FLUORIDE USE IN DENTISTRY DR BAKARE Outline • • • • • • • • • • • Introduction History Natural Sources Of Fluoride Physiology and metabolism of fluoride Fluoride in Dentistry Control of dental caries Fluoride toxicity Dental fluorosis Fluorosis indices Water defluoridation Conclusion Introduction • Fluoride is a mineral and Fluoride ion comes from the element fluorine. • Fluorine is 17th most abundant element in the earths crust. • Highly reactive, hence never encountered in its free state in nature. • Exits only in combination with other elements as a fluoride compound • Constitutes about 0.032% in earth’s crust • The name Fluorine is derived from • The Latin word “fluore” meaning “to flow”. • Greek “floris”- destruction Brief History of Fluoride in Dentistry • Frederick McKay in 1901 noted characteristic mottling stains on teeth of children who had spent all their life in Colorado known as Colorado brown stain • G.V Black and others found that other regions in the USA has similar mottling, and histological exam show that enamel was imperfectly calcified. No difference in caries incidence compared with normal teeth. • Mackay suspected the cause to be from the water supply • Similar findings in a community formed by house workers of an aluminium company prompted the chief chemist anxious that aluminium should not be blamed, to analyse the water and found a higher than normal concentration of fluoride (about 13.7ppm) • HT Dean in 1938 showed a relationship between tooth mottling and water fluoride level and that mottling disappear or minimal as fluoride fall below 1ppm. • FA Arnold 1953 reported a 50% fall in caries in Grand Rapids compared with control group after 6years of artificially fluoridating water. • 1969 --- WHO recommended first time 1 ppm fluoride in drinking water for a practicable and effective public health measure. • 1994 ----- WHO has recommended optimum level of fluoride in drinking water as 0.5-1.0ppm. Fluoride in Nigeria • Data from Nigeria is sparse. Two studies from Plateau state found a prevalence of 26.1% in langtang with 20.6% classified as mild. It reported Fl conc of 2.39-3.96ppm in streams and 1.26-2.82ppm in wells(1997) • In 2008, a prevalence of 12.9% was recorded. This study also found higher prevalence in high altitude areas which had lower Fl content of 0.76+/- 0.04 than the lower altitude areas Natural Sources of Fluoride • In rock and soil- • Fluorspar ( fluorite CaF2) • Fluorapatite {Ca10F2 (PO4 )6} • Cryolite ( Na3AlF6) • In Soil, the fluoride concentration increases with depth. • In Water: • Sea water - 0.8- 1.4mg/L. • Lakes, rivers or artesian wells - below 0.5mg/L. • Concentrations as high as 95mg/L have been recorded in the United Republic of Tanzania. • In Air: • • • • • Fluoride is widely distributed in the atmosphere as; dusts of fluorides-containing soils gaseous industrial waste domestic burning of coal fires gases emitted in areas of volcanic activity • In Foods And Beverages: • • • • Unprocessed foods -low (0.1-2.5 mg/kg). In plants - 2-20mg/g of dry weight. Leafy vegetables -11-26 mg on dry weight basis. Fish -20-40 ppm on dry weight basis. • In Animals • • • • Beef, pork and mutton-0.3ppm Higher in Chicken- contained in bone and cartilage fragments Fish products- up to 20ppm Dried sea foods also fluoride rich 84.5ppm (South East Asia) • In beverages • Juice, beverages, • Infant formula • Fluoride content in liquid beverages generally reflects that of water used. Total daily intake of Fluoride • Fluoride from Air • Minimal • Fluoride from Water • Most important single source of fluoride • Dependent on fluoride concentration and amount • Fluctuation –climatic and geographical areas • Fluoride from food • 0.3 to 0.6 mg/day • Fluoride intake 6months of life-bottle/breast fed • Breast fed infant receives 0.003 to 0.004mg/day- formula fed infants (1.2ppm) fluoride intake increased 50 times Physiology of fluoride • Ingested fluoride is absorbed mainly from the upper G.I.T. • F ingested on an empty stomach reaches peak plasma level in 30 minutes • Up to 95% of ingested F may be absorbed • Absorbed fluoride is transported in plasma and is either excreted or deposited in the calcified tissues • Most absorbed fluoride is excreted in urine. • Single ingestion of 5mg fluoride by an adult is absorbed and cleared from the blood in 8-9 hrs. • Approx. 