The use of sodium hypochlorite mixed with etidronic acid during canal preparation increases debris extrusion

The purpose of this study was to compare the impact of different irrigation protocols on debris extrusion. Single-rooted teeth were distributed into groups based on the irrigation protocols (n = 40): 2.5% NaOCl (biomechanical preparation: 20 mL and final irrigation: 5 mL); 2.5% NaOCl (biomechanical preparation: 20 mL) + 17% EDTA (final irrigation: 2 mL) + 2.5% NaOCl (final irrigation: 3 mL); and a mixture of 5% NaOCl +18% HEDP (biomechanical preparation: 20 mL and final irrigation: 5 mL). The canals were prepared using a reciprocating instrument size 40/0.06. For final irrigation, the groups were reassigned based on the agitation methods (n = 10): (a) no agitation; (b) ultrasonic; (c) sonic; and (d) continuous rotation. The control group (n = 10) received saline solution without agitation. The amount of debris extruded was measured by weight and analysed using One-way ANOVA (α < 0.05). The subgroups treated with NaOCl + HEDP mixture showed a significantly higher amount of extruded debris (p < 0.05), while there was no difference among agitation methods in all groups (p > 0.05).

Apical extrusion prevents apoptosis from activating an acute inflammatory program in epithelia

Apoptosis is traditionally considered to be an immunologically silent form of cell death. Multiple mechanisms exist to ensure that apoptosis does not stimulate the immune system to cause inflammation or autoimmunity. Against this expectation, we now report that epithelia are programmed to provoke, rather than suppress, inflammation in response to apoptosis. We found that an acute inflammatory response led by neutrophils occurs in zebrafish and cell culture when apoptotic epithelial cells cannot be expelled from the monolayer by apical extrusion. This reflects an intrinsic circuit where ATP released from apoptotic cells stimulates epithelial cells in the immediate vicinity to produce interleukin-8 (IL-8). Apical extrusion therefore prevents inappropriate epithelial inflammation by physically eliminating apoptotic cells before they can activate this pro-inflammatory circuit. This carries the implication that epithelia may be predisposed to inflammation, elicited by sporadic or induced apoptosis, if apical extrusion is compromised.

Accumulation of annexin A2 and S100A10 prevents apoptosis of apically delaminated, transformed epithelial cells

In various epithelial tissues, the epithelial monolayer acts as a barrier. To fulfill its function, the structural integrity of the epithelium is tightly controlled. When normal epithelial cells detach from the basal substratum and delaminate into the apical lumen, the apically extruded cells undergo apoptosis, which is termed anoikis. In contrast, transformed cells often become resistant to anoikis and able to survive and grow in the apical luminal space, leading to the formation of multilayered structures, which can be observed at the early stage of carcinogenesis. However, the underlying molecular mechanisms still remain elusive. In this study, we first demonstrate that S100A10 and ANXA2 (Annexin A2) accumulate in apically extruded, transformed cells in both various cell culture systems and murine epithelial tissues in vivo. ANXA2 acts upstream of S100A10 accumulation. Knockdown of ANXA2 promotes apoptosis of apically extruded RasV12-transformed cells and suppresses the formation of multilayered epithelia. In addition, the intracellular reactive oxygen species (ROS) are elevated in apically extruded RasV12 cells. Treatment with ROS scavenger Trolox reduces the occurrence of apoptosis of apically extruded ANXA2-knockdown RasV12 cells and restores the formation of multilayered epithelia. Furthermore, ROS-mediated p38MAPK activation is observed in apically delaminated RasV12 cells, and ANXA2 knockdown further enhances the p38MAPK activity. Moreover, the p38MAPK inhibitor promotes the formation of multilayered epithelia of ANXA2-knockdown RasV12 cells. These results indicate that accumulated ANXA2 diminishes the ROS-mediated p38MAPK activation in apically extruded transformed cells, thereby blocking the induction of apoptosis. Hence, ANXA2 can be a potential therapeutic target to prevent multilayered, precancerous lesions.

Apical Extrusion: Is It an Inherent Occurrence During Every Endodontic Treatment?

