mohammad samiei

 This systematic review compared the accuracy of guided endodontics with the conventional method in non-surgical endodontic retreatment. 

 Two reviewers conducted a systematic search across PubMed/MEDLINE, Scopus, Embase, and Web of Science databases. Inclusion criteria consisted of all in vitro studies up to October 2024 that documented the application of cone-beam computed tomography in creating a guide for endodontic retreatment cases. The reviewers assessed the quality of the selected studies using the QUIN tool. Data regarding the first author and publication year, sample size, tooth type, retreatment application, computer-aided navigation technique, groups, image acquisition method, outcome measures, guided technique results, conventional technique results, and the main results were extracted using a predefined template. 

 Based on our criteria, seven studies were included in this review. The studies demonstrated variability in the techniques utilized. Iatrogenic errors were less frequent in guided groups, regardless of the operator’s level of experience. Most studies indicated that guided endodontics was more effective than conventional methods, particularly in fiber post-removal and access through MTA, minimizing volumetric loss of tooth structure, and preserving fracture resistance. However, when using guided techniques for removal of separated instruments, more iatrogenic errors occurred, and more time was required compared to the freehand technique. 

 Guided endodontics has shown promise in improving the outcomes of non-surgical retreatment by reducing complications. However, as all included studies were in vitro, clinical evidence is lacking, and the generalization of these results should be done cautiously. Further well-designed clinical studies are required to confirm these findings.

Since the Safavid Dynasty the reactions of the Shia clerics divided, some cooperated with the government and became depended on it, while others stayed independent. We may call the two the Isfahan school of thought and the Atabat school of thought respectively. The main question is how the clerics belonging to the two schools employed their social capital during the crises of the Fall of Isfahan and the Russo-Iranian Wars? And why? This research is concentrated on the clergy’s mobilization power and does not go further to assess positive or negative impacts of such mobilizations. Structuration method suggested by Giddens is applied as the research method. The findings show that during the Fall of Isfahan, the clerics could not use their social capital and their reaction was silence and stayed inactive. This outcome was a result of some religious and political structural factors hand in hand with some agents’ reactions who based on their political affiliations did not issue a fatwa for jihad. However, the clerics of Atabat employed their social capital during the Russo-Iranian Wars and issued fatwa for jihad because of both religious and political structures and also agents’ preferences, and their mass mobilization became astonishingly successful.

The question why Mussadiq failed in leading Iran National Movement and why he could not finally achieve his aims is one of the most important questions that researchers on Iranian contemporary history are dealing with. Using situational analysis this research attempts to find out shortcomings of Mussadiq's political actions which enabled the opposition to remove him from power. Up until now researchers provided diverse answers to this question. Some highlighted his failure in safeguarding the unity of his allies; others highlighted his weak political leadership; some others raised his trust in the US government as a reliable mediator between him and the British government; a group found his main problem to be giving free space to the Toodeh communist party; and finally another group asserted that his main shortcoming was rooted in his trust to the unorganized masses of people. All the five cases are true, although none reflects the main cause of his failure. After scrutinizing the situation, this paper concludes that the main cause was his uncertainty between two contradicting political roles: being a liberal Prime Minister or a revolutionary leader.

Indigenous knowledge systems of human livelihood in various fields, all born out of the effort for sustainable living in the environment, are highlighted. The documentation and collection of this knowledge is often the responsibility of ethnographers. One important area in ethnographic research is the documentation of indigenous knowledge in the preparation of food using various plants in their habitats. Therefore, given the diverse effective practices in the preparation of indigenous foods from wild plants and the fading of associated indigenous knowledge in recent civilization acceleration, it is essential for ethnobotanists to document this valuable knowledge. In this study, the focus was on the study of edible plants and the methods of cooking various foods using them in the Sefid Cheshmeh village of Golestan province.

This study is of ethnographic nature, and the method of selecting participants or samples has been purposeful sampling, which continued until theoretical saturation was achieved. The data for this research were obtained through open and semi-structured interviews, and efforts were made to gather information through participatory observation as well. Regarding participatory observation, it is necessary to mention that researchers were involved and participated in the collection of plants, preparation, and cooking in a way.

