracture surfaces and fragments. Energy dispersive spectroscopy (EDS) was used to determine the percentage weight of NiTi in each file. The statistical analysis (Mann-Whitney test) showed that the cyclic fatigue resistance of the AF-f was significantly higher (p < 0.0001) than that of the i3G-f. Additionally, there was a significant difference (p = 0.0419) in the length of the fractured fragments. All instruments showed one or more types of manufacturing defects and presented similar NiTi percentages by weight. The manufacturing process is critical to cyclic fatigue resistance, and there seems to be responsible for the difference in cyclic fatigue resistance between these similar instruments.

The effect of irrigation solution temperature and novel heat-treated rotary files on apical debris extrusion and canal preparation time.

This study aimed to compare apical debris extrusion and canal preparation time with ProTaper Gold (PTG) and ProTaper Ultimate (PTU) files at different temperatures. Mesio-buccal roots of 60 mandibular first molars were distributed into six groups depending on the file type (PTG, PTU) and irrigation solution temperature (20, 37, 45°C). During instrumentation, extruded debris were collected and weighed to measure the mass in milligrams. The canal preparation time was recorded in seconds. ANOVA followed by Bonferroni post-hoc tests were used for analysis. The amount of debris extrusion was significantly higher in PTU, which was affected by the irrigation solution temperature (p < 0.05). The difference in canal preparation time was not significant between the two file systems, however, it was significant between the different temperatures (p = 0.001). Both file systems had shorter canal preparation times at 20°C. The irrigation solution temperature could influence the debris extrusion and time of canal preparation.

Exploring morphometric transformations in temperature-sensitive NiTi instruments alongside real-time intracanal temperature dynamics.

AIM: This study was twofold: (i) it aimed to investigate the morphometric changes of three temperature-sensitive nickel-titanium (NiTi) instruments at different temperatures, and (ii) to conduct an in vivo real-time analysis of intracanal temperature changes. METHODS: Changes in the shape and length of XP-Endo Shaper, XP-Endo Finisher, and XP-Endo Finisher-R were evaluated in real time whilst heated in a temperature-controlled water bath from 22 to 45°C. Instruments were fixed to a laminated water-resistant 1 mm graph paper attached to a stone block. Instruments were imaged whilst subjected to increasing temperature using a digital camera attached to an operating microscope. From recorded videos, still frames were extracted at 10-s intervals and changes in the length and shape of each instrument were measured and changes were plotted against time. Moreover, the intracanal temperature of distal roots of lower molars was measured in vivo for patients attending the clinic for non-surgical root canal treatments. The temperature was measured using a K-type thermocouple probe inserted into the mid-root level after irrigating the canal with a solution set at room temperature (22°C) or heated to 45°C. The intraoral and intracanal temperatures were recorded using a video camera for 180 s at 5-s intervals to plot the change in the intraoral and intracanal temperature, after both irrigation solution temperatures, with time. RESULTS: The shape transformation of XP-Endo Shaper began at 31.5 ± 2.0°C and reached its optimal transformation at 35.1 ± 1.0°C. For the Finisher and Finisher-R, shape transformations began at 29.2 ± 1.9 and 26.9 ± 2.2°C reaching the optimal transformation at 33.9 ± 1.4 and 32.7 ± 1.7°C, respectively. The average decreases in lengths of XP-Endo Shaper, Finisher, and Finisher-R after full transformation were 0.43 ± 0.23, 1.07 ± 0.22, and 1.15 ± 0.22 mm, respectively. The intracanal temperature reached 32.9 ± 0.8 and 33.2 ± 1.0°C after 3 min of application of irrigation solutions set at 22 or 45°C, respectively. CONCLUSION: The tested instruments exhibited diverse changes in their shapes and lengths at varying temperatures. Despite the temperature of the irrigation solution, the intracanal temperature consistently remained lower than the intracanal temperature once equilibrium was reached. This highlights the importance of considering the temperature of irrigation solution during in vitro testing of endodontic instruments.

Assessment of biomechanical behavior of immature non-vital incisors with various treatment modalities by means of three-dimensional quasi-static finite element analysis.

