DOCSLIB.ORG

Fluorine and Fluorides

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Fluorine and Fluorides This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Pro- gramme, the International Labour Organisa- tion, or the World Health Organization Environmental Health Criteria 36 FLUORINE AND FLUORIDES Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Orgaiization- World Health Organization 77, Geneva, 1984 The International Programme on Chemical Safety (IPCS) is a joint venture of the United Nations Environment Programme, the Interna- tional Labour Organisation, and the World Health Organization. The main objective of the IPCS is to carry out and disseminate evaluations of the effects of chemicals on human health and the quality of the environment. Supporting activities include the development of epidemiological, experi- mental laboratory, and risk-assessment methods that could produce inter- nationally comparable results, and the development of manpower in the field of toxicology. Other activities carried out by IPCS include the devel- opment of know-how for coping with chemical accidents, coordination of laboratory testing and epidemiological studies, and promotion of research on the mechanisms of the biological action of chemicals. ISBN 92 4 154096 6 ©World Health Organization 1984 Publications of the World Health Organization enjoy copyright protec- tion in accordance with the provisions of Protocol 2 of the Universal Copy- right Convention. For rights of reproduction or translation of WHO publica- tions, in part or in toto, application should be made to the Office of Publica- tions, World Health Organization, Geneva, Switzerland. The World Health Organization welcomes such applications. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or con- cerning the delimitation of its frontiers or boundaries. The mention of specific companies or of certain manufacturers' products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not men- tioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters. PRINTED IN FINLAND 84/6150 - VAMMALA - 6000 -3- CONTENTS ENVIRONMENTAL HEALTH CRITERIA FOR FLUORINE AND FLUORIDES Rage PREFACE ......................... 1. SUJINARY AND RECOMMENDATIONS FOR FURTHER RESEARCH 1.1 Summary .................... 1 1 1.1.1 Analytica1 methods ........... 11 1.1.2 Sources and magnitude of exposure . 11 1.1.3 Chemobiokinetics and metabolism ..... 12 1.1.4 Effect of fluoride on plants and animals ............... 12 1.1.5 Beneficial effects on human beings . 13 1.1.6 Toxic effects on human beings ...... 13 1.2 Recommendations for further research ...... 14 2. PROPERTIES AND ANALYTICAL METHODS .......... 15 2.1 Chemical and physical properties of fluorine and its compounds ............... 15 2.1.1 Fluorine ................ 15 2.1.2 Hydrogen fluoride ............ 16 2.1.3 Sodium fluoride and other alkali fluorides ................ 16 2.1.4 Fluorspar, cryolite, and fluorapatite . 17 2.1.5 Silicon tetrafluoride, fluorosilicic acid, and fluorosilicates ........ 17 2.1.6 Sodium monoflurophosphate ........ 18 2.1.7 Organic fluorides ............ 18 2.2 Determination of fluorine ........... 19 2.2.1 Sampling and sample preparation ..... 19 2.2.1.1 Air ............... 20 2.2.1.2 Soil and rocks .......... 20 2.2.1.3 Water .............. 21 2.2.1.4 Animal tissues .......... 21 2.2.1.5 Plants .............. 22 2.2.2 Separation and determination o.f fluoride 22 2.2.2.1 Colorimetric methods ....... 23 2.2.2.2 The fluoride selective electrode 23 2.2.2.3 Other methods .......... 24 3. FLUORIDE IN THE HUMAN ENVIRONMENT .......... 25 3.1 Fluoride in rocks and soil ........... 25 3.2 Fluoride in water ............... 25 -4-, Page 3.3 Airborne fluoride ...............26 3.4 Fluoride in food and beverages .........27 3.5 Total human intake of fluoride .........31 4. CHEMOBIOKINETICS AND METABOLISM ...........37 4.1 Absorption ................... 37 4.2 Retention and distribution ........... 37 4.2.1 The fluoride balance .......... 37 4.2.2 Blood .................. 38 4.2.3 Bone .................. 40 4.2.4 Teeth .................. 41 4.2.5 Soft tissues .............. 