Preventive Dentistry

( Prevention of dental caries )

There are 2 ways to prevent dental caries:

1) Chemical methods for e.g. : a) Fluoride.b) Pit & fissure sealant.c) Chemical mouth rinse.d) Diet & nutrition.e) Antimicrobial agent.

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Fluoride and dental caries

Fluoride is highly reactive it forms salts of almost all metals, it is rarely occurs as free ions in nature.Fluoride is widely distributed in the atmosphere originating from:- Dusts of fluoride containing soils.- Gaseous industrial wastes.- Gases emitted in areas of volcanic activity.

The concentration of fluoride in vegetation is range from 2 part per million (ppm) to 20 ppm dry weight. This depends on species of the plant, age of leafs, soils, fertilizers and pollution. Fluoride returns to soils through plant wastes or it may enter the food chain and be returned as animals waste. Fluoride may enter the environment indirectly by industrial air pollutions as coal burning, production of aluminum steel, phosphate fertilizers, manufacture of glass etc. In biological tissues fluoride is present in traces, thus called a trace element.

Sources of fluoride intake in Man: 1- Water: The greater part of F intake originates from water ingested each day. Fluoride is naturally present in rivers, oceans and ground water. The concentration may range from 0.1 – 10 ppm. 2- Food: It may present in various concentration in soft drinks, different infants and adult food. Fluoride concentration in various foods reflects its concentration in water where the product has been prepared.

2) Mechanical methods for e.g. :a) Mouth wash.b) Teeth brushing, dental floss, tooth picks.c) Chewing gum ( sugar free ).d) Scaling &polishing.

For infants the daily fluoride intake is determined by feeding pattern, as breast milk or formula milk. In human breast milk F concentration is 6 -12 mg/ml this is in fluoridated and non fluoridated area. In cow's milk the concentration is less than 0.019 ppm. In formula milk and cereals the concentration depends on the product and on F concentration in water these are prepared. For adults food F concentrations vary, but usually less than 0.5 ppm. A higher concentration may be found in tea (0.5 – 4ppm) and in fish and shell fish. 3- Drugs and dental products: Some drugs contain a high concentration of F as diuretics and anesthetics. Dental products as dentifrices and mouth rinses.

4- Pollutions: F is present in high concentration in the vicinity of metal industries, about 25 – 1000 times the normal.

Fluoride Metabolism: 1- Absorption:

After intake of F it will be absorbed in the gastro intestinal tract, it is also absorbed via lungs. There are factors affecting the rate of F absorption, these are:

- Solubility and degree of ionizations of the components. This will determine the amounts of F ions released. Only F in ionic form is of importance to health. NaF is more soluble than CaF2 thus the rate and degree of absorption of NaF is more than CaF2.

- Dose and F concentration. Following absorption there will be an elevation in plasma F level. The height of plasma peak is proportional to F dose ingested and rate and degree of absorption in addition to body weight (with increase body weight there will be a lower plasma peak).

- Presence of food in the stomach. Presence of certain dietary items as Ca may lead to formation of insoluble salts with F. Food acts as a physical barrier that retards absorption of F from GIT.

- Gastric acidity. There is an inverse relation between gastric acidity and absorption of F from GIT.

Ingestion of F is

- Empty stomach ………………100%

- In presence of glass of milk…… 70%

- Ca- rich breakfast ………… 60%

Milk may retard absorption of F from the stomach in the first hour, later absorption will continue at higher levels for longer period of time.

2- Retention and distribution in the body:

The maximum plasma concentration of F is reached in 30 minutes. The plasma peak will be reduced as F distributed in the body. Fluoride is a calcified tissue seeker, more than 99% of F in the body is found in calcified tissues. F is rapidly distributed to bone, teeth, heart, kidney and liver. While, fluoride is slowly distributed to skeletal muscles and adipose tissues.

The up take of F is affected by age factor, younger the age the greater will be the up take of F. Not all F in bone is firmly held as some of F is subsequently lost again by the osteoclastic resorption of bone.

3- Excretion:

The major route of excretion is by kidneys. After entering the renal tubules some of F ions will be re absorbed and return to the circulatory system, while the remainder of ions will be excreted by the urine. The renal clearance of F is 50 ml/minute. About 10% of F is removed by feces this amount is never absorbed, also a less quantity is excreted by sweat, saliva and gingival exudates, tears.

