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Background: The aim of this investigation was to assess the apical extrusion potential of sodium hypochlorite (NaOCl) in agarose-embedded mandibular first premolars employing four final agitation procedures. Methods: Based on CBCT confirmation of single oval-shaped canals, one hundred extracted mandibular first premolars were chosen. Using 5.25% NaOCl, the teeth were prepared using the XP Endo Shaper and divided into experimental and control groups. The following were the experimental groups: Group 1 comprised the XP-Endo Finisher, Group 2 the Ultrasonic Activation, Group 3 the Gentle File Finisher Brush, and Group 4 the 27-gauge side-vented needle. To test extrusion, the teeth were placed in a 0.2% agarose gel that contained the pH-sensitive dye m-cresol purple, allowing pixel quantification via ImageJ software (version 1.54i). Results: The XP Endo Finisher featured the most pixels, depicting higher apical extrusion (p < 0.01), followed by the side-vented needle, Gentle File Finisher Brush, and PUI, while the Control Group endured no extrusion. Conclusions: The effective irrigation method for root canal therapy is critical, especially in situations of open apices, resorption, or perforation. According to in vitro experiments, the XP-Endo Finisher has the maximum sodium hypochlorite extrusion, which is determined by parameters such as apical preparation size and irrigation system. [ABSTRACT FROM AUTHOR]

Background: To determine the amount of apical extrusion between various file systems during the retreatment procedure and to determine the effect of taper on the same. Materials and Method: Seventy mandibular extracted premolars were taken, and preparation was performed using a Woodpecker file (Woodpecker Medical Instrument Co., Ltd., Guilin, China) (25/0.06). The gutta‑percha (GP) was removed from each specimen with H file (#40/0.02) to simulate retreatment in seven groups (n = 10) using ProTaper Next (PTN;Dentsply, Maillefer, Ballaigues, Switzerland) (PTN) (30/0.07), Reciproc (25/0.08), Hyflex CM (30/0.06), Mtwo (30/0.05), Neoendo flex (30/0.04), Neoendo hybrid (30/0.04), and Flexicon file (30/0.06). The specimens were held with the help of a rubber stopper and put in the Eppendorf tube of volume 4 mL (pre‑weighed before retreatment). The debris that was on the root surface of the specimen was washed with distilled water with 1 mL volume, kept in the oven, and then again weighed after 7 days. Results: Apical extrusion was found in the following order: HYFLEX CM (LEAST) < FLEXICON < PROTAPER NEXT < RECIPROC < NEOENDO FLEX < NEOENDO HYBRID < MTWO (HIGHEST). Conclusion: W Hyflex CM and Flexicon files showed lesser extrusion of debris than others. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aimed to assess the apical extrusion of sodium hypochlorite in immature teeth caused by needle irrigation, ultrasonic irrigation, EDDY, Er:YAG, and diode lasers. Seventy-five human maxillary anterior teeth were selected. After the apical 3 mm of the roots was resected, the canal lumen was enlarged with #2 to #5 Gates-Glidden burs. The teeth were fixed to the lid of a flat-sided clear plastic container, and the plastic containers were filled with 0.2% agarose gel containing 1 mL of 0.1% m-cresol purple. Then, the specimens were allocated into five groups according to the irrigation activation techniques: needle irrigation, ultrasonic irrigation, EDDY, Er:YAG laser, and diode laser. The apical extrusion of sodium hypochlorite caused the color change in the gel. The containers were digitally photographed, and the percentage of pixels of irrigant extrusion (the color change) in each photograph was calculated. The diode laser group showed a significantly lower percentage of pixels than needle irrigation, EDDY, and Er:YAG laser (p < 0.05). The irrigant extrusion value of the ultrasonic irrigation group was significantly lower than that of the EDDY and Er:YAG laser groups (p < 0.05). There was no significant difference between the other groups (p > 0.05). All the groups caused irrigant extrusion in the immature teeth. The diode laser and ultrasonic irrigation caused less sodium hypochlorite extrusion than EDDY and Er:YAG laser. The needle irrigation showed more irrigant extrusion than the only diode laser group. [ABSTRACT FROM AUTHOR]

Aim: The purpose of this research is to compare the amounts of bacteria that are extruded from their apical surfaces during the instrumentation of root canals utilising the K3XF, Protaper Gold, Edge taper Platinum, and Hyflex CM Rotary systems. Materials and methods: Sixty caries free single rooted human maxillary incisor teeth were divided in six groups of ten teeth each. Teeth in each group were instrumented until the working length with the respective rotary file system. The access cavity was made, and the pulp and debris were removed from the canals. On the device for gathering microorganisms, the teeth were mounted. The Fusobacterium Nucleatum (ATCC 25586) was used to infect the root canals, which were then dried at 37 °C for 24 hours. Group I (Control group), no instrumentation was done. Group II used hand K-files, Group III used Protaper gold, Group IV used K3XF, Group V used Edge taper platinum, and Group VI used Hyflex CM rotary file systems. In. The sample was then collected, cultured in Mueller-Hinton agar for 24 hours, and the number of colony-forming units was counted. Statistical analysis: The Kruskal-Wallis nonparametric test and Mann-Whitney U test were applied to determine if significant differences existed among the groups (P< 0.05) Results: Comparing hand K-files to the other four rotary systems, the K3XF file system extruded the fewer number of bacteria. Conclusion: Within the limitations of this study, it can be concluded that all instruments tested produced bacteria from intracanal spaces apically. However, compared to the manual method, engine-driven nickel-titanium devices extruded fewer microorganisms. Comparatively, the K3XF rotary file system extruded less microorganisms than other rotary file systems. [ABSTRACT FROM AUTHOR]