42 4.3 Excretion ................... 42 4.3.1 Urine .................. 42 4.3.2 Faeces ................. 43 4.3.3 Sweat .................. 44 4.3.4 Saliva ................. 44 4.3.5 Milk .................. 44 4.3.6 Transpiacental transfer ......... 44 4.4 Indicator media ................ 44 5. EFFECTS ON PLANTS AND ANIMALS ............ 46 5.1 Plants ..................... 46 5.2 Insects .................... 48 5.3 Aquatic animals ................ 48 5.4 Birds ..................... 49 5.4.1 Acute effects .............. 49 5.4.2 Chronic effects ............. 52 5.5 Mammals .................... 52 5.5.1 Acute effects .............. 52 5.5.1.1 Exposure to sodium fluoride . 52 5.5.1.2 Exposure to fluorine, hydrogen fluoride, or silicon tetrafluoride 54 5.5.2 Chronic effects on small laboratory animals ................. 55 5.5.3 Chronic effects on livestock ...... 56 5.6 Genotoxicity and carcinogenicity ........ 59 5.6.1 Genetic effects and other related end points in short-term tests ....... 59 5.6.2 Carcinogenicity in experimental animals ................. 60 5.7 Experimental caries .............. 60 5.8 Possible essential functions of fluorides . 60 -5-. Page 6. BENEFICIAL EFFECTS ON HUMAN BEINGS .........62 6.1 Effects of fluoride in drinking-water .....62 6.2 Cariostatic mechanisms .............66 6.3 Fluoride in caries prevention .........66 6.3.1 Fluoridated salt (NaCl) .........67 6.3.2 Fluoridated milk ............67 6.3.3 Fluoride tablets ............68 6.3.4 Topical application of fluorides . 68 6.4 Treatment of osteoporosis ...........69 7. TOXIC EFFECTS ON HUMAN BEINGS ............ 72 7.1 Acute toxic effects of fluoride salts ..... 72 7.2 Caustic effects of fluorine and hydrogen fluoride .................... 74 7.3 Chronic toxicity ................ 75 7.3.1 Occupational skeletal fluorosis ..... 75 7.3.2 Endemic skeletal fluorosis ....... 77 7.3.3 Dental fluorosis ............ 79 7.3.4 Effects on kidneys ........... 83 7.4 Carcinogenicity ................ 85 7.5 Teratogenicity ................. 85 7.6 Effecta on mortality patterns ......... 86 7.7 Allergy, hypersensitivity, and dermatological reactions ................... 87 7.8 Biochemical effects .............. 89 8. EVALUATION OF SIGNIFICANCE OF FLUORIDES IN THE ENVIRONMENT ................... 92 8.1 Relative contribution from air, food, and water to total human intake .......... 92 8.2 Doses necessary for beneficial effects in man 92 8.3 Toxic effects in man in relation to exposure . 93 8.3.1 Dental fluorosis ............ 93 8.3.2 Skeletal fluorosis ........... 93 8.3.3 Other effects .............. 94 8.4 Effects on plants and animals ......... 94 8.4.1 Plants ................. 94 8.4.2 Animals ................. 94 REFERENCES.......................96 -6- NOTE TO READERS OF THE CRITERIA DOCUMENTS While every effort has been made to present information in the criteria documents as accurately as possible without unduly delaying their publication, mistakes might have occurred and are likely to occur in the future. In the interest of all users of the environmental health criteria documents, readers are kindly requested to communicate any errors found to the Manager of the International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland, in order that they may be included in corrigenda, which will appear in subsequent volumes. In addition, experts in any particular field dealt with in the criteria documents are kindly requested to make available to the WHO Secretariat any important published information that may have inadvertently been omitted and which may change the evaluation of health risks from exposure to the environmental agent under examination, so that the information may be considered in the event of updating and re-evaluation of the conclusions contained in the criteria documents. -7- IPCS TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR FLUORINE AND FLUORIDES Members Dr F. Berglund, Department of Medical Research, KabiVitrum Pharmaceuticals, Stockholm, Sweden Dr A.W. Davison, Department of Plant Biology, The University, Newcastle-Upon-Tyne, United Kingdom (Rapporteur) Professor