The aim of this literature review was to analyze all available scientific data on apical extrusion and to identify and associate the possible factors influencing the occurrence of apical extrusion, ranging from the choice of the canal shaping system, the irrigation technique, to the choice of diameter and the apical limit of preparation. A bibliographic search for relevant articles on apical extrusion of debris, irrigants, and bacteria was performed using the following databases: PubMed, Cochrane Library, and ScienceDirect. This search identified articles published between 2010 and 2023 in two languages (French and English). After selective sorting, 25 relevant documents were included. All the studies retained clearly agree on the inherent nature of apical extrusion during endodontic treatment. At the same time, we also understand that the amount of extrusion can be influenced by a number of parameters throughout endodontic therapy. According to this review, despite the undeniable nature of apical extrusion during endodontic therapy, studies with relatable experimental models that approach in vivo conditions are required to establish exploitable conclusions regarding apical extrusion and its prevention.

Apical extrusion of debris when using OneCurve, ProTaper Next and TruNatomy in curved canals

BACKGROUND

The extrusion of apical debris is related to various factors, and may be affected by variations in technique or instrumentation system. Although the extrusion cannot be completely prevented, it is crucial to minimize the amount of extruded material.

OBJECTIVES

The present study aimed to compare apical debris extrusion by the novel TruNatomy (TRN), OneCurve (OC) and ProTaper Next (PTN) instruments in curved root canals.

MATERIAL AND METHODS

A total of 60 multi-rooted human mandibular molar teeth with moderate and severe curvature were selected and randomly divided into 3 groups. The root canals were prepared with the OC, TRN and PTN files. For collecting the debris extruded through the apical foramen, Eppendorf tubes were used. After the vaporizing period, the tubes were re-weighed, and the amount of the extruded debris was calculated by subtracting the initial weight from the final weight. Statistical analysis was performed with the Shapiro-Wilk and Kruskal-Wallis tests. The statistical significance level was set at p < 0.05.

RESULTS

The least amount of debris was extruded with TRN and the greatest with PTN, but the difference between the groups was not significant (p = 0.257).

CONCLUSIONS

All instrumentation systems were associated with debris extrusion. The tested file systems presented similar results in terms of apical debris extrusion in curved canals. The novel TRN system demonstrated promising results, comparable to OC and PTN.

Comparative Evaluation of Extrusion of Apical Debris in Primary Maxillary Anterior Teeth Using Two Different Rotary Systems and Hand Files: An In Vitro Study

Successful outcome of pulp therapy depends on good chemomechanical preparation of the canals. This is completed with the help of various upcoming rotary and hand files. However, during this preparation, there might be an apical extrusion of the debris which may result in postoperative complications. The aim of this study was to evaluate and compare the number of debris apically extruded during canal preparation using two different pediatric rotary file systems and conventional hand file systems in primary teeth. 60 primary maxillary central incisors that were extracted due to trauma or untreated dental caries with no signs of resorption were taken. Canal preparation was executed using three different file systems: Group A: Group A hand K file system, Group B Kedo S Plus, Group C Kedo SG Blue. For each of these files using the Myers and Montgomery model, the pre- and post-weight of the eppendorf tube was assessed to quantify the number of apical debris. The maximum extrusion of apical debris was noticed with the Hand K-file system. The least debris was noticed in the Kedo S Plus file system. Statistical analysis revealed that there were highly significant differences in apical extrusion and debris when comparing hand files and rotary files and also between the two rotary files used. Apical debris collection is an unavoidable outcome of canal instrumentation. Among the file systems compared, rotary files had lesser extrusion when compared to hand files. Among the rotary files, Kedo S plus showed normal extrusion compared to SG Blue.

