preventive dentistry
dr.wissam hamied
general mechanisms where by fluoride affects dental caries:
the precise and complete mechanisms of actions f in relation to dental caries are not fully understood. there are three theories present explaining the role.
1st theory (pre eruptive theory):
this is a widely accepted theory claims that when f is taken during the period of tooth formation it may cause changes in composition and morphology of teeth. fluoride ion may replace the hydroxyl group of the hydroxyl apatite crystal forming a new crystal known as fluoroapatite crystal
.
ca10 (po4)6 oh2 + 2f- ? ca10 (po4)6f2+ 2oh-
this reaction is irreversible that is to say once fluoroapatite crystal is formed it will remain so for the life time. the new crystal is more stable and less soluble, and more resistance to acid dissolution. thus fluoride improves the crystallinaty of teeth. these teeth have more rounded cusps and shallower pits and fissures, thus reduce the predisposing factor for dental caries.
ingestion of fluoride in the pre eruptive stage will allow the incorporation of f in the whole enamel and dentin. this will increase the resistance against dental caries in addition reduces the progression of dental caries.
2nd theory (post eruptive theory):
when f is present in saliva and dental plaque it will react with the outer enamel surface to enhance remineralization. two types of reaction may develop the main reaction is formation of calcium fluoride, while the 2nd type of reaction is the formation of fluoroapatite crystal.
ca10 (po4)6 oh2 + 20f- ? caf2 + 6po43- +2oh-
ca10 (po4)6 oh2 + 2f- ? ca10 (po4)6f2+ 2oh-
calcium fluoride is not permanent as it dissociated to calcium and f ions. there for fluoridated products need to be applied continually and at a high concentration, other wise the enamel will be opened to renewed demineralization. these types of reactions can be initiated at any time of subject life.
3rd theory (antibacterial theory):
the presence of f in high concentration (more than 40 ppm) in dental plaque may affect the growth and fermentation of bacteria. these by:
-interference with bacterial adherence by retardation of extra cellular poly saccharide.
- f affect metabolism of bacteria by inhibition of intercellular enzymes as enolase and phosphotase.
-change the microbial composition of dental plaque.
fluoride can react with sound enamel or carious surface, it can applied systemically or topically.
fluoride is highly reactive with carious enamel tooth because the later may allow greater penetration of f ion, this may explain hight conc. of f in sub surface area compare to o.e.s.
so f enhance remenerilization of initial caries and arrest the carious lesion. so don’t open initial carious lesion and apply fluoride harder than sound enamel this depend on 1. dietary habits 2.oral hygiene.
fluoride therapy :
systemic fluoridation
1.communal water fluoridation
2.school water fluoridation
3.flouridated tablets
4. fluoridated milk or juice
5. fluoridated salts
topical fluoridation
1. professional
2. self apply
systemic fluoridation
history:
at the beginning of the 20th century (1901), dr fredrick mckay noticed that many of his patients who had lived in colorado spring (colorado usa) had a permanent stain on their teeth named as colorado stain. he noticed also it low caries severity among those patients. in 1902 eager noticed the same stain upon italian people migrates from naples, italy. he found that only people born and livid all their lives in that area had this deformity that is mottled teeth. in 1931, churchill showed a presence of high concentration of f in area with mottled teeth, but yet no correlation was found. trendily dean discovered that f concentration in drinking water affected the severity of mottling and dental caries severity. he conducted a series of studies regarding level of f in water and severity of dental caries in 21 cities among 7257 person, 12-14 year olds. two important conclusions were reached:
-the number of carious teeth and concentration of fluoride is inversely related.
-the amount of f in the water and mottled enamel are directly related.
the condition of mottled enamel was changed to endemic dental fluorosis.
dental fluorosis:
it is a developmental hypoplastic defect caused by excessive fluoridation during the period of tooth formation. it is the 1st sign of chronic toxicity appears clinically as a white spots or lines involving incisal edge or cusps of posterior teeth or as a white opaque or brown area, in sever cases a corroded appearance will occur. changes in human enamel have been examined using light and electron microscopy. in principle increased exposure to f during period of tooth formation leads to increase enamel porosity. in sever cases the fluorotic teeth are highly porous because of increase of inter crystalline spaces these spaces are occupied by water and protein more than enamel. the fluorosed teeth contain more immature protein. in more sever condition changes involve enamel as well as dentin. after eruption of teeth, although the surface layer is well mineralized it is susceptible to mechanical trauma leading to break down of the outer enamel surfaces.
the exact cause of this hypoplasia is not clear it may be attributed to:
1- altered metabolism in any or all phase of the enamel formation.
