Iranian Endodontic Journal
Volume:16 Issue: 2, Spring 2021

Due to the complex micro-anatomy of the root canal system, mechanical instrumentation leaves significant portions of the root canal walls untouched; therefore, complete elimination of bacteria from the root canal by cleaning with instrumentation alone is unlikely. It has long been postulated but not demonstrated, that any pulp tissue left in the root canals can serve as bacterial/fungal/viral (microorganism nutrients) nutrients. Furthermore, tissue remnants also impede the antimicrobial effects of root canal irrigants and medicaments and prevent intimate adaptation of the root canal filling to the dentin. Therefore, specific irrigation/disinfection procedures are necessary to remove tissue from the root canals and to kill microorganisms, respectively. The purpose of this paper was to review different aspects of a promising root canal irrigant; QMix. This is a relatively new root canal irrigant composed of traditional materials like chlorhexidine (CHX), ethylele diamine tetraacetic acid (EDTA), saline and a detergent. QMix is antibacterial, antifungal and has antibiofilm activities, it displays substantivity, smear layer removing ability; moreover, its effect on dentin and retention of fiber posts etc. has been reviewed. There have been strong reports that show the chemical design of QMix prevents precipitation of CHX when together with EDTA and mixing with sodium hypochlorite does not produce the orange-brown precipitate. Furthermore, the smear layer removal ability of QMix is comparable to that of 17% EDTA and the antibacterial activity of QMix was greater than 1% and 2% sodium hypochlorite (NaOCl) and 2% CHX.

 This study aims to evaluate the cyclic and torsional fatigue resistance of seven rotary systems.

 Methods and Materials: 

A total of 140 instruments were tested, 20 of each system including Genius (GN) 25/0.04, TruShape (TS) 25/0.06, Logic (LOG) 25/0.06 taper, Vortex Blue (VB) 25/0.06, ProTaper Gold (PTG) 25/0.08, Hyflex CM (HCM) 25/0.06 and Hyflex EDM (EDM) 25/0.08 taper. Cyclic fatigue resistance testing was performed using an artificial stainless steel canal with a curvature (60° angle and 5-mm radius) located at 5 mm from the tip. The files (n=10) rotated until fracture, and time was recorded in seconds. The torsional test was evaluated according to ISO 3630-1. Data were analysed with one-way ANOVA and Tukey’s tests (α=5%). The fractured surface of the instruments were assessed using scanning electron microscopy to confirm the type of fracture. 

 The cyclic fatigue resistance value of EDM was significantly higher than those of all tested instruments (P<0.05). LOG showed a higher cyclic fatigue resistance than GN or TS (P<0.05). There was no difference among the other groups (P>0.05). The torsional test showed that PTG 25/0.08 had the highest torsional strength value of all instruments tested followed by VB and EDM (P<0.05). The LOG showed significant difference only with GN (P<0.05). No difference was found among the other groups (P>0.05). In relation to angular deflection, the GN; TS; HCM, and EDM showed significantly higher values until fracture than the other groups (P<0.05). No difference was found among PTG, LOG, and VB (P>0.05). 

 Our in vitro study EDM group had the highest cyclic fatigue resistance among all the tested instruments. For the torsional test, the PTG showed highest torsional strength and lowest angular deflection values.

 The purpose of this study was to determine the volume of dental tissue removed during endodontic access preparation with cone-beam computed tomography (CBCT) comparing two different software. 

CBCT images of 20 teeth were obtained before and after endodontic access performed with spherical and conical diamond burs. The images were taken with i-CAT Precise system with 0.25 mm voxel size. Digital Imaging and Communications in Medicine (DICOM) images were loaded on two different software programs (Materialise® and InVersalius®), and a 3D reconstruction of the CBCT images was performed on both programs. The baseline volume (BV), and the final volume (FV) were obtained, and the lost tissue volume (LV) was calculated using the formula: LV=BV-FV. The t-test was used to compare initial and final volumes and also to compare the two programs, using a significance level of 5%. 

 The volumetric data calculated for the MaterialiseÒ and the InVesaliusÒ programs were, respectively: BV-mean of 441.79±85.08 mm3 and 442.01±84.83 mm3; FV-mean of 426.75±83.88 mm3 and 426.94±83.75 mm3; LV-mean of 15.04±4.32 mm3 and 15.07±4.16 mm3. No statistically significant difference was found in the volumes calculated by either program for initial, final, or removed tissue (P>0.05). However, there was a significant difference between the BV and LV calculated on the same program (P<0.05). 