Apical extrusion of sodium hypochlorite in immature teeth: comparison of three different cleaning protocols

This study compared standard needle irrigation, passive ultrasonic irrigation, XP-Endo Finisher and Easy Clean in the apical extrusion of sodium hypochlorite (NaOCl) in a model simulating immature teeth. Ten bovine teeth were maintained in suspension in a container with the apical portion in contact with 0.2% agarose gel containing 0.1% metacresol purple. The canals were irrigated with 2.5% NaOCl, according to each irrigation protocol. After 3 min, apical extrusion of NaOCl was observed by the colour gel change when in contact with NaOCl. The containers were photographed, and the NaOCl extrusion area was measured. All protocols showed NaOCl extrusion, providing similar area (P > 0.05). Considering the similarity among the studied protocols, all of them can be considered during the endodontic treatment of immature teeth. Further studies on the particularities of immature teeth should be performed to evaluate cell viability, cleaning efficiency, disinfection capacity and dentin removal promoted by the irrigation protocols.

Calcium sparks enhance the tissue fluidity within epithelial layers and promote apical extrusion of transformed cells

In vertebrates, newly emerging transformed cells are often apically extruded from epithelial layers through cell competition with surrounding normal epithelial cells. However, the underlying molecular mechanism remains elusive. Here, using phospho-SILAC screening, we show that phosphorylation of AHNAK2 is elevated in normal cells neighboring RasV12 cells soon after the induction of RasV12 expression, which is mediated by calcium-dependent protein kinase C. In addition, transient upsurges of intracellular calcium, which we call calcium sparks, frequently occur in normal cells neighboring RasV12 cells, which are mediated by mechanosensitive calcium channel TRPC1 upon membrane stretching. Calcium sparks then enhance cell movements of both normal and RasV12 cells through phosphorylation of AHNAK2 and promote apical extrusion. Moreover, comparable calcium sparks positively regulate apical extrusion of RasV12-transformed cells in zebrafish larvae as well. Hence, calcium sparks play a crucial role in the elimination of transformed cells at the early phase of cell competition.

Apical pressures generated by several canal irrigation methods: A laboratory study in a maxillary central incisor with an open apex

Aim

A laboratory study to determine the apical pressure generated by seven canal irrigation methods in an anterior tooth with an open apex.

Methodology

Canal irrigation was performed on a 3D‐printed central maxillary incisor with an open apex (maximum diameter of 2.1 mm). Ultrasonically activated irrigation (UAI), sonic activation (EDDY), negative pressure irrigation (EndoVac), the self‐adjusting file (SAF) and the XP‐endo Finisher were employed at tooth length (TL), TL—1 mm, TL—2 mm and TL—3 mm. UAI was tested at three intensity levels additionally. Hydrodynamic irrigation with RinsEndo was performed in the pulp chamber, at the canal orifice, the coronal third, the middle of the canal and at TL. Er:YAG laser activation, at four frequency settings, was performed in the pulp chamber and at the orifice of the canal. The pressure of the fluid towards the canal terminus generated by activation was directly transferred to a pressure sensor with a range of 0 to 120 mmHg and a response time of ≤0.5 ms. The critical threshold for apical extrusion of the irrigant was set at 5.73 mmHg (lower limit of the central venous pressure: 5.88 ± 0.15 mmHg). Each experiment was repeated ten times. The tests were followed by descriptive analyses (maximum, mean, standard deviation, 95% confidence interval).

Results

EndoVac, the SAF, the XP‐endo Finisher, and UAI never exceeded the critical threshold at any insertion depth or intensity level. Er:YAG laser activation exceeded the critical threshold exclusively at frequency settings that varied from the manufacturer's recommendation. EDDY at TL and RinsEndo at any insertion depth exceeded the critical threshold in 100% of the measurements. EDDY at TL—1,—2, and—3 mm crossed the critical threshold in 30%, 10%, and 20% of the measurements, respectively.

Conclusions

In a simulated maxillary central incisor with an open apex, irrigation with EndoVac, Er:YAG laser activation, UAI, the SAF, and the XP‐endo Finisher generated apical pressures below the critical threshold of 5.73 mmHg. By contrast, using EDDY and RinsEndo for irrigation produced higher apical pressures that exceeded the critical threshold.

