New nanostructure perovskite-based light-emitting diode with superior light extraction efficiency enhancement.

The external quantum efficiency (EQE) of a perovskite-based light-emitting diode (PELED) is a key indicator, comprising the internal quantum efficiency (IQE) and light extraction efficiency (LEE). Currently, enhancing EQE faces a major challenge in optimizing LEE. This study introduces an innovative structure to boost LEE, exploring various influencing parameters. The transition from a planar to a domical architecture leverages factors like the waveguiding effect, resulting in a remarkable tenfold increase in LEE, from 6 to 59%. Additionally, investigations into factors affecting LEE, such as altering dipole orientation, material-substrate contact angle, and layer thickness, reveal the potential for further improvement. The optimized structure attains an impressive LEE value of 74%.

The Effect of Low-Frequency Pulsed Electromagnetic Fields on the Differentiation of Permanent Dental Pulp Stem Cells into Odontoblasts.

Introduction: Exposure to pulsed electromagnetic field (PEMF) has been revealed to affect the differentiation and proliferation of human mesenchymal stem cells derived from dental pulp multipotent stromal stem cells (DP-MSCs). This study aimed to investigate the differentiation effect of electromagnetic fields (EMFs) on the DP-MSC. Materials and Methods: PEMF was produced by a system comprising a multi-meter autotransformer, solenoid coils, and teslameter. This study included 10 groups of DP-MSCs which underwent different electromagnetic radiation time and beam intensity. Three samples tested for each group. The effect of PEMF with the intensity of 0.5 and 1 mT (mili Tesla) and 50 Hz on the proliferation rate of DP-MSC was evaluated at 20 and 40 minutes per day for seven days. MTT assay was applied to determine the growth and proliferation of DP-MSC. Gene expression of DMP1 for differentiation of DPSCs to odontoblasts was confirmed by Real Time PCR., ANOVA statistical analysis and Kruskal-Wallis test were used to analyze the data. Results: The survival in all exposure groups was significantly higher than that in control except in the group of 40 minutes, 1 mT (P<0.05). In 20 minutes, 0.5 mT exposure, the survival intensity is significantly more than others (P<0.05). In general, the intensity of survival was recorded, 20, 0.5 mT≥20, 1 mT≥40, 0.5 mT≥40, 1 mT respectively. Therefore, according to the obtained results, ELF-EMF increases the survival of cells except for one case (40 minutes, 1 mT), even though the effective underlying mechanisms in this process are still unclear. Conclusions: The results obtained promise that in the future, by placing an important part of the pulp next to the electromagnetic field, the lost part of the pulp can be reconstructed and the dentin barrier can be created.

Postoperative pain after endodontic treatment of mandibular molars with two different instrumentation techniques: A randomized clinical trial.

Background: This study compared postoperative pain after endodontic treatment of mandibular molars with asymptomatic irreversible pulpitis with the RaCe rotary system and the crown-down versus the step-down technique. Materials and Methods: In this randomized clinical trial, 70 mandibular 1st and 2nd molars with asymptomatic irreversible pulpitis and normal periradicular state were randomly assigned to two groups for single-visit endodontic treatment with RaCe rotary system and the crown-down and the step-down technique (n = 35). Postoperative pain was assessed at 6, 12, 24, 48, 72, and 168 h postoperatively, using a Visual Analog Scale. Data were analyzed using SPSS 17 by repeated measures ANOVA, Chi-square test, independent sample t-test, and lLeast sSignificant Ddifference test. P < 0.05 was considered statistically significant. Results: The two groups were not significantly different regarding the pain scores at any time point (P > 0.05). Within-group comparisons showed a significant reduction in pain score over time, starting from 12 to 168 h, postoperatively (P < 0.05). Conclusion: The crown-down and step-down techniques had no significant difference regarding postoperative pain after endodontic treatment of mandibular molars with asymptomatic irreversible pulpitis with the RaCe rotary system.

CoFe2O4@SiO2-NH2@MOF-5 magnetic nanocatalyst for the synthesis of biologically active quinazoline derivatives.

