Madbury vs Madison and Mc Collough vs Maryland Essay

Madbury vs Madison and Mc Collough vs Maryland - Essay Example Marbury filed a suit before the Supreme Court on its original jurisdiction and prayed for a writ of Mandamus to be passed, ordering Madison to deliver him the signed commission (Levinson and Balkin 3). The questions or legal issues that were to be decided in this case were, whether the applicant had a right to the commission he demanded, whether the country can afford him a remedy and lastly, whether the remedy provided by the court will be in the form of Mandamus (William Marbury vs. James Madison). The case arose out of the dispute between two political parties, which were the Federalists, primarily led by Alexander Hamilton on the one hand and on the second hand the Republicans, led by Thomas Jefferson, James Madison and others (Levinson and Balkin 3). Jefferson and fellow Republicans were not pleased with the Federalists, who were trying to safeguard their political power by packing the court with their own men before they left their office. The Republicans vowed to fix the wrong which had been done by Republicans (Mountjoy & Mc Neese 27-28). This ultimately led to the battle in the form of Madbury vs. Madison in the US Supreme Court, Now coming to the case of Mc Culloch vs. Maryland, the parties to this suit were Mc Culloch who is the Appellant in this case, whereas, the State of Maryland is the defendant (Mc Culloch vs. Maryland). The State of Maryland had enacted a statute imposing a tax on all the banks, which were operating in Maryland and were not chartered by the state. The statute provided that all such banks will not have the power to issue note and can only issue them by purchasing the paper to be issued by the state (Mc Culloch vs. Maryland). The cashier of the Baltimore branch of the second bank of the United States, which was established by the 1816 Act of the Congress, issued bank notes without complying with the Maryland law. Maryland sued Mc Culloch to pay taxes and Mc Culloch contested the constitutionality of the Act (Mc Culloch vs. Maryla nd). The issues, in this case, were whether the Congress had the power to incorporate a bank, even when the power is not specifically stated by the constitution and whether the State of Maryland had the power to tax an institution created by its own power granted by the constitution (Mc Culloch vs. Maryland). The Supreme Court held in this case that the Congress had power under the Constitution to incorporate a bank, that the State of Maryland did not have the power to tax an institution created by the Congress pursuant to its powers under the constitution and the Act passed by Maryland to levy taxes was unconstitutional (Mc Culloch vs. Maryland). Despite the fact that the above two cases are distinct and stretched over two different time period, having different subject matter and facts, the two cases have certain things in common. Firstly, both the cases were on constitutional law and required interpretation of the constitution. Secondly, both cases were initiated in the same peri od of time, which is the early 19th century. Thirdly, both the cases had supreme importance and were landmark cases in the history of the United States, in the sense that both the cases decided important issues.

Financial Checkup Assignment Example | Topics and Well Written Essays - 750 words

Financial Checkup - Assignment Example The figures clearly indicate that I am credit worth as my assets are capable of covering my credit. In addition, it shows that I understand how to manage my debts as I keep the levels of debts below what I really own (Assets).The figures can be helpful when seeking short term credit to handle my short term needs (Eisenberg 69). According to my income and expense statements, the total expense is $2750 while my income is $900.The total loss is $1840.From this figures, my total expense exceed the total income resulting in a loss. This may be attributed to the fact that being a student, there is little time to engage in income generating activities but there is extensive spending due to a number of requirements in the learning institution and my personal needs. However, my income of 900 dollars show that I am capable of managing my time and engage in part time income generating activities , which clearly indicate that I can utilize time as a major resource in making substantive income(Eisenberg 62). My liquidity ratio is 2.92,which is below the recommended ratio of 3.The ratio shows that my liquid assets cannot meet my current expenses by a difference of 0.8.This can be attributed to the fact that as a student, I am bound to spent more than what I hold as liquid assets. However, the figure is comparatively positive compared to other students as it shows that I can meet most of my current expenses using my own cash and cash equivalents. Further, the figure is not alarming as I can still manage to get external source of cash such as pocket money from parents to cover the current expenses that I may be unable to meet on my own (Eisenberg 33).The debt asset ratio is 0.72.This figure is below 1, which clearly indicates that my assets exceed my debts and so I can pay my debts. Further, the figure shows that I am credit worth when borrowing or applying for a loan. My monthly average amount for revolving savings is$417.This average budgeted amount for every moth show

