Cariology and Fluoride Products

Week 8: Introduction to Cariology and Fluoride Products

• Reading assignments: Wilkins Ch. 16, 25, 34 & DH 15 Preventive Dentistry

Objectives

• Distinguish the effects of systemic and topical fluoride application.
• Describe factors related to fluoride toxicity, including signs and symptoms of acute and chronic toxicity, and procedures to minimize toxic reactions at home and in professional settings.
• Describe types of self-applied fluorides for home use.
• Compare relative concentrations of fluoride in dentifrices, at-home gel applications, mouth rinses, and professional applications.

The Caries Process

• Caries is a worldwide problem associated with plaque, microorganisms, and carbohydrate intake.
• Fluoride in the oral environment attenuates the caries process.
• All patients can benefit from appropriate fluoride therapy.

Main Factors in Caries Process

• Plaque
• Host
• Bacteria
• Carbohydrates

Plaque Biofilm

• The acquired pellicle is derived from saliva and binds to the tooth surface.
• The acquired pellicle can act as "double stick tape."
  • Advantage: Protects the tooth surface from direct acid exposure.
  • Disadvantage: Covered by bacteria that forms dental plaque.

Bacteria

• Plaque contains acid-producing bacteria ("acidogenic and aciduric"), such as Strep mutans & Lactobacilli.
• Bacteria produce acid when metabolizing fermentable carbohydrates like glucose, sucrose, fructose, and cooked starch.

Mutans Streptococci & Lactobacilli

• Mutans streptococci are infectious organisms that colonize teeth and help form the dental biofilm by creating a sticky environment.
• They are most active during the initial stages of demineralization and cavity formation.
• Lactobacilli are more active during the progression of caries.

Fermentable Carbohydrates

• Include sucrose, glucose, fructose, starchy foods like bread, cereals, pasta, cooked starches, rice, potatoes, beans, and chestnuts.
• Not just sweets are responsible for dental caries.

Bacterial Acids

• Acids produced by acidogenic bacteria can dissolve the mineral of the teeth (calcium & phosphate), enamel, and dentin.

Demineralization

• The primary mineral of tooth enamel is hydroxyapatite $(Ca<em>{10}(PO</em>4)<em>6(OH)</em>2)$, a crystalline form of calcium phosphate and hydroxide ions.
• Enamel and dentin are comprised of millions of tiny mineral crystals embedded in a matrix.
• Tiny spaces between the crystals are pores that make up small passageways or diffusion channels.
• Demineralization is the process by which the minerals of tooth structure are dissolved by organic acids produced by acidogenic bacteria that metabolize fermentable carbohydrates.
• The enamel is porous enough for small molecules and ions such as calcium, phosphate, fluoride, and organic acids to pass through.
• Acid diffuses from the plaque through the pellicle into the tooth through pores, dissolving the enamel crystals into calcium and phosphate ions.
• As enamel is demineralized during caries progression, the mineral removed makes the enamel even more porous.
• Hydroxyapatite becomes more soluble in acid during demineralization as it becomes contaminated with other minerals, turning into carbonated apatite.

Carious Lesions

• An active white spot lesion will appear dull compared to the translucent enamel.
• A shiny white spot lesion shows signs of an arrested or remineralized lesion.

Caries Process – Reversal

• If detected early enough, the demineralization process can be halted or reversed in a process called remineralization.
• The demineralization process can be reversed or arrested by biochemical means (fluoride) or mechanical means (sealant), or both.

Remineralization

• Saliva is the primary component for caries protection.
• It neutralizes or buffers acids formed by plaque bacteria and clears away bacteria and food debris.
• It contributes calcium and phosphate to prevent demineralization and allows for remineralization to occur.
• Maintaining a neutral salivary pH of 7 is necessary for remineralization.
• Demineralization occurs when pH drops to 5.5.
• If the acid is neutralized and the concentration of calcium and phosphate ions becomes higher outside the tooth than inside, it diffuses back into the tooth.
• The diffusion of minerals back into the tooth replenishes the lost minerals.
• The redeposited minerals combine to form hydroxyapatite crystals, rebuilding the mineral structure of enamel.