The results showed that local communities use different parts and products of plants for various nutritional and medicinal purposes, sometimes using food as medicine. In this study, 19 local foods that were prepared from plants by indigenous people were identified and examined. Among them, 11 foods were purely for nutritional purposes, and 8 foods had both medicinal and nutritional uses. Additionally, it was found that indigenous people cook special foods for occasions or specific seasons. The foods are as simple as possible and cooked quickly for family members to meet their physical needs. Given that food and its cooking methods are among the most important intangible cultural heritages and endangered among human societies, these studies can play a crucial role in preserving cultural and biological diversity..

Statement of the Problem: 

Bond strength of furcation repair materials is an essential factor in clinical success. Studies on the effect of adding titanium dioxide (TiO2) nanoparticles on the push-out bond strength of commonly used endodontic cements for furcation perforation repair is limited.

This study aimed to evaluate the effect of adding TiO2 nanoparticles to white Portland cement (PC), white mineral trioxide aggregate (MTA), and calcium enriched mixture cement (CEM) on their push-out bond strengths.

In this in vitro study, 120 endodontically treated molars were assigned to six groups (n=20) based on the material used to repair the perforation. In three groups, the cements (white PC, white MTA, and CEM) were placed in pure form, and in the three remaining groups, 1 weight % of TiO2 was added. The push-out bond strength was measured using a universal testing machine at a strain rate of 0.5 mm/min. Data were analyzed using one-way ANOVA and post hoc Games-Howell test (p< 0.05).

One-way ANOVA showed significant differences in the mean bond strength values between the six groups (p= 0.002). The post hoc Games-Howell test showed that the bond strengths in MTA+TiO2 and PC+TiO2 groups were significantly higher than those in MTA and PC groups, respectively. However, there was no significant difference in the bond strength between CEM and CEM+ TiO2 groups.

The incorporation of TiO2 into MTA and PC increased their push-out bond strength. However, it did not affect the push-out bond strength of CEM cement.

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.

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 differentia tion of DPSCs to odontoblasts was confirmed by Real Time PCR., ANOVA statistical analysis and Kruskal-Wallis test were used to analyze the data.

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, 1mT), even though the effective underlying mechanisms in this process are still unclear.

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.

Ethnobotany is the method of showing how local people make use of plants. Considering their use for the survival and livelihood of different communities since the past confirms the dependence on and connection with plants. In this study, Miran Castle area of Ramian city has been investigated regarding the richness of plant species and local people's indigenous knowledge.

The required information was gathered in the form of semi-structured interviews and participatory observation and interviews were conducted with local experts. In this research, we selected the species of 10 plant families that people had more knowledge about and the number of quotes was more than other plants.

The results confirmed a various knowledge and use of plants so that out of 15 selected plant species, 10 species had medicinal-edible uses, medicinal purposes, 3 for fodder, and 2 species had toxic properties. In addition, the study showed that the local people named the plants according to their morphological characteristics and ecological needs, also, they knew well where the plants grow, the way they were harvested, and used as food, medicine, tools, and shelter for living their lives.

The purpose of this in vitro study was to investigate the effect of incorporating silver nanoparticles (AgNPs) of herbal origin into mineral trioxide aggregate (MTA) on the push-out bond strength (PBS) and compressive strength (CS) in simulated furcal area perforations.

In this in vitro study, simulated furcal area perforations (1.3 mm in diameter and 2 mm in depth) were created in 40 extracted human lower molar teeth, which were divided into two groups (n=20): MTA alone and MTA combined with AgNPs (2% wt). Using a universal testing machine, PBS was evaluated by performing push-out tests, while CS was assessed using cylindrical specimens. The normal distribution of data was checked using the Kolmogorov-Smirnov test, and statistical analysis was performed using two-way ANOVA.

The CS results showed no significant difference between the MTA group at 4 and 21 days (P=0.297), but a significant difference was observed in the nanosilver/MTA group (P=0.013). However, there was no significant difference in the push-out bond strength among the study groups (P>0.05).

The incorporation of herbal origin silver nanoparticles did not significantly affect the PBS or CS of MTA.

Although nowadays the necessity of freedom of speech for safeguarding the health of a political system is not normally denied, still, there is no overwhelming consensus over the necessity of safeguarding the freedom of speech in the Islamic Republic of Iran. Perhaps the most important reason behind this shortcoming is that those thinkers who have been promoting freedom of speech used imported arguments. Whereas it is quite possible to base our argument for freedom of speech on the Islamic obligation of enjoining good and forbidding evil. This obligation which is known as a public responsibility in the Constitution has a very important political dimension that entails safeguarding freedom of speech for citizens. Basing freedom of speech on this obligation would guarantee an expansion of freedom of speech and reduction of its limits and would remove the obstacles in the way of political criticism, and would allow the elites outside the government to promote their thoughts and opinions which will be useful for society. In addition, it can be shown that this obligation outlaws any censorship of political writings. However, basing freedom of speech on the arguments that originated and formed in the Western civilization such as individualism has not been successful.

