The Power of Professional Learning Communities Essay

Benjamin Franklin said â€Å"An investment in knowledge pays the best interest.† Education opens the door for everyone to excel in life. To become a strong nation, its people, especially children, must have a good education so the nation can continue to excel and become stronger. Nevertheless, America is suffering through an education crisis today. The current statistics show that the United States is falling behind in education compared to other countries. The illiteracy rate is high, and the graduation rates for inner city children are low. The causes of this crisis are everyday problems such as lack of interest in school, poverty, and standardized testing. There are many solutions to the problem, but one solution, Professional Learning†¦show more content†¦The United States also places 25th in math, 17th in science, and 14th in reading (â€Å"Best Education in the World,† 2012). Fourth Graders in the U.S. are 11th in Math in the Trends in International Mathe matics and Science Study (â€Å"U.S. education spending tops Global List,† 2013.) Sixty-six percent of all fourth graders are not reading at grade level (Reese, Fredrick 2014). Fourteen percent of the population, or 32 million adults, cannot read. Nineteen percent of high school graduates cannot read. In less developed countries like Chile, Brazil, and Latina, children are increasing in academics three times faster than American Students (â€Å"Best Education in the World,† 2012). The problem in the education system lies within the public schools, because the majority of students attend public schools. In fact, only ten percent of children attend private schools (Jennings, 2013). USA Today said â€Å"Students in a handful of big-city school districts have a less than 50-50 chance of graduating from high school with their peers, and a few cities graduate far fewer than half each spring†¦Ã¢â‚¬  (Toppo, 2006). With these statistics in education, many people wonde r why the United States is lagging, but one major reason for the lagging is teaching methods. The use of standardized test has been used for many years. Tests such as ACT, SAT, EOC, and Gateway were made toShow MoreRelatedThe Danielson Framework Is A Tool964 Words   |  4 Pagescorrelation between topics. They know their students skills and what they know. They are aware of the developmental stages of their students and how the stages play a role in students’ learning. They set reasonable outcomes for students, use a wide range of resources for students’ use as well as for their professional knowledge. Distinguish teachers also plan lessons that flows in a sequential matter and aligns the instruction with school curriculum and state standards. Finally, they choose appropriateRead MoreThe Contribution Of Servant Leadership1310 Words   |  6 Pageseducational professional learning. 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Early Strikes Of The American Labor Movement Essay Example For Students

Early Strikes Of The American Labor Movement Essay EARLY STRIKES OF THE LABOR MOVEMENT In the mid-nineteenth century and early twentieth century, industry in America was growing at an alarming rate. This growth brought about basic changes in the way things were produced and in the lives of those who produced them. It was the Civil War that first started to change industrial landscape of the nation. More than a million dollars a day were spent on weapons, ammunition, machinery, clothing, boots, shoes, and canned goods (Meltzer, 3). The high demand for so many different items brought bigger, newer and more efficient factories. The factories were producing cheaper products than the small, independent, hand-made specialists were. As a result of this industrialization a shoemaker, for example, no longer made the whole shoe. Instead the new shoemaker only made the heel, or shoelace. Mass production left no place for the individual craftsman (Meltzer, 4). The new assembly line organization had several side effects. One was condition for the workers. Factories often provided inadequate housing which lead to bad living conditions. The working conditions were usually dirty, uncomfortable, and unsafe. By 1900 nearly one out of every five in the labor force was a woman. Conditions for women and children were often much worse. They women were used to hard work. In the