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Fluorides (1).ppt
1. Fluorine is an element of many
mosts:
most reactive of all of the
elements
the most powerful oxidizing agent
most electronegative.
compounds it forms--some of the
most stable and inert substances
known to man
5. Russian word “flor”—Greek “floris”-
destruction.
Latin “fluor”– flow/flux.
13th most abundant element on Earth's crust
6. Fluorine is the most electronegative and
reactive of all elements.
It is a pale yellow, corrosive gas, which
reacts with practically all organic and
inorganic substances
7. History: Fluorine was first identified by
Karl W. Scheele in 1771.
First isolated in 1886 by French chemist F.
Henri Moissan. - Nobel Prize for Chemistry
in 1906.
8. Until World War 2- no commercial
production of elemental fluorine.
Atom bomb projects and nuclear energy
applications -- isotopes of uranium can be
separated through the gas diffusion of UF6
12. Brendt & stearns [1972]
Crystallographic unit cell for apatite- 10Ca,
6 P, 2 Fl ions.
Ionic structure –permits – substitution.
Ca, P & Fl approx same size—maintain size
of the unit cell
14. Soluble Fl –water- nearly completely
absorbed.
solubility of inorg Fl depends on – diet &
Ca content.
Ca & Al compounds– reduces absorption.
15. Excretion
• Urine, sweat & feaces.
• Traces in milk, saliva, tears & hairs.
• Principle route—Urinary Fl- best indices of
Fl intake.
• Severe poisoning –rapid Ur excretion–
protective factor.
16. Spencer etal [1978]—kidney main pathway of
Fl excretion.
Avg intake--3.9mg/day
Ur Fl—30% of Fl—renal ptn
50% of Fl-- normal person
Antacids AlO2– inhibits Fl absorption.
17. storage
In hard tissue– skeletal & dentition
Depends
• amount ingested & absorbed.
• Duration of Fl exposure
• Type, region & metabolic activity of tissue.
18. Uptake of Fl in body tissue
Slightly alters chem.- composition of bone & teeth
minerals.
Three stage mechanism for entry of Fl ion into the
apatite lattice.
• Fl ions exchange with other ions/polarized
molecules—in loosely integrated shell
• II stg: exchange of Fl in hydration shell with anion
group at surface of apatite crystal.
Fl – OH and HCO3
• Surface ions --can migrate slowly –vacant spaces-
recystallization.
20. Historical evolution of Fl
{mile stone studies}
1901, Dr Frederick McKay, Colorado
springs, Colorado, USA.
“Colorado stains”
“minute white flecks, or yellow or brown spots or areas ,
scattered irregularly or streaked over the surface of a
tooth, or it may be a condition where the entire tooth
surface is of a dead paper-white , like the color of a
china dish.”---- ‘mottled enamel’ [McKay, 1916]
1905— St. Louis—no stains
24. “This mottled condtn, in itself, does not
seem to incr the susceptibility of the teeth to
decay, which in perhaps contrary to what
might be expected, because the enamel
surface is much more corrugated & rougher
than normal enamel.”
---McKay 1916
25. Mottled enamel –etiological factor
1918, Dr F McKay & Dr OE Martin.
Britton-1898-water supply changed from
shallow well to deep drilled artesian well
Mysterious element --water
26. 1925, Dr F McKay– change of water supply
from spring water of Great salt lake, Oakley
city, Idaho.
1908—pipeline constructed 5 miles out of
town,
71/2 yrs later– 24 born –free from stains
27. 1928, Dr F McKay & Dr Gromer Kempt –
similar obsv –Bauxite.
1909- shallow well—297 foot well –
children with badly stained teeth.
No mottling – prior to 1909.
28. Mottled En & Fl concn in drinking
water
Mr. Churchill, chief chemist of ALCOA.
[1931]
Looked for trace elements- spectrographic
analysis
Fl level 13.7 ppm in sample from Bauxite
29. Confirmation of Churchill’s findings—
Dr Margaret Smith, Head of Nutr dept &
Mr. Howard smith, agricultural chemist
Experimentally induced mottling --rats
30. Mottled En in UK
Norman Ainsworth 1933 examined 4,258
children –2-15 yrs old- England & Wales.
Moldon –childr –mottled enamel
Gave statistical data—caries experience in Fl
area was lower than average, McKay stressed
the same—caries rate no higher than normal
teeth.
31. 1933, Dr H Trendley Dean—full time
research of mottled enamel—US public
health services.
Ist dental officer –non-clinical assignment.
Task– continue McKay’s work & find the
extent & geological distribution of mottled
enamel in US.
questionnaire
32. Dean & colleagues refr – “Shoe-leather survey”
Developed standard classification of Mottling -
1934.
Aim –minimal threshold of Fl.
1939 Dean & McKay—conclusive –Fl in
domestic water primary cause of human mottled
enamel.
