Iranian Endodontic Journal
Volume:15 Issue: 2, Spring 2020

Endodontic pathosis is preliminary caused by bacteria and their by-products that interact with pulpal and periradicular host tissues. The purge of the root canal system (RCS) from bacteria is a necessity for successful endodontic treatment. Different approaches have been considered to reduce the number of microorganisms and confront microbiota in the radicular area; namely chemomechanical preparation and intracanal medication. However, various studies have shown that, due to the intricate anatomy of RCS, bacteria can persist in distant areas and significantly decrease the degree of success in endodontic ministrations. Thereby, elimination of bacteria remains a challenge, specifically from the infectious root canals. In recent years, local drug delivery systems (LDDS), loaded with drugs and/or antibacterial agents, have been deliberated for the removal of microorganisms or as a medicinal adjunct to mechanical instrumentation. Owing to the resistant species and complexities in the structure of root canals, it seems that LDDS may be able to closely affect microorganisms and improve the success rate of endodontic treatment. Furthermore, they are capable of limiting drugs to RCS, and can achieve a more effective therapeutic dose/concentration in the target site. Furthermore, and due to successful outcomes, administration of LDDS has also been given great attention for regenerative purposes. Micro/nanoparticles, liposomes, nanofibers, sealers and so forth represent typical delivery systems used for endodontic treatments. This study addresses pivotal LDDS used in endodontics and their applications.

Dental problems are common in human populations. Traditional treatments are focused on managing caries, soft tissue impairments, functional defects, poor aesthetics, digestive disorders and alveolar bone resorption. During the last two decades, basic and clinical researches on adult stem cells have established a potential therapeutic concept in tissue regeneration. Among major cells responsible for tooth development, odontoblasts play a key role in the formation of organic and inorganic constituents of dental tissue. A premier stride in the development of novel stem cell-based strategies for the treatment of reversible and irreversible pulpitis is odontoblast regeneration. Among different candidate cell sources for odontoblastic regeneration, use of dental adult stem cells is a preferred option because of their great ability to differentiate into odontoblasts and also their minimally invasive isolation procedure. This review emphasizes on articles that report successful odontoblast-like differentiation of dental mesenchymal stem cells which in turn provide a background for dentin-pulp complex cell therapies, using genetic or chemical manipulation. The series of experiments both in vitro and in vivo asserted that dental mesenchymal stem cells can efficiently differentiate into functional odontoblast-like cells. However, the review shows there are drawbacks in present methods. Future research should focus on optimizing protocols on odontoblast differentiation of dental stem cells by simultaneously introducing different genes with mutual synergy, combined with chemical or recombinant protein introduction.

Photodynamic therapy (PDT) is an emerging alternative therapy to conventional endodontic treatment to optimize bacterial elimination. The aim of this study was to evaluate the in vitro antibacterial effect of PDT combined with different irrigation protocols on root canals inoculated with Enterococcus (E.) faecalis.

Ninety uni-radicular human premolars were prepared and contaminated with E. faecalis for 4 days. Teeth were randomly divided into six groups: positive control group (C+) consisted of conventional needle irrigation with 2.5% sodium hypochlorite (NaOCl); negative control group (C-) consisted of no treatment after contamination; PDT group as treated with 0.005% methylene blue and diode laser irradiation for 90 sec at wavelength of 660 nm, energy of 9 Joules, power of 100 mW; the fourth group consisted of  NaOCl+PDT, the fifth group were treated with passive ultrasonic irrigation (PUI) with NaOCl+PDT (PUI+PDT); and the final group were treated with XP Endo Finisher with NaOCl+PDT (XP Endo+PDT). The contents of the root canals were collected with sterile absorbent paper points at two times: before and 24 h after decontamination protocols. The number of colony-forming units (CFU) was determined for each root canal. ANOVA and the Tukey test were used, with significance set at 5% (P<0.05).

The inhibition percentage ranged from 10.72 (C-) to 100% (XP Endo+PDT), with CFU/mL counts differing among all protocols tested (P<0.05). The different protocols significantly influenced bacterial inhibition (P<0.05). However, the XP Endo+PDT protocol resulted in the highest inhibition percentage (100%), followed by NaOCl+PDT (65.85%).

PDT combined with different final irrigation protocols was more effective in inhibiting E. faecalis growth than photodynamic therapy alone. XP Endo was the best irrigation protocol to eradicate this microorganism.

The aim of this study was to compare the effect of sample preparation methods on push-out bond strength of mineral trioxide aggregate (MTA).