home they put in 12 hours a day or more, cleaning, cooking, sewing, rearing children, and helping with the mens chores as well, (Foner, Women 8). Industry owners sent people to rural parts of the country to recruit women. They promised the women high wages, leisure hours, and silk dresses. Instead, the women worked 14 to 16 hours a day for an average wage of $1.56 a week. They received no silk dresses. Some of the hands never touch their money from months end to months end. Once in two weeks is payday. A woman had then worked 122 hours. The corporation furnishes her house. There is rent to be paid; there are also the corporation stores from which she has been getting her food, coal and other cheap stuff on sale may tempt her to purchase (Meltzer, 21). Factory employers also cheated women, believing they were defenseless. Some employers did not pay them at all, or deducted a large part of their pay for imperfect work. An 1870 survey showed that 7,000 of the working women could only afford to live in cellars and 20,000 were near starvation. For children in the nineteenth century, idleness was considered a sin. And the factory was a God sent protector against the evils into which idleness might lead children. In the 1830s in Massachusetts, children in the factory worked 12 to 13 hours a day. In 1845, the mills in Lowell set hours for children from sunup to sunset. In New England two fifths of all workers were children. The Census of 1870 reported 700,000 children ages ten to fifteen at work. By 1910, nearly 2 million children ages ten to fifteen were at work. In addition to the extremely high hours, the conditions children were forced to work in were atrocious. The factories were often dirty, unsanitary, cramped, dark, and unsafe. As difference in wealth between workers and owners increased, there was a greater need for the worker to be able to improve their circumstances. There were several key strikes through which the workers fought to improve conditions. In this paper I will investigate the issues, events, and outcomes surrounding three important strikes. The Homestead Strike: 1891, Steel Industry, Pittsburgh, Pennsylvania Conditions in the steel mills were difficult, dangerous and wages were low. Everywhere in the enormous sheds were pits gaping like the mouth of hell, and ovens emitting a terrible degree of heat, with grimy men filling and lining them. .ub1e25a17a303ed04a97a8aa136b7790b , .ub1e25a17a303ed04a97a8aa136b7790b .postImageUrl , .ub1e25a17a303ed04a97a8aa136b7790b .centered-text-area { min-height: 80px; position: relative; } .ub1e25a17a303ed04a97a8aa136b7790b , .ub1e25a17a303ed04a97a8aa136b7790b:hover , .ub1e25a17a303ed04a97a8aa136b7790b:visited , .ub1e25a17a303ed04a97a8aa136b7790b:active { border:0!important; } .ub1e25a17a303ed04a97a8aa136b7790b .clearfix:after { content: ""; display: table; clear: both; } .ub1e25a17a303ed04a97a8aa136b7790b { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .ub1e25a17a303ed04a97a8aa136b7790b:active , .ub1e25a17a303ed04a97a8aa136b7790b:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .ub1e25a17a303ed04a97a8aa136b7790b .centered-text-area { width: 100%; position: relative ; } .ub1e25a17a303ed04a97a8aa136b7790b .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .ub1e25a17a303ed04a97a8aa136b7790b .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .ub1e25a17a303ed04a97a8aa136b7790b .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .ub1e25a17a303ed04a97a8aa136b7790b:hover .ctaButton { background-color: #34495E!important; } .ub1e25a17a303ed04a97a8aa136b7790b .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .ub1e25a17a303ed04a97a8aa136b7790b .ub1e25a17a303ed04a97a8aa136b7790b-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .ub1e25a17a303ed04a97a8aa136b7790b:after { content: ""; display: block; clear: both; } READ: Japanese Temple Architecture Essay One man jumps down, works desperately for a few minutes, and is then pulled up exhausted. Another immediately takes his place; there is no hesitation, (Meltzer, 137). The accident rate in the steel mills of Pittsburgh was very high. In 1891 there was a total of 300 deaths and over 2,000 injuries. People died or were injured from explosions, burnings, asphyxiation, electric shocks, falls, crushing, etc. In 1889 the Amalgamated Association of Iron and Steel Workers organized to seek higher wages and .

