Elsevier

Indian Journal of Dentistry

Volume 4, Issue 4, December 2013, Pages 207-210
Indian Journal of Dentistry

Review Article
Biomarkers of fluoride exposure in human body

https://doi.org/10.1016/j.ijd.2013.05.002Get rights and content

Abstract

Fluoride is often called as a “Double-edged sword”, as inadequate ingestion is associated with dental caries and excessive consumption of fluorides in various forms leads to some deleterious effects on different tissues of the body such as teeth, bone and soft tissues. Due to the changing patterns of systemic fluoride exposure, there is an increase in the prevalence and severity of dental fluorosis. Therefore, it is extremely important to monitor the intake of fluoride in order to help scientists and policymakers to make better informed decisions about the best ways to balance dental caries prevention versus dental fluorosis risk. This can be done by monitoring level of various biomarkers available in human body. Biomarker is defined as “an indicator of change in biological system that could lead to a clinical disease”. The World Health Organization has stated that “a fluoride biomarker is of value primarily for identifying and monitoring deficient or excessive intakes of biologically available fluoride”. Fluoride biomarkers can be classified under the categories: contemporary (urine, plasma and saliva), recent (nails and hair) and historic markers (bone and teeth). These biomarkers can also serve as a tool to assess the impact of water fluoridation on bone quality and other physiological conditions. This literature review is presented with an objective to discuss various aspects of different biomarkers of fluoride exposure in human body and their significance in research, human health and dental health services.

Introduction

Fluoride is a natural component of the biosphere, the 13th most abundant element in the earth's crust, among its characteristics, F has a high affinity for mineralized tissues, which means it can be found in teeth and bone.1 Use of fluorides has formed the backbone of our fight against dental caries for more than 50 years now, this has lead to addition of fluoride into water, milk, salt and diet so as to provide its optimum amount to the general population, but, there is other face of fluoride which is seen when it is ingested in more than optimal concentration thereby leading to chronic toxicities like dental and skeletal fluorosis.

Dental fluorosis can occur when greater than optimal fluoride is ingested during critical periods of tooth enamel formation. This exposure can be either short term and coincide with amelogenesis or chronic, which encompasses a larger window of opportunity. It is a disturbance primarily affecting enamel during formation, but can also affect dentin. Microscopically, fluorotic enamel shows a subsurface porosity, whereas the clinical appearance varies from slight white lines to irregular cloudy areas. With increasing severity, the white areas merge, and loss of the enamel may occur. Skeletal fluorosis is a more serious condition compared to dental fluorosis. The most common feature of skeletal fluorosis is the irregular thickening of the bones in the central skeleton, due to periosteal sleeves of abnormally structured osseous tissue, osteophytosis, mineralization of tendons and muscle attachments, and bridging between the edges of the vertebral bodies. In skeletal fluorosis, fluoride is ingested during periods of bone modeling (growth) and/or remodeling.2

The balance between exposure to fluoride and the decrease in dental caries prevalence, concomitant with the increase in dental fluorosis prevalence, has been extensively documented. At 1 ppm concentration in water it can help to reduce caries inceidence in a population upto 50% with no clinically significant level of fluorosis seen.3, 4 The determination of ingestion levels of fluoride, however, is becoming increasingly difficult, since fluoride is present in virtually all foods and drinks, as well as in therapeutic agents. Considering that only absorbed fluoride is implicated in dental fluorosis development, assessment of fluoride absorption, instead of fluoride intake, seems to be more accurate.5 In India, occurrence of skeletal and dental fluorosis in endemic geographical areas across the country due to high fluoride content in drinking water is a public health problem. Therefore there is a need to monitor the effects of fluoride on these populations and so that government and other health agencies have the data to take necessary actions in this regard. A major obstacle in the study of fluorosis is the absence of an accurate and practical method for measuring combined fluoride intake, both cross-sectionally and cumulatively. This has led to the search for biomarkers of fluoride exposure in various body tissues i.e. teeth, bone, nail, hair, plasma, urine, saliva.

Section snippets

What are biomarkers?

Biological markers or biomarkers are defined as indicators that signal events in biological systems (human body) or samples. A biomarker is not used as diagnosis test, but as an indicator of a disease or biological alteration. The biomarkers are classified in to three types: 1) exposure; 2) susceptibility and 3) biomarkers of effect. For biomarkers of fluoride the examples would be respectively: 1) plasma, bone, teeth, urine, saliva, dental plaque, plaque fluid, hair, nails; 2) genetic factors,

Contemporary markers

The concentrations in urine, plasma, saliva fluids reflect the fluoride concentrations during the recent hours. Urinary fluoride excretions and concentrations are variable because of variations in urinary flow and pH. Plasma and saliva samples taken from fasting subjects have the best value because the fluoride concentrations in these two fluids are influenced by intake during recent hours.7

Recent markers

The concentrations in hair and nail reflect the average plasma fluoride concentrations over time.

Analytical methods for determination of fluoride in biological materials

The analytical methods help in detecting, measuring, and/or monitoring fluorides. Trace levels of fluoride in biological media are determined primarily by:

1. Potentiometric (ion selective electrode [ISE]) and 2. Gas chromatographic (GC) methods.

Calorimetric methods are available, but are more time consuming and lack the sensitivity of the other methods. Other methods that have been used include fluorometric, enzymatic, and proton activation analysis. The latter technique is sensitive to trace

Discussion

This literature describes the availability of various biomarkers which can used to assess fluoride level in human body. They are mainly teeth, bone, nail, hair, plasma, urine, saliva. Studies have been conducted both in animals and humans to provide evidence regarding accuracy of these biomarkers in determining fluoride exposure. Buzalaf et al5 used urine and nails for the purpose of monitoring fluoride intake, and found that both biomarkers were significantly correlated to total fluoride

Conclusion

Biological markers are identified for different diseases and conditions with hope to provide better estimates of exposure dose specific to individuals and to provide estimates of the relevant exposure dose to target tissues. Biological markers of exposure may be used to improve knowledge of the extent of population exposures to various exogenous agents through surveillance techniques and also participant compliance with treatment regimens in intervention trials.

Different fluoride markers may

Conflicts of interest

The author has none to declare.

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