Preventive Dentistry (Lecture 9) Other caries preventive factors Fluoride I Dr. Caroline Mohamed
Outline of lectures OTHER CARIES-PREVENTIVE FACTORS Fluorides Occurrence and intake Toxicology Pre-eruptive effect of fluoride on tooth formation Post-eruptive effects of fluoride Arrest of caries Remineralization
FLUORIDES • Fluorides have unique external modifying effects on caries initiation and progression. However, a prerequisite for optimal effect is a combination of excellent mechanical and chemical plaque control, targeting the cause of dental caries-the cariogenic plaque.
We should use fluoride in populations and individuals with: • a high prevalence of caries, • poor standards of oral hygiene, and • no exposure to fluoride, a restriction in frequency of intake of sticky, sugar-containing products would result in some decrease in caries incidence. • Salivary stimulation is an important caries-preventive measure in caries-susceptible patients who have a reduced salivary flow.
Occurrence and intake • Halogen • Compound form of fluorine. • A trace element- computer analyses. • Very reactive gas. • Not found in free elemental form in nature. • Major source is from water – artesian wells. • Found in soils rich in fluorspar, cryolite, and other minerals. • In biologic materials, the concentration of fluoride is generally as low as a few parts per million or less.
Soil..( 0.05 to 190 mg/m3) • Food… ( 0.2 to 1 ppm or more ) • Drugs • Fertilizers ..( ..42.000 mg/kg) • The most important fluoride-containing minerals are fluorspar CaF2, and fluorapatite which are widespread in many countries.
Normally the fluoride concentration in groundwater is limited to 0.2 to 2.0 ppm, but, for example in the United States, India and some African countries, fluoride concentrations greater than 60.0 ppm have been reported.
By contrast, most surface water contain less than 0.1 ppm of fluoride. In rivers, it may range from 0.1 to 1.0 ppm of fluoride. Seawater contains 1.2 to 1.4 ppm of fluoride. Concentrations may be altered locally by undersea volcanic activity. Most fluoride in water exists as free fluoride ions. D Caroline Mohamed
Dietary sources - drinking water • Waterborne fluorides are the most important source of flouride for humans. • Modern diets as a source of flouride. • Use of fluoridated water in preparation of processed foods and beverages. Hallo effect. • For temperate climates • Optimal fluoride level: 1 ppm of fluoride. D Caroline Mohamed
Dietary sources - foods • Fluoride in foods. • Nonfluoridated communities: 1 mg/day. • Fluoridated communities: 2 – 3 mg/day. • Not known to be a significant factor in fluorosis (mottled enamel). • Small amounts: fruits, vegetables, cereals. • Rich amounts: seafoods and tea leaves. D Caroline Mohamed
Dietary sources - drinking water • For infants and young children • Intake of 2 – 4 glasses of water: 0.5 – 1 mg of fluoride. • For older children, adolescents and adults • Intake of 6 – 8 glasses of water: 1.5 – 2 mg of fluoride. • Ingestion of fluoride greater than optimal levels in drinking water (2 ppm) may cause fluorosis. D Caroline Mohamed
Dietary sources - foods D Caroline Mohamed
Tea leaves are a particularly rich source of fluoride, most of which is rapidly released into tea infusions, within 5 to 10 minutes. • The fluoride concentrations of brewed tea commonly range from 0.5 to 4.0 ppm.
Fluoride intake from diet (including drinking water and beverages with less than 6.0 mg of F/L) and recommended use of fluoride-containing dental products such as toothpastes, mouthrinses, lozenges, and chewing gums will normally have no adverse effect on general health in young adults and adults. • However, up to the age of 6 years, it is well known that a high intake of fluoride will result in visible fluorosis of the teeth.
Early use of fluoride tooth paste • Young children in whom the swallowing reflex is not fully developed can ingest up to 0.3 –o,5mg F at each brushing. • The risk is not as high as fluoride supplement
Infant formula: Because its own F content and especially because it is mixed with fluoridated water. • Other factors that have been associated with susceptibility of populations to dental fluorosis are altitude, renal insufficiency, and possibly malnutrition.