Homosexuality Nature or Nurture Essay Example

Homosexuality: Nature or Nurture Paper Abstract The quest to achieve ultimate unity has become quite the hot topic in present years. In Ryan D. Johnson’s online research article, Homosexuality: Nature or Nurture, an explanation of homosexuality is broken down so the world has a better understanding of homosexuals. As referred to in the title, the origin of homosexuality has been debated to be because of nature or nurture. Basically, are people gay because it’s their personal choice or is it just who they are? The idea behind nurture is that the way one was raised can eventually affect a child’s sexual preference. In the first paragraph of this study, Johnson travels back to ancient Greece claiming that homosexuality has been around for ages, yet the root of the question still seems to be up in the air. According to the APA â€Å"sexual orientation is not a choice†¦[but] social theorists argue that on individual’s upbringing can directly influence this† (Johnson 1). Biological theorists believe that there is an actual genetic way of justifying homosexuality. Scientists and Psychoanalysts have evaluated the chromosomes of straight and gay males nonetheless the hypothalamus, and other certain wavelengths of their brains to find any comparisons to give reason to such different sexual preferences. This study focuses on the internal and external factors that could possibly contribute to and elucidate how one is a homosexual. The first experiment that Johnson assessed was that of Alfred Kinsey from the University of Indiana. We will write a custom essay sample on Homosexuality: Nature or Nurture specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Homosexuality: Nature or Nurture specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Homosexuality: Nature or Nurture specifically for you FOR ONLY $16.38 $13.9/page Hire Writer His target objective was ‘1) to find out how many adult males engaged in homosexual behavior, and 2) to suggest theories about [how] it came to be. ’ Many men said they had not participated in any homosexual relationships, yet more answered yes when asked about same-sex relationships. This shows that most men feel more comfortable with having an encounter with two other women, but not another male. Then again this is the typical heterosexual man, or the closeted homosexual that skew such statistics. This study was also conducted in the 1930’s, so homosexuality wasn’t as accepted as it is today. Karen Hooker took it in her hands to perform what is known as the first psychological tests to discover whether homosexuality was a mental illness or that of personal preference. She found that between the straight and gay men who were involved in the test, there was no difference in her findings. Homosexuality was from there on out no longer to be considered a mental disorder or illness, but an expression of one’s true nature. D. F. Swaab wanted to look into the cranial aspects of homosexuality. â€Å"Swaab found in his post-mortem examination of homosexual males’ brains that a portion of the hypothalamus of the brain was structurally different than a heterosexual brain’’(Johnson 2). This just shows that gay males have a super-hyper sex drive compared to heterosexual men. A heightened libido can explain the promiscuity of most gay males but it’s not enough to narrow that to only homosexuals. In 1991 a man named Simon LeVay followed execution of the Swaab’s hypothalamus theory. Since this experiment, along with Swaab’s, was exercised on the non-living the moral aspects are questionable, although these brains were those of AIDS patients. Finding that â€Å"the third interstitial notch of the anterior hypothalamus was two to three times smaller in homosexual men then in heterosexual men†(Johnson 3). According to LeVay this fact proves that homosexuality is derived from the make up of one’s brain. J. Michael Bailey and Richard Pillard did one of the most interesting experiments. They studied the variation of homosexuality in identical and fraternal twins, along with non-related adopted brothers. Identical brothers are more likely to be gay compared to fraternal and non-related brothers. The closer two are genetically the more likely one twin is to be gay. This was also found in a study with female counterparts. To focus more on the nurture part of this article, many sociobiologists and sociobehavoirists take a look at the parents and how one was brought up. If there was a weak father figure and a strong motherly figure then homosexuality is said to be more common because the child was unable to overcome their ‘Oedipus syndrome. Also the certain roles that are given to children at young ages have a common effect on sexuality, whether they follow a male and female stereotype that is. How a child is raised, what they witness and experience as they grow up all come together under the idea that nurture over nature has a bigger influence on a person’s sexuality. Therefore this article was quite informative about all the research that has been done over the years to de termine the nature verse nurture question dealing with homosexuality. The article was not as descriptive with calculations and didn’t go too in-detail about what each experiment entailed but the outcomes gave enough data to let the reader establish their own opinion. Kinsey’s findings claimed that many men were not comfortable with the idea of two men together, but another same-sex relation, being women, didn’t bother them. These ‘facts’ were pretty irrelevant since the experiment was very outdated and didn’t mention whether nature or nurturing were involved but just the appeal of being gay. Also it never mentioned how homosexuality came to be, as Kinsey claimed was one of the reasons for the experiment. Hooker did a great analysis to prove that homosexuality was completely not a mental disorder yet a decision of the heart. Swaab’s focus was on how the brains of a homosexual and a heterosexual differed. Concluding that since a part of a gay male’s hypothalamus is enlarged their sex drive is also larger. This theory needed more information and tests to back it up. Levay’s study dealt also with how one’s brain anatomy plays a role in one’s sexuality. Lastly Pillard and Bailey decided that when it comes to twins and sexuality the closer they are in genetic make up the more likely one will be homosexual. The satisfactoriness of this study was adequate in representing the male’s point of view of homosexuality but there was little no to reference to women. The theoretical framework was lacking for this reason. In order to determine whether homosexuality is a matter of nature or nurture this study should’ve involved both sexes to develop a fully rounded conclusion. No ethics other then that of experimenting on the non-living brain were overturn. The meaningfulness of the survey on the other hand, held great weight. The importance of teaching the masses that homosexuality is not a choice but who a person is inside cannot be stressed enough. Nature cannot be scientifically explained sometimes, and nurturing only plays a role for so long. The whole point of this study was to show how everyone is equal and should be treated equal no matter their sexual orientation, our anatomies might be different along with our chemical make up, but that doesn’t just involve sexual orientation. Everyone is different, and no study should have to make sense of that.