Metal-organic frameworks (MOFs) offered excellent catalytic activity due to their superior porosity, and high densities of catalytic sites in remarkable specific surfaces. In this research, we prepared a magnetic nanocomposite based on MOF-5 which is one of the prominent and practical structures that have been reported in many applications, and investigated the advantages of it as a catalyst. The multi-functional catalyst was prepared in five steps including (1) preparation of cobalt ferrite nanoparticles (CoFe2O4), (2) surface modification of cobalt ferrite using tetraethyl orthosilicate, (3) surface functionalization using 3-aminopropyl triethoxysilane, (4) preparation of MOF-5, (5) preparation of CoFe2O4@SiO2-NH2@MOF-5 nanocomposite. The resulting catalyst was evaluated by FTIR, FESEM, EDX, XRD, and VSM analyses. The CoFe2O4@SiO2-NH2@MOF-5 nanocomposite was applied as a catalyst for the quinazoline derivatives' synthesis. Various products were prepared with significant yields (90-98%) in short reaction times (20-60 min) without difficult work-up. In addition, the magnetic behavior of the catalyst allows it to be collected and recycled by a magnet and applied for six consecutive cycles without significantly reducing its efficiency. Quinazoline derivatives showed significant biological activities so their antioxidant activity was between 23.7% and 88.9% and their antimicrobial activity was in contradiction of E. coli, S. enterica, L. monocytogenes, S. aureus, and E. faecalis.

Concentrated Growth Factors Combined with Lipopolysaccharide Stimulate the In Vitro Regenerative and Osteogenic Activities of Human Dental Pulp Stem Cells by Balancing Inflammation.

Aim: We investigated the long-term effects of exposure to concentrated growth factors (CGFs) on the regenerative properties of dental pulp stem cells (DPSCs) in the presence and absence of lipopolysaccharide (LPS) as a proinflammatory agent. Methods: DPSCs were cultured with CGF at different concentrations of LPS (0.1, 1, and 10 µg/ml) for 21 days. Then, using MTT and scratch assays, the cell viability and migration were examined. Osteogenic stimulation was evaluated by alkaline phosphatase (ALP) staining and Sirius Red staining, which determined the ALP activity and collagen levels, respectively. The expression levels of osteogenic markers were quantified using the qRT-PCR method. One-way analysis of variance (ANOVA) and Tukey's HSD test were used to analyze differences between groups. Results: Long-term treatment of DPSCs with CGFs reduced LPS-induced cell death. Moreover, CGF and LPS (1 µg/ml), either in combination or alone, improved the DPSC migratory ability and caused a significant increase in osteogenic stimulation through the upregulation of collagen levels and ALP activity. Additionally, CGFs significantly upregulated RUNX2, DSPP, OCN, and OPN mRNA levels (as osteogenic markers), while LPS (1 µg/ml) only significantly increased OCN overexpression. Conclusion: Our findings are evidence that CGF could be a promising agent to induce dentin-pulp complex healing in long-term chronic inflammation.

A vector-agent approach to (spatiotemporal) movement modelling and reasoning.

Modelling a complex system of autonomous individuals moving through space and time essentially entails understanding the (heterogeneous) spatiotemporal context, interactions with other individuals, their internal states and making any underlying causal interrelationships explicit, a task for which agents (including vector-agents) are specifically well-suited. Building on a conceptual model of agent space-time and reasoning behaviour, a design guideline for an implemented vector-agent model is presented. The movement of football players was chosen as it is appropriately constrained in space, time and individual actions. Sensitivity-variability analysis was applied to measure the performance of different configurations of system components on the emergent movement patterns. The model output varied more when the condition of the contextual actors (players' role-areas) was manipulated. The current study shows how agent-based modelling can contribute to our understanding of movement and how causally relevant evidence can be produced, illustrated through a spatiotemporally constrained football case-study.

Comparison of the fracture resistance of the teeth prepared with ProTaper Universal, ProTaper Next, and ProTaper Gold rotary files.

