An Investigation into Human Enamel Structure by an Optical Sectioning Technique
The inter-relationship of the 4μ diameter rods of which human enamel is composed has previously been deduced from the appearances of cut surfaces of transverse and longitudinal slices of teeth. These can be very misleading as to the true structure. The basis of the present technique was the 3-dimensional reconstruction and analysis of rod inter-relationships from series of optical sections produced by means of a through focussing technique on thick slices of enamel. Slices of enamel about 120μ thick were prepared in such a way that the rods were approximately perpendicular to the cut faces. The slices were observed with a microscope fitted with a fine focus attachment graduated to record changes of 2μ in the height of the microscope stage. Photographs were taken with a Leitz Orthomat photographic apparatus which automatically winds a 35mm film on for each successive photograph. This obviated any interference with the microscope, camera and slice during the filming and led to a stability of relationship between slice and camera which was an important factor when subsequently locating rods between successive prints.