The wars essays

The wars essays Sigmund Freud once argued that "our species has a volcanic potential to erupt in aggression . . . [and] that we harbour not only positive survival instincts but also a self-destructive 'death instinct', which we usually displace towards others in aggression" (Myers 666). Timothy Findley, born in 1930 in Toronto, Canada, explores our human predilection towards violence in his third novel, The Wars. It is human brutality that initiates the horrors of World War I, the war that takes place in this narrative. Findley dedicated this novel to the memory of his uncle, Thomas Irving Findley, who 'died at home of injuries inflicted in the First World War" (Cude 75) and may have propelled him to feel so strongly about "what people really do to one another" (Inside Memory 19). Findley feels a great fondness for animals, and this affection surfaces faithfully in many of his literary works. The Wars is a novel wrought with imagery, and the most often recurring pattern is that of animals. Throughou t the novel, young Robert Ross' strong connection with animals is continually depicted in his encounters with the creatures. Findley uses Robert to reveal the many similarities between humans and animals. The only quality, which we humans do not appear to share with our animal counterparts, is our inexplicable predisposition to needless savagery. In his video documentary, The Anatomy of a Writer, Findley describes his affinity for animals when he says that he has "always been in awe of . . . animals. [He has] never understood where [humankind] picked up the idea that [animals] are less than [people] are-that man is everything". In The Wars, Findley stresses his belief that humans are "no better and no worse-no larger and no smaller than any other creature that walks or crawls or flies or swims. [They are] merely different" (Roberts 56). Parallels are drawn between the protagonist, Robert Ross, and many of the animals that appear throughout the novel. Rob...

Informational interview Essay Example | Topics and Well Written Essays - 250 words

Informational interview - Essay Example dent of me to conduct a personalized interview with some of the accountants who have made it to the top in order to become adept with the skills and challenges they faced. c) During my interviews, the interviewees were more than interested and willing to offer the information I ask for. Their corporation partly showed their experience and the importance of sharing information to other people.d)A part from the learned skills employees’ performance requires a lot more of interpersonal skills to allow right communication with employers, other employees and customers. In fact, to improve your career and get promotions especially in the field of accounting you need to put more diligence, creativity, and ethics at work. e) I am going to talk about the information I got from an interview with an accountant onhow the skills and challenges experienced overtime in the field of accounting are crucial to the transcending of his career to greater heights even to the position of a CFO. a) Good communication skills: As an accountant aspiring to be a manager, you need effective communication skills in order to relay you facts efficiently to the junior as well as senior staff. This will also help you reduce making many

U.S. Supreme Court Case Tennessee vs. Garner Study

U.S. Supreme Court Tennessee vs. Garner - Case Study Example The various arms and appendages of law while towing the practical manifestations of their powers do sometimes give way to special situations that alter and remold the conscience of a society and bring them under direct and enhanced observation and scrutiny of the masses and the intelligentsia. Infact such instances happen to be the important turning points in the legal and judicial history of any nation and do many a times lead to the evolution of the existing statutory provisions in the light of the current and emerging changes in the society. US Supreme Court case Tennessee vs. Garner is one such thought provoking event in the legal history of the US that strikingly challenged the existing statutory provisions pertaining to the use of force by the law enforcement agencies and called for reinterpretation and reshaping of this earlier taken for granted aspect of the policing in the US. October 3, 1974 was one other usual day in the life of the Memphis Police Officers Leslie Wright and Eton Hymon, when they were ordered to respond to a "prowler inside call". Both the officers promptly arrived on the scene of crime and after receiving