Teeth with fluorosis have an increase in porosity in the subsurface enamel (“hypomineralization”). The increased porosity of enamel found in fluorosis is a result of a fluoride-induced impairment in the clearance of proteins (amelogenins) from the developing teeth. Despite over 50 years of research, the exact mechanism by which fluoride impairs amelogin removal is not yet fully understood. It is believed, however, that it involves a fluoride-induced toxic effect on the cells (ameloblasts) involved in enamel formation.
In addition to affecting the enamel, dental fluorosis may also affect the underlying dentin as well, thus suggesting that “fluoride may exert effects at the cellular level well beyond tooth development.”
“HYPOMINERALIZATION”: INCREASED POROSITY OF TEETH DUE TO IMPAIRED CLEARANCE OF AMELOGENINS:
“Fluorosis is a hypomineralization of enamel caused by the retention of amelogenin proteins by fluoride. The affected enamel does not mature and has surface and subsurface porosities.”
SOURCE: Allen K, et al. (2004). Using microabrasive material to remove fluorosis stains. Journal of the American Dental Association 135:319-23.
“Dental or enamel fluorosis occurs when excess amounts of fluoride are ingested during tooth development (1-8 years of age). It is characterized by increased porosity (or hypomineralization) of the subsurface enamel and well mineralized surface layer of enamel. Mildly fluorosed enamel is fully functional, but may be cosmetically objectionable. As the severity of dental fluorosis increases, the depth of the enamel involvement and the degree of porosity increases. More severely fluorosed enamel is more porous, pitted, and discolored and is prone to fracture and wear because the well mineralized zone is very fragile to mechanical stress.”
SOURCE: Agency for Toxic Substances & Disease Registry [ATSDR]. (2003). Toxicological profile for Fluorides, Hydrogen Fluoride, and Fluorine. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.
“The observations that the fluorosed enamel retains a relatively high proportion of immature matrix proteins, characterized by high proline contents, support the notion of an incomplete removal of amelogenin proteins under excessive fluoride ingestion during development. Whitford (1997) recently stated that “although several other fluoride-induced effects might be involved in the aetiology of fluorosis, it now appears that inhibition of enzymatic degradation of amelogenins, which may delay their removal from the developing enamel and impair crystal growth, may be of critical importance”.
SOURCE: Aoba T, Fejerskov O. (2002). Dental fluorosis: chemistry and biology. Critical Reviews of Oral Biology and Medicine 13: 155-70.
“Enamel fluorosis results from increased porosity in the formed enamel, probably due to a delay in the removal of amelogenin proteins during enamel formation. The hydrolysis and removal of amelogenin from the enamel matrix is critical for tooth growth and development..”
SOURCE: DenBesten PK, et al. (2002). Effects of fluoride on rat dental enamel matrix proteinases. Archives of Oral Biology 47: 763-770.
“Dental fluorosis is characterized by an increasing porosity (hypomineralization) of the subsurface enamel, causing the enamel to appear opaque. The clinical features include changes ranging from barely discernible fine white lines running across the teeth to entirely chalky white teeth. In advanced stages, the enamel may become so porous that the outer layers break down and the exposed porous subsurface becomes discolored.”
SOURCE: Fomon SJ, et al. (2000). Fluoride intake and prevalence of dental fluorosis: trends in fluoride intake with special attention to infants. Journal of Public Health Dentistry 60: 131-9.
“Fluorosed enamel is characterized by retention of amelogenins in the early-maturation stage of enamel and by the formation of subsurface hypomineralization.”
SOURCE: Sapov K, et al. (1999). A laboratory assessment of enamel hypoplasia of teeth with varying severities of dental fluorosis. Journal of Oral Rehabilitation 26: 672-7.
“Dental fluorosis is defined as a permanent hypomineralization of enamel, characterized by greater surface and subsurface porosity than in normal enamel, that results from excess fluoride (F) reaching the developing tooth during developmental stages… Excess F available to the enamel during maturation disrupts mineralization and results in excessive retention of enamel proteins.”
SOURCE: Burt BA ; Eklund SA. (1999). Dentistry, Dental Practice, and the Community (5th Ed). WB Saunders Co; Philadelphia.
“excessive intake (of fluoride) leads to dental and skeletal fluorosis characterized by hypomineralization of the calcified tissues.”
SOURCE: Milan AM, et al. (1999). Altered phosphorylation of rat dentine phosphoproteins by fluoride in vivo. Calcified Tissue International 64:234-8.
“[T]he hypomineralized regions of fluorosed enamel might be an arrest of enamel maturation… In support of this hypothesis was the finding that human fluorosed enamel, when compared with normal mature enamel, had a similar total protein content, but the fluorosed enamel retained a relatively high proportion of immature matrix proteins.”
SOURCE: Fejerskov O, et al. (1990). The nature and mechanisms of dental fluorosis in man. Journal of Dental Research 69(Spec Iss): 692-700.
“Any use of fluorides, whether systemic or topical, in caries prevention and treatment in children results in ingestion and absorption of fluoride into the blood circulation. The mineralization of teeth under formation may be affected so that dental fluorosis may occur. Dental fluorosis reflects an increasing porosity of the surface and subsurface enamel, causing the enamel to appear opaque. The clinical features represent a continuum of changes ranging from fine white opaque lines running across the tooth on all parts of the enamel to entirely chalky white teeth. In the latter cases, the enamel may be so porous (or hypomineralized) that the outer enamel breaks apart posteruptively and the exposed porous subsurface enamel becomes discolored.”
SOURCE: Fejerskov O, et al. (1990). The nature and mechanisms of dental fluorosis in man. Journal of Dental Research 69(Spec Iss): 692-700.
“Fluorosed enamel is also characterized by a delay in the withdrawal of protein when compared with control enamel.”
SOURCE: Denbesten PK, et al. (1985). Changes in the fluoride-induced modulation of maturation stage ameloblasts of rats. Journal of Dental Research 64: 1365-70 .
“Enamel maturation has been characterized by the progressive deposition of mineral and withdrawal of organic matrix and water. It is evident that high chronic levels of fluoride interferes with this process.”
SOURCE: DenBesten PK, Crenshaw MA. (1984). The effects of chronic high fluoride levels on forming enamel in the rat. Archives of Oral Biology 29:675-9.
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