Table of Contents

Continuing Education
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Inside Dental Assisting

Jan/Feb 2012, Volume 8, Issue 1
Published by AEGIS Communications

Fluoride: an Essential Component in Oral Health

The appropriate use of fluoride in caries prevention and inhibition

Lois Dondiego, BASDH, RDH, CDA

Providing a fluoride treatment is a common procedure performed in dental offices every day across the country by dentists and dental hygienists after a prophy treatment. In certain states where it is permissible, dental assistants are allowed to perform this procedure under the scope of their expanded functions certification. Understanding how fluoride works and how to correctly provide this treatment to patients, along with knowledge of the safely administered dosage, is valuable information for every dental assistant.

How Fluoride Helps Enamel

Prior to eruption, the tooth is engulfed by a fluid-filled sac.1 This fluid may contain small amounts of maternal fluoride,2 which protects the developing tooth by making it more impervious to acid caused by bacteria.1 It does this by replacing some of the hydroxyl ions in the apatite crystal2 (a crystalline mineral component of hard tissues such as bones and teeth)3 during the mineralization stage of tooth development. This new structure called fluorapatite supplements tooth enamel, creating more enamel mass.2 The deposition of fluoride continues in the enamel surface after mineralization and before tooth eruption.3 After tooth eruption, fluoride will continue to strengthen the enamel through topical applications.2

Because fluoride is a mineral nutrient found in food, plants, and water, it is considered a natural cavity fighter.1 Fluoride consumption is available in two forms: systemic and topical. Systemic fluoride is found in foods, water supplies in communities that supplement with fluoride, and in some bottled water.3 Systemic fluoride is absorbed through the intestines, into the bloodstream, and transported to the blood vessels in the oral cavity.3 Systemic delivery of fluoride incorporates 1000 to 2000 parts per million (ppm) of fluoride into the enamel outer surface of the tooth, while according to some results, topical sources of fluoride can provide 30,000 ppm to the enamel.4

Topical fluoride is applied to the teeth by direct contact through its various forms: gels, foams, varnish, rinses, and fluoridated toothpastes. Topical fluoride provides three ways to prevent and inhibit dental caries formation:

  • Fluoride inhibits demineralization of the enamel by adsorbing into the enamel crystals inside the tooth, protecting the crystal surface from being broken down by the acid caused by cariogenic bacteria.
  • Fluoride acts to speed up remineralization: by absorbing into the crystal surface of the enamel it attracts calcium ions to the surface of the enamel, facilitating remineralization.
  • Fluoride inhibits bacterial activity by causing interference with key enzymatic pathways and acidifying the cytoplasm in the bacteria after it enters the bacteria cells.4


Types of Fluoride Treatments

Topical fluoride treatments are generally provided to children and other patients who do not live in fluoridated communities, and to patients with a high caries risk because of diet or improper oral hygiene. Treatments may also be administered to patients who experience a compromised salivary flow from chemotherapy or radiation therapy to the head and neck, and those patients with xerostomia (dry mouth) caused by medications or medical issues such as diabetes. Additionally, treatment is recommended for patients who have exposed root surfaces following periodontal therapy and those wearing orthodontic appliances.

The most common professionally applied topical fluorides include Sodium fluoride (NaF), and Acidulated phosphate fluoride (APF).3 Sodium fluoride is available in a solution of 2%, Gel 2%, Foam 2%, and Varnish 5%. A 2% acidulated phosphate fluoride is delivered in a solution of 1.23%, gel 1.23%, and foam 1.23%.3 Acidulated phosphate fluoride is the preferred topical fluoride and is usually recommended to patients and children who have no esthetic restorations in the oral cavity.3 NaF is the fluoride of choice for persons with esthetic restorations, because APF can cause pitting of those types of restorations.1

For patients who require more than two applications of fluoride per year, prescription home fluoride therapies are recommended. These will reduce decalcification and promote remineralization of the enamel surface. They come in the form of toothpastes, dental rinses, and gels.

