The effect of strontium, cobalt and fluoride on rat incisor enamel formation

Abstract

This investigation examined ultrastructurally the entire period of development of alterations in formative ameloblasts and the enamel which they produce following injection with fluoride, strontium, and cobalt ions. Rats injected with these ions were sacrificed at intervals of 1, 2, 4, 8, 16, 24 and 48 hours to elucidate the sequence and detail of cytologic and cell product alterations which occur. Undecalcified sections of rat incisor teeth were studied using electron microscopy and microradiography. All three ions initially produced disturbances in cell morphology and enamel formation consisting of dark globules, vacuoles, and pooling of stippled material on the enamel surface. While a period of decreased crystal formation occurred after injection with all three ions, only cobalt responses included a period of apparently complete absence of crystal formation. The hypermineralized layers occurring in the altered enamel are attributed to changes in the rate of enamel matrix formation and duration of its exposure to tissue fluids. Morphologic changes in Tomes' process were observed at the time of formation of abnormel following injection of all three ions. These observations are compared with previous studies of altered enamel formation and analyzed with the goal of learning more about the mechanisms of amelogenesis.

The Impact of Fluoride on Ameloblasts and the Mechanisms of Enamel Fluorosis

“…On the basis of these data, some of the older reports of the effects of parenterally applied fluoride on enamel formation in rats show levels that appear to be within the toxic range, and need to be interpreted with caution (Neiman and Eisenmann, 1975;Chen and Eisenmann, 1984;Ashrafi et al, 1988). Indeed, some studies have reported toxic effects after fluoride injection, including a delay in growth (less gain in body weight), immobility, and change of skin color (Mörnstad and Hammarström, 1978), or even death a few hours after injection of fluoride (Larsen et al, 1981).…”

“…In severe cases, prismless enamel is found within prismatic inner enamel. At these locations, formation of prismatic enamel had been abruptly interrupted during fluoride insult, during which prismless enamel had formed; after recovery, the prismatic enamel continued to form (e.g., Neiman and Eisenmann, 1975;Chen and Eisenmann, 1984;Suckling et al, 1988;Monsour et al, 1989;Kierdorf and Kierdorf, 1997;Kierdorf et al, 2000Kierdorf et al, , 2004.…”

Strontium and Caries: A Long and Complicated Relationship

“…Animal studies have shown that Sr causes at least disturbances in ameloblast morphology and amelogenesis [Weinmann, 1943;Neiman and Eisenmann, 1975], whereas several reports exist on Sr-mediated dentin hypomineralisation [e.g. Yaeger and Eisenmann, 1963].…”

“…Similar to its effects on dentin, Sr has been shown to cause disturbances in ameloblast morphology and amelogenesis [Weinmann, 1943;Neiman and Eisenmann, 1975] in rats when 6 injected. White et al [1980] demonstrated that the enamel organ limits Sr uptake in both the secretory and maturation phases of enamel formation.…”

Cytochemical Calcium Distribution in Secretory Ameloblasts of the Rat in Relation to Enamel Mineralization

“…Additional evidence that a substantial pool of calcium is available during the fluoride response is sup ported by the fact that pre-existing enamel continues to mineralize, forming a hypermineralized layer while newly secreted matrix fails to mineralize. This has been con firmed by microradiographic studies [9] as well as organ culture of mineralizing tooth germs exposed to various levels of fluoride [18]. There is growing evidence to sup port the view that fluoride may cause alterations in the composition of newly secreted enamel matrix.…”