The role of fluoride in caries prevention Flashcards
how does fluoride prevent caries
- fluoride present in fluid at the plaque/tooth interface promotes remineralisation
- the fluoro-apatite formed is less susceptible to demineralisation
- topical effect greater than systemic (F combining during amelogenesis) effect
- fluoride may also have an effect on bacteria and metabolic pathways resulting less acid being produced
- maintain elevated oral levels of fluoride for as long as possible (little and often)
- fluoride most effective on early lesions
what are the oral reservoirs for F
2 broad types:
- mineral deposits (CaF2 in saliva and fluid phase of plaque)
- biologically/ bacterially bound calcium- fluoride
what is better, systemic or topical?
topical is better
why is water floridation good
universal and passive
ingest water, F becomes incorporated into saliva
what are different methods for delivering F in oral care products
- toothpaste
- mouth rinses
- varnishes and gels
- tablets
what is the amount of F in fluoridated water
0.8-1.0ppm
how effective are F mouthrinses
- commonally avaliable for home use as daily or weekly
- reductions in caries of around 30%
- daily rinsing slightly more effective than weekly rinsing, but more expensive
- swishing round mouth important
- good befefit to risk ratio
- generally good compliance
- cost benefit ratio is low
why is F varnish good
- high F concentration (sodium fluoride 50mg/ml = 22600ppm F)
- sustained contact
- professionally applied (any DCP)
how does F varnish work
- colophony resin hardens in contact with saliva to maintain contact of fluoride with the tooth
how does F varnish work
- colophony resin hardens in contact with saliva to maintain contact of fluoride with the tooth
- mobilisation of calcium ions in the enamel
- precipitation of calcium fluoride
- rapid adsorption on tooth surface (enamel and dentine)
- increases F content of enamel up to 77% after a single application
- progressive release of F over several months
How does calcium fluoride work?
- acid attack
- release of F ions
- remineralisation
pH falls in acid attack, F products have a greater bioavaliability is the lower the pH, so the lower the pH the more F is released into the oral environment. Presence of F ions drives equation towards remineralisation
how do acidulated mouthrinses work
- lower the pH the greater bioavaliability of F
- drives F to the tooth surface because of boosting the pH
When are CPP-ACP useful
- useful in markets with no access to high F’s
- can be used at home or in office in trays
- not suitable for people with milk allergies
- more research needed
how can dental materials release F
- glass ionomer/resin modified
- attached to tooth surface
- some early release and slower diffusion through bulk GICs
- small amounts but they are sustained
what are the effects of fluoride at the tooth surface
- presence of F during caries process alters demin/remin dynamics
- partially demineralised crystals act as nucleators
- F ions adsorbed to crystal surface and attract Ca, P so new mineral is formed
- principal mechanism of F in caries control relies upon F in saliva, F at plaque fluid and tooth interface and F in fluids around lesion mineral crystals
- optimised by delivery of F to tooth surface, plaque and plaque fluid; also by maintaining F levels
what are the factors which determine the anticaries activity of F toothpaste
- F concentration
- frequency of application
- rinsing behaviours
- when brushing takes place
how does F concentration affect effectiveness of toothpaste
6-7% reduction in caries for every 500ppm F increase in concentration (really important factor)
how does frequency of brushing affect chance of caries
brushing twice per day or more results in lower caries increments
how does rinsing behaviours affect chance of caries
any rinsing removes excess fluoride but large vol of water reduces the F in mouth. so,
spit dont rinse
what is optimal brushing
- twice daily
- not using a beaker
- 1500ppm F paste
what is sub-optimal brushing
- once daily
- rinsing with beaker
- 1000ppm F paste
what is the difference between optimal and sub-optimal brushing
approx 40-50% difference in caries incidence
how important is the amount of toothpaste for efficacy of F toothpaste
not very important
what are the benefits with using F
- efficacy of F toothpaste clearly demonstrated
- higher F content, more caries prevention
what are the risks with F toothpaste
- despite being topical, inevitable ingestion particularly in young
- increased risk of enamel fluorosis
- risk-benefit assessment between caries prevention and fluorosis risk
what are the risks from ingesting fluoride
Acute toxicity
- very rare
- generally potential problem in very young
Chronic toxicity (fluorosis) - developmental defect of enamel
How much F do young children need to swallow to risk fluorosis?
there is no lower limit below which fluorosis does not occur
- general consensus is ~0.1mg f/kg body weight
- 1mg per day for 1 year old
- 2mg per day for 5-6 year old
- still possible to develop fluorosis at recommended daily intakes of 0.05-0.07 mg f/kg
how does the stomach affect the bioavaliability of F
stomach is at a low pH so the bioavaliability of F is very high, however can be affected by presence of cations in the stomach which reduces the bioavaliability
what increases the chance of fluorosis more, concentration or quantitiy of F toothpaste
quantity (20 fold compared to 3 fold)- see slide
so, best to use small quantity of higher concentration
quantitiy of toothpaste is/isn’t strongly associated with efficacy
isn’t
why is efficacy primarily concentration rather than dose dependant?
because oral fluoride reservoir is small
is it best to brush before or after meals
from a caries point of view: after (most effective at time of cariogenic challenge/less readily absorbed)
from an erosion point of view: before
why is it good to brush before bedtime
salivary flow rate reduced/ increased oral retention
anti caries benefit is topical or systemic?
topical
increased risk of developing fluorosis is topical or systemic?
systemic
what can we do to maximise caries benefit but reduce fluorosis risk in young children
- keep toothpaste out of reach of young children
- brush frequently (2x daily: evening and one other time)
- supervise brushing by young children
- use a small amount (pea/smear) of paste
- discourage swallowing
- brush after meals to minimize effect of F ingestion
- encourage spitting out, remove slurry: avoid excessive rinsing
- maximise f conc in releaiton to risk
what are community prevention tools
Fluoride
- tooth brushing schemes
- F varnish
Diet
- healthy eating policies
- free water/milk
- no sugary drinks
Community at large
- outreach activites (sealants, varnish)