OBJECTIVES: Root canal preparation can lead to cracks on the roots by creating stresses on the root canal walls, which decreases the fracture resistance of the tooth. The present study compared the fracture resistance of the teeth prepared by the ProTaper Universal (PTU), ProTaper Next (PTN), and ProTaper Gold (PTG) rotary file systems. MATERIALS AND METHODS: Fifty-six single-canal premolar teeth were sectioned 14 mm from the root apex. The roots were standardized based on the buccolingual and mesiodistal diameter and randomly assigned to three experimental (n = 14) and one control group (n = 14). The teeth in three experimental groups were instrumented with PTU, PTN, and PTG rotary files. The roots in the control group were not instrumented. A vertical force was applied to each root in a universal testing machine until the root fractured. The data were statistically analyzed by one-way analysis of variance. RESULTS: There was no significant difference in the fracture resistance of the teeth between the control, PTU, PTN, and PTG groups (p = .115). CONCLUSIONS: Root canal preparation with ProTaper files manufactured with conventional NiTi (PTU) and heat-treated alloys (PTN and PTG) did not affect the fracture resistance of teeth.

Effect of different intracanal medicaments on the fracture resistance of the human root.

Background: The effect of different intracanal medicaments on root fracture resistance has not been thoroughly investigated in the short and long term. To assess the effect of calcium hydroxide (CH), CH combined with Chlorhexidine (CHX), double antibiotic paste (DAP), and simvastatin as intracanal medicaments on the fracture resistance of the human root. One hundred and twenty single-rooted mandibular premolars which were extracted for periodontal reasons were collected for this in vitro study. Materials and Methods: This was an in vitro study. All teeth were decoronated. Root canals were prepared by the Pro taper system, and %2.5 NaOCl was used for irrigation. The smear layer was removed using %5.25 NaOCl and 17% ethylenediaminetetraacetic acid each for 3 min. The samples were randomly divided into five groups based on the medicament: (1) CH (2) CH + CHX (3) Simvastatin (4) DAP (5) Control group. All specimens in each group were incubated for 1 week (Subgroup A) and 1 month (Subgroup B). Then, medicaments were removed and filled with gutta-percha and AH26 sealer. All samples were tested for fracture resistance. The data were statistically evaluated with the SPSS software 17. ANOVA and Mann-Whitney U and Wilcoxon tests were used for the analysis of the data. P = 0.05 was considered statistically significant. Results: Although CH and CH + CHX increased the fracture resistance in a 1-week period, there was no significant difference between the groups after 1 month. Conclusion: Under the limitations of this study, CH and CH + CHX, DAP and simvastatin do not have a negative effect on root fracture resistance when used as intracanal medicaments for <1 month.

Antimicrobial effects of different concentrations of simvastatin versus triple antibiotic paste on Enterococcus faecalis biofilms at different stages of development.

Background. This study assessed the antimicrobial effects of different concentrations of simvastatin versus triple antibiotic paste (TAP) on Enterococcus faecalis biofilms at different stages of development. Methods. In this in vitro study, 70 human single-rooted mature premolars were decoronated, instrumented, and autoclave-sterilized. Next, an E. faecalis suspension was prepared and inoculated into the canals to obtain 4- and 6-week biofilms. After ensuring biofilm formation, the samples in each group were randomly assigned to 5 subgroups (n=12): 1 mg/mL TAP, 10 mg/ mL TAP, 1 mg/mL simvastatin, 10 mg/mL simvastatin, and positive control (phosphate-buffered saline solution). The medicaments were applied in the canals, and the teeth were incubated for one week. Dentin samples were collected by a rotary file, cultured, and the number of E. faecalis colonies was counted. The Kruskal-Wallis, Mann-Whitney U, and Wilcoxon tests were used for data analysis (α=0.05). Results. There were significant differences in colony counts between the two concentrations of TAP and the control group against both 4- and 6-week biofilms (P<0.05). The antibacterial effect of 10 mg/mL TAP and simvastatin was stronger than that of 1 mg/mL concentration against the 4- and 6-week E. faecalis biofilms (P<0.05). Furthermore, 10 mg/mL TAP and simvastatin were more effective against the 4-week biofilms than the 6-week biofilms (P<0.05). Conclusion. According to the present results and since biofilms may remain viable in the root canal system for weeks to months, applying 10 mg/mL TAP and simvastatin might be more effective.

Effect of the of Zeolite Containing Silver-Zinc Nanoparticles on the Push out Bond Strength of Mineral Trioxide Aggregate in Simulated Furcation Perforation.