Security in Wireless Protocols Essay Example | Topics and Well Written Essays - 750 words

Security in Wireless Protocols - Essay Example Some of these risks are similar to those of wired networks; some are aggravated by wireless connectivity; some are new. The important basis of risks in wireless networks is that the medium, the atmosphere, is open to all including the malicious intruders. Maintaining a secure wireless network is a continuous task that needs better effort than that needed for other networks and systems (Karygiannis and Owens, 2002). 802.11 standards: The Institute of Electrical and Electronics Engineers (IEEE) in the year 1997 created the first WLAN standard and it was named 802.11. However, soon the disadvantage of using 802.11 came up and it was found that 802.11 only supported a maximum network bandwidth of 2 Mbps. As a result the data transfer was too slow for most applications (Mitchell, 2008). Concerning the security aspect, 802.11 use the shared secret key and this in turn helps a hacker decrypting any of the 802.11 frames. Normally 802.11 dont supply any functions that support the exchange of keys among stations. Because of that, system administrators and users usually use the same keys for weeks and even months together. This gives malicious offenders ample of time to observe and hack into WEP-enabled networks (Geier, 2002). The IEEE 802.11 specification recognized many services to offer a safe operating background. The protection services are offered mainly by the Wired Equivalent Privacy (WEP) protoc ol to secure link-level data during wireless transmission between clients and access points. WEP does not provide total security, except only for the wireless portion of the connection. RC4-based stream encryption algorithm is used for confidentiality, verification, and integrity (Karygiannis and Owens, 2002). 802.11b: As the technology advanced IEEE expanded on the original 802.11 standard in July 1999 and created the 802.11b specification. It was found that 802.11b supports high bandwidth up to 11 Mbps when compared to traditional Ethernet. Similar to 802.11, 802.11b

Madbury vs Madison and Mc Collough vs Maryland Essay

Madbury vs Madison and Mc Collough vs Maryland - Essay Example Marbury filed a suit before the Supreme Court on its original jurisdiction and prayed for a writ of Mandamus to be passed, ordering Madison to deliver him the signed commission (Levinson and Balkin 3). The questions or legal issues that were to be decided in this case were, whether the applicant had a right to the commission he demanded, whether the country can afford him a remedy and lastly, whether the remedy provided by the court will be in the form of Mandamus (William Marbury vs. James Madison). The case arose out of the dispute between two political parties, which were the Federalists, primarily led by Alexander Hamilton on the one hand and on the second hand the Republicans, led by Thomas Jefferson, James Madison and others (Levinson and Balkin 3). Jefferson and fellow Republicans were not pleased with the Federalists, who were trying to safeguard their political power by packing the court with their own men before they left their office. The Republicans vowed to fix the wrong which had been done by Republicans (Mountjoy & Mc Neese 27-28). This ultimately led to the battle in the form of Madbury vs. Madison in the US Supreme Court, Now coming to the case of Mc Culloch vs. Maryland, the parties to this suit were Mc Culloch who is the Appellant in this case, whereas, the State of Maryland is the defendant (Mc Culloch vs. Maryland). The State of Maryland had enacted a statute imposing a tax on all the banks, which were operating in Maryland and were not chartered by the state. The statute provided that all such banks will not have the power to issue note and can only issue them by purchasing the paper to be issued by the state (Mc Culloch vs. Maryland). The cashier of the Baltimore branch of the second bank of the United States, which was established by the 1816 Act of the Congress, issued bank notes without complying with the Maryland law. Maryland sued Mc Culloch to pay taxes and Mc Culloch contested the constitutionality of the Act (Mc Culloch vs. Maryla nd). The issues, in this case, were whether the Congress had the power to incorporate a bank, even when the power is not specifically stated by the constitution and whether the State of Maryland had the power to tax an institution created by its own power granted by the constitution (Mc Culloch vs. Maryland). The Supreme Court held in this case that the Congress had power under the Constitution to incorporate a bank, that the State of Maryland did not have the power to tax an institution created by the Congress pursuant to its powers under the constitution and the Act passed by Maryland to levy taxes was unconstitutional (Mc Culloch vs. Maryland). Despite the fact that the above two cases are distinct and stretched over two different time period, having different subject matter and facts, the two cases have certain things in common. Firstly, both the cases were on constitutional law and required interpretation of the constitution. Secondly, both cases were initiated in the same peri od of time, which is the early 19th century. Thirdly, both the cases had supreme importance and were landmark cases in the history of the United States, in the sense that both the cases decided important issues.