Background: Prevention of the debris from extruding to the periapical region is an important aspect to be taken care of as its extrusion can result in pain, periapical inflammation, and delayed healing owing to the presence of highly infective components in the debris. Aim: The present trial was aimed to compare and assess the amount of debris extruded apically using the single-file reciprocating system - WaveOne GOLD and single file rotary system - OneShape in root canal preparations in vitro. Materials and Methods: Thirty mandibular premolars were divided into two groups (15 samples each) prepared with a single-file reciprocating system - WaveOne GOLD and single-file rotary system - OneShape. Debris extruded was collected and then stored in an incubator. The final weight was calculated after obtaining the mean of three consecutive weights obtained for each tooth. The data were compared using the ANOVA and Turkey's post hoc analysis. Results: Debris extrusions were recorded in both groups and analysis revealed statistical differences in weight before and after the instrumentation procedures in both groups. When compared, reciprocating single file – WaveOne GOLD extruded more debris than rotary single file system – OneShape with a P < 0.001. Conclusions: The rotary instrumentation systems extrude lesser debris apically than the reciprocating instrumentation system. The difference found was statistically significant. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Cell competition is a phenomenon that eliminates unfit cells from cell society, a function vital for maintaining cellular and organismal homeostasis. We previously showed that Madin-Darby canine kidney (MDCK) epithelial cells expressing the active form of the transcriptional coactivator Yes-associated protein (YAP) are apically extruded when surrounded by normal MDCK cells. Although we demonstrated that the arachidonic acid (AA) cascade is involved in YAP-dependent apical extrusion, the metabolic events leading to this outcome remained unclear. Here, we present the results of metabolomic analysis that identified phosphatidylcholine (PC) biosynthesis as the most significant player in this process. Removal of the PC biosynthetic components choline and methionine from culture medium inhibited YAP-dependent apical extrusion. Inhibition of either choline uptake or metabolic cycles involving choline or methionine also decreased YAP-dependent apical extrusion. At the molecular level, active YAP induced expression of the genes encoding glycerophosphocholine phosphodiesterase 1 (GPCPD1) and lecithin–cholesterol acyltransferase (LCAT), which are involved in choline metabolism. Our results indicate that YAP-dependent cell competition depends on YAP-mediated activation of the choline metabolic cycle. • Depletion of both choline and methionine from MDCK cell culture medium inhibits YAP-dependent apical extrusion. • Inhibition of choline or methionine metabolism suppresses YAP-dependent apical extrusion. • YAP upregulates the GPCPD1 and LCAT genes during YAP-dependent apical extrusion. [ABSTRACT FROM AUTHOR]

Background: Prevention of the debris from extruding to the periapical region is an important aspect to be taken care of as its extrusion can result in pain, periapical inflammation, and delayed healing owing to the presence of highly infective components in the debris. Aim: The present trial was aimed to compare and assess the amount of debris extruded apically using the single-file reciprocating system - WaveOne GOLD and single file rotary system - OneShape in root canal preparations in vitro. Materials and Methods: Thirty mandibular premolars were divided into two groups (15 samples each) prepared with a single-file reciprocating system - WaveOne GOLD and single-file rotary system - OneShape. Debris extruded was collected and then stored in an incubator. The final weight was calculated after obtaining the mean of three consecutive weights obtained for each tooth. The data were compared using the ANOVA and Turkey's post hoc analysis. Results: Debris extrusions were recorded in both groups and analysis revealed statistical differences in weight before and after the instrumentation procedures in both groups. When compared, reciprocating single file - WaveOne GOLD extruded more debris than rotary single file system - OneShape with a P ˂ 0.001. Conclusions: The rotary instrumentation systems extrude lesser debris apically than the reciprocating instrumentation system. The difference found was statistically significant. [ABSTRACT FROM AUTHOR]

The endodontic retreatment is a procedure performed on a tooth that received previous endodontic treatment and resulted in failure. The main cause of treatment failure is insufficient cleaning and inadequate obturation. Success of endodontic therapy is largely dependent upon the quality of root canal therapy done. In retreatment cases, the primary objective is the complete removal of gutta percha from the root canal system, which is a very tedious and time consuming process. This study was aimed to evaluate and compare the effective removal of gutta percha and sealer using various endodontic retreatment files. In the present study we compared the efficacy of protaper retreatment files and Reciproc blue retreatment files (R Blue) in removing GP and sealer from root canals. The retreatment procedure was said to be complete when no visible debris were observed on the instrument flutes. The samples were then split into two halves and examined under stereomicroscope, photographed, assessed using AUTOCAD software and percentage of remaining filling material in the coronal, middle and apical third of the canal was calculated in mm². The data was analyzed by using descriptive statistics, Chi square test was done through IBM SPSS statistics 20. The percentages of GP remaining in the coronal 1/3 rd, middle 1/3 rd and apical 1/3 rd region using Reciproc blue retreatment files was less when compared to protaper retreatment file and was found to be statistically significant(p<0.05).Both retreatment files retained gutta percha / sealer remnants within the root canal but Reciproc blue retreatment files were better. [ABSTRACT FROM AUTHOR]

Several lines of evidence indicate that cell competition can occur in mammals. In particular, at the initial stage of carcinogenesis, normal epithelial cells are able to recognize the neighboring transformed cells and actively eliminate them from epithelial tissues. This implies that normal epithelia have anti-tumor activity that does not involve immune cells, which is termed epithelial defense against cancer (EDAC). In this review article, we summarize recent advances on the underlying molecular machinery of EDAC. In addition, we also describe the molecular mechanisms by which transformed cells escape from EDAC to promote carcinogenesis. [ABSTRACT FROM AUTHOR]

Objectives: To compare the remaining root canal filling material, dentin removal, apical transportation, and apical extrusion of debris after the retreatment of canals filled with bioceramic or resin-based sealers using the Reciproc or Reciproc Blue instruments. Materials and methods: Sixty mandibular molars with severely curved mesial roots were selected. The samples were initially instrumented with Reciproc (R25) and then divided into four experimental groups according to the endodontic sealer and retreatment instrument (n = 15): BC Sealer/Reciproc (BCRC), BC Sealer/Reciproc Blue (BCRB), AH Plus/Reciproc (AHRC), and AH Plus/Reciproc Blue (AHRB). The procedure time was measured, and an Eppendorf tube was used in each root canal to store the debris extrusion. The samples were scanned by micro-CT before and after retreatment. The apical transportation, volume of dentin, and filling material were evaluated. Results: There were no significant differences in the reduction of the volume of obturator material or dentin removal between groups (p >.05). There were also no differences in the amount of extruded material or apical transportation (p >.05). The retreatment time for the AHRC group was significantly lower than that for the other groups (p =.004). Conclusions: All tested instruments obtained similar efficacy in filling material removal procedures, although no system completely removed the filling material. Retreatment of canals filled with bioceramic BC Sealer may be more time consuming. Clinical relevance: This study reported that Reciproc and Reciproc Blue can be indicated in retreatment of severely curved root canals filled either with bioceramic or resin-based sealers. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Apoptotic epithelial cells provoke inflammation if extrusion fails • ATP from retained apoptotic cells stimulates P2Y11 receptor on the neighboring cells • Activated P2Y11 stimulates IL-8 production in the neighboring cells • IL-8 recruits neutrophils toward retained apoptotic epithelial cells Duszyc et al. report that apoptotic epithelial cells provoke inflammation if they are not eliminated by apical extrusion. This is driven by paracrine signaling, where ATP from retained apoptotic cells triggers their epithelial neighbors to produce IL-8 and thus recruit neutrophils of the innate immune system. [ABSTRACT FROM AUTHOR]