Caries Process Intervention

• Replacement of minerals = Remineralization
• Fluoride or MI Paste are remineralizing agents.
• Fluoride can make the crystals of the teeth less soluble/ “more perfect.”
• The improved crystal is fluorapatite.
• Fluorapatite has a pH of 4.5, making the tooth structure more resistant to acid/ caries.
• The form of fluorapatite can help prevent tooth decay.

Summary by Solubility

• Fluorapatite: least soluble in acid
• Hydroxyapatite: less soluble in acid
• Carbonated Apatite: most soluble

Demineralization/Remineralization Process

• Demineralization and remineralization are natural processes as oral cavity fluids constantly strive to maintain equilibrium.
• When demineralization outweighs remineralization, caries occurs.
• When remineralization outweighs demineralization, caries can be reversed.
• If the diet is balanced, in which host protective factors (saliva) and fluoride can overcome the bacterial acid challenge, no net demineralization occurs.
• Increased frequency of foods that are acidogenic can tip this balance in the direction of demineralization.

Stages in the Formation of Carious Lesions

• Refer to Chapter 16 for details.

Initial Stage Caries

• Early caries or incipient lesions.
• Demineralized enamel with no breakthrough or cavitation of the enamel surface.
• Caries is a subsurface phenomenon, meaning subsurface demineralization occurs where acid diffuses through microchannels from the surface of the enamel to the subsurface in the dentin.
• Clinically:
  • Earliest clinical evidence of dental caries is a white spot lesion, resulting from up to 50% of mineral loss.
  • Characterized by chalky, white appearance.
  • When dried, tooth surface may have an opaque or dull appearance rather than shiny as in health.
  • Surface may become brownish overtime.

Moderate Stage Caries

• Breakdown of enamel over the demineralized area.
• Clinically:
  • Underlying dark shadow with transillumination.
• Radiographically, the radiolucency extends into the dentin.

Extensive Stage Caries

• Cavitation exposing dentin.
• Radiolucency extends into the inner half of dentin or into pulp.

Fluoride

• A nutrient taken into the body by way of:
  • Water containing fluoride (natural/ fluoridated).
  • Dietary supplements.
  • Certain foods (tea, seafood, processed foods, fruits and veggies, meat, dairy products).
• 99% of the fluoride in the body is located in mineralized tissues.
• “Parts Per Million” (PPM): The unit of measure to designate the amount of fluoride used for optimum levels in water or fluoride containing products. 1PPM = 1mg/ L
• Fluoride intake can be systemic or topical.
• The most common source is drinking water.
• Fluoride will provide a topical source as it washes over teeth.
• Food and beverages prepared at home may also be treated with fluoridated water.
• Can also be ingested from dentifrices/ mouth rinses/ supplements.

Fluoride and Tooth Development

• Pre-eruptive: Mineralization stage
  • Fluoride is deposited during the formation of enamel and then incorporated into the hydroxyapatite crystal.
  • Effects of excess fluoride: Dental Fluorosis is a form of hypo-mineralization that results from ingestion of excess amount of fluoride during tooth development.
• Pre-eruptive: Maturation Stage
  • After mineralization is complete, fluoride is then deposited into the enamel surface.
• Post-eruptive
  • After eruption, the concentration of fluoride on the enamel surface will depend upon different topical sources.
• For the erupted enamel, the highest concentration is at the outer surface exposed to the oral cavity.
• The level of fluoride in cementum is high and increases with exposure.
  • With recession, the root surface is exposed to the fluids of the oral cavity.

Types of Systemic Fluorides

1. Water Fluoridation:
   • Community Water Fluoridation
   • School Water Fluor
2. Salt Fluoridation
3. Milk Fluoridation
4. Fluoride Tablets

Systemic Fluoride

• Fluoridated water and prescription supplements incorporate insufficient amounts of fluoride systemically for optimal caries prevention.
• Amount of fluoride deposited:
  • 1000 – 2000 ppm on the outer surface of enamel
  • 20 – 100 ppm below the surface
• Versus: topical fluoride at approximately 30,000 ppm to the individual crystals of enamel.

