Prasanna Neelakantan

Effect of root canal irrigation protocols on the dislocation resistance of mineral trioxide aggregate-based materials: A systematic review of laboratory studies

The aim of this systematic review was to address the question: Do different irrigating protocols have an impact on the dislocation resistance of mineral trioxide aggregate (MTA)-based materials? The review was performed using a well-defined search strategy in three databases (PubMed, Scopus, Web of Science) to include laboratory studies performed between January 1995 and May 2017, in accordance with PRISMA guidelines. Two reviewers analysed the papers, assessed the risk of bias and extracted data on teeth used, sample size, size of root canal preparation, type of MTA-based material, irrigants, canal filling method, storage method and duration, region of roots and the parameters of push-out testing (slice thickness, plunger dimensions and plunger loading direction), the main results and dislocation resistance values (in MPa). From 255 studies, 27 were included for full-text analysis. Eight papers that met the inclusion criteria were included in this review. There was a wide variation in dislocation resistance due to differences in irrigation sequence, time and concentration of irrigants, storage method and duration, and the parameters of push-out bond strength testing. A meta-analysis was not done but qualitative synthesis of the included studies was performed. No definitive conclusion could be drawn to evaluate the effect of irrigation protocols on dislocation resistance of MTA-based materials. Recommendations have been provided for standardized testing methods and reporting of future studies, so as to obtain clinically relevant information and to understand the effects of irrigating protocols on root canal sealers and their interactions with the dentine walls of root canals.

Enterococcus faecalis immunoregulates osteoclastogenesis of macrophages

Abstract Persistent apical periodontitis (PAP) is characterized by refractory inflammation and progressive bone destruction. Enterococcus faecalis infection is considered an important etiological factor for the development of PAP, although the exact mechanisms remain unknown. This study aimed at investigating the role of E. faecalis in cell proliferation, inflammatory reactions and osteoclast differentiation of macrophages using an in vitro infection model of osteoclast precursor RAW264.7 cells. A cell viability assay of cultured RAW264.7 cells exposed to live E. faecalis at a multiplicity of infection of 100 for 2 h, indicated that the infection exhibited no cytotoxic effect. Transmission electron microscopy images revealed no apoptotic changes but a rise of metabolic activity and phagocytic features in the infected RAW264.7 cells. Confocal laser scanning microscopic and flow cytometric analysis indicated that the phagocytosis of RAW264.7 cells was activated by E. faecalis infection. Furthermore, quantitative real‐time PCR assays demonstrated that the expression of inflammatory cytokines was remarkably elevated in infected RAW264.7 cells. Differentiation of infected RAW264.7 cells into osteoclasts was remarkably attenuated, and expression of osteoclast marker genes as well as fusogenic genes significantly dropped. In summary, E. faecalis appears to attenuate osteoclastic differentiation of RAW264.7 precursor cells, rather stimulates them to function as macrophages. HighlightsAn in vitro infection model of osteoclast precursors by E. faecalis was established.E. faecalis infection upregulated the inflammatory response of osteoclast precursors.E. faecalis infection attenuated RANKL‐induced osteoclastogenesis of RAW264.7 cells.

Does the Orifice-directed Dentin Conservation Access Design Debride Pulp Chamber and Mesial Root Canal Systems of Mandibular Molars Similar to a Traditional Access Design?

Introduction: Despite the increasing reports on mechanical aspects of contracted endodontic access cavities (CECs), we believe that the biological aspects (debridement) have not been adequately investigated. This study examined if 1 type of CEC (orifice‐directed dentin conservation [DDC] access) was able to debride the pulp chamber, root canals, and isthmus of mesial roots of mandibular molars similar to a traditional endodontic access cavity (TEC). Methods: Mandibular molars (N = 32) were selected and divided randomly into 2 experimental groups (n = 12) after micro–computed tomographic scanning (group 1: TEC and group 2: DDC) and histologic controls (n = 8). After instrumentation to a size 30/0.06 taper using 3% sodium hypochlorite as irrigant, specimens were processed for histologic evaluation, and the remaining pulp tissue (RPT) was measured from the pulp chamber, root canal, and isthmus at all root thirds. Data were analyzed using 1‐way analysis of variance, Kruskal‐Wallis, and appropriate post hoc tests (P = .05). Results: The RPT in the pulp chamber was significantly higher in DDC compared with TEC (P < .05). Comparing the root thirds in each group, there was no significant difference in the RPT within the root canals or the isthmus (P > .05). The RPT within the root canals and isthmus was not significantly different between the 2 access cavity designs at any root third (P > .05). Conclusions: Debridement of the pulp chamber was significantly compromised in DDC. The type of access cavity did not influence the amount of RPT in the root canals and isthmus. Highlights:For the first time, the debridement of an orifice‐directed access cavity design (truss access) was compared with a traditional access cavity.The pulp chamber was significantly cleaner in a traditional access compared with the orifice‐directed access.The root canals and isthmus showed a similar amount of remaining pulp tissue immaterial of the access cavity design.