Metabolism - absorption • Major site of absorption: stomach. • Studies with animals suggest intestinal absorption also occurs. • Soluble fluoride in drinking water is 100% completely absorbed, whereas 50 – 80% of the fluoride in foods is absorbed. • Oral mucosa can absorb fluoride in small quantities. D Caroline Mohamed
Metabolism - Distribution • Teeth and skeleton have the highest concentrations of fluoride. • Due to the affinity of fluoride to calcium. • Cementum, bone, dentin, and enamel. • Fluoride content of teeth increases rapidly during early mineralization periods and continues to increase with age, but at a slower rate. D Caroline Mohamed
Metabolism - Excretion • Principal route of excretion is urine (90 – 95%). • Remaining 5 – 10% in the feces. D Caroline Mohamed
Metabolism - Excretion • Directly related to the degree of active bone growth. • Fluoride excretion is lower when a child is growing rapidly and is actively depositing bone material than in adultswith a mature bone structure and fully mineralized teeth. • About half of the ingested fluoride is excreted in the urine each day. D Caroline Mohamed
Metabolism - storage • Deposited in calcified structures. • Skeletons of older persons contain more fluoride than those of younger ones. • Amount of fluoride in bone gradually increases with age • Greatest during active growth years. D Caroline Mohamed
Metabolism - storage • Factors that attract fluoride to bones: • Presence of an active growth area at the ends of long bones. • Small size of the bone crystals. • Close contact between bones and the blood supply D Caroline Mohamed
Metabolism - storage • Deposited in the enamel through diffusion. • Carious enamel may take up 10 times more fluoride than adjacent healthy enamel to inhibit expansion of carious lesion. • Dentin may contain even more fluoride. • Chemically similar to bone • Highest concentration found adjacent to pulp: close to blood supply. D Caroline Mohamed
Relative safety • Low and moderate intake results to ( related to general health and age ): • Skeletal fluorosis • Mottled enamel • Osteosclerosis (hardening of bone) • Exostoses (bony projections) ( linked to impaired renal function) • Calcification of ligaments • High intake may result to death. D Caroline Mohamed
The intake of fluoride associated with the development of enamel fluorosis of the permanent teeth has been estimated to range from 40 to 100 μg/kg of body weight per day. • Infants consuming formulas made from concentrated liquids, or powders diluted with water providing 1,000 μg of fluoride/L, are at risk of dental fluorosis (1000 µg/L=1 mg/L). • The fluoride-concentration will increase when water is boiled in Teflon-coated vessels.
The maturation phase of the maxillary incisors occurs at 22 to 26 months of age ( around 2 years of age), when susceptibility to fluorosis is greatest. • For the incisors, fluoride exposure prior to this period ( < 2 years of age ) carries less risk than exposure for up to 36 months( around 5 years age ) subsequently; a period corresponding to the maturation phase of the incisors (approximately 2-3 years old). • The clinical implications are the central and lateral incisors are susceptible to fluorosis as a result of excessive fluoride intake up to age 5 years, with peak susceptibility at around the age of 2 years.
To prevent the development of visible and esthetically disturbing fluorosis, fluoride intake in infants and preschool children should therefore be limited and controlled.
Permanent Teeth Calcification Begins (Months) Eruption (Years) Maxilla Central incisor 3-4 7-8 Lateral incisor 10- 12 8-9 Canine 4-5 11-12 First premolar 8-21 10-11 Second premolar 24-27 10-12 First molar 0-1 5-6 Second molar 30-36 12-13
The risk for and severity of fluorosis are closely correlated with the plasma fluoride level during enamel maturation. • The later in life enamel mineralization occurs, the more severe the enamel fluorosis is likely to be, even assuming a constant dose of fluoride from birth. • The pattern of fluorosis in the permanent dentition is strongly correlated to the time of maturation of the tooth enamel for the homologous pairs of teeth.
Mottled enamel Exostoses Skeletal fluorosis osteosclerosis D Caroline Mohamed
Mottled enamel (Endemic Dental Fluoride) • White or brown spotty staining of tooth enamel. • May be due to food, debris, or plaque. • Sometimes will have horizontal striations. • Enamel is deficient in: • Number of cells producing enamel causes pitting (hypoplasia). • Hypocalcification causes chalkiness. D Caroline Mohamed
Mottled enamel (Endemic Dental Fluoride) • Occurs only in teeth that are being formed. • The risk of developing fluorosis is strongly correlated to the regular intake of fluoride during tooth mineralization, particularly during the maturation phase of the enamel. • When exposed to high concentrations of fluoride, opaque spots will develop on the enamel. • High intake of fluoride results to mottled enamel. • Protection of fluoride is decreased by severe fluorosis. D Caroline Mohamed
Dean (1936) suggested classification of the dentition into one of seven categories, according to the degree of enamel changes (fluorosis), from 0 for normal enamel to 7 for severe fluorosis. Scores from 1 to 6 comprised the stages questionable, very mild, mild, moderate, and moderately severe. Later Dean (1942) combined moderately severe and severe into one score, namely severe to include all enamel surfaces with any type of surface destruction, irrespective of degree.
