Fluoride and the Tooth Surface - PDF

Fluoride and the Tooth Surface Oral and Dental Science Josh Hudson GDC Learning Outcomes: 1.1.8 Describe the properties of relevant medicines and therapeutic agents and discuss their application to patient management 1.10.2 Provide patients with comprehensive and accurate preventative edu...

Fluoride and the Tooth Surface Oral and Dental Science Josh Hudson GDC Learning Outcomes: 1.1.8 Describe the properties of relevant medicines and therapeutic agents and discuss their application to patient management 1.10.2 Provide patients with comprehensive and accurate preventative education and instruction in a manner which encourages self care and motivation 1.10.3 Underpin all patient care with a preventative approach that contributes to the patient's long-term oral health and general health 1.10.4 Advise on and apply a range of preventative materials and treatment as appropriate 2.3 Describe and evaluate the role of health promotion in terms of the changing environment, community and individual behaviours to deliver health gain 2.4 Explain evidence-based prevention and apply appropriately  Pre-reading Caries ‘Aetiology of Dental Caries’ Lecture Susceptible tooth surface Plaque Bacteria Time Fermentable Carbohydrate Pre-reading ‘Histology of enamel and dentine’ Lectures Intended learning outcomes By the end of this session you will be able to.. List the key milestones in the history of fluoride and its use in caries prevention Outline and describe the stages in fluoride deposition Describe the modes of action of fluoride Explain how fluorosis occurs Identify fluorosis and assess its severity Refresher session… Normal enamel is mainly made up of hydroxyapatite This makes up 96% of enamel This is made of a lattice structure It is primarily made of phosphate and calcium ions Ca10 (PO4)6 (OH)2 Refresher session.. Decreasing pH As pH lowers below the critical pH (5.5 for hydroxyapatite), the tooth surface will demineralise Ca 10 (PO4)6 (OH)2 and break down into its component ions. If the pH regularly remains low Demineralisation and does not neutralise, extensive demineralisation over time will lead to caries. Ca 2+ , PO4 3- + OH- (hydroxyl ion) Refresher session.. Infrequent attacks mean less time below critical PH and less demineralisation (lower caries Stephen Curves risk) Frequent attacks mean more time below the critical PH and hence more demineralization (higher caries risk) How is fluoride relevant to you as dental professionals? Fluorine Before we can effectively link fluoride to dentistry, we need to understand what it actually is and its history.. Fluorine  Has the symbol F and atomic number 9 Highly reactive Is a Halogen within with metals to the periodic table Fluorine form salts or halides (referred to as fluoride) Found naturally in water, rocks, soil and tea  1892 1901 Frederick McKay 1902 1874 Sir James Crichton-Browne Sale of fluorine compound Dr Erhardt 1909 Investigation of Colorado Stain 1931 1930 Staining on teeth in Bauxite, Arkansas 1912 Dr HT Dean ‘shoe leather’/ ‘21 McKay investigates similar cities’ studies 1916 staining in Naples, Italy GV Black paper published on Colorado Stain 1945 1932 First experiment of artificial water McKay link between mottling fluoridation 1933 and caries reduction Ainsworth UK water fluoride 1940 comparison studies 1955 Artificial water fluoridation tried out in the UK 1960 1964 Anti-fluoride Birmingham fluoridated campaigns 1976 2000 The Royal College of Physicians‘ The York Study enquiry into water fluoridation 1980 Mrs McColl’s opposition 1985 of water fluoridation KNOX report The Future… Fluoride History 1. Colorado stain identification 2. HV Churchill water testing 07 01 7. Cochrane review 02 06 3. Identification fluoride may reduce caries 03 6. York report 05 04 4. Shoe leather surveys/21 cities surveys 5. Knox report 1) Colorado Stain - 1916 Dr Frederik McKay documented a ‘stain’ on some teeth when working in Colorado springs He was the first to document this appearance and went on to investigate its cause Enlisted the help of GV Black to investigate GV Black published a paper on the Colorado Stain 2) Water Sampling - 1931 Following identification of this stain by McKay, Churchill, who was a chemist for a local mining company in Arkansas, realised local children developed a similar effect following their water source changing Concerned this may be linked to his companies aluminium mine, he investigated the water He identified higher fluoride content in water where mottling was present Advised although there is higher fluoride in these areas, no definitive link to the mottling 3) Identification Fluoride may reduce caries - 1932 Although this had been postulated previously, in 1932 McKay suggested that the same compound that caused the mottling may reduce caries McKay had identified although mottled, these teeth developed no greater chance of decay that teeth which are normally calcified 4) Shoe leather studies/21 cities studies – 1930-1940 Following McKay’s claims, the head of the US public health service assigned Dr H Trendley- Dean to research the links between fluoride