C.O. Enwonwu, National Institute for Medical Research, Yaba, Lagos, Nigeria Professor W. Kiinzel, Stomatology Section, Erfurt Academy of Medicine, Democratic Republic of Germany Mr F. Murray, Department of Biological Sciences, University of Newcastle, New South Wales, Australia Professor M.D. Noweir, Occupational Health Department, High Institute of Public Health, Alexandria, Egypt (Chairman) Dr P. Phantunivanit, Faculty of Dentistry, Chulalongkorti University, Bangkok, Thailand Dr R.G. Scharnschula, WHO Collaborative Unit for Caries and Periodontal Disease Research, Institute of Dental Research, Sydney, Australia Professor Dr Ch. Schlatter, Swiss Federal Institute of Technology and University of Zurich, Institute of Toxicology, Schwerzenbach, Switzerland Dr D.R. Taves, Department of Radiation Biology and Biophysics,
Load more

Recommended publications
  • Combining Super-Resolution Microscopy with Neuronal Network Recording Using Magnesium Fuoride Thin Flms As Cover Layer for Multi-Electrode Array Technology L
    www.nature.com/scientificreports OPEN Combining super-resolution microscopy with neuronal network recording using magnesium fuoride thin flms as cover layer for multi-electrode array technology L. Schmidl1,6, G. Schmidl2,6*, A. Gawlik2, J. Dellith2, U. Hübner2, V. Tympel3, F. Schmidl4, J. Plentz2, C. Geis1 & H. Haselmann1,5 We present an approach for fabrication of reproducible, chemically and mechanically robust functionalized layers based on MgF2 thin flms on thin glass substrates. These show great advantages for use in super-resolution microscopy as well as for multi-electrode-array fabrication and are especially suited for combination of these techniques. The transparency of the coated substrates with the low refractive index material is adjustable by the layer thickness and can be increased above 92%. Due to the hydrophobic and lipophilic properties of the thin crystalline MgF2 layers, the temporal stable adhesion needed for fxation of thin tissue, e.g. cryogenic brain slices is given. This has been tested using localization-based super-resolution microscopy with currently highest spatial resolution in light microscopy. We demonstrated that direct stochastic optical reconstruction microscopy revealed in reliable imaging of structures of central synapses by use of double immunostaining of post- (homer1 and GluA2) and presynaptic (bassoon) marker structure in a 10 µm brain slice without additional fxing of the slices. Due to the proven additional electrical insulating efect of MgF2 layers, surfaces of multi- electrode-arrays were coated with this material and tested by voltage-current-measurements. MgF2 coated multi-electrode-arrays can be used as a functionalized microscope cover slip for combination with live-cell super-resolution microscopy.
    [Show full text]
  • The Heat of Combustion of Beryllium in Fluorine*
    JOURNAL OF RESEARCH of the National Bureau of Standards -A. Physics and Chemistry Vol. 73A, No.3, May- June 1969 The Heat of Combustion of Beryllium in Fluorine* K. L. Churney and G. T. Armstrong Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234 (February 11, 1969) An expe rimental dete rmination of the e ne rgies of combustion in Auorine of polyte traAuoroethylene film and Q.o wder and of mixtures of beryllium with polytetraAuoroethyle ne gi ves for reacti on ( 1)f).H ~.or= - 1022.22 kJ 111 0 1- 1 (- 244.32 kcal mol - I) wit h a n ove ra ll precision of 0.96 kJ 111 0 1- 1 (0. 23 kcal 111 0 1- 1 ) at the 95 pe rce nt confid ence limit s. The tota l un cert a int y is estimated not to exceed ±3.2 kJ mol- I (±0.8 kcal mol - I). The measureme nts on polytetraflu oroeth yle ne giv e for reaction (2a) and reacti on (2 b) f).H ~. o c =- 10 369. 7 and - 10392.4 Jg- I, respective ly. Overall precisions e xpressed at the 95 pe rcent confide nce Ijmits are 3.3 and 6.0 Jg- I, respective ly. Be(c)+ F,(g) = BeF2(a morphous) (1) C,F.(polym e r powd er) + 2F2(g) = 2CF.(g) (2a) C2F.(polyme r film ) + 2F2 (g) = 2CF.(g) (2b) Be2C and Be metal were observed in a small carbonaceous residue from the co mbustion of the beryll iul11 -polytetraAuoroethylene mixtures.