2- altered ameloplastic activity.
3- interference with crystal nucleation or growth.
4- faulty enzymatic factor.
factors affecting severity of dental fluorosis:
1- fluoride concentration in drinking water: a direct relation ship is present between dental fluorosis and level of f ingested.
2- total amount of fluoride ingested: f ingested from water, food, inhalation because of pollution all affect severity of dental fluorosis. the total amount of water in take is affected by temperature. in hot area, there is an increase ingestion of f due to increase intake of water thus increasing the risk of dental fluorosis, the opposite is true in cold area.
3- duration of exposure to fluoride: excessive intake of f for a long time as eight years during the period of tooth formation may increase the severity of dental fluorosis. teeth mineralized early in life develop less dental fluorosis, thus posterior are affected more than anterior, also primary teeth are affect less severely compared to permanent teeth, due to shorter maturation period. in addition enamel maturation and calcification of primary teeth take place in the intra uterine life, and the placenta do regulated the amount of f reaching the fetus, also f concentrated in bones of the mother and the fetus more than teeth.
4-others: dental fluorosis was found to increase among children with mal nourishment. the exact cause for this is not clear.
the optimal level of fluoride:
dean conducted his study among 7257, 12 - 14 year- old in seven cities in usa. this was to explore the association between f level in drinking water and severity of both dental caries and dental fluorosis. in measuring dental fluorosis a special index was applied called community index of dental fluorosis, dividing the condition in to different categories according to severity by weight (normal, questionable, very mild, mild, moderate and sever). while the dmf index was applied for recording dental caries. results reveled a maximum reduction of dental caries at a level of f of (1 ppm), at this level dental fluorosis will involve 10 % of the population, but it is of the very mild type with no practical aesthetic significance. increasing f level in drinking water will cause a dramatic increase in dental fluorosis but with no further reduction of dental caries. thus the optimal level is (the level of f in drinking water causing maximum reduction of dental caries but with no clinical signs of dental fluorosis). epidemiological and observational studies however showed that a more sever dental fluorosis do develop some times in certain area of hot climate at one part per million, thus the optimal level of fluoride was changed to 0.6 - 1.2 ppm according to the temperature. in winter is 1.2 ppm and in summer is 0.6 ppm.
1 ppm (0.7-1.2 ppm)
0.5-1.5 ppm
air temp recommended dose
< 18.3 1.1-1.3ppm
18.9-26.6 0.8-1.0ppm
> 26.7 0.5-0.7ppm
communal water fluoridation:
it is the controlled or artificial adjustment of the level of f in a communal water supply to achieve maximum reduction of dental caries and clinically no significant level of fluorosis. fluoride was 1st added to water supply in 1945 in grand rapids (michigan) while muskegon was the control. caries reduction was reported to be 55%.
in usa, now more than 126000,000 people are receiving systemic fluoridation. it is also applied in europe and other countries. chemicals used are sodium fluoride, calcium fluoride, hydro fluorosilicic acid, sodium silico fluoride etc. these materials are added to water by an automatic feeding apparatus and concentration of f is continuously adjusted.
from different epidemiological observation studies concerning water fluoridation it was concluded that:
1- artificial water fluoridation is effective in caries reduction in similarity to naturally fluoridated area.
2- caries reduction involved primary, permanent teeth as well as root caries. the reduction is more in permanent teeth compared to primary because of their shorter maturation period, also its more reduction in smooth surface rather than occlusal surface.
3- communal water fluoridation is a public health measure. all people in the community can gain the benefits from water fluoridation. no effort is needed by recipients to prevent caries.
4- it is a cheap and successful measure of prevention.
5- a reduction in periodontal disease was also reported in fluoridated area.
alternative to systemic water fluoridation
the communal water fluoridation is a successful method for the prevention of dental caries. in presence of objection against this method or there is no piped water supply as in rural area, there are alternative methods to flouride provide systemically. these are:
1- school water fluoridation (or home water fluoridation).