STATEMENT OF THE PROBLEM: Recently, zeolite has been regarded to improve the properties of dental materials such as mineral trioxide aggregate (MTA). PURPOSE: The aim of the present study was to evaluate the effect of incorporating zeolite/silver/zinc (Ze/Ag/Zn) composite at 2 wt% to MTA powder on the push-out bond strength in simulated furcation perforations. MATERIALS AND METHOD: Furcal perforations, measuring 1.3 mm in diameter and 2 mm in height, were simulated in 40 human mandibular first molars. The samples were allocated to two groups (n=20) based on the material used for the repair of perforations. In the group 1, MTA and in the group 2, MTA plus Ze/Ag/Zn (2%) was used. The samples were incubated at 37°C for 1 week. Then the universal testing machine was employed to measure bond strength. The resistance of materials to dislodgment was recorded in MPa. Data were analyzed using t-test. Statistical significance was set at p< 0.05. RESULTS: The push-out bond strength in the group 1 (6.40±1.98 MPa) was significantly higher than that in the group 2 (2.1±0.6 MPa) with p= 0.001. CONCLUSION: Under the limitations of the present study, it can be concluded that incorporation of Ze/Ag/Zn at 2 wt% to MTA powder had a negative effect on the push-out bond strength.

In vitro induction of odontogenic activity of human dental pulp stem cells by white Portland cement enriched with zirconium oxide and zinc oxide components.

Background . The aim of this in vitro study was to investigate the effect of zinc oxide (ZnO) and zirconium oxide (ZrO2) microparticles (MPs) and nanoparticles (NPs) in combination with white Portland cement (WPC) on odontogenic capacity of human dental pulp stem cells over a period of 21 days. Methods . Synthesized ZnO and ZrO2 particles were characterized using scanning electron microscopy and transmission electron microscopy. The viability of human dental pulp stem cells was measured by a 3-(4,5-dimethylthiazolyl-2-yl)-2,5- diphenyltetrazolium bromide assay at 7-, 14- and 21-day intervals after seeding on WPC disks enriched with ZnO and ZrO2 MPs and NPs. Odontogenic potential of ZnO and ZrO2 particles in combination with WPC was investigated by alkaline phosphatase (ALP) activity and ionized calcium level of supernatant culture media at different time intervals. Data were analyzed using one-way ANOVA and post hoc Tukey tests. Results . All the materials exhibited cell viability over a 21-day period, except for WPC with ZnO NPs on day 7, although it was not statistically significant (P>0.05). The ALP activity and ionized calcium level increased in all the groups compared to the control group (P<0.05). ZnO NPs had superior effect on odontogenic activity and calcium ion release compared to ZnO MPs (P=0.046). There was no significant difference between ZrO2 MPs and NPs in odontogenic activity (P>0.05). Conclusion . WPC enriched with ZnO and ZrO2 increased ALP activity and calcium ion release of human dental pulp stem cells over a period of 21 days in vitro.

Success Rate of 3 Injection Methods with Articaine for Mandibular First Molars with Symptomatic Irreversible Pulpitis: A CONSORT Randomized Double-blind Clinical Trial.

INTRODUCTION: Previous studies have reported that it is difficult to obtain proper anesthesia in mandibular molars with symptomatic irreversible pulpitis, and supplemental injections are usually unavoidable. The aim of the present study was to determine the anesthetic efficacy of articaine in mandibular first molars with symptomatic irreversible pulpitis with 3 injection methods: an inferior alveolar nerve block (IANB), an IANB with an intraligamentary injection, and an IANB with buccal infiltration before initiating the endodontic treatment. METHODS: Ninety-six patients (54 women and 42 men) with a diagnosis of symptomatic irreversible pulpitis in mandibular first molars were selected and randomly assigned into 3 groups (n = 32) according to the injection method as follows: group 1, a conventional IANB injection; group 2, an IANB injection, and after profound lip numbness after the IANB (after 15 minutes), buccal infiltration was administered; and group 3, an IANB injection, and after profound lip numbness after the IANB (after 15 minutes), an intraligamentary injection was performed, and after 20 minutes from the IANB, the endodontic treatment was initiated. The anesthetic solution was articaine 4% with 1:100,000 epinephrine. Success was defined as no or mild pain on the basis of the visual analog scale recording upon access cavity preparation or initial instrumentation. Data were statistically analyzed using the chi-square and Mann-Whitney U tests, and P < .05 was set as significant. RESULTS: The success rate for IANBs with an intraligamentary injection was 75%, and for IANBs with a buccal injection, it was 65.6%. For IANBs alone, the success rate was 28.1%. CONCLUSIONS: Considering the limitations of the present study, in can be concluded that the success rate of IANBs increased with intraligamentary injections and buccal infiltrations with articaine that were performed before initiating treatment. Also, none of the injection methods showed complete success in anesthesia in all patients.