Security in Wireless Protocols Essay Example | Topics and Well Written Essays - 750 words

Security in Wireless Protocols - Essay Example Some of these risks are similar to those of wired networks; some are aggravated by wireless connectivity; some are new. The important basis of risks in wireless networks is that the medium, the atmosphere, is open to all including the malicious intruders. Maintaining a secure wireless network is a continuous task that needs better effort than that needed for other networks and systems (Karygiannis and Owens, 2002). 802.11 standards: The Institute of Electrical and Electronics Engineers (IEEE) in the year 1997 created the first WLAN standard and it was named 802.11. However, soon the disadvantage of using 802.11 came up and it was found that 802.11 only supported a maximum network bandwidth of 2 Mbps. As a result the data transfer was too slow for most applications (Mitchell, 2008). Concerning the security aspect, 802.11 use the shared secret key and this in turn helps a hacker decrypting any of the 802.11 frames. Normally 802.11 dont supply any functions that support the exchange of keys among stations. Because of that, system administrators and users usually use the same keys for weeks and even months together. This gives malicious offenders ample of time to observe and hack into WEP-enabled networks (Geier, 2002). The IEEE 802.11 specification recognized many services to offer a safe operating background. The protection services are offered mainly by the Wired Equivalent Privacy (WEP) protoc ol to secure link-level data during wireless transmission between clients and access points. WEP does not provide total security, except only for the wireless portion of the connection. RC4-based stream encryption algorithm is used for confidentiality, verification, and integrity (Karygiannis and Owens, 2002). 802.11b: As the technology advanced IEEE expanded on the original 802.11 standard in July 1999 and created the 802.11b specification. It was found that 802.11b supports high bandwidth up to 11 Mbps when compared to traditional Ethernet. Similar to 802.11, 802.11b

Elementary School Literature Class Essay Example for Free

Elementary School Literature Class Essay The biography genre allows the reader to learn about the events in the life of a non-fictional character. An example would be the book Rocks in His Head by Carol Hurst. After reading the text, the students may then be required to complete a character biography which would outline personal information about the character, interesting information about him, important dates mentioned in the text, his name, where he lived, and such. a)  Ã‚  Ã‚  Ã‚  Ã‚   Fable The fable genre introduces things which are given human qualities as characters. Fables often contain moral lessons. An example of a fable would be Aesop’s fable of The Boy Who Cried Wolf. Students may then be asked to fill out a dissection chart wherein they will have to describe scenes corresponding to the different parts of the story, such as conflict, resolution, moral, etc. b)  Ã‚  Ã‚  Ã‚  Ã‚   Fairy Tale Fairy tales are fictional stories which often have magical elements integrated into the story. An example would be Hans Christian Andersen’s Thumbelina. A story map would be one applicable graphic organizer which would require the students to map out the beginning, purpose, conflict, most important moment, and conclusion of the story. c)  Ã‚  Ã‚  Ã‚  Ã‚   Folktales Folktales are stories which are grounded on the cultural tradition of a particular place. The story of Johnny Appleseed is one popular American folktale. A venn diagram may be used to graphically organize the information learned from the story. d)  Ã‚  Ã‚  Ã‚   Historical Fiction Historical fiction is a sub-genre of fiction. It portrays fictional stories of historical figures or events. An example would be the book The Mary Celeste written by Jane Yolen and Heidi Stemple. A time line may be used as a graphic organizer in the case of historical fiction stories. e)  Ã‚  Ã‚  Ã‚  Ã‚   Informational Text or Nonfiction Informational texts are non-fiction texts which give the reader current and accurate information regarding a particular topic. Secrets of a Civil War Submarine by Sally M. Walker talks about the disappearance of the first submarine to sink an enemy ship in the Civil War and is a leading example of an informational text. For this purpose, a map may be accomplished by the student plotting out the problem and solution found in the informational text. KWLs are also popular organizers for informational texts. f)  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Mystery Mystery texts involve the solving of puzzles or crimes by the characters in the text. There are several series which involve mystery plots such as Nancy Drew