    [Show full text]
  • UNITED STATES PATENT Office SVEND S
    Patented May 24, 1932 1,859,998 UNITED STATES PATENT oFFICE SVEND S. SVENDSEN, OF CHICAGO, ILLINOIS, ASSIGNOR TO CLAY REDUCTION comi PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIs . HYDRATED SILICA No Drawing. Application filed December 23, 1927. Serial No. 242,291. This invention relates to the production of silicofluoride is also volatilized and collected hydrated silica from a silicious material such in aqueous animonia. The volatilization oc as silica and silicates generally. - - - - curs about 300 C. The following reactions According to the invention the silicious take place in the aqueous ammonia at tem 5 material is treated with ammonium fluoride peratures below 34 C.: 5 5 or bifluoride and silicon ammonia fluorine compounds are produced. These compounds 2SiF(NH) +2H.O= are volatilized and converted into hydrated (NH4)2SiFs--SiO, (hydrated) + silica by the action of water and ammonia. 2NH.F. (IV) O Metallic silicates or substances containing (NH)SiF+4NH,+2HO = them can be subjected to this treatment di SiO, (hydrated) + 6NH.F. (V) rectly. In treating silica in the form of quartz it is found to be necessary to subject It is thus apparent that O heating the it to a preliminary treatment in order to fa silicious material with the ammonium-flu cilitate the action of the ammonium fluoride oride, ammonia-silicon-fluorine compounds a or bifluoride thereon. A suitable preliminary are formed, and by employing suitable tem treatment is to heat the quartz to a bright red peratures are volatilized from the reaction heat and suddenly cool it by immersion in mixture. These compounds may be silicon water.
    [Show full text]
  • Magnesium Fluoride (Mgf2)
    Magnesium Fluoride (MgF2) THOMAS M. COTTER, MICHAEL E. THOMAS, and WILLIAM J. TROPF Applied Physics Laboratory The Johns Hopkins University Laurel, Maryland Magnesium fluoride is a tetragonal material with TiO2 (rutile) structure. The space group is D 4h14 or P42/mnm. The unit cell contains two formula units (six atoms). Dimensions of the cell (at 27 ~ are 0.4623 nm along the a axis and 0.3052 nm along the c axis [1, also see 2]. Theoretical density is 3.177 g/cm 3 and melting point is 1528 _+ 3 K [2]. A melting point of 1543 K is also reported [3]. Magnesium ions occupy octahedral sites with Dzh point symmetry. Six fluorine ions at sites with Czv symmetry surround each magnesium ion. Fluorine-ion positions in the unit cell are known from X-ray diffraction measurements [1, 2]. A wide transparency range from 0.12 to 8 ~tm [2], good mechanical properties, and low optical index of refraction make magnesium fluoride a desirable material for coatings and interference filters. MgF2 is a positive uniaxial material, with its highest birefringence in the UV. Except for lithium fluoride, MgF2 has the shortest wavelength cutoff of any common optical material. Magnesium fluoride occurs naturally as the mineral selliate [3]. Single-crystal MgF2 [3, 4] is widely used for windows, lenses, polarizers, and other optical components. Optical-quality, hot-pressed polycrystalline MgF2 is also used for optical components, particularly in the infrared. IRTRAN 1 [5] is a trade name for hot-pressed MgF2 made by Kodak; KO-1 is an equivalent Soviet material [6].
