Fluoride and Caries Prevention in Children

Brief History of Fluoride and Preventive Dentistry In 1909, a young dentist in Colorado Springs Colorado, Dr. Frederick McKay made the observation that a large number of his child patients had a brown stain on their teeth, in some instances disfiguring. However, the teeth that were stained appeared to be resistant to dental caries. The Colorado Dental Association invited G.V. Black, the distinguished dental educator at Northwestern University to speak at their annual convention and to investigate the brown stain that has been identified by Dr. McKay. Black could not believe the circumstance had not previously been reported in the dental literature. He spent the remainder of his six years of life studying it.

Brief History of Fluoride and Preventive Dentistry Staining came to be known as Colorado Brown Stain. In 1923, the community of Oakley, Idaho, invited Dr. McKay to consult with them regarding brown stain that had recently begun appearing on their children’s teeth. The source of the community water supply of Oakley had recently been changed; McKay was suspicious of a water-borne causation. He recommended a change in the source of the community’s water supply. After the source was changed, the brown stain subsequently disappeared.

Brief History of Fluoride and Preventive Dentistry In the late 20s, Dr. McKay was asked to visit Bauxite, Arkansas, as the same brown staining of children’s teeth was occurring. Bauxite was a ‘company-town’ of the Aluminum Company of America. McKay investigated with a USPHS dentist and reported findings. However, could not identify anything in the water. In 1933, an Alcoa aluminum chemist, H.V. Churchill, using photospectrographic analysis identified that the substance in the water supply was fluoride.

Brief History of Fluoride and Preventive Dentistry Fluoride is a ubiquitous element in earth’s crust; the 13th most abundant element. Image is of fluorite mineral crystal. Increases in fluoride correlate with increased depth. Deep artesian wells, common in Rocky Mountain Range and extending into Mexico, result in more fluoride in the water. Fluoride is also by-product of aluminum production. Bauxite, Arkansas’ public water intake was downstream from the waste water disposal of the aluminum company.

Brief History of Fluoride and Preventive Dentistry Fluoride is found naturally in low concentration in essentially all drinking water and foods. Waters from underground sources are more likely to have higher levels of fluoride; the concentration in seawater averages 1.3 parts per million (ppm).   Fresh water supplies generally contain between 0.01–0.3 ppm.

Brief History of Fluoride and Preventive Dentistry H. Trendley Dean of the National Institute of Dental Research is credited with first fluoride studies. By 1936, it had been determined that fluorosis does not occur at levels under 1.0 ppm. However, caries preventive effect observed at 1.00 ppm. Subsequent recommendations led to adding varying parts per million fluoride to the water, from 0.7-1.3 ppm, depending on average daily temperatures. Assumption was that people in hotter climates drink more water, therefore need to reduce fluoride concentration in the water.. Recently, recommendation was reduced by the CDC from an average of 1.0 ppm to 0.7 ppm, based on concern regarding increasing prevalence of fluorosis.

Water Fluoridation In 1945, Grand Rapids, Michigan added fluoride to its public water supply, the first community in the world to fluoridate its public water supply. Over next fifteen years fluoridation was studied extensively by NIH. Eight cities were involved as experimental and controls: Grand Rapids and Muskegon, Michigan; Newburgh and Kingston, New York; Evanston and Oak Park, Illinois; and Brantford and Sarnia, Ontario, Canada. Documented that adding fluoride to water supply reduced dental caries by 50-60%, and was safe.

Developmental Changes in Enamel in the Presence of Fluoride Hydroxyapatite is the crystalline form of enamel with the formula Ca10(PO4)6(OH)2. In the presence of fluoride (from fluoridated water) during tooth development, the OH- ion is replaced by the fluoride ion, producing fluorapatite. Fluorapatite is more resistant to acid demineralization than is hydroxyapatite. It has also been determined that teeth developed in the presence of fluoride (with fluorapatite formed) have more well-coalesced grooves on the occlusal surfaces and fewer pits and fissures.

Water Fluoridation For 65 years, community water fluoridation has been a safe and healthy way to effectively prevent tooth decay. Centers for Disease Control has recognized water fluoridation as one of the 10 great public health achievements of the 20th century. Average cost savings ranges from $15.95 per person per year in a small community to $18.62 per person per year in a larger community. Costs to fluoridate average $.95/person/year. 72% of public water supplies are fluoridated; 64% of Americans drink fluoridated water. Kentucky was first state in U.S. to mandate fluoridation of all public water supplies. With advent of use of fluorides in dentifrices. professional applied topical fluorides, and other vehicles the relative reduction is dental caries is now approximately 25%, versus the earlier reduction when fluoridation was the only vehicle.

Supplemental Systemic Fluorides As not all individuals have access to public water supplies and not all public water supplies are fluoridated, fluoride tablets were developed for ingestion by children during the period of tooth formation. While use of supplemental fluorides was popular for several years, they are fairly infrequently used today. The research has not been consistent as to their effectiveness. Additionally, dosage was difficult to control as allowances had to be made for the amount of naturally occurring fluoride existing in in the child’s water supply. This required collecting water and having the fluoride content assessed by a laboratory. Compliance with children taking the tablets was also a significant problem. Compliance has been demonstrated to be improved when combined with children’s vitamins. Individual sodium fluoride tablets in varying concentrations are still available by prescription, as are children’s vitamins with fluoride. Typical concentrations are 0.25 – 1.0 mg. A number of countries internationally add fluoride to their salt rather than to their water. Has been demonstrated to be effective.

