Determination of the Minimum Instrumentation Size for Penetration of Irrigants to the Apical Third of Root Canal Systems

The effect of final irrigation with different solutions on smear layer removal and dentin erosion: A scanning electron microscope study

AIM

This study aimed to compare the effectiveness of initial irrigation with sodium hypochlorite (NaOCl) and final irrigation with QMix, 40% citric acid, and 17% ethylenediaminetetraacetic acid (EDTA) on smear layer removal and dentin erosion.

METHODOLOGY

Forty extracted human mandibular premolar teeth were randomly divided into four groups (n = 10) according to the type of final irrigants used: 17% EDTA, QMix, citric acid, and control (normal saline). Canals were mechanically prepared using ProTaper Next instruments to an apical size of X3. Subsequently, the roots were sectioned in a buccolingual direction. Scanning electron microscopy (SEM) was used to assess the presence of the smear layer and the amount of dentin erosion in the coronal, middle, and apical thirds of the root canals.

RESULTS

In regards to smear layer removal, there was a significant difference between the control group and the other tested groups. Moreover, it was significantly higher in the coronal and middle thirds than in the apical third. However, there were no significant differences between the groups of EDTA, QMix, and citric acid. Concerning dentin erosion, citric acid produced significantly more dentin erosion than the other tested groups.

CONCLUSION

Final irrigation with solutions had a higher ability to remove the smear layer in the coronal and middle thirds compared to the apical third. Of all the solutions tested, 40% citric acid had the most pronounced impact on dentin erosion, followed by 17% EDTA and QMix.

Smear layer removal efficacy of different irrigation techniques in conservatively instrumented root canals

Background/purpose

Establishing effective irrigation methods is warranted to ensure the predictability of minimally invasive root canal instrumentation. This study aimed to compare the smear layer removal efficacy of different irrigation techniques in root canals instrumented with TruNatomy nickel-titanium rotary instruments.

Materials and methods

Experiment 1: Extracted human mandibular incisors were instrumented using TruNatomy Shaping Files up to Small (#20/0.04), Prime (#26/0.04), or Medium (#36/0.03) (n = 17, each) and irrigated with EDTA, NaOCl, and again with EDTA using syringe irrigation (SI). Experiment 2: Extracted mandibular incisors were instrumented using TruNatomy Small and irrigated with EDTA and NaOCl as in Experiment 1, using (1) conventional laser-activated irrigation (LAI) with an erbium-doped yttrium aluminum garnet laser unit at 30 mJ/10 Hz (LAI 30/10) or 70 mJ/20 Hz (LAI 70/20), (2) photon-induced photoacoustic streaming (PIPS) (20 mJ/15 Hz), (3) ultrasonic-activated irrigation, or (4) SI (n = 13 each). Five additional canals served as negative controls (no irrigation). The smear layer on the canal wall was scored under scanning electron microscopy.

Results

In Experiment 1, the TruNatomy Small group exhibited significantly higher smear layer scores compared to the other groups in the apical and middle thirds. In Experiment 2, the LAI 70/20 and PIPS groups demonstrated significantly lower smear layer scores compared to the LAI 30/10 and SI groups in the apical third.

Conclusion

Conservative instrumentation using the TruNatomy Small reduced the cleaning efficacy of irrigation. However, PIPS performed satisfactory for smear layer removal without injury to the root canal wall.

Confocal laser scanning evaluation of the influence of ledges on root canal disinfection

The aim was to analyse the influence of an apical ledge on root canal disinfection. Forty-four single-rooted teeth were micro-CT scanned and inoculated with Enterococcus faecalis. In Group S shaping was performed with ProTaper Next (PTN) up to X3 at working length (WL). In Group L an apical ledge was created with K-Files #40 and shaping completed up to PTN X3. NaOCl 5% and EDTA 10% irrigant solutions were alternated. Confocal laser scanning microscope (CLSM) and viability staining were used to analyse the proportions of dead (red) and live (green) bacteria and penetration ability inside dentinal tubules. Data were analysed with the Mann-Whitney test with Bonferroni correction (p < 0.05). In Group L the amount of red fluorescence resulted significantly lower, and penetration ability was decreased in the apical and middle portion (p < 0.05). The presence of an apical ledge may negatively influence the disinfection both in the apical and middle third.

The effect of root canal preparation tapers on planktonic bacteria and biofilm reduction in the apical third: A correlative microtomography and microbiological laboratory study

AIM

To evaluate the influence of different preparation tapers on the reduction in planktonic bacteria and biofilms of Enterococcus faecalis and Candida albicans in the apical third (4 mm) of the mesial roots of mandibular molars, correlating decontamination with canal shape.

METHODOLOGY

After microtomography analysis for morphological standardization of the canals, 48 mandibular molar roots, each containing two canals (96 canals), were contaminated with E. faecalis and C. albicans and divided into four groups (n = 11) for canal instrumentation using ProDesign Logic 2 files with different tapers G (.03): # 25.03; G (.04): # 25.04; G (.05): # 25.05; and G (.06): # 25.06 and irrigation with 2.5% sodium hypochlorite. Four roots were examined under a scanning electron microscope (SEM) to qualitatively assess biofilm formation. Eight roots were used as the negative control group (samples were not contaminated). Bacteriological samples were taken exclusively from the apical third of the roots before and after chemical-mechanical preparation and bacterial counts were determined (CFU/mL). The final micro-CT scan was used to quantify the volume variation and unprepared canal area in the apical third. Statistical analysis was performed using the Kruskal-Wallis, Student-Newman-Keuls and Wilcoxon tests for analysis of microbiological data. anova and the Tukey or Games-Howell test were used for analysis of micro-CT data and Spearman's test for correlations (α = 5%).

RESULTS

All groups showed a significant reduction in bacteria (p < .05), with no statistically significant difference between groups. There was no significant difference in per cent volume increase between groups. The unprepared area (Δ%) was affected by the file used (p = .026) and was significantly lower for G (.06) compared to G (.03). There was no statistically significant correlation among bacterial reduction, volume and unprepared area (p > .05).

CONCLUSION

The different preparation tapers influenced root canal shaping in the apical third but did not improve decontamination in this region.

Irrigant dynamics of a back-to-back double side-vented needle in root canals with various tapers: a computational fluid dynamics study

Understanding the apical pressure and irrigant flow patterns in root canals is crucial for safe and effective irrigation. Therefore, this study aimed to assess the flow characteristics of irrigants in root canal models with varying tapers during final irrigation by employing various needle designs, including a back-to-back double-side-vented needle, through computational fluid dynamics. The root canal model was configured as a closed geometrical cone with a simulated apical zone (size 30) and features tapers of 4%, 6%, and 8%. Three needle types-open-ended needle (OEN), single side-vented needle (SSVN), and double side-vented needle (DSVN)-were investigated. The results indicated that for the 4% taper models, the open-ended needle generated the maximum apical pressure, followed by the double side-vented needle and the single side-vented needle. However, in the 6% and 8% tapering root canal models, the double-side-vented needle applied the lowest maximum apical pressure. Consequently, the DSVN can pose a risk for irrigant extrusion in minimally prepared canals due to heightened apical pressure. In wider canals, the DSVN exhibited lower apical pressure. The maximum irrigant replacement was observed with OEN compared to that of the closed-ended group for both flow rates. Additionally, compared with OENs, closed-ended needles exhibited nonuniform and lower shear wall stress.

Computational fluid dynamics investigation on the irrigation of a real root canal with a side-vented needle

BACKGROUND

Root canal therapy is one of the main treatments for root canal diseases, and effective irrigation is the key to successful treatment. Side-vented needle is one of the commonly used needle types in clinic. In the real root canal, due to the influence of the curvature of the root canal, the irrigation flow field in different needle directions shows obvious differences. At the same time, changes in root canal curvature and working depth will lead to changes in irrigation efficiency and the flow field. Both the mainstream of the irrigation flow and the shear stress near the wall changes significant. Consequently, either the replacement in the root canal or the removal efficiency of the smear layers is apparently modified.

MATERIALS AND METHODS

In this paper, the permanent root canal of the maxillary first molar prepared until 15/04 were scanned by micro-CT, and then imported into the software for 3D reconstruction. The key parameters of flushing efficiency of 30G side needle at different working depths of 4.75 mm, 5 mm, 5.25 mm and 5.5 mm were compared. Meanwhile, the simulated models with different curvatures of 0°, 5°, 10°, 20° and 30° based on the real root canal were reconstructed to investigate the curvature effect on the irrigation efficiency.