and Babysitter’s Club. With this genre, charts may be used after the reading of the text requiring students to fill out information regarding the characterization of the hero, the villain, the victim, the crime or problem and the solution. g)  Ã‚  Ã‚  Ã‚  Ã‚   Picture books Picture books provides verbal and visual narratives of the plot and story. Maurice Sendak’s Where the Wild Things Are is a good example of a picture book. The text is quite simple and sparse but the blend with the visual narrative makes for better communication of the author’s intention. A character analysis or a plot diagram may be accomplished by the student after reading a picture book. h)  Ã‚  Ã‚  Ã‚  Ã‚   Poetry Poetry depicts a concept or story through a particular form. A famous children’s literature poet is Shel Silverstein. Some of his more popular works are The Missing Piece Meets the Big O and The Giving Tree. Since poems are more complex than story-telling texts, a plot diagram would be a good graphic organizer for students to accomplish. i)  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Realistic Fiction Realistic fiction presents fictional characters, plot and settings but depict them in such a way that they could be found in real life. There are many examples of this genre such as Are You There God? It’s Me Margaret by Judy Blume. The challenge is for the author to create a story addressing a concern or issue of the target reader audience. Given the purpose of realistic fiction, a character analysis may be completed by the student along with an analogy for what the student would do if they were in the same situation. 7. Design a literature lesson plan to include the following categories: grade, 2 behavioral objectives (Sunshine State Standards), 2 activities, 1 assessment instrument, and 1 follow-up homework assignment. Include the title of the book and its genre. This is a literature lesson plan for a second grade class. One picture book will be used as class reading material, in this case Maurice Sendak’s Where The Wild Things Are, and several wordless picture books will be provided for the students’ activities. One objective of the lesson is to teach students the various character perspectives that may be employed in telling a story and to have the students apply this learning in the activities. Another objective is to have the students exercise and display their creative talents, particularly their writing skills through the creation of their own story. At the beginning of the lesson the picture book will be read to the students. After the reading of the text, the students will be asked to complete a character diagram for each of the main characters involved in the text. They will be asked to map out the descriptions of the characters as well as the activities which the character actually engaged in throughout the story. This will not only allow the instructor to assess the students’ understanding of the story but it will allow for a better platform for discussing how character perspectives can be used in telling a story. The students will thus be asked to engage in an activity of shifting the character perspectives in the book so that the narrative is told from a first, second or third person perspective. This will be done by focusing on particular scenes in the picture book used for storytelling. Having in mind their description of the characters, the students will be asked to change the text corresponding to the scene pinpointed so that it would be in first, second or third person perspective. Further application of the lesson will be engaged in by having the students break off into groups. Each group is to take a wordless picture book. They will then be asked to draw a piece of paper from a hat. The strip of paper will indicate in what perspective the text of the narrative should be told. The students will then be asked to write a simple narrative for the wordless picture book. One line narrations for each picture would be deemed sufficient. The students would be informed that although creativity in formulating the text would be incentivized, what is more important is the proper use of the perspective as well as the grammatical correctness of the work. At the end of the class the students will submit the completed story. Before dismissal, the instructor will make copies of the students’ stories. The stories of the different groups will be switched so that each student is left with a copy of a story completed by another group. As an assignment, the students will be asked to shift the perspective of the story assigned to them. They are informed that they may vary the manner in which the story was told as long as they maintain the same framework for the narrative and as long as they are able to use a perspective other than that which was used.

