Topical fluorides: a discussion of risks and benefits

An In Vitro Investigation of Anticaries Efficacy of Fluoride Varnishes

Most currently marketed fluoride varnishes (FVs) have not been evaluated for their effectiveness in preventing dental caries. The objective of this study was to investigate the anticaries efficacy, measured as fluoride release into artificial saliva (AS); change in surface microhardness of early enamel caries lesions; and enamel fluoride uptake (EFU) of 14 commercially available FVs and two control groups. Bovine enamel specimens (5×5 mm) were prepared and assigned to 18 groups (n=12). Early caries lesions were created in the specimens and characterized using Vickers microhardness (VHN_lesion). FV was applied to each group of specimens. Immediately afterward, specimens were incubated in 4 mL of AS for 18 hours, which were collected and renewed every hour for the first six hours. AS samples were analyzed for fluoride using an ion-specific electrode. Specimens were then brushed for 20 seconds with toothpaste slurry and subjected to pH cycling consisting of a four-hour/day acid challenge and one-minute treatments with 1100 ppm F dentifrice for five days. Microhardness was measured following pH cycling (VHN_post). EFU was determined using microbiopsy. Acid resistance (eight-hour demin challenge) was performed after pH cycling, and microhardness was measured (VHN_art) and compared with baseline values to test the FV impact after pH cycling. One-way analysis of variance was used for data analysis (α=0.05). FVs differed in their release characteristics (mean ± SD ranged from 14.97 ± 2.38 μg/mL to 0.50 ± 0.15 μg/mL), rehardening capability (mean ± SD ranged from 24.3 ± 15.1 to 11.7 ± 12.7), and ability to deliver fluoride to demineralized lesions (mean ± SD ranged from 3303 ± 789 μg/cm³ to 707 ± 238 μg/cm³). Statistically significant but weak linear associations were found between ΔVHN_{(post - lesion)}, EFU, and fluoride release (correlations 0.21-0.36). The results of this study demonstrated that differences in FV composition can affect their efficacy in in vitro conditions.

Prevention. Part 7: professionally applied topical fluorides for caries prevention

This paper reviews the use of professionally applied topical fluorides (PATF) in caries prevention. PATFs are indicated for children and adults with one or more decayed smooth surfaces and/or those who are at high caries risk. Frequency of administration depends on the patient's caries risk, and is usually every 6 months. The effectiveness of fluoride varnish and gel applications has been well established in caries prevention trials involving permanent teeth. Although both types are effective, varnish may be preferred because it is easier to apply, reduces the risk of fluoride over-ingestion, and has greater patient acceptance. Fluoride foams are similar products to gels, but have not been tested clinically. The use of in-office two-part rinses is not recommended because they have not been proven effective. A cleaning, or prophylaxis, is not necessary before the application of topical fluoride for caries prevention. In conclusion, when used appropriately, PATFs are a safe, effective means of reducing caries risk among high-risk populations.

Fluoride exposure and dental fluorosis in Newburgh and Kingston, New York: policy implications

OBJECTIVES

This analysis was conducted to determine the changes in the effect of exposure to fluoridation and other sources of fluoride on dental fluorosis in children attending Newburgh and Kingston school districts in New York State.

METHODS

Data for this analysis were obtained from two surveys conducted in the 1986 and 1995 school years. Analyses were limited to 3500, 7-14-year-old lifelong residents of a fluoridated or a nonfluoridated community. Dean's classification and DMFS index were used for recording dental fluorosis and caries, respectively. A questionnaire was used to collect fluoride exposure data. Regression procedures were used to estimate the effect of fluoridation, fluoride supplements, and brushing before the age of 2 years on dental fluorosis.

RESULTS

Children examined in 1996 were at higher risk for both questionable and very mild to severe dental fluorosis if they received fluoride from water or daily tablet use, or started brushing before the age of 2 years. The increase in risk from 1986 to 1995 was greater for African-American children.

CONCLUSION

This analysis showed that the risk of developing dental fluorosis did not decline over time in these communities. Continuous exposure to water fluoridation had an observable effect on dental fluorosis. However, implementation of fluoridation in Newburgh Town did not result in an increase in dental fluorosis prevalence.

Changes in dental fluorosis and dental caries in Newburgh and Kingston, New York

OBJECTIVES

This study sought to determine whether the prevalence of dental fluorosis and dental caries had changed in a fluoridated community and a nonfluoridated community since an earlier study conducted in 1986.

METHODS

Dental fluorosis and dental caries data were collected on 7- to 14-year-old lifelong residents (n = 1493) of Newburgh and Kingston, NY.

RESULTS

Estimated dental fluorosis prevalence rates were 19.6% in Newburgh and 11.7% in Kingston. The greatest disparity in caries scores was observed between poor and nonpoor children in nonfluoridated Kingston.

CONCLUSIONS

The prevalence of dental fluorosis has not declined in Newburgh and Kingston, whereas the prevalence of dental caries has continued to decline.