75% – 90% of ingested F¯ is absorbed • More in liquid diet than in solid (80% in solid, up to 97% in water) • Half-time for absorption is 30 min • Peak plasma concentration – 30 – 60 min. • Ionic form-- relevant to health • Fat soluble form • Calcium in diet reduces absorption • 99% of body burden is assoc. with calcified tissues • 50% will be assoc. within 24 hr – Rest is excreted through urine Distribution of Fluoride • Teeth and skeleton have the highest concentrations of fluoride -affinity of fluoride to calcium. • Fluoride content of teeth increases rapidly during early mineralization periods and continues to increase with age, but at a lower rate. Fluoride in Dentistry • The application of fluoride in dentistry can be considered under the following: • Control of dental caries • Fluoride toxicity • Dental fluorosis Fluoride in Caries Control • The effect of fluoride in caries prevention can be considered under two headings. • Pre-eruptive effect • Post – eruptive effect Pre-Eruptive Effect • Improved crystallinity - Changes the crystalline structure of enamel to make it less soluble. • Increased Crystal size • Less acid solubility • More rounded cusps and fissures • Overall effect is small because discontinuation of fluorides leads to increased caries – constant servicing!!! Pre-Eruptive Effect • Changes the crystalline structure of enamel to make it less soluble. OLD CONCEPT • That major inhibitory effect was thought to be due to its incorporation in tooth mineral during the development of the tooth prior to eruption • Recent evidences shows that the main effect of fluoride in caries prevention are the post-eruptive - through Topical effect. • Fluoride incorporated during mineral development at normal levels of 20- 100ppm does not alter the solubility of the mineral. • Fluoride incorporated developmentally into the normal tooth mineral is insufficient to have a measurable effect on acid solubility. • Only when fluoride is concentrated into a new crystal surface during Remineralization, is it sufficient to alter solubility beneficially. Post-Eruptive Effect • Effect is seen when fluoride is present in plaque and saliva. • There is now clear evidence that caries reduction is most effective when a low conc. Of Fl is maintained consistently in the oral environment. • This is in contrast to earlier concept • Attributed the major benefit of Fl to pre-eruptive maturation of forming enamel • Predominant effect is TOPICAL rather than systemic • Interferes with glycolysis – Bacteria metabolizing sugars to acid by inhibiting enolase and proton pump ATPase. • Inhibit the glycolytic pathway of oral microorganisms reducing acid production and interfering with the enzymatic regulation of carbohydrate metabolism. • Also reduces the accumulation of intracellular and extra-cellular polysaccharides • This bactericidal action occurs only at higher concentrations. • These inhibitory mechanisms are affected by the hydrogen ion concentration of plaque. • A decrease in pH results in a greater inhibitory action on bacterial carbohydrate metabolism which occurs due to • Unionized hydrofluoric acid formed at lower pH values • Fluoride can not cross the cell wall and membrane in its ionized form(F-) but can rapidly travel through the cell wall and into the cariogenic bacteria in the form of HF. • Fluoride in the presence of plaque bacteria generated acid, travels with the acid into the subsurface of the tooth, adsorb to the crystal surface and protect it from being dissolved. • Once inside the cell ,the HF dissociates again acidifying the cell and releasing fluoride ions that interfere with enzyme activity in the bacterium.Interferes with glycolysis Summary of Fluoride Anti-caries Activities • Fluoride prevents demineralization. • Formation of fluorohydroxyapatite and inhibition of mineral loss from enamel. • Fluoride enhances remineralization • Through formation of a fluoride reservoir and creation of supersaturated solutions. • Fluoride alters the action of plaque bacteria. • At low pH, fluoride combines with hydrogen ions and diffuses into oral bacteria as hydrogen fluoride (HF) Inside the cell HF dissociates, acidifying the cell and releasing fluoride ions that inhibit glycolysis. • Fluoride aids in post eruptive maturation of enamel. • Fluoride reduces enamel solubility. Fluoride Application Systemic fluoride Sources • Water and other beverages. • Food • Fluoride drops • Fluoride tablets Water Fluoridation • It is the controlled addition of fluoride to public water supply to bring its fluoride concentration up to an optimal level to prevent dental caries. • Also defined as controlled adjustment of the concentration of fluoride in a communal water supply so as to maximize caries reduction and a clinically insignificant level of fluorosis. • It is also an upward adjustment of the concentration of fluoride ion in a public water supply in such way that the concentration of fluoride in the water may be consistently maintained at 1 ppm by weight to prevent dental caries with minimum possibility of