The Contribution of Various In Vitro Methodologies to Comprehending the Filling Ability of Root Canal Pastes in Primary Teeth.

A void-free obturation during root canal treatment on primary teeth is currently very difficult to attain. In this study, the pulpectomy filling abilities of Bio-C Pulpecto (Angelus, Basil, Londrina, Paraná, Brazil) and of zinc oxide eugenol, or "ZOE" (DenPro, Prevest, New York, NY, USA), were compared using several in vitro techniques. Therefore, 30 primary anterior teeth were used in the present in vitro study. Analysis of variance (ANOVA), including a multiple comparison procedure (Holm-Sidak method, Dunn's Method, or Tukey test), was used. On micro-CT, Bio-C Pulpecto exhibited higher void percentages than did ZOE (10.3 ± 3.8%, and 3.5 ± 1.3%), respectively (p < 0.05). With digital microscopy, higher total void percentages were found in the BC (13.2 ± 26.7%) group compared to the ZOE (2.7 ± 2.8%) group (p < 0.05). With the CLSM, mean tubular penetration depths were higher for Bio-C Pulpecto than for ZOE in all canal thirds (p < 0.05). SEM images demonstrated no tags into dentinal tubules in either group throughout the three thirds. Moreover, higher statistically significant flowability was found for Bio-C (2.657 ± 0.06 mm) compared to ZOE (1.8 ± 0.13 mm) (p < 0.05). The findings of this study indicate that neither ZOE nor Bio-C Pulpecto appears to meet the criteria for an ideal root canal filling paste for primary teeth. This study laid the groundwork for future research by determining how micro-CT, digital microscopy, SEM, and CLSM contribute to our understanding of the filling process of primary teeth. More thorough research on the mechanism of root canal obturation on primary teeth is required to achieve a long-term successful root canal therapy in young children.

Influence of Coronal Flaring on the Shaping Ability of Two Heat-Treated Nickel-Titanium Endodontic Files: A Micro-Computed Tomographic Study.

Nickel-titanium (NiTi) usage is associated in endodontics with some complications including canal transportation. Centering ability of a NiTi file is the ability to stay centered in the root canal system during instrumentation. Any undesirable deviation from the natural canal path is indicated as canal transportation. A possible strategy to improve the centering ability of NiTi instruments is the pre-enlargement of the coronal third of the root canal to minimize coronal interferences. This procedure is known as coronal flaring. The aim of this study was to perform a micro-computed tomographic (micro-CT) evaluation of the effect of coronal flaring on canal transportation and centering ability of two heat treated nickel-titanium rotary instruments, 2Shape (Micro Mega, Besançon, France) and HyFlex CM (Coltène Whaledent, Altstätten, Switzerland). Thirty extracted mandibular molars with two independent mesial canals were selected and randomly instrumented (n = 15 canals) with One Flare (Micro Mega, Besançon, France) before HyFlex CM, HyFlex CM (without coronal flaring), One Flare before 2Shape and 2Shape (without coronal flaring). One Flare (Micro Mega, Besançon, France) was introduced 4 mm below the canal entrance for canals prepared with coronal flaring. HyFlex CM and 2Shape were used accordingly to manufacturers' instructions. New files were used for each canal. During and after instrumentation, irrigation procedures were performed. Micro-CT images were obtained pre- and post-preparation to measure and record root canal transportation and centralization. They were reconstructed from root apex to canal orifices, generating approximately 1000 sections per specimen. The anatomical thirds were determined by dividing the number of cross-sectional slices by three. Root canal transportation and centralization were determined by Gambil method, and the mean values were analyzed by repeated measures analysis of variance followed by multiple comparisons of Bonferroni to compare the different instrumentations procedures and the root thirds (p < 0.05). As for root canal transportation, 2Shape reported significantly higher values compared to HyFlex CM in the cervical region independently from the coronal flaring. In the apical region, 2Shape caused significantly minor canal transportation when used with coronal flaring with compared with the absence of coronal flaring. Regarding the centralization, HyFlex CM showed higher values than 2Shape in the cervical, independently from coronal flaring. In the apical region, 2Shape with coronal flaring exhibited significant major centering ratio, compared with not. Within the limitations of this study, coronal flaring reduced canal transportation and improved centralization of the 2Shape files in the apical section while it had no significant influence on shaping ability of the HyFlex CM instruments. Coronal flaring could represent a valid strategy to improve the shaping ability of NiTi files knowing that its benefit could be influenced by the shaping file used.