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Theories of caries reduction by fluoride :

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(OH)2 + 2 F- Ca10(PO4)6 F2 + 2 OH-

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 re mineralization. Two types of reactions 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(OH)2 + 20 F- CaF2 + 6PO43- + 2OH-

Ca10 (PO4)6(OH)2 + 2 F- Ca10 (PO4)6 F2 + 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.

- Inhibition of intercellular enzymes as enolase and phosphotase.

- In a high concentration, F is toxic to bacteria.

The general mechanisms where by fluoride reduces dental caries involve the followings:

1- Increase enamel resistance or reduction in enamel solubility.

Caries process involves dissolutions of enamel by acids from bacterial plaque. This dissolution is inhibited by the presence of fluoride. When enamel is exposed to acid (pH less than 5.5) it will dissolve to its ionic form (Ca, HPO4, OH), this occurs beneath a bacterial plaque. The concentrations of calcium, phosphate and other ions in the solution will increase. When plaque stop producing acid, the pH will raise and the dissolved minerals get precipitated in the outer enamel surface. Thus the carious process is a cyclic phenomenon

consisting of phases of de mineralization and re precipitation. The presence of fluoride reduces the solubility of enamel by promoting the precipitations in form of fluoroapatite crystals and calcium fluoride.

Ca10(PO4)6 (OH)2 + 2 F- Ca10(PO4)6 F2 + 2 OH

Ca10 (PO4)6 (OH)2 + 20 F- 10CaF2 + 6PO43- + 2OH-

2- Re mineralization of incipient lesion.

By depositions of minerals into previously damaged areas, this will also lead to reduce solubility. Fluoride enhances the re mineralizing process by accelerating the growth of enamel crystals that have been de mineralized by caries process.

3- Interference with plaque microorganism.

In high concentration fluoride is bactericidal, thus reduces plaque. In relatively low concentration, fluoride is bacteriostatic, affecting growth of bacteria.

4- Improved tooth morphology.

Ingestion of fluoride during the period of tooth formation, lead to changes in tooth morphology, as smaller cusps depth of teeth turn the more self-cleansing.

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Fluoride toxicity :There are two types of toxicity related to fluoride:

1- Acute fluoride toxicity due to single ingestion of a large dose of fluoride at one time.

2- Chronic fluoride toxicity due to long term ingestion of small amount of fluoride for a long time.

Acute fluoride toxicity;

It is the rapid excessive ingestion of fluoride at one time, the speed and severity of ingestion depend on amount of fluoride ingested and the weight and age of the victim.

It is always recommended not to dispense more than 264 mg of F at any time.

Signs and symptoms of acute toxicity:

GIT; nausea, vomiting, diarrhea, abdominal pain, and cramps.

CNS, paresthesia, tetany, CNS depression and coma.

CVS; weak pulse, hypotension, pallor, shock, cardiac irregularities and ultimately failure.

Blood chemistry; acidosis, hypocalcaemia, hypomagnesaemia.

Emergency treatment depends on the dose ingested:

1- Less than 5 mg/kg body wt. :

- give calcium orally or milk to relive gastro intestinal symptoms.

- Induce vomiting if necessary

- Keep child under observations.

2- More than 5 mg F/ kg body wt. :

- Empty stomach by induction of vomiting using emetic materials.

- If vomiting is not possible as for infant or young child or retarded patient then endotracheal intubation is performed before gastric lavage.

- Give solution as milk or Ca- gluconate 5% or Ca – lactate solution.

- Admit to hospital.

3- More than 15 mg / kg.

- Admit to hospital immediately.

- Cardiac monitoring

- IV administration of 10 ml of 10% Ca gluconate solutions.

- Monitoring of electrolyte especially Ca and K.

- Adequate urine out put by diuretic.

- Supportive measures for shock.

Recommendations to avoid toxicity

1- use small amount of topical fluoride agents in the clinic (not more than 4 ml).

2- Self applied fluoride for children need to be observed by parents.

3- Keep F supplements out of the reach of children.

Chronic fluoride toxicity

It is long term ingestion of small amount of F for years, in teeth is dental fluorosis and in bone is skeletal fluorosis.

Skeletal fluorosis is a term used to describe any changes in bone because of ingestion of at least 8 ppm of fluoride for years.

Signs:

- More dense bone.

- Diffuse bone.

- Thickening of cortical bone.

- Numerous exostoses. Through out the skeleton.

- Calcification of ligaments and tendon

- Crippling fluorosis in severe cases.

The severity of these signs depends on the duration and concentration of F ingested and age of the individual. This condition is seen in polluted area due to industrial factories or volcanic actions.