The objectives of this study were to evaluate the stress distribution and risk of fracture of a non-vital immature maxillary central incisor subjected to various clinical procedures using finite element analysis (FEA). A three-dimensional model of an immature central incisor was developed, from which six main models were designed: untreated immature tooth (C), standard apical plug (AP), resin composite (RC), glass-fibre post (GFP), regeneration procedure (RET), and regeneration with induced root maturation (RRM). Mineral trioxide aggregate (MTA) or Biodentine® were used as an apical or coronal plug. All models simulated masticatory forces in a quasi-static approach with an oblique force of 240 Newton at a 120° to the longitudinal tooth axis. The maximum principal stress, maximum shear stress, risk of fracture, and the strengthening percentage were evaluated. The mean maximum principal stress values were highest in model C [90.3 MPa (SD = 4.4)] and lowest in the GFP models treated with either MTA and Biodentine®; 64.1 (SD = 1.7) and 64.0 (SD = 1.6) MPa, respectively. Regarding the shear stress values, the dentine tooth structure in model C [14.4 MPa (SD = 0.8)] and GFP models [15.4 MPa (SD = 1.1)] reported significantly higher maximum shear stress values compared to other tested models (p < 0.001), while no significant differences were reported between the other models (p > 0.05). No significant differences between MTA and Biodentine® regarding maximum principal stress and maximum shear stress values for each tested model (p > 0.05). A maximum strain value of 4.07E-03 and maximum displacement magnitude of 0.128 mm was recorded in model C. In terms of strengthening percentage, the GFP models were associated with the highest increase (22%). The use of a GFP improved the biomechanical performance and resulted in a lower risk of fracture of a non-vital immature maxillary central incisor in a FEA model.

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.

A CBCT based cross sectional study on the prevalence and anatomical feature of C shaped molar among Jordanian.

The prevalence and anatomical features of C-Shaped Mandibular Second Molars (MSMs) are rarely studied in Jordanian sub-population. This study then took a part to evaluate the prevalence of C-shaped in MSMs using cone-beam computed tomography (CBCT) in the Jordanian sub-population. It used a cross-sectional design and three thousand scans collected over eight years between 2011 and 2019. The data were then reviewed for whether they were fully formed of MSMs. A total of 2037 cases that had 2845 MSMs were evaluated to identify C-shaped canals at coronal, middle, and apical sites. An oblique slicing module perpendicular to the long axis of MSMs was used to evaluate the teeth. The type and frequency of C-shaped canals, as well as the correlations between sex and side (right/left) and between sex and groove direction (buccal/lingual) were measured using the chi-square test on SPSS software at the significance level of 95%. A total of 342 teeth of 243 patients were C-shaped molars, which comprised 12% of the patient's teeth and 99 of them as a bilateral C-shaped canal with mean age of 40 years and sex ratio of 2:1 between female and male. With the limitations of this study, the lingual groove and type 3 were the most common properties of MSM. Besides, the Jordanian population mostly had C-shaped canals.

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

The apically extruded debris caused by TruNatomy System (TRN), RACE EVO system (RE) and VDW Rotate (VR) systems in mandibular anterior teeth with ribbon-shaped root canals were compared. The root canals (n = 20 in each group) were irrigated with NaOCl 2.5%, and the extruded debris was collected at pre-weighted Eppendorf tubes. The amount of apically extruded debris (mg) and the treatment time (s) were recorded. Tukey pairwise comparisons were performed to compare groups with a 95% confidence level. VR had significantly less debris extrusion values and treatment time than RE and TRN (P < 0.05). Although no difference was observed between RE and TRN in terms of apically extruded debris (P > 0.05), a significant difference in favour of RE was observed in terms of treatment time (P < 0.05). All the instruments extruded debris at varying weights.

Evaluating In Vitro Performance of Novel Nickel-Titanium Rotary System (TruNatomy) Based on Debris Extrusion and Preparation Time from Severely Curved Canals.

INTRODUCTION: This laboratory-based study aimed to investigate the quantitative amount of apically extruded debris from severely curved root canals and the preparation time for the novel rotary system TruNatomy (TN; Dentsply Sirona, Charlotte, NC) compared with Reciproc Blue (RCB; VDW Dental, Munich, Germany), HyFlex (HyFlex Controlled Memory [HCM; Coltene/Whaledent, Altstatten, Switzerland] and HyFlex EDM [HEDM, Coltene/Whaledent]), and ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland) rotary systems. METHODS: One hundred mandibular molar human teeth with severe curvature of the mesiobuccal canal (25°-45°) were included in the present study. The specimens were randomly distributed into 5 balanced groups (n = 20): TN, RCB, HCM, PTN, and HEDM. The amount of extruded debris for each group during instrumentation at body temperature was collected in an Eppendorf tube. After desiccation, the mean debris weights for each group were calculated. The total preparation time for each group was also recorded. Data were statistically analyzed using the Kruskal-Wallis test at a significance level of P < .05. RESULTS: The HCM and HEDM groups extruded a significantly higher amount of debris than the other tested groups (P < .001). TN extruded the least amount of debris, but it was not significantly different compared with the RCB and PTN groups (P > .05). In terms of preparation time, the TN group did not show any significant difference compared with the other groups. CONCLUSIONS: All instrumentation systems extruded debris. TN was among the groups that produced the lowest amount of apically extruded debris that is clinically acceptable. The amount of apically extruded debris using the TN system was equal to 2 popular systems and statistically significantly less than 2 other popular systems studied.