causing dental fluorosis. • Most effective, safest and cheapest way of reducing caries. • Recommended level of fluoride for community water supply ranges from 0.7-1 ppm depending on the mean maximum temperature. • At this level, fluoridated water is odourless and tasteless. • It results in 20-40% reduction of caries over a life time • It does not confer life time immunity • The adsorption of fluoride to the enamel surface is greatly influenced by concentration and temperature. • Hence the, fluoride concentration in public water supply is adjusted according to the average atmospheric temperature (temperate /tropical region) • WHO recommended (1994)- 0.5 to 1.0 ppm Simple modified method to determine optimum fluoride concentration and mean annual temperature. Richard et.al • The use of water fluoridation dates back to the 1900 following the discovery of the a mystery staining of teeth by Dr. Fredrick Mckay in Colorado Boulder. Advantages • Most economical and cost effective measure for reduction of dental caries • It is practicable because it requires no individual effort. • Offers both pre-eruptive and post-eruptive effects • Topical effect through release in saliva Disadvantage • It requires an effective and central water supply system • Freedom of choice is removed • Requires a complex infrastructure • Initial capital outlay School Water Fluoridation • Suitable alternative to community water fluoridation • 4.5 to 6.3 ppm Advantages • Effective public health measure-when community water supply is not possible Disadvantages • 5 to 6 years old upon starting school- will not provide pre-eruptive contact • Intermittent fluoride exposure-less than 180 days in a year Salt Fluoridation • The controlled addition of fluoride to domestic salt during manufacture for the purpose of preventing caries. • Concentration is based on estimate of salt consumption and evaluated by studies of urinary fluoride concentration • 1st used in Switzerland in 1955 • Concentration of 250mg/kg salt recommended (250ppm for adults and less for children) • Caries protection may be as good as water fluoridation • Commonly used material is Potassium Fluoride Salt Fluoridation Advantages • • • • Low cost Negligible waste Ease of implementation Freedom of choice for individuals Disadvantages • Fluoride dosages of different age in different regions • Lower salt consumption during tooth forming years • In conflict with general health message of low salt intake for prevention of coronary heart disease Milk Fluoridation • First mentioned by Ziegler in 1956 • Limited Effect as a public measure • Topical fluoride effect less than water because of binding to calcium or protein in the milk. Advantages • Need to drink under 14 years of age Disadvantages • Incompletely ionized in milk • Lower absorption from milk than water • Variation in intake • Requires parental or school efforts • Technical difficulties • Problem in distribution • High cost Dietary Supplement • Can be in form of tablets, drops, in 1.0mg, 0.5mg and 0.25mg preparations • Most of them contain neutral NaF. • Dose is 0.5mg F/day in children ≥ 3yrs • Results in 40-50% reduction in caries experience Advantages • Effective • Freedom of choice Disadvantages • Compliance needed for consistency • Risk of over dose is high Topical Fluoride • These are placed directly on the teeth. • Some preparations provide a high concentration of fluoride over a short period of time. • Other preparations such as dentifrices provide continuous low concentration of fluoride on the teeth. • Topical fluorides allow for the interaction of fluoride with minerals in the teeth. Indications for Topical Fluoridation • Caries active individuals • Children shortly after the period of teeth eruption. • Those who are on medication which decrease the salivary flow or who have received radiation to head and neck. • After periodontal surgery when the roots of the tooth are exposed. • Patients with fixed or removable prosthesis after placement or replacement of restorations. • Mentally and physically challenged patients. • Patients with an eating disorder or who are undergoing a change in lifestyle which may affect their oral hygiene habits. Rationale for Topical Fluoridation • To speed the rate and increase the concentration of the fluoride acquisition above the level which occurs naturally. • The initial caries lesion characterized by a white spot is porous and accumulates fluoride at a much higher concentration than the adjacent sound tooth enamel. Topical fluorides are divided broadly into 2 main categories Professionally Applied • Introduced by Bibby in 1942. • Dispensed by dental professionals in the dental office and usually involve the use of high