Reduced Protein Expression of the Na+/Ca2++K+-Exchanger (SLC24A4) in Apical Plasma Membranes of Maturation Ameloblasts of Fluorotic Mice

Exposure of forming enamel to fluoride results into formation of hypomineralized enamel. We tested whether enamel hypomineralization was caused by lower expression of the NCKX4/SLC24A4 Ca2+-transporter by ameloblasts. Three commercial antibodies against NCKX4 were tested on enamel organs of wild-type and Nckx4-null mice, one of which (a mouse monoclonal) was specific. This antibody gave a prominent staining of the apical plasma membranes of maturation ameloblasts, starting at early maturation. The layer of immuno-positive ameloblasts contained narrow gaps without immunostaining or with reduced staining. In fluorotic mouse incisors, the quantity of NCKX4 protein in ameloblasts as assessed by western blotting was not different from that in non-fluorotic ameloblasts. However, immunostaining of the apical plasma membranes of fluorotic ameloblasts was strongly reduced or absent suggesting that trafficking of NCKX4 to the apical membrane was strongly reduced. Exposure to fluoride may reduce NCKX4-mediated transport of Ca2+ by maturation stage ameloblasts which delays ameloblast modulation and reduces enamel mineralization

The effect of fluoride on enamel and dentin formation in the uremic rat incisor

Renal impairment in children is associated with tooth defects that include enamel pitting and hypoplasia. However, the specific effects of uremia on tooth formation are not known. In this study, we used rat mandibular incisors, which continuously erupt and contain all stages of tooth formation, to characterize the effects of uremia on tooth formation. We also tested the hypothesis that uremia aggravates the fluoride (F)-induced changes in developing teeth. Rats were subjected to a two-stage 5/6 nephrectomy or sham operation and then exposed to 0 (control) or 50 ppm NaF in drinking water for 14 days. The effects of these treatments on food intake, body growth rate, and biochemical serum parameters for renal function and calcium metabolism were monitored. Nephrectomy reduced food intake and weight gain. Intake of F by nephrectomized rats increased plasma F levels twofold and further decreased food intake and body weight gain. Uremia affected formation of dentin and enamel and was more extensive than the effect of F alone. Uremia also significantly increased predentin width and induced deposition of large amounts of osteodentin-like matrix-containing cells in the pulp chamber. In enamel formation, the cells most sensitive to uremia were the transitional-stage ameloblasts. These data demonstrate that intake of F by rats with reduced renal function impairs F clearance from the plasma and aggravates the already negative effects of uremia on incisor tooth development

Enamel Pits in Hamster Molars, Formed by a Single High Fluoride Dose, Are Associated with a Perturbation of Transitional Stage Ameloblasts

Excessive intake of fluoride (F) by young children results in formation of enamel subsurface porosities and pits, called enamel fluorosis. In this study, we used a single high dose of fluoride administered to hamster pups, to determine the stage of ameloblasts most affected by fluoride, and whether pit formation was related to F-related sub-ameloblastic cyst formation. Hamster pups received a single subcutaneous injection of either 20 mg or 40 mg NaF/kg body weights, were sacrificed 24 h later, and the number of cysts formed in the first molars counted. Other pups were sacrificed 8 days after F-injection when the first molars had just erupted, to score for enamel defects. All F-injected pups formed enamel defects in the upper half of the cusps in a dose-dependent way. After injection of 20 mg NaF/kg an average of 2.2 white spots per molar was found but no pits. At 40 mg NaF/kg, almost 4.5 spots per molar were counted as well as 2 pits per molar. The defects in erupted enamel were located in the upper half of the cusps, sites where cysts had formed at the transition stage of ameloblast differentiation. These results suggest that transitional ameloblasts, located between secretory and maturation stage ameloblasts, are most sensitive to the effects of a single high dose of fluoride. Fluoride- induced cysts formed earlier at the pre-secretory stage were not correlated to either white spots or enamel pits, suggesting that damaged ameloblasts overlying a fluoride induced cyst regenerate and continue to form enamel

Transport Functions of Ectoderm Epithelial Cells Forming Dental Enamel

Chapter 11. Transport Functions of Ectoderm Epithelial Cells Forming Dental Enamel Michael L. Paine, Alan Boyde, and Rodrigo S. Lacruz Abstract:The development of enamel encapsulates fundamental cellular processes associated with ...

Immunohistochemical Characterization of Rapid Dentin Formation Induced by Enamel Matrix Derivative

The purpose of this study was to examine the pulpal expression of dentin-related proteins during enamel matrix derivative (EMD)–induced reparative dentin formation in a pulpotomy model in pig incisors. Pulpotomies were performed on 72 lower incisors in 24 adult miniature swine. The exposed pulp tissue was treated with EMD or covered with a calcium hydroxide paste (Dycal ® ). At predefined time-points, ranging from 4 days to 12 weeks, experimental teeth were extracted and examined by use of light microscopy, and expression of dentin-related proteins in the pulps was investigated by immunohistochemistry, using antibodies against type I collagen, dentin sialoprotein (DSP), sheathlin, and EMD. In all EMD-treated teeth a substantial amount of reparative dentin formation was observed. The amount of reparative dentin in calcium hydroxide–treated teeth was significantly smaller than in EMD-treated teeth ( P < 0.005) and was less effective in bridging the pulpal wounds. Immunohistochemistry demonstrated that enamel matrix proteins were present in detectable amounts at the application site for about 4 weeks. Moreover, the expression of proteins related to dentin formation in the wounded pulp tissue was about 2 weeks advanced in EMD-treated teeth. These findings demonstrate that enamel matrix molecules have the capacity to induce rapid pulpal wound healing in pulpotomized teeth, and suggest that the longevity and continued presence of enamel matrix macromolecules at the application site can be utilized to stimulate growth and repair of dentin over a period consistent with a favorable clinical outcome.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48011/1/223_2003_Article_153.pd