Sodium Fluoride: Uses, Mechanisms, and Safety

Tooth Anatomy

• Teeth consist of three layers of calcified tissue: enamel, cementum, and dentin.
• Enamel is white, hard calcified tissue made of calcium phosphate and calcium carbonate, covering the dentin.
• Cementum is a layer that covers the part of the tooth buried in the gum.
• Dentin is beneath the enamel and cementum, surrounding the pulp cavity.
• Dentin is composed of 75% mineral and is hard and dense.
• Enamel is composed of 98% mineral, making it the hardest substance in the body.
• Vitamins A, C, and D are needed for proper tooth formation.
• Vitamin A deficiency can cause hypoplastic enamel.
• Vitamin C deficiency affects dentine calcification.
• Vitamin D aids calcium absorption and the deposition of calcium and phosphate in teeth.
• Magnesium, chloride, carbonate, and citrate ions are also present in teeth.

Common Dental Terms

• Abscess: A serious infection caused by severe decay, with pain and swelling as symptoms.
• Bleaching: A process using hydrogen peroxide solution to whiten discolored teeth.
• Crown: An artificial cover for a damaged tooth, made of plastic, metal, porcelain, or a combination.
• Filling: Material (amalgam, plastic, porcelain, or gold) used to fill a cavity.
• Orthodontic treatment: Correcting teeth position with braces or similar devices.
• Root Canal therapy: Cleaning and filling the pulp of a damaged or decayed tooth, also known as endodontics.
• Periodontitis: Gum disease leading to tooth loss, involving inflamed gums, plaque, and bone loss.

Introduction to Dental Products

• Dental products maintain dental hygiene and prevent tooth decay.
• Maintaining clean teeth helps prevent decay.
• Numerous products and inorganic compounds help maintain oral and dental hygiene.

Classification of Dental Products

• Dental products include anticaries agents, cleaning agents, desensitizing agents, cements, and fillers.
• Anticaries agents help prevent dental decay, such as sodium fluoride, stannous fluoride, and sodium monofluorophosphate.
• Cleaning agents (dentifrices/polishing agents) clean and polish teeth and remove stains via abrasive action.
• Cleaning agents are available as paste, powder, gel, or liquid and include calcium carbonate, dibasic calcium phosphate, calcium phosphate, and sodium metaphosphate.
• Desensitizing agents reduce teeth sensitivity to temperature, such as strontium chloride and zinc chloride
• Cements and fillers temporarily cover or protect areas in dental surgery, like zinc eugenol cement.

Anticaries Agents

• Anticaries agents include sodium fluoride, stannous fluoride, and sodium monofluorophosphate.
• Dental caries involves enamel and dentin demineralization.
• Untreated caries may result in microorganisms invading the pulp.
• Dental caries is an infectious disease (dental plaque) involving acid production from oral bacteria acting on carbohydrates.
• Dental plaque is a sticky biofilm or bacterial mass in the mouth.
• Dental caries causes tooth decalcification and bad breath.
• Dentifrices enhance stain and plaque removal.
• Preventing caries involves brushing and fluoride administration.

Mechanisms of Action of Fluoride

• Fluorides deposited on teeth prevent acid or enzyme action that produces cavities.
• Fluoride replaces the hydroxyl ion in hydroxyapatite to form fluorapatite on the enamel surface, protecting against tooth decay.
• Fluorapatite hardens enamel and makes it acid-resistant and may also promote enamel remineralization and possess antibacterial activity.
• Trace amounts of fluoride prevent dental caries.

Administration and Effects of Fluoride Overdose

• Fluoride can be administered orally or topically.
• Oral fluoride is absorbed in the gastrointestinal tract, deposited in bone and teeth, with the remainder excreted by kidneys.
• A small fluoride quantity (0.5 -1 ppm) prevents caries.
• Excess fluoride ingestion (2-3 ppm) leads to dental fluorosis (mottled enamel), increased bone density, or gastric disturbances.
• High fluoride intake can cause muscular weakness, convulsions, and even heart failure.
• Topical fluoride solutions, mouthwashes, and gels are less effective than oral fluoride.
• A daily dose of 2.2 mg of sodium fluoride is generally recommended.