Concluded Dr F McKay search successfully
33. 1939, Dr.TH Dean—hypothesis –inverse
relationship between endemic dental fluorosis &
dental caries emerged with survey of four
Illinois cities.
Galesburg & Monmouth[1.8 &1.7 ppm resp]
and Macomb & Quincy [0.2ppm]
34. Dean’s 21 cities study—primary basis for
choice of 1.0mg F/L—optimum concn for
Fluoridation.
35. 1941 Robert weaver– Gr Britain– a natural Fl
Area discovered- WWII.
Childr– Lake Dist from south shields—river
tyne– remarkably good teeth—than local
childr.
Impr obsv– finding – attention on the
deciduous dentition as well as permanent
teeth
36. Dental caries prevalence in
artificially Fl areas
Grand Rapids –Muskegon study
Lake Michigan area
1944-1959 :- Francis Arnold, Phillip Jay & John
Knutson
Michigan state health dept & Univ of Michigan
dental school.
First crucial step –caries reduction from12.48 to 6.22
DMF
Indicating natural obsv of inverse r/t of water Fl &
dental caries –cause & effect r/tship.
37. July 1951, Muskegon—Fl drinking water—
no longer control.
Grands Rapids –retrospective comparison
with base line data.
39. Evanston – Oak park study
[1946-1960]
3rd American Fl experiment– 14 yr study.
Drs. Blayney JR, Hill IN, Zimmerman SO –
university of Chicago memorial dental
clinic.
Evanston childr—43% reduction[5.95
to1.66 DMF]
Oak park childr — no change obsv.
40. Presented most detailed data of all the
fluoridation studies
Experimental proof –caries inhibitory prop
of Fl at 1 ppm in drinking water.
41. Canadian study
1951 Hutton & 1965 Brown and Paplove.
• Brantford, Ontario—Fl added
• Sarnia community—control town
• Stratford community-naturally 1.3 ppm Fl
17 yrs later Brantford similar caries
experience as Stratford.
55% lower than in control town of Sarnia.
42. Fl inhibits smooth surface caries
Dutch study [Tiel-Culemborg]
Backers Dirks 1961—11-15 yrs old
children.
• Tiel –Fluoridated—1.1 ppm
• Culemborg --- 0.10ppm control
43. • Designed to assess the prev effect of Fl
drinking water on anatomical sitting of
caries attack.
• approximal, free surface [buccal & lingual],
pit & fissure areas
• 13 yr study—88% reduction in smooth
surface caries & 43% in P&F caries.
44. New Zealand study
1965, Ludwig– Hastings,NZ: effectiveness
of Fluoridation.
Retrospective study
Baseline examtn 1954----later 1964
reexamined.
DMF of 10yr old
• 5.48 –1954
• 2.46—1964
• Reduction of 55%
46. 1969, WHO– recommends Ist time 1ppm Fl
in drinking water for practicable and
effective public health measure
47. Critical review
21 cities study:-
0.2-1.3mg F/L– in 9 cities of 21
Caries experience drops sharply towards
1.0-1.2mg/L & then tends to level out.
“questionable” category –usually separated
-not taken into account—should be
considered as Fluorosis—mildest form.
48. Pioneering Fluoridation studies
Grand-Rapids- Muskegon study-1945
Newburgh—Kingston study 1945
Evanston- Oak park study –1946
Canadian study—1946
• Also found fluorosis occurrence to same
extent as Dean in areas of natural
fluoridation
49. With time –it became common to quote -
prevalence data of very mild fluorosis -
lower boundary.
Time of Fluoridation policy in US- ?able
category –disregarded
50yrs after 21 cities study—1.0mg F/L
“optimal” concn for fluoridation
50. On application of present day standards of
field trails– all 4 studies –crude
• None are longitudinal—all used a sequential
cross- sectional design
• Sampling methods & dental examiners –
vary from one year to next.—risking bias &
random errors.
51. Potential confounders—socioeconomic diffr
not considered.
Data from control comm. –not used in
Grand Rapids & Evanston to compute the
extent of caries redtn
Conclusion based on weaker before- after
analysis.
52. Tiel- Culemborg study-1961
Only true longitudinal study of fluoridation
effects.
1988, 15 yrs after Fluoridation ceased in
Tiel, Culemborg’s caries experience was
lower than Tiel’s, even though DMF scores
in Tiel that year were lower than they were
when fluoridation was still operating in
1968
59. Fluorine is an element of many mosts: It is the most
reactive of all of the elements, the most powerful oxidizing
agent, and the most electronegative. But its true strength
and the secret of its success lies in the compounds it forms-
-some of the most stable and inert substances known to
man. These compounds have enabled a steady stream of
scientific and commercial advances: Staying warm and dry
in a downpour, cooking with the ease of a nonstick pan,
and beaming a "cavity free" smile are all available thanks
to the fluorine atom.