2- dietary fluoride supplements by:
a- fluoridated tablets (dropings or lozenges).
b- fluoridated salt.
c- fluoridated milk (or juice).
school water fluoridation:
this method was first applied in usa, 1954, in which the f content of the water supply was adjusted for the prevention of dental caries. the optimal level of f here is about 4.5 times the optimal amount in the community.
this is because:
-children spend only a part of their total waking hours in schools.
-they enter the school at 6- year of age, thus the incisors are no longer at risk of dental fluorosis.
-only a part of daily water intake is consumed.
-there is holiday and weekends.
for all of the above and to compensate for the part exposure to f, the level of fluoride in school water supply increased.
special equipment can be used for the addition of f, which should be adjusted continuously by well trained employee.
advantages of school water fluoridation:
- technically feasible.
-low in cost.
- no effort is needed by the recipients.
the disadvantage of this method
-the fluoridation started late in life, that is at 6 years of age,
-there is an interruption of fluoridation due to holidays and week ends.
a maximum benefit of systemic water fluoridation is by early intake of f from the first years of life till 13-15 yeas of age.
the home water fluoridation is also of beneficial in caries prevention however the level of water is in similarity to communal water fluoridation.
fluoridated supplements:
1- tablets, dropings and/or lozenges:
this is especially prescribed for children with high risk to dental caries, handicapped
children, or those with serious illness as blood disorder.
this method is an effective measure to prevent or reduce dental caries provided to be taken daily from birth, or the first years of life till 13- 5 years, caries reduction can reach 50 -80%. a variety of supplements are present in form of naf.
-liquid form for infants and young children, concentrations are 0.125 mg fi droping, 0.25 mg fi droping, and 0.5 mg fi droping.
-liquid form with vitamins as a, d, c, e, e,. b1, b3, b6, bi2 and iron, prescribed to mal nourished children only.
-tablets with or with out vitamins, it can chewed the swallowed.
-for school children more than 6 years of age a mouth wash fluoride of 5 ml can be used. the child is asked to rinse his mouth first for one minute then swallow to have a topical and systemic effect.
note: supplements should be given daily, not with milk.
in prescription of f tablets several important factors should be taken in consideration.
-f content of the water supply, (communal or bottled water). applied only in non f area or those with low f level.
-age of the child.
-co operation of parents.
fluoridated tablets (dropings).
naf, 2.2mg (1 mg f).
1.1 mg (0.5 mg)
age conc.
0-2 yr. 0.25 mg/daily
2-4 yr. 0.5 mg/ daily
4- yr. 1.0 mg/ daily dropings: 10 dropings= 1 mg f/ l = 1ppm
• another program
- started at 3 years of age give 0.5 mg/day till 13 - 15 years.
- in presence of dental caries (0.25 mg/day till 3 years) then 0.5 mg/ day till 13-15 -years.
instruction :
1. given daily (once or twice).
2. tablets crushed between teeth.
3• each bottle contains not more than 264 tablets, to avoid acute toxicity after the accidental ingestion of fluoride tablets.
4- dentifrices used should be with out f, or with a low concentration.
fluoridated salt:
it was introduced first in switzerland, 1955. it is considered next to water fluoridation regarding caries reduction. f is added to salt inform of naf or caf2 in different doses, 200, 250, 350 mg f/ kg of salt for domestic use or bakeries.
advantages of salt fluoridation are:
-low cost
-ease of implementation
-no personal efforts is needed.
-effective in caries reduction for permanent as well deciduous teeth.
disadvantage children would start to use salt too late in life, or they used to take small amount of salt.
fluoridated milk:
human and bovine milk contain a low level of f about, 0.03 ppm. milk is a good food for infant and children, it is a suitable vehicle for supplementary f to children, it is an excellent source for calcium and phosphorous in addition to vitamin d. milk is essential for development of bones and teeth.
the bioavailability of f from milk is in similarity to water, other studies showed that milk may retard the absorption of f from git, but does not prevent f absorption.
fluoridated milk can be used in home and school programs, with caries reduction of70%.
the disadvantages of milk fluoridation are the high cost. some children dislike milk, for them a fluoridated juice can be used.