in water, mottling and caries reduction. His subsequent studies demonstrated; Increased mottling with increased fluoride Decreased caries if water fluoridated 1ppm fluoride appeared to be the optimal level He developed an ‘Index for Fluorosis’ to classify the severity of this tooth mottling  Benefits discovered Water Fluoridated Caries reduction Campaigns against ‘mass medication’ 5) Knox Report - 1985 Review of papers looking at the links between fluoride and cancer Concluded that there is no link and fluoridated drinking water is safe 6) York Report - 2000 Reviewed evidence from hundreds of studies into water fluoridation No association found between water fluoridation and bone fractures, or water fluoridation and cancer  Based on older research (no Fluoridation increased the modern research percentage of children with no available) decay in deciduous teeth by 15% Insufficient evidence on effect in adults 73% of studies focussed on areas with natural fluoridation Cochrane Review 2015 Fluoridated water reduces caries in children's permanent Fluoridation increased teeth by 26% the percentage of children with no decay in Fluoridation of 0.7ppm gives permanent teeth by 14% a 12% chance of Fluorosis Fluoridated water reduces (mottling) that may cause caries in deciduous (baby) aesthetic concerns teeth by 35% Modern Day Controversy still remains for artificial water fluoridation Currently in the UK approximately 10% of the population has fluoride in the water Have you lived in an area with fluoride in the water? Click this link to find out Modern Day Luckily, although water fluoridation is not universal, the benefits of fluoride use are well researched and well advocated in caries prevention Cochrane Studies Delivering Better Oral Health NHS Website NHS Review of Water Fluoridation Patients will still question its use! So how does fluoride prevent caries? How does it work? - Uptake into the tooth Pre-eruptive Post-eruptive Ultimately, fluoride is stage (systemic stage (topical absorbed into the tooth fluoride) fluoride) surface making it more resistant to demineralisation from the Matrix caries process. This occurs Secretion at multiple stages; Maturation Stage How is it absorbed? – Matrix Secretion Stage Fluoride absorbed from systemic sources (swallowed fluoride) Travels to developing tooth buds via blood and surrounding tissue fluid Deposited into the tooth during enamel formation as fluoroapetite This fluoroapetite replaces the usual hydroxyapetite Excess fluoride can inhibit ameloblast activity affecting enamel development This may result in ‘mottling’ termed fluorosis  How is it absorbed? - Maturation Stage Fluoride absorbed from systemic 1 sources (swallowed fluoride) Occurs after calcification but 2 prior to eruption Deposition of fluoride continues at the 3 enamel surface from the tissue fluid around the tooth 4 More fluoride is taken up by outer layer 5 Also forms fluoroapetite How is it absorbed? - Post-Eruptive Stage Drop in PH due Loss of calcium and Healthy tooth to bacterial acid Demineralised phosphate from surface tooth surface hydroxyapatite Addition of Increase in calcium and Remineralisation PH phosphate from saliva to reform hydroxyapatite How is it absorbed? - Post-Eruptive Stage Drop in PH due Loss of calcium and Healthy tooth to bacterial acid Demineralised phosphate from surface tooth surface hydroxyapatite Addition of calcium Increase in and phosphate and Remineralisation PH fluoride from saliva to form fluoroapetite How is it absorbed? - Post-Eruptive Stage Key Points The most fluoride is acquired during the 2-3 years post-eruption This is because it is more porous which facilitates diffusion and uptake Demineralised enamel also absorbs fluoride more easily for this reason Fluoride reacts strongly with calcium so does not penetrate deeply if used topically Maximum uptake cannot be exceeded but fluoride can be replaced as the surface is abraded It is therefore more essential for fluoride to be used to reduce the progression of caries rather than purely prevent it. This is because it is more easily absorbed once the process has started. So it works by producing fluoroapetite but why is this important? Why is fluoroapetite important? Formed by fluoride ions replacing hydroxyl ions during remineralisation This newly formed molecule is more stable due to improved hydrogen bonds, fewer imperfections and larger crystals Helps inhibit demineralisation Fluoroapetite’s critical and promote remineralisation PH = 4.5 Why is fluoroapetite important? Due to the lower critical PH, fluoroapetite is less soluble. This makes the tooth more resistant to future acid attacks This, therefore, reduces demineralisation This ultimately reduces caries incidence Where does the fluoride come from? Topical applications of fluoride create a reservoir of fluoride in saliva This fluoride bonds to calcium in saliva forming CaF2 When an acid attack occurs and PH drops, the fluoride is released This can then enter the tooth during remineralisation It is therefore essential that there is a regular supply of low-level fluoride to replace the ions lost. This forms the basis of caries prevention with fluoride. Ways to ensure this regular supply is maintained are summarised here Topical Fluoride Source Fluoride Level Prescription? Toothpaste (Stannous/Sodium 1450-5000ppm YES if 2800 or 5000ppm Fluoride) Mouth rinse 225ppm EITHER Restorative materials (e.g. Glass 0.8-1.2ppm dropping over - Ionomer Cements) time Fluoride Varnish 22,600ppm YES Water Fluoridation 0.7-1ppm generally NO Fluoride Tablets Made up to 0.3-0.7ppm YES How does that work in real life?  