Dental fluorosis associated with hereditary diabetes insipidus

The molecular basis of hereditary enamel defects in humans

The formation of human enamel is highly regulated at the molecular level and involves thousands of genes. Requisites for development of this highly mineralized tissue include cell differentiation; production of a unique extracellular matrix; processing of the extracellular matrix; altering of cell function during different stages of enamel formation; cell movement and attachment; regulation of ion and protein movement; and regulation of hydration, pH, and other conditions of the microenvironment, to name just a few. Not surprising, there is a plethora of hereditary conditions with an enamel phenotype. The objective of this review was to identify the hereditary conditions listed on Online Mendelian Inheritance in Man (OMIM) that have an associated enamel phenotype and whether a causative gene has been identified. The OMIM database was searched with the terms amelogenesis, enamel, dental, and tooth, and all results were screened by 2 individuals to determine if an enamel phenotype was identified. Gene and gene product function was reviewed on OMIM and from publications identified in PubMed. The search strategy revealed 91 conditions listed in OMIM as having an enamel phenotype, and of those, 71 have a known molecular etiology or linked genetic loci. The purported protein function of those conditions with a known genetic basis included enzymes, regulatory proteins, extracellular matrix proteins, transcription factors, and transmembrane proteins. The most common enamel phenotype was a deficient amount of enamel, or enamel hypoplasia, with hypomineralization defects being reported less frequently. Knowing these molecular defects allows an initial cataloging of molecular pathways that lead to hereditary enamel defects in humans. This knowledge provides insight into the diverse molecular pathways involved in enamel formation and can be useful when searching for the genetic etiology of hereditary conditions that involve enamel.

Full mouth rehabilitation in a medically compromised patient with fluorosis

Severely worn out dentition needs to be given definite attention as it not only affects aesthetics but can also cause psychological distress to the affected individual. It can cause chewing difficulty, temporomandibular joint problems, headaches, pain and facial collapse. Before any attempt to restore severely worn dentition, aetiology of excessive tooth wear should be established. Severe wear can result from chemical cause, mechanical cause or a combination of various causes. Dental fluorosis can also result in severe wear of teeth. Teeth sometimes become extremely porous and friable with a mottled appearance ranging from yellow to brown-black. There occurs loss of tooth substance and anatomic dental deformities resulting in un-aesthetic dentition requiring full mouth rehabilitation. Here a similar case of full mouth rehabilitation of severely worn dentition due to dental fluorosis in a 27-year-old patient is presented. This case report conjointly presents the uncommon association of diabetes insipidus with dental fluorosis. Diabetes insipidus through its characteristic symptom of polydipsia can result in intake of more than permitted dose of fluoride thus causing dental fluorosis. In literature only few cases have been reported of dental fluorosis in association of diabetes insipidus. Full mouth rehabilitation of the patient was successfully accomplished through well-planned systematic approach to simultaneously fulfill aesthetic, occlusal and functional parameters.

Fluoride: benefits and risks of exposure

This summarizes current knowledge of the benefits and risks of fluoride ingestion. The preponderance of evidence indicates that fluoride can reduce the incidence of dental caries and that fluoridation of drinking water can provide such protection. Due to the ubiquitous nature of exposures to fluoride sources other than drinking water, it is currently impossible to draw firm conclusions regarding the independent effect of fluoride in drinking water on caries prevalence using an ecologic study design. Moderate dental fluorosis occurs in 1 to 2% of the population exposed to fluoride at 1 mg/l in drinking water and in about 10% of the population at 2 mg/l; moderate/severe fluorosis occurs in variable percentages ranging up to 33% of the population exposed to fluoride at 2.4 to 4.1 mg/l in drinking water. The issue of whether moderate or severe dental fluorosis represents an adverse health effect is still controversial. There is no evidence of skeletal fluorosis among the general U.S. population exposed to drinking water fluoride concentrations lower than 4 mg/l. Radiographically detected osteosclerosis after chronic exposure to fluoride in drinking water at 8 mg/l was not associated with clinical symptoms. Reports of crippling skeletal fluorosis associated with low concentrations of fluoride in drinking water in tropical countries have been attributed to other dietary factors. The available data suggest that some individuals may experience hypersensitivity to fluoride-containing agents. Further studies on hypersensitivity are required. There is no evidence of increased incidence of renal disease or renal dysfunction in humans exposed to up to 8 mg fluoride per liter in drinking water. Structural changes in kidneys of experimental animals have been detected at doses exceeding 1 to 5 mg fluoride per kilogram per day. Based on four case reports, individuals with renal insufficiency who consume large volumes of naturally fluoridated water at 2 to 8 mg/l are possibly at increased risk of developing skeletal fluorosis. Studies on the effects of fluoride in individuals with renal insufficiency are needed. There is no evidence that chronic exposure to concentrations of fluoride reported to be greater than 2 mg/l in drinking water increases human cancer mortality or incidence. A study of lifetime exposure to fluoride on cancer incidence in rats and mice has been completed, but assessment for cancer has not been completed. There is no evidence that fluoride is genotoxic except in some in vitro assays at cytotoxic concentrations. There is no in vivo evidence that fluoride affects human cellular enzyme activities.(ABSTRACT TRUNCATED AT 400 WORDS)

Environmental and physiological factors affecting dental fluorosis

In addition to differences in fluoride intake and possibly to calcium deficiency or malnutrition, there are several factors which may account for individual differences in the occurrence of dental fluorosis. Disorders in acid-base balance affect the renal handling of fluoride such that, in acidosis, the excretion rate is diminished and, in alkalosis, the excretion rate is enhanced. Thus, any factor that can decrease urinary pH would be expected to increase the likelihood of dental fluorosis and vice versa. Results from studies with both rats and dogs have shown that acid-base disturbances per se, especially acidosis, adversely affect the mineralization of enamel in a manner that resembles fluorosis. It has been found that the retention and tissue levels of fluoride are increased by residence at high altitude. It has also been found that, in the absence of fluoride exposure, residence at high altitude per se can have a profound disruptive effect on amelogenesis which could be confused with fluorosis. The effects of diseases which lead to increases in urinary flow rate and water intake on the likelihood of the occurrence of dental fluorosis are also discussed.