Objective: To evaluate apical extrusion during a novel erbium-doped yttrium aluminum garnet (Er:YAG) laseractivated irrigation (LAI) modality. Background data: A novel double-pulse Er:YAG modality (AutoSWEEPS) was introduced recently, replacing a single laser pulse with two micropulses that are separated by a varying time delay (which is continuously "swept" between 300 and 600 lsec). Although the proposed method demonstrated increased efficacy, no data were yet available on extrusion. Methods: The extrusion was evaluated on simulated canals (n = 6) using particle imaging velocimetry. In the first two groups, the irrigation device was a syringe coupled to either a 30-G open-ended or side-vented needle, with flow rates of 1, 2, 5, and 15 mL/min. In the second two groups, irrigant activation was performed with an Er:YAG laser, using either a super-short pulse (SSP) or AutoSWEEPS modality. The pulse energies were 5, 10, 20, 30, and 40 mJ and the frequency was 10 Hz. Results: The measured extrusion was most prominent during the open-ended needle irrigation, followed by the vented needle irrigation. Compared with the conventional needle irrigation (CNI), all the studied LAI modalities resulted in *3-20 times less extrusion. The AutoSWEEPS modality induced the smallest extrusion rate, which was always <1.5mm3/sec and was also independent of the laser energy. Conclusions: Within the limitations of the study, our results demonstrate that the SSP and AutoSWEEPS laserassisted irrigation methods exhibited less extrusion in comparison with CNI methods. [ABSTRACT FROM AUTHOR]

Introduction: During endodontic retreatment apical extrusion of debris in the form of filling materials, necrotic pulp tissues, microorganisms as well as irrigants may lead to post instrumentation pain, inflammation and impaired healing. Aim: The aim of the study was to compare the amount of debris extruded from the apex during retreatment procedures using ProTaper R (PTR; Dentsply Maillefer, Ballaigues, Switzerland) and Endostar RE Re endo rotary system (ERE; Poldent Co. Ltd., Warsaw, Poland) file systems. Materials and Methods: A total of 30 extracted mandibular premolars were prepared and obturated with gutta-percha and AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) using warm vertical compaction technique. The teeth were randomly divided into two groups of 15 each for removal of root canal filling material with PTR and ERE files. The Apically Extruded Debris (AED) was collected in preweighed eppendorf tubes. Data were analysed statistically using independent sample t-test. Significance level was established at α=0.05 Results: No significant difference (p=0.701) was found among the groups regarding the amount of AED. AED was more for PTR files as compared to ERE files while PTR files cleaned the canal walls better as compared to ERE. Conclusion: Both retreatment file systems were associated with some degree of debris extrusion from the apex. Though statistically insignificant PTR files extruded more debris than ERE files. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aim To compare the amount of apically extruded debris and of remaining filling material during the removal of root canal filling material using three rotary NiTi retreatment instruments or Hedström files. Methodology Ninety-six severely curved human molars of both jaws were selected. The root canals were prepared to size X2 (tip size 25, .06 taper) using the ProTaper Next system (Dentsply Sirona, Ballaigues, Switzerland), filled with gutta-percha and AH Plus sealer (Dentsply De Trey, Konstanz, Germany) and then randomly divided into four experimental groups ( n = 24 each) with two subgroups of maxillary and mandibular teeth each. An experimental model was used as a phantom head to simulate the upper and lower jaws. The root filling materials were removed with one of the following files using a crown-down preparation technique: I. Hedström files (H-files) ( VDW, Munich, Germany), II. R-Endo (Micro-Mega, Besançon, France), III. Reciproc ( VDW) and IV. ProTaper Universal Retreatment system ( PTU-R) (Dentsply Maillefer). Apically extruded material was collected in vials, which were weighed with a microbalance (10−5 g) before and after the retreatment. The area of residual filling material in the coronal, middle and apical root level was assessed using digital analysis. These data were analysed statistically using ANOVA and the Kruskal-Wallis test. Results Reciproc was associated with significantly less extruded debris than the H-files ( P = 0.009). No significant differences were detected amongst the four retreatment techniques concerning residual filling material ( P = 0.082). The amount of extruded debris and areas of remaining filling material were not correlated ( P = 0.901). Location of teeth in the maxilla or mandible had no impact on the amount of extruded debris within each instrument group ( P = 0.609). However, when teeth were evaluated in general irrespective of the instruments, significantly more debris was extruded in the mandibular location ( P < 0.001). Conclusions All retreatment systems were associated with apical extrusion of debris, but H-files extruded significantly more material than Reciproc. Remnants of filling material were observed in all samples with no significant differences between the four techniques. [ABSTRACT FROM AUTHOR]

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 Antæos® ( 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. [ABSTRACT FROM AUTHOR]

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 upregulation 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. [ABSTRACT FROM AUTHOR]

Objective: Sodium hypochlorite has been routinely delivered into the pulp canal via irrigation needle. The study aimed at to determine the advantage and disadvantage of apical extrusion of sodium hypochloride using monoject or hypodermic irrigation needle in root canal treatment. Materials and Methods: Eighty single rooted teeth with closed apices were used in this in vitro study to determine apical extrusion of sodium hypochlorite using the gel diffusion technique. Extracted human anterior teeth were used as study samples. Monoject (size 27G) and hypodermic (27Gx 1/2, 0.40x13mm, Terumo Needle) irrigation needle were used. The highest concentration of 5.25% hypochlorite solution was used for irrigation. To standardize the time diffusion of the dye, the gel was photographed at exactly 20 minutes after the initial irrigation with sodium hypochlorite. Results: A total of 36 out of 40 (90%) teeth in the hypodermic needle group showed positive apical extrusion compared to 14 of 40 teeth (35%) in the monoject group regardless of apical size. The discoloration of agar was clearly obtained after the sample tooth had been irrigated with sodium hypochlorite indicating the sign of apical extrusion. It is therefore; recommend that monoject irrigation needle should be used by students regardless of costs during root canal treatment in the polyclinic or dental clinic due to its safety in order to prevent sodium hypochlorite accident. Conclusion: Monoject needle showed significantly less sodium hypochlorite extrusion compared to hypodermic needle [ABSTRACT FROM AUTHOR]

