Dental Structure and Fluoridation

Dr. Iyad ABOU RABII

DDS. OMFS. MRes. PhD

Dental Structure

Dental structure (Enamel)

The enamel is the most highly mineralized tissue in the

body consisting of

95% hydroxyapatite (HAP)

4.5% water

0.5% organic matrix.

Enamel is the visibl white part of the crown.

It contains calcium phosphate, fluorine, protein and water.

Thanks to this combination, the enamel optimally protects the interior of each tooth from temperature differences, bacteria and acids, as well as from the pressure required to chew food.

Dental structure (Enamel)

Mineralization

• It is the change of physical stat of a substance from liquid and semi-liquid status to solid status through deposition of minerals (calcium and phosphate) .

Mineralization

Localization of

mineral within

the collagen

fibril.

Mineralization

Hydroxy Apatite (HA) and fibrillo-carbonato-apatite

Hydroxyapatite CrystalsSamson

Chemical formula is Ca10 (Po4). X2

Hydroxyapatite Crystal has one longitudinal axis C and three transversal axis a1, a2, a3

the two axis a1,a2 are perpendicular with the axis C with an angle of 120 between theses two axiss

Enamel rod Structure

Enamel.

A, Its rod structure as seen in ground sections with the

light microscope.

B, Electron micrography shows that enamel consists of a

mass of crystallites organized into rod and interrod

enamel.

Enamel rod Structure

Fluoridation

A. Goals of fluoride administration

B. Non-professional fluoride administration

1. Systemic

2. Topical gels

3. Rinses

4. Dentifrice

C. Professional administration

1. Topical

2. Varnish

Contents

GOALS OF FLUORIDE (F) ADMINISTRATION

Do no harm

Prevent decay on in tact dental

surfaces

F

F

Arrest active decay

Remineralize decalcified teeth

1.

2.

3.

4.

F

Fluorosis or

toxicity

Do not harm the patient

Probable toxic dose (PTD):

• PTD is 5 mg F/kg body weight.

For a 20 kg 5 to 6 year old this would be 100 mg

for a 10 kg 2 year old, 50 mg.

F content of dental products or treatments may exceed these values for

young children. For example,

a gel tray containing 5 ml of APF contains 61.5mg F (F is absorbed

more quickly when in acidic form.),

100ml of 0.2 or 0.4% F mouth rinse contains 91 or 97mg F and a

tube of fluoridated toothpaste contains as much as 230mg F.

1.

TEXT

POTENTIAL HARM

5 mg F / kg body

weight

20 kg 6 year old,

PTD= 100 mg F

10 kg 2 year old

PTD = 50 mg F

230 mg F/

tube

toothpaste

ACT91-97 mg F/

container of F

mouthrinse

Symptoms:

1. Vomiting

2. Excess salivary and

mucous discharge

3. Cold wet skin

4. Convulsion at

higher dose

Probable toxic dose:

Topical F,

12,300 ppm F

pH= 3.5

61.5

mg F/

5 ml

Do not harm the patient

Probable toxic dose (PTD):

Sub-lethal toxic symptoms are manifested quickly after the dose and

consists of

1. vomiting

2. excessive salivation

3. tearing

4. mucous discharge,

5. cold wet skin

6. convulsions

1.

TEXT

F

Ca

F

Ca

Counter Measures:

1. Emetics

2. 1% calcium

chloride

3. Calcium gluconate

4. milk

Divalent cations

like Ca cause

precipitation, of F

and prevent

absorbtion in the

intestine.

F Ca

F

Ca

F Ca

FCa

FCa

FCa

A serious systemic

consequence is binding of F

to Ca which needed for

heart function.

POTENTIAL HARM

F Ca

FCa

FCa

FCa

Fluorosis:

Fluorosis occurs when teeth are developing.

The most critical ages are from 0 to 6 years. After 8 years, risk of

fluorosis is essentially past.

During the critical ages F intake in excess of 0.1mg/kg body

weight/day can lead to fluorosis.

This is roughly 1mg/day for a 1 to 2 year old or 1.5 to 2 mg for a 5

year old.

Do Not Harm the Patient

2.

TEXT

10

9

8

7

6

5

4

3

2

FLUOROSIS

0.0 0.5 1.0 2.0 3.0 4.0

DMFT

PPM F IN DRINKING WATER

slight

severe

moderate

mild

F in excess of 0.1mg/ kg body

weight = fluorosis

POTENTIAL HARM

FLUOROSIS

F

F

Excess F affects

mineralization of

developing teeth

Up to age 6 is the critical age for fluorosis.