During the WWI and after violating the neutrality of Iran by hostile powers, Iranians experienced horrible consequences of war and after several years of drought and food shortcomings, famine and pandemics killed millions of Iranians. Total occupation and overt violation of neutrality by foreigners gradually resulted in a huge number of casualties that would not happen in peace conditions and undoubtedly the foreigners’ operations were among the causes of the 1917-1919 famine in Iran. Surprisingly, there is almost no trace of the horrible event in Iranians’ collective memory. The main question of this research is how we can compensate for this matter by using the standard definitions of war crimes available in international law and in this way help to reside this bitter experience in the collective memory of Iranians and the people of the world. This paper, examining the documents and memoirs of that period, shows many of those events, based on present international regulations and even of that time being “war crimes” or “crimes against humanity”. It concludes that although filing an international lawsuit to pursue is actually impossible because of political exigencies, using the legal terminology is necessary to register this historic catastrophe in the collective memory of Iranians and humanity as a whole.

Commonly used medicaments in the treatment of external inflammatory root resorption (EIRR) have shown adverse effects; resulting in an increasing tendency to employ natural and/or herbal medication. The present in vitro study aimed to evaluate the effects of curcumin and aloe vera, as two natural medicaments, on the changes of pH in external root surface defects; and compare their outcomes with the results obtained from the application of calcium hydroxide, as a conventional medicament used in endodontic treatments.

In the current investigation, 92 permanent teeth, with a single root canal, were randomly divided into four groups. Similar cavities were created on the buccal surfaces of roots, 5 mm from their apices. The root canals in each of the study groups were filled with curcumin, aloe vera, calcium hydroxide or normal saline. The pH was measured after 20 min (i.e. the baseline), 1, 7, 14, 21, and 28 days using a digital pH meter. The data were analysed using repeated-measures ANOVA and the statistical significance was set at P<0.05.

At the baseline, day 1 and day 7, the mean pH of both curcumin and aloe vera groups was higher than the mean pH of calcium hydroxide and normal saline groups (P<0.05). On day 14, the mean pH of aloe vera group was higher than that of calcium hydroxide and normal saline groups (P<0.05). On days 21 and 28, the mean pH of aloe vera group was higher than the mean pH of all the other groups (P<0.05). All other intergroup differences were not statistically significant at each time point (P>0.05).

The current in vitro study demonstrated that aloe vera was more alkaline than curcumin; nevertheless, both groups exhibited more alkalinity than calcium hydroxide.

 Biocompatible and biodegradable scaffolds based on natural polymers such as gelatin and chitosan (CS) provide suitable microenvironments in dental tissue engineering. In the present study, we report on the synthesis of injectable thermosensitive hydrogel (PNIPAAm-g-CS copolymer/gelatin hybrid hydrogel) for osteogenic differentiation of human dental pulp stem cells (hDPSCs).

 The CS-g-PNIPAAm was synthesized using the reaction of carboxyl terminated PNIPAAm with CS, which was then mixed with various amounts of gelatin solution in the presence of genipin as a chemical crosslinker to gain a homogenous solution. The chemical composition and microstructures of the fabricated hydrogels were confirmed by FT-IR and SEM analysis, respectively. To evaluate the mechanical properties (e.g., storage and loss modulus of the gels), the rheological analysis was considered. Calcium deposition and ALP activity of DPSCs were carried out using alizarin red staining and ALP test. While the live/dead assay was performed to study its toxicity, the real-time PCR was conducted to investigate the osteogenic differentiation of hDPSCs cultured on prepared hydrogels.

 The hydrogels with higher gelatin incorporation showed a slightly looser network compared to the other ones. The hydrogel with less gelatin indicates a rather higher value of G', indicating a higher elasticity due to more crosslinking reaction of amine groups of CS via a covalent bond with genipin. All the hydrogels contained viable cells with negligible dead cells, indicating the high biocompatibility of the prepared hydrogels for hDPSCs. The quantitative results of alizarin red staining displayed a significant rise in calcium deposition in hDPSCs cultured on prepared hydrogels after 21 days. Further, hDPSCs cultured on hydrogel with more gelatin displayed the most ALP activity. The expression of late osteogenic genes such as OCN and BMP-2 were respectively 6 and 4 times higher on the hydrogel with more gelatin than the control group after 21 days.

