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1.
Introduction
Dental fluorosis is an enamel defect caused by the excessive intake of fluoride during enamel formation. In deciduous teeth, it occurs during the embryonic phase, while in permanent teeth, it occurs primarily in children aged 2–8 years old (1–4). The primary sources of fluoride intake are from food and water, as well as from toothpaste, which contains added fluoride. Fluoride is also being added to different materials, including fluoride varnish, fluoride foam and dental resin to prevent the occurrence of dental caries. All these methods increase the morbidity of dental fluorosis (1). The incidence of dental fluorosis is currently a problem worldwide, although the prevalence of dental fluorosis varies in different countries. In the USA, ~25% of the population have dental fluorosis and its incidence is also high in China, ~11.7% of adolescents of 12 years old suffer dental fluorosis (2,4). According to the Dean's index, dental fluorosis may be classified into five types: Questionable, very mild, mild, moderate and severe (5). In clinical practice, dental fluorosis may be classified into three types: Chalk, discoloration and defective (6).
Enamel formation by ameloblasts is a complex process. The primary elements of enamel hydroxyapatite are present in the crystalline form (7,8). It has been demonstrated that 8–14 H+ are released in the extracellular environment as the minimum repeating structure of hydroxyapatite crystals are formed, thus lowering the pH (7–9). To maintain the pH balance, ameloblasts must buffer the protons. During the secretory stage, amelogenins may serve an important role in buffering the pH (9,10); however, during the maturation stage, ameloblasts secrete bicarbonate into the enamel matrix to neutralize the microenvironment (7,9–11). The process of enamel formation requires strict control of extracellular pH (7–9,11); hydroxyapatite crystal growth and proteinase activity in the extracellular space are pH-dependent phenomena (7,8,12). pH therefore serves an important role during amelogenesis, which is the basis of enamel formation.
The current review discusses the regulation of pH during amelogenesis in dental fluorosis and also explores the effects of changes in ion transporters on dental fluorosis. This may identify future directions of research to identify potential novel treatments of dental fluorosis.
2.Mechanism of dental fluorosis
There are multiple potential causes of dental fluorosis; however, the precise mechanism by which dental fluorosis...