Root canal irrigants influence the hydrophobicity and adherence of Staphylococcus epidermidis to root canal dentin: an in vitro study

Objectives To determine the effect of root canal irrigants on the hydrophobicity and adherence of Staphylococcus epidermidis (S. epidermidis) to root canal dentin in vitro. Materials and Methods Root dentin blocks (n = 60) were randomly divided into 4 groups based on the irrigation regimen: group 1, saline; group 2, 5.25% sodium hypochlorite (NaOCl); group 3, 5.25% NaOCl followed by 17% ethylenediaminetetraacetic acid (EDTA); group 4, same as group 3 followed by 2% chlorhexidine (CHX). The hydrophobicity of S. epidermidis to root dentin was calculated by cell surface hydrophobicity while the adherence was observed by fluorescence microscopy, and bacteria were quantified using ImageJ software (National Institutes of Health). Statistical analysis of the data was done using Kruskal-Wallis test and Mann-Whitney U test (p = 0.05). Results The hydrophobicity and adherence of S. epidermidis to dentin were significantly increased after irrigating with group 3 (NaOCl-EDTA) (p < 0.05), whereas in group 4 (NaOCl-EDTA-CHX) both hydrophobicity and adherence were significantly reduced (p < 0.05). Conclusions The adherence of S. epidermidis to dentin was influenced differently by root canal irrigants. Final irrigation with CHX reduces the bacterial adherence and may impact biofilm formation.

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.

Cone-beam computed tomographic and histological investigation of regenerative endodontic procedure in an immature mandibular second premolar with chronic apical abscess

AIM The aim of the present study was to investigate the tissue generated after regenerative endodontic procedure (REP) in the root canal space of an immature mandibular second premolar with pulp necrosis and chronic apical abscess using cone-beam computed tomographic (CBCT) and histological methods. METHODS REP was performed in an immature mandibular second premolar. At the 3-year follow up, CBCT scans were taken to evaluate the outcome of treatment. As the tooth was not restorable to function, it was extracted and processed for histological examination. RESULTS CBCT showed a reduction in size of the periradicular radiolucency, with a marginal increase in root length. Apical closure and thickening of the root canal walls were apparent. Histologically, the root canal space was filled with minimally-inflamed fibrous connective tissue. Some cementum-like mineralized connective tissue was evident on the internal canal walls. The apical third showed cementum-like deposits at the apex and the outer canal walls, without dentin formation. CONCLUSIONS The present study of a structurally-failed tooth with prior REP demonstrates that the tissue formed within the root canal space was fibrous connective tissue with cementum-like deposition in the canal space. No evidence of dentin- or pulp-like tissue was found.

Unusual root canal morphology of mandibular first premolar and its management: A rare case report

Clinicians proceed the canal exploration according to the literature so far reported. At times, there are apparent variations in the teeth. These discrepancies should be thoroughly surveyed and piled up to date. One such rare complexity of canal morphology was discussed in the present case. A 48-year-old female patient referred to the endodontic clinic for full-mouth rehabilitation. On intraoral hard-tissue examination, decay was noted in multiple teeth which were confirmed by an orthopantomogram and endodontic treatment plan was suggested. The patient was prepared for the access opening of right mandibular first premolar (tooth #44) before which endodontic treatment of first and second quadrants was completed. The cone-beam computed tomography (CBCT) images revealed that tooth # 44 had two separate roots and four distinct root canals (mesiobuccal, mesiolingual, distobuccal, and distolingual). Root canal treatment was completed in two visits. Postoperative CBCT was advised to confirm the obturation of all the canals.