Introduction: Although success of endodontic therapy has significantly improved in the last few decades due to the introduction of novel materials and techniques, failures of endodontic therapy requiring re-treatment still comprise a significant percentage of patients requiring root canal treatment. Aim: To evaluate and compare the effective removal of gutta percha and sealer, amount of apical debris extrusion and time required for gutta percha removal using various endodontic files. Materials and Methods: Total 48 extracted mandibular premolars were mounted on acrylic blocks and endodontic procedure was carried out using size 40 K file and obturated using guttapercha and zinc oxide eugenol sealer. After one month storage, samples were decoronated, mounted on screw capped vials and subjected to removal of obturated material by four instruments: H files, safe sided H files, protaper universal retreatment rotary system and ultrasonic retreatment tip, grouped as 1, 2, 3, and 4 respectively. Only 2mm of obturated material from the coronal part was removed using no. 3 Gates Glidden drill, guttapercha was softened with a drop of xylene for 2 mins for each canal and retreatment was performed. The retreatment procedure was said to be complete when no visible debris were observed on the instrument flutes. The samples split into two halves and examined under stereomicroscope, photographed, assessed using AUTOCAD software and percentage of remaining filling material in coronal, middle, apical thirds of the canal was calculated in mm2. Retreatment time was recorded in seconds and apically extruded debris was assessed by microbalance in grams for each tooth. The data was analyzed by using descriptive statistics, ANOVA and Scheffe's post hoc test through SPSS for windows (v 16.0). Results: The ultrasonic retreatment tip had less percentage of residual guttapercha/sealer, shorter mean operating time and little apical extrusion with a significant difference (p<0.05) between the other groups. Conclusion: All techniques retained guttapercha/sealer remnants within the root canal. The ultrasonic retreatment tip proved to be an efficient method of removing obturated material. It was fastest with least apical debris extrusion. [ABSTRACT FROM AUTHOR]

Aim To compare the amount of debris extruded apically during root canal retreatment using ProTaper, Mtwo and Reciproc instruments with hand H-files. Methodology In total, 60 freshly extracted human mandibular incisor teeth were used. All root canals were prepared with a Reciproc R25 file than filled with Gutta-percha and AH Plus sealer using cold lateral condensation before being assigned randomly to four groups ( n = 15 each). In group 1, root fillings were removed with the Protaper Universal retreatment system; ProTaper Universal F3 and F4 instruments were used for the final preparation. In group 2, root fillings were removed with the Mtwo retreatment system; Mtwo size 30, .06 taper, size 35, .06 taper and size 40, .06 taper files were used for the final preparation. In group 3, root fillings were removed with Reciproc R25 instruments; Reciproc R40 instruments were used for the final preparation. In group 4, the root fillings were removed with Gates Glidden burs and sizes 35, 30 and 25 H-files; for final preparation, a size 40 H-file was used. Glass vials were used for debris collection. The vials were weighed before and after Gutta-percha removal. Additionally, the times required for the retreatment procedures were recorded. Data were analysed statistically using one-way analysis of variance. Results The Reciproc system produced significantly smaller amounts of apical extruded debris than the other groups ( P < 0.05). There was no significant difference between the Mtwo, H-file and ProTaper groups. The ProTaper and Reciproc groups required significantly less time than the Mtwo and H-file groups ( P < 0.001). Conclusions Use of the reciprocating single file system resulted in the extrusion of significantly less debris compared with the full-sequence rotary NiTi instruments and hand filing. Use of the ProTaper and Reciproc instruments required less time for retreatment procedures than use of the Mtwo or H-file. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effect of photon-induced photoacoustic streaming (PIPS) technique at different power settings on extrusion of irrigating solution. Root canal preparation was performed up to a #30 file on 64 extracted single-rooted mandibular premolar teeth, which were then divided into four groups. Each group was irrigated with one of the following irrigation methods: (a) irrigation with conventional irrigation open-ended needles, (b) continuous ultrasonic irrigation, (c) 0.3 W PIPS, or (d) 0.9 W PIPS. Apical extrusion of irrigating solution was evaluated using a modified model. The net weight of the extruded irrigating solution was measured for each group, and the resulting data were analysed statistically using Kruskal-Wallis at a 95 % confidence level ( P < 0.05). Although the 0.9 W PIPS group resulted in the largest quantity of irrigation solution, the ultrasonic group was the smallest. However, the difference between these groups was not statistically significant at the 95 % level of confidence ( P > 0.05). PIPS at both 0.3 W and 0.9 W resulted similar solution extrusion to the conventional irrigation or ultrasonic irrigation. [ABSTRACT FROM AUTHOR]

Aim To compare apical extrusion of debris in canals prepared with two reciprocating file systems and two different irrigation systems. Methodology Forty single straight root canals in human mandibular pre-molars were prepared using Reciproc R40 ( REC) and WaveOne Large ( WO) instruments. Before preparation, the dimensions of a size 40 instrument from each system were measured under scanning electron microscopy ( SEM) at 80X. The teeth were randomly divided into four different groups of 10: REC and VPro EndoSafe ( REC/ VPro); WO/VPro; REC and conventional irrigation ( REC/CI); and WO/CI Eppendorf tubes containing a single tooth were weighed on an analytical balance to the nearest 0.1 mg before instrumentation. Irrigation was performed with a total volume of 8 mL of 2.5% sodium hypochlorite. After instrumentation, the teeth were removed from the Eppendorf tube and incubated at 37 °C for 15 days to evaporate the liquid. The tubes were weighed again, and the difference between the initial and final debris weights was calculated and statistically evaluated using analysis of variance (two-way anova) with a significance level of 0.05. Results No significant difference was observed between the VPro and CI irrigation systems ( P > 0.05). Apical extrusion of debris was confirmed in all samples, and extrusion was greater in the REC groups than in the WO groups ( P < 0.05). The WO file had a 20% smaller diameter at the tip (D0) than the measurement provided by the manufacturer. Conclusions All systems were associated with apical extrusion of debris. The WO system was associated with less extrusion than the REC system. The amount of extruded debris was independent of the irrigation system used and was related to the instrumentation technique. Morphological analysis of instruments using SEM revealed no correlation between the diameter provided by the manufacturer and the measured diameter for the WO Large file. [ABSTRACT FROM AUTHOR]