Influence of different heat treatments and temperatures on the cyclic fatigue resistance of endodontic instruments with the same design.

OBJECTIVES: To evaluate the influence of different heat treatments and temperatures on the cyclic fatigue resistance of 2Shape instruments (Micro Mega, Besancon, France) with the same design. MATERIALS AND METHODS: A total of 80 2Shape TS1 (#25/.04) and 80 TS2 (#25/.06) files with different heat treatments (no heat-treated, NHT; C-Wire; T-Wire; CM-Wire) were tested at room (25° ± 1 °C) and body (37° ± 1 °C) temperatures in 16-mm stainless steel artificial canal with a curvature of 60° and 5 mm of radius. Files were tested in continuous rotation at 300 rpm using a customized device. Cyclic fatigue resistance was expressed in the number of cyclic to fracture (NCF). The phase transformation temperature of each file was determined by differential scanning calorimetry. Data were statistically analyzed using the two-way ANOVA and the Bonferroni post-hoc test with p < 0.05. RESULTS: All CM-Wire TS1 and TS2 files showed higher NCF than the other groups at both temperatures (p < 0.001). C-Wire TS2 showed higher resistance than NHT and T-Wire TS2 (p < 0.001), with no significant differences between the last two. Body temperature significantly decreased NCF of all tested files (p < 0.05) except for NHT and T-Wire TS1. CONCLUSIONS: Body temperature negatively affected the cyclic fatigue resistance of C-Wire and CM-Wire TS1 and of all TS2 files compared with room temperature. The CM-Wire instruments exhibited the highest cyclic fatigue resistance of all tested files. CLINICAL RELEVANCE: Heat-treated nickel-titanium files can differently perform according to environmental temperature and file dimensions. The CM-Wire 2Shape prototypes displayed the highest flexural resistance in all experimental conditions.

Influence of NiTi Wire Diameter on Cyclic and Torsional Fatigue Resistance of Different Heat-Treated Endodontic Instruments.

We compared the mechanical properties of 2Shape mini TS2 (Micro-Mega, Besançon, France) obtained from 1.0 diameter nickel-titanium (NiTi) wires and 2Shape TS2 from 1.2 diameter nickel-titanium (NiTi) wires differently thermally treated at room and body temperature. We used 120 NiTi TS2 1.0 and TS2 1.2 files made from controlled memory (CM) wire and T-wire (n = 10). Cyclic fatigue resistance was tested by recording the number of cycles to fracture (NCF) at room and body temperatures using a customized testing device. Maximum torque and angle of rotation at failure were recorded, according to ISO 3630-1. Data were analyzed by a two-way ANOVA (p < 0.05). The CM-wire files had significantly higher NCFs at both temperatures, independent of wire dimensions. Testing at body temperature negatively affected cyclic fatigue of all files. The 1.0-mm diameter T-wire instruments showed higher NCF than the 1.2-mm diameter, whereas no significant differences emerged between the two CM wires at either temperature. The maximum torque was not significantly different across files. The TS2 CM-wire files showed significantly higher angular rotation to fracture than T-wire files. The TS2 CM-wire prototypes showed higher cyclic fatigue resistance than T-wire prototypes, regardless of wire size, exhibiting suitable torsional properties. Torsional behavior appears to not be affected by NiTi wire size.

Physicochemical and Antibacterial Properties of Conventional and Two Premixed Root Canal Filling Materials in Primary Teeth.

