I have been examining my megalodon teeth and even Ramanessin shark teeth and under the microscope I can usually see (presumably) enamel that had been laid down in thin lines that always turn and meet the tooth edges at a 90 degree angle. It is easiest to see in fossil teeth where the mineral coloring brings out these whitish lines. It is hard to see in extant white teeth. Here are 3 photos of what I mean. The horizontal lines are from the middle region of the meg tooth along the tooth axis. The