Topical Fluoride Techniques

The dental auxiliary must always obtain patient consent before any fluoride treatment and of course parental consent prior to treating a child. Explain the procedure to the patient and provide post-treatment instructions such as not eating, drinking, or rinsing for 30 minutes. Next, seat the patient upright to prevent swallowing of the fluoride. There are two procedures to use when giving a fluoride treatment. The first procedure is the paint-on-method, which is not recommended for applying gel or foam due to ingestion issues. This method may be used for young children or a patient with a difficult gag reflux who cannot tolerate a tray.

Apply the fluoride to one side of the oral cavity, then the other. Using a cotton-roll holder and saliva ejector can help in absorbing the excess fluoride and prevent it from being swallowed. It is important that before applying a fluoride solution, dry the teeth with either a 2x2 gauze or compressed air. Saliva in the oral cavity acts as a barrier to fluoride uptake, and drying the teeth prior to the application will allow the fluoride to be absorbed. After all the teeth have been moistened with the fluoride, begin the timing sequence according to the manufacturer’s directions. After the timing sequence has expired, suction the remainder of the fluoride from the oral cavity, wipe the teeth with a 2x2 gauze, and ask the patient to expectorate, but not to rinse. Then proceed to the other side and repeat the procedure. When finished, remind the patient not to eat, drink, or rinse for 30 minutes.3

For the tray technique, the proper size tray for the patient must be selected. Check for areas of recession: a custom-made tray may be required to cover all areas of exposed enamel above the gingiva and exposed root surfaces. To prevent gagging, use a properly fitting tray, utilize suction throughout, seat the patient upright with head tilted slightly forward, and provide reassurance throughout the treatment.3

Place the gel or foam in the tray. To avoid ingestion of the fluoride, use no more than 2 mL of fluoride for children and no more than 5 mL for adults. Dry the teeth and begin the timing sequence; when completed, remove the tray, suction excess fluoride and saliva, wipe any excess from the teeth with a 2x2 gauze. Ask the patient to expectorate, but not to rinse, and give post-treatment instructions.3

When applying a fluoride varnish, the procedure is not as time-consuming and usually all that is needed is a cotton applicator or disposable applicator brush and saliva ejector. For this procedure, brush the fluoride varnish onto each tooth surface—lingual, buccal, and occlusal. It will dry quickly. Follow manufacturer’s directions as to when the patient can eat, drink or rinse.

According to the American Dental Association (ADA) Council on Scientific Affairs position paper,5 fluoride varnish is the safest and most efficient fluoride delivery system for children, and the ADA advocates its use in almost every setting.


The incidence of dental caries can be significantly decreased by 20% to 30% when individuals used fluoridated dentifrices regularly. Additionally, research has shown a 30% to 40% reduction in dental caries when a mouth rinse containing fluoride (even at low concentrations) is used frequently. It has been established that fluoride is a reliable and effective means for improving the oral health of individuals.2

As with most treatments, there are also important safety recommendations for patients. A condition known as dental fluorosis can occur in patients who ingest too much fluoride from excess (fluoride) in the drinking water. The safety level of fluoride in drinking water is 1 ppm and may be adjusted according the amount of water consumed in warmer or colder climates.2 However, the U.S. Department of Health and Human Services is proposing a change to the recommendation for the optimal fluoride level in drinking water. The new recommendation, 0.7 milligrams of fluoride per liter of water, replaces the previous recommended range of 0.7 to 1.2 milligrams per liter. One of the reasons for this change is that Americans have access to more sources of fluoride than they did when water fluoridation was first introduced in the United States.6

Parental supervision is required when children are brushing or using other fluoride supplements. Rinses are not recommended for a child under the age of six, or for individuals who are mentally compromised. Because of potential toxicity, all fluoride products should be equipped with child-proof containers and kept away from children or other individuals who do not understand how to use fluoride.