Sodium Fluoride

• The molecular formula for sodium fluoride is NaF.
• The molecular weight for sodium fluoride is 41.99 g/mol.
• Sodium fluoride should contain 98-102% of sodium fluoride, calculated with reference to the dried substance.
• It can be prepared by neutralizing hydrofluoric acid with sodium carbonate: 2HF + Na2CO3 --> 2NaF + H2O + CO2.
• Another preparation method involves double decomposition of calcium fluoride with sodium carbonate.
• Sodium Fluoride Properties include: it being a white powder or colorless crystals, soluble in water, and insoluble in ethanol.

Sodium Fluoride - Identification, Uses, Application, and Cautionary Information

• To test for sodium fluoride, sodium fluoride is combined with sulfuric acid in a platinum crucible covered with polished glass, heated in a ventilated hood, and the glass will be etched.
• Sodium fluoride retards or prevents dental caries because fluoride ions are an agent in dental practice.
• Fluoridized teeth resist microorganisms and decrease microbial acid production.
• A 2% aqueous solution of Sodium Fluoride is widely used topically.
• Optimal fluoride in drinking water is 1.5 to 3 ppm, or a 2% solution topically on teeth.
• Sodium fluoride is poisonous in larger doses, and high fluoride water (>3 ppm) causes mottling of teeth and gastric disturbances.
• Large doses of Sodium Fluoride can lead to systemic toxicities affecting central nervous, cardiovascular, musculoskeletal, and respiratory systems.

Stannous Fluoride

• The molecular formula for stannous fluoride is SnF2
• The molecular weight for stannous fluoride is 156.7 g/mol
• Stannous fluoride should contain not less than 71.2% of stannous ion and not less than 22.3% and not more than 25.5% of fluoride when dried.
• Stannous fluoride is prepared by evaporating stannous oxide in hydrofluoric acid without oxygen.
• Stannous fluoride is a white crystalline powder with a salty, astringent taste.
• It is soluble in water but insoluble in alcohol.
• An aqueous solution of stannous fluoride will produce a white precipitate of stannous hydroxide upon standing.
• Stannous Fluoride should be kept in an airtight container to prevent oxidation to stannous tetra-fluoride.
• Stannous fluoride can be identified by adding calcium chloride to its solution, forming a white precipitate of calcium fluoride.
• Another test involves mixing stannous fluoride with silver nitrate, forming a brown precipitate.
• Stannous fluoride prevents dental caries as a solution, gel, mouthwash, or dentifrice, but may discolor teeth with over use.

Cleaning Agents (Dentifrices/Polishing Agents)

• Cleaning agents include Calcium carbonate, Dibasic calcium phosphate, calcium phosphate, sodium metaphosphate, and calcium pyrophosphate.
• Cleaning Agents utilize agents for cleaning and polishing tooth surfaces.
• These agents physically remove plaque and debris, are abrasive in nature, and provide whiteness to teeth and applied as powders or pastes
• Cleaning Agents Drawbacks: They are unable to clean surfaces inside cavities and crevices
• Cleaning action depends on abrasive property and rubbing force; pumice is too abrasive for daily use

Dibasic Calcium Phosphate/ Dicalcium Phosphate

• Dibasic calcium phosphate is also known as dicalcium phosphate or dicalcium orthophosphate or calcium hydrogen phosphate.
• It occurs as a dihydrate (CaHPO4.2H2O).
• When exposed to air, it effloresces to anhydrous dibasic calcium phosphate (CaHPO4).
• In fine powder form is used un dentifrices
• Dibasic Calcium Phosphate provides good flow properties and is odorless and tasteless

Dibasic Calcium Phosphate (Method of Preparation and Uses)

• Dibasic calcium phosphate is prepared by reacting neutral calcium chloride with disodium hydrogen phosphate: CaCl2 + Na2HPO4 --> CaHPO4 + 2NaCl
• Dibasic calcium phosphate has a 1:1 ratio of calcium to phosphorus and is recommended for oral administration as an electrolyte replenisher.
• It can supply both calcium and phosphorus for children's growth and pregnant women.
• Externally it is used as a dentifrice for its cleaning action, making it suitable for toothpastes and tooth powders.

