LIGHT AND SCANNING ELECTRON-MICROSCOPIC I NVESTIGATIONS ON ENAMEL HYPOPLASIAS OF FLUOROSED ROE DEER TEETH

Hypoplastic enamel surface lesions were studied in severely fluorosed permanent mandibular cheek teeth. The shape of the hypoplasias varied between large, rather shallow depressions of the enamel surface and na rrow lesions running deep into the enamel. The areas of transition bet ween hypoplasias and surrounding enamel were of a convexly rounded out line. Studies of thin ground sections through hypoplasias viewed in no rmal and polarized light showed the (crowded) Retzius lines to exactly follow the shape of the hypoplastic surface lesions. As was revealed by scanning electron microscopy, the bottom of the shallow defects as well as the walls of the lesions and the transitional area between hyp oplasias and surrounding surface enamel were covered by Tomes' process pits. Based on the present findings and that of a previous study (KIE RDORF et al. 1993), we interprete these enamel surface hypoplasias to be the result of a more or less intense reduction in the secretory act ivity of the ameloblasts. On the basis of our observations, detachment of the ameloblasts from the forming enamel surface and formation of s ubameloblastic cysts, that were observed in rodents after injection of high doses of fluoride, can be excluded as the way by which formation of the hypoplasias described in this study had occurred.