[Dental caries prevention with semestral topical administration of acidulated phosphate fluoride]

998 children aged 6, 8 and 10, from low income families living in the Federal District, Brazil and attending public, first grade, schools, received bi-annual topical APF Gel-Tray applications. The mass methodology proposed by the National Dental Caries Preventive Program of the Brazilian Ministry of Health, without previous prophylaxis, was adopted. After one year, in fluoridated communities the reduction in the incidence of CPOS was of 31.6%, 24.9% and 39.5%, respectively, for the groups aged 6, 8 and 10. In non fluoridated communities the reductions were, respectively, of 24.3%, 26.6% and 27.7%, in every case with statistic significance at the 95% confidence level. Considering the positive results in a developing area, it is recommended that oral health institutions at all levels could adopt a comprehensive and continuous preventive program for children under their responsibility.

Gingivitis/stomatitis in cats

Any alteration in the balance of bacterial challenge versus the host's ability to resist and repair will result in oral lesions that are similar in appearance. The bacterial cause of gingivitis and periodontitis in humans and in all other animals in which it has been studied is firmly established, and specific species of predominantly gram-negative anaerobes have been implicated. Naturally occurring or acquired immunopathologies are likely to result in premature dental disease. When oral disease is associated with the accumulation of plaque, a positive response can be achieved by reducing the bacterial challenge to the host through the maintenance of oral hygiene by timely professional dental prophylaxis and home care. Disease that is the result of atypical immune responses, however, can be much more difficult to manage. Such oral disease can occur with either immune deficiencies or exaggerated immune responses, and it is likely that multiple mechanisms are active concurrently. In any case, gram-negative anaerobes present in plaque are likely to be a major contributing factor. Therefore patients with chronic refractory gingivitis-stomatitis must be considered to be plaque intolerant. Only with a frequent regimen of aggressive and thorough professional dental treatment plus meticulous oral home care on a daily basis can one expect to keep these cases in remission. Because this is often unrealistic, the only other way to keep these patients free of disease is by total dental extraction. The tissues that are colonized by the causative organisms must be eliminated. All root tips and bony sequestra must be removed and healing with intact epithelium accomplished before these cases will go into remission. Edentulous feline patients that continue to have signs of gingivostomatitis have been found to have an area of nonhealed bony sequestrum and chronic osteomyelitis. Once effective debridement has been accomplished and epithelial healing completed, nonresponsive cases can be expected to go into remission (Color Plate 2, Figure 7). It is hoped that as more is learned about this frustrating problem, the many factors influencing feline oral disease will be scientifically documented. In the future, actual diagnoses can be systematically made early on in disease, and treatment will be more than just symptomatic.

A critique of topical fluoride methods (dentifrices, mouthrinses, operator-, and self-applied gels) in an era of decreased caries and increased fluorosis prevalence

Within the last 20 years there has been a decrease in the caries prevalence of US schoolchildren, a change in the intraoral caries pattern, and a slowing of the progress of lesions. Simultaneously, the prevalence of enamel milder, cosmetically acceptable forms and is more noticeable in fluoride-deficient communities than those with optimal or above-optimal water fluoride concentrations. Circumstantial evidence indicates that a principal contributor to the caries decline is the extensive use of fluoride dentifrices. Conversely, although use of a fluoride dentifrice can add to the total daily amount of ingested fluoride in preschool children, there is little evidence to suggest that dentifrice ingestion is a principal factor causing the fluorosis increase. The value of fluoride methods may be assessed in relative or absolute terms. The relative, or percentage, caries reduction attributed to fluoride mouthrinses and gels appears to be a property intrinsic to the methods themselves and generally is little affected by the caries activity of the population being treated. Conversely, the absolute, or numerical, caries reduction is dependent upon the level of disease in the population. Thus, the reported caries decline reduces the number of surfaces prevented from developing caries, even though the percentage reduction remains substantially unchanged. Although inadvertent ingestion of fluoride can result from the use of mouthrinses and gels, there is little evidence to suggest that they have contributed to the fluorosis increase. When using topical methods, prudence should prevail to avoid ingestion of fluoride. Fluoride dentifrices should continue to be used routinely, and although lower potency dentifrices may be considered, the literature does not provide strong support for their need. Use of fluoride mouthrinses and gels for individual patients should be predicted upon their caries activity or risk. Use of these methods in public health programs is a matter of cost-effectiveness, which will be influenced by the caries prevalence of the target population.

An evaluation of the use of professional (operator-applied) topical fluorides

Application of fluoride solutions, gels, varnishes, and prophylaxis pastes is reviewed as well as the sequential APF/SnF2 office-rinse method. The most widely-used technique is with 1.23% APF gel (12,300 ppm F) in trays. Clinical results from this method are similar to those achieved with an APF solution of the same fluoride concentration. A professional APF gel/tray application need not be preceded by a prophylaxis, should last four min, and should not be followed by a water rinse for 30 min. Fluoride varnishes are newer topical fluoride agents, but their relative efficacy, compared with other proven caries-inhibitory methods, remains to be fully determined. In general, fluoride prophylaxis pastes have not been shown to inhibit caries; however, their use is justified by the ability of some to replenish fluoride lost from the abrasive action of the paste on tooth enamel. The sequential office-rinse method has not been tested in randomized clinical trials, and its use cannot be recommended.