Aim To evaluate the apical extrusion of debris associated with several root canal preparation systems in vitro. Methodology Forty-five extracted human mandibular premolars with single canals and similar lengths were used. The root canals were instrumented using ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland), Twisted File (SybronEndo, Orange, CA, USA) or WaveOne (Dentsply Maillefer, Ballaigues, Switzerland). Debris extruded apically during instrumentation was collected into pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70 °C for 5 days. The Eppendorf tubes were weighed to obtain the final weight of the Eppendorf tubes plus extruded debris. Three consecutive weights were obtained for each tube. The groups were compared using the Kruskal-Wallis one-way analysis of variance on Ranks and Tukey's test. Results The ProTaper Next group produced the highest mean extrusion value whilst WaveOne produced less debris compared with all the other instruments ( P > 0.05). There was a significant difference between the ProTaper Next and WaveOne group ( P < 0.05). Conclusions Apically extruded debris was associated with all instrumentation techniques. The WaveOne system extruded less debris compared with the Twisted File and ProTaper Next. [ABSTRACT FROM AUTHOR]

Aim To evaluate the influence of reciprocating single-file instrumentation with different working lengths ( WL) and apical preparation sizes on apical bacterial extrusion. Methodology Sixty-eight human single-rooted pre-molars were used. Conventional access cavities were prepared, and the root canals were contaminated with an Enterococcus faecalis suspension and incubated at 37°C for 30 days. Teeth were then divided into four groups of 15 specimens each (Reciproc size 25, .08 taper and Reciproc size 40, .06 taper instruments were used at the foramen; Reciproc size 25, .08 taper and Reciproc size 40, .06 taper instruments were used 1 mm short of the foramen). Positive and negative controls consisted of four infected and four uninfected pre-molars that were instrumented according to each experimental group. Bacteria extruded from the apical foramen during instrumentation were collected into vials containing 0.9% NaCl. The microbiological samples were then incubated in a brain-heart agar medium for 24 h. The resulting bacterial titre, in colony-forming units ( CFU) per mL, was determined, and these data were analysed using a Wilcoxon matched-pairs signed rank test and a Kruskal-Wallis H-test. The level of significance was set at α = 0.05. Results No growth was observed in the negative control group. All positive controls demonstrated bacterial growth after the experimental time interval. No significant difference was found in the number of CFU amongst all experimental groups ( P = 0.95). Conclusions This study showed that the WL and the apical preparation size did not have a significant effect on bacterial extrusion when performing reciprocating instrumentation. [ABSTRACT FROM AUTHOR]

During embryonic development or under certain pathological conditions, viable but suboptimal cells are often eliminated from the cellular society through a process termed cell competition. Cell competition was originally identified in Drosophila where cells with different properties compete for survival; 'loser' cells are eliminated from tissues and consequently 'winner' cells become dominant. Recent studies have shown that cell competition also occurs in mammals. While apoptotic cell death is the major fate for losers in Drosophila, outcompeted cells show more variable phenotypes in mammals, such as cell death-independent apical extrusion and cellular senescence. Molecular mechanisms underlying these processes have been recently revealed. Especially, in epithelial tissues, normal cells sense and actively eliminate the neighbouring transformed cells via cytoskeletal proteins by the process named epithelial defence against cancer (EDAC). Here, we introduce this newly emerging research field: cell competition in mammals. [ABSTRACT FROM AUTHOR]

Aim To assess and compare the amount of extruded debris after canal preparation using ProTaper Universal and ProTaper Next files. Methodology Forty extracted mandibular premolars with single canals and of similar lengths were instrumented using the ProTaper Universal F3 or the ProTaper Next X3. The extruded debris during instrumentation was collected into pre-weighed Eppendorf tubes. The tubes were stored in an incubator for 5 days. The tubes were weighed to obtain the final dry weight of the extruded debris. The amount of apically extruded debris was calculated by subtracting the initial weight of the tube from the final weight. The distribution of the data was examined using the Shapiro-Wilks test. Continuous variables were compared with an independent-samples t-test for two groups. Results All specimens were associated with apical debris extrusion. The ProTaper Universal group produced a significantly greater amount of debris extrusion ( P < 0.001). The lowest and highest amounts of debris for PTU and PTN groups were recorded as 0.00117-0.00165 g and 0.00017-0.00067 g, respectively. Conclusion ProTaper Next files was associated with significantly less extruded apical debris when compared to ProTaper Universal files. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to evaluate the apical extrusion of debris by the two reciprocating single-file systems: WaveOne and Reciproc. Conventional multi-file rotary system was used as a reference for comparison. The hypotheses tested were (i) the reciprocating single-file systems extrude more than conventional multi-file rotary system and (ii) the reciprocating single-file systems extrude similar amounts of dentin debris. Materials and methods: After solid selection criteria, 80 mesial roots of lower molars were included in the present study. The use of four different instrumentation techniques resulted in four groups ( n = 20): G1 (hand-file technique), G2 (ProTaper), G3 (WaveOne), and G4 (Reciproc). The apparatus used to evaluate the collection of apically extruded debris was typical double-chamber collector. Statistical analysis was performed for multiple comparisons. Results: No significant difference was found in the amount of the debris extruded between the two reciprocating systems. In contrast, conventional multi-file rotary system group extruded significantly more debris than both reciprocating groups. Hand instrumentation group extruded significantly more debris than all other groups. Conclusion: The present results yielded favorable input for both reciprocation single-file systems, inasmuch as they showed an improved control of apically extruded debris. Clinical relevance: Apical extrusion of debris has been studied extensively because of its clinical relevance, particularly since it may cause flare-ups, originated by the introduction of bacteria, pulpal tissue, and irrigating solutions into the periapical tissues. [ABSTRACT FROM AUTHOR]

