Histological Features of Fluorosed Human Dental Enamel

Abstract

The present study describes the histological features of enamel in teeth showing either mild or severe fluorosis. Sections were examined in transmitted and polarized light after imbibition in aqueous media or alcohols and quinoline. For semiquantitative study contour maps were prepared. Furthermore quantitative imbibition studies were performed along a traverse through the enamel and at selected points. From the values of total path difference, birefringence was calculated and imbibition graphs drawn. Finally, contact microradiographs were made. The study showed that it is only possible to correlate the degree of histological change with clinical features in severe cases of dental fluorosis. The general morphology of fluorosed enamel does not differ from normal enamel, but the tissue comprise areas of diffuse hypomineralization. In polarized light, opposite to microradiography, much more extensive changes were observed. Thus, slight degrees of dental fluorosis were recorded only when using polarized light. In severe cases, a maximum degree of 25% porosity or more were recorded and located immediately deep to a well-mineralized enamel surface. In severe cases of fluorosis, only dark zones were observed when examined in quinoline, and the quantitative imbibition studies showed that the enamel in these cases reacted similar to what is described in initial caries lesions. In both slight and severe dental fluorosis the subsurface porous region behaved as a ‘mixed body’ in aqueous media, but when examined in alcohols, these could only penetrate the tissue completely in severe cases. Thus, in mild dental fluorosis the subsurface region behaved as a ‘molecular sieve’. The findings in the present study are correlated to previous observations of enamel formation in order to explain the pathogenesis of dental fluorosis.

Relative fluoride response of caries lesions created in fluorotic and sound teeth studied under remineralizing conditions

“…Then, the teeth were cut in half coronally-apically and mesially-distally 6 leaving buccal and lingual tooth halves from which the roots were removed. As the susceptibility to fluorosis varies between tooth surfaces 13 and to eliminate surface-specific differences in natural fluoride concentration 5 which would have been confounding factors, only the buccal half was used in the present study; the lingual half and all other tooth sections were discarded. Subsequently, a sound enamel window, approx.…”

“…The higher concentration of fluoride is believed to affect cell/matrix interactions as the teeth are forming. 4 Hypomineralization of enamel is caused by the retention of amelogenins in the early maturation stage of tooth development 5 . As a result, the affected enamel does not mature and has surface and subsurface porosities.…”

“…5 To overcome this potentially confounding factor, a sound enamel window was created on the teeth close to the cervical area and through abrasion, thereby standardizing all teeth. It is important to realize, however, that fluorosed teeth have a variation in enamel structure even from section to section, as enamel fluorosis appears clearer in cusps and incisal areas.…”

Análise da morfologia de incisivos fluoróticos de ratos por meio de microscopia eletrônica de varredura e microscopia de polarização

“…Muitos estudos de fluorose examinam as características histológicas e a natureza físico-química do esmalte (Fejerskov et al, 1974(Fejerskov et al, , 1975Shinoda, 1975). No entanto o que concerne a ultraestrutura do esmalte fluorótico, os estudos são escassos (Kruger, 1971: Fejerskov et al, 1974.…”

“…Do ponto de vista estrutural, a fluorose se caracteriza por um esmalte superficial normalmente mineralizado sobreposto a uma camada hipomineralizada (Fejerskov et al, 1974(Fejerskov et al, , 1975 (Fejerskov et al, 1994).…”