fluoride concentration products ranging from 5000-19000 ppm which is equivalent to 5-9mgF/ml. • The three agents currently in use are: 1) Neutral Sodium Fluoride (NaF) 2) Acidulated Phosphate Fluoride (APF) 3) Stannous Fluoride (SnF2) Advantages • Effective and useful for individuals at high risk of dental caries • Freedom of choice Disadvantages • Need for personnel • Time consuming • Requires access to service Indications • • • • • • • • Caries prone children >6 years of age Patients with initial carious lesions For nervous patients, varnish is easy to apply Medically and physically disabled For early childhood caries Fluoride varnish can reduce hypersensitivity in root caries Patients with orthodontic appliances who cannot or will not use fluoride rinses Patients with reduced salivary flow due to salivary gland dysfunction, drugs or radiotherapy Contraindications • Due to high fluoride concentration, it is not ideal for home use • Not for children < 6 years who cannot spit out Forms of Topical Fluoride • Aqueous Solutions And Gels • The gel adheres to the teeth for a considerable amount of time and eliminates the continuous wetting of the enamel surfaces required when solutions are used. • When gels are applies using trays, it is possible to treat two or four quadrants simultaneously and saves time. • Each application is loaded by using a thin layer, thereby reducing the risk of accidentally ingesting a large quantity of fluoride. • Thixotropic solutions are more stable at lower pH and do not run off the tray as readily as conventional gels. • FOAMS • Foam based agents were developed to minimize the risk of fluoride over dosage as well as to maintain the efficacy of topical fluoride treatment. • Advantages of foam based APF agents are: • It is much lighter than a conventional gel and therefore only a small amount agent is needed for topical application.(4gm of gel/mouth while less than 1gm of foam/mouth). • The surfactant in the foaming agent has cleansing action by lowering the surface tension. • It may also facilitate the better penetration of the material into inter proximal surfaces where its action is most needed. • Since APF foams does not require suctioning, it offers advantages for home use as well as treatment of young children and disabled persons where saliva evacuation may not be feasible. • FLUORIDE VARNISH • It was first developed by Schimdt in Europe in 1964. • Increasing the time of contact between enamel surface and topical fluoride agents favors the deposition of fluoro-apatite and fluorohydroxyapatite. • Technique Used: • After prophylaxis, the teeth are dried but not isolated since varnish can stick to cotton. • 0.3-0.5ml of varnish is required to cover full dentition. • Application is done first on lower arch then upper, using single tufted small brush, starting with the proximal surfaces. • Patient is asked to sit with mouth open for 4 min to let it set. • The patient is asked not to rinse or drink for 1 hour. • Examples of Fluoride varnish preparations: • Duraphat • It is the first fluoride varnish developed in Germany. • It is a viscous yellow material containing 22,600 ppm fluoride as sodium fluoride in aneutral colophonium base. • It has shown 30%-40% caries reduction in permanent dentition and 7%-44% reduction in primary dentition. • Carex • It is also a fluoride varnish containing low fluoride concentration than Duraphat (1.8% fluoride). • It has the efficacy equal to that of Duraphat as caries preventive agent Technique of Application • Knutson’s techniques • At the initial appointment the teeth are cleaned with aqueous pumice slurry and then isolated with cotton rolls and dried with compressed air. • Using cotton tipped applicator sticks, 2% sodium fluoride solution is painted on the air dried teeth so that all tooth surfaces are visibly wet. The solution is allowed to dry for 3-4 minutes. • Advice patient not to eat or drink for the next 30 minutes • The procedure is repeated for each of the isolated segments until the teeth are treated. • A 2nd ,3rd and 4th fluoride application, each not preceded by a prophylaxis, is scheduled at intervals of approx. 