Aquafresh Science Academy Fluoride Slide Set
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This presentation summarizes the caries formation process and fluoride mode of action It further discusses the different types of fluoride available and their relative efficacies
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Aquafresh Science Academy Fluoride Slide Set
- 1. Caries Formation and the Effects of Various Fluorides in Treatment ©iStockphoto.com ©iStockphoto.com/Günay Mutlu ©iStockphoto.com/Nina Shannon www.aquafreshscienceacademy.com
- 3. Caries development process ©iStockphoto.com ©iStockphoto.comPeter Nguyen ©Sciencephotolibrary.com
- 4. The five stages of caries development 1,2 1. Collins WJN, et al. A Handbook for Dental Hygienists. 3rd edition. Oxford: Wright, 1992. 2. Clarkson BH, et al. Caries Res 1991;25:166-173. 3. Collapse of surface layer to form cavity Irreversible lesion Possible formation of apical abscess Reversible lesion 1. Initial subsurface demineralization Initial subsurface demineralization Extension of demineralized zone towards dentine Collapse of surface layer to form cavity Extension of caries lesion into dentine Extension of caries into pulp 1 2 3 4 5
- 7. Caries lesions Figure 1. Sectioned, extracted tooth with three caries lesions Figure 2. A single caries lesion showing bacterial invasion in dentinal tubules
- 11. Fluoride mode of action
- 13. Fluoride effect on remineralization and demineralization of enamel 1. Silverstone LM. Clinical uses of fluoride 1985;153-175. 2. Featherstone JD, et al. J Dent Res 1990;69:620-625. 3. Aoba T. Crit Rev Oral Biol Med 1997;8:136-153. 4. Briner WW & Francis MD. Arch Oral Biol 1962;7:541-550. Reduce demineralization 2,3 Inhibit acid generation from plaque bacteria 4 Promote remineralization 1 F-
- 24. Comparison of fluoride performance in dentifrices
Notes de l'éditeur
- Dental caries is a progressive condition characterized by demineralization and destruction of enamel and dentin A major factor in the cause of dental caries is plaque, a sticky film that develops on the surface of teeth, made up largely of bacteria Some of these bacteria, in particular, Streptococcus mutans and S. sobrinus , efficiently metabolize carbohydrates from sugars in the diet to produce lactic and other acids, which demineralize the tooth surface 1 References 1. Duckworth RM. Int Dent J 1993;43:529-539.
- [Insert animation ‘Caries development’] This animation depicts the five stages of caries development, in which a white spot lesion is initially formed, which, if left untreated, can result in decay spreading down into the pulp, leading to inflammation and the formation of an apical abscess
- Dental cavities can occur at a number of sites 1,2 Among children, pit-and-fissure caries represent 90% of all dental caries Root decay is a widespread problem in adults and appears to be increasing This may be because more and more adults are retaining their own teeth into old age. Also, investigation and treatment of periodontal disease exposes the root surface, making the root more susceptible to bacterial attack References 1. Collins WJN and Walsh TF (eds). A Handbook for Dental Hygienists. 3rd edition. Oxford: Wright, 1992. 2. Clarkson BH et al. Effects of phosphoprotein moieties on the remineralization of human root caries. Caries Res 1991;25:166-173.