After age 8, risk is past.

Enamel prism

Fluorosis:

Remember that all forms of F intake comprise the daily

consumption.

This includes

1. water intake (up to 1.5mg/day)

2. Foods (0.3 to 1.0mg) and especially significant in young

children

3. Swallowed toothpaste. Children under 2 years swallow 50% of

toothpaste during tooth brushing and at 5years, 25%, both of

which may amount to 1mg F/day.

Do Not Harm the Patient

2.

TEXT

FLUOROSIS

F in excess of 0.1mg/ kg body

weight = fluorosis

Maxium safe dose

for a 5 year old = 2

mg F / day

Maxium safe dose

for a 2 year old = 1

mg F / day 1 2 3 4 mg F

supplements toothpaste

fluids food

DW Banting

JADA

123:86,1991

Daily F intake of a 20 kg 4

year olds with different water F

0.5

ppm

water F1.2

ppm

water F

FLUOROSIS

Children under 2 years

swallow 50% of

toothpaste

5 year olds swallow 25%

of toothpaste

Toothpaste = 1 mg F /

gram (1000 ppmF)

1 to 3 grams

“pea” size amount (0.5g) is

recommenred for fluorosis

susceptible children.

moderate

severe

mild

pitting

Prevention of Caries: 1st theory

1st theory :Deposition of fluorapatite (FHA) in sound tooth structure:

•Caries protection results from FHA being more acid resistant than

pure hydroxyapatite (HA).

•Deposition takes place when F replaces hydroxyl groups in HA.

•This can occur pre- or post-eruption at neutral pH, or post-

eruptively at neutral or acidic pH. At low pH, HA dissolves, then

re-precipitates as new crystals which are larger and more acid-

resistant due to higher FHA and lower magnesium and carbonate

content.

Prevention of Caries: 1st theory

Deposition of fluorapatite (FHA) in sound tooth structure:

Deposition of FHA is accomplished both by

1. systemic intake of F during tooth development

2. topical F administration after eruption. Professional topical F

treatments with concentrated acidulated phosphate fluoride (APF)

gels (2.72% APF gel contains 12,300 ppm F), is the most efficient

way to accomplish this, especially when applied to newly erupted

teeth (i.e., age 2 for primary molars; age 6 to 8 for permanent first

molars and anterior teeth; age 11 to 14 for permanent premolars and

second molars).

MECHANISMS OF F PROTECTION

F F F F F F

F F F F F

F

Saliva (S)

Plaque (P)

Tooth (T)

DEPOSITION

Increase FHA

levels maximally in intact

dental surfaces.

Theory:

Topical F is

the best

method for

deposition.

F

F

F

F

F

FF

FCa

PO4

PO4

Ca

Neutral pH

remineralization

DEPOSITION OF F

F

F

FHA

FHA

FHA

HA

pH 5.0

Ca

P

FHA is more acid resistant than HA

H+

H+

CO3

Mg

H+

H+

Mg and CO3

do not

reprecipitate

F

F

F

F

This has better F uptake due to

more porosity

DEPOSITION OF FBest F uptake is late pre-eruption

and early post-eruption

F

F

F

FF

FFF

F

F

F

F

Mature

enamel

Surface

build-up of

F

F

F

F

Ename

l fluid

Young enamel

Drinking

water

Permanent

teeth

Primary

teeth

F 3000 900

No F 2000 600

Maximal F levels of in outer 5 microns

3000

2000

1000

PPM Fluoride

outer 2 microns = 6000 ppm

fluoride (max. uptake)

Fluoride uptake is higher in a decalcified

area

F

5 um

DEPOSITION OF F

CaCa CaCaCaF F

F

As fluoride reacts strongly with calcium it

does not penetrate far into the tooth.

3000 ppm F

1500 ppm F

FDEPOSITION OF F:

Maxium uptake can

not be exceeded.

(3000 to 4000 ppm F

in outer 5 um)

The F-rich surface can be abraded

away.

Bioavailability of F: A second theory of caries prevention asserts that

F in the vicinity of carious activity (in enamel fluid) prevents

dissolution of HA crystals. Although this mechanism requires only

low levels of F (less than 100ppm to as low as 1ppm), F must be

present when the acid challenge takes place and therefore must be

supplied continually.