 Our in vitro study showed that CBCT was able to determine the volume of dental tissue removed in the endodontic access preparation of extracted human teeth, regardless of the software program used.

 This study evaluated the propagation of dentinal microcracks and the root canal volume increase after being prepared with two endodontic instruments: ProTaper Next (PTN) and WaveOne Gold (WOG) by micro-computed tomography analysis. 

Methods and Materials: 

We selected 48 maxillary molars randomly distributed in two groups: PTN and WOG. The samples were scanned before and after instrumentation, and then the image analysis was performed to detect the propagation of pre-existing dentinal micro-cracks and calculate the pre- and post-instrumentation volume. The statistical analysis was performed using Student’s t-test, Fisher's exact test, and ANCOVA (P<0.05). 

 Dentinal microcracks were observed in 95.8% of the samples, both PTN and WOG instruments propagated microcracks after instrumentation, but there was no significant difference between the instruments (P=0.538). In relation to the root canal volume there was no statistic difference between PTN and WOG systems for the mesiobuccal (P=0.426) and distobuccal root canals (P=0.523). 

 We can conclude that both ProTaper Next and WOG systems propagate dentinal microcracks after root canal preparation in this in vitro study, without statistical significance. The root canal volume prepared also showed no statistically significant difference between the two groups. This in vitro study requires further studies for more concrete conclusions.

 C-shaped canals and three rooted mandibular molars are challenging to treat. These anatomies are commonly found in mandibular molars, especially in the Mongoloid population. However, there is no report on these anatomies using cone-beam computed tomography on all three mandibular molars in Thais. The objectives of this study were to determine the prevalence of C-shaped canals and three-rooted mandibular molars in Thais and investigate whether there is a relationship between these morphology and gender. 

Methods and Materials: 

Three pre-calibrated observers independently determined the presence of each anatomy using a specific protocol in 753 molars from cone-beam computed tomographic images. The three observers randomly re-evaluated 20% of the samples to determine inter- and intra-observer agreement using Cohen’s Kappa statistic. The relationship of these root canal anatomy with sex was analysed by the Chi-square test. 

 The prevalence of C-shaped canals and three-rooted molars was 0.39% and 12.1%, 42.4% and 3.9%, and 16.6% and 9.1% in first, second, and third mandibular molars respectively. The inter-/intra-observer reliability of the results was extremely high. 

 This cross-sectional study showed the prevalence of C-shaped canals in mandibular second molars was relatively high and should be considered normal root canal anatomy in Thais. The prevalence of three-rooted molars was highest in first molars and frequently found in third molars. Cone-beam computed tomography was a reliable technique to determine root canal anatomy.

 Although micro-computed tomography (MCT) evaluation of the shaping ability of ProTaper Next (PTN) and Hyflex CM (HCM) files has been reported, to our knowledge, no study has assessed the performance of V-Taper 2H (VT) files. The aim of this study was to evaluate and compare the shaping ability of PTN, HCM, and VT systems in the mesial canals of mandibular molars using MCT.

 Methods and Materials: 

 Thirty extracted first and second mandibular molars were scanned using MCT and randomly assigned to HCM, PTN, and VT groups. Images obtained before and after preparation were evaluated for the increase in the root canal volume, untouched surface area, and amount of accumulated hard tissue debris. One-way analysis of variance (ANOVA) and Kruskal-Wallis test were used to compare the variables in the groups (α=5%). 

 There were no statistically significant between-group differences in the postoperative measurements (P>0.05). The canal volume increased in all three groups: PTN   (73.84%), VT (73.48%), and HCM (49.29%). The largest and smallest untouched areas were observed in the PTN (41.37%) and VT (30.85%) groups, respectively (P>0.05). The debris formed during canal preparation was 1.84%, 2.16%, and 2.42% in the VT, PTN, and HCM groups, respectively (P>0.05). 

 Based on our in vitro study, the PTN, HCM, and VT systems showed similar shaping abilities. None of the tested canals were completely free from debris, while the untouched surface area was considerably large. The VT system had the most favorable results with the smallest untouched surface area and least debris were. We would recommend further trials to endorse these findings.

 We aim to evaluate the cyclic and torsional fatigue resistance of two rotary instruments, Hyflex CM 25/0.06 (HCM) (Coletene-Whaledent, Allstetten, Switzerland) and Aurum Blue (AB) 25/0.06 (Meta-Biomed, Republic of Korea). 