- Dental caries can occur at a number of sites. Figure 1 shows a sectioned, extracted tooth with three caries lesions at different stages of progression Figure 2 depicts a single caries lesion at higher magnification and after staining. The arrows point to bacteria that have invaded the dentine tubules exposed by the carious lesion. Acid production by these bacteria will lead to further decay
- Demineralization and remineralization is a dynamic process, characterized by the flow of calcium and phosphate out of and back into tooth enamel, which should be balanced in order to prevent the progression of caries The relationship between demineralization and remineralization is influenced by the presence of several factors present in the saliva and plaque (fluid), such as the salivary calcium and phosphate concentration, pH, and bioavailability of fluoride These factors can be either beneficial or detrimental to the mineral Demineralization occurs when tooth enamel (mainly composed of hydroxyapatite) is exposed to plaque acids The rate of demineralization is inversely proportional to the degree of saturation of calcium and phosphate ions and the pH of the solution In the early stages of demineralization, the tooth surface remains intact and demineralization is reversible Remineralization occurs when the pH increases and calcium and phosphate from saliva together with fluoride form new hydroxyapatite crystals on the enamel surface and the body of the lesion Once demineralization reaches a certain stage, the tooth surface collapses to expose a cavity
- In the presence of fermentable carbohydrates (eg, glucose, fructose, starch) organic acids (eg, lactate, acetate) are produced by cariogenic bacteria (streptococci and lactobacilli) in the dental plaque and the oral pH drops Low pH drives the dissolution of calcium and phosphate in the hydroxyapatite crystalline structure of the tooth (demineralization). Initially this dissolution may be reversed by remineralization from calcium and phosphate in the saliva In the presence of low concentrations of fluoride in saliva or plaque fluid, the released calcium and phosphate could reprecipitate as fluorapatite or fluorohydroxyapatite which is less soluble than hydroxyapatite (demineralizes at a pH <4.5) and may provide additional protection from acid attack 1,2 However, if the acidic conditions persist, below a critical pH of around 5.5, the acid-induced dissolution exceeds the remineralization of the saliva. The net result is a gradual loss of tooth mineral, leading to irreversible cavity formation 1 References Arends J, et al. In: Cariology Today. Basel: Karger, 1984. pp245-258. ten Cate JM. Acta Odontol Scand 1999;57:325-329.
- [Insert animation ‘The action of demineralization and remineralization in the mouth’] This animation shows a schematic representation of acid production by plaque bacteria and the resulting demineralization that occurs Repair of the demineralized surface may then follow through salivary replacement of the lost minerals, in a process called remineralization 1 References 1. Ten Cate JM, et al. Crit Rev Oral Biol 1991;2:283-296.
- The benefits of fluoridated water were studied extensively in the 1940–1950, when epidemiologic studies demonstrated that children drinking naturally fluoridated water had fewer caries than those in populations where water supplies were low in fluoride concentration 1,2 Large-scale water fluoridation programmes are now available globally Excessive fluoride ingestion, well exceeding WHO limits of 0.7-1.2 mg/l fluoride, should be avoided because of risk of fluorosis, characterized by a white, mottled appearance of the teeth Other ingested sources (i) a wide variety of food and beverages contain traces of fluoride (ii) Fluoride supplements (tablets, gum) Following demonstration of the effectiveness of fluoride in reducing caries, fluoride toothpastes were introduced in the 1950s Since then, the benefits of fluoride toothpastes, mouthwashes, gels and varnishes have been demonstrated in numerous clinical trials 3 Since the introduction of fluoride-containing dentifrices the incidence of caries has reduced by 9.7–24.9% 4 References 1. Dean HT, et al. Public Health Rep 1942;65:1403-1408. 2. World Health Organization, 2004. Available at: www.who.int/oral_health/media/en/print.html (date accessed: 17 September 2007). 3. Marinho VC, et al. Cochrane Database Syst Rev 2003; CD002782. 4. Twetman S, et al. Acta Odontologica Scandinavica 2003;61;6:347-355(9).
- The anti-caries action of fluoride is due to its favorable effect on tooth remineralization and demineralization 1 Fluoride acts via topical mechanisms which in summary include: enhancement of remineralization at crystal surfaces of the tooth; inhibition of demineralization and inhibition of bacterial enzymes 2-5 References White DJ. J Clin Dent 2001;12:57-62. Silverstone LM. Clinical uses of fluoride 1985;153-175. Featherstone JD, et al. J Dent Res 1990;69:620-625. Aoba T. Crit Rev Oral Biol Med 1997;8:136-153. Briner WW & Francis MD. Arch Oral Biol 1962;7:541-550.