    [Show full text]
  • United States Patent Office Patented Jan
    2,732,410 United States Patent Office Patented Jan. 24, 1956 2 The process can be carried out in various ways. Thus, 2,732,410 the vaporized halogen fluoride can be passed, if desired PROCESS FOR PREPARNG TETRAFLUORO with an inert carrier gas such as nitrogen, argon or helium, ETHYLENE BY REACTING CARBON AND through a column of carbon heated at a temperature of A BINARY HALOGEN FLUORDE at least 1500 C. in a suitable reactor, e. g., a graphite Mark W. Farlow, Holly Oak, and Earl L. Muetterties, tube placed inside a resistance furnace or an induction Hockessin, Dei, assignors to E. I. du Post de Neois's furnace. The gaseous reaction products are then imme and Company, Wilmington, Del, a corporation of Dela diately treated, as described below, to remove any un Ware reacted halogen fluoride and any free chlorine or bromine, 0 in order to minimize or eliminate the possibility of their No Drawing. Application January 12, 1955, reacting with the tetrafluoroethylene present in the re Serial No. 481,482 action product. A preferred mode of operation consists in 4 Claims. (C. 260-653) reacting the halogen fluoride with the carbon electrodes of a carbon arc, where the temperature is estimated to be in This invention relates to a new process of preparing 15 the range of 2500 to 3500-4000 C., and again immediate compounds containing only carbon and fluorine, or car ly removing from the effluent gas any halogen fluoride and bon, fluorine and another halogen, such compounds be free reactive halogen which may be present.
    [Show full text]
  • A Review of Water Fluoridation” October 1, 2010 November 7, 2014
    Alberta Health, Office of the Chief Medical Officer of Health Notice to the reader on “A Review of Water Fluoridation” October 1, 2010 November 7, 2014 November 7, 2014 Notice to the reader Re: A Review of Water Fluoridation, October 1, 2010 report This report is a compilation of existing resources, materials and research that highlight key aspects of the water fluoridation debate. It was developed as a support to assist Medical Officers of Health in Alberta in dealing with queries on fluoridation. While not written for the public, this report is now widely available to help anyone interested to better understand the issue and to provide answers to questions about fluoridation. The reader must be aware that this report is not drafted as a scientific review article for publication although references are made to previous systematic reviews and their findings. It is also important to note that specific references for quoted material are given in the text at the time they are used. Office of the Chief Medical Officer of Health, Alberta Health © 2014 Government of Alberta PREPARED BY DR. STEVEN K. PATTERSON A Review of Water Fluoridation S UBMITTED: O CTOBER 1, 2010 A Review of Water Fluoridation Dr. Steven Patterson A Table of Contents Page Number Executive summary 3 Introduction/Background 6 Importance of oral health Scope of dental disease in Alberta/Canada 7 Dental disease in Alberta Dental disease in Canada Mechanism of fluoride’s action 12 Benefits of water fluoridation Dental fluorosis 17 Safety of water fluoridation Canadian Health Measure Survey 2007-2009 Fluorosis data from Alberta dental surveys Population vs.
    [Show full text]
  • Elemental Fluorine Product Information (Pdf)
    Elemental Fluorine Contents 1 Introduction ............................................................................................................... 4 2.1 Technical Application of Fluorine ............................................................................. 5 2.2 Electronic Application of Fluorine ........................................................................... 7 2.3 Fluorine On-Site Plant ............................................................................................ 8 3 Specifications ............................................................................................................ 9 4 Safety ...................................................................................................................... 10 4.1 Maintenance of the F2 system .............................................................................. 12 4.2 First Aid ................................................................................................................ 13 5.1 Chemical Properties ............................................................................................. 14 5.2 Physical Data ....................................................................................................... 15 6 Toxicity .................................................................................................................... 18 7 Shipping and Transport ........................................................................................... 20 8 Environment ...........................................................................................................
