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Aquafresh Science Academy - Fluoride Slides PowerPoint PPT Presentation

This presentation summarizes the caries formation process and fluoride mode of action

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Aquafresh Science Academy - Fluoride Slides

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Caries formation and the effects of various fluorides in treatment l.jpg

Caries Formation and the Effects of Various Fluorides in Treatment

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©iStockphoto.com/Günay Mutlu

www.aquafreshscienceacademy.com

©iStockphoto.com/Nina Shannon


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Learning objectives

  • To summarise the caries formation process and fluoride mode of action

  • To discuss the different types of fluoride available and their relative efficacies


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Caries development process

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©Sciencephotolibrary.com

©iStockphoto.comPeter Nguyen


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The five stages of caries development1,2

1

Initial subsurface demineralization

Reversible lesion

1. Initial subsurface demineralization

2

Extension of demineralized

zone towards dentine

3

Collapse of surface layer to form cavity

Irreversible lesion

3. Collapse of surface layer to form cavity

4

Extension of caries lesion into dentine

5

Extension of caries into pulp

Possible formation of apical abscess

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.


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The five stages of caries development

  • [Insert animation ‘Caries development’]


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Caries sites

  • Pit-and-fissure caries develop initially in the fissures of the teeth, but can spread into the dentine

  • Smooth-surface caries are most common on interdental surfaces, but can occur on any smooth surface of the tooth

  • Root caries attack the cementum and dentine, which becomes exposed as gums recede


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Caries lesions

Figure 1. Sectioned, extracted tooth with three caries lesions

Figure 2. A single caries lesion showing bacterial invasion in dentinal tubules


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Salivary [Ca2+]

Low pH

Salivary [PO43-]

Salivary [F-]

Demineralization and remineralization

  • Tooth enamel is involved in continuous demineralization and remineralization in the oral environment

  • The progression or reversal of caries depends upon the balance of demineralization and remineralization

Demineralization

Remineralization


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The natural demineralization and remineralization process

  • Cyclical changes in the oral environment result in alternating periods of demineralization and remineralization at the tooth-plaque interface1

Adapted from Aoba T. Oral Dis 2004;10:249-257.

1. Gao XJ, et al. J Dent Res 2001;80:1834-1839.


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The natural demineralization and remineralization process

  • [Insert animation ‘The action of demineralization and remineralization in the mouth’]


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Fluoride mode of action


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Sources of fluoride

  • Topical agents

  • Fluoridated water

  • Other ingested sources

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©iStockphoto.com/Adam Gryko

©iStockphoto.com/ Wolfgang Amri

©iStockphoto.com


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F-

Fluoride effect on remineralization and demineralization of enamel

Promote remineralization1

Inhibit acid generation from plaque bacteria4

Reduce demineralization2,3

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.


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Fluoride inhibits demineralization: Formation of FAP

  • Fluoride prevents demineralization through formation of fluorohydroxyapatite (FAP)

  • [Insert animation ‘Fluoride prevents demineralization: The formation of FAP’]


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Fluoride inhibits demineralization: Helps prevent mineral loss

  • Fluoride prevents demineralization through inhibition of mineral loss from enamel

  • [Insert animation ‘Fluoride prevents demineralization min loss’]


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Fluoride promotes remineralization: Formation of a fluoride reservoir

  • Fluoride promotes remineralization through formation of a fluoride reservoir

  • [Insert animation ‘Fluoride promotes remineralization: Formation of a fluoride reservoir’]


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Fluoride promotes remineralization: Creation of supersaturated solutions

  • Fluoride promotes remineralization through creation of supersaturated solutions

  • [Insert animation ‘Fluoride promotes remineralization: Creation of supersaturated solutions’]


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Fluoride inhibits plaque bacteria invitro1-4

  • 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

  • Fluoride ions inhibit glycolysis

  • As fluoride is trapped inside the cell this becomes a cumulative process

1. Hamilton IR, et al. Fluoride in dentistry. Copenhagen: Munksgaard; 1996. p23-51.2. Whitford GM, et al. Infect Immun 1977;18:680-687.3. Van Loveren C. J Dent Res 1990;69:676-681.4. ten Cate JM. Acta Odontol Scand 1999;57:325-329.


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Types of fluoride


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Types of fluoride overview

  • The use of fluoride dentifrices has reduced the incidence of caries by 9.7%–24.9%1

  • Sodium fluoride (NaF) and sodium monofluorophosphate (MFP) are the most common sources of fluoride in dentifrices

    • These can be used alone or in combination

1. Twetman S, et al. Acta Odontologica Scandinavica 2003;61;6:347-355.2. Volpe AR, et al. Am J Dent. 1993;6:S13-S42.3. Sullivan RJ, et al. J Clin Dent. 1995;6:135-138.


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Fluoride formulation factors and mode of action

  • Not all fluoride toothpastes are the same

    • Different fluoride source, pH and choice of formulation can affect fluoride uptake1,2

  • Fluoride needs to be deposited and slowly released to be effective following brushing3

    • The amount of fluoride released into saliva and adsorbed by enamel during the period after brushing is critical

1. Friberger P. Scand J Dent Res 1975:83;339-344.2. White DJ, et al. Caries Res 1986;20:332-336.3. ten Cate JM. Eur J Oral Sci 1997;105:461-465.