- [Insert animation ‘Fluoride prevents demineralization: The formation of FAP’] Fluoride ions in the saliva and those which adhere to the surface of the enamel can inhibit the dissolution of weak areas by acid HAP is more soluble at lower pH than FAP, in which the OH- ion in pure hydroxyapatite is completely replaced by an F- ion The resultant FAP is more resistant to dissolution by acid Fluoride absorption in carious enamel is greater compared with sound enamel due to the increased porosity and increased surface area of the demineralized regions
- [Insert animation ‘Fluoride prevents demineralization min loss’] If fluoride is present in the saliva, it helps prevent acid dissolution of the enamel crystal surface
- [Insert animation ‘Fluoride promotes remineralization: Formation of a fluoride reservoir’] With fluoride exposure, precipitation of calcium fluoride can take place at the tooth surface, which can act as a reservoir of calcium and fluoride to help prevent demineralization Fluoride can also promote remineralization through the creation of supersaturated solutions, leading to new mineral formation in areas of the tooth enamel that have been demineralized The newly formed tooth surface has a composition somewhere between HAP and FAP, which more resistant to decay Animation - When the outer surface of the enamel is exposed to high concentrations of fluoride calcium fluoride can be formed in considerable amounts, which is precipitated on the enamel surface
- [Insert animation ‘Fluoride promotes remineralization: Creation of supersaturated solutions’] Fluoride in the saliva can be incorporated into the solid crystal lattice to convert hydroxyapatite (HAP) to fluorohydroxyapatite (FAP) As FAP is less soluble than HAP, fluoride acts to increase the thermodynamic driving force for apatite mineralization In supersaturated conditions, this results in remineralization Calcium and phosphate are lost from the tooth as a result of caries challenge. Saliva is supersaturated with calcium and phosphate. The introduction of low levels of fluoride (ca.0.1ppm) to saliva accelerates remineralization which leads to the replacement of lost calcium and phosphate to the tooth from the saliva by driving the thermodynamic equilibrium for crystal growth
- Several in vitro studies have investigated the effect of fluoride on oral bacteria 1-4 and have shown that fluoride is taken up by the bacteria when they produce acid during carbohydrate metabolism Fluoride ions are released inside the bacterium where they have a detrimental and cumulative effect on essential enzyme production References 1. Hamilton IR, et al. Fluoride in dentistry. Copenhagen: Munksgaard; 1996. p23-51. 2. Whitford GM, et al. Infect Immun 1977;11:142-148. 3. Van Louveren C. J Dent Res 1990;69:676-681. 4. ten Cate JM. Acta Odontol Scand 1999;57:325-329.
- Many studies have shown the effectiveness of the various fluoride actives in caries prevention However there is some controversy regarding the relative efficacy of each fluoride source used in marketed dentifrices, 1,2 which particularly applies to the most widely studied sodium fluoride (NaF) and sodium monofluorophosphate (MFP) Stannous fluoride (SnF 2 ) and amine fluoride (AmF) are less common sources, and may also be combined in commercially available dentifrices References 1. Volpe AR, et al. Am J Dent. 1993;6:S13-S42. 2. Sullivan RJ, et al. J Clin Dent. 1995;6:135-138.