 The prepared PNIPAAm-g-CS copolymer/gelatin hybrid hydrogel presented great features (e.g., porous structure, suitable rheological behavior, and improved cell viability), and resulted in osteogenic differentiation necessary for dental tissue engineering.

Accessing the information that the elderly of different communities have , is one of the ways to restore traditions that are in danger of destruction. The purpose of this study is to identify the trees, their organs used by forest edge users and the by-products of this ecosystem. Information was recorded in the two ways of conversation in the natives' place of residence and participatory observation, and through field surveys, herbarium samples of tree limbs were collected and identified with reliable sources. For each tree, the local name, organ, used, medicinal properties and how to use them were recorded. In this research, 10 species of trees that were used more by local people were selected. The words expressed in their language for the parts of trees are completely narrative and are named according to their use. They are aware of the vegetative form, places where trees grow, different properties and ways of using tree limbs and how to exploit forest by-products and they use it in their lives.

During last half a century, particularly after the Islamic Revolution, Islamization of science and particularly humanities has been among important philosophical discussions, and still a lot is being published on this issue. This paper attempts to identify the exact subject of the discussion, and to show although objective science tries to make distance from every biases, even according to the realists who give priority to the correspondence, the impact of different worldviews on the objective theories they offer still can remain. Islamic worldview is no exception, and as sciences of different historical periods have been effected by the prevalent worldview of the time, it can be effected by the Islamic worldview. Then the theory of impossibility of Islamic science is refuted by the case of mind body dualism in psychology believed differently in Islamic and materialist worldviews. It is noteworthy that science can become Islamic in a natural way and not according to policymaking. Science cannot be Islamized using censorship or mixing it with propositions from the Quran and Hadith. At the end it is concluded that although science can become Islamic, Islamization of science based on censorship and similar artificial means is not fruitful.

The bond strength of the materials used as a cervical barrier in the pulp regeneration is essential for the success of treatment. This study aimed to evaluate the effects of triple antibiotic paste (TAP), double antibiotic paste (DAP), and simvastatin as intracanal medicaments on the dislodgement resistance of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM).

A total of 160 extracted human single-rooted teeth were selected, and root canal preparation was carried out. The teeth in each group were randomly divided into four subgroups: TAP, DAP, simvastatin, and the control group (without intracanal medicament). Four weeks after placing the medicaments, it was removed by sodium hypochlorite, and MTA and CEM were placed in the coronal third of the root canals. After a week, 2-mm-thick dentin disks were prepared from the coronal third of the roots, and the push-out test was performed using a universal testing machine. The data were analyzed using two-way ANOVA and independent t-test at a significance level of 0.05.

Regardless of the intracanal medicament, there was no significant difference between the overall bond strength of MTA (59.3±10 MPa) and CEM (55.8±11 MPa) (P=0.6). Furthermore, there were no significant differences in bond strength between the two intracanal medicament groups and the control group (P>0.05).

Under the limitations of the current study, DAP, simvastatin, and TAP, as intracanal medicaments, did not adversely affect the push-out bond strength of CEM and MTA.

The anti-American inclination of the Islamic Republic of Iran’s foreign policy-making is well established, and the bitter aspects of the two nation’s history well known. However, to assert a simple causal relationship between history and foreign-policy structure portrays the Islamic Republic’s anti-Americanism as inevitable, eternal and unrelated to actors’ agency. This article disputes this simple structural understanding by drawing on Greener’s method of applying path-dependency theory to political science. We first identify the ideas and structure of revolutionary Iran, benefiting in particular from the complementary insights of postcolonial theory. Following, we examine US policy choices in the Islamic Republic’s formative period of 1978–79—specifically those related to human rights, the shah and direct US intervention—and how these were perceived and acted upon in Tehran. Our findings indicate that American actions and Iranian decisions both influenced the establishment of a path-dependent process of perception and perpetration that continues until today. Successive Iranian governments have asserted that America ignores Iranian’s human rights, supports their enemies, and pursues direct intervention, while successive US government actions, motivated by Iranian counter-actions, have generated ample evidence to validate such claims. This can explain how a spiral of distrust emerged between the two nations.