Acidic and alkaline chemicals’ influence on a tricalcium silicate-based dental biomaterial: CHARACTERIZATION OF TRICALCIUM SILICATE

Bioactive hydraulic tricalcium silicate materials are commonly used in several dental procedures. Mineral Trioxide Aggregate (MTA) is one such material, which is used in a variety of clinical applications, the most recent of which is root canal sealing material, during which, the MTA potentially comes in contact with remnants of the chemical agents used for disinfecting root canals. The effects of commonly used root canal irrigating solutions on MTA have not been investigated in depth, thus far. The aim of this study was to determine the effect of five common chemical agents used in root canal preparation (sodium hypochlorite/NaOCl, ethylene diaminetetraacetic acid/EDTA, mixture of sodium hypochlorite and etidronic acid/NaOCl + EA, mixture of EDTA and Chlorhexidine/QMix, or saline) on a commercial tricalcium silicate (MTA Plus). Samples were analyzed using scanning electron microscopy with energy dispersive spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy and Inductively coupled plasma techniques to see effects of phases formed and calcium ion release. Specimens immersed in NaOCl and NaOCl + EA had strong peaks for calcium hydroxide, but materials exposed to EDTA and QMix had lesser XRD peaks for calcium hydroxide. The calcium hydroxide peak in the XRD indicates hydration of tricalcium silicate and formation of amorphous calcium silicate hydrate. Calcium released from samples immersed in EDTA and NaOCl was less than in NaOCl + EA and QMix solutions. Fewer calcium phosphate crystals and less calcium hydroxide were observed with the samples in NaOCl, EDTA and QMix, which could have an important impact as it negatively influences the bioactivity.

Immunohistochemical characterization of stem cell and differentiation markers of the dental pulp of human natal teeth

Aim: Dental pulp stem cells, which are primarily derived from the pulp tissues of human teeth, have rarely been obtained from natal teeth. This study investigated the stem cell and differentiation markers of the dental pulp of natal teeth using immunohistochemistry. Materials & Methods: The pulp tissue from extracted natal teeth (n = 2) of a 20-day-old healthy male was examined for immunohistochemical expression of stem cell (Oct-4 and SOX 2) and differentiation markers (Nestin, CD 44, desmin, osteopontin and Ki- 67). Results: The pulp tissue of the natal teeth expressed immunopositivity for nestin, CD 44 and SOX2. Conclusion: Natal teeth, if preserved properly, could serve as sources of dental pulp stem cells that are an improvement on deciduous teeth.

Effectiveness of ultrasonically activated irrigation on root canal disinfection: a systematic review of in vitro studies

ObjectivesReduction of microbial load from the root canal systems is a pre-requisite for healing of lesions of endodontic origin. Such microbial reduction is influenced by the method of irrigant delivery and activation. The aim of this systematic review was to compare the effect of ultrasonically activated irrigation (UAI) with other irrigation techniques on the reduction of microorganisms during root canal disinfection.Materials and methodsThe research question was created based on the PICO strategy. Two reviewers independently performed a comprehensive literature search in electronic databases. Following application of inclusion and exclusion criteria to the selected articles, a systematic data extraction sheet was constructed. The selected articles were assessed using methodological quality scoring protocol. The risk of bias in selected studies was critically assessed by two reviewers.ResultsA total of 15 articles were included for the systematic review. The included studies were heterogeneous in study design; hence, meta-analysis was not performed. The overall risk of bias for the selected studies was moderate. Overall, UAI showed superior reduction of microbial counts, resulting in better disinfection compared to other irrigation systems chosen for comparison in this review.ConclusionThe use of UAI can bring about superior microbial reduction within the root canal system compared to other irrigant activation techniques.Clinical relevanceActivation of irrigants with ultrasonic brings about significant bacterial reduction from the root canal systems compared to other methods of irrigant activation and conventional syringe irrigation. This might help in improving the outcome of root canal treatment.