Mechanotransduction activates RhoA in the neighbors of apoptotic epithelial cells to engage apical extrusion

Epithelia must eliminate apoptotic cells to preserve tissue barriers and prevent inflammation.¹ Several different mechanisms exist for apoptotic clearance, including efferocytosis^2,3 and apical extrusion.^4,5 We found that extrusion was the first-line response to apoptosis in cultured monolayers and in zebrafish epidermis. During extrusion, the apoptotic cell elicited active lamellipodial protrusions and assembly of a contractile extrusion ring in its neighbors. Depleting E-cadherin compromised both the contractile ring and extrusion, implying that a cadherin-dependent pathway allows apoptotic cells to engage their neighbors for extrusion. We identify RhoA as the cadherin-dependent signal in the neighbor cells and show that it is activated in response to contractile tension from the apoptotic cell. This mechanical stimulus is conveyed by a myosin-VI-dependent mechanotransduction pathway that is necessary both for extrusion and to preserve the epithelial barrier when apoptosis was stimulated. Earlier studies suggested that release of sphingosine-1-phosphate (S1P) from apoptotic cells might define where RhoA was activated. However, we found that, although S1P is necessary for extrusion, its contribution does not require a localized source of S1P in the epithelium. We therefore propose a unified view of how RhoA is stimulated to engage neighbor cells for apoptotic extrusion. Here, tension-sensitive mechanotransduction is the proximate mechanism that activates RhoA specifically in the immediate neighbors of apoptotic cells, but this also must be primed by S1P in the tissue environment. Together, these elements provide a coincidence detection system that confers robustness on the extrusion response.

Sodium Hypochlorite Extrusion Accidents: Management and Medico-Legal Considerations

Sodium hypochlorite is considered the most widely used irrigant in endodontics as it exhibits effective antimicrobial activity and has potent tissue-dissolving ability. Whilst it is considered safe when used within the confines of the root canal system, it can cause serious complications when inadvertent periradicular extrusion occurs. This article outlines the complications of sodium hypochlorite extrusion and reviews the appropriate management based on the contemporary evidence. Preventive measures are suggested and the relevant medico-legal considerations are outlined.

Evaluation of apically extruded debris during the canal preparation using new heat-treated nickel-titanium files in curved canals

This study compared the amount of apically extruded debris associated with different heat-treated Ni-Ti rotary systems during the preparation of curved root canals of mandibular molars. Sixty extracted human mandibular molars were selected. EdgeFile, K3XF, OneCurve (OC) and ROTATE files were used to prepare both mesial canals of teeth. The initial weight of each Eppendorf tube to be used was calculated using an analytical balance prior to instrumentation. After instrumentation, the tubes were then stored for 5 days in an incubator at 70°C. Each tube was reweighed, and the weight of the dry extruded debris was established by subtracting the pre-instrumentation and post-instrumentation weight of the Eppendorf tubes for each group. All files caused apical extrusion of debris. There was no statistical difference between the ROTATE, EdgeFile, OC and K3XF systems (P > 0.05). All the heat-treated Ni-Ti rotary systems led to similar apical debris extrusion during the canal preparation.

Apically extruded debris produced during glide path preparation using R-Pilot, WaveOne Gold Glider and ProGlider in curved root canals

The present study aimed to compare the apically extruded debris produced during glide path preparation using R-Pilot (RP), WaveOne Gold Glider (WGG) and ProGlider (PG) with the subsequent preparation using Reciproc Blue in curved root canals. Mesial roots of mandibular molars with angle of curvature between 25° and 35° were selected (n = 20). The Myers and Montgomery method was used to collect and assess apically extruded debris. The glide path was prepared either manually with K-file, ProGlider, R-Pilot or WaveOne Gold Glider. Manual preparation group produced the highest amount of apically extruded debris (P < 0.05), while all groups caused debris extrusion. There were no significant differences among the extruded debris caused by RP, PG and WGG groups (P > 0.05). Apically extruded debris produced by engine-driven reciprocational or continuous rotational single file glide path instruments was similar, whereas manual glide path preparation was associated with the greatest amount of extruded debris.

Influence of Different Irrigation Solutions and Instrumentation Techniques on the Amount of Apically Extruded Debris

OBJECTIVE

The objective of the present study was to evaluate the influence of different irrigation solutions on the amount of extruded residues apically, varying the instrumentation technique in manual, continuous rotation, or reciprocation motions. The amounts of residue for each irrigation solution was also assessed.