Effect of the Bone Graft on the Surface Microhardness of Endodontic Biomaterials.

INTRODUCTION: During periapical surgery, using of bone products in large endodontic lesions, is a treatment option that could affect the properties of the retro-filling endodontic material. The aim of present study was to evaluate the effect of Osteon II bone powder on the surface microhardness of calcium-enriched mixture (CEM) and mineral trioxide aggregate (MTA). METHODS AND MATERIALS: Each material was mixed and carried into 40 sterile custom-made plastic cylinders. Half of the samples in each group were exposed to Osteon II. All cylinders were submerged in simulated tissue fluid and incubated at 37°C and 100% relative humidity for 7 days. Surface microhardness values of each study group was attained using Vickers microhardness test. The data were analyzed statistically using two-way ANOVA and independent t-test at a significance level of 0.05. RESULTS: The highest and lowest microhardness values were recorded in the MTA/without Osteon and MTA/with Osteon groups, respectively. Irrespective of the presence or absence of bone powder, the overall microhardness of CEM cement and MTA was not significantly different. In the MTA group, the presence of the powder resulted in a significant decrease (P<0.05) of the microhardness; however, its effect on CEM cement was not significant (P>0.05). CONCLUSION: Under the limitations of the present in vitro study, the presence of Osteon bone powder had no negative effect on the microhardness of CEM cement, contrary to its effect on MTA.

The Effect of a Mineralized Bone Graft on the Surface Microhardness of Mineral Trioxide Aggregate and Biodentine.

INTRODUCTION: This study was designed to determine the effect of Osteon II mineralized bone powder on the surface microhardness of two retrofilling materials: Mineral trioxide aggregate (MTA) and Biodentine (BD). METHODS AND MATERIALS: Each retrograde material was mixed and carried into 30 sterile custom-made plastic cylinders. Half of the samples in each group were exposed to Osteon II. All cylinders were submerged in simulated tissue fluid and incubated at 37°C and 100% relative humidity for 7 days. Surface microhardness values of each study group was attained using Vicker's microhardness test. The data were analyzed statistically using two-way ANOVA and independent t test at a significance level of 0.05. RESULTS: In all the setting conditions, BD had significantly greater surface microhardness than MTA (P<0.001). Surface microhardness of both materials was significantly reduced in the presence of osteon II (P=0.006 for BD and P<0.001 for MTA). CONCLUSION: Mineralized bone graft materials negatively affect surface microhardness of both MTA and BD. In presence of osteon II, BD had the highest surface microhardness.

Anatomic Features of C-shaped Mandibular Second Molars in a Selected Iranian Population Using CBCT.

INTRODUCTION: The aim of this retrospective study was to analyze the frequency of C-shaped root canal configuration and characterize mandibular root canal morphology using cone-beam computed tomography (CBCT) with 3D images in an Iranian population. METHODS AND MATERIALS: This study consisted of retrospective evaluation of CBCT images from 231 adult patients (153 with bilateral second mandibular molars). Two endodontists examined 384 mandibular second molars of a population in Tabriz, Iran to determine the presence of C-shaped canals and their anatomical characteristics. Root canal configurations were categorized at three different levels. Bilateral or unilateral occurrence of C-shaped canals and their relationship to gender, age and tooth position were examined and statistically analyzed using chi squared test and Fisher's exact test in SPSS 17. The significance level was set at 0.05. RESULTS: Of 384 mandibular second molars examined, 82 (21.4%) molars from 58 patients had a C-shaped root canal configuration. The prevalence of bilateral C-shaped canals was 15.6% amongst 153 patients with bilateral mandibular second molars. There were no significant differences in the distribution of C-shaped canals with respect to gender or age (P=0.06 and P=0.86, respectively). Only 4 teeth (4.9%) had the same root canal configuration from the orifice to the apex. In the remainder of the teeth, the cross-sectional root canal configuration changed at different levels of the root. CONCLUSION: There were significant variations in the number of roots and canal morphology in mandibular second molars, which should be considered during debridement and obturation of the root canal system.