Ca Ca Ca PH Ca DROP F Ca = Hydroxyapatite Ca = Fluoroapatite Ca  pH RISE F = Hydroxyapatite = Fluoroapatite Does fluoride have any other mechanisms of action?  H H H H H H H H Action on bacterial plaque At concentrations over 1% (such as professionally applied fluoride), a bactericidal effect is demonstrated This means fluoride can be toxic to bacteria such as strep mutans When the PH drops, H+ and F- bond to form HF which then diffuses across the bacterial cell wall This then inhibits glycolysis by preventing the uptake of glucose through the cell wall and its breakdown. It also inhibits enzyme systems involved in the conversion and transport of sugars This cuts of the bacteria’s food supply meaning it cannot metabolise sugars into acid F Action on enamel surface Fluoride reduces the surface It has also been energy of enamel. This has the 0 suggested that fluoride effect of decreasing the 03 on the tooth surface can wettability of enamel and 1 ‘push away’ proteins hence ability for bacteria to which reduces pellicle adhere formation Less pellicle This prevents the formation, less formation of pellicle plaque and less so plaque cannot 02 04 bacterial adhesion accumulate as easily leads to a reduced likelihood of caries Action on tooth morphology Some evidence suggests that systemic fluoride 0 may alter tooth 1 morphology during their development These may 03 therefore make the tooth more cleansable This can result in; Shallower pits Reduced fissure 02 depth Lower cusp height What about the other tooth surfaces? (Dentine and Cementum) Root Caries Recap As these are Gingival recession mineralised surfaces, exposes dentine and these are also cementum susceptible to decay This is root caries This is more common in; As they are less xerostomia patients mineralised, decay can (patients with limited progress saliva) and radiotherapy faster patients  How does fluoride prevent root caries? 1. Incorporating into surface during remineralisation 2. Reducing surface wettability 3. Antibacterial effects (Kato et al, 1997) What does the research say? Topical Fluoride to Prevent Root Caries: Systematic Review with Network Meta-a nalysis Professionally applied fluoride (Silver diamine fluoride, fluoride varnish) reduces risk of root caries at 2 years Self-applied fluoride (various concentrations of sodium fluoride mouth rinse, and fluoride tooth paste) reduces risk of root caries at 1 year Therefore, professionally and self-applied fluoride is essential for caries prevention in patients with exposed root surfaces (dentine and cementum) at risk of caries. Will become more of an issue as the population continues to age. Fluorosis What is fluorosis and how does it form? What is it? “The term given to changes in the enamel which are associated with excess ingestion of fluoride…it can vary from white opacities, lines or flecks to more severe brown-yellow mottling of the enamel. The precise effect depends on the dose of fluoride (from all sources), duration for which it was taken, and the age of the patient at the time of ingestion.” Clinical Textbook of Dental Hygiene and Therapy (Edited by Robert Ireland, 2006) Mechanism of fluorosis If excess fluoride is present it is thought to inhibit normal ameloblast activity during the matrix formation and maturation phases, and hypomineralised (and hypoplastic) enamel will form. Due to the hypomineralisation, the enamel becomes more porous and hence more readily takes up stain which can cause more obvious discolouration. It is important to remember that enamel defects can result from other causes, not just fluorosis. For example: trauma, disease, drugs and genetics. What are the aetiological agents? The ingestion of the below can cause fluorosis; 1. Dietary fluoride supplements 2. Drinking water 3. Toothpaste 4. Topical applications The most critical time is from 0-8 years as the teeth develop Due to the staggered nature of tooth development, not all teeth will always be affected depending on the timing of the fluoride exposure Is it fluorosis? Indices for recording fluorosis The two main indices are the Dean Index (1942) and the Thylstrup and Fejerskov index (1978) The Thylstrup and Fejerskov index is shown to the right Score 0 the enamel has normal translucency Scores 1-4 has increasing levels of fluorosis with no loss of the outermost enamel Scores 5-9 has increasing degrees of loss of the outermost enamel Summary Summary Action on hydroxyapatite Action on tooth Action on bacterial Mode of Action of Fluoride morphology enzymes Action on enamel surface Summary https://www.youtube.com/watch?v=TyVV0UDQ_f4 https://www.youtube.com/watch?v=TyVV0UDQ_f4 Thank You!