RESULTS

The results show that moderate working depth (such as 4.75 mm and 5.25 mm in present paper) helps to improve the replacement capacity of irrigation flow. At the same time, the apical pressure decreased as the working depth increased. The curvature of the root canal seriously affects the removal depth of the smear layers of the root canal. A root canal with a large curvature (especially 20° and 30°) can significantly improve the difficulty of irrigation.

CONCLUSIONS

(1) Moderate working depth helps to improve the displacement capacity, the ERD of the irrigation flow is generally improved at the working depths of 4.75 mm and 5.25 mm, and the apical pressure will decrease with the increase of working depth. (2) The large curvature of the root canal can significantly improve the difficulty of irrigation. The curvature of the root canal can severely influence the removal depth of the smear layer on the wall. It can be found both the span and the depth of the ESS for little curvatures (5° and 10°) root canals are higher than those for large curvatures (20° and 30°).

Expert consensus on irrigation and intracanal medication in root canal therapy

Chemical cleaning and disinfection are crucial steps for eliminating infection in root canal treatment. However, irrigant selection or irrigation procedures are far from clear. The vapor lock effect in the apical region has yet to be solved, impeding irrigation efficacy and resulting in residual infections and compromised treatment outcomes. Additionally, ambiguous clinical indications for root canal medication and non-standardized dressing protocols must be clarified. Inappropriate intracanal medication may present side effects and jeopardize the therapeutic outcomes. Indeed, clinicians have been aware of these concerns for years. Based on the current evidence of studies, this article reviews the properties of various irrigants and intracanal medicaments and elucidates their effectiveness and interactions. The evolution of different kinetic irrigation methods, their effects, limitations, the paradigm shift, current indications, and effective operational procedures regarding intracanal medication are also discussed. This expert consensus aims to establish the clinical operation guidelines for root canal irrigation and a position statement on intracanal medication, thus facilitating a better understanding of infection control, standardizing clinical practice, and ultimately improving the success of endodontic therapy.

The Effect of Master Apical Preparation Size on Healing Outcomes in Endodontic Treatment: A Systematic Review and Meta-Analysis

INTRODUCTION

The aim of this systematic review was to assess the existing literature and examine whether or not the size of apical enlargement during mechanical preparation affects the outcome of treatment in patients undergoing nonsurgical root canal therapy (NSRCT).

METHODS

MEDLINE (PubMed), Embase, Cochrane Library, and gray literature were searched (January 2000-May 2023). Study selection and data extraction were performed in duplicate. Eligible studies were critically appraised for risk of bias and quality of evidence and were meta-analyzed to estimate the treatment effects.

RESULTS

Two studies were included in the meta-analysis. The overall pooled success rate was 75.8%. The success rates of treatment with an apical size ≥ 30 and < 30 were 80.9% and 52.9%, respectively. Cases with an apical size ≥ 30 demonstrated significantly more favorable results (RR = 0.63, 95% Confidence Interval 0.46-0.79, P < .05). The overall quality of evidence was low.

CONCLUSIONS

With a low certainty of evidence, master apical preparation size ≥ 30 may result in an increased healing outcome in terms of clinical and radiographic evaluations.

Debris and Smear Layer Removal in Curved Root Canals: A Comparative Study of Ultrasonic and Sonic Irrigant Activation Techniques

The aim of this study was to compare the cleaning efficacy of three irrigant activation devices with a control of non-activated syringe and needle irrigation in curved root canals. Sixty human curved roots were endodontically prepared and divided into four groups (n = 15) with similar root curvature distributions. Final irrigation using 4% NaOCl was performed with a syringe and needle (30-G) alone, or with Eddy sonic powered irrigation system (polymeric tip #0.25/0.06), Endosonic ultrasonic activation (polymeric tip #0.25/0.03), or Irrisafe ultrasonic activation (stainless-steel tip, #0.25/0.00). SEM was used to evaluate cleaning efficacy, employing five-score systems for debris and smear layer. While no significant difference in debris removal was observed between Endosonic or Irrisafe activation and non-activated irrigation, Eddy sonic powered irrigation system significantly improved debris removal in the apical third of curved root canals. Smear layer removal was effective in coronal and mid-root sections for all groups but less so in the apical third. Thus, Eddy sonic powered irrigation system demonstrated higher efficacy in removing debris from the apical third of curved root canals compared with non-activated syringe and needle irrigation. However, all three irrigant activation systems exhibited no difference from the non-activated control in smear layer removal.

Influence of pulse energy, tip design and insertion depth during Er:YAG-activated irrigation on cleaning efficacy in simulated severely curved complex root canal systems in vitro

AIM

To investigate the influence of pulse energy, tip geometry and tip position in simulated 3D-printed root canals with multiple side canals at different levels in all directions on the cleaning performance of laser-activated irrigation (LAI) compared to sonic activation (EDDY) and conventional needle irrigation (NI).

METHODOLOGY

3D-printed root canal models (25/.06, length 20 mm, curvature 60°, radius 5 mm) with side canals (diameter 0.2 mm) at 2, 5 and 8 mm from the apex were filled with coloured biofilm-mimicking hydrogel. LAI (Morita AdvErL Evo, Kyoto, Japan) was performed with six settings (n = 20; pulse-energy, pulses per second [PPS], tip position): LAI1 (50 mJ, 25 PPS, P400FL, canal entrance [CE]), LAI2 (same as LAI1, but insertion depth 9 mm before the apical endpoint [AE] [corresponding to 1 mm above the first lateral canals]), LAI3 (80 mJ, 25 PPS, P400FL, 9 mm before AE), LAI4 (same as LAI 3, but at CE) for 3 × 20 s each, LAI5 (50 mJ, 25 PPS, P400FL 2 × 20 s, CE & R200T (30 mJ, 25 PPS, 1 × 20 s, 9 mm before AE), LAI6 (30 mJ, 25 PPS, R200T, 9 mm before AE, 3 × 20 s). A continuous irrigation (3 mL/20 s) using distilled water accompanied the irrigation cycles. NI and EDDY (3 × 20 s each; 3 mL/20 s irrigation, insertion AE minus 1 mm, amplitude 4 mm) served as control groups. Biofilm-mimicking hydrogel removal (ImageJ, NIH) was assessed for the entire system, the central canal and the lateral canals using standardized photographs with a microscope (Expert DN, Müller-Optronic) and statistically analysed was performed using Kruskal-Wallis and Dunn tests (p = .05). Irrigant extrusion beyond the foramina was also recorded.

RESULTS

LAI2 (99.08%; interquartile range [IQR]: 96.85-100.00) and LAI3 (97.50%; 96.24-100.00) achieved the significantly best and LAI6 (80.08%; 73.41-84.69) the significantly worst removal of hydrogel from the entire root canal system amongst all LAI configurations (p < .05). There were no significant differences between LAI6, EDDY (72.89%; 67.49-76.22) and manual irrigation (54.39%; 51.01-56.94) (p > .05). R200T laser tip caused significantly more often irrigant extrusion than all other techniques (p < .05).

CONCLUSION

Tip design, energy settings, and the positioning of the laser tip below the canal entrance caused an improvement in cleaning performance of the LAI. However, the small R200T tip created significantly more procedural errors (irrigant extrusion) due to higher concentrated energy.

Efficacy of a novel remotely-generated ultrasonic root canal irrigation system for removing biofilm-mimicking hydrogel from a simulated isthmus model

AIM

To evaluate the efficacy of a novel ultrasonic irrigation device, remotely-generated irrigation with a non-invasive sound field enhancement (RINSE) system, in removing biofilm-mimicking hydrogel from a simulated isthmus model and compare it with sonically- and ultrasonically-activated irrigation systems.

METHODOLOGY

A polycarbonate root canal model containing two standardized root canals (apical diameter of 0.20 mm, 4% taper, 18 mm long with a coronal reservoir) connected by three isthmuses (0.40 mm deep, 2 mm high, 4 mm long) was used as the test model. The isthmuses were filled with a hydroxyapatite powder-containing hydrogel. The canals were filled with irrigant, and the models were randomly assigned to the following activation groups (n = 15): EndoActivator (EA), ultrasonically activated irrigation (UAI), and RINSE system (RS). Syringe irrigation (SI) with a 30G needle served as the control. Standardized images of the isthmuses were taken before and after irrigation, and the amount of hydrogel removed was determined using image analysis software and compared across groups using anova (p < .05).

RESULTS

Hydrogel removal was significantly higher with the RS (83.7%) than with UAI, EA, or SI (p ≤ .01). UAI (69.2%) removed significantly more hydrogel than SI and EA (p < .05), while there was no significant difference between SI (24.3%) and EA (25.7%) (p = .978).