relevant feedback from the neighbors, proceeded to scan the house being targeted. Hymon noticed a person running across the backyard and with the aid of his flashlight, was reasonably able to discern that the suspect, Edward Garner was an unarmed teenager of slight built (Findlaw, 2008). When Garner tried to climb over a fence, Hymon shot him in the back of his head to prevent him from escaping from the scene of crime (Findlaw, 2008). Later on a paltry ten dollars and a ring stolen from the house being scanned was found on the body of the suspect. Hymon acted in direct exercise of the authority given by a Tennessee statute to its police officers, sanctioning a deadly use of force so as to apprehend a fleeing suspect (Findlaw, 2008). The father of the deceased teenager filed a suit in the Federal District Court, to seek damages for the death and violation of his son's constitutional rights (Findlaw, 2008). The District Court upheld the constitutional credentials of the given statute and declared the officer's actions to be legal and valid (Findlaw, 2008). However, the United States Court of Appeals for the Sixth Circuit, while responding to an appeal by the appellee-respondent, reversed, stating that the use of force against a fleeing suspect in pursuance of the requirements of the Fourth Amendment is subject to be qualified in the light of the criteria of reasonableness (Findlaw, 2008). The basic issue that this case brings to fore is the ascertaining of the constitutionality of the deadly use of force by the law enforcement agencies against an unarmed, fleeing suspect (Findlaw, 2008). It questions the gross generalization of the provisions pertaining to the use of force by the law enforcement agencies against the relatively innocuous suspects who try to flee. Should the nature or proportion of force used by a police team against an escaping terrorist be same as that used against a harmless teenager, who attempts to escape from the scene of some petty crime This case highlights the human rights of the fleeing suspects and pragmatically checks the unrestrained use of force by t

Genotoxicity of Endodontic Irrigants and Medicaments

Genotoxicity of Endodontic Irrigants and Medicaments Abstract Genotoxicity describes a deleterious action on a cells genetic material affecting its integrity. This includes both certain chemical compounds and certain types of radiation. Genotoxic substances are all those with affinity to interact with DNA which is not proof of their dangerousness to humans, but does render them potentially mutagenic or carcinogenic. This review will address the genotoxicity of endodontic irrigants, medicaments, and sealers. It has been postulated that exposure of living tissues to cytotoxic agents can result in chronic cell injury, compensatory cell proliferation, hyperplasia, irritation, degeneration or tissue necrosis (1) and ultimately tumor development (2, 3). It is likely that proliferation may increase the risk of mutations within target cells and also be important in selective clonal expansion of exogenously or endogenously initiated cells from pre-neoplastic foci and eventually tumors (2). Thus, the DNA damage may diminish the self-repairing potential of tissue (4). In light of these considerations, genotoxicity and cytotoxicity assays gained widespread acceptance as an important and useful indicator of carcinogenicity. Definition of genotoxicity In genetics, genotoxicity describes a deleterious action on a cells genetic material affecting its integrity. This includes both certain chemical compounds and certain types of radiation. Genotoxic substances are all those with affinity to interact with DNA which is not proof of their dangerousness to humans, but does render them potentially mutagenic or carcinogenic (5). Genotoxicity of root canal irrigants Sodium hypochlorite Sodium hypochlorite (NaOCl) is recommended as the main endodontic irrigant because of its ability to dissolve organic matter together with its broad antimicrobial action (6). NaOCl is commercially available as aqueous solutions with concentrations ranging from 1% to 15% and having an alkaline pH with values around 11 (7). Sodium hypochlorite has a wide range activity against both Gram positive and Gram negative bacteria. It is the strongest antifungal agent among root canal irrigations and medications. Furthermore, it is the only root canal irrigant that can destroy the microbial biofilm effectively (6, 7). Hamaguchi and Tsyutsui (8) showed that NaOCl was not genotoxic to mamalian cells. Hagiwara et al. (9) showed that sodium hypochlorite induced