The role of The role of fluoride in caries fluoride in caries

prevention, prevention, toxicologic toxicologic

aspectsaspects12th lecture12th lecture

Goals of Fluoride (F) Goals of Fluoride (F) AdministrationAdministration

• 1) Do not harm the patient. • 2) Prevent decay on intact dental

surfaces. • 3) Arrest active decay. • 4) Remineralize decalcified tooth

surfaces.

GOALS OF FLUORIDE (F) ADMINISTRATION

Do not harm

Prevent decay on intact dental surfaces

FF

FF

Arrest active decay

Remineralize decalcified teeth

1.

2.

3.

4.

FF

Fluorosis or toxicity

The Basics of Fluoride The Basics of Fluoride PreventionPrevention

Ca10[PO4]6 [OH ]2+F- = Ca5[PO4]3 F Ca5[PO4]3 OH +OH-

equation

Hydroxyapatite (HAP) Fluorhydroxyapatite (FHA)

OH

PO4

Ca

Ca

Ca

Ca

Ca Ca

PO4

PO4

PO4PO4

OH

PO4

Ca

Ca

Ca

Ca

Ca Ca

PO4

PO4

PO4PO4

OHF-

F-

Hydroxyapatite (HAP) Fluorhydroxyapatite (FHA)

If more fluorid ingested during enamel formation:

Ca10[PO4]3 [OH ]2+20F- = 10CaF2 + PO43- + OH-

With the breakdown of HAP crystals calciumfluoride is formed.Clinical appearance: White - Brown spots on teeth.

Fluorosis

Fluorosis, regardless of severity, cannot occur once enamel formation is complete and the teeth have erupted. Therefore older children and adults are not at risk for dental fluorosis.

Benefits of fluorideBenefits of fluoride• Increased resistency against acides• Compact cristall-net• Pre-eruptive effect: different shape

(shallow fissures and smaller cusps)• Post-eruptive effect: remineralisation,

inhibition of sugar-digesting enzymes, inhibition of polysaccaride-synthesis in high cc, inhibition of protein (bact) absorption to enamel surfaces, inhibition of regeneration and colonisation of cariogen bacteria.

General effectsGeneral effects• Inhibition of arteriosclerosis• Inhibition of osteoporosis

Toxicity of swallowed TPToxicity of swallowed TP

• STD (safely tolerated dose) – 1-3 mg /bwkg

• PLD (potentially lethal dose) – 5mg /tskg– PTD (potentially toxic dose)

• CLD (certainly lethal dose) – 32-64 mg/tskg

Probable toxic dose (PTD): The PTD is 5 mg F/kg body weight.

For a 20 kg 5 to 6 year old this would be 100 mg and 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 mouthrinse contains 91 or 97mg F and a tube of fluoridated toothpaste contains as much as 230mg F.

TEXT

POTENTIAL HARM

5 mg F / kg body 5 mg F / kg body weightweight

20 kg 6 year old, PTD= 100 mg F100 mg F

10 kg 2 year old PTD = 50 mg F50 mg F

230 mg230 mg F/ tube toothpaste

ACT91-97 mg91-97 mg F/ container of F mouthrinse

Symptoms:Symptoms:

1.1. VomitingVomiting

2.2. Excess salivary Excess salivary and mucous and mucous dischargedischarge

3.3. Cold wet skinCold wet skin

4.4. Convulsion at Convulsion at higher dosehigher dose

Probable toxic dose:

Topical F, 12,300 ppm F pH= 3.5

61.5 61.5 mgmg F/ 5 ml

FF

CaCa

FF

CaCa

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.

FF CaCa

FF

CaCa

FF CaCaFFCaCa

FFCaCa

FFCaCa

A serious systemic consequence is binding of F to Ca which needed for heart function.

POTENTIAL HARM

FF CaCaFFCaCa

FFCaCa

FFCaCa

ToxicityToxicitySub-lethal toxic symptoms are manifested quickly

after the dose and consists of vomiting, excessive salivation, tearing and mucous discharge, cold wet skin and convulsions with higher doses.

Counter measures which should be administered immediately are emetics, 1% calcium chloride, calcium gluconate or milk.

(Calcium reacts with F in the GI tract and prevents its absorption. The most serious consequences of F toxicity stem from reactions of cationic electrolytes with systemic F.)

ToxicityToxicity• Chemical burn: concentrated F

contaminated with skin, creates HF acid

• Protoplasma toxicity: inhibition of enzyme-systems

• Binding Ca: inhibitors of muscle function

• Hyperkalaemia (extra high potassium level): cardiotoxicity

Chronic toxicityChronic toxicity

• Sceletal fluorosis• -osteosclerosis• -calcification of tendons• -multiplex exostosis

Chronic toxicityChronic toxicity

•The fluorosis

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.

Remember that all forms of F intake comprise the daily consumption. This includes water intake (up to 1.5mg/day), foods (0.3 to 1.0mg) and especially significant in young children, 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.

TEXT

FLUOROSIS

FF

FF

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

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 toothpastefluids 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 F

1.2 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 recommended for fluorosis susceptible children.

moderate

severe

mild

pitting

Mild fluorosisMild fluorosis

Moderate fluorosisModerate fluorosis

Severe, pitted fluorosisSevere, pitted fluorosis