Chapter 6:

Fluorides (Topical and Systemic)

Kathleen Ziegler, PharmD

Overview

Fluoride is a mineral that is found in all natural water sources. Fluoride is the ionic form of the trace element fluorine. Fluorine is commonly found in the environment and reaches water sources by leaching from soil and rocks into groundwater.

The process of caries is multifactorial and, over time, can culminate in localized destruction of hard dental tissues by the weak acids produced by bacterial carbohydrate fermentation. Fluoride remineralizes the calcium hydroxyapatite structure in enamel by forming calcium fluorapatite, which is more resistant to acid attacks. The remineralization effect of fluoride can both reverse the early decay process and create a tooth surface that is more resistant to decay.

Fluoride can be delivered topically and systemically. Topical fluorides strengthen teeth already present in the mouth, making them more decay resistant. Topical fluorides encourage remineralization of enamel, and also inhibit bacterial metabolism, reducing the growth of plaque bacteria. Modes of topical fluoride delivery include toothpastes, gels, mouthrinses, and professionally applied fluoride therapies.

Systemic fluorides are those that are ingested and become incorporated into forming tooth structures. Systemic fluorides can also confer topical protection because fluoride is present in saliva, which continually bathes the teeth. Modes of systemic fluoride delivery include water fluoridation or dietary fluoride supplements in the form of tablets, drops, or lozenges.

1 | Fluorosis

A potential risk of fluoride is the development of fluorosis. Fluorosis of permanent teeth occurs when an excess quantity of fluoride is ingested for a sufficient period while tooth enamel is being mineralized. The level of fluoride intake between the ages of about 15 and 30 months is thought to be most critical for the development of fluorosis of the maxillary central incisors. The mechanisms by which fluoride modifies tooth development are not fully understood, but may result from alterations in protein metabolism disrupting the crystal organization in the developing tooth. Once teeth erupt, they cannot develop enamel fluorosis.

Fluorosis varies in appearance from white striations to stained pitting of enamel and does not affect the function or health of the teeth. Excess fluoride exposure can be minimized by using the recommended amount of toothpaste (Table 1) and by storing toothpaste where young children cannot access it without parental assistance. Parents should supervise their child’s use of fluoride toothpaste to avoid overuse or ingestion.

*See complete guideline at https://ebd.ADA.org

2 | Professionally Applied Topical Fluorides

Fluoride Gels, or Foams

Professionally-applied fluorides are more concentrated than self-applied fluorides, and therefore are not needed as frequently. Because these applications are relatively infrequent, generally at 3- to 12-month intervals, fluoride gel poses little risk for dental fluorosis, even among patients younger than six years of age. Routine use of professionally-applied fluoride gel or foam likely provides benefit to persons at high risk for tooth decay, especially those who do not consume fluoridated water and brush daily with fluoride toothpaste.

Because early studies reported that fluoride uptake by dental enamel increased in an acidic environment, fluoride gel is often formulated to be highly acidic (pH of approximately 3.0). Products available in the United States include gels of acidulated phosphate fluoride (1.23% [12,300 ppm] fluoride), as 2% neutral sodium fluoride products (containing 9,000 ppm fluoride), and as gels or foams of sodium fluoride (0.9% [9,040 ppm] fluoride). In a dental office, fluoride gel is generally applied for 1 to 4 minutes, depending on the product used and manufacturer’s directions.

Fluoride-Containing Prophylaxis Paste

According to the Centers for Disease Control and Prevention, “Fluoride-containing paste is routinely used during dental prophylaxis (i.e., cleaning). The abrasive paste, which contains 4,000-20,000 ppm fluoride, might restore the concentration of fluoride in the surface layer of enamel removed by polishing, but it is not an adequate substitute for fluoride gel or varnish in treating persons at high risk for dental caries (151). Fluoride paste is not accepted by FDA or ADA as an efficacious way to prevent dental caries.” (Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5014a1.htm).

Fluoride Varnish

Varnishes are available as sodium fluoride (2.26% [22,600 ppm] fluoride) or difluorsilane (0.1% [1,000 ppm] fluoride) preparations. A typical application requires 0.2 to 0.5 mL, resulting in a total fluoride ion application of approximately 5 to 11 mg.

High-concentration fluoride varnish is painted by dental or other health care professionals directly onto the teeth and sets when it comes into contact with saliva. Fluoride varnish is not intended to adhere permanently; this method holds a high concentration of fluoride in a small amount of material in close contact with the teeth for several hours. Reapplying varnishes at regular intervals with at least two applications per year can help effectiveness. Although it is not currently cleared for marketing by the FDA as an anticaries agent, fluoride varnish has been widely used for this purpose in Canada and Europe since the 1970s. Studies conducted in Canada and Europe have reported that fluoride varnish is as effective in managing tooth decay as professionally-applied fluoride gel. In the United States, fluoride varnish is cleared for marketing by the FDA for use as a cavity liner and a root densensitizer, although it has been used “off label” to prevent caries (Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5014a1.htm).

According to the Centers for Disease Control and Prevention (CDC), there is no published evidence to indicate that professionally-applied fluoride varnish is a risk factor for dental fluorosis, even among children younger than six years of age. Proper application technique reduces the possibility that a patient will swallow varnish during its application and limits the total amount of fluoride swallowed as the varnish wears off the teeth over a period of hours (Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5014a1.htm).

Silver Diamine Fluoride

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