Examples of topical applications which ensure bioavailability are

fluoridated drinking water and fluoridated dentifrices. A major source

of bioavailable F is residual F in plaque and pellicle. F in plaque

minerals such as CaF2 or calculus or in protein complexes is released

during bacterial acid production.

Prevention of Caries

BIOAVAILABILITY

F

F

S

P

T F

ACID

SUGAR

Provide continual low level of F to

enamel fluid. The benefit occurs at

the time of decalcification.

Theory:

MECHANISMS OF F PROTECTION

Water fluoridation

is an example of a

source.

BIOAVAILABILITY OF F

SUGAR

Low level of F F

S

H+

H+

H+

H+

F

F

F

F

SS

saliva

Plaque and

enamel fluid

plaque

Intact HA

crystals

H+

FDecalcifying HA

crystals

J Arends. JDR

69(SI):601,199

0

Decalcification of enamel crystals:

F Stable FHA

F Loosely bound or

adsorbed F

F

F

F

F

FF F

F

F

F

FFACID

Protection from

dissolution

F from plaque

fluid

H+

H+

BIOAVAILABILITY OF F

F

F

Loosely-bound F

will eventually

become stable

FHA.

J Arends. JDR

69(SI):601,199

0

F

F

F F

F

F

F

F

Protection only

where is

F

H+

H+

H+

H+

H+

BIOAVAILABILITY OF F

F

Ca

PO4

PO4

Ca

FHA with no

Incomplete protection

F

H+

H+

H+

H+

H+

F

J Arends. JDR

69(SI):601,199

0

BIOAVAILABILITY OF F

F

F

F

H+

H+MS

Effect on bacteria:

H+

H+

F

F

F

F

SSH+

F

H+

H+

The presence of

fluoride at the time of

glycolytic activity will also

inhibit of plaque

acidogenesis.

SOURCES OF BIOAVAILABLE F

1. saliva

0.08

0.02

ppm F in saliva

after drinking

1 3 5 h

F F F F

S

P

T

4. RESIDUAL

F

AC

T2. Fluoridated

water 3. Home care products

Calcium

Fluoride

F F F F F

Topical F

CaF2 precipitates in

plaque during topical

F treatment

FHA

No FHA

No FHA

F F

10 ppm F

added to

drinking water

LESIONS (mean)

MS

8

30

5

DEPOSITION

BIOAVAILABILITY

Larson RH. Caries

Res 10:321, 1976

sugar

BIOAVAILABILITY VERSUS DEPOSITION OF F

Rodent studies:

plus

0

1

2

3

4

5

0.05 0.1 1 5

calcium loss

F ppm in solution

pH

BIOAVAILABILITY OF F

pH 5.0

HA

calcium

phosphate

JM Ten Cate. JDR

69(SI):614,1990

Research evidence:

F

F

Add F:

Summary of preventive F procedures and recommendations:

The older view of caries prevention was that FHA deposition in non-carious

dental surfaces should be maximized by systemic F administration during

tooth development, and post-eruptively by topical F treatments.

It was believed that increased FHA provided increased protection against

caries.

Although implementation of high FHA deposition has proved beneficial, it

does not afford as much protection as bioavailable F. Moreover, the high

doses of F required, systemically or topically (which often becomes

systemic intake) are partly responsible for the increasing incidence of

fluorosis.

Prevention of Caries

Summary of preventive F procedures and recommendations:

Current clinical recommendations for preventive F measures are

1) to determine total F intake per day from all sources in order to assess

over or under F exposure

2) determine caries risk

3) institute a regimen commensurate with individual caries risk status which

emphasizes bioavailability of post-eruptive topical F (e.g. regular use of F

dentifrice and other home products if indicated)

4) administer professional topical F treatments, the timing of which should

also be gauged to caries risk (This may not be needed in low risk

individuals) and

5) administer systemic topical F if indicated. (The latter is currently under

review. Present Academy of Pediatric Dentistry recommendations are

presented below.

Prevention of Caries

FLUORIDE SUPPLEMENTS

AGE <0.3ppm 0.3-

0.6ppm

>0.6ppm

6m-3y 0.25 0 0

3-6y 0.5 0.25 0

6-16y 1.0 0.5 0

F in drinking water

F

Academy of Pediatric Dentistry current

recommendations

1. Determine F intake

2. Determine caries risk

3. Devise personalized plan based on risk

level.

4. Stress bioavailability of F.

5. Monitor F intake of young patients in

an effort to prevent fluorosis.

SUMMARY OF PREVENTIVE F

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