CONCLUSIONS

RINSE system resulted in the most hydrogel removal, performing better than UAI or EA. The effect of RS was also not reliant on the insert or tip entering the pulp chamber or root canal, making it particularly useful in conservative endodontics.

Efficacy of different irrigant activation techniques for cleaning root canal anastomosis

OBJECTIVE

This study compared in vitro the anastomosis cleaning efficacy of different irrigant activation techniques at different levels; control group non-activation (NA), passive ultrasonic irrigation (PUI) using Irrisafe, and EDDY sonic activation.

METHODS

Sixty anastomosis-containing mesial roots of mandibular molars were mounted in resin, sectioned at 2, 4, and 6 mm from the apex. Then reassembled and instrumented in a copper cube. For the irrigation technique roots were randomly divided into 3 groups (n = 20): group 1: NA, group 2: Irrisafe, group 3: EDDY. Stereomicroscopic images of anastomoses were taken after instrumentation and after irrigant activation. ImageJ program was used to calculate the percentage of anastomosis cleanliness. The percentage of cleanliness was calculated before and after final irrigation within each group and were then compared using paired t-tests. Intergroup and intragroup analyses were performed to compare between different activation techniques at the same root canal level (2, 4 and 6 mm) (intergroup) and to evaluate if each technique had different cleanliness efficacy according to the root canal level (intragroup) using one-way analysis of variance and post hoc tests (p < 0.05).

RESULTS

All three irrigation techniques significantly improved anastomosis cleanliness (p < 0.001). Both activation techniques were significantly better than the control group at all levels. Intergroup comparison revealed that EDDY significantly achieved the best overall anastomosis cleanliness. The difference between EDDY and Irrisafe was significant in favor to EDDY at 2 mm and insignificant at 4 and 6 mm. The intragroup comparison showed that improvement in anastomosis cleanliness (i2-i1) in the needle irrigation without activation group (NA) was significantly higher in the apical 2 mm level compared to the 4 & 6 levels. While the difference in anastomosis cleanliness improvement (i2-i1) between levels in both Irrisafe and EDDY groups was insignificant.

CONCLUSIONS

Irrigant activation improves anastomosis cleanliness. EDDY was the most efficient in cleaning anastomoses located in the critical apical part of the root canal.

CLINICAL RELEVANCE

Cleaning and disinfection of the root canal system followed by apical and coronal sealing is the key for healing or prevention of apical periodontitis. Remnants of debris and microorganisms retained within the anastomoses (isthmuses), or other root canal irregularities may lead to persistent apical periodontitis. Proper irrigation and activation are essential for cleaning root canal anastomoses.

A Comparative Evaluation of Antibacterial Efficacy of Moringa oleifera Leaf Extract, Octenidine Dihydrochloride, and Sodium Hypochlorite as Intracanal Irrigants against Enterococcus faecalis: An In Vitro Study

Objectives

The aim of this study is to investigate and compare the microbial efficacy of Moringa oleifera leaf extract, octenidine dihydrochloride (OCT), NaOCl, and their combinations as intracanal irrigants against Enterococcus faecalis.

Materials and Methods

Sixty single-rooted mandibular premolars were decoronated followed by root canal preparation. Each root specimen was autoclaved, inoculated with E. faecalis, and incubated at 37°C for 48 hr. Then, the specimens were divided into six groups based on the irrigation solution used: 2.5% NaOCl (Group 1), 0.1% OCT (Group 2), M. oleifera leaves extract (Group 3), a combination of M. oleifera extract and 1.25% NaOCl (Group 4), a combination of M. oleifera extract and OCT (Group 5) and normal saline (Group 6). Microbial samples were taken from each root canal before (S1) and after (S2) irrigation and the bacterial viability was assessed using colony-forming units (CFU) on bile esculin agar plates.

Results

Comparing the number of CFU/ml before and after irrigation showed a significant reduction (P < 0.001) in all studied groups. Comparison between the CFU/ml after irrigation by NaOCl and each of the combination groups showed a significant difference.

Conclusion

M. oleifera leaves extract and 0.1% OCT solutions have antibacterial effect against E. faecalis comparable to 2.5% NaOCl and might be used as root canal irrigants. The combination groups showed better antimicrobial activities than individual irrigants. However, further studies are required to investigate the biocompatibility and possible toxic effects of the tested irrigants.

Micro-Computed Tomography Evaluation of Minimally Invasive Shaping Systems in Mandibular First Molars

The aim of this study was to compare the shaping ability of a modified ProTaper Next technique (PTNm) with that of TruNatomy (TN) in lower molars mesial curved canals using micro-computed tomography (Micro-CT). Sixty mesial canals of first mandibular molars were randomly assigned between two groups (n = 30). After canal scouting with K-File #10, glide path and shaping were carried out with TN or PTNm systems. The PTNm sequence consists of ProGlider, followed by ProTaper Next X1 and apical finishing with NiTiFlex #25 up to working length (WL) to ensure adequate apical cleaning. Samples were scanned using micro-CT and pre- and post-shaping volumes were matched to analyse geometric parameters: the volume of removed dentin; the difference of canal surface; centroid shift, minimum and maximum root canal diameters; cross-sectional areas; the ratio of diameter ratios (RDR) and the ratio of cross-sectional areas (RA). Measurements were assessed 2 mm from the apex and in relation to the middle and coronal root canal thirds. Data were analysed using ANOVA (p < 0.05). No statistically significant differences were found between the groups for any parameter at each level of analysis, except for RA at the coronal level (p = 0.037). The PTNm system showed the tendency to enlarge more in the coronal portion with a lower centroid shift at apical level compared with TN sequence (p > 0.05). Both PTNm and TN sequences demonstrated similar maintenance of original anatomy during the shaping of lower molar mesial curved canals.

Does Low-Taper Root Canal Shaping Decrease the Risk of Root Fracture? A Systematic Review

Minimal root-canal preparation has been suggested to reduce the risk of root fracture, but as a result, satisfactory cleaning and shaping do not take place. Large-scale taper instrumentation can contribute to removing infected tissue; however, it may weaken the tooth structure. The aim of this systematic review is to evaluate whether root-canal shaping with low-taper instruments decreases the risk of root fracture, compared to high-conicity shaping. A search was performed on Ovid MEDLINE, PubMed, and the Web of Science. The inclusion criteria were: studies comparing the root fracture resistance of endodontically treated teeth, shaped with low- and high-conicity taper instruments, in human trials, and via in vitro study. The review includes all types of endodontically treated teeth, with various instrument tapers. The scientific search engines produced 328 results. Only 20 of the results were evaluated after screening. Based on the articles analyzed, it is not clear whether a taper difference can determine differences in root fracture resistance. No randomized controlled trial (RCTs) with long follow-ups have been published to date. It must also be taken into account that the in vitro studies do not consider the numerous differences that there are between in vitro and clinical evaluation. The review was registered on the PROSPERO website, with the protocol number CRD42020151451.

Influence of needle working length and root canal curvature on irrigation: a computational fluid dynamics analysis based on a real tooth

Backgrounds

To compare the irrigation efficiency with different needle working length and different root canal curvature based on a real unshaped root canal using computational fluid dynamics (CFD) method.

Methods

Images of the root canal of the maxillary first molar after being prepared to .04/15 were scanned using micro-CT, and then imported into the software for three-dimensional reconstruction. A palatal root canal with a curvature of 23.4° was selected as the experiment canal. The needle working length of the 30-G flat needle was 4.75 mm, 5 mm, 5.25 mm and 5.5 mm short of apical foramen respectively, the flow pattern, irrigation velocity, shear stress were compared. The modified curved canals with a curvature of 0°, 5°, 10°, 20° and 30°were reconstructed via software. The flat needle was replaced at the optical inserted depth, and key parameters of irrigation efficiency were analyzed.

Results

Decreased needle working length had a positive impact on irrigation efficiency. With the optimal needle working length, the replacement of the apical irrigation fluid, the effective velocity, and wall shear stress were significantly improved in more severely curved root canals. With the same needle working depth and analogous canal curvature, irrigation efficiency is higher in real canal than that of modified canal.

Conclusions

Short needle working depth, large curvature and the anomalous inner wall of canals help to improve irrigation efficiency.

Final irrigation protocols affect radicular dentin DMP1-CT expression, microhardness, and biochemical composition

OBJECTIVE

To evaluate the effect of several final irrigation protocols on radicular dentin microhardness, biochemical composition, and DMP1-CT expression.