In this study, some physicochemical and antibacterial properties of three root canal filling materials for primary teeth, Calplus "CP" (Prevest DenPro, Lewes, DE, USA), Bio-C Pulpecto "Bio-CP" (Angelus, Basil, Londrina, Paraná, Brazil), and Zinc Oxide and Eugenol "ZOE" (Prevest DenPro, Lewes, DE, USA) were compared. For each material, the pH, solubility, contact angle, and crystalline microstructure under SEM were evaluated. Their antibacterial activity against Enterococcus faecalis was determined through direct tests. The Kruskal−Wallis test was used to analyze the results using a one-way analysis of variance on ranks. All the materials had an alkaline pH at 3, 24, and 72 h, with CalPlus having the highest (p < 0.05). Bio-CP was more soluble during the evaluation period (24 h) than ZOE and CalPlus (p < 0.05). Bio-CP and ZOE demonstrated the creation of crystallite structures on their surfaces after immersion in PBS at 37 °C, whereas CalPlus showed none. The lowest contact angle was observed for Bio-CP (53 ± 1.5°); contact angles of (86 ± 4°) and (96 ± 1°), respectively, were observed after 10 s of the deposition of the water drop for CalPlus and ZOE. In conclusion, according to this study, there is still a need to develop new filling materials for primary teeth. ZOE, CalPlus and Bio-CP demonstrated different physicochemical and antibacterial properties, but none of the materials had optimal properties and could be considered the most suitable filling material for primary teeth pulpectomy. Bioceramics in their current state are not an alternative. The physicochemical and antibacterial properties still need improvement to fit the intricate anatomy of primary teeth.

The Pushout Bond Strength of Three Calcium Silicate-based Materials in Furcal Perforation Repair and the Effect of a Novel Irrigation Solution: A Comparative In Vitro Study.

AIM: To evaluate the pushout bond strength of three calcium silicate-based materials used as furcal perforation repair materials and the effect of root canal irrigants on the pushout strength of the tested repair materials. MATERIALS AND METHODS: Furcal perforations measuring 1.3 mm in diameter were made in the center of the furcation area of 90 extracted human mandibular molars. The teeth were then randomly divided into three groups (n = 30) according to the repair material: Biodentine (Septodont, St-Maur-des-Fossés, France), PD-MTA White (Produits Dentaires, Vevey, Switzerland), and K-Biocer (REKITA, Lebanon). The specimens were stored at 100% humidity at 37°C for 72 hours. They were later divided into three subgroups (n = 10) based on the irrigation protocol: 2.5% sodium hypochlorite, BioAKT (Metabolic substrate, New Tech Solutions s.r.l., Brescia, Italy), and a control group. After incubation for 48 hours, the dislodgement resistance of the samples was measured using a universal testing machine. RESULTS: The mean bond strength was significantly different between repair materials in the irrigation control group (p-value <0.001). With PD-MTA White and K-Biocer, the mean bond strength was not significantly different between irrigation groups (p-value = 0.681). The mean bond strength of Biodentine was significantly different between irrigation groups (p-value = 0.002); it was the highest with BioAKT. CONCLUSION: Biodentine showed a high performance as a perforation repair material and its resistance to dislocation increased after being exposed to BioAKT. K-Biocer had the lowest pushout bond strength. PD-MTA White showed intermediate bond strength and was not affected by the tested irrigants. CLINICAL SIGNIFICANCE: The bond strength of endodontic materials to root dentin is an important factor to consider for long-term clinical success since the teeth are constantly subjected to masticatory forces.

Effectiveness of the REvision System and Sonic Irrigation in the Removal of Root Canal Filling Material from Oval Canals: An In Vitro Study.