Effect of Microhardness on Chemical Degradation

Effect of Microhardness on Chemical Degradation Abstract Objective: The aim of this study was to evaluate the effect of chemical degradation media associated with brushing on surface roughness (Ra) and Knoop microhardness (KHN) analyses of different composites. Material and Methods: Eighty specimens were prepared for each composite: Grandio SO (Voco), Amaris (Voco), Filtek Supreme (3M/ESPE), Filtek LS (3M/ESPE). The specimens were divided into four groups according to the immersion in chemical degradation media for 7 days: artificial saliva (control), heptane, 0.02M citric acid, 70% ethanol. The surface of specimens was submitted to 10950 brushing cycles (200g load) in an automatic tooth-brushing machine with abrasive slurry. Surface roughness and microhardness measurements were obtained at baseline, after immersion in chemical degradation media and after brushing. Data were submitted to three-way repeated measures ANOVA and Tukey’s test (pResults: The KHN means for composites were: Grandio (153.5 ±35.9)a, Filtek Supreme (87.0 ± 24.9)b, Amaris (64.5 ±24.5)c, LS (69.0 ±15.3)c; for storage media: artificial saliva (97.3 ±46.7)a, ethanol (93.3 ±49.9)a, citric acid (95.8 ±42.1)a, heptane (87.6 ±36.7)b; and after treatments: after chemical degradation (104.8 ±49.7)a, baseline (93.8 ±42.5)b, after brushing (81.9 ±36.5)c. The Ra results for composites were: LS (0.15 ±0.25)a, Grandio SO (0.19 ±0.24)ab, Filtek Supreme (0.20 ±0.22)ab, Amaris (0.23 ±0.37)b; for storage media: artificial saliva (0.18 ±0.31)a, heptane (0.18 ±0.25)a, ethanol (0.20 ±0.26)a, citric acid (0.21 ±0.28)a; and after treatments: brushing (0.11 ±0.14)a, after chemical degradation (0.23 ±0.32)b, baseline (0.24 ±0.32)b. Conclusions: Brushing after chemical degradation reduced surface roughness values. In general, chemical degradation did not affect composites roughness, but microhardness was significantly reduced. Heptane produced the biggest reduction in composites microhardness. Clinical Relevance: The food-simulating solutions and brushing simulating alter the composites properties, and these alterations are material-dependent. Keywords: composites, chemical degradation, brushing, Knoop microhardness, surface roughness. Introduction Improvements on the composition and mechanical properties of resin-based materials along with increased esthetic demands have resulted in the enlarged use of direct composite restorations in anterior and posterior teeth [1,2]. These improvements provided more strength and durability to the composite restorations under the conditions of the oral environment. Most of the available composites contain a polymer matrix of dimethacrylate monomers, such as Bis-GMA, UDMA, and TEGDMA (organic phase), inorganic filler particles (dispersed phase) coated with a methyl methacrylate-functional silane coupling agent to bond the filler to the organic matrix, a photoinitiator system to allow photoactivation by light units and other minor additions including polymerization initiators, stabilizers and coloring pigments [3-5]. However, the critical oral environment conditions (pH changes or humidity) may increase the composite biodegradation over time [6]. Under oral conditions, dental materials may be exposed either intermittently or continuously to chemical agents present in saliva, food and beverages [1]. Previous studies have shown that some dietary foods and beverages can cause surface degradation of restorative materials [7-14]. Their constituents can soften the organic phase and promotes disintegration of the dispersed phase, altering the surface hardness [1,15]. Besides of chemical environment, the toothbrushing is another condition that influences the longevity of composites restorations in vivo. Although toothbrushing plays an important role in oral hygiene, the effects of abrasion constitutes another important issue on dental materials wear processes, which can result in alterations in surface roughness, loss of contour, staining and plaque retention [16]. There are several types of composites nowadays, such as nanohybrid, nanofill and microhybrid, which have the similar polymer matrix composition. However, the inorganic phase (size, type and distribution of filler particles) are different. Therefore, the effects of chemical degradation liquids and toothbrushing on surface roughness and microhardness of these types of composites must be reported. Thus, the aim of this study was to evaluate the effects of chemical degradation associated with toothbrushing on surface roughness and microhardness of different composites. The null hypothesis tested was that the immersion in chemical degradation media and brushing are not able to modify the surface roughness and microhardness of the tested materials. Material and Methods Specimens