METHODS

Two tests were performed. In the first test, 90 mandibular premolars were divided into nine groups (n=10). Each group was subjected to a different technique: ProTaper Universal, WaveOne Gold, or manual instruments, with different irrigation solutions [2.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) gel, or distilled water]. During the preparation of the root canal, the apically extruded material was collected in previously weighed glass vials. In the second test, irrigation solutions were weighed separately with the same weighing method. Data were analyzed using the Kolmogorov-Smirnov, one-way and two-way ANOVA, Levene, Tukey, and Games-Howell tests.

RESULTS

Apically extruded debris was observed in all groups. ProTaper Universal with continuous rotation using 2% CHX gel resulted in the greatest amount of debris (P<0.001). There were significant differences in the amounts of residue among the different groups (P<0.001). Moreover, when the weighing of the irrigation solutions was tested, the 2.5% NaOCl solution produced the greatest amount of residues compared with other irrigation solutions.

CONCLUSION

Different irrigation solutions influenced the amount of apically extruded debris during the preparation of the canal among the different instrumentation techniques. The ProTaper technique using 2% CHX gel resulted in the greatest amount of apically extruded debris.

Obesity Suppresses Cell-Competition-Mediated Apical Elimination of RasV12-Transformed Cells from Epithelial Tissues. Cell Rep. 2018;23:974-982. [PMID: 29694905 PMCID: PMC6314181 DOI: 10.1016/j.celrep.2018.03.104]

Recent studies have revealed that newly emerging transformed cells are often eliminated from epithelial tissues via cell competition with the surrounding normal epithelial cells. This cancer preventive phenomenon is termed epithelial defense against cancer (EDAC). However, it remains largely unknown whether and how EDAC is diminished during carcinogenesis. In this study, using a cell competition mouse model, we show that high-fat diet (HFD) feeding substantially attenuates the frequency of apical elimination of RasV12-transformed cells from intestinal and pancreatic epithelia. This process involves both lipid metabolism and chronic inflammation. Furthermore, aspirin treatment significantly facilitates eradication of transformed cells from the epithelial tissues in HFD-fed mice. Thus, our work demonstrates that obesity can profoundly influence competitive interaction between normal and transformed cells, providing insights into cell competition and cancer preventive medicine.

Sasaki et al. demonstrate using a cell competition mouse model that high-fat diet feeding substantially attenuates the frequency of apical elimination of RasV12-transformed cells from intestinal and pancreatic epithelia. These results indicate that obesity can profoundly influence competitive interaction between normal and transformed cells at the initial stage of carcinogenesis.

Evaluation of the apical extrusion of sodium hypochlorite gel in immature permanent teeth: An in vitro study

BACKGROUND

Sodium hypochlorite (NaOCl) gel has been suggested as a safer substitute in open apices as compared to solution, with the same antimicrobial effect.

OBJECTIVES

This study aimed to compare the amount of the apical extrusion of NaOCl gel and solution in immature permanent teeth.

MATERIAL AND METHODS

A crossover in vitro study was conducted at the Department of Pediatric Dentistry, Faculty of Dentistry of Damascus University, Syria. Thirty freshly extracted immature single-rooted human premolars were decoronated and the cavity was then accessed. The teeth were radiographed to determine the mesiodistal dimension of the apex. In addition, the surface area of the apical foramen was calculated with Adobe Photoshop® to evaluate the amount of extrusion from the whole surface of the apex. The teeth were divided into 2 groups according to the size of the apex: ≤2.5 mm (group A) and >2.5 mm (group B); each group was irrigated with 5 mL of NaOCl solution and 2 different commercial types of NaOCl gel for 60 s, and then the extruded irrigant was measured in a plastic vial.

RESULTS

The data was analyzed using the Kruskal-Wallis analysis. Based on the observed results, a statistically significant difference was noted (p = 0) between NaOCl solution and gel when the apical diameter was ≤2.5 mm, while there was no significant difference between the 2 types of NaOCl gel. No statistically significant difference was observed (p = 0.2) between NaOCl solution and gel when the apical diameter was >2.5 mm.