This study aimed to evaluate the effectiveness of the Endostar REvision system (Poldent, Warsaw, Poland) in the removal of filling materials from oval root canals using sonic irrigation as an additional cleaning method. Thirty human-extracted mandibular premolars with oval canals were prepared using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland) up to instrument F1 (20/.07), and then filled by the continuous wave vertical compaction technique using pulp canal sealer EWT (Sybron Dental Specialties, Orange, CA, USA). The teeth were randomly divided into two groups (n = 15) according to the instrumentation system and the additional cleaning method, as follows: REvision (30/.08, 25/.06) with EQ-S sonic activation (Meta Biomed, Chungcheongbuk-do, Korea), REvision (30/.08, 25/.06) without additional activation. All specimens were sectioned longitudinally at 3 and 7 mm from the apex, and analyzed using digital microscopy (KEYENCE, Osaka, Japan) to measure the total area of the residual obturation materials, followed by SEM analysis. The data on the percentage of remaining filling material were analyzed by Kruskal−Wallis one-way Analysis of Variance on ranks. None of the retreatment protocols completely removed the filling material from the root canals (p > 0.05); the retreatment technique using sonic activation showed statistically less residual filling materials than the retreatment technique using irrigants without activation at the coronal third (p < 0.05), whilst no significant difference was found between both tested groups at the apical and middle thirds (p > 0.05). The REvision system showed promising results in the removal of filling materials from oval canals.

The Effectiveness of Different Irrigation Techniques on Debris and Smear Layer Removal in Primary Mandibular Second Molars: An In Vitro Study.

AIMS: The aim of the present in vitro study was to compare the effectiveness of passive ultrasonic irrigation (PUI), sonic irrigation, and mechanic dynamic activation on the removal of debris and smear layer from primary mandibular second molars during pulpectomy. MATERIALS AND METHODS: Mesial roots of 48 primary mandibular second molars were prepared with an R-motion 21 mm file (30/0.04) (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland), irrigated with 1% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA), and divided into four groups (n = 24 canals) according to the final irrigation activation technique: control group without activation, PUI with Ultra-X (Eighteeth, Changzhou, China), mechanical activation with XP-endo Finisher (FKG), and sonic irrigation with EQ-S (Meta Biomed, Chungcheongbuk-do, Korea). The roots were split longitudinally and analyzed using scanning electron microscopy (SEM). The presence of debris and smear layer was assessed using a 5-grade scoring scale with 200× and 1000× magnification, respectively. The Kruskal-Wallis and Friedman tests were used for data analysis. RESULTS: The activation of the irrigant significantly improved debris and smear layer removal (p < 0.001). There was no significant difference between Ultra-X, XP-endo Finisher, and EQ-S (p > 0.05). No activation technique was able to completely eliminate debris and smear layer from the root canals of primary mandibular second molars. CONCLUSIONS: During pediatric pulpectomy, the irrigation protocol must include activation of the irrigation solutions using either ultrasonic, sonic, or mechanical activation techniques to enhance the removal of debris and smear layer for a better prognosis. CLINICAL SIGNIFICANCE: During root canal treatment on primary teeth, the clinician must incorporate an activation technique in the irrigation protocol to enhance the removal of debris and smear layer and increase the success of the treatment.

Apically Extruded Debris in Curved Root Canals Using a New Reciprocating Single-File Shaping System.

INTRODUCTION: The present study addresses the influence of 5 different shaping file systems on apical debris extrusion (AED) using 2 different irrigation protocols. METHODS: One hundred fifty mandibular first permanent molars were divided into 2 groups and 10 subgroups. The mesial root canals were shaped using One Reci (MicroMega), WaveOne Gold Primary (Dentsply Sirona, York, PA), and ProTaper Next (Dentsply Sirona) using reciprocating motion and One Curve (MicroMega) and ProTaper Next using continuous rotation. The first group and the second one were respectively irrigated with 10 and 5 mL distilled water. RESULTS: When the same instrumentation technique was used, the G10 mL subgroups showed statistically lower AED than the G5 mL subgroups (P < .05). The One Reci and One Curve subgroups, in both groups, produced statistically lower AED than the remaining subgroups. CONCLUSIONS: The cross section of the instrument could be the main parameter in determining the amount of AED. The irrigation volume used during the shaping procedure might affect the amount of AED.

Assessment of root canal transportation of 2Shape and ProTaper gold in mandibular molar mesial canals: A micro-computed tomographic study.