At the initial stage of carcinogenesis, a mutation occurs in a single cell within a normal epithelial layer. We have previously shown that RasV12-transformed cells are apically extruded from the epithelium when surrounded by normal cells. However, the molecular mechanisms underlying this phenomenon remain elusive. Here, we demonstrate that Cav-1-containing microdomains and EPLIN (also known as LIMA1) are accumulated in RasV12-transformed cells that are surrounded by normal cells. We also show that knockdown of Cav-1 or EPLIN suppresses apical extrusion of RasV12-transformed cells, suggesting their positive role in the elimination of transformed cells from epithelia. EPLIN functions upstream of Cav-1 and affects its enrichment in RasV12-transformed cells that are surrounded by normal cells. Furthermore, EPLIN regulates non-cell-autonomous activation of myosin-II and protein kinase A (PKA) in RasV12- transformed cells. In addition, EPLIN substantially affects the accumulation of filamin A, a vital player in epithelial defense against cancer (EDAC), in the neighboring normal cells, and vice versa. These results indicate that EPLIN is a crucial regulator of the interaction between normal and transformed epithelial cells. [ABSTRACT FROM AUTHOR]

Aim. Assessment of apical extrusion during root canal shaping using 3 manual techniques, such as apical box and step-back preparation by reaming or fi ling. Material and methods. Three groups of inferior incisors, each of them having 20 teeth, were instrumented by 3 different root canal techniques of manual shaping: apical box and step-back associated with reaming or filing. KFlexoreamers were used in apical box and reaming canal preparation, respectively K-Flexofi les for circumferential filing. The apical extruded material was collected and weighed. Results and discussion. All the investigated techniques of canal shaping produced apical extrusion. The maximal values were observed in circumferential fi ling and the minimal in reaming. Apical box registered intermediate values. The apical extrusion was pretty similar in both reaming methods because the mean values were inferior to fi ling mean value to an extent of 38% in step-back and 35,5% in apical box. [ABSTRACT FROM AUTHOR]

Aim To evaluate ex vivo, apical bacterial extrusion associated with two reciprocating single-file systems (WaveOne and Reciproc) compared with a conventional multifile rotary system (BioRace). Methodology Forty-five human single-rooted mandibular incisors were used. Endodontic access cavities were prepared, and root canals were contaminated with an Enterococcus faecalis suspension. Following incubation at 37 °C for thirty days, the contaminated teeth were divided into three groups of 15 specimens each (G1 - Reciproc, G2 - WaveOne and G3 - BioRace). Positive and negative controls consisted of 5 infected teeth and 3 uninfected incisors that were instrumented with one of the tested NiTi systems, respectively. Bacteria extruded from the apical foramen during instrumentation were collected into vials containing 0.9% NaCl. The microbiological samples were taken from the vials and incubated in brain heart agar medium for 24 h. The resulting bacterial titre, in colony-forming units ( CFU) per mL, was determined, and these data were analysed by Wilcoxon matched-pairs signed rank test and Kruskal-Wallis H-test. The level of significance was set at α = 0.05. Results No significant difference was found in the number of CFU between the two reciprocating systems ( P = 0.41). The conventional multifile rotary system group was associated with significantly higher CFU than both of the two reciprocating groups ( P = 0.01). Conclusions All instrumentation systems extruded bacteria beyond the foramen. However, both reciprocating single-file systems extruded fewer bacteria apically than the conventional multifile rotary system. [ABSTRACT FROM AUTHOR]

Aim To evaluate (i) the effect of irrigant flow rate, needle type, needle insertion depth and apical constriction diameter and (ii) the effect of ultrasonic, sonic and manual dynamic agitation on irrigant extrusion using a recently introduced method. Methodology Thirty-two human teeth with a straight root canal were prepared to size 35, 0.06 taper and assigned to group A or B. The apical constriction diameter was 0.15-0.25 mm. Specimens were mounted on a plastic vial filled with distilled water to simulate a periapical lesion. A point-conductivity probe was used to determine the volume of irrigant extruded into the vial. Within group A, NaOCl was delivered at 0.14 or 0.26 mL s−1 by an open-ended or a closed-ended needle at 1 or 3 mm short of working length (WL). In group B, NaOCl was agitated at high or low power either by an ultrasonically or sonically oscillating instrument inserted at 1 or 3 mm short of WL or by manual push-pull strokes of a gutta-percha cone. Results were analysed by repeated-measures anovas, at 0.05 significance. Results An increase in the flow rate resulted in increased extrusion ( P < 0.001). The open-ended needle extruded significantly more irrigant than the closed-ended ( P < 0.001). Extrusion decreased as needles moved away from WL ( P < 0.001). The effect of apical constriction diameter was not significant ( P > 0.454). Manual dynamic agitation extruded significantly more irrigant than sonic and ultrasonic agitation ( P < 0.001). Conclusions Irrigant flow rate, needle type and insertion depth and agitation technique had a significant effect on extrusion. [ABSTRACT FROM AUTHOR]

Extrusion of intracanal debris as well as irrigants is a common occurrence during root canal treatment, and no instrument or technique has thoroughly solved this problem. Because flare-ups may arise with any irritation directed towards periapical tissues, a shaping or irrigation technique should minimize the risk of apical extrusion, even though it may not be prevented. There has been a rapid evolution of root canal instruments and irrigation systems through the last decade, and many have been assessed for their debris extrusion potential. The purpose of this review was to identify publications regarding the evaluation of debris, bacteria and irrigant extrusion during root canal treatment. A Pub Med, Ovid and MEDLINE search was conducted using the keywords 'apical extrusion', 'debris extrusion' and 'endodontic treatment'. The literature search extended over a period of more than 30 years up to 2012. Content of the review was limited to apical extrusion of debris and irrigants, extrusion of liquid by irrigation methods and bacterial extrusion. Issues relevant to apical extrusion were obtained by further search in the reference sections of the retrieved articles. The review provides an update on the current status of apical extrusion. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of the present study was to test the hypothesis that apical extrusion of the irrigant occurs during laser-driven irrigation in vivo. Materials and methods: Three hundred human root canals, in 181 patients, were divided into two groups: the no lesion group ( n = 140) and the lesion group ( n = 160). All the root canals were enlarged using a crown down technique up to size 30–80 K-files, depending on the original condition of the root canal. For the final irrigation, the teeth were irrigated with a mixture of radiopaque contrast medium and NaOCl in solution. The solution was activated for 60 s in teeth with one canal or two canals and for 120 s in teeth with three or four canals. Results: Radiopaque contrast medium was absent from the periapical tissues of all samples. Conclusions: No contrast medium was observed radiographically in the periapical tissues. The hypothesis that apical extrusion of root canal irrigants occur during laser cavitation was rejected Clinical relevance: It appears that the power of the laser used at 1 W for 1–2 min can drive the irrigation solution to the tip of the canal without harming the apical tissues. [ABSTRACT FROM AUTHOR]