CONCLUSIONS

Sodium hypochlorite gel is safer than solution when irrigating immature teeth with the apical diameter ≤2.5 mm.

Apically extruded debris and irrigants during root canal filling material removal using Reciproc Blue, WaveOne Gold, R-Endo and ProTaper Next systems

Background. The present study aimed to compare the amount of apically extruded debris and irrigants produced by various nickel-titanium instruments.

Methods. A total of 100 single-rooted mandibular premolar teeth were root canal treated and prepared for agar gel model. The root canal fillings were removed using Reciproc Blue, ProTaper Next, R-Endo, WaveOne Gold systems or hand instrumentation. The mean weights of apically extruded materials were calculated. Data were statistically analyzed using one-way ANOVA and post hoc Bonferroni tests.

Results. Hand instrumentation resulted in significantly more debris and irrigants than other systems (P<0.05). The mean amount of apically extruded debris and irrigants produced by Reciproc Blue system was significantly greater than motordriven instruments (P<0.05). No significant difference was detected between ProTaper Next and WaveOne Gold systems (P>0.05), while they both produced significantly less apically extruded material than R-Endo system (P<0.05).

Conclusion. All the instruments caused apical extrusion. ProTaper Next and WaveOne Gold systems were associated with significantly less apical extrusion.

An in vitro Study

OBJECTIVES

The present study was undertaken to evaluate and compare the apical extrusion of irrigant and depth of irrigant penetration into dentine using the EndoVac irrigating system and manual irrigation system in primary molar teeth.

STUDY DESIGN

Twenty five extracted primary molars satisfying the inclusion and exclusion criteria were divided into two groups with 29 roots in each group with an equal distribution of apical foramen area. The teeth were mounted in pre-weighed glass bottles and the canals were irrigated with 5.25% sodium hypochlorite solution mixed with acid fuchsin using either of irrigating systems according to the group ascertained. The amount of irrigant extruded was recorded. The roots were sectioned at two mm, four mm and six mm from the apex and examined under a stereomicroscope for depth of irrigant penetration.

RESULTS

Apical extrusion of the irrigant solution was significantly less with the EndoVac system (1.18±1.04) when compared with the manual irrigation system (2.3±1.55) (P=0.002)*. Results showed that greater irrigant penetration was achieved using the EndoVac irrigation system compared to the manual irrigation system (P= 0.000)*. With both the irrigation systems, the depth of irrigant penetration was better in the six mm sections followed by the four mm sections and two mm sections (P=0.000)*.

CONCLUSION

The EndoVac irrigation system demonstrated better efficacy compared to manual irrigation system with less apical extrusion and better depth of irrigant penetration into dentine.

Long-term live imaging of the Drosophila adult midgut reveals real-time dynamics of division, differentiation and loss

Organ renewal is governed by the dynamics of cell division, differentiation and loss. To study these dynamics in real time, we present a platform for extended live imaging of the adult Drosophila midgut, a premier genetic model for stem-cell-based organs. A window cut into a living animal allows the midgut to be imaged while intact and physiologically functioning. This approach prolongs imaging sessions to 12–16 hr and yields movies that document cell and tissue dynamics at vivid spatiotemporal resolution. By applying a pipeline for movie processing and analysis, we uncover new and intriguing cell behaviors: that mitotic stem cells dynamically re-orient, that daughter cells use slow kinetics of Notch activation to reach a fate-specifying threshold, and that enterocytes extrude via ratcheted constriction of a junctional ring. By enabling real-time study of midgut phenomena that were previously inaccessible, our platform opens a new realm for dynamic understanding of adult organ renewal.

Comparative Safety of Needle, EndoActivator, and Laser-Activated Irrigation in Overinstrumented Root Canals

OBJECTIVE

To evaluate the safety of sodium hypochlorite (NaOCl) irrigation using three different techniques during the final rinse in overinstrumented root canals.

BACKGROUND DATA

The effect of irrigant activation on irrigant extrusion from overinstrumented root canals is still unclear.

