Focus on fluorides: update on the use of fluoride for the prevention of dental caries

Abstract

Improving the efficacy of fluoride therapies reduces dental caries and lowers fluoride exposure.

Background: Fluoride is delivered to the teeth systemically or topically to aid in the prevention of dental caries. Systemic fluoride from ingested sources is in blood serum and can be deposited only in teeth that are forming in children. Topical fluoride is from sources such as community water, processed foods, beverages, toothpastes, mouthrinses, gels, foams, and varnishes. The United States Centers for Disease Control and Prevention (CDC) and the American Dental Association (ADA) have proposed changes in their long standing recommendations for the amount of fluoride in community drinking water in response to concerns about an increasing incidence of dental fluorosis in children. Current research is focused on the development of strategies to improve fluoride efficacy. The purpose of this update is to inform the reader about new research and policies related to the use of fluoride for the prevention of dental caries.

Methods: Reviews of the current research and recent evidence based systematic reviews on the topics of fluoride are presented. Topics discussed include: updates on community water fluoridation research and policies; available fluoride in dentifrices; fluoride varnish compositions, use, and recommendations; and other fluoride containing dental products. This update provides insights into current research and discusses proposed policy changes for the use of fluoride for the prevention of dental caries.

Conclusions: The dental profession is adjusting their recommendations for fluoride use based on current observations of the halo effect and subsequent outcomes. The research community is focused on improving the efficacy of fluoride therapies thus reducing dental caries and lowering the amount of fluoride required for efficacy.

Keywords: Fluoride; Fluorosis; decay prevention; fluoride delivery systems.

Figure 1. Halo Effect Sources

Percentage source contribution to total daily fluoride intake: 90th Percentile Drinking Water Intakes for Consumers Only and a Fluoride Concentration of 0.87 mg/L. Image from Environmental Protection Agency. Fluoride: Exposure and Relative Source Contribution Analysis. 2010, page 99.

Figure 2. Fluorosis – tooth hypomineralization resulting in a change in the appearance of teeth

Causes:

1. Long term ingestions of higher than optimal levels of fluoride during tooth mineralization

2. Use of antibiotics (amoxicillin) during childhood < 6 years of age

3. Genetic predisposition

Images from Centers for Disease Control and Prevention. Community Water Fluoridation, Images of Fluorosis, http://www.cdc.gov/fluoridation/faqs/dental_fluorosis/.

Figure 3. Relationship between equivalent fluoride in water and fluorosis incidence and caries DMFT experience

The percent caries experience (DMFT) and fluorosis was reported for 12 to 14 year old children in 21 communities. The categories for fluorosis are: Normal, white; Questionable (Δ) yellow; Very Mild (□) cyan; Mild (◇) green; Moderate (▲) blue; and Severe (◆) red areas. The caries experience in permanent teeth is reported as diseased, missing, or filled teeth (●) heavy black curve. The red arrow shows the current incidence of very mild fluorosis, and the blue arrow shows the anticipated incidence of very mild fluorosis due to the reduction of community water fluoride concentration by 0.3 ppm F. Adapted from data published by Dean^,

Figure 4. Salivary fluoride concentration 1 hour after indicated fluoride and calcium therapies. This comparison of the salivary fluoride concentration after 1 hour is for the following rinses or toothpastes in singly or in combination. The error bars are 95 % confidence intervals

The therapies are:

1. None: no rinse baseline; n = 10

2. C-R: 20 mL of 150 mmol/L calcium lactate 60-second rinse; n = 12

3. F-R: 20 mL of 228 ppm (12 mmol/L) NaF 60-second rinse; n = 12

4. F-R/C-R: 20 mL of 228 ppm NaF 60-second rinse followed by 20 mL of 150 mmol/L calcium lactate 60-second rinse; n = 12

5. Fp/H₂O: 60-second brush with 1.5 g of 1100 ppm NaF toothpaste followed by a 10 second rinse with 10 mL H₂O; n = 12

6. C-R/Fp/H₂O: 20 mL of 150 mmol/L calcium lactate 60-second rinse followed by a 60-second brush with 1.5 g of 1100 ppm NaF toothpaste and then followed by a 10 second rinse with 10 mL H₂O; n = 12

7. Cp/F-R: 60-second brush with 1.5 g of 5.6 % (w/w) calcium glycerophosphate toothpaste followed by a 20 mL of 228 ppm NaF 60-second rinse; n = 11

8. C-R/F-R: 20 mL of 150 mmol/L calcium lactate 60-second rinse followed by a 20 mL of 228 ppm NaF 60-second rinse n = 12.

Figure 5. Comparison of fluoride concentrations in overnight salivary samples after a calcium pre-rinse or a fluoride rinse

Fluoride concentration in saliva samples obtained overnight after 60-second 20 mL rinse as follows: Baseline distilled water (H₂O), 228 ppm fluoride (F-R Lo), 912 ppm fluoride (F-R Hi), or 150 mmol/L calcium lactate pre-rinse immediately followed by a 228 ppm fluoride rinse. All fluoride was from sodium fluoride. The error bars are standard errors (N = 12) statistical differences (p < 0.05, Holm-Sidak pairwise multiple comparison test) are indicated by the letters. Data from Vogel et al (2008)

Figure 6

Fluoride uptake into hydroxyapatite after 3 hours exposure to F-varnishes of varying concentration of sodium fluoride.