Fluorides in toothpastes

Representative Method Ion-selective electrodes find application in numerous quantitative analyses, each of which has its own unique considerations. The following procedure for the analysis of fluoride in toothpaste provides an instructive example. 

E.D. Beltran, S.M. Szpunar, Fluoride in toothpastes for children Suggestion for change, Pediatr. Dent. 10 (1988) 185-188. 

F.N. Hattab, Analytical methods for the determination of various forms of fluoride in toothpastes, J. Dent. 17 (1989) 77-83. 

Figure 9.15 The halogens have many varied uses - fluoride in toothpaste to help reduce dental decay, chlorine in household bleach to kill bacteria, bromine as a fire retardant, and iodine in photographic reproduction.

Many toothpastes contain fluoride, which helps to prevent tooth decay. However, some people worry about the long-term effects of fluoride in toothpastes as well as in the water supply. IMAGE COPYRIGHT 2009, AAAU HORNG. USED UNDER LICENSE FROM SHUTTERSTOCK.COM. 

This chapter describes how individuals with severe enamel fluorosis (mottled tooth enamel) became associated with fluoride in the public water supply and protection from dental caries. A comparison of caries experience with the fluoride content of public water supplies and enamel fluorosis in adolescents indicated that 1 pg fluoride/mL (1 part/million) in the water provides caries protection with minimal enamel fluorosis (sect. 1). One mechanism is the spontaneous isomorphic replacement of apatite s hydroxide anions with fluoride, which reduces enamel solubility. A second is fluoride-mediated inhibition of enolase, which retards bacterial acid production at teeth surfaces. These findings led to the use of fluoride in toothpastes, which provides better protection from caries at tooth surfaces than water fluoridation alone (sect. 2). The chapter concludes with a discussion of potentially harmful effects of fluoride ingestion (sect. 3). 

Figure 3.7 Results from the measurement of fluoride in toothpaste. Data 1-9 are replicate measurements. Dashed lines are 95% confidence intervals. The circled datum (number 3) is the suspect outlier. The dotted line is the critical x value calculated from the a = 0.05", n = 9 Grubbs s test. The datum numbered 12 (circled cross) is the reference value of the sample (0.033 m/m%).

Dedicated benchtop NMR analyzers for a variety of applications are available. Broker s Minispec mq series (www.minispec.com) includes an analyzer to determine fluoride in toothpaste quantitatively and another to determine water droplet size distribution in oil/water emulsions. Fluoride is often added to toothpaste as sodium fluoride or sodium monofluorophosphate to prevent tooth decay. The fluorine analyzer can determine fluorine and hydrogen at the level of a few hundred ppm. Toothpaste is squeezed into a glass sample tube and the quantitative determination of fluorine takes less than 1 min. The NMR method uses no solvents or reagents and is independent of the sample color... 

Other analytical techniques have less frequently been used nuclear magnetic resonance spectroscopy (NMR) (e.g., tocopherols in toothpaste by hyphenated LC-NMR), energy dispersive X-ray fluorescence (ED-XRF) (e.g., heavy metals determination), surface enhanced Raman scattering (e.g., determination of 4-aminobenzoic acid or PABA, in sunscreens), neutron activation analysis (e.g., determination of iron and zinc), and thermometric analysis (e.g., fluoride in toothpaste). 

The NHP Regulations apply to a number of personal care products such as toothpaste, antiperspirants, and sunscreens. The presence of an active that is an inorganic substance in a nonprescription topical drug that also falls under the definition of a cosmetic, e.g., sodium fluoride in toothpaste would make the product an NHP regardless of natural or synthetic duplicate status of the sodium fluoride. The regulations designate certain products as natural but do not provide the rationale for doing so. 

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