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Factors that influence fluoride delivery

  • Fluoride source (NaF, MFP, stannous fluoride)

    • For example, MFP requires activation by hydrolysis by salivary phosphatase to release active F-

  • Fluoride concentration in formulation

  • Formulation properties

    • pH will drive different fluoride modes of action

    • Ingredients such as divalent cations (eg, Ca2+) can reduce the amount of available fluoride

    • Ingredients such as high levels of phosphates can reduce fluoride uptake


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NaF vs MFP: Supporting studies

  • Fluoride ions are freely available in NaF whereas MFP requires hydrolysis by salivary phosphatase to release free fluoride, the biologically active species1,2

  • In vitro, in situ, animal and clinical studies all support that NaF has superior anti-caries efficacy to MFP in an equivalent silica base formulation

    • A calcium carbonate-based MFP formulation contains abrasive particles which are thought to complement or enhance fluoride efficacy2

    • Meta-analysis of 12 clinical studies: 6.8% clinically and statistically significant greater benefit with NaF vs MFP3

    • Study in adolescents: 7% greater benefit with NaF than MFP4

1. Newby CS, et al. J Clin Dent 2006;17:94-99.2. Lynch RJ, et al. Int Dent J 2005;55:175-178.3. Bowen WH. J Royal Soc Med 1995;88:505-507.4. Stephen KW, et al. Int Dent J 1994;44:287-295.


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Comparison of fluoride performance in dentifrices


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Comparison of marketed NaF and MFP in an in situ caries model1

Results

  • Surface hardness recovery and fluoride uptake were significantly (p<0.001) greater with NaF (1100ppm F) than MFP (1100ppm F) after 14 days of treatment

1. Zero DT, et al. Caries Res 2007;41:268-334.


Efficacy of marketed naf and mfp dentifrices in an in situ caries model 1 l.jpg

Efficacy of marketed NaF and MFP dentifrices in an in situ caries model1

Results

  • Remineralization potential and fluoride uptake were significantly greater for a dentifrice containing 1350ppm F NaF/silica base than for a dentifrice containing 1000ppm F MFP/450ppm F NaF/dicalcium phosphate base

*

*

*

*

Data expressed as least square mean ± S.D. n=39*p<0.01 compared with 1000ppm F MFP/450ppm NaF

  • Zero DT, et al. Presented at the 85th General Session & Exhibition of the International Association for Dental Research (IADR), New Orleans, USA, 2007.


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Surface microhardness changes and fluoride uptake with marketed NaF and MFP in an in vitro caries cycling model1

Results

  • At least 25% greater surface microhardness was observed with NaF than with MFP after 20 days of treatment (p<0.05), as a result of improved remineralization and increased fluoride uptake

  • NaF in silica base A gave greater surface microhardness and fluoride uptake after 20 days of treatment (p<0.05) than NaF in silica base B

  • All dentifrices tested contained 1100ppm F

1. Newby EE, et al. 54th ORCA Congress. July 2007. Caries Res 2007;41:328 (abs 173).


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Conclusions from in situ and in vitro studies comparing NaF with MFP1–3

  • NaF (1100ppm F/silica base) showed greater efficacy with regard to surface hardness recovery and fluoride uptake than MFP (1100ppm F/dicalcium phosphate base) in an in situ caries model1

  • A second in situ study similarly demonstrated that NaF (1350ppm F) in a silica base provided greater remineralization potential and fluoride uptake than a combination of MFP (1000ppm F) and NaF (450ppm F) in a dicalcium phosphate base2

  • This in situ evidence is supported by data from an vitro study.3 Taken together, these results suggest:

    • NaF in silica base provides superior anti-caries potential to MFP formulations

    • Different formulations of NaF in silica base have different remineralization potentials and fluoride uptake

1. Zero DT, et al. Caries Res 2007;41:268-334. 2. Zero DT, et al. Presented at the 85th General Session & Exhibition of the International Association for Dental Research (IADR), New Orleans, USA, 2007.3. Newby EE, et al. 54th ORCA Congress. July 2007. Caries Res 2007;41:328 (abs 173).


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Summary

  • Dental caries is a progressive disease characterised by demineralization (dissolution) and destruction of enamel and dentine

  • Fluoride can reduce caries by preventing demineralization and promoting remineralization of tooth surfaces and can also inhibit plaque acid production

  • Four fluoride sources are used routinely in dentifrices: sodium fluoride (NaF); sodium monofluorophosphate (MFP); amine fluoride (AmF) and stannous fluoride (SnF2)

  • While investigations continue to reveal the relative benefits and mode of action of these different fluoride sources, there is a strong set of data which indicates that NaF is a superior anti-caries agent to MFP

  • Optimizing the base formulation can increase fluoride bioactivity without altering the fluoride level, with the potential to enhance anti-caries efficacy


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