1 week. • The four-visit procedure is recommended for 3, 7, 11 and 13 years, coinciding with the eruption of different groups of primary and permanent teeth. • MUHLER’S TECHNIQUE • commonly for Stannous fluoride application • Each tooth surface is cleaned with pumice or any other dental cleaning agent for 5-10 seconds. • Unwaxed floss is passed between the interproximal areas. • Teeth are isolated and dried with air. • SnF2 is applied using paint-on technique and the solution is kept for 4 minutes. • Repeat applications are made every 6 months or more frequently if the patient is susceptible to caries. • Tray technique • The patient should sit upright in the chair. • Oral prophylaxis is done. • The teeth to be treated are completely isolated and dried with air. • Clinical application of APF gels should be done using trays that fit into the patient’s upper and lower arches. • A disposable foam-lined tray is preferred. • To reduce ingestion of fluoride, a minimum amount of fluoride gel that will permit complete coverage of the tooth surfaces should be dispensed. Usually, the amount is less than 5 ml • After the trays have been properly positioned, saliva ejector is used to evacuate the stimulated saliva and excess fluoride. • It is repeated every 15-30 seconds so as to keep the teeth most with the fluoride solution throughout the four minute period. • The patient should be told not to swallow the gel but to exert slight pressure using the cheeks and tongue as well as light biting force in order to cause the gel to flow interproximally. • The fluoride gel should be in the mouth for 4 minutes and then the remaining oral fluid must be expectorated. • The patient is instructed not to eat, drink or rinse mouth for 30 minutes. Self Applied • Low concentration fluoride agents • Dentrifices • Fluoridated toothpaste • Mouthrinses Fluoride toothpaste • The commonest and most widely used. • The simplest method of fluoride delivery. • World wide decline in caries experience has been attributed to widespread use of toothpaste. • Many of the toothpastes contain Sodium monofluorophosphate. • First fluoride dentrifice accepted by ADA in 1964 • Demonstrated caries reduction of about 30% • The concentration of fluoride in toothpaste varies • The standard and most frequently used toothpaste contains 1,000 to 1,100ppm of fluoride • Toothpastes containing 500 to 550ppm fluoride (pediatric toothpastes) Recommendations • Containers should be labeled with the concentration of fluoride in ppm • Containers should be designed to limit the amount of paste dispensed • Individuals should brush twice daily Fluoride Mouth rinse Recommendations • Usually formulated at concentrations of either 0.2% for • Should not be used in children younger than 6 years weekly use or 0.05% for daily use. • Should only be used in high risk children • They are intended to be used by • Appropriate for patients with orthodontic appliances or forcefully swishing 10ml of liquid radiotherapy treatments around the mouth for 60 seconds before expectorating it. Fluoride Toxicity • Fluoride toxicity can be • Acute • Chronic Factors that affect toxicity of fluoride • Concentration • Duration of exposure • State of nutrition (calcium, magnesium) Acute toxicity • Acute fluoride toxicity results from rapid excessive ingestion of fluoride at a given time. • Children younger than 6 years account for the vast majority of the cases. • The acute lethal dose for an adult is suggested to be 32-64 mg F/kg, and in children it is 5mg F/kg. • Certainly lethal dose (CLD): Amount of drug likely to cause death. • Adult = 5-10 g NaF taken at one time or 32-64 mg F / Kg body weight. • Children = 2.5 g of NaF • Once absorbed, fluoride binds calcium ions and may lead to hypocalcemia. • Fluoride has direct cytotoxic effects and interferes with a number of enzyme systems: • It disrupts oxidative phosphorylation, glycolysis, coagulation, and neurotransmission (by binding calcium). • Fluoride inhibits Na+/K+ -ATPase, which may lead to hyperkalemia by extracellular release of potassium. • Fluoride inhibits acetylcholinesterase, which may be partly responsible for hypersalivation, vomiting, and diarrhea (cholinergic signs). Acute toxicity • Signs and symptoms 1.Gastrointestinal signs predominate • Hypersalivation • Nausea • Vomiting • Diarrhea • Abdominal pain • Dysphagia • Mucosal injury 2. Electrolyte abnormalities Hypocalcemia Hypomagnesemia Hyperkalemia 3. Neurologic effects • • • • • • • Headache Tremors Muscular spasm Tetanic contractions Hyperactive reflexes Seizures Muscle weakness 4. Cardiovascular • Widening of QRS • Various arrhythmias • Shock Management of Acute Fluoride Toxicity Immediate cases: • Aimed at reducing fluoride absorption by inducing vomiting, fluid replacement, monitoring levels of plasma calcium and potassium. More than 5mg/kg fluoride ingested • Empty the stomach by inducing vomiting. • Give milk, 5% calcium gluconate orally and hospitalization. Less than 5mg/kg fluoride ingested • Give milk. More than 15mg/kg fluoride ingested • Immediate Hospitalization, Induce vomiting, Cardiac monitoring, Slow administration of 10% calcium gluconate-IV. • Maintain urinary output-using diuretics if necessary, supportive measures for shock. Chronic