Twenty-four extracted human mandibular premolars with single root canal were selected for this in vitro study. After instrumentation, irrigation and drying of root canals, they were randomly divided into two experimental groups (n=12). Group 1: After removing the 3 mm of root ends, 2 mm thick sections were established from the remaining roots. MTA was mixed following the manufacturers’ recommendations and root sections were filled. Group 2: The whole root canal was used for filling and packing of MTA and like group 1, after removing the 3 mm of root ends, root sections were provided. Push-out bond strength was measured and analyzed by the independent t-test. Level of statistical significance was set at 0.05.

The highest mean push-out bond strength was in apical section of group 2 (4.86±1.31) and the lowest value was in coronal section of group 2 (3.05±1.15). The results of the independent t-test showed a significant difference between two groups only in the apical section (P=0.02).

Based on the results of this in vitro study, the highest mean push-out bond strength was in apical section of group 2. It seems that using the whole root canal for MTA application is better for MTA in vitro analysis of bond strength to root dentin because it is more similar to the clinical conditions.

In this study, new devices were developed and evaluated for cyclic fatigue testing (CTF) of endodontic instruments in two-dimensional (2D) and three-dimensional (3D) replicas of the internal anatomy of a mesial root of a mandibular molar.

The trajectories of both curved mesial canals of the same root were outlined from computed tomographic scans and exported to a computer assisted drawing (CAD) software. In the CAD program, the canals were virtually enlarged to a size 25/0.06. The CTF devices were then prototyped in stainless steel. The 2D models represented the bucco-lingual (BL) and mesio-distal (MD) views of the canals, while the original trajectory was kept in the 3D model. Vortex Blue 25/0.06 instruments were tested for fatigue in the six canals (n=12). The number of cycles to failure (NCF) and fragment length (mm) were recorded. Data was statistically analyzed (ANOVA and post-hoc Games-Howell test) with the level of significance set at 5%.

The mean NCF was significantly different among all the canals (P<0.05). The lifespan of the files was greater in the 2D-BL models, followed by the 2D-MD and 3D. The mean fragment length was also different among the tested models (P<0.05).

The tested 2D and 3D representations of the same canal trajectory resulted in significant differences both in the amount of stress (seen from NCF) and localization of the maximum stress (seen from fragment length). Further investigations are required to better understand the effects of different 3D curvatures on the cyclic fatigue of endodontic instruments.

Bacterial leakage has considerable role in endodontic related failures. The aim of this study was to compare the bacterial leakage of bioceramic and resin based root canal sealers.

Sixty-eight maxillary central incisors were included in this experimental study and randomly allocated to four groups which obturated with GP and four different sealers (AH Plus=15, AdSeal=15, Well Root ST=15, MTA Fillapex=15) and control groups (positive =4, negative =4). A dual chamber technique was carried out using fresh human saliva and traced for 90 days. Chi-square and Long Rank test was performed for data analysis.

Bacterial leakage was observed in 33.3% of Well Root ST, 40% of AH Plus, 53.3% of AdSeal and 66.6% of MTA Fillapex group.  The difference between Well Root ST and MTA Fillapex groups was significant (P= 0.02). The mean leakage time between Well Root ST (85.6 days) and MTA Fillapex groups (71.2 days) was significant (P= 0.037).

Based on the result of this study, bacterial leakage was observed in all experimental groups.Respectively Well Root ST and MTA Fillapex groups showed the least and highest bacterial leakages.

This case report describes the use of the guided endodontics for a non-surgical endodontic retreatment of the mandibular molar. A 38-year-old female reported apical swelling and localized pain on the tooth #30, exacerbated when chewing hard food. Periapical radiographic examination showed pulp canal obliteration in the apical third associated with extensive radiolucent area. Cone-beam computed tomography (CBCT) images were requested to support the diagnosis and enable preparation of a surgical guide, used to direct access to the canals that were obliterated and incompletely filled. The follow-up at 24 months radiographically showed completely healed apical area in the involved tooth. This non-surgical technique demonstrated efficacy in case resolution.Keywords: Cone-beam Computed Tomography; Endodontic; Guided Endodontics

Dens invaginatus is an abnormal dental developmental, probably resulting of the invagination of mineralized tissues from the tooth crown surface before its calcification. The teeth that are most affected by this abnormality are the maxillary lateral incisors. This dental developmental anomaly has various types and the rarest is type III which has the worst prognosis, because of its complex anatomy. Conventional root canal therapy may not sufficiently resolve the case itself and in some circumstances the surgical intervention is also necessary. This report addresses a complex combined endodontic treatment of a type III dens invaginatus in a maxillary lateral incisor in an 18 years-old female patient, with an extensive periapical lesion affecting the buccal and palatine cortical bone, diagnosed by cone-beam computed tomography (CBCT). The case was conducted with the combination of endodontic and surgical treatment, under the use of the surgical operating microscope. The association of CBCT, visual magnification, XP-endo Finisher, bioceramic sealer, MTA Repair HP and bone graft were important to ensure predictable success.