MATERIALS AND METHODS

A total of 140 single-rooted human teeth were prepared with WaveOne Gold files and randomly distributed into 7 groups (n = 20) according to the final irrigation protocol: distilled water (DW); sodium hypochlorite-EDTA (NaOCl-EDTA); EDTA (EDTA); EDTA-NaOCl (EDTA-NaOCl); EDTA-chlorhexidine (EDTA-CHX); passive ultrasonic irrigation (PUI:NaOCl-EDTA); and PUI:NaOCl-EDTA-NaOCl. Dentin microhardness (n = 10) was evaluated in the root canal lumen using Vickers hardness tester. Immunohistochemical analysis (n = 5) was used to evaluate DMP1-CT expression. Dentin ultrastructure and biochemical composition were evaluated by using Raman and energy dispersive X-ray analysis (EDAX) (n = 5) with a scanning electron microscope (SEM). Analysis of variance (ANOVA) and Tukey test were performed (p˂0.05).

RESULTS

Raman spectra of the organic content and DMP1-CT expression were lower at the lumen canal in EDTA-NaOCl, PUI:NaOCl-EDTA, and PUI:NaOCl-EDTA-NaOCl when compared to control (p < 0.05). EDAX showed reduced values for calcium and phosphorus in EDTA-NaOCl, PUI:NaOCl-EDTA, and PUI:NaOCl-EDTA-NaOCl. SEM microphotography's showed completely cleaned dentin, permeable tubules, and dentin erosion, mainly when PUI was used. NaOCl-EDTA presented significantly higher microhardness values than PUI:NaOCl-EDTA-NaOCl (p < 0.05). PUI:NaOCl-EDTA-NaOCl exhibited the lowest Vickers hardness values of all groups.

CONCLUSION

The final irrigation protocols that used a final rinse with NaOCl and PUI showed a detrimental effect on radicular dentin DMP1-CT expression, biochemical composition, and microhardness.

CLINICAL RELEVANCE

The adequate irrigation protocol could be advantageous to preserve the radicular dentin ultrastructure, promote adequate adhesion, and sustain favorable conditions for biomineralization and regeneration.

Comparison of GentleWave system and passive ultrasonic irrigation with minimally invasive and conventional instrumentation against LPS in infected root canals

This study compared the effectiveness of GentleWave system (GWS) and passive ultrasonic irrigation (PUI) in removing lipopolysaccharides (LPS) from infected root canals after minimally invasive (MIT) and conventional instrumentation (CIT) techniques. Sixty first premolars with two roots were inoculated with fluorescent LPS conjugate (Alexa Fluor 594). Of those, twelve were dentin pretreated, inoculated with fluorescent LPS conjugate, and submitted to confocal laser scanning microscopy (CLSM) to validate the LPS-infection model. Forty-eight teeth were randomly divided into treatment groups: GWS + MIT, GWS + CIT, PUI + MIT, and PUI + CIT (all, n = 12). Teeth were instrumented with Vortex Blue rotary file size 15/0.04 for MIT and 35/0.04 for CIT. Samples were collected before (s1) and after a root canal procedure (s2) and after cryogenically ground the teeth (s3) for intraradicular LPS analysis. LPS were quantified with LAL assay (KQCL test). GWS + MIT and GWS + CIT were the most effective protocols against LPS, with no difference between them (p > 0.05). PUI + CIT was more effective than PUI + MIT (p < 0.05) but less effective than GWS + MIT and GWS + CIT. GWS was the most effective protocol against LPS in infected root canals using MIT and CIT techniques.

Effect of Various Irrigant Activation Methods and Its Penetration in the Apical Third of Root Canal-In Vitro Study

OBJECTIVE

 The objective of this study was to evaluate the irrigant penetration using iohexol dye with four irrigation techniques.

METHODOLOGY

 Single-rooted premolars were recently extracted and preserved in physiological saline solution. All the samples were standardized to 16 mm. Standard endodontic access was prepared using endoaccess bur (Dentsply Maillefer, Switzerland). The initial patency was established using #10 k file (Mani, Utsunomiya, Tochigi, Japan) to the working length. The cleaning and shaping were performed using the file system ProFit S3 in the following sequence: P0 (orifice enlarger), PF1 (yellow), PF2 (red) #25, and PF3 (blue) #30. The samples were randomly allocated in concealed opaque envelopes into four groups. This was performed by a trained dentist. Fifteen samples were allocated to one group. The groups were divided as follows: Group A-conventional needle (CN), Group B-side-vented needle (SVN), Group C-manual dynamic agitation (MDA), and Group D-EndoActivator (EA). The radiopaque dye irrigant agitation/activation was performed by one operator to prevent operator bias. Following irrigation using the different techniques, digital radiographs were taken, and the measurement was taken from the apical foramen to the point where the dye had penetrated apically for each tooth and the data were entered into an Excel sheet for all the four groups.

RESULTS

 Comparing the four groups, there was a statistically significant difference among the four groups (p < 0.05), thus, favoring the alternate hypothesis. EA had resulted in better penetration of the irrigant compared with the other three groups (p < 0.05).

CONCLUSION

 It was evident that irrigant penetration was best achieved with the use of an EA followed by MDA, SVNs, and then the CN when the preparation was done till size 30 (PF3 #30) using ProFit S3 rotary file system.

Present status and future directions -Management of curved and calcified root canals

Root canal curvature and calcification introduce factors that increase the risk of procedural accidents during root canal treatment. The inability to achieve patency to the apical third, asymmetrical dentine removal leading to transportation, perforation and instrument fracture inside the curved trajectories are some of the procedural problems that might jeopardize the management of intraradicular infection and result in poor treatment outcomes. In fact, curved and constricted canals introduce such complexity that total instrumentation concepts and specially designed instruments have been developed to deal with the challenge. This narrative review seeks to provide and consolidate the principles necessary for understanding the dynamics of curved and constricted canal management and to improve the understanding for future developments in this field.

Influence of apical preparation size and final irrigation protocol on the debridement of oval root canals

This study assessed the influence of apical preparation size and final irrigation protocol on the debridement of the apical third of oval root canals of mandibular molars. Seventy-seven distal roots were divided into 7 groups (n = 11): Control: without instrumentation or irrigation; Group 30CI: ProTaper Next (up to size 30; PTN) + conventional irrigation (CI); Group 30UAI: PTN + ultrasonically activated irrigation (UAI); Group 30XPF: PTN + XP-endo Finisher (XPF); Group 40CI: PTN + ProDesign Logic (up to size 40; PDL) + CI; Group 40UAI: PTN + PDL + UAI; and Group 40XPF: PTN + PDL + XPF. The total volume of irrigating solutions used per root canal in all the experimental groups was 33 mL of 2.5% sodium hypochlorite (NaOCl) and 6 mL of 17% ethylenediaminetetraacetic acid (EDTA). After specimen processing and histological analysis under a digital microscope (100x), the percentages of untouched canal walls (UCW) and remaining debris (RD) were assessed using Image J software. A descriptive and exploratory analysis was conducted, indicating that the data failed to meet the assumptions of an analysis of variance. Therefore, generalized linear models were used to assess the effects of the different instrumentation and irrigation protocols, as well as the interaction among them, on the percentage of UCW and RD. No significant difference was found among the irrigation protocols regarding the percentage of UCW, irrespective of apical preparation size (p>0.05). However, UCW and RD were significantly lower in groups 40CI, 40UAI and 40XPF than in groups 30CI, 30UAI and 30XPF (p<0.05). The percentage of RD was significantly lower in the UAI and XPF groups than in the CI groups, irrespective of apical preparation size (p<0.05). The difference between preparation sizes 30 and 40, with respect to RD, was higher when CI was used (p<0.05). In conclusion, instrumentation up to apical preparation size 40 resulted in lower percentages of UCW and RD than up to apical preparation size 30. Use of UAI or XPF resulted in lower percentages of RD than CI.

Comparison of Herbal Agents with Sodium Hypochlorite as Root Canal Irrigant: A Systematic Review of In Vitro Studies

During endodontic treatment, eliminating microorganisms from the root canals should be considered with utmost importance. Before filling the canal, every effort should be made to ensure optimal shaping and adequate disinfection of the root canal system. This systematic review aimed to compare the efficacy of herbal agents with sodium hypochlorite (NaOCl) in reducing the microbial load while used as a root canal irrigant. The research question in the present study was to assess “Is there a significant difference in reducing microbial load comparing sodium hypochlorite (NaOCl) and herbal agents.” Electronic databases (PubMed, Scopus, and Web of Science) were searched from their start dates to November 2020 using strict inclusion and exclusion criteria and reviewed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Only in vitro studies comparing herbal agents with NaOCl regarding antimicrobial efficiency were included. Two reviewers independently assessed the included article. 825 articles were obtained from an electronic database. Twenty papers were included for review of the full text. Eleven papers were excluded because they did not meet the inclusion criteria. Finally, nine articles were included in the systematic review. The present systematic review was at the in vitro level; therefore, the result cannot translate the exact clinical conditions. This systematic review concludes that herbal agents cannot be used as a main irrigant for canal disinfection.

