The surface morphology of human enamel treated with pulsed, infrared laser radiation was examined using reflected light and scanning electron microscopy. Thin ( < 5μm) surface melts with a varying degree of surface macroroughening were produced for each of the four wavelengths studied (9.32, 9.57, 10.27, 10.59 μm) in the 10–50 J·cm^––2 pulse energy density range with peak power densities reaching approximately 10⁷–10⁸ W·cm^––2. Significant heat conductance under the surface melt was limited to a depth of approximately 10–20 μm. Tetracalcium diphosphate monoxide, Ca₄(PO₄)₂O, was identified as being a component of the surface melt together with an apatite phase that had a reduced carbonate content when compared to normal surface enamel. Histological differences and shallower lesions were observed using polarizing light microscopy in artificial lesions formed in lased enamel when compared with control lesions. These results provide a greater understanding of the use of lasers as a potential preventative tool in dentistry.

The structure of the chorion and plasma membranes of gastrula‐stage zebrafish Brachydanio rerio embryos were studied using field emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). These studies confirm the outer chorion membrane complex to be 1.5–2.5 μm in thickness and to consist of three layers, electron‐dense outer and innermost layers (0.2–0.3 and 1.0–1.6 μm in thickness respectively) separated by an electron‐lucent middle layer (0.3–0.6 μm in thickness). The middle and inner layers are pierced by pore canals. A granular to farinaceous nature of the thin outer surface of the outer layer of the chorion has been revealed for the first time. The study provides original TEM images of the plasma membrane structures of gastrula‐stage embryos, and FE‐SEM and TEM images showing the plasma membrane to have three morpohologically distinct regions, being prominently ridged and folded at the surface of the blastoderm, smooth over the syncytial layer at the vegetal pole and with an intermediate region between the animal and vegetal pole where folding develops in advance of the expanding blastodermal disc of cells. FE‐SEM and TEM studies reveal details of the syncytial layer (1–4 μm thick) beneath the smooth plasma membrane at the vegetal pole, containing cytoplasmic organelles and small yolk globules. The significance of the structural detail shown in these studies is considered in the light of the difficulties experienced in cryopreservation of the embryo resulting from the inability of achieving cryoprotectant penetration of the yolk mass.

In this paper the relation between the average lesion depth (1) of artificial carious lesions and the length of microhardness indentations (D) on the surface (the load perpendicular to the surface) is investigated. The results show that an empirical linear relationship does exist between 1 and D for both human and bovine enamel. Linearity has been found for decalcification periods 2–8 days and pH values 4.5 and 4.0. The slope of the curves as well as the load dependency is discussed. The error in the lesion depth determinations is 10–15%. The study also gives a numerical comparison between the average lesion depth in human and in bovine enamel decalcified under the same conditions. After 4 days at pH 4.5 or 4.0, the relations are 1 (bovine) ≈ 1.4 # 1(human) and 1 (bovine) ≈ 1 (human), respectively. The advantage of the technique presented here is that is does not destroy the specimen and is suitable for experiments in in vivo situations.

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Three topical fluoride agents deposited surface coatings of different morphology and thickness on intact human enamel surfaces. The agents studied were an acidic silane fluoride lacquer, a neutral NaF lacquer, and an APF gel. Each agent reacted with the enamel surface differently, producing its own distinctive etching pattern. The smallest particles observed in the surface coatings were from 20 to 30 nm in diameter and appeared to have indistinct morphologies. They often agglomerated into spherical globules ranging from 1-3 micron in diameter.