- Not all fluoride dentifrices are equally effective, even if they contain equivalent concentrations of fluoride Different fluoride compounds and vehicles can influence fluoride uptake and the anti-caries outcome – stability, availability and bioavailability of fluoride ions are important To be effective in topical formulations (eg, rinses or dentifrices) fluoride needs to be delivered in a soluble bioavailable form so the fluoride ions can penetrate the tooth enamel and enter demineralized areas of the tooth After brushing, salivary fluoride concentrations decrease rapidly to very low concentrations within a few hours
- Enamel fluoride uptake is not just a function of free fluoride availability Ingredients in dentifrice formulations can also influence fluoride uptake and availability, eg, contamination with phosphate or calcium can reduce the amount of fluoride delivered to the tooth pH plays an important role in driving different fluoride processes
- While there have been numerous studies to compare anti-caries effects between the two most common sources of fluoride in toothpastes, NaF and MFP, there is some debate regarding the mechanism of anti-caries action of NaF vs MFP 1,2 In general, clinical studies have shown that NaF is more effective than MFP 3-5 Results of a meta-analysis demonstrated that NaF was 5 – 10% more effective ( p <0.01) than MFP in preventing caries when in an equivalent base formulation 6 This is likely because MFP requires activation by a salivary enzyme to release free fluoride 3 It has been suggested that an MFP/calcium carbonate-containing abrasive base may enhance the anti-caries effect of fluoride present in the dentifrice 7 A study which compared changes in enamel surface microhardness when brushing with a MFP-silica based dentrifrice and a MFP-calcium carbonate based dentifrice showed that MFP-calcium carbonate was more effective than MFP-silica in reducing enamel demineralization and promoting fluoride release in the oral cavity 7 References Stookey GK, et al. Caries Res 1993;27:337-360. Beiswanger BB, et al. ASDC J Dent Child 1989;56:270-280. Bowen WH. J Royal Soc Med 1995;88:505-507. Stephen KW, et al. Int Dent J 1994;44:287-295. Toda S, et al. J Dent Res 2008;87:224-227. Newby CS, et al. J Clin Dent 2006;17:94-99. Cury JA, et al. Caries Res 2003;37:194-199.
- Recent studies have compared the remineralization potential and fluoride uptake of NaF and MFP dentifrices using in vitro and in situ caries cycling models The following fluoride formulations were tested: 1350ppm F- 2700ppm F- 1100ppm F- References Zero DT, et al. Caries Res 2007;41:268-334. Newby EE, et al. 54th ORCA Congress. July 2007, Caries Res 2007;41:328(abs 173). Zero DT, et al. Presented at the 85th General Session & Exhibition of the International Association for Dental Research (IADR), New Orleans, USA, 2007.
- The mean % surface hardness recovery (SD) was: 13.0 (14.0) for the placebo dentifrice; 21.5 (16.1) for dose response control dentifrice; 37.7 (22.9) for NaF (1100ppm F-; Aquafresh Advanced); 28.7 (18.2) for MFP (1100ppm F-) 1 The mean fluoride uptake (SD) was 3.5 (1.5) for placebo dentifrice; 7.8 (3.8) for dose response control dentifrice; 14.9 (7.7) for NaF (1100ppm F-; Aquafresh Advanced); 9.9 (4.7) for MFP (1100ppm F-) NaF (1100ppm F-; Aquafresh Advanced) provided significantly ( p <0.001) greater % surface hardness recovery and fluoride uptake ( p <0.001) than MFP (1100ppm F-) References 1. Zero DT, et al. Caries Res 2007;41:268-334.
- In this in situ caries model, the enamel fluoride uptake and remineralization potential of 2 commercially available dentrifices were compared, which either contained 1350ppm F in an NaF/silica base or 1000ppm F MFP/450ppm F NaF in a dicalcium phosphate base Surface microhardness recovery and fluoride uptake after 14 days were significantly greater with 1350ppm F NaF/silica base than with 1000ppm F MFP/450ppm F NaF/dicalcium phosphate base A dose response relationship between NaF dentrifices with regard to surface microhardness and fluoride uptake was observed References 1. Zero DT, et al. Presented at the 85th General Session & Exhibition of the International Association for Dental Research (IADR), New Orleans, USA, 2007.
- Differences in surface microhardness were observed between the fluoride dentifrices at 10 and 20 days 1 At least 25% increase in surface microhardness was observed with NaF dentifrices than with MFP after 20 days NaF in silica base A (Aquafresh Advanced) was associated with greater increases in surface microhardness and fluoride uptake after 20 days than NaF in silica base B, which demonstrates that different efficacy can result from dentifrices formulated with equivalent fluoride levels and fluoride sources (NaF) because of changes in formulation Differences in microhardness positively correlated with demineralization and fluoride uptake Available fluoride was similar for all test products (900 –1160ppm) All dentifrices tested contained 1100ppm F References 1. Newby EE, et al. 54th ORCA Congress. July 2007.Caries Res 2007;41:328(abs 173).