The aim of this study was to compare shaping abilities of Protaper Gold® (PTG) and 2Shape® (TS) by using a new automatic process and micro-computed tomography (Micro-CT). 32 first mandibular molars with two separate mesial canals were selected. Only mesial roots were prepared with PTG and TS. Pre- and post-operative scans were performed using Micro-CT to provide volumes with a voxel size of 20 µm. Volumes, non-instrumented area, amount of transportation and centering ability in coronal, middle and apical third shaping time and procedural errors were recorded. TS and PTG increased the endodontic volume of 2.98 mm3 (±1.56) and 3.21 mm3 (±1.78) respectively with no statistical difference (p = .168) and no procedural errors. No significant difference was found concerning canal transportation among groups but only within the same group PTG (p value < .001) and TS (p value < .001). The mean centering ratio was significantly different only between the section levels for PTG (p value < .001) and TS (p value = .01); it was significantly reduced in the cervical third. The percentage of untouched canal walls ranged between 29.78% (±15.145) and 36.60% (±11.968) respectively for PTG and TS with no statistical difference among groups (p value = .168). TS and PTG with post machining heat treatment were able to produce centered preparations with no significant difference or procedural errors. TS system provided a shorter preparation time than PTG files.

Anatomical Investigation of Middle Mesial Canals of Mandibular Molars in a Middle Eastern Population: A Cross-sectional Cone-beam Computed Tomography Study.

AIM: To identify the prevalence of middle mesial canals (MMC) in mandibular molars in a Lebanese population to determine the relationship between MMC and different factors (age, sex, and tooth type) and to examine the canal's morphological aspects (category, length, orifice position, and dentin width toward furcation). MATERIALS AND METHODS: The presence of MMC in the mesial roots of 505 mandibular molars of 200 patients was analyzed using cone-beam computed tomography (CBCT). Then, the position of the MMC orifices with respect to the pulpal floor and the main canals orifices, and the width of dentin along the canal toward the furcation were determined using 3D Slicer 4.10.1. RESULTS: In all, 14.65% of the first and second mandibular molars presented an MMC. A higher frequency of confluent canals was noted mostly joining the mesiobuccal canal (MBC). Gender appears to be a factor influencing the prevalence of MMCs, contrary to age-groups and tooth type. In mandibular first molars, the orifice is located at a mean distance of 1.22 ± 0.44 mm from the pulpal floor, 1.42 ± 0.53 mm from the MBC orifice, and 1.57 ± 0.60 mm from the mesiolingual canal (MLC) orifice. The width of dentin toward the furcation varies between 0.95 and 2.29 mm. In mandibular second molars, the orifice is located at a mean distance of 1.00 ± 0.51 mm from the pulpal floor, 1.39 ± 0.60 mm from the MBC orifice, and 1.37 ± 0.50 mm from MLC orifice. The width of dentin toward the furcation varies between 0.71 mm and 2.22 mm. CONCLUSION: Middle mesial canal is present in 14.65% of mandibular molars in the Lebanese population, with its orifice located under the pulpal floor. The majority of MMCs join the MBC. CLINICAL SIGNIFICANCE: Middle mesial canal is not a rare finding in the Lebanese population (14.65%). Clinicians should take time to search for this canal in the isthmus between the main mesial canals.

Evaluation of Two Shaping Systems and Two Ultrasonic Irrigation Devices in Removing Root Canal Filling Material from Mesial Roots of Mandibular Molars: A Micro CT Study.