Topical Fluoride

• Topical uptake means fluoride diffuses into the surface of the enamel of an erupted tooth.
• Common misconceptions:
  • That systemic fluoride is the most effective anti- cavity form.
• Standard of care still recommends systemic because the fluoride will still work by topical means.

Topical vs Systemic

• Public health standpoint:
  • A way to reach the lower socio-economic population that may not have access to other fluoride products.
  • This led to water fluoridation and the use of oral fluoride supplements.

Water Fluoridation

• Natural fluoride content is adjusted in domestic municipal water supply to concentration levels that are optimal for caries prevention WITHOUT causing fluorosis (Controlled by the EPA).
• The US Department of Health and Human Services recommended that the optimal ppm for water fluoridation is 0.7ppm in 2011.
• Water Fluoridation = the most efficient, effective, reliable, and inexpensive means for oral health.
• CDC called Fluoridation the 10 most significant public health measures of the 20th century.

Fluoride Action

1. Inhibition of demineralization
2. Enhancement of remineralization
3. Inhibition of bacteria by inhibiting enolase, an enzyme needed by bacteria to metabolize carbohydrates

Inhibition of Demineralization

• Fluoride ions will adsorb to the surface of the crystals, forming a protective layer.
• It will act as a barrier against acid and protect the surface from being dissolved.

Enhancement of Remineralization

• Fluoride attracts calcium and phosphate ions leading to rapid crystal growth.
• Fluoride ions attract and bond with calcium and phosphate ions, forming a compound called fluoroapatite.

Inhibition of Bacteria

• Fluoride interferes with the metabolic processes of acid-producing bacteria present in dental plaque.
• It will inhibit the enzymatic activity, which reduces the production of acids as byproducts.

Fluoride and Saliva

• Saliva is the single most important factor in the maintenance of oral health.
• It contains many protective proteins and minerals, keeping them available in the solution.
• Fluoride in the saliva can help with remineralization.
• By using fluoride products, the beneficial levels can be sustained for as long as 2-6 hours in the saliva and in the plaque (depending on the product and the individual).

Fluoride Benefits

• Most effective method for dental caries prevention and control.
• Available in two main forms:
  • Systemically: by way of circulation to developing teeth (pre-eruptive).
  • Topically: directly on exposure surfaces of erupted teeth (post- eruptive).
• Most beneficial through topical effects, but maximum caries inhibition is through a combination of:
  • Systemic exposure before tooth eruption
  • Frequent topical fluoride exposures throughout life after teeth are erupted

Fluoride Products

• KNOW PPMs

Self-Applied Fluoride

• Prescription and OTC products are available as: dentifrice, mouth rinse, gels
• OTC: 1500ppm or less

Fluoride Dentifrices

• Approved by ADA for caries prevention
• 1st approved in 1960 → 0.4% stannous fluoride
• Major side effect: Orange-brown stain
• Current Fluoride Constituents:
  • Sodium fluoride (NaF) 0.24% (1100ppm)
  • Sodium monofluorophosphate (Na2PO3F) 0.76% (1000ppm)
  • Stannous fluoride (SnF2) 0.45% (1000ppm)

Fluoride Mouth Rinses

• 0.05% NaF (OTC) - 225-230 ppm, Once daily
• 0.0221% NaF (OTC) - 100 ppm, Twice daily
• 0.2% NaF (Rx) - 905 ppm, Once daily or once weekly
• 0.044% NaF and APF (OTC) - 200 ppm, Once daily

Fluoride Gel

• Neutral Sodium Fluoride 1.1%: 5,000 ppm
• Stannous Fluoride 0.4%: 1,000ppm

Fluoride Supplements

• Introduced in the 1940s; intended to compensate for insufficient fluoridated drinking water
• In 1994, American Academy of Pediatric Dentistry created a supplementation dosage schedule:
  • For children 6 mos to 16 years consuming drinking water that contains <0.6ppm of fluoride
• Clinical recommendations from the American Dental Association Council on Scientific Affairs includes the use of fluoride supplements for children:
  • Who are at high risk of developing caries
  • Whose primary source of drinking water is deficient in fluoride
• Sodium fluoride supplements are available as tablets, lozenges and oral drops
  • Tablets and lozenges:
    • Tablets are chewed; lozenges dissolved for 1- 2minutes
    • Available in 0.25 mg, 0.50 mg and 1.0 mg dosage
  • Drops:
    • Liquid concentrate to be dropped directly into mouth or mixed with meals
    • Primary use for children from 6months – 3 years