chromosome aberrations in Syrian hamster embryo (SHE) cells when treated in the presence of exogenous metabolic activation. Aubut et al. (10) revealed that neutralizing a 2.5% NaOCl solution did not induce any genotoxic effect. Marins et al. (11) showed that NaOCl did not induce any genotoxic effect. Chlorhexidine CHX is a synthetic cationic bis-guanide that consists of two symmetric 4-cholorophenyl rings and two biguanide groups connected by a central hexamethylene chain. CHX is a positively charged hydrophobic and lipophilic molecule that interacts with phospholipids and lipopolysaccharides on the cell membrane of bacteria and then enters the cell through some type of active or passive transport mechanism (12). Its efficacy is due to the interaction of the positive charge of the molecule and the negatively charged phosphate groups on microbial cell walls (12), thereby altering the cells osmotic equilibrium. This increases the permeability of the cell wall, which allows the CHX molecule to penetrate into the bacteria. CHX is a base and is stable as a salt. The most common oral preparation, chlorhexidine gluconate, is water-soluble and at physiologic pH, it readily dissociates and releases the positively charged chlorhexidine component (12). At 0.2% concentration, due to the leakage of low mol ecular weight substances(potassium and phosphorous) from the bacterial cell wall, CHX is bacteriostatic. On the other hand, at 2% concentration, CHX is bactericidal, as precipitation of the cytoplasmic contents occurs and resulting in cell death (13). Ribeiro et al. (14) revealed that chlorhexidine digluconate is able to induce primary DNA damage in leukocytes and in oral mucosal cells, but no chromosome breakage or loss in erythrocytes. Another study indicated that CHX in 0.01% and 1% concentrations did not induce DNA damage. Yeung et al. (15) stated that potential genotoxicity and tissue damage when extruded into the periradicular tissue and at higher concentrations should be considered during periodontal and endodontic practice. Li et al. (16) revealed that CHX-induced genotoxicity on macrophages may be via reactive oxygen species generation. MTAD BioPure (Dentsply, Tulsa Dental, Tulsa, OK, USA), otherwise known as MTAD, was introduced by Torabinejad et al. in 2003 (17). It is composed of 3% doxycycline, 4.25% citric acid and a detergent (0.5% Polysorbate 80) (17). Marins et al. (18) assessed the genotoxicity of MTAD using single cell gel (comet) assay. Results showed that the BioPure MTAD was able to promote DNA breakage in CHO cells only at the highest concentration tested as well as to induce significant increase in tail moment at all tested concentrations in murine fibroblasts. Another study revealed that MTAD did not cause cell death, but presented genotoxic effects (19). EDTA EDTA (Ethylenediaminetetraacetic acid) refers to the chelating agent with the formula (HO2CCH2)2NCH2CH2N(CH2CO2H)2. This amino acid is widely used to sequester di- and tri-valent metal ions. EDTA binds to metals via four carboxylate and two amine groups. EDTA forms specially strong complexes with Mn(II), Cu(II), Fe(III), and Co(III). EDTA is mostly synthesised from 1,2-diaminoethane (ethylenediamine), formaldehyde (methanal), water and sodium cyanide. This yields the tetra sodium salt, which can be converted into the acidic forms by acidification (20, 21). EDTA is a polyamino carboxylic acid and a colourless, water-soluble solid. It is widely used to dissolve limescale. Its usefulness arises due to its role as a hexadentate ligand and chelating agent, i.e. its ability to sequester metalions such as Ca2+ and Fe3+. After being bound by EDTA, metal ions remain in solution but exhibit diminished reactivity. EDTA is produced as several salts, notably disodium EDTA and calcium disodium EDTA. The compound was first described in 1935 by Ferdinand Munz, who prepared the compound from ethylenediamine and chloroacetic acid (22). Today, EDTA is mainly synthesised from ethylenediamine (1,2-diaminoethane), formaldehyde, and sodium cyanide (22). EDTA reacts with the calcium ions in dentine and forms soluble calcium chelates. EDTA demineralizes dentine to a depth of 20–30 ÃŽ ¼m in 5 min (23). According to Heindorff et al. (24) EDTA influences chromosome breakage by mutagenic agents. In particular, when applied in combination with chemical mutagens, EDTA enhances mutagen-induced aberration frequencies. Furthermore, they reported that EDTA affects the inhibition of DNA synthesis in primary cultures of mammalian cells. This may be due to impairment of enzymes involved in DNA