There are two kinds of fluoride toxicity: chronic and acute. Chronic refers to long-term fluoride amounts above the Safely Tolerated Dose (STD) levels. Chronic fluoride toxicity is most commonly represented by fluorosis. Acute refers to the intake of additional quantities of fluoride that are above the STD, which is estimated to be one-fourth of the Certainly Lethal Dose (CLD). In adults, the CLD amount is between 5 to 10 g sodium fluoride taken at one time. For children, it is approximately 0.5 to 1.0 g, which varies with the size and weight of the child. It should be noted that for a child 12 years old and younger, less than 1 g (1000 mg) can be fatal.2

The first symptoms of acute fluoride toxicity may begin within 30 minutes of ingestion. In the gastrointestinal tract, fluoride forms hydrofluoric acid and begins to irritate the stomach lining. This will cause increased thirst, salivation, nausea, vomiting, diarrhea, and abdominal pain, which may continue for 24 hours. In the blood, symptoms of hypocalcaemia may occur caused by the calcium ions binding by the circulating fluoride. Hyperreflexia and convulsions can occur due to high fluoride levels’ effect on the central nervous system. Last, if not treated, cardiovascular and respiratory depression will result and may lead to death within a few hours from respiratory paralysis or cardiac failure. Emergency treatment may include inducing vomiting by stimulation at the back of the tongue or throat or by Ipecac syrup, in addition to calling 911 for emergency response.2 Current emergency recommendations for acute fluoride toxicity also include administering a calcium-binding agent, such as milk, in addition to stimulation of vomiting and activating emergency medical services. Follow the instructions of the emergency responders or the Poison Control Center.


If parents are reluctant to have fluoride treatments given to their children, one alternative for caries prevention are products containing xylitol. Xylitol is a natural five carbon alcohol sugar discovered in the bark of birch trees by scientists 100 years ago. It is not known for certain how xylitol works. It is theorized that it interferes with the metabolism of Streptococcus mutans. In the presence of xylitol, the S. mutans bacteria is bound to proteins in the cell. Bacteria attached to the transport proteins in the cell limit the transport proteins’ ability to leave the cell and bring in more glucose to feed the bacteria.7

In a two-year study comprising 169 mother–child participants, the results concluded that the mother’s continual use of xylitol chewing gum during pregnancy prevented significant tooth decay in the child by reducing the transmission of S. mutans from mother to child. The children were reassessed two years later and the results indicated that the use of xylitol by the mothers had prevented tooth decay in their children.7


When used correctly, fluoride is a safe and efficient means of providing cavity protection and should be available to appropriate individuals through fluoridated water, professional applications, and consumer products. An effective alternative to the use of fluoride are products that contain xylitol. As more programs are established to eradicate the caries epidemic, the use of fluoride and xylitol will continue to be at the forefront. Knowing how to administer fluoride treatments and what alternatives there are to fluoride is essential information for every dental assistant.


1. Bird DL, Robinson DS. Torres and Ehrlich Modern Dental Assisting. 9th ed. St. Louis, MO: Elsevier Health Sciences; 2008:192-197.

2. Lippincott Williams & Wilkins. Lippincott Williams & Wilkins’ Comprehensive Dental Assisting. 1st ed. Baltimore, MD: Lippincott Williams & Wilkins; 2011:176-177.

3. Wilkins EM. Clinical Practice of the Dental Hygienist. 8th ed. Philadelphia, PA: Lippincott William and Wilkins: 2004:455-474.

4. Young DA, Featherstone JDB, Budenz AW. Dental caries and caries management. In: Daniel SJ, Harfst SA, Wilder R, eds. Mosby’s Dental Hygiene Concepts, Cases, and Competencies. 2nd ed. St. Louis, MO: Elsevier Health Sciences; 2007:474-475.

5. The ADA Council on Scientific Affairs. Professionally Applied Topical Fluoride. Executive Summary of Evidence-Based Clinical Recommendations. May 2006.

6. U.S. Department of Health & Human Services. HHS and EPA announce new scientific assessments and actions on fluoride. January 7, 2011. Accessed January 19, 2011.

7. Hansen A. Xylitol: a dental phenomenon. American Dental Association Web site. Published August 2006. Accessed August 2, 2011.

About the Author

Lois Dondiego, BASDH, RDH, CDA
University of Medicine & Dentistry of New Jersey
Scotch Plains, New Jersey