toxicity • Fluoride ingested in small doses over a long period time results in changes in the teeth and bone. • These changes are called fluorosis. Fluorosis • Dental fluorosis • Skeletal fluorosis Dental Fluorosis • Occurs as a result of hypo-mineralization of enamel due to the ingestion of excess fluoride during tooth development. • The severity of fluorosis is dose, duration and time dependent. • The occurrence of enamel fluorosis is most strongly associated with cumulative fluoride intake during enamel development • This is especially during the early maturation stage of enamel development. • The time for early maturation (enamel calcification) varies from tooth to tooth • Upper central incisor has the most sensitive period for fluorosis as 1524 months for boys and 21-30 months for girls • Risk of enamel fluorosis is limited to children aged 8 years and below ( 6 years and above, teeth are spared) • Children aged 6 years (posterior teeth can be affected at this period). • By age 6 years, most children can control inadvertent swallowing of fluoride rinses and gel. Measurement of fluorosis: indices • Various indices have been developed to measure dental fluorosis. This includes: • Deans Fluorosis Index(original-1934 and modified-1942) • Thylstrup and Fejerskov index for fluorosis • Fluorosis risk index • Tooth surface index of fluorosis. Deans Fluorosis Index(original-1934 and modified-1942) • Formulated by H. Trendley Dean in 1934 • The first Fluorosis Index for categorizing dental fluorosis. • Based on a 7-point ordinal scale: normal, questionable, very mild, mild, moderate, moderately severe, and severe. • Was modified in 1942 in which moderately severe" and "severe" categories were combined. • A new 6-point ordinal scale was released and it is extensively used today. • It is also this version that is still recommended by the World Health Organization (WHO) in its basic survey manual (Burt and Eklund, 1999; World Health organization.1997) • Assessment to be done under good sunlight facing the window. Thylstrup and Fejerskov index(TFI) for fluorosis 1978 It is the most sensitive of the indices since it calls for drying which accentuates the appearance of fluorosis Water De-fluoridation • De-fluoridation means to improve the quality of water with high fluoride concentration by adjusting the optimal level in drinking water. Methods of water defluoridation • Absorption and ion exchange method • Exchange negative ions such OH- group for fluoride ions depends up on PH, temperature, flow rate, grain size of the material. • Commonly used materials: activated alumina, activated bauxite, Zeolite, Tricalcium phosphate, activated bone char, magnesite, magnesite etc Precipitation method: • In a high PH condition, coprecipitation of several elements in water with fluoride ions forms fluoride salts- flocculation • Examples: • Alum • Alum and lime • Lime softening • Calcium chloride Membrane separation • Reverse osmosis process • Expensive developing countries • 30% of raw water is lost in the process Nalgonda Technique • Invented in India in 1975 • Most simple • Least expensive • Easiest to operate • Can be applied at the domestic and community levels • Cost effective • Flexible design to use in different location Conclusion • Fl when used appropriately fluoride is a safe and effective agent that can be used to prevent dental caries. • Appropriate fluoride intake in different population groups in different areas has to be ascertained on the basis of fluoride concentration in food and water resources taken by the local population. References • Fejerskov, J. Ekstrand, Brian. Fluorides in dentistry. 2nd edition. • Mellberg and Ripa. Fluorides in preventive dentistry. 1st edition. • John Murray, Rugg. Fluorides in caries prevention. 3rd edition. • Update on the use of fluoride-S.Joyston-Bechal and E.A.M Kidd • European Academy Of Paediatric Dentistry-guideline on the use of fluoride in children • Lauer WC. Water Fluoridation Principles and Practices. 5th ed. Vol. M4. American Water Works Association • 2017 August WACS Update • Hussain J and Sharma KC. Environmental Monitoring and Assessment. March 2010, Volume 162, Issue 1, pp 1-14. • Textbook of community Dentistry, TR Gururaja Rao. 2004 edition. • Rajan et al 1987,1988, Use of fluoridated toothpaste - Blood fluoride levels in children, International society of fluoride research. • American Academy of pediatric dentistry,1967, revised in 2014. Reference manual , Vol 37 No.6. Question • The sensitive year for fluorosis is fouth year. • Indication for topical fluoride application. • Concentration of fluorde in Naf, SnF, APF • Is prophylaxis needed before topical fluoride • Content of a dentrifices