replication. Using single cell gel (Comet)assay, Marins et al. (25) showed that EDTA did not produce genotoxic effects. Iodine potassium iodide (IKI) Iodine was first discovered in seaweed in the early 1800s. Although its exact mode of action is not fully known, it is thought to induce cell death nonspecifically due to the oxidizing effects of free iodine on SH-OH- and NH groups of amino acids and on double bonds of unsaturated fatty acids. Iodine is highly efficient microbicide to a wide variety of bacterial, fungal and viral infections (26). Potassium iodide (KI) is a compound made of 76% of iodine and 23% of the alkali metal potassium by weight. KI is prepared by reacting iodine with a hot solution of potassium hydroxide, the product being subsequently reduced to iodide by heating the dry reaction mixture with carbon. Another form of iodine compounds is IKI. The solution can be prepared by mixing 2 g of iodine in 4 g of KI; this mixture then is dissolved in 94 ml of distilled water (26). Poul et al. (27) assessed the genotoxic effects of potassium iodate in vitro using the alkaline comet assay and the cytokinesis-block micronucleus assay on CHO cells. Results showed that potassium chlorate as well as potassium iodide, bromide and chloride did not induced DNA damage in the alkaline comet assay for doses up to 10 mM. In another study, Hikiba et al. (28) assessed the effect of iodine and iodoform on chromosome aberrations using Syrian hamster embryo (SHE) cells and found that iodine induced chromosome aberrations and iodoform induced no genotoxicity. Using the comet assay and chromosome aberration test to characterize the genotoxic potency of povidone-iodine within 4 h of contact with CHO-K1 cells, Muller et al. (29) found no chromosomal damage. In another study, Hedayati et al. (30) showed that incubation of lymphocytes with (131)I induced genotoxicity, which was reflected by an increase in micronuclei frequency. Genotoxicity of intracanal medicaments Calcium hydroxide Calcium hydroxide [Ca(OH)2 ] was originally introduced to the field of endodontics by Herman in 1920 as a pulp-capping agent. It is a white odorless powder with the formula Ca(OH)2, and a molecular weight of 74.08 (31). Calcium hydroxide has low solubility in water (about 1.2 gL-1 at 25 C), which decreases as the temperature rises. The dissociation coefficient of Ca(OH)2 (0.17) permits a slow, controlled release of both calcium and hydroxyl ions. The low solubility is a good clinical characteristic as a long period is necessary before it becomes soluble in tissue fluids when in direct contact with vital tissues (32). It has a high pH (about 12.5-12.8), is insoluble in alcohol and is chemically classified as a strong base, it main actions come from the ionic dissociation of Ca2+ and OH- ions and their effect on vital tissues, generating the induction of hard tissue deposition and being antibacterial. Ca(OH)2 dissociates into calcium and hydroxyl ions on contact with aqueous fluids. Ca (OH)2 in water has a thixotropic behavior (33). According to Ribeiro et al. (34) calcium hydroxide do not promote DNA damage in mammalian cells. In another study, Ribeiro et al. (35) revealed that calcium hydroxide was not able to modulate alkylation-induced genotoxicity or oxidative DNA damage as depicted by the single cell gel (comet) assay. MTA MTA is a mixture of a refined Portland cement and bismuth oxide and trace amounts of SiO2, CaO, MgO, K2SO4, and Na2SO4 (36). Portland cement is a mixture of dicalcium silicate, tricalcium silicate, tricalcium aluminate, gypsum, and tetracalcium aluminoferrite (37). Gypsum, and to a lesser extent, tetracalcium aluminoferrite are important determinant of setting time (37). MTA contains fewer toxic heavy metals, has a longer working time, and have undergone additional processing/purification than regular Portland cements (36). The MTA powder is mixed with supplied sterile water in a 3:1 powder/liquid ratio and it is recommended that a moist cotton pellet be temporarily placed in direct contact with the material and left until a follow-up appointment (38). Upon hydration, MTA materials form a colloidal gel that solidifies to a hard structure in approximately 3–4h, with moisture from the surrounding tissues purportedly assisting the setting reaction (38). Hydrated MTA has an initia l pH of 10.2, which rises to 12.5 three hours after mixing (39). Using single cell gel (comet) assay, Ribeiro et al. (40) detected no DNA damage after a treatment of cells by MTA and Portland cements for concentrations up to 1000  µ/ml. In another study, Ribeiro et al.