fluoride and mineralised tissues - topical aspects Flashcards
how many fluoride be delivered topically??
- Dentifrices
- Mouthwashes
- Gels / foams / varnishes
- Implantable / Restorative materials, such as copolymer membranes and glass ionomer cements
how many fluoride be delivered systemically
- Salt
- Fluoride supplement tablets
- Fluoridated water supplies
what is the optimum level of fluoride and what does this value have to take into account?
1mg/litre or 1ppm
- maximum dental caries protection
- minimum dental fluorosis
at what stage of life and during what challenges is fluoride application most important and beneficial?
- post-eruptively
- in aqueous phase
- during caries challenge
topical application is more beneficial in reducing caries challenge
what potential mechanisms are there of fluoride reducing caries
- Fluoride alters structure of the developing enamel making it more resistant to acid attack
- ???
- Very little fluoride is incorporated into developing mineral
- ???
- Fluoride reduces the ability of bacteria to produce acid
- ++
- Topical exposure to fluoride encourages remineralisation with the formation of fluorapatite
- ++ ++
antibacterial effect of fluoride
- inhibition of enolase
- causes build up of 2-phosphoglycerate
- therefore no generation of lactic acid
- inhibition of ATPase
- protons are not pumped out of the cell
- does not go through proton motive force
- therefore no glucose taken up by the cell
- this leads to ATP not being replaced
- therefore glycolysis is slowed and stopped
- bacterial cell is killled
what is the level of fluoride required to induce an antibacterial effect
1-3mM (~120ppm) required in vitro
- as fluoride needs to penetrate through the biofilm and reach bacteria on tooth surface - much higher required
- 1550-1500ppm
- 2 minute exposure
- twice a day brushing
- repeated exposure everyday is recommended
how is fluorapatite formed
advantages over hydroxyapatite?
- Topical exposure to fluoride results in uptake into enamel surface.
- F- substituted for OH;
Ca10(PO4)6(OH)2 +2F- —> Ca10(PO4)6(F)2 + 2OH-
- F- is higher charge density
- tighter crystal structure
- more stable crystal structure
- rapid crystal formation
- lower solubility product
- more resistant to acid dissolution
what is necessary for fluorapatite formation to occur?
a caries challenge
process relies on alternating decreases and increases in pH
how does fluoride pass through pellicle layer?
pellicle layer is hydrophobic and semipermeable
- fluoride must pass through in a net neutral state
- not charged ion
- CaF passeds through and is incorporated into the mineralising crystal
is a high Ca:F ratio better to wound healing or worse?
lower calcium levels result in larger reduction of the carious lesion
- more prolonged deposition of mineral phases
- able to penetrate deeper into the regions of the lesion
- slow mienralisation is better for the end product
how does the structure of enamel influence the action of fluoride?
- enamel lamella and striae of retzius (perikymata at surface)
- provide entry points for fluoride
examples of toothpastes, how they deliver fluoride and their beneficial properties
- Sodium fluoride pastes and gels
- immediate provision of free F-
- Sodium Monofluorophosphate (SMFP) hydrolysed within plaque
- To give and release sodium fluoride
- More insoluble
- Able to penetrate deeper
- Stannous fluoride stannous anti-microbial agent
- So is fluoride -> good
how have amine fluoride been used to deliver fluoride
what is the disadvantages
- Hydrophobic tails prevent impenetrable layer to acid attack
- Disadvantage
- Difficult to have caries challenge required to replace hydroxyapatite with fluorapatite