Professionally Applied Fluoride

• Consider the individual patient needs when choosing the appropriate fluoride form (i.e. Caries risk, extensive restorations)
• Forms:
  • Gels or foams delivered in trays
  • A varnish applied with a brush on teeth
• Table 36-2 Professionally applied topical fluorides:
  • Sodium Fluoride (NaF) Gel or Foam
  • Acidulated Phosphate Fluoride (APF) Gel or Foam
  • Neutral Sodium Varnish
• 2.0% SODIUM FLUORIDE (NaF)
  • Concentration: 9,050ppm pH: 7.0 (neutral sodium fluoride)
  • Foam or gel in tray for 4 minutes
  • Do not Overfill!
• 1.23% ACIDULATED PHOSPHATE FLUORIDE (APF)
  • Concentration: 12,300 ppm pH:3.5
  • Low pH enhances fluoride uptake, but because of low/ acidic pH may etch porcelain or composite restorations (contraindication!)
  • Application: tray for 4 minutes. At least every 3-6 mos.
• 5% NEUTRAL SODIUM FLUORIDE VARNISH (NaF)
  • Concentration: 22,600ppm, but less fluoride is used per application (<7mg)
  • pH: 7.0 (neutral)
  • Application: apply thin layer with brush in 1-2 minutes
  • For caries reduction, ideal application is every 3-6 months
  • Effective for demineralization from ortho
  • Effective is reversing pit and fissure enamel lesions in primary dentition and remineralizing enamel lesions
  • Application of choice for dentin hypersensitivity
  • Only professional topical fluoride to be used in children younger than 6 y.o.

Fluoride Safety

• Fluoride is beneficial in small amounts, but can be injurious if used without attention to correct dosage
• All dental personnel needs to be familiar with:
  • Recommended approved procedures
  • Potential toxic effects of fluoride
  • How to administer general emergency measures should overdoses occur
• Instruct patients in proper care of fluoride products:
  • Dentist prescribes no more than 120 mg of fluoride at one time
  • Request parental supervision for child’s brushing
  • Keep fluoride products out of child’s reach

Dental Fluorosis

• Fluoride is safe when used as directed.
• Appears as a white stain that later may become discolored and brown.
• Excessive amounts during formation can cause pitted or mottled teeth
• Teeth exposed to an optimum of slightly higher level of fluoride appear white and opaque, without blemishes
• If higher than optimum fluorosis appears as white bands or flecks
• Ingestion of naturally occurring excess fluoride in drinking water and/ fluoridated dental products can produce visible fluorosis
• Typically occurs during years of development: No systemic symptoms birth to 12-16 years or when 3rd molars are complete

Fluoride Toxicity

• Acute toxicity
  • Rapid intake of an excess dose in a short time
• Chronic toxicity
  • Long-term ingestion of fluoride in amounts exceeding approved therapeutic levels
• Accidental ingestion
  • Can lead to a toxic reaction. Acute fluoride poisoning is rare
• A lethal dose is the amount of a drug likely to cause death if not intercepted by antidotal therapy
  • Certainly Lethal Dose (CLD)
    • Adult CLD: 5-10 g of sodium fluoride taken at one time
    • Child: 0.5-1.0 g varies depending on size and weight of child
• Signs and symptoms of acute toxic dose
  • Symptoms begin within 30 minutes of ingestion and may persist for as long as 24 hours
    • GI: nausea, vomiting, diarrhea, abdominal pain, increased salivation, thirst
    • Systemic: vascular, CNS, cardiovascular, respiratory systems

Objective Recap

• Which OTC at-home product contains the lowest concentration of sodium fluoride? And what is the appropriate unit of measure for fluoride?
  • a. Mouthrinse
  • b. Toothpaste
  • c. Gel Supplement
• TRUE or FALSE: Placement of topical fluoride (ie. varnish) will typically deposit more fluoride than systemic fluoride (ie. water).
• Which is the standard of care and why?