A scanning electron microscope investigation of calcium fluoride-like material deposited during topical fluoride exposure on sound human enamel in vitro.

1. The morphological aspects of globules deposited in vitro when a NaF solution is applied to sound human enamel were studied by scanning electron microscopy. 2. Particles, presumably of calcium fluoride-like material, formed on the surfaces of an unerupted tooth and consisted of subunits showing a "cauliflower" appearance, indicating agglomeration of even smaller particles. The number and size of the crystals increased with time of exposure. 3. These particles represent highly resistant fluoride reservoirs and may be of clinical significance.