METHODS

A total of 30 single-rooted teeth were decoronated. The working lengths were determined and the roots were divided into two groups of 15 teeth each: group 1, instrumentation 0.5 mm short of the apical foramen and group 2, instrumentation 0.5 mm beyond the apical foramen (overinstrumented). Needle irrigation (NI), sonic irrigation with EndoActivator (EAI), and laser-activated irrigation (LAI) were used for the final rinse in each group; each root underwent the three irrigation procedures in a randomized crossover manner. A modified container-foam model was used to collect apically extruded NaOCl. The weight of the extruded NaOCl was calculated by subtracting the initial weights of the containers from their final weights. All data were statistically analyzed.

RESULTS

The amount of NaOCl extrusion was similar with all three irrigation systems in group 1. In group 2, the amount of extruded NaOCl was significantly greater with EAI than with NI and LAI. EAI and LAI caused significantly greater extrusion in group 2 than in group 1.

CONCLUSIONS

EAI, NI, and LAI are equally safe for irrigating canals with intact apices. However, the risk of irrigant extrusion can increase in overinstrumented canals, with EAI associated with a greater risk compared with NI and LAI.

Rab5-regulated endocytosis plays a crucial role in apical extrusion of transformed cells

Newly emerging transformed cells are often eliminated from epithelial tissues. Recent studies have revealed that this cancer-preventive process involves the interaction with the surrounding normal epithelial cells; however, the molecular mechanisms underlying this phenomenon remain largely unknown. In this study, using mammalian cell culture and zebrafish embryo systems, we have elucidated the functional involvement of endocytosis in the elimination of RasV12-transformed cells. First, we show that Rab5, a crucial regulator of endocytosis, is accumulated in RasV12-transformed cells that are surrounded by normal epithelial cells, which is accompanied by up-regulation of clathrin-dependent endocytosis. Addition of chlorpromazine or coexpression of a dominant-negative mutant of Rab5 suppresses apical extrusion of RasV12 cells from the epithelium. We also show in zebrafish embryos that Rab5 plays an important role in the elimination of transformed cells from the enveloping layer epithelium. In addition, Rab5-mediated endocytosis of E-cadherin is enhanced at the boundary between normal and RasV12 cells. Rab5 functions upstream of epithelial protein lost in neoplasm (EPLIN), which plays a positive role in apical extrusion of RasV12 cells by regulating protein kinase A. Furthermore, we have revealed that epithelial defense against cancer (EDAC) from normal epithelial cells substantially impacts on Rab5 accumulation in the neighboring transformed cells. This report demonstrates that Rab5-mediated endocytosis is a crucial regulator for the competitive interaction between normal and transformed epithelial cells in mammals.

Paper points revisited: risk of cellulose fibre shedding during canal length confirmation

AIM

To compare the degree of fibre shedding by six brands of endodontic paper point when used for the paper point technique (PPT) of working length confirmation.

METHODOLOGY

An in vitro model simulating the clinical use of paper points in PPT was used to assess the degree of fibre shedding of six brands of size 20, .02 taper paper point. Whilst observing the artificial terminal foramen with polarized light microscopy, the number of fibres shed directly (point inserted 1 mm beyond the terminal foramen) and indirectly (point inserted to length then a gutta-percha point inserted) was assessed. The degree of direct fibre shedding as a function of brand was analysed with Fisher's exact test and multiple pairwise comparisons. Indirect fibre shedding was analysed with Kruskal-Wallis and Wilcoxon rank-sum tests.

RESULTS

All brands shed fibres both directly and indirectly, with a significant influence of brand on the proportion of fibres shed directly (P < 0.0306) and on the mean number of fibres shed indirectly (P < 0.0001). Post hoc analysis demonstrated a similar hierarchy of point integrity for both tests with Classic (UnoDent, Witham, UK) shedding significantly more than other brands and SS White (Gloucester, UK) and Antaeos^® (VDW, Munich, Germany) shedding the least.

