Diurnal periodicity of von Ebner growth lines in pig dentine

Using ground sections from the teeth of young pigs injected at 2-weekly intervals with marker dyes, it was possible to visualize and photograph von Ebner growth lines situated between labelled increments, provided that both the bright field and ultraviolet illuminators of a Leitz Ortholux microscope were used simultaneously. Counts on five sections revealed that 13 von Ebner lines, and therefore 14 increments, existed between two successive fluorescing lines. This confirmed the commonly held belief that von Ebner lines are a visible manifestation of a daily rhythm of dentine deposition. Von Ebner lines are visible in dentine as a result of the refractive Becke effect, indicating an abrupt, though possibly small, change in refractive index at the junctions between adjacent layers of dentine. The most likely explanation of this is a change in the composition of forming dentine during the course of each day.