Mechanism of Fluoride Action Early work on water fluoridation led to the assumption that it was the incorporation of the fluoride ion into the hydroxyapatite crystalline structure during tooth development that imparted caries resistance. More recent work indicates that this is probably not the case. Rather, caries reduction is more related to the post-eruptive topical effect of the fluoride rather than the pre-eruptive systemic developmental effect on tooth development. Fluoride in saliva (and in plaque) inhibits the demineralization of sound enamel and enhances the remineralization of demineralized enamel. The fluoride is taken up by the demineralized enamel along with calcium and phosphate to establish an improved enamel crystalline structure.

Topical Fluoride Therapeutics Interestingly, the early studies of water fluoridation found that the anterior teeth had a greater reduction in caries than did the posterior teeth. This led to speculation that there was a topical effect, as the water being drunk came into more intimate contact with the anterior teeth versus the posterior. Thus the therapeutic approach to using fluorides topically emerged, and with that fluoride dentifrices, professional applied high potency topical fluorides, and fluoride mouth rinses.

Professionally Applied High Potency Topical Fluorides High potency topical fluorides for professional application are compounded differently, with different strengths, and available in a variety of vehicles for application: 2% Sodium Fluoride (0.9% fluoride; 9,000 ppm) in gel or foam. Acidulated Phosphate Fluoride (1.23%; 12,300 ppm) in gel or foam. 5% Sodium Fluoride as a varnish (2.26% fluoride; 22,600 ppm)

Acidulated Phosphate Topical Fluorides Early studies reported that fluoride uptake by enamel increased in an acidic environment. APF fluorides are formulated to be highly acidic with a pH of 3.0. Teeth should be dry prior to application If liquid or gel used, it must be flossed between contacts. If foam used in a tray, it is assumed that the pressure of the tray will force the fluoride into the contact areas. (Questionable) Post-treatment instructions include not eating or drinking anything for 30 minutes.

Fluoride Varnish

Fluoride Varnish Fluoride varnish was developed and began to be used in Europe in the 1970s. It was introduced in the United States in the 1990s and is becoming the most popular high potency topical fluoride used by dentists. It is only approved for desensitizing exposure root surfaces; therefore is used “off label.” It has the advantages of: high concentration of fluoride in small volume of material; held in close contact with the teeth for extended period of time; ease of application; and non-offensive taste. The only brand of varnish that has been studied for efficacy is Duraphat by Colgate. Other brands are presumed to be effective as of similar content. Duraphat has the disadvantage of leaving the teeth with a yellowish-brown stain for a short time following application. Competitive brands are clear or white and do not have this disadvantage, thus enhancing their market popularity. Post-treatment instructions for fluoride varnish include not brushing the teeth until the next day.

Clinical Considerations in High Potency Topical Fluorides Topical fluorides must be used regularly and repeatedly to be effective. The decision of the use of fluorides as a caries preventive agent must always we based on a caries risk assessment of the child. Teeth must be dry on application. Topical fluorides are not cost effective in children at low risk for dental caries, therefore should be used on children at moderate or high risk for dental caries. Specifically, not in areas of water fluoridation. Topical fluorides have relatively little preventive impact on pit and fissure lesions; reason sealants necessary. Primary effect is on smooth surfaces. Caries on smooth surfaces is most frequently on the proximal surfaces. Therefore, the fluoride must be flossed into the inter-proximals of teeth to gain the caries preventive effect of topical fluorides.. While varnishes adhere to the teeth for an extended period, gels and foams do not, and therefore must be applied and remain on dry teeth for a full four minutes. (One company markets a one minute foam—this has never been demonstrated to be effective.)

Fluoride Toothpaste Brushing with fluoride toothpaste increases fluoride concentration in saliva by 100-1,000 fold; returning to baseline in 1-2 hours. Children older than six years of age can retain more fluoride in their saliva by not rinsing after brushing. (Younger children should not do this as will swallow the toothpaste with potential for fluorosis.) Concentration of fluoride in fluoride toothpaste is 1,000-1,500 ppm Regular used of fluoride toothpaste reduces caries experience by 15-30%. Fluoride toothpaste accounts for 90% of toothpaste market in the United States.

Fluoride Toothpaste Young children, less than 6 years old, are at risk for fluorosis as a result of a tendency to swallow toothpaste. Parents are advised to only place a “pea-sized” amount of toothpaste on the child’s toothbrush. Prevalence of fluorosis in the U.S, is 22-23% of children.

Prevident Dentrifice Prevident is a high concentration fluoride dentrifice (1.1% sodium fluoride), by Colgate. Available by prescription only. Indicated for children over age 6 who have are at high risk for dental caries.

Fluoride Mouthrinses Most common ingredient is sodium fluoride; typically at 0.05% concentration. Again, due to the potential for fluorosis, not recommended for children under age 6. Average caries reduction with daily use in non-fluoridated community approximately 30%. Indicated for children with moderate to high caries experience, especially if they live in a non-fluoridated community. Brands include: ACT, Duraphat Rinse FluoriGard, and Fluorinse