CONCLUSION

All brands of paper point may shed cellulose fibres both directly and indirectly with a significant influence of brand on the degree of fibre shedding. Further work should be undertaken to develop biocompatible absorbent dental points.

Comparison of apically extruded debris associated with several nickel-titanium systems after determining working length by apex locator

Background/Aim:

To compare apically extruded debris using ProTaper Universal (PTU), ProTaper Next (PTN), WaveOne (WO), Twisted File (TF), M-Two (MT), and Revo-S (RS) after determining the working length (WL) with root ZX.

Materials and Methods:

Seventy-two teeth were selected. The WL determination was performed with root ZX. The teeth were divided into six experimental groups, randomly. In groups, root canals were prepared with PTU to size F4/0.06, with PTN to size X4/0.06, with WO to size 40/0.08, with TF to size 40/0.04, with MT to size 40/0.06, and with RS to size AS40/0.06. After preparations were completed, final irrigation was performed with 2 mL distilled water, and a total of 10 mL of distilled water was used in each tooth. Tubes were stored in an incubator at 68°C for 5 days to evaporate the distilled water before weighing the dry debris. Data were analyzed by the Mann–Whitney U-test.

Results:

The RS group led to the highest amount of extruded debris, however, WO led to the least amount of extruded debris. There was no statistically difference among the groups (P > 0.05).

Conclusions:

The authors conclude that the results obtained might depend on the apex locator used to determine the WL.

Effect of root canal dimensions, injection rate, and needle design on the apical extrusion of an irrigant: an in vitro study

AIM

The purpose of this study was to determine the effect of root canal dimensions, type of needle, and injection rate on the apical extrusion of an irrigant in a simulated root canal.

METHODS

Ten students used two types of 28-gauge needles, to deliver 3 mL irrigant solution into artificial canals prepared in acrylic blocks to a standard size of ISO 25, 30, or 40 (0.06 taper; n = 10). Each block was preweighed to the nearest microgram before and after irrigation once the canal was dried with paper points. This was repeated with a syringe pump at a flow rate of 50, 100, 200 or 300 μL/s with the needle inserted to a standard depth.

RESULTS

Significant differences were observed between the side-vented and notched-end needles when the rate of irrigation was higher than 100 μL/s, and when the apical size was below ISO 40 (P < 0.001). The amount of extrusion was more variable and significantly higher when irrigation was performed manually, compared with the syringe pump groups.

CONCLUSIONS

Injection rates above 100 μL/s increased the risk of extrusion, whereas increasing the apical canal size to ISO 40 reduced the amount of extrusion in all groups. The use of a side-vented needle negates the injection-rate effects.

Weight of apically extruded debris following use of two canal instrumentation techniques and two designs of irrigation needles

AIM

To compare the weight of apically extruded debris associated with canal shaping using K-files, and the Revo-S system using two different needle tips, open-ended and side-vented.

METHODOLOGY

Forty freshly extracted mandibular premolar teeth were divided into four groups as follows; Group 1a: Hand instrumentation of root canal with open-ended needle used to provide irrigation, Group 1b: Hand instrumentation with a two side-port needle, Group 2a: Revo-S preparation with open-ended needle, Group 2b: Revo-S preparation with a two side-port needle. One Eppendorf tube for each tooth was weighed with a 0.0001 electronic weighing machine before instrumentation procedures. During instrumentation, irrigation was performed after every instrument with 1 mL distilled water. On completion of the preparation, teeth were removed from the Eppendorf tubes. All of the tubes were incubated at 37 °C for 15 days, to evaporate the irrigant. After the incubation period, tubes were weighed again. The difference between pre-and post-debris weights was calculated, and statistical evaluation was performed using analysis of variance at 0.05 level of significance.

RESULTS

No statistically significant difference was observed between K-files and the RevoS system. A significant difference was observed between needles (P < 0.05). Open-ended needles were associated with significantly more debris than side-vented needles (P < 0.05).

CONCLUSIONS

Both hand and rotary canal instrumentation resulted in extrusion of debris beyond the apical foramen. No significant difference was observed between K-files and Revo-S system. Open-ended needles were associated with significantly more extruded debris than two side-port needles.