preparation Eighty cylindrical specimens of each composite were fabricated (shade A3) using a metallic matrix with 2 mm in height and 3 mm in diameter. A mylar strip was placed over the composite and pressed with a glass plate to provide a flat surface, being removed after curing. The composites were applied in increments of 2 mm and cured on the top surface using LED photocuring unit (Elipar Freelight 2, 3M/ESPE, St. Paul, MN, USA) at 1200 mW/cm2 power density, activated for 40 s. After curing, they were stored in individual containers with deionized water for 24 h. Then, they were polished using a sequence of 1200, 2400 and 4000 grit aluminum oxide abrasive disks (Extec, Enfield, CT, USA) in a polishing device (DP-10, Panambra, Sà £o Paulo, Brazil). After polishing, all the specimens were immersed in deionized water at 37  ºC for 24 h. Four direct restorative materials were tested, as described in Table 1. Knoop microhardness measurements The microhardness measurement was performed with a microhardness tester (FM-700, Future-Tech, Tokyo, Japan), Knoop tip, under 25 g load for 10 s. Three indentations were performed 100  µm apart from each other, at the surface of the specimens. The means were determined as Knoop Hardness Number (KHN). Surface roughness analysis The mean surface roughness (Ra) was evaluated using a profilometer (MaxSurf XT 20, Mahr, Goettingen, Germany). The diamond stylus moved 2.5 mm long starting the first measurement 0.2 mm from the lower area of specimen. Three profile measurements were performed for each specimen at intervals of 0.25 mm and a final average was used. The mean Ra values were determined with a cut-off value of 0.8 mm, a transverse length of 0.8 mm, and a stylus speed of 0.1 mm/s. Chemical degradation media immersion The specimens of each composite were randomly divided according to the food-simulated substances tested (n=20). The solutions tested are mediums recommended by FDA (1976) to be used as food-simulating liquids [17]. Heptane P.A. (Synth – Labsynth, Diadema, Sà £o Paulo, Brazil) was used to simulate butter, fat meals and vegetable oils. Citric acid 0.02M (Synth) simulated beverages, vegetables, fruits and candies. Ethanol 70% (Zulu Hospitalar 70% Companhia Nacional de à lcool, Piracicaba, Sà £o Paulo, Brazil) simulated alcoholic beverages and mouthrinses. Artificial saliva was used as control and prepared according to Gohring et al. [18] using 22.1 mmol/l hydrogen carbonate, 16.1 mmol/l of potassium, 14.5 mmol/l sodium, 2.6 mmol/l hydrogen phosphate, 0.8 mmol/l boric acid, 0.7 mmol/l calcium, 0.4 mmol/l thiocyanate and 0.2 mmol/l magnesium. The specimens were kept in individual vials with 2 ml of each solution for 7 days at 37  ºC. After this period, the specimens were washed thoroughly, and stored in deionized water at 37  ºC, for 24 h. The microhardness and surface roughness were evaluated. Brushing protocols Subsequently, the experimental units were subjected to brushing abrasion in an automatic toothbrushing (TB) machine (ODEME Biotechnology – Joaà §aba, Santa Catarina, Brazil) which imparted reciprocating motion to 6 soft bristle toothbrush heads (Sanifill Ultraprofissional, Hypermarcas – Sà £o Paulo, Brazil). This apparatus provides linear brushing movements across the specimens at a speed of 120 cycles per min at 37 °C, with a double pass of the brush head over the surface. The top surface of resin composites cylinders were submitted to 10950 brushing stokes under a vertical load of 200 g with abrasive slurry, simulating one year of clinical situation [19]. The abrasive slurry consisted of fluoridated dentifrice (Colgate Tripla Aà §Ãƒ £o, Colgate-Palmolive, Sà £o Paulo, Brazil) and artificial saliva, in a ratio of 1:3, by weight [20]. Toothbrushes were replaced after the completion of each brushing cycles. After brushing, the specimens were kept in deionized water at 37 ºC, for 24 h. At the end of this protocol, the microhardness and surface roughness was obtained. Statistical analysis This experiment followed a factorial scheme of the 4x3x4 type. The experimental variables under study were composites [Grandio, Amaris, Filtek LS, Filtek Supreme], time [baseline, after chemical degradation (CD) and after brushing (TB)] and the food-simulating media [artificial saliva (AS), heptane (H), citric acid (CA) and ethanol (E)]. The variable responses were the mean roughness measurement value obtained in profilometer, and the average of three microhardness readings. Data were submitted to statistical analysis using the computer software Statistica for Windows (Statsoft, Tulsa, OK, USA). The inferential statistics consisted of three-way repeated measures ANOVA (composites, time, and chemical degradation media), in which the variable time was considered as a repeated factor, followed by Tukey’s test. The level of significance