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 Revo S 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. [ABSTRACT FROM AUTHOR]

The aim of the present study was to conduct a systematic review and critical analysis of published data on irrigant extrusion to identify factors causing, affecting or predisposing to irrigant extrusion during root canal irrigation of human mature permanent teeth. An electronic search was conducted in Cochrane Library, LILACS, PubMed, Sci ELO, Scopus and Web of Knowledge using a combination of the terms 'irrigant', 'rinse', 'extrusion', 'injection', 'complication', 'accident', 'iatrogenic', 'root canal', 'tooth' and 'endodontic'. Additional studies were identified by hand-searching of six endodontic journals and the relevant chapters of four endodontic textbooks, resulting in a total of 460 titles. No language restriction was imposed. After applying screening and strict eligibility criteria by two independent reviewers, 40 case reports and 10 ex vivo studies were included in the review. A lack of clinical studies focusing on irrigant extrusion during root canal irrigation was evident. The reviewed case reports focused mainly on the clinical manifestations and management of the accidents and did not provide adequate details on the possible factors that may influence irrigant extrusion. The data from the included e x vivo studies were inconclusive due to major methodological limitations, such as not simulating the presence of periapical tissues and not assessing the validity of irrigant detection methods. The extensive variability in the protocols employed hindered quantitative synthesis. The choice of factors investigated in ex vivo studies seems not to have been driven by the available clinical evidence. These issues need to be addressed in future studies. [ABSTRACT FROM AUTHOR]

Aim (i) To introduce a new method of quantifying extruded irrigant during root canal irrigation ex vivo. (ii) to evaluate the effect of periapical tissue simulation and pressure equalization and (iii) to determine the effect of needle type, apical preparation size and apical constriction diameter on irrigant extrusion. Methodology Sixteen human single-rooted teeth were sequentially prepared to sizes 25-45, 0.06 taper and mounted on a plastic vial simulating a periapical lesion. The apical constriction diameter was standardized to 0.15-0.35 mm. The vial was filled with distilled water or air and was either open to the environment or closed. A point-conductivity probe was used to determine the volume of extruded irrigant into the vial. Na OCl was delivered by an open-ended or a closed-ended needle at 3 mm short of working length. Results were analysed by two 3-way repeated-measures ANOVAs Results The open-ended needle extruded significantly more irrigant than the closed-ended in the majority of cases ( P < 0.002). An increase in the apical size was related to decreased irrigant extrusion ( P < 0.024). The effect of constriction diameter was not significant. The water-closed and water-open methods were related to less extrusion than the air-closed and air-open methods, respectively ( P < 0.005). Open systems (water-open, air-open) allowed extrusion of larger amounts of irrigant than corresponding closed systems (water-closed, air-closed) ( P < 0.005). Conclusions The conductivity probe is a reliable method for real-time quantification of irrigant extrusion ex vivo. Not simulating tissue resistance in ex vivo experiments may lead to significant overestimation of irrigant extrusion. [ABSTRACT FROM AUTHOR]

Aim To evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal instrumentation using a manual technique and three engine-driven techniques utilizing nickel–titanium instruments (K3, RaCe, and FlexMaster). Methodology Seventy extracted human mandibular premolar teeth with similar dimensions were used. Access cavities were prepared and root canals were then contaminated with a suspension of Enterococcus faecalis and then dried. The contaminated roots were divided into four experimental groups of 15 teeth each and one control group of 10 teeth. G1. RaCe group: the root canals were instrumented using RaCe instruments. G2. K3 group: the root canals were instrumented using K3 instruments. G3. FlexMaster group: the root canals were instrumented using FlexMaster instruments. G4. Manual technique group: the root canals were instrumented using K-type stainless steel instruments. G5. Control group: no instrumentation was attempted. Bacteria extruded from the apical foramen during instrumentation were collected into vials. The resultant microbiological samples were removed from the vials and then incubated in culture media for 24 h. The number of colony-forming units (CFU) was determined for each sample. The data obtained were analysed using the Kruskal–Wallis one-way analysis of variance and Mann–Whitney U-tests, with α = 0.05 as the level for statistical significance. Results There was a significant difference between experimental-control and engine-driven-manual technique groups ( P < 0.05). The manual technique was associated with the greatest extrusion of microorganism. Conclusions All instrumentation techniques extruded intracanal bacteria apically. No significant difference was found in the number of CFU among the engine-driven techniques; manual techniques extruded significantly more microorganisms. [ABSTRACT FROM AUTHOR]

Aim To investigate the efficiency of a hydrodynamic irrigation system compared with conventional cleansing techniques in root canals. Methodology Forty-five freshly extracted single-rooted teeth were de-coronated and their root canals were enlarged to size 30 at the apex. The teeth were randomly divided into three groups ( n = 15) for the final rinsing sequence using 2% NaOCl plus acid fuchsin: group I: static application of irrigant, 3 min; group II: flushing with a syringe; 5-mL NaOCl, 1 min; group III: RinsEndo®-system; 5-mL NaOCl, 50 s. Apical extrusion was documented photographically. The roots were sectioned at 2, 4, 6 and 8 mm from their apices and the penetration depths of dye into dentine measured, using a stereomicroscope. Wilcoxon's test and Pearson's chi-squared test were employed to prove statistic relevance. Results Greater dye penetration depth into the dentinal tubules was achieved when employing hydrodynamic rinsing procedures. Using this technique, 23% of the specimens were penetrated for more than 50% of their dentine thickness, whereas the results for flushing with a syringe were 12% (static application, 7%). No penetration of dentine occurred in 63% of specimens with static application, 39% flushing with a syringe and 15% using the hydrodynamic system ( P < 0.05 Pearson's chi-squared test). Apical extrusion occurred more frequently after hydrodynamic rinsing (extruded specimens: RinsEndo® = 80%; static application/flushing with a syringe = 13%; P < 0.05 Pearson's chi-squared test). Conclusions Hydrodynamic rinsing demonstrated an improvement over conventional methods in terms of dentine penetration of a dye marker. A higher risk of apical extrusion with the RinsEndo®-system was evident. [ABSTRACT FROM AUTHOR]