A Comparative Evaluation of Smear Layer Removal Using Erbium:YAG Laser-Activated Irrigation, Sonic Irrigation, and Manual Dynamic Irrigation: A Scanning Electron Microscope Study

Introduction: The conventional chemomechanical procedures are ineffective in complete disinfection of the pulp space due to the complexities of the root canal architecture. The present study aims to compare the efficacy of erbium: YAG laser-activated irrigation, sonic irrigation, and manual dynamic irrigation in the removal of the smear layer through a scanning electron microscope study. Methods: Fifty extracted single rooted mandibular premolars with single canal were used and instrumented until F3 ProTaper rotary file reached the working length. Upon the completion of the canal preparation, each specimen was irrigated with 3 mL of 4% NaOCl for 3 minutes, 3 mL saline for 1 minute and 3 mL of 17% EDTA for 3 minutes. The teeth were assigned to three experimental groups (n=15 each): manual dynamic irrigation, sonic irrigation (EndoActivator), and Er:YAG laser using an X pulse tip. Root canals were sectioned longitudinally and the smear layer at the apical, middle and coronal third was examined under a scanning electron microscope. Smear layer scores were analyzed by Kruskal-Wallis and Mann-Whitney U tests at P = 0.05. Results: The Er:YAG laser group showed significantly lower smear layer scores in the apical third as compared to all other groups. EndoActivator resulted in better cleaning efficacy at the apical area compared to manual dynamic agitation. Conclusion: This study showed results in favor of Er:YAG with an X-pulse tip followed by EndoActivator activation.

Effect of Apical Third Enlargement to Different Preparation Sizes and Tapers on Postoperative Pain and Outcome of Primary Endodontic Treatment: A Prospective Randomized Clinical Trial

INTRODUCTION

The purpose of this study was to evaluate the effect of apical preparation size and taper on postoperative pain and healing after primary endodontic treatment.

METHODS

One hundred and twenty patients with asymptomatic mandibular first molars with radiographic evidence of periapical pathology and with a periapical index (PAI) score ≥3 were randomly assigned to 2 groups, group 1 and 2, based on apical enlargement to 2 and 3 sizes larger than the initial apical binding file (IABF), respectively. Each group was further divided into subgroups A and B depending on the apical enlargement taper of 4% and 6%, respectively. Endodontic treatment was performed, and the final apical enlargement in all the groups was performed as follows: group 1A, 2 sizes larger than the IABF with a 4% taper; group 1B, 2 sizes larger than the IABF with a 6% taper; group 2A, 3 sizes larger than the IABF with a 4% taper; and group 2B, 3 sizes larger than the IABF with a 6% taper. Postoperative pain was assessed at 6, 12, 24, 48, and 72 hours. Clinical evaluation and the change in the PAI score on radiographs were assessed at the 3-, 6-, and 12-month follow-ups.

RESULTS

No significant difference in postoperative pain was found. The success rate was lowest (57.1%) in group 1 subgroup A as evidenced by the significant change in the PAI score between group 1 subgroup A and the rest of the groups at the 6- and 12-month follow-ups.

CONCLUSIONS

Apical preparation to 2 sizes larger than the IABF with a 4% taper is insufficient and results in significantly lower success rates compared with larger preparation sizes and tapers.

Comparative evaluation of apical extrusion of intracanal bacteria using ProTaper Next, Mtwo, and ProTaper rotary systems: An in vitro study

Aim:

The aim of this study was to evaluate the number of intracanal bacteria extruded apically after instrumentation with three different nickel–titanium rotary instruments.

Materials and Methodology:

Forty freshly extracted mandibular premolars were selected, access cavities were prepared, and the teeth were mounted in the bacterial collection apparatus. Root canals were contaminated with a suspension of Enterococcus faecalis and incubated for 24 h at 37°C. The contaminated teeth were divided into four groups of 10 teeth each according to the rotary system used for instrumentation: Group 1: ProTaper universal files, Group 2: MTwo files, Group 3: ProTaper Next files, and Group 4: Control group (no instrumentation). Bacteria extruded after preparations were collected into vials. The number of colony-forming units (CFUs) was determined for each sample.

Statistical Analysis:

The data obtained were analyzed using the one-way analysis of variance followed by post hoc Tukey’s test with a P = 0.05 as the level for statistical significance.

Results:

The results suggested a statistically significant difference in the number of CFUs between four experimental groups (P < 0.001).

Conclusion:

Least amount of bacterial extrusion was seen in ProTaper Next Group while more bacterial extrusion was seen in MTwo Group.

Effect of preoperative oral administration of steroids in comparison to an anti-inflammatory drug on postoperative pain following single-visit root canal treatment - a double-blind, randomized clinical trial

AIM

This randomized, double-blinded, clinical trial evaluated the effect of oral premedication of piroxicam, prednisolone, dexamethasone or placebo on postoperative pain after single-visit root canal treatment in teeth with symptomatic irreversible pulpitis and symptomatic apical periodontitis.

METHODOLOGY

The trial is reported according to the Preferred Reporting Items for RAndomized Trials in Endodontics (PRIRATE) 2020 guidelines. The protocol was registered at the clinical trial registry (India) (CTRI/2019/06/019818). In total, 160 patients, assigned to four groups, received orally either 20 mg piroxicam, 20 mg prednisolone, 4 mg dexamethasone or a placebo 60 min before root canal treatment. Patients recorded their postoperative pain intensity at 6, 12, 24, 48 and 72 h using a 10-cm visual analogue scale. Intergroup comparison was performed using Kruskal-Wallis tests with post hoc analysis using Dunns test. Incidence of pain was analysed using chi-square tests. A P value < 0.05 was considered to be statistically significant. Binary logistic regression was used to determine the odds of postoperative pain, with incidence of pain as the dependent variable and intervention groups, gender, age and type of tooth as independent variables.

RESULTS

In total, 156 patients were analysed in the trial, since four patients dropped out during follow-up. All drugs were associated with a significantly lower incidence of postoperative pain compared to the placebo at 6 h (P = 0.009), 12 h (P = 0.003) and 24 h (P = 0.008). Mean intensity of pain was significantly more intense at 6, 12 and 24 h with the use of placebo in comparison to the other three intervention groups (P < 0.05). Intensity of pain was not significantly different between the premedications used (P > 0.05). One patient in the piroxicam group reported gastritis, whereas no adverse effects were recorded in other groups.

CONCLUSION

Preoperative oral administration of a single dose of 4 mg dexamethasone, 20 mg piroxicam or 20 mg prednisolone reduced the incidence and severity of postoperative pain following single-visit root canal treatment compared to a placebo in patients with symptomatic irreversible pulpitis and symptomatic apical periodontitis up to 24 h. The odds of postoperative pain at 24 h for patients premedicated with 4 mg dexamethasone or 20 mg piroxicam or 20 mg prednisolone were 5.3 times, 3.4 times and 2.5 times less compared to the placebo, respectively.

Development of Chlorhexidine Digluconate and Lippia sidoides Essential Oil Loaded in Microemulsion for Disinfection of Dental Root Canals: Substantivity Profile and Antimicrobial Activity

The dental intracanal disinfection is crucial to achieve the success of endodontic treatment, avoiding the maintenance of endodontic infections. Chlorhexidine digluconate can act as an irrigating agent for it. However, it can cause tissue irritation in high concentrations. Therefore, combinations with other antimicrobial agents and more efficient therapeutic alternatives are studied, which make it possible to administer drugs more safely and with minimal adverse effects. Thus, the objective of this study was the development of a microemulsion containing chlorhexidine digluconate and essential oil of Lippia sidoides to be used for disinfection of dental root canals and to evaluate its profile of substantivity and antimicrobial activity. The microemulsions were obtained through phase diagrams, using the spontaneous formation method. We completed a physical-chemical characterization and evaluate the stability of the microemulsions, in addition to the substantivity profile in a bovine root dentin model, and in vitro antibacterial effect on Enterococcus faecalis. A method for quantifying chlorhexidine was developed using UV-Vis spectroscopy. The microemulsions showed acid pH, conductivity above 1.3 μScm^-1, and dispersion index similar to water. The microemulsions showed antimicrobial inhibition halos similar to the commercial gel conventionally used, but with four times more substantivity to dentinal tissues. Microemulsions were obtained as a therapeutic alternative to formulations available on the market, presenting themselves as a system with great potential for the administration of drugs for disinfection of root canals.