(41) demonstrated that regular and white MTA did not produce genotoxic effects at 1 to 1000  µgmL-1 FOR 3 H AT 37 C. Another study using Chinese hamster ovary (CHO) cells indicated that that MTA and Portland cements are not genotoxins and are not able to induce cellular death (42). Braz et al. (43) assessed the genotoxic effects of MTA and Portland cements in peripheral lymphocytes from 10 volunteers by the alkaline single cell gel (comet) assay. Findings failed to detect the presence of DNA damage after a treatment of peripheral lymphocytes by MTA and Portland cements for concentrations up to 1000 mug mL(-1). Camargo et al. (44) revealed that regular and white MTA preparations did not negatively influence cell survival or reactive oxygen species production. Ding et al. (45) show ed that MTA and calcium silicate possessed no genotoxic effect. According to Zeferino et al. (46) MTA as well as Portland cement+15% bismuth oxide were not genotoxic. Genotoxicity of root canal sealers For assessment of the genotoxic potential of any material, it is recommended to perform a series of in vitro tests. At least two assays, investigating different endpoints, shall use mammalian cells. For cytotoxic and bactericidal compounds, as many endodontic  sealers appear to be, care must be taken in the test set up: For a proper evaluation the selected test concentrations used for genotoxic effects must be below the concentrations where toxic effects are found (47). Ørstavik and Hongslo (48) showed that extracts of a synthetic polymer material, based on epoxy-bis-phenol A, induced mutations in Salmonella typhimurium TA 100 as did extracts of the epoxy-bis-phenol A resin alone. Formaldehyde, an active ingredient from one of the ZnO-based materials, induced mutations in both Salmonella typhimurium TA 98 and TA 100. The mutagenic activity of formaldehyde as well as of the epoxy material was reduced in the presence of rat liver microsomes. Schwikl et al. (49) showed that eluates of mixed AH26 were mutagenic, and their genotoxicity was strongly depended on the setting time. The number of mutants after exposure to eluates of unset AH26 was enhanced approximately 7- to 10-fold. However, the mutagenic activity of the mixed material was clearly reduced after a setting time of 1 wk. Physiological saline eluates of the mixed AH26 were not found to be mutagenic. Dimethyl sulfoxide eluates of the liquid component of AH26 elicited mutagenic effects similar to the freshly mixed material; eluates made in physiological saline were barely mutagenic at a 10-fold higher concentration. Leyhausen et al. (50) showed that AH-Plus revealed no genotoxicity and mutagenicity. Epoxy-based sealers are also mutagenic in mammalian cell mutation assays. Ersev et al. (51) showed that silver-free AH26 set for 24 h were weakly mutagenic in Salmonella typhimurium TA100. They further showed that silver-free AH26 might contain small amounts of two mutagenic substances: bisphenol A diglycidyl ether and formaldehyde. Tai et al. (52) revealed that root canal sealers containing formaldehyde and bisphenol A diglyether proved to be not only cytotoxic but also genotoxic. Miletic et al. (53) found no mutagenicity found for AH26 and AH Plus sealers on human lymphocytes in highly controlled conditions in vitro. Formaldehyde is released from some epoxy-based sealers with a maximum after 2 days, even though the amount is much less than that of paraformaldehyde containing zinc oxide-eugenol sealers (54). It was believed that the leakage of formaldehyde and bisphenol- A diglycidyl ether from the epoxy-sealers contributed to the mutagenic effects (49, 55). Formaldehyde is classified as a carcinogen in animals, whereas there exists only limited evidence for carcinogenic effects in man (56). There is also limited evidence for animal carcinogenicity from bisphenol-A diglycidyl ether and no adequate data for the evaluation of human cancer risk for this compound (57). Considering the limited exposure of these compounds from endodontic epoxy sealers and the lack of definitive assessment by the IARC, it seems unlikely that such sealers contribute to an increased risk of cancer in patients. However, the high level of paraformaldehyde in zinc oxide-eugenol. Using Comet assay, Huang et al. () showed that the zinc oxide eugenol-based sealers  (Canals, Canals-N, and Tubilseal) did not always cause a dose-dependent increase in genotoxicity. The resin-based sealers (Topseal, AH 26, and AH Plus) caused a dose-dependent increase in genotoxicity, but no such effect was seen with the calcium hydroxide-based sealer (Sealapex) (47).