Aim To evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal instrumentation using the two engine-driven techniques utilizing nickel-titanium instruments (ProTaper and System GT). Methodology Forty extracted single-rooted human mandibular premolar teeth were used. Access cavities were prepared and root canals were then contaminated with a suspension of Enterococcus faecalis and dried. The contaminated roots were divided into two experimental groups of 15 teeth each and one control group of 10 teeth. Group 1, ProTaper group: the root canals were instrumented using ProTaper instruments. Group 2, System GT group: the root canals were instrumented using System GT instruments. Group 3, control group: no instrumentation was attempted. Bacteria extruded from the apical foramen during instrumentation were collected into vials. The microbiological samples from the vials were incubated in culture media for 24 h. Colonies of bacteria were counted and the results were given as number of colony-forming units. The data obtained were analysed using the Kruskal–Wallis one-way analysis of variance and Mann–Whitney U-tests, with α = 0.05 as the level for statistical significance. Results There was no significant difference as to the number of extruded bacteria between the ProTaper and System GT engine-driven systems ( P > 0.05). Conclusions Both engine-driven nickel-titanium systems extruded bacteria through the apical foramen. [ABSTRACT FROM AUTHOR]

Abstract Aim To evaluate the weight of debris and irrigant volume extruded apically from extracted teeth in vitro after endodontic instrumentation using the balanced force technique, a hybrid hand instrumentation technique, and three engine-driven techniques utilizing nickel–titanium instruments (ProFile .04, Quantec 2000 and Pow-R). Methodology Five groups of 20 extracted human teeth with single canals were instrumented using one or other of five techniques: balanced force, hybrid, Quantec 2000, ProFile .04, or Pow-R. Debris extruded from the apical foramen during instrumentation were collected into preweighed 1.5 mL tubes. Following instrumentation, the volume of extruded irrigant fluid was determined by visual comparison to control centrifuge tubes filled with 0.25 mL increments of distilled water. The weight of dry extruded dentine debris was also established. Results Overall, the engine-driven techniques extruded less debris than the manual ones. However, there was no statistical difference between the balanced force technique and the engine-driven methods. The volume of irrigant extruded through the apex was directly associated with the weight of extruded debris, except within the ProFile group. The hybrid technique was associated with the greatest extrusion of both debris and irrigant. Conclusions Overall, the engine-driven nickel–titanium systems were associated with less apical extrusion. [ABSTRACT FROM AUTHOR]

The aim of this in vitro study was to assess the sealability of a recently introduced thermoplasticized gutta-percha technique (Trifecta, Hygenic Corp., OH, USA) in the presence or absence of a smear layer. A total of 100 teeth with single straight root canals were included in the study. The teeth were decoronated and the canals prepared with a modified double-flared technique under constant irrigation with 2.5% sodium hypochlorite solution. The apical matrix was prepared to size 40 and apical patency subsequently confirmed with a size 10 file. Four teeth were discarded for technical reasons and the remaining 96 allocated randomly into two groups of 44 teeth and a group of eight teeth which acted as controls. Canals in group 1 were obturated randomly with either cold lateral condensation of gutta-percha or with the Trifecta technique. Canals in Group 2 were rinsed with 17% REDTA to remove the smear layer and then obturated with latera, condensation or the Trifecta technique. All teeth were suspended in India ink for 9 days, demineralized, and rendered transparent prior to the assessment of apical linear dye penetration. Apical extrusion of sealer and gutta-percha occurred commonly but there was no significant difference between the four obturation groups. However, overall, there was significantly more extrusion of sealer with the Trifecta technique compared with lateral condensation (P<0.05). The majority of canals (79 out of 88) had no evidence of apical leakage and there was no significant difference between the groups. The prevalence of sealer and gutta-percha penetration into the dentinal tubules was significantly different between the four obturation techniques (P<0.01) and significantly more common in the absence of the smear layer (P<0.001). Under the conditions of this study, the Trifecta technique proved a satisfactory alternative to lateral condensation. Removal of the smear layer did not enhance sealability despite increasing the proportion of specimens with dentinal penetration of sealer and gutta-percha. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Contractility in apoptotic epithelial cells stimulates RhoA in their neighbors • Apoptotic contractility is detected by E-cadherin-based mechanotransduction • Mechanotransduction requires priming by sphingosine-1-phosphate (S1P) signaling • Mechanotransduction and S1P signaling thus collaborate for apoptotic extrusion Epithelia eliminate apoptotic cells by apical extrusion. Duszyc et al. show that this reflects an E-cadherin-based mechanotransduction pathway that is primed by S1P. Mechanotransduction activates RhoA in the neighbor cells in response to contractility in the apoptotic cells to drive extrusion and preserve tissue integrity. [ABSTRACT FROM AUTHOR]

At the initial stage of carcinogenesis, transformation occurs in a single cell within an epithelial sheet. However, it remains unknown what happens at the boundary between normal and transformed cells. Using Madin-Darby canine kidney (MDCK) cells transformed with temperature-sensitive v-Src, we have examined the interface between normal and Src-transformed epithelial cells. We show that Src-transformed cells are apically extruded when surrounded by normal cells, but not when Src cells alone are cultured, suggesting that apical extrusion occurs in a cell-context-dependent manner. We also observe apical extrusion of Src-transformed cells in the enveloping layer of zebrafish gastrula embryos. When Src-transformed MDCK cells are surrounded by normal MDCK cells, myosin-II and focal adhesion kinase (FAK) are activated in Src cells, which further activate downstream mitogen-activated protein kinase (MAPK). Importantly, activation of these signalling pathways depends on the presence of surrounding normal cells and plays a crucial role in apical extrusion of Src cells. Collectively, these results indicate that interaction with surrounding normal epithelial cells influences the signalling pathways and behaviour of Src-transformed cells. [ABSTRACT FROM AUTHOR]