We assessed the efficiency of two shaping file systems and two passive ultrasonic irrigation (PUI) devices for removing filling material during retreatment. The mesial canals from 44 extracted mandibular molars were prepared and obturated. The teeth were randomly divided into two groups, and then one group was retreated with Reciproc R25 (VDW, Munich, Germany) (n = 44) and the other group was retreated with 2Shape (TS, Micro Mega, Besançon, France) (n = 44). A micro-computed tomography (CT) scan was taken before and after the retreatment to assess the volume of the filling material remnants. The teeth were then randomly divided into four groups to test two different PUI devices: Irrisafe (Satelec Acteon Group, Merignac, France) and Endo Ultra (Vista Dental Products, Racine, WI, USA). The teeth in Group A were retreated with 2Shape to test the Endo Ultra (n = 22) device, the teeth in Group B were retreated with 2Shape in order to test the Irrisafe (n = 22) device, the teeth in Group C were retreated with Reciproc to test the Endo Ultra (n = 22) device, and Group D was retreated with Reciproc to test the Irrisafe (n = 22) device. A third micro-CT scan was taken after the retreatment to test the PUIs. The percentage of Gutta-Percha (GP) and sealer removed was 94.75% for TS2 (p < 0.001) and 89.3% for R25 (p < 0.001). The PUI significantly enhanced the removal of the filling material by 0.76% for Group A (p < 0.001), 1.47% for Group B (p < 0.001), 2.61% for Group C (p < 0.001), and by 1.66% for Group D (p < 0.001). 2Shape was more effective at removing the GP and sealer during retreatment (p = 0.018). The supplementary approach with PUI significantly improved filling material removal, with no statistical difference between the four groups (p = 0.106).

The influence of brushing motion on the cutting behavior of 3 reciprocating files in oval-shaped canals.

INTRODUCTION: The purpose of this study was to compare the cutting efficiency of 3 reciprocating single-file systems used with a brushing motion in oval-shaped canals. METHODS: Sixty premolars with single oval canals were selected and randomly assigned to 3 groups according to the file used in canal instrumentation: R25 Reciproc (VDW, Munich, Germany), Primary WaveOne ((Dentsply Maillefer, Ballaigues, Switzerland), and a novel prototype instrument (UFile; MicoMega, Besancon, France). Instrumentation was performed in 4 consecutive steps; according to manufacturers' instructions, 5 brushing strokes against the buccal wall with a nonworking instrument followed by another 5 and 15 brushing strokes with a working file. Cone-beam computed tomographic scans were taken after each step of preparation. Pre- and postinstrumentation images were superimposed at the apical and midroot levels and then evaluated in terms of changes in the maximum buccolingual (ΔBL) and mesiodistal dimensions (ΔMD). RESULTS: Instrumentation with a brushing motion resulted in the following findings. At the apical levels, no significant difference was found in ΔBL for the 3 groups (P > .05). However, ΔMD was significantly less for the Reciproc (P = .006) and UFile (P = .03) groups. At the midroot levels, the UFile group showed the highest significance in terms of ΔBL (P < .0001) but the lowest in terms of ΔMD (P = .003). ΔMD was significantly the highest for the WaveOne group at the midroot levels (P = .05). CONCLUSIONS: The prototype file was more efficient than the other files at the midroot levels, whereas all systems acted the same at the apical levels. The increase in the number of brushing strokes resulted in more dentinal cutting in the direction of those strokes.

Irrigant flow beyond the insertion depth of an ultrasonically oscillating file in straight and curved root canals: visualization and cleaning efficacy.

INTRODUCTION: The purpose of this study was to evaluate the influence of the insertion depth of an ultrasonically oscillating file on the ability to remove dentin debris from simulated canal irregularities in an extracted tooth model of a straight root canal and its influence on the flow of irrigant in both straight and curved canals. METHODS: A tooth model with artificial depressions in 1 canal wall at 0.5, 2, 4, and 6 mm from the working length was used. Ultrasonic-activated irrigation was performed with the file inserted 1, 2, 3, 4, or 5 mm short of the working length. Dye penetration and high-speed recordings of the flow in straight and curved canals showed the static and dynamic behavior of the flow during ultrasonic activation. RESULTS: The overall cleaning efficacy decreased with increasing distance between the file and the apex, with the depressions next to the file and within 3 mm in front of the file being the cleanest. The flow observed from the visualization experiments matched this distance, suggesting a direct relation between flow and cleaning. The observed flow depth increased with increasing power setting; the curvature of the root canal had no influence on the flow depth. High-speed imaging showed a start-up phase with deeper fluid activation than in the steady phase afterward. CONCLUSIONS: The ultrasonically oscillating file could remove dentin debris up to 3 mm in front of the file tip, coinciding with the extent of the observed flow. The root canal curvature had no influence on the irrigant flow.