Volume of Anesthetic Agents and IANB Success: A Systematic Review.

The aim of this study was to provide an evidence-based answer to the question: "Is 3.6-mL volume of an anesthetic agent more effective than 1.8-mL volume in providing anesthesia for mandibular molars?" Following formulation of research question and keyword selection, a comprehensive search of the following databases was conducted: Cochrane library, PubMed, Scopus, Google Scholar, ProQuest, and Clinicaltrials.gov. Three-phase eligibility appraisal and quality assessment of the studies were carried out by 2 independent reviewers. To reduce clinical heterogeneity, the included studies were divided into 2 groups: studies on healthy teeth and studies on teeth with pulpitis. The data of included studies were statistically combined through meta-analysis using a fixed-effects model. A total of 20,778 records were initially retrieved from the search. Following screening and eligibility assessment, 8 studies met the eligibility criteria and were included for qualitative synthesis. Of those, 5 studies were qualified for meta-analysis. In the irreversible pulpitis group, increasing the volume of anesthetic agent from 1.8 to 3.6 mL significantly increased the success rate of inferior alveolar nerve block (risk ratio = 2.45, 95% CI: 1.67-3.59, p < .001). However, there was insufficient evidence to draw a conclusion regarding healthy teeth.

Evaluation of some spiral and sequential computed tomography protocols of adults used in three hospitals in Shiraz, Iran with American College of Radiology and European Commission guidelines.

PURPOSE: Use of computed tomography (CT) has increased considerably all over the world. In addition, there has been an increased demand for utilisation of CT scanning in Iran over the past decade, especially after introducing multi-detector computed tomography (MDCT). It should be considered that making a mistake in the selection of scan parameters leads to patients receiving higher doses and having increased risk of cancer. All of these facts prompted us to compare six routine CT protocols in three hospitals in the city of Shiraz, and to compare the results with American College of Radiology (ACR) practice parameters and European Commission (EC) guidelines for dual- and multi-detector CT. MATERIAL AND METHODS: In the studied hospitals, 10 adult patients were chosen randomly for every six protocols, taken by different technologists. Seven and 11 scan factors in sequential and spiral scans, respectively, were compared with ACR (2014) and EC guidelines (EC16262 & EC2004). RESULTS: The majority of scan factors in sequential and the spiral protocols that were scrutinised met the guidelines. The CTDIvol and DLPs for sequential and spiral scans were lower than the dose reference level (DRL) pronounced by ACR in three CT departments, and they were compatible with the recommended dose by EC (16262) in a private hospital. CONCLUSIONS: Based on accordance of CTDIvol with ACR measurements and incompatibility with EC (2004) in teaching hospitals, we concluded that the recorded doses should be compared with different criteria. A regular review of protocols, using special protocols for different pathologic circumstances and continual education for technologists in the three CT departments, are recommended.

Quality of the calcium-enriched mixture apical plug in simulated apexification model; Effect of different mixing and placement methods.