Mottled enamel (Endemic Dental Fluoride) D Caroline Mohamed
Toxicology • Topical fluoride agents are safe and harmless if used strictly as directed. • The probable toxic dose defined as the threshold dose that could cause serious or life threatening systemic signs and symptoms necessitating immediate emergency treatment and hospitalization, is 5 mg of F/kg of body weight. • Child death is likely to occur if a child ingests a fluoride dose in excess of 15 mg of F/kg of body weight. • A dose as low as 5 mg of F/kg body weight may be fatal for some children.
It is essential that the fluoride concentrations in dental products be known to the persons who use them. • It is even more important to know the amount of fluoride contained in standard packaging (bottles of tablets, tubes of toothpaste, etc) as well as the amounts involved during routine usage and how these amounts relate to the probable toxic dose.
Symptoms of acute toxicity • Fluoride toxicity is characterized by a variety of signs and symptoms. • Symptom onset usually occurs within minutesof exposure. • Severity of symptoms can depend on the amount of fluoride ingested/ age/weight/health condition of the patient. • Symtoms: Gastrointestinal Abdominal pain Diarrhea Dysphagia Hypersalivation Mucosal injury Nausea Vomiting Electrolyte abnormalities Hyperkalemia Hypocalcemia Hypoglycemia Hypomagnesemia
Cardiovascular Cardiac arrest Shock Various arrhythmias Neurological effects Headache Hyperactive reflexes Muscle weakness Muscular spasm Paresthesia Seizures Tetanic contractions Tremor
Method of action (fluoride toxicity) Ingested fluoride initially acts locally on the intestinal mucosa. It can form hydrofluoric acid in the stomach, which leads to gastrointestinal irritation or corrosion. After ingestion, the gastrointestinal tract is the earliest and most commonly affected organ system.
Treatment In case of accidental swallowing, give milk, calcium carbonate or milk of magnesia to slow absorption. D Caroline Mohamed
Mechanisms of anticaries action of fluoride • Increase in the enamel’s resistance to acid solubility • Enamel formed has more perfect and larger crystals, less soluble in acid, and less likely to develop caries. • Fluoride favors formation of fluorapatite, a more acid – resistant apatite than hydroxyapatite. D Caroline Mohamed
Mechanisms of anticaries action of fluoride • Remineralization • Greater concentration of fluoride released from the dissolved enamel or already present on the plaque,the more will remineralization be favored and carious process be slowed. • Use of topical fluoride raises the fluoride level of tooth surface and underlying tissues to a level expected to protect against caries. D Caroline Mohamed
Mechanisms of anticaries action of fluoride • Antibacterial effects of fluoride • Inhibition of enzymes essential to cell metabolism and growth. • Lower the surface energy of the tooth. • Can strip off bacteria from hydroxyapatite. • Fluoride can bind more effectively to positively charged areas on the apatite crystal than can the bacteria. D Caroline Mohamed
Systemic Theory of fluoride action • Pre-eruptive fase • Systemic fluoride during teeth mineralization leads to F enamel absortion ( fluorapatita) and more resistance to decay. • May enhance the resistance of the tooth by way of: • An alteration in tooth morphology, ( cusps are rounder , the fissures are more shallow, fissure approximation is abrupt and tight and • A conversion of the hydroxiapatite mineral to fluoridated state with an attendant reduction in solubility and an enhancement of the mineralization phase of the caries process D Caroline Mohamed
Pre-eruptive fase and post-eruptive fase. • In teeth, as in all the mineralized tissues, fluoride levels tend to be greatest at the surface nearest the tissue fluid that supplies the fluoride. • Pre eruptive accumulation is highest on the pulpal aspect of the dentin and the outer surface of the enamel. • A much higher total fluoride concentration is found in the dentin because of endogenous fluoride supply from the vessels of pulp. • The outer surface of the enamel will receive a "topical” supply of fluoride from the surrounding follicular fluid, explaining why fluoride concentrations decrease from the inner surface of the dentin and the outer surface of the enamel, respectively.
The concentration of fluoride is also higher in those parts of the enamel that are the first to develop and mature ie, the incisal edges of the anterior teeth and the occlusal surfaces of the molars and premolars. • These pre eruptive effects of fluoride may reduce susceptibility to initiation of fissure caries in the molars during eruption and possibly around the approximal contact surfaces before secondary, posteruptive maturation is completed.