Various studies have recommended using calcium-enriched mixture (CEM) cement in different endodontic treatments, including vital pulp therapy. However, possible reciprocal effects of the covering glass ionomer cement (GIC) on their mechanical properties have not been yet investigated in detail. The current research aimed to experimentally evaluate the surface microhardness of CEM cement and the covering GICs after different application/testing times.

Using stainless steel moulds (8×4×4 mm), CEM cement samples were prepared (n=120) and randomly divided into 12 experimental groups (n=10). CEM cement with thickness of 4 mm was inserted into the moulds, and the remaining spaces were filled with self-cured or light-cured resin-modified GICs at three-time intervals; immediate, in 15 min and after 24 h. Then, the samples were incubated for one and seven days. Using a Vickers microhardness tester, the microhardness of CEM and GICs was measured. The data were analyzed using two-way ANOVA and Tukey’s test, and the significance level was set at 5% (P<0.05).

The reciprocal effects of the type/time of application of GICs on the surface microhardness of CEM cement or GICs were statistically significant (P<0.001). The surface microhardness of CEM cement and both covering GICs significantly increased over time and in seven-day samples was significantly higher than in one-day samples (P<0.05).

Low surface microhardness of CEM/GICs in short-term (24 h) seems transient; and appears to be compensated over a longer period (i.e. 7-day). Therefore, using GICs adjacent to CEM cement in single-visit restorative treatments may be advocated

Public understanding, an important subject that is less discussed in the available literature, is under scrutiny by the book entitled Science, Society, Development: Papers on Public Understanding from both Historical and Philosophical Perspectives. Using critical rationalism as its main analytical approach, the book attempts to make a correction on the notion of science in the public perspective and also about the definition and necessity of public understanding. Despite the success of critical rationalism in enlightening the public about science, this approach alone is unable in clarifying non-scientific motivations such as political and economic interests behind propagating science. To prevent this shortcoming, we could consider besides critical rationalism some other approaches which help us and the public detect non-scientific motivations and to distinguish between genuine attempts and those who look at science as a means. This paper also discusses some formative points and suggests four complementary additions to the book. Overall, the book is an in-depth and valuable attempt on this subject.

This research sheds light on what has constituted and defined Iran’s postrevolutionary political identity and provides insights into its development with important socio-political implications. In order to understand the configurationand the evolution of post-revolutionary identity in Iran, we examined Hajj Messages issued by Iran’s Supreme Leader through a content analysis within the framework of a threefold typological model of identity advanced by the authors:empiricistic, rationalistic, and idealistic. The passages selected from the Supreme Leader’s Hajj Messages are classified into the above-mentioned three categories based on the model. Results indicate that in the post-revolutionary Iran, arationalism that inherits the doctrines of anti-despotism, anti-colonialism, and return to Islam prevails. It is also observed that the post-revolutionary identity of Iran has both empiricist and idealist factors, in the narrations of which the rituals of Hajj and the history of prophets are underscored respectively. This research also concerns ebbs and flows in the process of identity development in postrevolutionary Iran. Whilst the rationalist factor keeps stable and is graduallystrengthening its preponderance, idealism is ebbing away and empiricism is flowing in.

Prevention of dentinal crack formation is of utmost importance in endodontic treatment. This study aimed to evaluate the effect of RaCe, ProTaper, and V-Taper rotary systems on dentinal crack formation in three root regions during endodontic treatment.

Seventy human mandibular first molars were selected randomly, and their distal roots were used. Ten samples were assigned to the control group, and sixty samples were assigned to three groups (n=20). Each group was prepared with RaCe, ProTaper, or V-Taper rotary files according to the manufacturers’ instructions. A stereomicroscope was used to view cracks at ×40 magnification. Friedman’s, chi-squared, and Kruskal-Wallis tests were used for statistical analysis of data (P<0.05).

A comparison of the three rotary systems did not reveal any significant differences in the number of cracks between the three root thirds evaluated (P>0.05). A comparison of the number of cracks in the coronal, middle, and apical thirds in each rotary system showed that the number of cracks in the middle third was fewer than that in the two other thirds only in the V-Taper group (P<0.05), with no significant differences in the ProTaper and RaCe groups between the different root regions (P>0.05).

The application of RaCe, ProTaper, and V-Taper rotary files resulted in a similar rate of crack formation in endodontic treatment. V-Taper files created the minimum number of cracks in the middle third.