BACKGROUND: Presence of voids at root canal wall‒apical seal material interface gives rise to the entrapment of toxins and microorganisms, which might have a relationship with post treatment disease. The present study was carried out to evaluate the effect of different mixing (manual and ultrasonic) and placement (manual and manual in association with indirect ultrasonic) methods of Calcium-enriched Mixture (CEM) cement on the number and dimensions of voids in the apical plug in simulated apexification models. MATERIAL AND METHODS: A total of 80 human maxillary central incisors with mature apices were selected. After simulation of the open apices, the teeth were divided into 4 groups (n=20) based on the mixing and placement techniques of CEM cement: group 1, manual mixing‒manual placement; group 2, manual mixing‒manual placement in association with indirect ultrasonic technique; group 3, ultrasonic mixing‒manual placement; and group 4, ultrasonic mixing‒manual placement in association with indirect ultrasonic technique. The samples were placed within gypsum sockets in which the periodontal ligament was reconstructed with polyether impression material. After placement the apical plugs, a wet piece of cotton was placed on canal orifices, followed by dressing with Cavit. The samples were incubated at 37°C and 100% relative humidity for 7 days. Then the voids between the material and root canal walls were counted with the CBCT technique. The void dimensions were scored with the following scoring system: score 1, no voids; score 2, the void size less than half of the size of the evaluated cross-section; score 3, the void size larger than half of the size of the evaluated cross-section. Statistical analyses were carried out with chi-squared and Fisher's exact tests. Statistical significance was defined at P<0.05. RESULTS: The maximum (7) and minimum (2) number of voids were detected in groups 1 and 2, respectively. The difference between these two groups was statistically significant (p<0.05). The differences in the number of voids between groups with similar mixing technique and different mixing techniques (i.e. groups 1 and 3 and groups 2 and 4) were not significant (p>0.05). Void dimensions in all the study groups were in score 2 category and no score 3 was recorded in the study groups. CONCLUSIONS: Under the limitations of the present study, manual placement in association with indirect ultrasonic technique was a proper technique to improve the quality of apical plug, considering the decrease in the number of voids. Key words:Apical plug, CEM cement, void.

Endodontic microleakage studies: correlation among different methods, clinical relevance, and potential laboratory errors.

INTRODUCTION: Creation of a tight seal in endodontically treated root canals is of utmost importance. Clinical and laboratory studies have a great role in the assessment of the sealing ability of endodontic materials. The present review was undertaken to evaluate correlation between different techniques used in microleakage studies in endodontics and the potential laboratory errors. EVIDENCE ACQUISITION: A systematic search was run using Medline, Biosis, Cochrane Database, Embase, Google Scholar, and Web of Science databases. Furthermore, the reference lists of the articles published on the subject were thoroughly searched. There was no language restriction in the search. Two reviewers separately evaluated the titles and abstracts. EVIDENCE SYNTHESIS: All the methods used might have proved useful if the study could have been carried out with a larger sample size, with carefully designed control groups. Furthermore, extra evaluations are recommended on the reliability of the method used. Examinations like glucose reactivity test, assessment of antimicrobial activity of the tested materials and in situ FISH examination for the reliability of bacterial leakage model have been recommended. It has been recommended that two or more methods be considered for each material in the same study. On the other hand, long-term animal studies can be useful with histological and radiographic evaluations for meticulous assessment of leakage. Furthermore, long-term clinical trials on humans might be helpful on the condition that confounding factors are controlled. CONCLUSIONS: Studies on microleakage should be focused on animal studies, clinical trials or laboratory tests. On the basis of available evidence, it appears that despite potential errors on microleakage studies they are very valuable.

Accuracy of Working Length Determination using NovApex and Root-ZX Apex Locators: An in vitro Study.

INTRODUCTION: This ex vivo study evaluated the accuracy of the Root-ZX electronic apex locator (EAL) (J. Morita, Tokyo, Japan) and the NovApex (Forum Technologies, Rishon Lezion, Israel) in determining the working length (WL) during endodontic treatment. MATERIALS AND METHODS: Forty extracted single-rooted human teeth were selected for this study. The actual WL was measured with visual technique by a size #15 k-file under magnification. Then, the canal lengths were measured electronically with both Root-ZX and NovApex apex locators within ±0.5 and ±1 mm. Mean percentage of data was analyzed between groups using paired t-test, with a statistically significant level of p < 0.05. RESULTS: The accuracy of NovApex apex locator was 85% within ±0.5 mm and 92.5% within ±1 mm. The accuracy of Root-ZX apex locator was 70% within ±0.5 mm and 97.5% within ±1 mm. There was no significant difference between the accuracy of the two EALs. CONCLUSION: Both the NovApex and Root-ZX EALs are useful for measuring the WL with high accuracy. CLINICAL SIGNIFICANCE: Given the importance of accurate WL determination in the success of endodontic treatments, the accuracy of different apex locators should be evaluated.