Relationship of total fluoride intake to beneficial effects and enamel fluorosis

Recent studies indicate that the prevalence of very mild to moderate dental fluorosis, as classified by Dean, has increased relative to that found in earlier investigations. To date, fluoridated water, fluoride supplements, the diet, fluoride dentifrices, and other topical fluoride applications have been identified as sources of systemic fluoride. Recent evidence suggests that there is a strong association between mild to moderate enamel fluorosis and the use of fluoride supplements during early childhood, and that the presently recommended supplementation schedule for U.S. children above the age of 2 years may be too high. Evidence also suggests that there is a strong association between fluoride dentifrice use during early childhood and enamel fluorosis in fluoridated populations. These findings support the need for a careful review of existing supplementation schedules and early oral hygiene practices. There is a pressing need for additional analytical epidemiological studies to confirm existing findings and to determine whether other fluoride sources may be associated with enamel fluorosis. Further, since exposure to combinations of individual risk factors has been shown to carry more than merely an additive increase in the risk of fluorosis, these studies must be multifactorial in design. There is also a need for more fluorosis prevalence and severity data to be gathered, so that the development of enamel fluorosis as a public health problem can be assessed, and so that the success of measures implemented to maximize efficacy while minimizing unwanted side-effects can be monitored.

Critical evaluation of the composition and use of topical fluorides

This report reviews the current status of various topical fluoride systems commonly used for caries prevention; these systems include professional fluoride applications, prophylaxis pastes, varnishes, rinses, gels, and dentifrices. Although the cariostatic benefits of professional applications are well-established from early studies, the magnitude of benefit relative to other preventive measures needs to be re-assessed under current conditions. Significant cariostatic benefits from fluoride prophylaxis pastes remain to be established, as does the relative efficacy of fluoride varnishes in comparison with other fluoride measures. The established cariostatic activity of fluoride rinses with supervised usage needs confirmation under normal home usage conditions. There is inadequate evidence to justify either increasing or decreasing the concentration of fluoride in conventional dentifrices whose efficacy is well-established. Based on limited clinical data and supportive laboratory data, fluoride appears to be effective for preventing root-surface caries.

The distribution of fluoride of prenatal origin in the rat--a pilot study

Sixteen female, Sprague-Dawley rats were divided into four equal groups. Two groups served as controls receiving low or regular concentrations of fluoride (F); animals in the other two groups were given drinking water, containing 100 parts/10(6) F, for 3 weeks either during or immediately before pregnancy. Thirteen days after delivery, the pups and dams were killed and various tissues analysed for F content. Prenatal F supplementation increased F concentrations in plasma, mandibular incisors and femoral epiphyses of pups by 25, 36 and 38% respectively, when given during pregnancy. Only a slight increase of 9 and 11% in the respective F concentrations of incisors and epiphyses occurred when the supplement was given before pregnancy. The fluoride level of milk was consistently higher than that of the maternal plasma. These results suggest the need for further study of prenatal F supplementation.

Effects of a sodium fluoride solution and a varnish with different fluoride concentrations on enamel remineralization in vitro

To study the efficacy of sodium fluoride varnishes and a NaF solution in remineralization of enamel, 120 slabs of non-carious human enamel enamel were presoftened for 6 h and randomly divided into six groups. The slabs were stored in synthetic saliva for 9 days, except for a daily 30-min immersion in 0.1 M lactic acid-NaOH buffer. During the 9-day period, one group of the slabs received no treatment, and the rest were treated once or three times with 2.3% or 1.1% sodium fluoride varnish Duraphat, or nine times with a 0.1% NaF solution. Finally, the slabs were demineralized for 1 h, and the amount of dissolved Ca and F was determined. Microhardness of enamel was determined initially, after presoftening, after the 9-day period, and after the 1-h demineralization. All fluoride treatments prevented enamel softening almost completely during the 9 days, but the control slabs softened markedly. Fluoride varnishes were more effective than NaF solution. Three applications of 2.3% Duraphat were slightly more effective than any of the other varnish treatments, but one treatment with 2.3% varnish was not more effective than treatments with 1.1% varnish. Enamel treated three times with 1.1% varnish showed the greatest acid resistance during the 1-h demineralization. The results suggest that the efficacy of the varnish was not proportional to the fluoride concentration but rather to the number of applications. Fluoride uptake by enamel was greatest with the most concentrated varnish. Enamel solubility was not, however, directly proportional to the fluoride content of enamel.

Longitudinal study of the caries susceptibility of occlusal and proximal surfaces of first permanent molars

Ten- to 13-year-old children were examined annually for three years to determine the caries activity in the proximal and occlusal surfaces of first permanent molars. Almost every tooth with an unsound (carious or filled) proximal surface also had an unsound occlusal surface. Caries scores in proximal surfaces remained relatively constant and low. The percentage of teeth with occlusal caries or fillings increased throughout the study, even though the teeth had been erupted for seven to ten years by the end of the study. Within the age range studied, the time that teeth were in the mouth had little effect on the vulnerability of occlusal surfaces to caries attack.