    [Show full text]
  • Sulfur Hexafluoride Hazard Summary Identification
    Common Name: SULFUR HEXAFLUORIDE CAS Number: 2551-62-4 RTK Substance number: 1760 DOT Number: UN 1080 Date: April 2002 ------------------------------------------------------------------------- ------------------------------------------------------------------------- HAZARD SUMMARY * Sulfur Hexafluoride can affect you when breathed in. * If you think you are experiencing any work-related health * Sulfur Hexafluoride can irritate the skin causing a rash or problems, see a doctor trained to recognize occupational burning feeling on contact. Direct skin contact can cause diseases. Take this Fact Sheet with you. frostbite. * Exposure to hazardous substances should be routinely * Sulfur Hexafluoride may cause severe eye burns leading evaluated. This may include collecting personal and area to permanent damage. air samples. You can obtain copies of sampling results * Breathing Sulfur Hexafluoride can irritate the nose and from your employer. You have a legal right to this throat. information under OSHA 1910.1020. * Breathing Sulfur Hexafluoride may irritate the lungs causing coughing and/or shortness of breath. Higher WORKPLACE EXPOSURE LIMITS exposures can cause a build-up of fluid in the lungs OSHA: The legal airborne permissible exposure limit (pulmonary edema), a medical emergency, with severe (PEL) is 1,000 ppm averaged over an 8-hour shortness of breath. workshift. * High exposure can cause headache, confusion, dizziness, suffocation, fainting, seizures and coma. NIOSH: The recommended airborne exposure limit is * Sulfur Hexafluoride may damage the liver and kidneys. 1,000 ppm averaged over a 10-hour workshift. * Repeated high exposure can cause deposits of Fluorides in the bones and teeth, a condition called “Fluorosis.” This ACGIH: The recommended airborne exposure limit is may cause pain, disability and mottling of the teeth.
    [Show full text]
  • D3G DISPATCH News About Developmental Dental Defects (D3s), the D3 Group, and the Chalky Teeth Campaign
    THE D3 GROUP ISSUE #13 MARCH 2020 D3G DISPATCH News about Developmental Dental Defects (D3s), The D3 Group, and the Chalky Teeth Campaign. COMMENT FROM THE CUSP: Going viral Commiserations to everyone disrupted by the pandemic crisis, and hallelujah to science and technology for providing humanity an unprecedentedly strong path to recovery. Just 3 weeks ago, a colleague praised D3G's recent progress as "going viral"– not knowing the next day we'd be in the midst of a COVID-19 scare that has consumed life down under since. With D3G now affected by the bad connotation of improvement") emerge, usually directed at authors "going viral", this first issue of 2020 relays a mixture of and/or reviewing. It seems appropriate that D3G use ups, downs and uncertainties – unfortunately the April CE it's clinico-scientific strengths to improve both ends event in Toronto has been postponed and the October of the system and that this will be a great topic for Symposium remains on track but uncertainly so. On the our upcoming symposium. bright side we share some wonderful examples of "D3 Take care, and do the world a favour by communicating love", provide further reasons to "think beyond MIH" the importance of science! and to communicate translationally, and dip a cautious toe into the murky waters of research publication quality. Unsurprisingly the latter is frequently discussed amongst D3-Mike | Mike Hubbard D3ers and diverse grumbles (aka "opportunities for D3G Founder-Director NEWS: Feel the D3 love :-) Given growing tensions with COVID-19, we're thrilled the first 3 months of 2020 delivered a wonderful triad of "feel the D3 love" moments that'll surely help us through this challenge and beyond.
    [Show full text]
  • Ionic Compound Ratios Time: 1 -2 Class Periods
    Collisions Lesson Plan Ionic Compound Ratios Time: 1 -2 class periods Lesson Description In this lesson, students will use Collisions to explore the formation of ionic compounds and compound ratios. Key Essential Questions 1. What makes up an ionic compound? 2. Are ionic compounds found in common ratios? Learning Outcomes Students will be able to determine the ionic compound ratio of an ionic compound. Prior Student Knowledge Expected Cations are postiviely charged ions and anions are negatively charged ions. Lesson Materials • Individual student access to Collisions on tablet, Chromebook, or computer. • Projector / display of teacher screen • Accompanying student resources (attached) Standards Alignment NGSS Alignment Science & Enginnering Practices Disciplinary Core Ideas Crosscutting Concepts • Developing and using • HS-PS-12. Construct and • Structure and Function models revise an explanation for the • Construcing explanations outcome of a simple chemical and designing solutions rection based on the outermost electron states of atoms, trends int he periodic table, and knowl- edge of the partterns of chemi- cal properties. www.playmadagames.com ©2018 PlayMada Games LLC. All rights reserved. 1 PART 1: Explore (15 minutes) Summary This is an inquiry-driven activity where students will complete the first few levels of the Collisions Ionic Bonding game to become introduced to the concept of ionic bonding and compound ratios. Activity 1. Direct students to log into Collisions with their individual username and password. 2. Students should enter the Ionic Bonding game and play Levels 1-6 levels. 3. Have your students answer the following questions during gameplay: 1. What combination of ions did you use to successfully match a target? 2.