Effect of a Modified Irrigation Protocol on the Cleanliness of Moderately Curved Canals

Objectives  This study tested the hypothesis that modifying the sequence of sodium hypochlorite (NaOCl)/ethylene diamine tetra-acetic acid (EDTA) irrigation during root canal shaping would improve apical cleanliness in moderately curved canals.

Materials and Methods  Forty-five root canals were prepared using Protaper Gold with three irrigation protocols. Standard irrigation (SI) used 0.5 mL 3% NaOCl between each instrument, followed by 5 mL 17% EDTA manually agitated for 30 seconds. Reverse irrigation (RI) used 0.5 mL of 17% EDTA between each instrument, then 5 mL of 3% NaOCl, manually agitated for 30 seconds. Reverse irrigation plus (RI+) was similar to RI, except NaOCl (5 mL), used as a final rinse, was allowed to interact for 3 minutes with dentin before manual agitation (30 seconds).

Root canal cleanliness was evaluated under the scanning electron microscope (SEM) (Hulsmann score); the chemical composition of dentin after irrigation was analyzed by energy dispersive X-ray (EDX).

Statistical Analysis  Results were compared using Kruskal–Wallis ANOVA by ranks and Wilcoxon matched paired posthoc tests. A Chi-square test assessed whether the best cleanliness would demonstrate a significant association with one irrigation protocol; odds ratio calculation was performed using score “1” versus score “2 or more” (2+) ( p < 0.05).

Results  In the apical region, cleanliness was better in RI+ than SI and both significantly better than RI. Odd ratios indicate that the cleanliness in RI+ was significantly better than RI and SI groups ( p < 0.000 and 0.003, respectively). Independently of the irrigation protocol, EDX analyses showed no chemical alteration of root dentin.

Conclusions  Using 17% EDTA during shaping, followed by 3% NaOCl rinse for 3 minutes, improved apical cleanliness without inducing erosion of dentin.

Influence of endodontic cavity access on curved root canal preparation with ProDesign Logic rotary instruments

OBJECTIVE

This study evaluates whether endodontic cavity access into molars influences the chemomechanical preparation of curved root canals.

MATERIALS AND METHODS

Twenty mesiobuccal canals of maxillary molars were randomly divided into two experimental groups (n = 10), according to the type of endodontic access analyzed (conventional and minimally invasive). The preparations were made by a single operator, and the canals, after access, were prepared with Logic system (0.25, 0.04 taper) along the working length. Samples were scanned before and after canal preparation (SMX-90CT Plus (Shimadzu® microtomograph operated with 70 kV, 100 uA, FOV (XY) 13.3 mm, FOV (Z) 7.0 mm, and voxel size 0.013 mm/Pix)) to match canal volumes. Images were analyzed to evaluate surface areas, transport, and centralization at 3 mm from the canal entrance and 3 mm from the apex (OnDemand3D^TM Dental software). Student's t test with a significance level of 5% was used for the statistical analysis.

RESULTS

Regardless of the position of the analyzed canals, there was no difference in the prepared area regarding the transport and centralization of the endodontic instrument between the two types of cavity accesses performed.

CONCLUSIONS

The conventional and minimally invasive access did not influence the action of the 0.25 and 0.04 taper instrument during the curved root canal preparation.

CLINICAL RELEVANCE

The type of endodontic access did not influence the action of the rotary instrument during the curved root canal preparation.

Apical Transportation of Mesiobuccal Canals of Maxillary Molars Following Root Canal Preparation with Two Rotary Systems and Hand Files: A Cone-Beam Computed Tomographic Assessment

Objectives:

This study aimed to compare the transportation of the mesiobuccal canal of maxillary molars following root canal preparation with HyFlex CM (HCM) and Edge Taper Platinum (ETP) rotary systems and stainless steel (SS) hand files using cone-beam computed tomography (CBCT).

Materials and Methods:

This in-vitro study was performed on 48 maxillary molars in three groups of 16. The teeth were mounted in acrylic blocks, and root canals were prepared using HCM in group 1 (up to #30/0.06), ETP in group 2 (up to F3/0.06), and SS hand files in group 3 (up to #30). CBCT scans were taken before and after root canal preparation. The amount of canal transportation was measured at 0, 3, 6, and 9mm from the apex. Data were analyzed using Kruskal-Wallis and Mann-Whitney tests.

Results:

The difference in canal transportation at 0 and 6mm from the apex was significant between the HCM and ETP groups (P=0.031 and 0.023) but none of the systems showed any significant difference with hand files at 0-and 6-mm levels (P=0.10, 0.56, 0.22, and 0.50), respectively. At 3mm from the apex, no significant difference was noted among the groups (P=0.30). At the 9-mm level, the amount of canal transportation was not significantly different between HCM and ETP (P=0.83) but they showed significant differences with hand files (P<0.001).

Conclusion:

ETP and HCM caused less canal transportation at the curvature of the mesiobuccal canal of maxillary molars compared to hand files. ETP showed superior efficacy in root canal preparation compared to HCM.

Influence of Apical Preparation Size on Effective Conventional Irrigation in the Apical Third: A Scanning Electron Microscopic Study

Objective

This study aimed to investigate the relationship between final apical preparation size and smear layer removal in the apical third using conventional irrigation in mandibular bicuspids.

Methods

A total of 66 extracted human mandibular bicuspids with comparable root canal morphology were equally divided into five experimental groups and a control group (n=11). Based on their experimental group, samples were instrumented up to size 25, 30, 35, 40, or 45 with 0.04 taper using 2.5% sodium hypochlorite (NaOCl) as the irrigant. Final irrigation was performed with 17% EDTA followed by 2.5% NaOCl. The control group was instrumented up to size 45/.04, and was irrigated with distilled water. Samples were sectioned buc-colingually, and they were qualitatively evaluated under scanning electron microscope for efficacy in smear layer removal. The Kruskal-Wallis and Mann-Whitney U tests were employed for statistical analysis.

Results

Statistical analysis revealed comparable removal of smear layer in the coronal and middle thirds of all experimental samples regardless of grouping. When using file size larger than 35, removal of smear layer in the apical third significantly improved (p<0.05). No significant difference was observed between 40/.04 and 45/.04.

Conclusion

Under the conditions of this study, using conventional irrigation, apical enlargement more than size 35/.04 is essential to enhance removal of smear layer at the apical third.

Cleaning effectiveness of a nickel-titanium ultrasonic tip in ultrasonically activated irrigation: a SEM study

In endodontic treatment, regardless of the instrumentation technique, the presence of a smear layer covering contaminated dentin walls is always a concern. Thus, irrigation plays an essential role in reducing bacterial load. To enhance irrigation effectiveness, different ultrasonic activation methods and the use of different tips have been studied. This study assessed the cleaning capacity of the novel NiTi ultrasonic tip for smear layer removal using ultrasonically activated irrigation (UAI) with passive or continuous ultrasonic irrigation (PUI or CUI, respectively), compared with conventional irrigation. Forty-five single-rooted human mandibular premolars were decoronated to a standardized length of 16 mm. Instrumentation was performed using the Genius system up to size 50.04 and irrigated with 3% NaOCl. The specimens were divided into three groups (n = 15) according to the final irrigation activation technique: conventional irrigation (CI), as control group; PUI; and CUI, following the manufacturer's protocol. The samples were longitudinally cleaved and analyzed under a scanning electron microscope for smear layer removal according to a cleanliness score for the cervical, middle, and apical thirds. Data were evaluated by means of the Kruskal-Wallis and Tukey's tests, with a 5% level of significance. UAI enhanced cleaning compared to conventional irrigation, mainly at the apical third. CUI showed the best results, with statistically significant lower scores than PUI and CI (p < 0.05). Final irrigant activation with the NiTi tip showed better cleaning capacity than conventional irrigation. In addition, CUI resulted in better smear layer removal than PUI.