Calcium Carbonate

• The molecular formula of calcium carbonate is CaCO3.
• The molecular weight of calcium carbonate is 100.1 g/mol.
• Calcium carbonate can be referred to as precipitated chalk, or precipitated calcium carbonate.
• Calcium carbonate is a widely distributed calcium salt found as chalk, marble, limestone, aragonite, calcite, and in pearls and shells.
• On a commercial scale, calcium carbonate is obtained by mixing boiling calcium chloride and sodium carbonate, leading to a precipitate.
• Calcium carbonate is a white, micro-crystalline powder that is odorless and tasteless. It is stable in air, almost insoluble in water and alcohol and neutralizes acids with effervescence.

Calcium Carbonate (Uses)

• Precipitated chalk, with its fine powdery texture, is used in dentifrices.
• It furnishes both abrasive and antacid effects in tooth powder and toothpaste.
• Calcium Carbonate can cause constipation and is administered with magnesium salts.
• Acting rapidly as a non-systemic antacid, it neutralizes gastric acid and forms calcium chloride: CaCO3 + 2 HCl --> CaCl2 + CO2 + H2O

Desensitizing Agents

• Desensitizing agents such as strontium chloride and zinc chloride reduce pain in sensitive teeth caused by temperature or touch.
• These products are non-abrasive and used only as directed by a dentist.
• Desensitizing agents act like local anesthetics; however, the exact mechanism of action is unknown.

Strontium Chloride and Zinc Chloride

• The molecular formula for Strontium chloride is SrCl2. 6H2O
• The molecular weight for Strontium chloride is 266.2 g/mol.
• Strontium chloride is prepared by adding strontium carbonate to hydrochloric acid until effervescence ceases.
• The filtered solution is concentrated and crystallized: SrCO3 + 2HCl --> SrCl2 + H2O + CO2.
• Strontium chloride is available as white crystals or granules, produces effervescence in dry air and is soluble in water and alcohol.
• Strontium chloride acts as desensitizing agents in dental remedies

Zinc Chloride (Preparation and Uses)

• The molecular formula for zinc chloride is ZnCl2.
• Zinc chloride is prepared by heating granulated zinc with hydrochloric acid until hydrogen evolution stops, then filtering and evaporating to dryness: Zn + 2HCl --> ZnCl2 + H2
• It is used as an antiseptic astringent for skin and mucous membrane solutions from 0.5-2.0%.
• Zinc chloride is an ingredient in magnesia cements for dental fillings and certain mouthwashes
• Also, Zinc chloride is uses used topically as a dentin desensitizer using a 10% solution in teeth, administered as solution and mouthwash.

Cement and Fillers and Zinc Oxide Eugenol (ZOE) Cement

• Dental cement temporarily or permanently cover and protect areas after dental surgery.
• The cementing material is applied as a paste that hardens to form a protective layer until removed after tissue healing.
• Temporary cement is often medicated with eugenol which is typically antiseptic and local anesthetic.
• Zinc oxide eugenol (ZOE) cement contains zinc oxide and eugenol in oil of cloves
• They have low strength, cause the least irritation, and have an obtundent effect on exposed dentin.

ZOE Cement - Classification, Preparation System, and Method of Preparation

• Type I ZOE is for temporary cementation.
• Type II ZOE is for permanent cementation.
• Type III ZOE is for temporary filling and thermal base.
• Type IV ZOE is for cavity liners.
• ZOE cement is available as a powder and liquid or in a paste system.
• Hydrolysis of zinc oxide yields zinc hydroxide: ZnO + H2O --> Zn (OH)2
• Zinc hydroxide reacts with eugenol to form zinc eugenolate: Zn (OH)2 + 2HE --> ZnE2+2H2O

ZOE (Structure and Uses)

• The chelate formed in ZOE cement is an amorphous gel that crystallizes, imparting strength and setting time is around 4-10 minutes for the set cement
• The set cement includes particles of zinc oxide embedded in a matrix of zinceugenolate.
• Zinc oxide eugenol is used in temporary and permanent cementation and pulp capping agent and reduces the pain.
• ZOE also has anesthetic and antibacterial activity.