was the conventional value of 5%. Results Microhardness evaluation The mean KHN values of the composites after chemical degradation media are shown in Figure 1. The application of RM-ANOVA showed significant differences for the factors composites (p=0.0001), time (p=0.0001) and chemical degradation (p=0.0001). Grandio SO composite presented the highest KHN values for all times tested. Amaris and Filtek LS exhibited values significantly lower than Filtek Supreme and Grandio SO (Table 2). For the chemical degradation media factor, the immersion in heptane produced the lowest microhardness means, compared to the other tested media (Table 3). Regarding the different times, the microhardness (KHN) values significantly increased after immersion in chemical degradation media and decreased after brushing, compared to baseline means (Table 4). Surface roughness analysis The means of roughness surface (Ra) for the composites are shown in Figure 2. The application of RM-ANOVA showed no significant differences for composite (p=0.034) and time (p=0.626) factors. The roughness means obtained for Amaris composite were significantly higher than Filtek LS. Grandio SO and Supreme exhibited intermediate means (Table 2). For the chemical degradation media, no significant differences were obtained for surface roughness (Table 3). The Ra means after brushing were lower than at baseline and after chemical degradation CD (Table 4). Discussion The chemical environment is one aspect of the oral conditions which has an appreciable influence on the in vivo degradation of composites [21]. Some chemicals substances from food and drinks can lead to surface degradation of composite restorations, resulting in unaesthetic appearance and increased surface roughness, accelerating the wear of dental materials [22,23]. This degradation is mainly due to the softness of composite matrices with exposure to organic acids and various food and liquid constituents [24,25,12]. Previously published studies have reported that acidic conditions show a tendency to degrade glass ionomer cements, polyacid modified composite resins, and composite resins [9,26,10,27,11]. The present study was performed to investigate the Knoop microhardness and surface roughness of four composites, before and after simulating oral conditions. Hardness is defined as the resistance to permanent indentation or penetration [28,1]. It is used to predict the wear resistance of a material and its ability to cause abrasion opposing tooth structure [28]. The composites exposed in food-simulating media can suffer chemical softening, reducing their physico-mechanical properties. Changes in the composite hardness usually occur within the first 7 days after exposure to chemical solutions [21]. Therefore, this study conducted the initial readings of the hardness in the specimens after post-cure [1], and another reading after the exposure period of immersion. In the present study, specimens stored in heptane showed significantly reduction in microhardness, as also observed previously [14,28]. Heptane simulates butter, fatty meals and vegetables oil [14,1] and may damage the resin matrix,[12,28] producing cracks in the interface, and consequently, weakening the material.[14] It is questioned if alcohol-containing beverages may compromise the longevity of composites restorations [29], since it presents the potential of damaging polymers [1,12], by fully penetrating the resin matrix and promoting the release of unreacted monomers [13]. The partial dissolving of the resin matrix may result in the degradation of the filler-matrix interface, thereby impairing the flexural strength and hardness [14]. In this study, the concentration of ethanol solution (70%) was used according to previous [28] but it showed no significant effect in the microhardness of composites. The differences in hardness values compared to previous studies could be related to the surface characteristics of the composites, filler distribution and conversion rate [30]. Furthermore, the period of 24 h of storage before immersion in ethanol may lead to complete polymerization of the composites, reducing the presence of unreacted monomers on the surface [1,14]. The effects of intraoral organic acids, as citric acid, besides producing tooth erosion, can cause surface degradation of composites [9], favoring the breaking of bonds in Bis-GMA molecules of composites [24,11]. Despite of others studies that citric acid reduced the hardness of composites [7,9], in this study no differences were observed in the microhardness of the composites when immersed in citric acid for 7 days. Nevertheless, the period of storage may have been insufficient to promote differences in the mechanical properties of the specimens’ surface [7,14]. Differences in microhardness means among the composites exposed to