    [Show full text]
  • Soares, R. Et Al
    Original Article DOI: 10.7860/JCDR/2017/23594.9758 Assessment of Enamel Remineralisation After Treatment with Four Different Dentistry Section Remineralising Agents: A Scanning Electron Microscopy (SEM) Study RENITA SOARES1, IDA DE NORONHA DE ATAIDE2, MARINA FERNANDES3, RAJAN LAMBOR4 ABSTRACT these groups were remineralised using the four remineralising Introduction: Decades of research has helped to increase our agents. The treated groups were subjected to pH cycling over a knowledge of dental caries and reduce its prevalence. However, period of 30 days. This was followed by assessment of surface according to World Oral Health report, dental caries still remains microhardness and SEM for qualitative evaluation of surface a major dental disease. Fluoride therapy has been utilised in changes. The results were analysed by One-Way Analysis Of a big way to halt caries progression, but has been met with Variance (ANOVA). Multiple comparisons between groups were limitations. This has paved the way for the development of performed by paired t-test and post-hoc Tukey test. newer preventive agents that can function as an adjunct to Results: The results of the study revealed that remineralisation of fluoride or independent of it. enamel was the highest in samples of Group E (Self assembling Aim: The purpose of the present study was to evaluate the ability peptide P11-4) followed by Group B (CPP-ACPF), Group C (BAG) of Casein Phosphopeptide-Amorphous Calcium Phosphate and Group D (fluoride enhanced HA gel). There was a significant Fluoride (CPP ACPF), Bioactive Glass (BAG), fluoride enhanced difference (p<0.05) in the remineralising ability between the self assembling peptide P -4 group and BAG and fluoride Hydroxyapatite (HA) gel and self-assembling peptide P11-4 to 11 remineralise artificial carious lesions in enamel in vitro using enhanced HA gel group.
    [Show full text]
  • Periodic Trends in the Main Group Elements
    Chemistry of The Main Group Elements 1. Hydrogen Hydrogen is the most abundant element in the universe, but it accounts for less than 1% (by mass) in the Earth’s crust. It is the third most abundant element in the living system. There are three naturally occurring isotopes of hydrogen: hydrogen (1H) - the most abundant isotope, deuterium (2H), and tritium 3 ( H) which is radioactive. Most of hydrogen occurs as H2O, hydrocarbon, and biological compounds. Hydrogen is a colorless gas with m.p. = -259oC (14 K) and b.p. = -253oC (20 K). Hydrogen is placed in Group 1A (1), together with alkali metals, because of its single electron in the valence shell and its common oxidation state of +1. However, it is physically and chemically different from any of the alkali metals. Hydrogen reacts with reactive metals (such as those of Group 1A and 2A) to for metal hydrides, where hydrogen is the anion with a “-1” charge. Because of this hydrogen may also be placed in Group 7A (17) together with the halogens. Like other nonmetals, hydrogen has a relatively high ionization energy (I.E. = 1311 kJ/mol), and its electronegativity is 2.1 (twice as high as those of alkali metals). Reactions of Hydrogen with Reactive Metals to form Salt like Hydrides Hydrogen reacts with reactive metals to form ionic (salt like) hydrides: 2Li(s) + H2(g) 2LiH(s); Ca(s) + H2(g) CaH2(s); The hydrides are very reactive and act as a strong base. It reacts violently with water to produce hydrogen gas: NaH(s) + H2O(l) NaOH(aq) + H2(g); It is also a strong reducing agent and is used to reduce TiCl4 to titanium metal: TiCl4(l) + 4LiH(s) Ti(s) + 4LiCl(s) + 2H2(g) Reactions of Hydrogen with Nonmetals Hydrogen reacts with nonmetals to form covalent compounds such as HF, HCl, HBr, HI, H2O, H2S, NH3, CH4, and other organic and biological compounds.
    [Show full text]