Evaluation of SmearOFF, maleic acid and two EDTA preparations in smear layer removal from root canal dentin

Objectives: To evaluate SmearOFF, 7% maleic acid (MA) and two different preparations of ethylenediaminetetraacetic acid (EDTA) in smear layer removal.Materials and methods: Fifty single-rooted teeth were separated into five groups, instrumented and irrigated as follows: (1) SmearOFF, (2) 7% MA, (3) 18% EDTA (pH 11.4), (4) 17% EDTA (pH 8.5) and (5) 0.9% saline. Teeth samples were blinded and examined by scanning electron microscopy with Image J software.Results: Eighteen percent EDTA was less efficient when compared to SmearOFF and MA at all thirds of the root canal system. There was no difference between SmearOFF and MA in the coronal and middle thirds. In the apical third, MA removed more smear layer. Seventeen percent EDTA was as efficient as SmearOFF and MA in coronal and middle third but not in the apical third. Eighteen percent EDTA removed smear layer less efficiently in the coronal and middle thirds than 17% EDTA; in the apical third, there was no difference observed. In the saline group, all specimens were heavily smeared. There was no significant difference between 18% EDTA and saline at all canal thirds.Conclusions: SmearOFF and 17% EDTA (pH 8.5) had better smear layer removal capability in the coronal and middle thirds of the root canal system. In the apical third, 7% MA was superior. 18% EDTA (pH 11.4) and saline had poor smear layer removal ability.

Effectiveness of irrigation strategies on the removal of the smear layer from root canal dentin

The aim of this study was to evaluate the removal of the smear layer by some commonly used (needle-and-syringe irrigation, sonic activation, ultrasonically activated irrigation) and new root canal irrigation strategies (negative pressure irrigation and polymer rotary file) using a novel approach by comparing pre- and post-experimental images. Prepared root canals (n = 50) were subjected to a split tooth model and divided into 5 groups (n = 10): (1) needle-and-syringe irrigation (control); (2) sonic activation (SA); (3) negative pressure irrigation with continuous warm activated irrigation and evacuation (CWA); (4) polymer finishing file (FF); (5) ultrasonically activated irrigation (UAI). Smear layer scores and percentage of open dentinal tubules (%ODT) were evaluated by 2 examiners before and after irrigation procedures, from the middle and apical thirds of the root canal, on scanning electron microscopic images. Data were analysed using Kruskal-Wallis and post hoc tests at P = 0.05. Needle-and-syringe irrigation (control) showed no significant difference (both smear score and %ODT) compared to the pre-experimental value (P > 0.05). All other groups showed lower smear scores and higher %ODT, compared to the control (P < 0.05). The lowest smear score and highest %ODT were observed in the CWA group, which was significantly different from all other groups (P < 0.05). SA group showed significantly higher smear scores and lower %ODT than FF or UAI (P < 0.05). CWA showed superior removal of smear layer in the middle and apical thirds of the root canal compared to the other irrigation strategies.

Does adding an instrument after root preparation with Reciproc® R25 increase bacterial reduction?

Aim

The aim of this study was to compare the bacterial reduction achieved with reciprocating instruments such as Reciproc^® R25 (VDW GMBH, Munich, Germany) and Reciproc^® R25 combined with rotary file Mtwo 40.04 (VDW GMBH) during root canal preparation.

Materials and Methods

Fifty mesiobuccal root canals of maxillary molars were contaminated with Enterococcus faecalis broth culture and then an initial bacterial sample was collected from the root canal with paper cones and plated on brain-heart infusion agar. The root canals were divided into four groups as follows: Reciproc^® R25 (n = 20) and Reciproc^® R25 combined with Mtwo 40.04 instrument (n = 20). The negative controls consisted of five uncontaminated root canals and the positive control consisted of five contaminated roots that were not subjected to any decontamination procedure. Irrigation was performed using sodium chloride. After instrumentation, samples were collected with paper cones and the rate of bacterial reduction was calculated. Microbiological testing (colony-forming units [CFUs]) was performed to quantify the decontamination obtained by the proposed protocols. Statistical analysis was performed by paired t-test and analysis of variance test.

Results

Both techniques significantly reduced the number of bacteria in the root canal (P < 0.05), with no significant difference among them (P > 0.05).

Conclusion

The addition of the instrument Mtwo 40.04 after the root preparation with the instrument R25 does not improve its decontamination capability.

Impact of Minimal Root Canal Taper on the Fracture Resistance of Endodontically Treated Bicuspids

Objective:

Minimal invasive endodontics preserve coronal and radicular tooth structure to increase the fracture resistance of teeth. The aim of this study was to assess the influence of final preparation taper on the fracture resistance of maxillary premolars.

Materials and Methods:

Sixty maxillary premolars were selected and divided into 2 groups: 30 were shaped with a final apical diameter 30 and a 4% taper and 30 with 6% taper using iRaCe^® instrument (FKG dentaire, Switzerland). All root canals were irrigated with sodium hypochlorite and final rinse with ethylenediaminetetraacetic acid. All canals were filled with gutta-percha single-cone filling technique and AHPlus^® sealer (Dentsply- Maillefer, Baillagues, Switzerland) and access cavity restored with resin composite. Roots were wax coated, placed in an acrylic mold and loaded to compressive strength fracture in a mechanical material testing machine recording the maximum load at fracture and fracture pattern (favorable/restorable or unfavorable/unrestorable). Fracture loads were compared statistically, and data examined with Student t-test with a level of significance set at P ≤ 0.05.

Results:

No statistically significant difference was registered between the 4% taper of preparation (270.47 ± 90.9 N) and 6% taper of preparation (244.73 ± 120.3 N) regarding the fracture resistance of the endodontically treated premolars tested (P = 0.541), while more favorable restorable fractures were registered in the 4% taper group.

Conclusions:

Continuous 4% preparation taper did not enhance the fracture resistance of endodontically treated maxillary premolars when compared to a 6% taper root canal preparation. More fractures were registered in the 4% taper group.

Influence of size and insertion depth of irrigation needle on debris extrusion and sealer penetration

Objectives

To determine the effect of size and insertion depth of irrigation needle on the amount of apical extruded debris and the amount of penetration depth of sealer using a confocal laser scanning microscope (CLSM).

Materials and Methods

Twenty maxillary premolars were assigned to 2 groups (n = 10), according to the size of needle tip, 28 G or 30 G. Buccal roots of samples were irrigated with respective needle type inserted 1 mm short of the working length (WL), while palatal roots were irrigated with respective needle type inserted 3 mm short of the WL. Prepared teeth were removed from the pre-weighed Eppendorf tubes. Canals were filled with F3 gutta-percha cone and rhodamine B dye-labeled AH 26 sealer. Teeth were transversally sectioned at 1 and 3 mm levels from the apex and observed under a CLSM. Eppendorf tubes were incubated to evaporate the irrigant and were weighed again. The difference between pre- and post-weights was calculated, and statistical evaluation was performed.

Results

Inserting needles closer to the apex and using needles with wider diameters were associated with significantly more debris extrusion (p < 0.05). The position of needles and level of sections had statistically significant effects on sealer penetration depth (p < 0.05 for both).

Conclusions

Following preparation, inserting narrower needles compatible with the final apical diameter of the prepared root canal at 3 mm short of WL during final irrigation might prevent debris extrusion and improve sealer penetration in the apical third.

Effectiveness of supplementary irrigant agitation with the Finisher GF Brush on the debridement of oval root canals instrumented with the Gentlefile or nickel titanium rotary instruments

AIM

To examine the efficacy of a novel supplementary irrigant agitating brush (Finisher GF Brush, MedicNRG, Kibbutz Afikim, Israel) on the debridement of root canals prepared with a novel stainless steel rotary instrumentation system (Gentlefile; MedicNRG), or nickel titanium rotary instruments in oval root canals.

METHODOLOGY

Mandibular premolars (n = 72) were selected and divided randomly into three experimental groups (n = 24) after microCT scanning: group 1, canal preparation to rotary NiTi size 20, .04 taper (R20); group 2, rotary NiTi to size 25, .04 taper (R25) and group 3, Gentlefile size 23, .04 taper (GF). Specimens were subdivided into two subgroups: subgroup A, syringe-and-needle irrigation (SNI); subgroup B, Finisher GF Brush (GB). Ten untreated canals served as controls. Specimens were processed for histological evaluation, and the remaining pulp tissue (RPT) was measured. Data were analysed using Mann-Whitney and Kruskal-Wallis tests (P = 0.05).

RESULTS

All experimental groups had significantly less RPT than the control (P < 0.05). Group 3B (GF-GB) had significantly less RPT than groups 1B (R20-GB) and 2B (R25-GF; P < 0.05). When irrigated with SNI, there was no significant difference in the RPT between the three groups (P > 0.05). When instrumented with R20, there was no significant difference between SNI and GF (P < 0.05) whilst GB had significantly less RPT than SNI for R25 (P < 0.05).