the tested solutions were found and are related to their composition and particle content [14,29]. Grandio SO, Filtek Supreme and Amaris have similar matrix composition (Bis-GMA, UDMA, TEGDMA), however, differ in size and amount of filler particles (Table 1). The higher resistance of Bis-GMA to the degradation effects of immersion media can be explained by the fact that bis-acryl resin composite materials contain bifunctional acrylates, which cross-link to provide increased mechanical strength and resistance to weakening in the presence of solvents [28,31]. Grandio SO and Filtek Supreme present nanoscale particles, which provide better mechanical resistance compared to hybrid resins, superior polishing than microfilled resins, higher strength and reduced polymerization shrinkage [32]. Due to their nanoscale, these materials showed the highest microhardness values in this study. By the other hand, Filtek LS is constituted of silorane, with quartz and yttrium fluoride as inorganic filler, which increased hydrophobicity and reduced water sorption [33]. Differences in microhardness among Filtek LS and others composite could be attributed to the lower filler content (76% w/w), as observed by Yesilyurt et al. [14]. Therefore, the differences in composites compositions could have contributed to the differences in hardness. After simulated toothbrushing, there was a reduction in microhardness values. This fact may be due to changes on the surface of the resin matrix when immersed in the solutions before brushing. According to a previous study [2], the immersion in food-simulating media increased the exposure of filler particles by softening the matrix. Additionally, toothbrushing can change the surface of composites [2,34,35]. In clinical situation, the consumption of food or beverages occurs before brushing habits, making this association clinically relevant. Although an increase of the composite surface roughness and degradation after brushing have been previously reported,[2] significantly lower roughness means were obtained after brushing in this study. Likewise, previous studies showed that most of composites did not present significant changes by the immersion on chemical degradation media in surface roughness over time [2,9,15]. This study found differences on surface roughness of mycrohybid, nanofill and nanohybrid composites, as results of their differences in their compositions. Filtek LS, myycrohybrid composite, had the lowest surface roughness, probably due to low filler content. Filtek Supreme e Grandio SO had an intermediate smoother texture, whereas Amaris showed the roughest surface. Nevertheless, despite of these initial differences, the immersion in chemical solutions did not interfere in the final surface roughness. However, interaction between immersion in food-simulating media and simulated brushing decreased surface roughness, as observed by Turssi et al. [20] This may be attributed to the reaction of the solutions with the polymer matrix. Toothbrushing after the immersion on food-simulating media resulted in the removal of part of the organic matrix around the loosen fillers [2]. Then, the softened matrix have become mixed with the abrasive slurry, decreasing its abrasive potential [20]. Roughness surfaces of composite favors the accumulation of plaque, gingival inflammation, superficial staining and secondary caries. It is noteworthy that the effect of brushing on the composites depends on several factors, such as the type of toothpaste, type and shape of the brush bristles, the proportion of deionized-water solution, as well as speed and weight applied during simulation process. As these parameters were standardized for all groups, it can be suggested that the surface roughness varies with the size, hardness and percentage of composite particles, as reported previously [20,36]. The different treatments tested resulted in alteration of composite properties, and these alterations were material-dependent; thus, the null hypothesis tested was rejected. The present study is important for guiding the improvements of the present composite resins against the challenges they will face during clinical service. It is also relevant to state that esthetics represents only one of the reasons for composite resin restorations failure. Improvements in other areas such as bonding degradation, material deterioration and ability to prevent caries progression/activity should be also considered. Conclusion According to the limitations of this study, it can be concluded that: The microhardness means of the tested composites were influenced by the material; Toothbrushing reduced Ra values of the materials tested, but the solutions used for chemical degradation did not affect the results. Conflict of Interest The authors declare that they have no conflict of interest.