Methods and Materials:

 Forty rotary instruments, HCM 25/0.06 and AB 25/0.06 (n=20 each) were used. The instruments were rotated in an artificial stainless steel canal with a 60° angle and a 5-mm radius of curvature (n=10) at body temperature (35°±1°C). The torsional test evaluated the torque and angle of rotation at failure of new instruments (n=10) in the portion 3 mm from the tip according to ISO 3630-1. The fractured surface of each fragment was observed by scanning electron microscopy. The data were analyzed using unpaired student’s t- test, and the level of significance was set at 5%. 

AB 25/0.06 had significantly greater number of cycles to failure than HCM 25/0.06 (P<0.05). The torsional test showed there were no significant differences in the torsional strength and angular rotation to fracture between the groups (P>0.05). 

 Based on this in vitro study, AB 25/0.06 instrument was more resistant to cyclic fatigue than the HCM 25/0.06 instrument, suggested that these instruments are safer than HCM 25/0.06 for the preparation of severely curved canals. However; there was no significant difference in the torsional properties of the two instruments then appear to have similar performance during constricted canal preparation.

The present case report describes an endodontic treatment of a three-rooted maxillary first molar with taurodontia and a palatal root with two separate canals. Maxillary first molar with two palatal canals is rare since extra canals are found most in the mesiobuccal root as the second mesiobuccal canal. Clinicians should have a thorough knowledge of the root canal system and internal anatomy and be alert about the possible existence of any variation in the canal morphology because it determines the successful outcome of an endodontic treatment.

External cervical resorption (ECR) is a pathology that is difficult to diagnose early, and because it is often confused with root decay, it can be treated inadequately and even result in tooth loss. Currently, treatment does not have a defined protocol, being widely varied in the literature. This article proposes that cases of ECR should be treated individually, following different criteria, based on aspects related to the patient and the tooth involved. Furthermore, this work illustrates, through a case report, how a patient can present unique characteristics that require treatment to be case-dependent and should be discussed among a multidisciplinary team.

The use of chlorhexidine gluconate (CHX) as an irrigating solution in an anesthesia cartridge is a wrong procedure commonly performed in daily clinical practice. Being an invasive procedure, it is invariably associated with complications. A 47-year-old healthy woman was injected accidentally with 2% CHX in the buccal vestibular area instead of an anesthetic solution during a root canal treatment. After the injection, the patient experienced local side effects, such as a burning sensation on the right cheek area, also a discomfort perception at the injection site and a slight inflammation with a mild extraoral redness especially on the right side cheek. The patient was prescribed with antibiotics and anti-inflammatories to reduce pain and inflammation. The patient complained of upper lip numbness by the second day of the accident. The extraoral swelling reduced gradually and the redness diminished considerably over a period of 6 days. At day 60 of follow-up, the patient recovered satisfactorily from extraoral inflammation but still presented a slight numbness of the upper lip. As a conclusion, we can claim that anesthesia cartridges with irrigant solutions should never be used to irrigate the root canals, and accidental injection of CHX should be carefully assessed by the clinician.

Profound knowledge of the internal anatomy and configuration of the teeth plays a pivotal role in the success of standard root canal treatment. The presence of unexpected extra root canals has been reported in all the teeth, making root canal treatment a challenge for every clinician. Although the maxillary second premolar is no exception to this rule, the presence of a variety of multiple canals is relatively rare. In fact, the presence of three separate root canals has been reported in only 1-6% of cases. A 33-year-old male was referred for root canal retreatment of his left maxillary second premolar. An intraoral periapical radiograph revealed previous substandard endodontic treatment. Retreatment was performed under an operating microscope, and four root canals were found, which is, in fact, very rare. This case highlights another variation in the morphology of such teeth and it does highlight the importance of using magnification, especially an operating microscope in endodontic treatment.

Crown re-attachment is the most conservative treatment that can be used to restore fractured tooth, even in an emergency situation. The re-attachment maintains original contour and incisal translucency of the tooth, and reduces the chair time and cost. In case of crown fracture with pin-point pulp exposure, irritation to the pulp should be minimised and consideration must be taken for pre-treatment pulpal status, choice of pulp capping material, choice of bonding system and treatment sequence during crown re-attachment procedures. This article reported a crown fracture case with pin-point pulp exposure that was treated using crown re-attachment with direct pulp capping. At two-year follow-up, the tooth was asymptomatic, remained functional, vital, and the appearance of restoration was acceptable with no colour change to the crown.