< p >In recent years the notion of development has expanded to include besides the economic dimension variety of other dimensions, one of which is subjective well-being. This paper attempts to find and analyze Iran’s ranking among other countries in subjective well-being based on Gallop findings. The findings show that in subjective well-being Iran is in crisis, while its ranking in other indicators of development based on Gallop’s and World Bank’s findings is better. To understand this gap between the subjective and objective well-being measured by other indicators of development, including GDP per capita, Gini coefficient, social support, healthy life expectancy, freedom to make life choices, generosity, and freedom from corruption, three analyses has been suggested: historical-cultural, political discourse and media sphere. In conclusion, for overcoming the crisis of subjective well-being in Iran the cultural policies should be revised, the political discourse must change to a moderate and more sympathetic discourse with free space for healthy competitions, and the monopoly of the state in radio and television should be removed to give different groups of the Iranian elites the opportunity to work in line with national interests to convince the public of the realities of the status quo.

The release of information without scientific basis about the new corona virus (2019) pandemic has now become a global anxiety. The aim of this study was to analyze the performance, planning and flexibility of the Vice Chancellor for Research and Technology of Tabriz University of Medical Sciences in response to the new coronavirus (covid-19) Pandemic crisis to produce and disseminate evidence-based information.

This was an organizational study which was done by descriptive methods. After announcement of a call for Covid-19 research project from the website of Tabriz University of Medical Science (TUOMS), a new policy was arranged for review process. The time and production of evidence were the major factors for this experience. Electronic arbitration methods and virtual discussion were used. Quantitative data was performed in MS Excel version 16 and the results were presented in the form of tables and graphs.

Due to the urgency of aggregating the evidence, the review process was done by the scientific team during a maximum of 72 and by the ethical team within 24 hours (excluding the spent time by the principal investigators), 64 research and technological projects were prioritized. The shortest possible review process, the interactive approach of reviewing and problem-based nature of the approved topics were among the most important achievements.

This experience showed that cohesive organizational activities in the field of research and flexibility of the processes can play a significant role in dealing with epidemics and crises in order to overcome obstacles, challenges and for production of scientific evidence.

 Stem cell-based treatment modalities have been potential strategies for tissue regenerationin many conditions. Several studies have evaluated the biologic properties of DPSCs and their efficacyin the treatment of a variety of diseases. The present study was undertaken to evaluate the adhesionbehavior of DPSCs on different endodontic materials before and after setting.

 The crowns of the selected teeth were removed, and the root canals were prepared andobturated with gutta-percha and AH26 sealer. A retrograde cavity was prepared at root ends. Differentmaterials were placed in the cavities. Then the samples were attached to the wells with the use of achemical glue. Dental pulp stem cells were allowed to proliferate to reach a count of 2 million andtransferred to -12well plates in association with a culture medium. Finally, the samples attached to thewells were exposed to the stem cells immersed in the culture medium before and after setting. Thenadhesion of the stem cells was evaluated using SEM.

 The SEM results showed cellular adhesion in the samples containing CEM cement both beforeand after setting. The samples containing MTA Angelus and ProRoot MTA exhibited cellular adhesionbefore setting, with no cellular adhesion after setting. The samples containing AH26 and MTA Fillapexsealers exhibited cellular adhesion after setting, with no adhesion before setting. The samples containingsimvastatin exhibited no cellular adhesion before setting; this material had dissolved in the culturemedium after setting evaluation.

The results of the present study showed that of all the materials tested, CEM cement hadthe highest capacity for dental pulp stem cell adhesion.

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

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

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

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

Periodontitis can lead to a progressive destruction of periodontal tissues supporting the tooth. Developing biomaterials for tissue engineering has noticeably improved the existing treatment options. The present study investigated the gelatin-hydroxyapatite nanofibers as promising scaffolds for guided tissue regeneration (GTR).

The scaffolds were prepared through electro-spinning technique and then the physic-chemical properties and the cytotoxic effect (on dental derived mesenchymal stem cells) were assessed.

The nano-scaffolds were successfully prepared with mono-dispersed nano-scale diameter (102 ± 0.10 nm), negative surface charge (-20 ± 0.17 mV) and uniform network-shaped morphology. The treatment of the mesenchymal stem cells was derived from human dental pulp stem cells (hDPSC) with gelatin-hydroxyapatite nanofibers showed that the prepared scaffolds revealed a great proliferative effect. Besides, the applied method can be used to prepare fiber-based structures via other polymeric materials.

Incorporating different materials to decrease the degradation rate of the fibers can match with the speed of tissue regeneration. In this case, the prepared nanofibers can be applied as a membrane biomaterial.