CONCLUSIONS

Supplementary irrigant agitation with the Finisher GF Brush improved the debridement of canals prepared with Gentlefile and size 25, .04 taper rotary NiTi. Root canal debridement did not significantly differ between the instruments when syringe irrigation was used.

Smear layer removal evaluation of different protocol of Bio Race file and XP- endo Finisher file in corporation with EDTA 17% and NaOCl

Background

The aim of the present study was to compare the amount of the smear layer remaining in prepared root canals with different protocols of Bio RaCe files and XP-endo Finisher file (XPF) in association with 17% EDTA and sodium hypochlorite solution.

Material and Methods

A total of 68 extracted single-rooted teeth were randomly divided into 4 experimental groups (n=14) and two control groups (n=6). The root canals were prepared with Bio RaCe files (FKG Dentaire, Switzerland) using the crown-down technique based on manufacturer’s instructions and irrigated according to the following irrigation techniques: Group 1: XPF with 2 mL of 2.5% NaOCl for 1 minute. Group 2:, XPF with 1 mL of 17% EDTA for one minute. Group 3: XPF was used for 1 minute in association with normal saline solution. Group 4: XP-endo Finisher file for 30 seconds in association with 2.5% NaOCl and 17% EDTA for 30 seconds. The negative control group: NaOCl (2.5%) was used during root canal preparation, followed by irrigation with 17% EDTA at the end of root canal preparation. The positive control group: Normal saline solution was used for irrigation during root canal preparation. In all the groups, during preparation of the root canals with Bio RaCe file, 20 mL of 2.5% NaOCl was used for root canal irrigation and at the end of the procedural steps 20 mL of normal saline solution was used as a final irrigant. The samples were analyzed under SEM at ×1000‒2000 magnification and evaluated using Torabinejad scoring system. Data were analyzed with non-parametric Kruskal-Wallis test and post hoc Mann-Whitney U test, using SPSS. Statistical significant was defined at P<0.05.

Results

The results of the study showed the least amount of the smear layer at coronal, middle and apical thirds of the root canals in groups 2, which was not significantly different from the negative control group (P<0.5).

Conclusions

Under the limitations of the present study, use of a combination of NaOCl and EDTA in association with XPF exhibited the best efficacy for the removal of the smear layer.

Key words:Smear layer, XP-endo Finisher file, EDTA, Sodium hypochlorite.

Canal Transportation and Centering Ability of ProTaper and SafeSider in Preparation of Curved Root Canals: A CBCT Evaluation

INTRODUCTION

Maintaining the original central canal path is an important parameter in efficient root canal preparation. Instruments causing minimal changes in original canal path are preferred for this purpose. This study sought to compare canal transportation and centering ability of ProTaper and SafeSider instruments in curved mesiobuccal root canals of mandibular first molars using cone beam computed tomography (CBCT).

METHODS AND MATERIALS

In this experimental study, 30 mesiobuccal root canals of extracted human mandibular first molars with 20° to 40° curvature were randomly divided into two groups (n=15). After mounting in putty, preoperative CBCT scans were obtained of teeth. Root canals in group A were shaped using S1, S2, F1 and F2 of ProTaper system. Root canals in group B were instrumented to size 25 using SafeSider system according to the manufacturers' instructions. Postoperative CBCT scans were then obtained. The distance between the external root surface and internal canal wall was measured at the mesial and distal at 1, 3 and 7 mm from the apex. The values measured on primary and secondary CBCT scans were compared to assess possible changes in original central canal path and canal transportation. Data were compared using the t-test and repeated measure ANOVA.

RESULTS

ProTaper and SafeSider were significantly different in terms of canal transportation and centering ability, and ProTaper was significantly superior to SafeSider in this respect (P<0.001).

CONCLUSION

ProTaper (in contrast to SafeSider) is well capable of maintaining the original central canal path with the least amount of transportation.

Investigations into in situ Enterococcus faecalis biofilm removal by passive and active sodium hypochlorite irrigation delivered into the lateral canal of a simulated root canal model

AIM

To investigate in situ Enterococcus faecalis biofilm removal from the lateral canal of a simulated root canal system using passive or active irrigation protocols.

METHODOLOGY

Root canal models (n = 43) were manufactured from transparent resin materials using 3D printing. Each canal was created with an 18 mm length, apical size 30, a .06 taper and a lateral canal of 3 mm length, with 0.3 mm diameter. Biofilms were grown in the lateral canal and apical 3 mm of the main canal for 10 days. Three models from each group were examined for residual biofilm using SEM. The other forty models were divided into four groups (n = 10). The models were observed under a fluorescence microscope. Following 60 s of 9 mL of 2.5% NaOCl irrigation using syringe and needle, the irrigant was either left stagnant in the canal or activated using gutta-percha, sonic or ultrasonic methods for 30 s. Images were then captured every second using an external camera. The residual biofilm percentages were measured using image analysis software. The data were analysed using generalized linear mixed models. A significance level of 0.05 was used throughout.

RESULTS

The greatest level of biofilm removal was obtained with ultrasonic agitation (66.76%) followed by sonic (45.49%), manual agitation (43.97%) and passive irrigation groups (38.67%), respectively. The differences were significant between the residual biofilm in the passive irrigation and both sonic and ultrasonic groups (P = 0.001).

CONCLUSION

Agitation resulted in better penetration of 2.5% NaOCl into the lateral canal of an artificial root canal model. Ultrasonic agitation of NaOCl improved the removal of biofilm.

Effects of EDTA gel and chlorhexidine gel on root dentin permeability

The aim of this study was to evaluate the effect of 24% ethylenediaminetetraacetic acid (EDTA) gel and 2% chlorhexidine gel (CHX) in dentin permeability and smear layer removal from root canals instrumented with NiTi rotary system using histochemical staining and scanning electron microscopy (SEM) analysis. Overall, 43 premolars were classified into two experimental groups, EDTA (n = 20) and CHX (n = 20), and a negative control (NC) (n = 3). All specimens were instrumented and the irrigant solutions were used after each file change. The EDTA group received a final rinse with 5-ml 1% NaOCl followed by a 5-ml 0.9% saline solution; the CHX group received a final rinse with 10-ml 0.9% saline solution; and the negative control group received a final rinse with only 0.9% saline solution. Fifteen teeth from each group were prepared for histochemical staining and evaluation of dentin permeability using the image-scanning software Axion Vision (v.4.8.2). Five remaining teeth were prepared for analysis using SEM for morphological analysis. The study found that 24% EDTA gel increased the permeability of dentin in all thirds evaluated and also demonstrated an increased cleaning ability, with dentinal walls free of smear layer and open dentinal tubules, as compared to 2% CHX gel. It was concluded that EDTA was efficient in cleaning the dentinal tubules and increased dentin permeability.

Effect of 5% Chlorine Dioxide Irrigant on Micro Push Out Bond Strength of Resin Sealer to Radicular Dentin: An In Vitro Study

INTRODUCTION

Chlorine dioxide (ClO₂) has been recently investigated as a possible root canal irrigant due to its broad spectrum of antimicrobial action, tissue dissolution and smear layer removal properties. Literature is scarce on the effect of chlorine dioxide irrigation on the resin sealer dentin bond strength.

AIM

To compare 5% chlorine dioxide (ClO₂) with or without Ethylene Diamine Tetra Acetic acid (EDTA) with 3% Sodium hypochlorite (NaOCl) and EDTA combination as endodontic irrigants on the adhesion of AH Plus sealer to radicular dentin using micro- Push out Bond Strength (µPBS) test.

MATERIALS AND METHODS

Forty freshly extracted central incisors were decoronated and randomly divided into four groups based on the different irrigation regimes followed during irrigation: Group I - 3% NaOCl + 17% EDTA, Group II - 5% ClO₂ + 17% EDTA, Group III - 5% ClO₂ and Group IV - Saline, and canal enlarged till Protaper F3. All the samples were obturated with F3 gutta-percha cones using AH Plus sealer and sectioned perpendicular to long axis to obtain 1mm thick slices from the middle and coronal portions for µPBS measurement in universal testing machine followed by assessment of failure pattern under stereomicroscope. Data was analysed using One-way analysis of variance (ANOVA), Bonferroni and t-test.

RESULTS

Bond strength values were in the following order: Group I>Group II>Group III>Group IV, with no statistically significant difference amongst experimental groups on intergroup comparison, except with saline. The µPBS values were more in coronal third than middle third in all specimens, with no statistical significant difference. Mode of failure showed mixed patterns in all experimental groups except saline.

CONCLUSION

In the present study, the bond strength values of ClO₂ were comparable with conventional NaOCl and EDTA combination and hence, ClO₂ can be considered as an effective alternative endodontic irrigant.